Fire hazards calculations pdf. Prediction of dangerous factors of fire during its free development

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LECTURE

in the discipline "Prediction of dangerous fire factors"

Topic No. 3. "GAS EXCHANGE IN THE ROOM AND THERMAL PHYSICAL FUNCTIONS REQUIRED FOR THE DESCRIPTION

CLOSED FIRE"

Lecture outline:

Lecture 1.2. ADDITIONAL EQUATIONS OF AN INTEGRAL MATHEMATICAL MODEL OF FIRE FOR CALCULATING THE FLOWS OF EXHAUST GASES AND AIR ENTERING THROUGH OPENINGS

1.1. Introduction

1.2. Pressure distribution along the height of the room

1.3 Plane of equal pressures and operating modes of the opening

1.4. Distribution of pressure differences along the height of the room

1.5. Formulas for calculating the flow rate of gas emitted through a rectangular opening

1.6. Formulas for calculating the air flow through a rectangular opening

1.7. The influence of wind on gas exchange

Lecture 3.4. EQUATIONS OF AN INTEGRAL FIRE MODEL FOR CALCULATING THE HEAT FLOW IN THE FENCE AND THE BURNING RATE OF COMBUSTIBLE MATERIALS

2.1 Approximate estimate of the amount of heat flow into the fences

2.2 Empirical methods for calculating heat flow into enclosures

2.3 Semi-empirical methods for calculating heat flow into fences

2.4 Methods for calculating the burnout rate of combustible materials and heat release rate

Lecture objectives:

1. Educational

As a result of listening to the material, listeners should know:

Integral equations for calculating gas exchange parameters

Equations of the integral model for determining heat flows to room structures during a fire

The influence of external conditions on heat and gas exchange during a fire

Be able to: predict the situation during a fire, taking into account heat and gas exchange

2. Developmental: highlight the most important thing, independence and flexibility of thinking, development of cognitive thinking.

Literature

1. D.M. Rozhkov Prediction of hazardous factors of indoor fire. – Irkutsk 2007. P.89

2. Yu.A.Koshmarov, M.P. Bashkirtsev Thermodynamics and heat transfer in firefighting. VIPTSH Ministry of Internal Affairs of the USSR, M., 1987

3. Yu.A.Koshmarov Prediction of dangerous factors of fire in the premises. – Moscow 2000. P.118

4. Yu.A.Koshmarov, V.V. Rubtsov, Processes of growth of fire hazards in industrial premises and calculation of the critical duration of a fire. MIPB Ministry of Internal Affairs of Russia, M., 1999

ADDITIONAL INTEGRAL EQUATIONS

MATHEMATICAL MODEL OF FIRE FOR CALCULATION

EXPENSIVE AND INCOMING GAS CONSUMPTIONS

THROUGH AIR OPENINGS

Introduction

During a fire, gas exchange occurs between the room and the environment through openings for various purposes (windows, doors, technological openings, etc.).

The stimulator of gas movement through the openings is the pressure difference, i.e. the difference between the pressure inside a room and the pressure in the surrounding atmosphere. The pressure difference is due to the fact that during a fire, the density of the gas environment inside the room differs significantly from the density of the outside air. In addition, it is necessary to take into account the influence of wind on the magnitude of this difference. The fact is that the external pressure on the windward side of the building is higher than the external pressure on the leeward side. Let's consider conditions when there is no wind.

In the initial stage of a fire, a specific gas exchange regime is observed. The peculiarities of this mode are that the gas exchange process occurs in one direction through all existing openings and cracks. There is no air flow into the room from the environment during this period of fire development. Only after some time, when the average temperature in the room reaches a certain value. The gas exchange process becomes two-way, i.e. Heated gases flow out of the room through some openings, while fresh air enters through others. The duration of the initial stage of the fire, during which “one-way” gas exchange is observed, depends on the size of the openings.

Provided that there is no air supply from the outside in the differential equations of fire, we can discard terms containing air flow ( G B = 0.).

In addition, we will consider unpressurized rooms in which the average pressure of the medium remains almost constant, equal to the pressure of the outside air, so that with sufficient accuracy we can assume that:

Where r 0 , T 0– density and temperature of the environment before the start of a fire; r m, T m– respectively, the average values of density and temperature of the medium at the considered moment in time; Р m– average pressure in the room.

The time interval during which one-way gas exchange is observed is relatively short. The average temperature and oxygen concentration in the room change slightly over this period of time. For this reason, it can be accepted that the values h, D, R at this stage of the fire remain unchanged. In addition, we accept that n 1 = n 2 = n 3 = m = 1 and V = const.

Taking into account the above, the fire equations for its initial stage in a room with a small opening take the following form:

; (2)

, (4)

, (5)

(6)

In what follows, one more assumption is made:

with р = с рВ = const. (7)

In order to obtain an analytical solution to these equations, the following technique is used. Since the process of fire development is considered over a relatively short period of time, we can assume that the ratio of heat flow in the fence to heat release is a constant value, equal to its average value over this interval:

(8)

Where Q om = ψ η Q n;

τ * – time of completion of the initial stage of the fire;

φ – heat loss coefficient.

From the energy balance equation (3) you can determine the flow rate of gases expelled from the room.

Taking into account equations (3) and (8), the flow rate of expelled gases at each moment in time is determined by the formula:

(9)

Therefore, for the initial stage of a fire, taking into account condition (1), the flow rate of expelled gases is determined by the formula:

(10)

Thus, the fire equations for its initial stage in the room will take the form:

, (11)

, (12)

, (13)

. (14)

These equations represent a special case of the basic (unsimplified) system of fire equations.

The dependence of the average volume density on time can be described by the following expression:

, (15)

then the process of increasing the average ambient temperature in the room is described by the formula:

, (16)

Where

where b Г – flame front width, m;

where is the heat of combustion, J kg -1;

with p– heat capacity of the gas environment in the room, J∙kg -1 ·K -1 (1.01);

ρ 0 , T 0 – initial value of density (kg m -3) and temperature (K), respectively;

V– free volume of the room, m3;

From the differential equation (12), which describes the process of reducing the partial oxygen density in a room, we find the partial oxygen density depending on time:

. (17)

Where ρ 0 = 0.27 kg m -3, ρ 01 / ρ 0 = 0,23.

Using differential equation (13), we determine the average partial density of toxic gas depending on time using the formula:

, (18)

Where – threshold density, kg m -3.

Finally, consider the differential equation (14), which describes the change in the critical density of smoke in a room. Let us separate the variables in this equation and then, integrating taking into account the initial condition, we obtain a formula for determining the optical concentration of smoke:

, (19)

Where .

Meaning μ * depends on the properties of the combustible material (CM). For example, for wood when it burns in the open air μ * ≤ 5 Np m -1 .

The optical density of smoke is related to the visibility range by the following relationship:

Where l view– visibility range, m.

3 ORDER OF WORK

1. Using the basic theoretical principles, calculate according to the version of the initial data (Table 3):

a) partial density of oxygen depending on time;

b) average partial density of toxic gas;

c) optical concentration of smoke;

d) optical density of smoke.

2. Enter the obtained intermediate and final results into the table.

3. Prepare a report.

1) Brief theoretical information.

2) Initial data.

3) Quantitative indicators of the calculations made.

4) Answers to security questions.

The work is performed on A4 sheets, in printed text, in the form of an explanatory note containing a brief abstract part, the required calculations and graphs. The design of the work must comply with the general requirements for the design of student work at the university.

Table 3 - Data on options for calculating the initial stage of a fire

Option No.	Room size	t oh oh s	Height of the working area, h, m	Flammable substance	Weight, kg	Shape of the combustion surface (Table 4)	Fire development period, min	Flame front width, m	Burning area F, m 2
	20x10x5		1,7	petrol		V
	15x15x6			acetone		V
	10x30x4		1,8	wood		b
	20x20x4		2,1	polyethylene		b
	40x10x3		1,8	rubber		b
	25x30x5		2,0	turbine oil		V
	30x10x5		1,8	linen		b
	20x20x6		2,5	diesel fuel		V
	40x10x5		2,2	cotton		A
	30x8x4		1,9	cotton		A
	20x10x4		2,3	petrol		V
	20x20x3		1,8	toluene		A
	30x6x3		1,7	wood		A
	30x10x5		2,4	polyethylene		A
	20x10x6		2,0	rubber		A
	25x10x4		1,8	turbine oil		V
	30x10x5		2,2	linen		A
	15x15x4		2,0	diesel fuel		V
	30x10x4		2,3	Styrofoam		A
	30x20x5		2,0	cotton		A
	30x30x4		1,8	petrol		V
	40x10x4		2,0	toluene		A
	25x10x3		2,2	wood		A
	25x25x4		2,0	polyethylene		b
	30x20x3		2,0	rubber		A
	25x25x4		1,8	turbine oil		V
	40x10x5		2,4	linen		A
	20x20x6		2,0	diesel fuel		V
	25x10x4		1,8	Styrofoam		b
	30x20x6		2,2	cotton		A

Table 4 – Shape of combustion surface

Table 5 - Average burnout rate, lower calorific value, smoke-forming ability, specific gas consumption and linear flame propagation speed of substances and materials

Substances and materials	Y F, specific mass burnout rate, x10–3, kg m–2 s–1	Net calorific value, Q, kJ kg –1	Smoke generating ability, Dm, m 2 kg –1	Specific gas consumption, L, kg kg –1	Linear speed of flame propagation, J·10 2 , m/s
Petrol	61,7			0,25	0,45
Acetone	59,6			0,26	0,44
Diesel fuel	42,0				0,4
Turbine oil				0,282	0,5
Toluene					0,388
Wood	39,3			1,15
Rubber	11,2				1,7-2
PVC-9 foam	2,8				0,37
Polyethylene	10,3				0,32
Cotton	2,4			2,3	4,2
Linen	21,3		33,7	1,83

CONTROL QUESTIONS

1. Fire stages and their characteristics.

2. Combustion process and basic conditions.

3. Mass burnout rate and what it depends on.

4. Linear speed of combustion propagation

5. Fire temperature in fences and open spaces

6. Smoke is.

7. Fire development and periods

LITERATURE

1. Koshmarov Yu.A. Predicting indoor fire hazards. Tutorial. AGPS Ministry of Internal Affairs of the Russian Federation, M. - 2000.

2. Application of the field method of mathematical modeling of fires in premises. Guidelines. FGU VNIIPO EMERCOM of Russia, 2003.

