Mathematical models of fire development indoors are described in the very general Changes in the status parameters of the environment, enclosing structures and equipment elements over time. Equations, mathematical models of fire in the room are based on the fundamental laws of physics: the laws of preserving mass, energy, the amount of movement. These equations reflect the entire set of interconnected and interdependent processes inherent in the fire - heat dissipation as a result of combustion, chimping and changing the optical properties of the gas environment, the release and distribution of toxic combustion products with the environment and with adjacent rooms, heat exchange and heating the enhancement structures and others. Integral method The simulation is based on a fire modeling at the level of averaged characteristics (medium-value parameters, which are characterized by conditions in the volume of space: temperature, pressure, composition of the gas environment, etc. for any time). This is the most simple in mathematically model of a fire. It is represented by a system of ordinary differential equations. Secondary functions are the average sharing parameters of the gas medium in the room, and the independent variable is the time. There are also differential and zone models.
2. Prediction of dangerous fire factors in a room based on the zone mathematical model.
Zone method The calculation of the dynamics of the OFP is based on the fundamental laws of nature - the laws of preserving the mass, impulse and energy. The gas medium of premises is an open thermodynamic system, exchanging mass and energy with the environment through open openings in the enclosing room structures. Gas medium is multiphase, because It consists of a mixture of gases (oxygen, nitrogen, combustion products and gasification of fuel material, gaseous fire extinguishing agent) and fine particles (solid or liquid) smoke and fire extinguishes. In the zone mathematical model, the gas volume of the room is divided into characteristic zones, in which the corresponding conservation laws of conservation are used to describe the heat andasseman. The dimensions and the number of zones are chosen in such a way that within each of them the heterogeneity of the temperature and other fields of the parameters of the gas medium was minimal, or from some other assumptions determined by the objectives of the study and the location of the combustible material. The most common is a three-zone model in which the size of the room is divided into the following zones: a convective column over a fire center, a sealing layer of heated gas and a cold air zone. As a result of the calculation of the zone model, there are dependence on the time of the following parameters of heat and mass transfer: medium-sharing values \u200b\u200bof temperature, pressure, mass concentrations of oxygen, nitrogen, fire extinguishing gas and combustion products, as well as the optical density of smoke and range of visibility in the heated shrouded indoor layer; the lower boundary of the heated smoke of the sealing layer; The distribution in the height of the column of mass flow raised over the cross section of the column of temperature and effective degree of black mixture; mass costs of the expiration of gases outside and the influx of outdoor air inside through open opening; heat fluxes that are discharged into the ceiling, walls and gears, as well as emitted through the openings; Temperatures (temperature fields) enclosing structures.
3. Forecasting hazardous fire factors in a room based on a differential mathematical model. The differential mathematical model allows you to calculate for any moment the development of the fire the values \u200b\u200bof all local status parameters in all points of space indoors. The differential model of the calculation of heat-mass exchange during a fire consists of a system of the main differential equations of the laws of the preservation of pulse, mass and energy. The main equations of the mathematical model include: the equation of the continuity of the gas mixture is the mathematical expression of the law of conservation of the gas mixture, the energy equation is a mathematical expression of the law of conservation and conversion of energy, the equation of continuity for the component of the gas mixture, the equation of the state of the mixture of ideal gases, the equations of thermophysical parameters of the gas mixture of gases Consides the chemical composition of the mixture. Additional ratios of the mathematical model include: the calculation of the process of having structures of building structures (materials of walls, overlapping, gender and columns), the calculation of turbulent heat and mass exchange, the calculation of radiation heat dissolument, calculating the burnout of the fuel load, i.e. Determining the magnitude of the remaining mass of liquid or solid fuel after partial burnout, combustion modeling (modeling of the combustion area can be carried out using energy sources, mass and smoke without taking into account the chemical kinetics and thermogase-shaped conditions in the field of combustion).