3. Puzach S.V. Methods for calculating heat and mass transfer during a fire in a room and their application in solving practical problems of fire and explosion safety. Monograph. - M.: Academy of State Fire Service of the Ministry of Emergency Situations of Russia, 2005. - 336 p.

4. Puzach S.V., Smagin A.V., Lebedchenko O.S., Abakumov E.S. New ideas about calculating the required time for evacuation of people and the effectiveness of using portable filter self-rescuers during fire evacuation. Monograph. - M.: Academy of State Fire Service of the Ministry of Emergency Situations of Russia, 2007. 222 p.

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MINISTRY OF THE RUSSIAN FEDERATION FOR CIVIL DEFENSE, EMERGENCIES AND DISASTER ELIMINATION

Academy of the State Fire Service

COURSE WORK

FOR PREDICTION OF GPP

Topic: Prediction of fire hazards in a public building

Completed by: student student gr. 1111-B Art. Lieutenant ext. sl. Mashaev D.T.

Checked by: Candidate of Legal Sciences, Associate Professor, Colonel of the Internal Service, Lebedchenko O.S.

Moscow 2013

Introduction

1. Initial data

4. Determination of the critical duration of the fire and the time of blocking of escape routes

Bibliography

Introduction

alarm automatic evacuation system

To develop economically optimal and effective fire prevention measures, a scientifically based forecast of the dynamics of fire hazards is required. Forecasting the dynamics of dangerous fire factors is necessary:

When creating and improving alarm systems and automatic fire extinguishing systems;

When developing operational plans for extinguishing fires;

When assessing actual fire resistance limits;

And for many other purposes.

Modern scientific methods for predicting the dynamics of fire hazards are based on mathematical models of fire. A mathematical fire model describes in the most general form changes in the parameters of the environment in a room over time. As well as the condition of the enclosing structures of this room and various elements of technological equipment.

Mathematical models of indoor fire consist of differential equations that reflect the fundamental laws of nature: the law of conservation of mass and the law of conservation of energy.

Mathematical models of indoor fire are divided into three classes: integral, zone and differential. Mathematically, the above three types of fire models are characterized by different levels of complexity. To carry out calculations of fire hazards in the finishing shop of a furniture factory, we select an integral mathematical model of the development of a fire in the premises.

1. Initial data. Brief description of the object

The public building is one-story. The building is constructed of prefabricated reinforced concrete structures and bricks.

Dimensions of the room in plan:

Width = 12 m;

D Lina = 24 m;

Height = 4.2 m;

Plan of a public building in Figure 1.

There are 3 window openings in the external walls of a public building, 1 of which is open. Distance from the floor to the bottom edge of each window opening = 0.8 m. Height of window openings = 1.8 m. Width of closed window openings = 2 m, width of open window opening = 6 m. The glazing of window openings is made of ordinary glass. Glazing is destroyed at an average volumetric gas temperature in the room of 300 °C.

The fire wall has a technological opening 3 m wide and high. In the event of a fire, this opening is open.

In a public building has 2 identical doorways connecting to the outside environment. Its width=1.2 m and height = 2.2 m. In case of fire, the doorways are open.

The floors are concrete, with asphalt covering.

Combustible material is furniture + PVC linoleum (0.9+1) Combustible material is located on the floor. Size of site occupied flammable material: length=11 m, width=5 m. Quantity combustible material is 12 00kg.

Collection of initial data

Geometric characteristics of the object.

The position of the center of the orthogonal coordinate system is selected in the lower left corner of the room on the plan (Fig. p.1). The x-axis is directed along the length of the room, the y-axis along its width, and the z-axis vertically along the height of the room.

Geometric characteristics:

room: length L=24 m; width B=12 m; height H=4.2 m.

doors (number of doors N to =2): height h d1.2 =2.2m; width b d1.2 = 1.2 m; coordinates of the lower left corner of the door: y d1 = 0 m; x d1 = 10 m; y d2 = 12 m; x d2 =4.2m;

open windows (number of open windows N oo =2): height h oo 1.2 =1.8 m; width b oo 1,2 = 2 m; coordinates of one lower corner of the window: x oo 1 = 0 m; y oo 1 = 5 m; x oo 2 = 24 m; y oo 2 = 5 m; z oo 1,2 =0.8m;

closed windows (number of closed windows N zo =1): height h zo1 =1.8 m; width b zo1 =6.0m; coordinates of one lower corner of the window: x zo1 = 8 m; y zo1 =12 m; z zo1 =0.8m; glazing destruction temperature Tcr = 300C;

technological opening (number of openings Npo=1): height h p1 = 3.0 m; width b p1 =3.0m; coordinates of the lower left corner of the opening: y p1 = 18m; x p1 =20.0m.

Properties of combustible load in select according to the typical flammable load base (Appendix 3 (furniture + PVC linoleum (0.9+1) No. 11))

lower heat and combustion Q R n = 14 MJ/kg ;

flame propagation speed V l = 0.015 m/s;

specific burnout rate Sh 0 = 0,0137 kg/(m 2 With );

specific smoke emission D = 53 Np*m 2 /kg;

specific oxygen consumption when burning L o2 = 1,369 kg/kg;

release of carbon monoxide L from = 0.03 kg/kg;

allocation of two To isi carbon L co2 = 1,478 kg/kg;

Other hot load characteristics:

total mass of hot load M?=1200 kg;

open surface length l pn = 11 m;

width of the open surface b pn = 5 m;

height of the open surface from the floor level h pn = 0 m;

Initial boundary conditions.

We set the initial and boundary conditions:

The temperature of the gas environment of the room is T m 0 =20? WITH;

The outside air temperature is T a =20? WITH;

The pressures in the gas environment of the room and the outside air at floor level are equal to P a = 10 5 Pa.

Selection of fire development scenario.

The place of combustion is located in the center of the site occupied by the GM

2. Description of the mathematical model of fire development in the premises

To calculate the dynamics of dangerous fire factors, we use an integral mathematical model of the free development of a fire in a room.

According to the initial data in the basic system of differential equations, it should be assumed that

G pr =0; G out =0; G ov =0; Q 0 =0;

where G in and G out are the flow rates of the supply and exhaust fans;

G ov - consumption of gaseous fire extinguishing agent; Q 0 - heat flow released by the heating system.

For a fire under given conditions, we can assume in the energy equation that

those. the internal energy of the environment in a room during a fire remains practically unchanged

Taking into account the above, the system of basic equations of the IMM has the form

;

where V is the volume of the room, m 3; c m , T m , p m - average volumetric densities, temperatures and pressures, respectively; m m is the average volume concentration of the combustion product; X O 2 - average volume concentration of oxygen.

3. Calculation of the dynamics of fire hazards in the premises

To predict the general physical properties, an integral model was used - a mathematical model of fire, which is implemented by the INTMODEL program, developed at the IT&G Department of the Academy of the State Fire Service of the Ministry of Emergency Situations of Russia. In this program, the Runge-Kutta-Fehlberg method of 4-5 orders of accuracy with a variable step is used to numerically solve a system of differential equations.

Table 3.1 Initial data for calculating the dynamics of fire hazards in the premises

Atmosphere: Pressure, mmHg Temperature, °C


Premises: Length, m Width, m Height, m



Temperature, °C
Number of openings
Coordinates of the first opening:
bottom cut, m.
top cut, m.
width, m.
opening, °C
Coordinates of the second opening:
bottom cut, m.
top cut, m.
width, m.
opening, °C
Coordinates of the third opening:
bottom cut, m.
top cut, m.
width, m.

Type of combustible load: furniture + PVC linoleum (0.9+1)

Width, m.
Quantity, kg.
Heat release, MJ/kg
O 2 consumption, kg/kg
Smoke emission, Np*m 2 /kg
CO release, kg/kg
CO 2 release, kg/kg
Burnout rate, kg/(m 2 hour)
Linear flame speed, mm/s

Table 3.2 Results of calculations of the dynamics of fire hazards in the premises

Time min	Conc. O2 wt.%	Smoke, Np/m	Far view., m.	Conc.CO, wt.%	Concentrated CO2, wt.%	Conc. OM, wt.%

Table 3.3 Results of calculations of the dynamics of fire hazards in the premises

Time min	Density Gas kg/m3	Excess pressure, Pa	PRD height, m	Air flow	Gas leak	Burnout rate, g/s

Table 3.4 Results of calculations of the dynamics of fire hazards in the premises

Horizontal time, min	Conc. RH wt.%	Conc. O2 wt.%	Complete combustion, mass,%	Specific rate vyg., kg/(m2h)	Vyg. weight, kg	Speed vyg., g/s	Area, m2

Table p3.5 Results of calculations of the dynamics of fire hazards in the premises

Time min	Surface temperature, °C	Coef. heat transfer, W/(m2K)	Density heat flow, W/m2	Warm. flow, kW

Note:

1. At f=4.5 min. window glazing is destroyed;

2. At f=5.8 min. the GM area is completely engulfed in fire;

3. At f=30.0 min. complete burnout of the combustible load.

Dependence graphs T m (f), µ m (f), X O 2 (f), X CO 2 (f), X CO (f), S (f), Y* (f), l view (f) are presented in the figure, paragraphs 3.1-p3.8

4. Determination of the critical duration of the fire and the time of blocking of escape routes

Ensuring the safety of people in the event of a possible fire must be given paramount importance.

The fundamental document regulating fire safety in Russia - Federal Law No. 123 "Technical Regulations" defines evacuation as one of the main ways to ensure the safety of people during fires in buildings and structures.

The main criterion for ensuring the safety of people in case of fire * is the time of blocking of evacuation routes f bl. The time for blocking evacuation routes is calculated by calculating the minimum value of the critical fire duration. The critical duration of a fire is the time it takes to reach the maximum permissible fire hazards for humans.

Thus, to calculate the time of blocking evacuation routes, it is necessary to have a method for calculating the critical duration of a fire. The question of the accuracy of the method for calculating the critical duration of a fire is key in solving the problem of ensuring the safe evacuation of people in a fire. Underestimation of fire danger, as well as its overestimation, can lead to large economic and social losses

Let us determine, using the data obtained on the PC on the dynamics of the physical permeability, the time of blocking of evacuation routes t§„ from the workshop premises. To do this, we first find the time for each hazardous factor to reach its critical value.

Fire hazards affecting people and property include:

1) flame and sparks;

2) heat flow;

3) increased ambient temperature;

4) increased concentration of toxic products of combustion and thermal decomposition;

5) reduced oxygen concentration;

6) reduced visibility in smoke.

We accept the critical values of RPP according to (Table 4.1).