4. Critical duration of fire based on an integral mathematical model.
The critical duration of the fire is the time to achieve extremely permissible values \u200b\u200bof the IPP values \u200b\u200bin the residence area of \u200b\u200bpeople. The formula for calculating the checkpoint at a temperature: where T cr - the maximum allowable temperature value in the working area. To calculate the CAT under the condition for achieving the concentration of oxygen in the working area of \u200b\u200bits maximum allowable value: 
. To calculate the CAT under the condition for achieving the concentration of toxic gas in the working area of \u200b\u200bits maximum allowable value: 
. For calculating the CAT for loss of visibility: 
. These formulas can be used only for premises with small open openings.
LECTURE
under the discipline "Forecasting hazardous fire factors"
Topic number 3. "Gas exchange room and the thermophysical functions necessary to describe
Closed Fire »
Lecture Plan:
Lecture 1.2. Additional equations of the integral mathematical model of a fire for calculating the expenditures of outgoing gases and entering airways
1.1. Introduction
1.2. Pressure distribution at the height of the room
1.3 Plane of equal pressure and operating modes
1.4. Distribution of pressure drops at the height of the room
1.5. Formulas for calculating the gas consumption emitted through rectangular opening
1.6. Formulas for calculating air flow coming through rectangular opening
1.7. The effect of wind on gas exchange
Lecture 3.4. Equations of the integral fire model for calculating the heat flux in the fencing and the burnout speed of combustible materials
2.1 Approximate assessment of the magnitude of the heat flux in the fence
2.2 Empirical methods for calculating the heat flux in fencing
2.3 Semi-empirical methods for calculating heat flux in fencing
2.4 Methods for calculating the burnout speed of combustible materials and heat dissipation rate
Goals lectures:
1. Training
As a result of listening, listeners should know:
Integral equations for calculating gas exchange parameters
Equations integral model To determine the heat fluxes to the designs of the room during a fire
Effects of external conditions for heat and gas exchange in case of fire
To be able to: predict the situation on a fire, taking into account the heat-sharing
2. Developing: allocate the most important, independence and flexibility of thinking, the development of cognitive thinking.
Literature
1. D.M. Rozhkov Forecasting hazardous fire factors indoors. - Irkutsk 2007. p.89
2. Yu.A. Koshmarov, M.P. Bashkirtsev thermodynamics and heat transfer in the fire business. VIPTSTS MVD USSR, M., 1987
3. Yu.A. Koshmarov Forecasting hazardous factors in the room. - Moscow 2000. p.118
4. Yu.A. Koshmarov, V.V. Rubtsov, the growing processes of dangerous factors of fire in the industrial premises and the calculation of the critical duration of the fire. MPB MVD of Russia, M., 1999
Additional integrated equations
Mathematical model of fire for calculation
Expenditure of outgoing gases and incoming
Through air openings
Introduction
In case of fire, gas exchange placing with the environment through the openings of various purposes (windows, doors, technological holes, etc.).
The growth of gas movement through the openings is the pressure drop, i.e. The difference between the indoor pressure and pressure in the surrounding atmosphere. The pressure drop is due to the fact that during the fire, the density of the gas medium indoors is significantly different from the density of the outer air. In addition, it is necessary to take into account the impact of the wind on the magnitude of this drop. The fact is that the outdoor pressure on the windward side of the building is higher than the outdoor pressure on the leeward side. Consider the conditions when the wind is absent.
Introduction
In modern conditions, the development of economically optimal and efficient fire fighting events Unfinite without a scientifically substantiated forecasting dynamics of dangerous fire factors (OFP).
Forecasting OFP required:
· when creating and improving signaling systems and automatic fire extinguishing systems;
· when developing operational extinguishing plans (planning actions of combat units in a fire);
· when evaluating the actual limits of fire resistance;
· to calculate fire risk and many other purposes.
Modern methods of forecasting OFPs allow not only to predict the likely fires, but also to simulate the events that have occurred to analyze and evaluate the action of the RTP.
Dangerous fire factors affecting people and material values \u200b\u200b(according to the Federal Law of the Russian Federation of July 22, 2008 No. 123-FZ " Technical Regulations About requirements fire safety"), Are:
· Flame and sparks;
· increased temperature environment;
· reduced oxygen concentration;
· toxic combustion and thermal decomposition products;
· reduction of visibility in smoke;
· Heat flow.
From scientific positions, hazardous fire factors are physical concepts and, therefore, each of them is presented in quantitatively physical.
Modern scientific methods of forecasting OFP are based on mathematical models of fire. The mathematical model of the fire describes in the general form a change in the state of the medium in the room over time, as well as the parameters of the state of the enclosing structures of this room and various elements (technological) equipment.
The main equations from which the mathematical model of the fire flow out of the fundamental laws of nature: the first law of thermodynamics and the law of preserving the mass. These equations reflect and link the entire set of interrelated and interdependent processes inherent in fire, such as heat dissipation as a result of burning, smoking in the flame zone, changing the optical properties of the gas environment, the release and distribution of toxic gases, the gas exchange room with the environment and with adjacent rooms, heat exchange and heating the enclosing structures, reducing the concentration of oxygen indoors.
The methods of forecasting OFP differ depending on the type of the mathematical model of the fire. Mathematical models of fire in the room are conventionally divided into three types: integral, zone and field (differential).
To make a scientifically substantiated forecast, you need to refer to a particular fire model. The choice of model is determined by the goal (tasks) of the forecast (studies) for the specified unambiguing conditions (characteristics of the room, fuel material, etc.) by solving the system of differential equations that form the basis of the selected mathematical model.
The integral fire model allows you to get information (i.e., allows you to make a forecast) on the mid-billing values \u200b\u200bof the state of the medium 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. medium-sharing) parameters of the medium with their limit values \u200b\u200bin the working area, formulas obtained on the basis of experimental studies of the spatial temperature distribution, concentrations of combustion products, optical smoke density, etc. d.
However, even when using an integral fire model, it is impossible to obtain an analytical solution of the system of ordinary differential equations in the general case. The implementation of the selected prediction method is possible only by its numerical solution using computer simulation.
1. Theme and Currency Tasks
Course work is one of the types of independent academic work of students on the development of educational material and the final stage of studying the methods of forecasting OFP on the basis of mathematical models of fire considered at the discipline "Prediction of hazardous factors of fire", as well as a form of control by educational institution for the level of relevant knowledge and cadet skills.
Course work puts the following tasks in front of the listeners:
· consolidate and deepen knowledge in the field of mathematical modeling dynamics of dangerous fire factors;
· on specific examples, information about the degree of interconnection and interconnectedness of all physical processes inherent in the fire (gas exchange room with the environment, heat dissipation in the flame zone and the heating of building structures, chimping and changing the optical properties of the gas medium, isolation and distribution of toxic gases, etc.);
· issimate the methodology for forecasting OFP using a computer program that implements the integral mathematical model of the fire;
· get the use of computer programs when studying fires.
The topic and the goal of the course work - predicting hazardous factors in the room (purpose and other characteristics of which are determined by the task option).
2. Requirements for the content and design of the course work
Course work is performed in accordance with the guidelines and consists of a calculating and explanatory note and the graphic part. The calculation and explanatory note consists of an explanatory text, the results of calculations in the form of tables, drawings and schemes reflecting the geometric characteristics of the object and the picture of the gas exchange indoors in the fire. The graphic part is represented by the graphs of the development of dangerous factors of the fire in the room during the time.
The required reference material is given in applications to the instructions and in the recommended literature.
Before proceeding to perform the course work, it is necessary: \u200b\u200bto study the material on discipline, familiarize yourself with the guidelines, to choose the recommended training, reference and regulatory literature. Replies for each task item are issued in an unfolded with justification.