Table 4.1

Maximum permissible values of RPP

Thus, the critical temperature value at the level of the working area is 70°C. To determine the time the temperature reaches this value, we calculate what the average volume temperature will be if the temperature at the level of the working zone is critical. The relationship between local and volume-average RPP values along the height of the room has the following form:

(GPP - GPP o) = (GPP m - GPP o)Z, (clause 4.1)

where RPP is the local (maximum permissible) value of RPP; RPP 0 is the initial value of RPP; RPP m - average volume value of the hazardous factor; Z - parameter calculated by the formula:

where H is the height of the room, m; h - level of the working area, m. Height of the working area h is determined by the formula

h = h pl +1.7, (clause 4.3)

where h p l is the height of the platform on which people are located above the floor of the room, m.

People at higher elevations are at greatest risk in a fire. . In our case we take hpl = 0. Then

Parameter value Z at the level of the working area it will be equal to:

Then, when the temperature at the level of the working zone reaches 70°C, the average volume temperature will be equal to:

The average volume temperature reaches this value approximately 2.4 minutes after the start of the fire (table 3.2).

For successful evacuation of people, the visibility range in case of smoke in the room during a fire must be no less than the distance from the most remote workplace to the emergency exit. The visibility range on escape routes must be at least 20 m [2]. The visibility range is related to the optical density of smoke as follows:

l pr =2.38/m(4.4)

Hence, the maximum visibility range at the level of the working area will correspond to the following value of the optical density of smoke:

l pr =0.119 Np/m

In this case, the average volume level of smoke will be equal to:

According to the table in clause 3.2, we obtain f m = 3.8 minutes.

The maximum partial density of oxygen on escape routes is 0.226 kg/m 3 .

When the partial density of O2 reaches this value at the level of the working zone, the average volumetric density of oxygen will be:

To determine the time the oxygen concentration reaches this value, we plot the dependence of the average volumetric oxygen density on the time of the fire (Figure 4.1).

In accordance with Figure 3.9, the time to reach the critical value of the partial oxygen density is 2.3 minutes.

The maximum partial density of carbon monoxide on evacuation routes is 1.16·10 -3 kg/m 3 . When the partial density of CO reaches this value at the level of the working area, the average volumetric density of carbon monoxide will be:

The average volumetric partial density of CO does not reach this value during the calculation (Figure 4.2.).

The limiting value of the partial density of CO 2 at the level of the working area is 0.11 kg/m 3 . In this case, the average volumetric density of carbon dioxide will be equal to:

The partial density of CO 2 does not reach this value during the calculation (Figure 4.3).

The maximum permissible value of heat flow along escape routes is 1400 W/m2. As a first approximation, the value of the heat flux density along evacuation routes can be estimated using the data in table 3.5.

The average heat flux density along evacuation routes reaches its critical value after 2.9 minutes from the start of the fire (Table 3.5).

As we can see, the temperature of the gas environment in the room reaches the critical value the fastest, therefore, φ t = 2.4 min.

Literature

1. Federal Law “Technical Regulations on Fire Safety Requirements”. 2008.

2. Methodology for determining the calculated values of fire risk in buildings, structures and structures of various classes of functional fire hazard. Appendix to the order of the Ministry of Emergency Situations of Russia dated June 30, 2009 No. 382.

3. Methodology for determining the estimated values of fire risk at production facilities. Appendix to the order of the Ministry of Emergency Situations of Russia dated July 10, 2009 No. 404.

4. A manual for determining the fire resistance limits of structures, the limits of fire spread through structures and flammability groups of materials (to SNiP P-2-80). - M., 1985.

5. Fire safety of buildings and structures. SNiP 21-01-97*.

6. Puzach S.V. Methods for calculating heat and mass transfer during a fire in a room and their application in solving practical problems of fire and explosion safety. - M| State Fire Service Academy of the Ministry of Emergency Situations of Russia, 2003.

7. Ryzhov A.M., Khasanov I.R., Karpov A.V. and others. Application of the field method of mathematical modeling of fires in premises. Guidelines. - M.: VNIIPO, 2003.

8. Determination of the time of evacuation of people and the fire resistance of building structures taking into account the parameters of a real fire: Textbook / Puzach S.V., Kazennoe V.M., Gornostaev R.P. - M.: Academy of State Fire Service of the Ministry of Emergency Situations of Russia, 2005. 147 p.

9. Astapenko V.M., Koshmarov Yu.A., Molchadsky I.S., Shevlyakov A.N. Thermogasdynamics of fires in premises. - M.: Stroyizdat, 1986.

10. Mosalkov I.L., Plyusina G.F., Frolov A.Yu. Fire resistance of building structures. - M.: Special equipment, 2001.

11. Koshmarov Yu.A. Forecasting hazardous factors of indoor fire: A tutorial. - M.: Academy of State Fire Service of the Ministry of Internal Affairs of Russia, 2000.

12. Drysdale D. Introduction to fire dynamics. - M., Stroyizdat, 1988.

13. Yakovlev A.I. Calculation of fire resistance of building structures. - M.: Stroyizdat, 1988.

14. Koshmarov Yu.A. Thermal engineering: a textbook for universities. - M.: ICC "Akademkniga", 2006. - 501 e.: ill.

15. Problem book on thermodynamics and heat transfer./ Ed. Koshmarova Yu.A. Part 3 - M.: Academy of State Fire Service of the Ministry of Internal Affairs of the Russian Federation, 2001.

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course work, added 06/22/2011

Determination of the estimated time for evacuation of people in case of fire. Preliminary planning of combat operations by members of voluntary fire-fighting units to extinguish fires using primary fire extinguishing means indoors. Determination of the area of the risk zone.

course work, added 04/12/2017

Concentrations and effects of volatile toxic substances released during a fire. Influence of hazardous factors, specific gas output during combustion. Task and tabular data for calculating evacuation time and the degree of danger of flammable substances in case of fire.

training manual, added 01/27/2012

Features of fires in elevators. Operational and tactical characteristics of the facility (KKZ JSC SK Agroenergo). Characteristics of the building, evacuation routes for people. Fire extinguishing and fire alarm installations. Determination of fire parameters.

test, added 06/19/2012

Calculation of evacuation time from the start of a fire to the blocking of evacuation routes as a result of the spread of dangerous fire factors to them. Determination of potential risk values for workers who are in the building on the site.

Introduction

In modern conditions, the development of economically optimal and effective fire-fighting measures is unthinkable without a scientifically based forecast of the dynamics of fire hazards (FH).

Prediction of general physical fitness is necessary:

· when creating and improving alarm systems and automatic fire extinguishing systems;

· when developing operational firefighting plans (planning the actions of combat units in a fire);

· when assessing actual fire resistance limits;

· for calculating fire risk and many other purposes.

Modern methods for forecasting the physical properties make it possible not only to predict probable fires, but also to model fires that have already occurred for their analysis and assessment of the effect of fire protection devices.

Hazardous fire factors affecting people and material assets (according to the Federal Law of the Russian Federation dated July 22, 2008 No. 123-FZ “Technical Regulations on Fire Safety Requirements”) are:

flames and sparks;

· increased ambient temperature;

· reduced oxygen concentration;

· toxic products of combustion and thermal decomposition;

· reduced visibility in smoke;

·heat flow.

From a scientific point of view, fire hazards are physical concepts and, therefore, each of them is represented quantitatively by a physical quantity.

Modern scientific methods for predicting RPP are based on mathematical models of fire. A mathematical model of fire describes in the most general form the change in the parameters of the state of the environment in a room over time, as well as the parameters of the state of the enclosing structures of this room and various elements of (technological) equipment.

The basic equations that make up the mathematical model of a fire follow from the fundamental laws of nature: the first law of thermodynamics and the law of conservation of mass. These equations reflect and link the entire set of interrelated and interdependent processes inherent in a fire, such as heat release as a result of combustion, smoke release in the flame zone, changes in the optical properties of the gaseous medium, the release and spread of toxic gases, gas exchange of the room with the environment and with adjacent rooms, heat exchange and heating of the enclosing structures, reducing the oxygen concentration in the room.

Methods for predicting RPP are distinguished depending on the type of mathematical model of fire. Mathematical models of indoor fire are conventionally divided into three types: integral, zone and field (differential).

To make a scientifically based forecast, it is necessary to turn to one or another fire model. The choice of model is determined by the goal (objectives) of the forecast (research) for given conditions of uniqueness (characteristics of the room, combustible material, etc.) by solving a system of differential equations that form the basis of the selected mathematical model.

The integrated fire model allows you to obtain information (i.e., it allows you to make a forecast) about the average volumetric values of the parameters of the state of the environment in the room for any moment of the development of the fire. At the same time, in order to compare (correlate) the average (i.e., volume-average) parameters of the environment with their limiting values in the working area, formulas are used that are obtained on the basis of experimental studies of the spatial distribution of temperatures, concentrations of combustion products, optical density of smoke, etc. d.

However, even when using an integral fire model, it is generally impossible to obtain an analytical solution to a system of ordinary differential equations. The implementation of the chosen forecasting method is possible only by solving it numerically using computer modeling.

1. Topic and objectives of the course work

Course work is one of the types of independent educational work of students to master educational material and the final stage of studying methods for predicting general physical properties based on mathematical models of fire, considered in the discipline “Forecasting hazardous factors of fire”, as well as a form of control on the part of the educational institution over the level of relevant knowledge and skills of cadets.

The course work poses the following tasks for students:

· consolidate and deepen knowledge in the field of mathematical modeling of the dynamics of fire hazards;

· using specific examples, obtain information about the degree of interdependence and interconnectedness of all physical processes inherent in a fire (gas exchange of the room with the environment, heat generation in the flame zone and heating of building structures, smoke emission and changes in the optical properties of the gaseous environment, release and spread of toxic gases, etc.);

· master the methodology for predicting general physical properties using a computer program that implements an integral mathematical model of fire;

· gain skills in using computer programs when studying fires.

The topic and purpose of the course work is forecasting the dangerous factors of a fire in a room (the purpose and other characteristics of which are determined by the assignment option).

2. Requirements for the content and design of coursework

The course work is carried out in accordance with the methodological instructions and consists of a calculation and explanatory note and a graphic part. The calculation and explanatory note consists of explanatory text, calculation results in the form of tables, drawings and diagrams reflecting the geometric characteristics of the object and the picture of gas exchange in the room during a fire. The graphic part is presented by graphs of the development of fire hazards in the premises over time.

The necessary reference material is given in the appendices to the instructions and in the recommended literature.

Before starting course work, you must: study the material in the discipline, familiarize yourself with the methodological instructions, select recommended educational, reference and regulatory literature. Answers for each item of the task are given in expanded form with justification.