The work should be done neatly, ink in black or printed in black font on the print sheets of A4 format. The text in the explanatory note should be written smaller, without cutting words (with the exception of generally accepted abbreviations), on one side of the sheet. A computer version of the work is recruited in the Word text processor, Times New Roman font with 1-1,5 interval. Font size for text - 12 or 14, for formulas - 16, for tables - 10, 12, or 14. The size of the fields on the sheet is 2 cm from all sides. Paragraph indent of at least 1 cm.
When calculating the required evacuation time, formulas and substituted values \u200b\u200bare given, units of measurement of physical quantities obtained in response.
The headlines of the sections and chapters are written in capital letters. Headers of subsections - lower case letters (except first uppercase). Word transfer in headlines are not allowed. The point at the end of the title is not put. The numbering of tables, drawings and graphs should be through.
The course work pages must be numbered by Arabic numbers. The first page is the title page, the second - the task for the execution of the course work, the third - the content, etc. On the first page of the course work number is not put. Pages of the course work, besides the title leaf, and tasks for the course work must be numbered. The task form for the execution of the course work is given in Appendix 1.
On the title page should be indicated:
the name of the Ministry, educational institution and the department, on which the term work is performed;
the topic of the course work and the option of task;
FULL NAME. listener who completed the course work;
title, position, Full name supervisor;
city and year of the course work.
At the end of the work, it is necessary to indicate the used literature (surname and initials of the author, the full name of the book, publishing house and the year of publication). The listener must sign, put the listener, put the date and pass to the check in the Faculty of absentee learning. The presence of admission to protection is the basis for calling the listener to the laboratory and examination session.
If the work satisfies the requirements for it, the head allows it to be protected. The work recognized as not responding with presented requirements is returned to the student on refinement.
Protection of coursework by listeners of the faculty of absentee training can be carried out during the session. The results of the defense are estimated on the four-point system: "excellent", "good", "satisfactory", "unsatisfactory." The project manager affixed an assessment on a title page of work, in the statement, the credentials of the student and assures the signature. Only positive evaluations are affixed.
Upon receipt of unsatisfactory assessment, the listener must re-execute the work on a new topic or recycle the former.
3. Selecting a task option and source data
The option for execution of the course work is determined by the number in the list of the educational group (by number in the group log). The number of the option is indicated on the title paper sheet. Depending on the year of the receipt of listeners for training (a set of 2010, 2011, etc.) initial data for calculations (temperature atmospheric air and indoors, the size of the room and the openings, the combustible load parameters, etc.) are shown in Tables 1-5 (Appendix 2).
Data obtained using computer simulation and necessary for execution of chapters 3 are issued by options individually in in electronic format At the installation lecture on discipline.
Additional data for all options:
critical temperature for glazing - 300 ° C;
number of openings - 2 (windows and door);
mechanical ventilation - absent;
automatic fire extinguishing installation (AUP) - missing;
all other not specified parameters take default.
Abbreviationadopted when exposing the course "Forecasting hazardous factors":
OFP - dangerous fire factors;
PDZ is the maximum permissible value of a dangerous fire factor;
PRD - plane of equal pressure (neutral plane);
1.In accordance with the option of task in the 1st chapter of the course work, make calculation of the initial parameters of the combustible load in the room under consideration.
2.Draw a building plan, indicate the size of the room and a fuel load.
.In Chapter 2, we describe the system of differential equations, on the basis of which an integral mathematical model of a fire in the room was created, with a complete explanation of all physical quantities in it.
.In accordance with the task course, take ready-made tabular data from the teacher (Table 1) on the dynamics of the development of medium-wide values \u200b\u200bof the OFP with the free development of the fire, calculated using the INTMODEL computer program that implements the integral mathematical model in the room.
5. In tabular data to construct the corresponding graphic dependences of the medium sharing parameters on the time of fire development: M (T);
μ m (t); LVID (T); (t); (t); (t); Cm (t); Y * (t); Special (T); GB (T); GG (T); DP (T).
6.Make a description and comparative conclusions on the obtained graphs, explain the jumps on the charts (if available).
7.Guided by the data and graphic dependencies of the OIS from time to be calculated using a computer program, in the 4th chapter of the course work, to characterize the dynamics of the development of individual OFP, the sequence of the onset of various events, as a whole, describe the fire development forecast.
.Determine the critical duration of the fire under the condition of achieving each dangerous factor of fire the maximum permissible (mid-payable) value and necessary time Evacuation of people from the premises under consideration:
a) according to mathematical modeling (reduce the results in Table 2);
b) according to the method of determining the time from the beginning of the fire prior to blocking evacuation paths as a result of the dissemination of dangerous fire factors according to Appendix No. 5 to the order of the Ministry of Emergency Situations of Russia of July 10, 2009 No. 404 to clause 33 (methods for determining the calculated fire risk values \u200b\u200bon production facilities).
The resulting calculation results are reflected in the 4th chapter of the course work, there to also draw conclusions: what is the similarity and the difference between these techniques than can explain the difference in the calculation results.
9.According to the results of Table 2, we conclude the timeliness of the operation of fire detectors installed indoors. If they are ineffective work, to offer them an alternative replacement (Appendix 3).
10.Conduct calculations of the OISP parameters for the working area level (OFP l. ) With the free development of the fire at the time of time 11 minutes, according to the formula:
(OFP l. - OFP 0) \u003d (OFP m - OFP 0) · Z,
where official l. - local IPP value;
OFP 0 - initial IPP value;
OFP m. - Medium sharing value of a hazardous fire factor; - a dimensionless parameter calculated by the formula:
For H.£ 6 m,
where h. - Height of the working area, m;
N. - The height of the room, m.
11.The results of the calculations of the OIS for the level of the working area are made to the table in the 5th chapter of the course work.
12.Based on the calculations obtained for the time of 11 minutes:
a) bring the scheme of gas exchange indoors for the development time of the fire for 11 minutes with the free development of the fire;
b) give a detailed feature of the operational situation on the fire based on the OIS calculations for the level of the working area, to propose measures to carry out the safe evacuation of people.
13.Make a general conclusion in the course work. The output must include:
a) a brief description of the object;
(b) Analysis of the OFP, which have reached its maximum permissible value at 11 minutes with free fire development;
c) comparing the critical time of the PDZ on dangerous fire factors according to the calculations of the INTMODEL computer program and the method of determining the time from the beginning of the fire before blocking the evacuation paths as a result of the dissemination of dangerous fire factors according to Appendix No. 5 to the order of the Ministry of Emergency Situations of Russia of July 10, 2009 No. 404;
d) Analysis of the timeliness of the triggering of fire detectors installed in the premises, if necessary, proposal to replace them;
(e) A description of the actions of the facility personnel in the event of a fire, based on the data obtained during the calculations;
(f) A description of the actions of fire units based on the situation that their arrival time is 10 minutes from the beginning of the fire development;
(g) Recommendations to the owner of the premises and firemanship calculations that allow secure evacuation in the event of a fire in the room. Recommendations should be linked with the results of forecasting the dynamics of the OFP for this room;
(h) Conclusion about the feasibility and prospects for using computer programs to calculate the dynamics of OFP during a fire.
14.At the end of the course work, lead a list of references.
5. Sample course work
RUSSIAN EMERGENCY SITUATIONS MINISTRY
Federal State Budgetary Educational
establishment of higher vocational education
"Ural Institute of State fire service
Ministry of the Russian Federation for Affairs civil Defense,
emergency situations and elimination of the effects of natural disasters "
Department of Physics and Heat Exchange
COURSE WORK
Topic: Forecasting hazardous factors in a storage room
Option number 35
Performed:
listener of the study group З-461
senior Lieutenant internal service Ivanov I.I.
Checked:
senior teacher of the department
physics and heat exchange, Ph.D., Captain of the internal service
Subacheva A.A.