The work must be done neatly, in black ink or printed in black on A4 printed sheets. The text in the explanatory note should be written legibly, without abbreviations of words (except for generally accepted abbreviations), on one side of the sheet. The computer version of the work is typed in the word processor Word, Times New Roman font with 1-1.5 line spacing. The font size for text is 12 or 14, for formulas - 16, for tables - 10, 12 or 14. The size of the margins on the sheet is 2 cm on all sides. Paragraph indentation of at least 1 cm.

When calculating the required evacuation time, formulas and the values substituted in them, units of measurement of the physical quantities obtained in the answer should be given.

Section and chapter headings are written in capital letters. Subsection headings are in lowercase letters (except for the first capital). Hyphenation of words in headings is not allowed. There is no period at the end of the title. The numbering of tables, figures and graphs should be continuous.

The pages of the course work must be numbered with Arabic numerals. The first page is the title page, the second is the assignment for the course work, the third is the content, etc. There is no number on the first page of the course work. The pages of the course work, except the title page, and the assignments for the course work must be numbered. The assignment form for completing the course work is given in Appendix 1.

The title page must indicate:

name of the ministry, educational institution and department where the course work is being carried out;

the topic of the course work and the assignment option;

FULL NAME. a student who has completed course work;

title, position, full name scientific supervisor;

city and year of course work.

At the end of the work, you must indicate the literature used (the author's surname and initials, the full title of the book, publisher and year of publication). The completed course work must be signed, dated and submitted for review by the correspondence faculty. Having access to defense is the basis for calling a student to a laboratory examination session.

If the work meets the requirements for it, then the manager allows it to be defended. Work recognized as not meeting the requirements is returned to the student for revision.

The defense of coursework by students of the distance learning faculty can be carried out during the session. The results of the defense are assessed on a four-point system: “excellent”, “good”, “satisfactory”, “unsatisfactory”. The project manager puts the assessment on the title page of the work, in the statement, the student’s grade book and certifies it with a signature. Only positive ratings are given.

If a student receives an unsatisfactory grade, he must re-do the work on a new topic or rework the previous one.

3. Selecting a task option and initial data

The assignment option for coursework is determined by the number in the list of the study group (by the number in the group journal). The option number is indicated on the title page of the course work. Depending on the year students entered the training (enrollment 2010, 2011, etc.), the initial data for calculations (ambient and indoor air temperature, dimensions of the room and openings, flammable load parameters, etc.) are given in tables 1-5 (Appendix 2).

Data obtained using computer modeling and necessary to complete Chapter 3 are provided according to options individually in electronic form at the orientation lecture for the discipline.

Additional data for all options:

critical temperature for glazing - 300°C;

number of openings - 2 (windows and door);

anti-smoke mechanical ventilation - absent;

automatic fire extinguishing installation (AUP) - absent;

accept all other not specified parameters as default.

Abbreviations, adopted when presenting the course “Forecasting hazardous fire factors”:

OFP - fire hazards;

PDZ - maximum permissible value of fire hazard;

PPR - plane of equal pressures (neutral plane);

1.In accordance with the assignment option in Chapter 1 of the course work, calculate the initial parameters of the combustible load in the room in question.

2.Draw a plan of the building, indicate on the plan the dimensions of the room and flammable load.

.In Chapter 2, provide a description of the system of differential equations on the basis of which an integral mathematical model of a fire in a room was created, with a full explanation of all the physical quantities included in it.

.In accordance with the assignment option for course work, take from the teacher ready-made tabular data (Table 1) on the dynamics of the development of average volumetric RPP values during the free development of a fire, calculated using the INTMODEL computer program, which implements an integral mathematical model of a fire in a room.

5. Using the tabular data, construct the corresponding graphical dependences of the average volume parameters on the time of fire development: m(t);

µm(t); lview(t); (t); (t); (t); сm(t); Y*(t); Spozh (t); Gв (t); Gg(t); DP(t).

6.Make a description and comparative conclusions based on the obtained graphs, explain the jumps in the graphs (if any).

7.Guided by the data calculated using a computer program and the graphical dependences of the general physical properties on time, in Chapter 4 of the course work, characterize the dynamics of the development of individual general physical properties, the sequence of occurrence of various events, and generally describe the forecast for the development of a fire.

.Determine the critical duration of a fire based on the condition that each fire hazard reaches the maximum permissible (average volume) value and the required time for evacuating people from the premises in question:

a) according to mathematical modeling data (summarize the results in Table 2);

b) according to the methodology for determining the time from the start of a fire to the blocking of evacuation routes as a result of the spread of dangerous fire factors on them in accordance with Appendix No. 5 to the order of the Ministry of Emergency Situations of Russia dated July 10, 2009 No. 404 to paragraph 33 (Methods for determining the estimated values of fire risk at production facilities).

The obtained calculation results are reflected in Chapter 4 of the course work, and conclusions are drawn there: what are the similarities and differences between these methods, what can explain the difference in the calculation results.

9.According to the results of Table 2, draw a conclusion about the timely response of fire detectors installed in the premises. In case of their ineffective work, offer them an alternative replacement (Appendix 3).

10.Carry out calculations of GPP parameters for the level of the working area (GPP l ) with free development of fire at a time of 11 minutes, according to the formula:

(GPP l - General physical training 0) = (GPP m - GPP 0)·Z,

where is the GPP l - local GPP value;

general physical training 0- initial value of the RPP;

general physical training m - volume-average value of the fire hazard factor; - dimensionless parameter calculated by the formula:

At H£ 6 m,

Where h- height of the working area, m;

N- room height, m.

11.The results of GPP calculations for the level of the working area should be included in the table in Chapter 5 of the course work.

12.Based on the calculations obtained for a time of 11 minutes:

a) provide a diagram of gas exchange in the room for a fire development time of 11 minutes with free development of the fire;

b) give a detailed description of the operational situation during a fire according to the physical safety calculations for the level of the working area, propose measures for the safe evacuation of people.

13.Draw a general conclusion on the course work. The output should include:

a) a brief description of the object;

b) analysis of the RPP that reached its maximum permissible value at 11 minutes with free development of the fire;

c) comparison of the critical time for the onset of emergency conditions for dangerous fire factors according to calculations of the INTMODEL computer program and the methodology for determining the time from the start of a fire to the blocking of evacuation routes as a result of the spread of dangerous fire factors to them in accordance with Appendix No. 5 to the order of the Ministry of Emergency Situations of Russia dated July 10, 2009 No. 404;

d) analysis of the timeliness of response of fire detectors installed in the premises, if necessary, proposals for their replacement;

e) description of the actions of facility personnel in the event of a fire, based on the data obtained during the calculations;

f) a description of the actions of fire departments, based on the assumption that the time of their arrival is 10 minutes from the start of the fire;

g) recommendations to the owner of the premises and fire crews to ensure safe evacuation in the event of a fire in the premises. Recommendations should be linked to the results of forecasting the dynamics of general physical fitness for a given room;

h) conclusion about the feasibility and prospects of using computer programs to calculate the dynamics of physical permeability during a fire.

14.At the end of the course work, provide a list of references used.

5. Sample coursework

RUSSIAN EMERGENCY SITUATIONS MINISTRY

Federal State budgetary educational

institution of higher professional education

"Ural Institute of State Fire Service

Ministry of the Russian Federation for Civil Defense Affairs,

emergency situations and disaster relief"

Department of Physics and Heat Transfer

COURSE WORK

Topic: Prediction of fire hazards in a warehouse

Option No. 35

Completed:

student of training group Z-461

Senior Lieutenant of the Internal Service Ivanov I.I.

Checked:

senior lecturer of the department

Physics and Heat Transfer, Ph.D., Captain of Internal Service

Subacheva A.A.

Ekaterinburg

for coursework

in the discipline "Forecasting hazardous fire factors"

Listener Ivanov Ivan Ivanovich

Option No. 35 Well 4 Group Z-461

Object name: cotton bales warehouse

Initial data

Block atmospherepressure, mm. rt. Art. 760 temperature, 0C 20Block room length, m60 height, m6 width, m24 temperature, 0C20 opening 1 - standard (door) bottom cut, m0? width, m3.6 top cut, m3 opening, 0S20opening 2 - standard (windows)? width, m24 bottom cut, m1,2 opening, 0C300 top cut, m2.4 Block loadtype of combustible materialcotton in balessmoke emission Np*m 2/kg0.6 length, m32.9 CO emission, kg/kg0.0052 width, m13.1 CO emission 2, kg/kg0.578number of GN, kg4320specific burnout rate, kg/m 2*с0.0167 heat release MJ/kg 16.7 flame propagation speed, m/s 0.0042 oxygen consumption kg/kg 1.15

Deadline: "____"__________

Listener____________________ Leader_______________

1. Initial data

The fire room is located in a one-story building. The building is constructed of prefabricated reinforced concrete structures and bricks. In the building, along with the warehouse premises, there are two work rooms. Both rooms are separated from the warehouse by a fire wall. The site plan is shown in Figure 1.

(You need to indicate on the diagram the dimensions of the room and the estimated mass of the combustible load according to your option!)

Rice. 1. Building plan

Warehouse dimensions:

length l1 = 60 m;

width l2 = 24 m;

height 2h = 6 m.

There are 10 identical window openings in the outer walls of the warehouse. The distance from the floor to the lower edge of each window opening is YH = 1.2 m. The distance from the floor to the upper edge of the opening is YB = 2.4 m. The total width of the window openings = 24 m. The glazing of the window openings is made of ordinary glass. Glazing is destroyed at an average volumetric gas temperature in the room of 300°C.

The warehouse premises are separated from the work rooms by fire doors, the width and height of which are 3 m. In the event of a fire, these openings are closed. The warehouse premises have one doorway connecting it to the outside environment. The width of the opening is 3.6 m. The distance from the floor to the upper edge of the doorway is Yв = 3, Yн = 0. In case of fire, this doorway is open, i.e. opening temperature 20 0C.

The floors are concrete, with asphalt covering.

Combustible material represents cotton in bales. Fraction of area occupied by flammable load (FL) = 30%.

The floor area occupied by the GN is determined by the formula:

Where? floor area.

The amount of combustible material per 1 P0 = 10. The total mass of combustible material.

Combustion begins in the center of the rectangular area occupied by the GM. Dimensions of this site:

The properties of GN are characterized by the following values:

calorific value Q = 16.7;

carbon monoxide release = 0.0052.

There is no mechanical ventilation in the premises. Natural ventilation is carried out through door and window openings.

Central water heating.

External atmospheric conditions:

no wind, outside temperature 20 0C = 293 K

pressure (at level Y=h) P A = 760 mm. rt. Art., i.e. = 101300 Pa.

Parameters of the state of the gas environment indoors before a fire:

T = 293 K (according to the selected option);

P = 101300 Pa;

Other options:

critical temperature for glazing? 300 o WITH;

material of enclosing structures - reinforced concrete and brick;

room temperature - 20 o WITH;

automatic fire extinguishing system? absent;

anti-smoke mechanical ventilation? absent.

2. Description of the integral mathematical model of the free development of fire in a warehouse

An integral mathematical model of indoor fire was developed based on the fire equations set out in the works. These equations follow from the basic laws of physics: the law of conservation of matter and the first law of thermodynamics for an open system and include:

equation of material balance of the gaseous environment in the room:

V(dсm/dф) = GB + w - Gr, (1)

where V is the volume of the room, m 3; With m - average volumetric density of the gas medium kg/m 3; f - time, s; G B and G r - mass flow rates of air entering the room and gases leaving the room, kg/s; w is the mass burnout rate of the combustible load, kg/s;

oxygen balance equation:

Vd(p 1)/dф = x 1c G B -x 1n 1G r - w L 1Yu, (2)

where x 1- average volumetric mass concentration of oxygen in the room; X 1c - oxygen concentration in exhaust gases; n 1- coefficient taking into account the difference in oxygen concentration in the exhaust gases x 1g 1, n 1 = x 1g /x 1; L 1- rate of oxygen consumption during combustion, p 1- partial density of oxygen in the room;

combustion product balance equation:

Vd(p2)/dф = w L2Yu - x2n2Gr, (3)

where X i - average volume concentration of the i-th combustion product; L i - rate of release of the i-th combustion product (CO, CO2); n i - coefficient taking into account the difference in the concentration of the i-th product in the exhaust gases x ig from the volume average value x i , n i = x ig /X i ; R 2- partial density of combustion products in the room;

Balance equation for the optical amount of smoke in a room:

Vd ()/d = Dш - n4 Gr/ рm - кcSw, (4)

where is the volume-average optical density of smoke; D - smoke-forming ability of GM; n4 is a coefficient that takes into account the difference between the smoke concentration in the heated gases leaving the room and the volume-average optical smoke concentration, n4= mg/mm;

energy balance equation U:

dU/dф = h Q p n w + i G w + S ditch T V G V - WITH R T m m Gr -Q w , (5)

where P m - average volume pressure in the room, Pa; WITH pm , T m - average volumetric values of isobaric heat capacity and room temperature; Qpn- lower working heat of combustion GN, J/kg; WITH ditch , T V - isobaric heat capacity and temperature of incoming air, K; i G - enthalpy of gasification of combustion products of GN, J/kg; m is a coefficient that takes into account the difference between temperature T and isobaric heat capacity C rg flue gases from the average volume temperature T m and volume-average isobaric heat capacity Cpm ,

m = C rg T G /Срm T m ;

Yu - coefficient of completeness of combustion of GN; Q w - heat flow into the fence, W.

Average volume temperature T m is related to the average volume pressure P m and density p m equation of the state of the gas environment in the room:

P m = c m R m Tm .(6)

The equation of the material balance of a fire, taking into account the operation of the supply and exhaust mechanical ventilation system, as well as taking into account the operation of the volumetric fire extinguishing system with inert gas, will take the following form:

VdP m / df = w + G B -G r +G etc -G vyt + G ov, (7)

The above system of equations is solved numerically using a computer program. An example is the INTMODEL program.

. Calculation of the dynamics of general physical transfer using the computer program INTMODEL

Computer simulation results

The educational computer program INTMODEL implements the mathematical model of fire described above and is designed to calculate the dynamics of fire development of liquid and solid combustible substances and materials in a room. The program allows you to take into account the opening of openings, the operation of mechanical ventilation systems and volumetric fire extinguishing with inert gas, and also takes into account the oxygen balance of the fire, allows you to calculate the concentration of carbon oxides CO and CO 2, smoke content of the room and visibility range in it.

Table 1. Dynamics of development of parameters of the gaseous environment in the room and coordinates of the PRD

Time, minTemperature tm, 0СOptical smoke density µm, Np/m Visibility range lm, m,

wt.% , wt.%s m, kg/m 3Neutral plane - PDP Y*, mG V , kg/sG G , kg/sDP, PaS pl , m 2020064,6223001,20531,50,0080,00800120064,6222,999001,2051,150,160,3290,010,2221064,6222,99400,0031,20261,040,411,0650,050,8322064,6222,9800,0091,19620,960,6762,0720,181,8425064,6222,95100,0221,18410,910,9493,2480,433,19530064,6222,90300,0451,16580,891,2374,490,824,99636064,6222,8290,0010,0781,14120,871,5485,7021,347,18745064,6222,7240,0010,1271,11090,881,896,8111,979,78855064,6222,580,0020,1921,0760,892,267,7722,6812,77967064,6222,3910,0030,2791,03850,912,658,5563,4216,171081064,6222,1490,0040,390,99760,912,9319,3914,2719,9711970,00164,6221,8450,0050,530,95410,913,2610,0515,1524,17 121150,00164,6221,4710,0060,7020,90950,933,63110,5276,0128,78131350,00164,6221,0190,0080,9110,86550,954,03610,8256,8333,81141560,00164,6220,4830,011,1610,82350,984,46610,9677,5739,25151770,00164,6219,8620,0131,4550,78461,014,91510,9778,2245,11161980,00264,6219,1580,0161,7950,74991,045,37210,8828,7451,41172180,00364,6218,3820,022,180,72021,085,83710,7019,1458,14182350,00464,6217,5540,0232,6080,69591,126,29810,4639,4165,29192480,00664,6216,7020,0283,0750,67741,166,73710,1969,5572,87202580,00964,6215,8590,0323,5710,66481,197,1469,9169,5980,83212640,01364,6215,0580,0374,0880,65771,237,5059,6479,5389,13222660,01864,6214,3270,0414,6120,65531,267,7979,4089,4197,71232650,02564,6213,680,0465,1340,65681,288,0289,1989,25106,5242610,03364,6213,1210,0515,6450,66121,38,1299,0789,1115,41252560,04257,0812,6480,0556,1380,66761,38,089,0698,99124,38262500,05146,7512,2510,0596,6110,67481,338,3348,7958,7133,33272450,0639,4711,9180,0647,060,68241,439,2347,9978,05141,51282430,0734,0111,5990,0687,5260,68492,0716,033,6534,76149,08292410,0829,7911,3370,0727,9760,68742,116,3183,4874,59156,38302370,0926,5811,1320,0758,390,69252,0315,4353,8924,9163,28312320,09924,1410,970,0798,7650,69991,8513,3834,9785,69169,74322250,10722,310,8480,0829,0950,70921,5410,0637,1147,1175,72332190,11420,9210,7580,0849,3840,71851,358,1848,5217,87181,31342140,1219,8610,6750,0879,6540,72591,37,6418,9198,01186,62352100,12519,0210,5950,0899,9120,73141,287,4549,0297,99191,74362070,1318,3110,5190,09110,1570,73581,287,3819,0497,94196,69372050,13417,7110,4480,09310,3920,73941,277,3319,0577,89201,5382030,13817,210,3840,09510,6150,74241,277,2859,0667,85206,18392010,14216,7510,3240,09710,8270,7451,277,2449,0757,82210,76402000,14616,3510,2690,09911,030,74731,277,2079,0847,79215,24411980,14915,9910,2190,10111,2230,74921,267,1749,0927,76219,62421970,15215,6810,1720,10311,4080,7511,267,1449,17,74223,92431960,15515,3910,1280,10411,5840,75261,267,1179,1087,72228,14441960,15715,1310,0880,10611,7530,7541,267,0929,1157,71232,3451950,1614,8910,0490,10711,9140,75521,267,079,1217,69236,38461940,16214,6810,0130,10912,0690,75631,267,059,1277,68240,4471930,16414,489,9790,1112,2170,75731,267,0319,1337,67244,36481890,16614,3510,0550,1112,2490,76531,448,5737,6846,73248,07491740,16314,5710,4160,10811,9570,78951,579,4396,6955,85250,96501570,15715,210,9260,10311,4720,82081,659,8145,9975,09253,06511400,14716,211,5050,09810,8920,85581,729,9275,4134,4254,53521230,13617,5212,1040,09310,2830,89291,779,8384,8973,77255,54531060,12419,1312,6920,0879,6890,93081,819,5584,4453,2256,2254920,11321,0113,2440,0829,1370,96811,849,0994,0612,69256,6655790,10323,1513,7460,0788,6421,00351,868,4953,742,26256,9556680,09325,5514,1910,0748,2081,0361,867,7953,471,89257,1457590,08428,2114,5780,077,8351,06471,836,9213,3411,62257,2557,5550,0829,7514,7590,0697,6621,07771,816,5173,2621,49257,3

Change in average volumetric parameters of the gas environment over time

Rice. 2. Change in the average volumetric temperature of the gas medium over time

Chart description:The increase in temperature in the first 22 minutes of the fire can be explained by combustion in the PRN mode, which is due to the sufficient oxygen content in the room. From the 23rd minute, the fire goes into the emergency mode due to a significant decrease in oxygen concentration. From 23 minutes to 50 minutes, the combustion intensity constantly decreases, despite the continuing increase in the combustion area. Starting from the 50th minute, the fire again goes into the PRN mode, which is associated with an increase in oxygen concentration as a result of burnout of the combustible load.

Conclusions according to the schedule:On the temperature graph we can roughly distinguish 3 stages of fire development. The first stage is the temperature increase (up to approximately 22 minutes), the second is the quasi-stationary stage (from 23 minutes to 50 minutes), and the third is the decay stage (from 50 minutes until the complete burnout of the combustible load).

Rice. 3. Change in optical density of smoke over time

Chart description:In the initial stage of a fire, smoke is released insignificantly, combustion completeness is maximum. Basically, smoke begins to be released after 22 minutes from the start of the fire, and the maximum permissible limit for the average volumetric value of smoke density will be exceeded at approximately 34 minutes. Starting from 52 minutes, with the transition to fading mode, the smoke decreases.

Conclusions according to the schedule:The emission of significant amounts of smoke began only with the transition of the fire to the fire control mode. The risk of reduced visibility in smoke in this room is small - the maximum permissible limit will be exceeded approximately only after 34 minutes from the start of the fire, which can also be explained by the presence of large open openings in the room (doors).