Yekaterinburg
to perform course work
under the discipline "Prediction of dangerous factors of fire"
Listener Ivanov Ivan Ivanovich
Option number 35 Course 4 Group Z-461
Object name: cotton
Initial data
Block atmosphere, mm. RT. Article.760temoper, 0With 20 blocks of placed, M60, M6Shirina, M24temper, 0C20Proot 1 - regular (door) bottom slice, m0? width, m3,6store slice, m3vice, 0C20Proot 2 - regular (windows)? Width, M24Nizhniy slice, M1,2Viscretion, 0C300 Turning Sing, M2.4Block LoadsVide Fuel Materials in Tyuyl Empower NP * M 2/ kg0,6dlin, m32,9 voltage CO, kg / kg0.0052 wirina, m13,0,tovel 2, kg / kg0,578 Nationality of GG, kg4320 lesible burnout speed, kg / m 2* C0.0167 Type of heat MJ / kg16) flame propagation, m / s0.0042 Consumption of oxygen kg / kg1,15
Deadline: "____"__________
Listener ____________________ Head _______________
1. Source data
The fire premises is located in a single-storey building. The building is built from precast concrete structures and bricks. In the building, along with the warehouse, there are two working cabinets. Both rooms are separated from a warehouse by fire wall. The object plan is shown in Figure 1.
(It is required to put on the diagram the size of the room and the calculated mass of the combustible load according to its version!)
Fig. 1. Plan of the building
Warehouse size:
length L1. \u003d 60 m;
width L2. \u003d 24 m;
height 2H \u003d 6 m.
In the outer walls of the warehouse room there are 10 identical window openings. The distance from the floor to the lower edge of each window opening yH \u003d 1.2 m. The distance from the floor to the upper edge of the opening of YB \u003d 2.4 m. The total width of the window openings \u003d 24 m. The glazing of window openings is made of ordinary glass. The glazing is destroyed with the mid-paying temperature of the gas medium indoor, equal to 300 ° C.
The placement of the warehouse is separated from the working offspring of fire doors, the width and height of which are 3 meters. With the fire, these openings are closed. The warehouse room has one doorway connecting it with an outer environment. The width of the opening is 3.6 m. The distance from the floor to the top edge of the doorway YB \u003d 3, yn \u003d 0. With a fire, this doorway is open, i.e. Opening temperature 20 0c.
The floors are concrete, with asphalt coating.
Fuel material It is cotton in bales. The share of the area occupied by the combustible load (GG) \u003d 30%.
Floor area, occupied by GN, is located by the formula:
where? Floor area.
The amount of fuel material is 1 p0 \u003d 10. The total mass of the combustible material.
The burning begins in the center of the rectangular platform, which is occupied by um. Sizes of this site:
Properties of GG are characterized by the following values:
heat combustion Q \u003d 16.7;
selection of carbon oxide \u003d 0.0052.
Mechanical ventilation in the premises is missing. Natural ventilation is carried out through door and window openings.
Heating central water.
External atmospheric conditions:
the wind is absent, the outdoor temperature 20 0C \u003d 293 to
pressure (at y \u003d h) p but \u003d 760 mm. RT. Art., i.e. \u003d 101300 Pa.
Parameters of the state of the gas environment indoors before the fire:
T \u003d 293 to (according to the selected option);
P \u003d 101300 Pa;
Other parameters:
critical temperature for glazing? 300 O. FROM;
material of enclosing structures - reinforced concrete and brick;
indoor air temperature - 20 o FROM;
automatic fire extinguishing system? absent;
contamination mechanical ventilation? absent.