Rice. 4. Change in visibility range indoors over time

Chart description:During the 26 minutes of fire development, the visibility range in the burning room remains satisfactory. With the transition to the PRV mode, visibility in a burning room quickly deteriorates.

Conclusions according to the schedule: The visibility range is related to the optical density of the smoke ratio. That is, the visibility range is inversely proportional to the optical density of the smoke, so as smoke increases, the visibility range decreases and vice versa.

Rice. 5. Change in average volume oxygen concentration over time

Chart description: In the first 9 minutes of fire development (initial stage), the average volume concentration of oxygen remains almost unchanged, i.e. oxygen consumption by the flame is low, which can be explained by the small size of the combustion center at this time. As the combustion area increases, the oxygen content in the room decreases. From approximately 25 minutes from the start of combustion, the oxygen content stabilizes at the level of 10-12 wt.% and remains almost unchanged until approximately the 49th minute of the fire. Thus, from the 25th to the 49th minute, the PRV mode is implemented in the room, i.e. combustion in conditions of lack of oxygen. Starting from the 50th minute, the oxygen content increases, which corresponds to the decay stage, in which the incoming air gradually fills the room again.

Conclusions according to the schedule: The oxygen concentration graph, similar to the temperature graph, allows us to identify moments of change in combustion modes and stages. The moment when the maximum permissible limit for oxygen is exceeded cannot be tracked on this graph; to do this, you will need to recalculate the mass fraction of oxygen into its partial density using the value of the average volume density of the gas and the formula .

Rice. 6. Change in the average volume concentration of CO during the development of a fire

Chart description: draw a description and conclusions from the graphs similar to those above.

Conclusions according to the schedule:

Rice. 7. Change in average volume concentration of CO2 over time

Chart description:

Conclusions according to the schedule:

Rice. 8. Change in the average volumetric density of the gaseous medium over time

Chart description:

Conclusions according to the schedule:

Rice. 9. Change in the position of the plane of equal pressure over time

Chart description:

Conclusions according to the schedule:

Rice. 10. Change in the flow of fresh air into the room depending on the time of fire development

Chart description:

Conclusions according to the schedule:

Rice. 11. Change in the outflow of heated gases from the room depending on the time of fire development

Chart description:

Conclusions according to the schedule:

Rice. 12. Change in pressure difference over time

Chart description:

Conclusions according to the schedule:

Rice. 13. Change in combustion area during a fire over time

Chart description:

Conclusions according to the schedule:

Description of the fire situation at 11 minutes

According to paragraph 1 of Art. 76 FZ-123 “Technical Regulations on Fire Safety Requirements”, the time of arrival of the first fire department to the place of call in urban settlements and urban districts should not exceed 10 minutes. Thus, the description of the fire situation is carried out at 11 minutes from the start of the fire.

At the initial moments of time, with the free development of a fire, the parameters of the gas environment in the room reach the following values:

The temperature reaches 97°C (crosses the threshold value of 70°C);

The visibility range has remained virtually unchanged and is 64.62 m, i.e. has not yet crossed the 20 m threshold;

The partial density of gases is:

c = 0.208 kg/m3, which is less than the maximum partial density for oxygen;

c = 0.005 kg/m3, which is less than the maximum partial density for carbon dioxide;

c = 0.4*10-4 kg/m3, which is less than the maximum partial density for carbon monoxide;

The PRD will be at the level of 0.91 m;

the combustion area will be 24.17 m2 .

Thus, calculations showed that at the 11th minute of free fire development, the following RPPs will reach their maximum permissible value: average volumetric temperature of the gas medium (at 10 minutes).

. Time to reach threshold and critical values of physical permeability

According to Federal Law-123 “Technical Regulations on Fire Safety Requirements”, the required evacuation time is considered to be the minimum time for one of the fire hazards to reach its critical value.

Required time to evacuate the premises according to mathematical modeling

Table 2. Time to reach threshold values

No. Threshold values Time to reach, min1 Limit gas temperature t = 70°C102 Critical visibility range 1 cr = 20 m333 Maximum permissible partial density of oxygen with = 0.226 kg/m 3104Maximum permissible partial density of carbon dioxide (with )before = (with )before = 0.11 kg/m 3not achieved5 Maximum permissible partial density of carbon monoxide (with )before = (with )before = 1,16*10 -3kg/m 3not achieved6Maximum average volumetric temperature of the gas medium T m = 237 + 273 = 510 K307Critical temperature for glazing t = 300°C is not achieved8Threshold temperature for heat detectors IP-101-1A tpopor = 70°C9

In this case, the minimum time for evacuation from the warehouse is the time to reach the maximum temperature of the gas environment, equal to 10 minutes.

Conclusion:

a) characterize the dynamics of the development of individual OFPs, the sequence of occurrence of various events and, in general, describe the forecast for the development of a fire;

b) draw a conclusion about the timely response of fire detectors installed in the premises (see paragraph 8, table 2). In case of ineffective operation of fire detectors, offer them an alternative (Appendix 3).

Determining the time from the start of a fire to blocking
escape routes due to fire hazards Let's calculate the required evacuation time for a room with dimensions 60·24·6, the fire load of which is baled cotton. The initial room temperature is 20°C.

Initial data:

room

free volume

dimensionless parameter

temperature t0 = 20 0С;

type of combustible material - cotton in bales - TGM, n=3;

calorific value Q = 16.7;

specific burnout rate = 0.0167;

speed of flame propagation over the surface of the GM;

smoke generating ability D = 0.6;

oxygen consumption = 1.15;

carbon dioxide emission = 0.578;

carbon monoxide release = 0.0052 ;

GM combustion completeness;

other parameters

reflection coefficient b = 0.3;

initial illumination E = 50 Lux;

specific isobaric heat capacity Ср = 1.003?10 -3 MJ/kg?K;

maximum visibility range = 20 m;

limit values for toxic gas concentrations:

0.11 kg/m3;

1.16?10-3 kg/m3;

Calculation of auxiliary parameters

A = 1.05?? = 1.05?0.0167? (0.0042)2 = 3.093?10-7 kg/s3

В = 353?Ср?V/(1-)??Q = 353?1.003?10-3?6912/(1-0.6)?0.97?16.7 = 377.6 kg

B/A = 377.69/3.093?10-7 = 1.22?109 c3

Calculation of the time of onset of the PDZ of general physical fitness:

1)at elevated temperature:

2)for loss of visibility:

3)according to reduced oxygen content:

4)for carbon dioxide CO2

a negative number is obtained under the logarithm sign, so this factor does not pose a danger.

5)for carbon monoxide CO

a negative number is obtained under the logarithm sign, so this factor does not pose a danger.

Critical fire duration:

tcr= miníý = í746; 772; ý = 746 s.

The critical duration of a fire is determined by the time at which the maximum permissible temperature in the room occurs.

Required time to evacuate people from the warehouse:

tnv = 0.8*tcr/60 = 0.8*746/60 = 9.94 min.

Make a conclusion about the adequacy/inadequacy of time for evacuation based on the calculation data.

Conclusion: compare the required evacuation times obtained by different methods and, if necessary, explain differences in results.

. Calculation of the dynamics of physical permeability for the level of the working area. Analysis of the fire situation at 11 minutes

The level of the working area according to GOST 12.1.004-91 “Fire safety. General requirements" is taken to be 1.7 meters.

The relationship between local and volume-average RPP values along the height of the room has the following form:

(GPP? GPP) = (GPP? GPP)·Z,

where is the general physical training? local (threshold) GPP value;

OFPO? initial GPP value;

General physical training? average volume value of a hazardous factor;

Z? dimensionless parameter calculated using the formula (see paragraph 4.2).

Table 3. Dynamics of development of general physical fitness at the level of the work area

Time, minTm, оС, mass%,

Np/m , m , mass% , mass% , kg/m 3, m120.023.0000.0000064.620.000000.000001.205171.353220.422.9970.0000064.620.000000.001261.204161.306320.822.9920.000006 4.620.000000.003791.201471.273422 ,122,9790,0000064,620,000000,009271,196371,251524,222,9590,0000064,620,000000,018961,188661,243626,722,9280,0000064,620,0 00420,032861,178301,235730,522 ,8840,0000064,620,000420,053501,165531,239834,722,8230,0000064,620,000840,080891,150831,243939,822,7430,0000064,620,00126 0.117541.135031.2511045.722.6410 ,0000064,620,001690,164301,117801,251 1152,422,5130,0004264,620,002110,223281,099481,251 1260,022,3560,0004264,620,002530,295741,080691,260

The fire area is 24.17 m.

The temperature at the level of the working area is 52.4 0C, which does not reach the maximum value of 70 0 WITH.

The visibility range indoors has not changed and is

2.38/0.00042 = 5666 m.

Normal oxygen concentration: 22.513 wt%.

The partial densities of O2, CO and CO2 at the level of the working area are equal, respectively:

1.09948?22.513/100 = 0.247 kg/m3;

1.09948?0.00211/100 = 2.3*10-5 kg/m3;

1.09948?0.22328/100 = 0.00245 kg/m3.

Thus, calculations showed that the partial density of oxygen is above the maximum permissible limit, and that of toxic gases is below.

Rice. 14. Scheme of gas exchange in a room at time 11 minutes

At the 11th minute of combustion, gas exchange occurs with the following indicators: the influx of cold air is 3.26 kg/s, and the outflow of heated gases from the room is 10.051 kg/s.

In the upper part of the doorway there is an outflow of smoky heated gases from the room; the plane of equal pressure is at a level of 1.251 m, which is below the level of the working area.

Conclusion: based on the calculation results, give a detailed description of the operational situation at the time of the arrival of fire departments, propose measures for the safe evacuation of people.

General conclusion about the work

Draw a general conclusion about the work, including:

a) a brief description of the object;

b) general characteristics of the dynamics of the RPP during the free development of a fire;

d) analysis of the response of fire detectors installed in the premises, if necessary, proposals for their replacement;

e) characteristics of the operational situation at the time of arrival of fire departments, proposals for safe evacuation of people;

f) conclusion on the feasibility and prospects of using computer programs to calculate the dynamics of physical properties during a fire.

Literature

1. Terentyev D.I. Prediction of fire hazards. Course of lectures / D.I. Terentyev, A.A. Subacheva, N.A. Tretyakova, N.M. Barbin // Federal State Budgetary Educational Institution of Higher Professional Education "Ural Institute of State Fire Service of the Ministry of Emergency Situations of Russia". - Ekaterinburg, 2012. - 182 p.

2.Koshmarov Yu.A. Forecasting general physical fitness indoors: Textbook / Yu.A. Nightmarov/ - M.: Academy of State Fire Service of the Ministry of Internal Affairs of Russia, 2000. -118 p.

Federal Law of the Russian Federation dated July 22, 2008 No. 123-FZ “Technical Regulations on Fire Safety Requirements.”

Order of the Ministry of Emergency Situations of the Russian Federation dated July 10, 2009 No. 404 (as amended on December 14, 2010) “On approval of the methodology for determining the estimated values of fire risk at production facilities.” - Fire and explosion safety. - No. 8. - 2009. - Page 7-12.

Order of the Ministry of Emergency Situations of the Russian Federation dated June 30, 2009 No. 382 (as amended on April 11, 2011) “On approval of the methodology for determining the estimated values of fire risk in buildings, structures and structures of various classes of functional fire hazard.” - Fire safety No. 3. - 2009. - Page 7-13.

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RUSSIAN EMERGENCY SITUATIONS MINISTRY

Federal State budgetary educational

institution of higher professional education

"Ural Institute of State Fire Service

Ministry of the Russian Federation for Civil Defense Affairs,

emergency situations and disaster relief"

Department of Physics and Heat Transfer

COURSE WORK

Topic: Prediction of fire hazards in a warehouse

Option No. 35

Completed:

student of training group Z-461

Senior Lieutenant of the Internal Service Ivanov I.I.

Checked:

senior lecturer of the department

Physics and Heat Transfer, Ph.D., Captain of Internal Service

Subacheva A.A.

Ekaterinburg

for coursework

in the discipline "Forecasting hazardous fire factors"

Listener Ivanov Ivan Ivanovich

Option No. 35 Well 4 Group Z-461

Object name: cotton bales warehouse

Initial data

Block atmosphere
pressure, mm. rt. Art.		temperature, 0 C
Block room
		height, m
width, m		temperature, 0 C
opening 1 - standard (door)
bottom cut, m		Width, m
top cut, m		opening, 0 C
opening 2 - standard (windows)
Width, m		bottom cut, m
opening, 0 C		top cut, m
type of combustible material	cotton bales	smoke emission Np*m 2 /kg
		CO release, kg/kg
width, m		CO 2 release, kg/kg
quantity of GN, kg		specific burnout rate, kg/m 2 *s
heat release MJ/kg		flame propagation speed, m/s
oxygen consumption kg/kg

Deadline: "____"__________

Listener____________________ Leader_______________

1. Initial data

(You need to indicate on the diagram the dimensions of the room and the estimated mass of the combustible load according to your option!)

Rice. 1. Building plan

Warehouse dimensions:

length l 1 = 60 m;

width l 2 = 24 m;

height 2h = 6 m.

There are 10 identical window openings in the outer walls of the warehouse. The distance from the floor to the lower edge of each window opening is Y H = 1.2 m. The distance from the floor to the upper edge of the opening is Y B = 2.4 m. The total width of the window openings = 24 m. The glazing of the window openings is made of ordinary glass. Glazing is destroyed at an average volumetric gas temperature in the room of 300°C.

The warehouse premises are separated from the work rooms by fire doors, the width and height of which are 3 m. In the event of a fire, these openings are closed. The warehouse premises have one doorway connecting it to the outside environment. The width of the opening is 3.6 m. The distance from the floor to the upper edge of the doorway is Y in = 3, Y n = 0. In case of fire, this doorway is open, i.e. opening temperature 20 0 C.

The floors are concrete, with asphalt covering.

Combustible material represents cotton in bales. Fraction of area occupied by flammable load (FL) = 30%.

The floor area occupied by the GN is determined by the formula:

Where? floor area.

The amount of combustible material per 1 P 0 = 10. The total mass of combustible material.

Combustion begins in the center of the rectangular area occupied by the GM. Dimensions of this site:

The properties of GN are characterized by the following values:

calorific value Q = 16.7;

carbon monoxide release = 0.0052.

There is no mechanical ventilation in the premises. Natural ventilation is carried out through door and window openings.

Central water heating.

External atmospheric conditions:

no wind, outside temperature 20 0 C = 293 K

pressure (at level Y=h) P a = 760 mm. rt. Art., i.e. = 101300 Pa.

Parameters of the state of the gas environment indoors before a fire:

T = 293 K (according to the selected option);

P = 101300 Pa;

Other options:

critical temperature for glazing? 300 o C;

material of enclosing structures - reinforced concrete and brick;

room temperature - 20 o C;

automatic fire extinguishing system? absent;

anti-smoke mechanical ventilation? absent.

2. Description of the integral mathematical model of the free development of fire in a warehouse

equation of material balance of the gaseous environment in the room:

V(dс m /dф) = G B + w - G r , (1)

where V is the volume of the room, m 3; c m is the average volumetric density of the gas medium kg/m 3 ; f - time, s; G B and G r - mass flow rates of air entering the room and gases leaving the room, kg/s; w is the mass burnout rate of the combustible load, kg/s;

oxygen balance equation:

Vd(p 1)/dф = x 1в G B - x 1 n 1 G r - w L 1 Yu, (2)

where x 1 is the average volumetric mass concentration of oxygen in the room; x 1b - oxygen concentration in exhaust gases; n 1 - coefficient taking into account the difference in oxygen concentration in the exhaust gases x 1g from the average volume value x 1, n 1 = x 1g / x 1; L 1 - rate of oxygen consumption during combustion, p 1 - partial density of oxygen in the room;

combustion product balance equation:

Vd(p 2)/dф = w L 2 Yu - x 2 n 2 G r, (3)

where X i is the average volume concentration of the i-th combustion product; L i - release rate of the i-th combustion product (CO, CO2); n i - coefficient taking into account the difference between the concentration of the i-th product in the exhaust gases x iг from the average volume value x i, n i = x iг /х i; p 2 - partial density of combustion products in the room;

Balance equation for the optical amount of smoke in a room:

Vd ()/d = Dsh - n 4 G r / r m - k c S w , (4)

where is the volume-average optical density of smoke; D - smoke-forming ability of GM; n 4 - coefficient that takes into account the difference between the smoke concentration in the heated gases leaving the room from the average volumetric optical smoke concentration, n4 = m mg / m m;

energy balance equation U:

dU/dф = Q p n w + i g w + C rv T in G in - C r T m m G r - Q w , (5)

where P m is the average volume pressure in the room, Pa; Срm, Тm - average volumetric values of isobaric heat capacity and room temperature; Q p n - lower working heat of combustion GN, J/kg; Срв, Тв - isobaric heat capacity and temperature of incoming air, K; i g - enthalpy of gasification of combustion products of GN, J/kg; m is a coefficient that takes into account the difference between the temperature T and the isobaric heat capacity C rg of the flue gases from the average volume temperature T m and the average volume isobaric heat capacity C pm ,

m = Срг Тг/Срм Т m;

Yu - coefficient of completeness of combustion of GN; Q w - heat flow into the fence, W.

The average volume temperature T m is related to the average volume pressure P m and density p m by the equation of state of the gaseous environment in the room:

P m = c m R m T m . (6)

VdP m / dф = w + G B - G r + G pr - G out + G out, (7)

The above system of equations is solved numerically using a computer program. An example is the INTMODEL program.

3. Calculation of the dynamics of general physical transfer using the INTMODEL computer program

Computer simulation results

The educational computer program INTMODEL implements the mathematical model of fire described above and is designed to calculate the dynamics of fire development of liquid and solid combustible substances and materials in a room. The program allows you to take into account the opening of openings, the operation of mechanical ventilation systems and volumetric fire extinguishing with inert gas, and also takes into account the oxygen balance of the fire, allows you to calculate the concentration of carbon oxides CO and CO 2, the smoke content of the room and the visibility range in it.

Table 1. Dynamics of development of parameters of the gaseous environment in the room and coordinates of the PRD

Time, min

Temperature

Smoke optical density

Visibility range

Neutral plane - PRD Y*, m

Change in average volumetric parameters of the gas environment over time

Rice. 2.

Chart description: The increase in temperature in the first 22 minutes of the fire can be explained by combustion in the PRN mode, which is due to the sufficient oxygen content in the room. From the 23rd minute, the fire goes into the emergency mode due to a significant decrease in oxygen concentration. From 23 minutes to 50 minutes, the combustion intensity constantly decreases, despite the continuing increase in the combustion area. Starting from the 50th minute, the fire again goes into the PRN mode, which is associated with an increase in oxygen concentration as a result of burnout of the combustible load.

Conclusions according to the schedule: On the temperature graph we can roughly distinguish 3 stages of fire development. The first stage is the temperature increase (up to approximately 22 minutes), the second is the quasi-stationary stage (from 23 minutes to 50 minutes), and the third is the decay stage (from 50 minutes until the complete burnout of the combustible load).

Rice. 3.

Chart description: In the initial stage of a fire, smoke is released insignificantly, combustion completeness is maximum. Basically, smoke begins to be released after 22 minutes from the start of the fire, and the maximum permissible limit for the average volumetric value of smoke density will be exceeded at approximately 34 minutes. Starting from 52 minutes, with the transition to fading mode, the smoke decreases.

Conclusions according to the schedule: The emission of significant amounts of smoke began only with the transition of the fire to the fire control mode. The risk of reduced visibility in smoke in this room is small - the maximum permissible limit will be exceeded approximately only after 34 minutes from the start of the fire, which can also be explained by the presence of large open openings in the room (doors).

Rice. 4.

Chart description: During the 26 minutes of fire development, the visibility range in the burning room remains satisfactory. With the transition to the PRV mode, visibility in a burning room quickly deteriorates.

Rice. 5.

Rice. 6.

Chart description: draw a description and conclusions from the graphs similar to those above.

Conclusions according to the schedule:

Rice. 7. Change in average volume concentration of CO 2 over time

Chart description:

Conclusions according to the schedule:

Rice. 8. Change in the average volumetric density of the gas medium over time

Chart description:

Conclusions according to the schedule:

Rice. 9. Change in the position of the plane of equal pressure over time

Chart description:

Conclusions according to the schedule:

Rice. 10. Change in the flow of fresh air into the room depending on the time of fire development

Chart description:

Conclusions according to the schedule:

Rice. eleven. Change in the outflow of heated gases from the room depending on the time of fire development

Chart description:

Conclusions according to the schedule:

Rice. 12. Change in pressure difference over time

Chart description:

Conclusions according to the schedule:

Rice. 13.

Chart description:

Conclusions according to the schedule:

Description of the fire situation at 11 minutes

At the initial moments of time, with the free development of a fire, the parameters of the gas environment in the room reach the following values:

The temperature reaches 97°C (crosses the threshold value of 70°C);

The visibility range has remained virtually unchanged and is 64.62 m, i.e. has not yet crossed the 20 m threshold;

The partial density of gases is:

c = 0.208 kg/m 3, which is less than the maximum partial density for oxygen;

c = 0.005 kg/m 3, which is less than the maximum partial density for carbon dioxide;

c = 0.4*10 -4 kg/m 3, which is less than the maximum partial density for carbon monoxide;

The PRD will be at the level of 0.91 m;

The combustion area will be 24.17 m2.

4. Time to reach threshold and critical values of physical permeability

Required time to evacuate the premises according to mathematical modeling

Table 2. Time to reach threshold values

	Thresholds	Reaching time, min
	Limit gas temperature t = 70°C
	Critical visibility range 1 cr = 20 m
	Maximum permissible partial density of oxygen c = 0.226 kg/m 3
	Maximum permissible partial density of carbon dioxide (s) prev = (s) prev = 0.11 kg/m 3	not achieved
	Maximum permissible partial density of carbon monoxide (s) pre = (s) pre = 1.16*10 -3 kg/m 3	not achieved
	Maximum average volumetric temperature of the gas medium T m = 237 + 273 = 510 K
	Critical temperature for glazing t = 300°C	not achieved
	Threshold temperature for heat detectors IP-101-1A t popor = 70°C

In this case, the minimum time for evacuation from the warehouse is the time to reach the maximum temperature of the gas environment, equal to 10 minutes.

Conclusion:

a) characterize the dynamics of the development of individual OFPs, the sequence of occurrence of various events and, in general, describe the forecast for the development of a fire;

Determining the time from the start of a fire to the blocking of evacuation routes by fire hazards

Let's calculate the required evacuation time for a room with dimensions 60·24·6, the fire load of which is baled cotton. The initial room temperature is 20°C.

Initial data:

room

free volume

dimensionless parameter

temperature t 0 = 20 0 C;

type of combustible material - cotton in bales - TGM, n=3;

calorific value Q = 16.7;

specific burnout rate = 0.0167;

speed of flame propagation over the surface of the GM;

smoke generating ability D = 0.6;

oxygen consumption = 1.15;

carbon dioxide emission = 0.578;

carbon monoxide release = 0.0052 ;

GM combustion completeness;

other parameters

reflection coefficient b = 0.3;

initial illumination E = 50 Lux;

specific isobaric heat capacity C p = 1.003?10 -3 MJ/kg?K;

maximum visibility range = 20 m;

limit values for toxic gas concentrations:

0.11 kg/m3;

1.16?10 -3 kg/m 3 ;

Calculation of auxiliary parameters

A = 1.05?? = 1.05?0.0167? (0.0042) 2 = 3.093?10 -7 kg/s 3

В = 353?С р?V/(1-) ??Q = 353?1.003?10 -3 ?6912/(1-0.6)?0.97?16.7 = 377.6 kg

V/A = 377.69/3.093?10 -7 = 1.22?10 9 c 3

Calculation of the time of onset of the PDZ of general physical fitness:

1) at elevated temperature:

2) for loss of visibility:

3) by reduced oxygen content:

4) for carbon dioxide CO 2

a negative number is obtained under the logarithm sign, so this factor does not pose a danger.

5) for carbon monoxide CO

a negative number is obtained under the logarithm sign, so this factor does not pose a danger.

Critical fire duration:

kr = min = 746; 772; = 746 s.

The critical duration of a fire is determined by the time at which the maximum permissible temperature in the room occurs.

Required time to evacuate people from the warehouse:

nv = 0.8* cr /60 = 0.8*746/60 = 9.94 min.

Make a conclusion about the adequacy/inadequacy of time for evacuation based on the calculation data.

Conclusion: compare the required evacuation times obtained by different methods and, if necessary, explain differences in results.

5. Calculation of the dynamics of general physical fitness for the level of the working area. Analysis of the fire situation at 11 minutes

The level of the working area according to GOST 12.1.004-91 “Fire safety. General requirements" is taken to be 1.7 meters.

The relationship between local and volume-average RPP values along the height of the room has the following form:

(GPP? GPP o) = (GPP? GPP o)·Z,

where is the general physical training? local (threshold) GPP value;

OFP about? initial GPP value;

General physical training? average volume value of a hazardous factor;

Z? dimensionless parameter calculated using the formula (see paragraph 4.2).

Table 3. Dynamics of development of general physical fitness at the level of the work area

Time, min

The fire area is 24.17 m.

The temperature at the level of the working area is 52.4 0 C, which does not reach the maximum permissible value of 70 0 C.

The visibility range indoors has not changed and is

2.38/0.00042 = 5666 m.

Normal oxygen concentration: 22.513 wt%.

The partial densities of O 2, CO and CO 2 at the level of the working area are equal, respectively:

1.09948?22.513/100 = 0.247 kg/m3;

1.09948?0.00211/100 = 2.3*10 -5 kg/m3;

1.09948?0.22328/100 = 0.00245 kg/m3.

Thus, calculations showed that the partial density of oxygen is above the maximum permissible limit, and that of toxic gases is below.

Rice. 14.

At the 11th minute of combustion, gas exchange occurs with the following indicators: the influx of cold air is 3.26 kg/s, and the outflow of heated gases from the room is 10.051 kg/s.

In the upper part of the doorway there is an outflow of smoky heated gases from the room; the plane of equal pressure is at a level of 1.251 m, which is below the level of the working area.

General conclusion about the work

Draw a general conclusion about the work, including:

a) a brief description of the object;

b) general characteristics of the dynamics of the RPP during the free development of a fire;

d) analysis of the response of fire detectors installed in the premises, if necessary, proposals for their replacement;

e) characteristics of the operational situation at the time of arrival of fire departments, proposals for safe evacuation of people;

f) conclusion on the feasibility and prospects of using computer programs to calculate the dynamics of physical properties during a fire.

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Fire hazards calculations pdf. Prediction of dangerous factors of fire during its free development

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The public building is one-story. The building is constructed of prefabricated reinforced concrete structures and bricks.

Dimensions of the room in plan:

Width = 12 m;

D Lina = 24 m;

Height = 4.2 m;

Plan of a public building in Figure 1.

The fire wall has a technological opening 3 m wide and high. In the event of a fire, this opening is open.

In a public building has 2 identical doorways connecting to the outside environment. Its width=1.2 m and height = 2.2 m. In case of fire, the doorways are open.

The floors are concrete, with asphalt covering.

Combustible material is furniture + PVC linoleum (0.9+1) Combustible material is located on the floor. Size of site occupied flammable material: length=11 m, width=5 m. Quantity combustible material is 12 00kg.

Collection of initial data

Geometric characteristics of the object.

The position of the center of the orthogonal coordinate system is selected in the lower left corner of the room on the plan (Fig. p.1). The x-axis is directed along the length of the room, the y-axis along its width, and the z-axis vertically along the height of the room.

Geometric characteristics:

room: length L=24 m; width B=12 m; height H=4.2 m.

doors (number of doors N to =2): height h d1.2 =2.2m; width b d1.2 = 1.2 m; coordinates of the lower left corner of the door: y d1 = 0 m; x d1 = 10 m; y d2 = 12 m; x d2 =4.2m;

open windows (number of open windows N oo =2): height h oo 1.2 =1.8 m; width b oo 1,2 = 2 m; coordinates of one lower corner of the window: x oo 1 = 0 m; y oo 1 = 5 m; x oo 2 = 24 m; y oo 2 = 5 m; z oo 1,2 =0.8m;

closed windows (number of closed windows N zo =1): height h zo1 =1.8 m; width b zo1 =6.0m; coordinates of one lower corner of the window: x zo1 = 8 m; y zo1 =12 m; z zo1 =0.8m; glazing destruction temperature Tcr = 300C;

technological opening (number of openings Npo=1): height h p1 = 3.0 m; width b p1 =3.0m; coordinates of the lower left corner of the opening: y p1 = 18m; x p1 =20.0m.

Properties of combustible load in select according to the typical flammable load base (Appendix 3 (furniture + PVC linoleum (0.9+1) No. 11))

lower heat and combustion Q R n = 14 MJ/kg ;

flame propagation speed V l = 0.015 m/s;

specific burnout rate Sh 0 = 0,0137 kg/(m 2 With );

specific smoke emission D = 53 Np*m 2 /kg;

specific oxygen consumption when burning L o2 = 1,369 kg/kg;

release of carbon monoxide L from = 0.03 kg/kg;

allocation of two To isi carbon L co2 = 1,478 kg/kg;

Other hot load characteristics:

total mass of hot load M?=1200 kg;

open surface length l pn = 11 m;

width of the open surface b pn = 5 m;

height of the open surface from the floor level h pn = 0 m;

Initial boundary conditions.

We set the initial and boundary conditions:

The temperature of the gas environment of the room is T m 0 =20? WITH;

The outside air temperature is T a =20? WITH;

The pressures in the gas environment of the room and the outside air at floor level are equal to P a = 10 5 Pa.

Selection of fire development scenario.

The place of combustion is located in the center of the site occupied by the GM

2. Description of the mathematical model of fire development in the premises

To calculate the dynamics of dangerous fire factors, we use an integral mathematical model of the free development of a fire in a room.

According to the initial data in the basic system of differential equations, it should be assumed that

G pr =0; G out =0; G ov =0; Q 0 =0;

where G in and G out are the flow rates of the supply and exhaust fans;

G ov - consumption of gaseous fire extinguishing agent; Q 0 - heat flow released by the heating system.

For a fire under given conditions, we can assume in the energy equation that

those. the internal energy of the environment in a room during a fire remains practically unchanged

Taking into account the above, the system of basic equations of the IMM has the form

;

;

where V is the volume of the room, m 3; c m , T m , p m - average volumetric densities, temperatures and pressures, respectively; m m is the average volume concentration of the combustion product; X O 2 - average volume concentration of oxygen.

3. Calculation of the dynamics of fire hazards in the premises

Table 3.1 Initial data for calculating the dynamics of fire hazards in the premises

Atmosphere:

Pressure, mmHg

Premises:

Length, m

Width, m

Table 3.2 Results of calculations of the dynamics of fire hazards in the premises

Table 3.3 Results of calculations of the dynamics of fire hazards in the premises

Table 3.4 Results of calculations of the dynamics of fire hazards in the premises

Table p3.5 Results of calculations of the dynamics of fire hazards in the premises

Note:

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