2. Description of the integral mathematical model of free fire development in the storage room
The integral mathematical model of a fire in the room is based on the fire equations set out in the works. These equations flow out of the basic laws of physics: the law of preserving the substance and the first law of thermodynamics for the open system and include:
the equation of the material balance of the gas environment indoors:
V (DCM / DF) \u003d GB + W - GR, (1)
where V is the size of the room, m 3; from m. - Medium Valuation Density of Gas Environment kg / m 3; F - time, C; G. B. and G. r. - mass costs entering the air and flowing out of the gases, kg / s; W is the mass rate of fuel burning, kg / s;
oxygen balance equation:
VD (P. 1) / DF \u003d X 1V. G. B. - X. 1n. 1G. r - W l 1Yu, (2)
where X. 1 - medium sharing mass concentration of oxygen indoors; H. 1V. - oxygen concentration in the outgoing gases; N. 1 - coefficient taking into account the difference in oxygen concentration in the outgoing gases x 1G. 1, N. 1 \u003d H. 1G. / X. 1; L. 1 - speed of oxygen consumption during burning, p 1 - partial density of oxygen indoors;
balance balance equation:
VD (P2) / DF \u003d W L2U - X2N2GR, (3)
where X. i. - medium sharing concentration of I-go of the combustion product; L. i. - the release rate of the I-GO product of the combustion (CO, CO2); N. i. - coefficient taking into account the difference between the concentration of I-go of the product in the outgoing gases x ig from the middle-value value x i. , N. i. \u003d X. ig / H. i. ; R 2 - partial density of combustion products indoors;
the equation of the balance of the optical amount of smoke indoors:
VD () / d \u003d ds - N4 GR / PM - KCSW, (4)
where - the mid-paying optical density of smoke; D is the smoke-forming ability of the GM; N4 is a coefficient that takes into account the difference between the concentration of smoke in the heated gases from the medium-sharing optical concentration of smoke, N4 \u003d mmg / mm;
energy Balance Equation U:
dU / DF \u003d h. Q. p. n. sh + I. g. sh + S. rV. T. in G. in - FROM r T. m. m Gr. - Q. w. , (5)
where P. m. - mid-pay pressure indoor, PA; FROM pm. , T. m. - mid-paying values \u200b\u200bof the isobar heat capacity and temperature indoors; Q.p.n.- lower working heat combustion GG, J / kg; FROM rV. , T. in - the isobaric heat capacity and the temperature of the incoming air, K; I. g. - Enhaulpia gasification of combustion products GN, J / kg; M is a coefficient that takes into account the difference in temperature T and isobaric heat capacity with rG outgoing gases from mid-pay temperature t m. and medium sharing isobaric heat capacity cfm ,
m \u003d S. rG T. g. / SRM. T. m. ;
Yu - the coefficient of completeness of the combustion of GG; Q. w. - heat flow to fence, W.
Medium sharing temperature T. m. associated with medium pressure pressure m. and density R. m. The equation of the state of the gas environment indoors:
P. m. \u003d S. m. R. m. TM. .(6)
The equation of the material balance of the fire, taking into account the operation of the supply and exhaust system of mechanical ventilation, as well as, taking into account the operation of the system of volumetric fire extinguishing inert gas, will take the following form:
VDP. m. / DF \u003d sh + g B. - G. r. + G. etc - G. out + G. o (7)
The above equation system is solved by numerical methods using a computer program. An example is an intmodel program.
. Calculation of the speakers of the OFP using the IntModel computer program
Computer simulation results
The intmodel training computer program implements the mathematical model of the fire described above and is intended to calculate the dynamics of fire development of liquid and solid combustible substances and indoor materials. The program allows you to take into account the opening of the openings, the operation of mechanical ventilation systems and the inert gas extinguishing gas, and also takes into account the oxygen balance of the fire, allows you to calculate the concentration of carbon oxides CO and 2, smallestness of the room and visibility range in it.
Table 1. Dynamics of development of the parameters of the gas environment indoors and the coordinates of the PRP
While, the Mind Temperature TM, 0Soptical density of smoke μm, NP / mdnal diffraction of lm, m,
wt.% , wt.% C m, kg / m 3Neutral plane - PRP Y *, MG in kg / cg g. , kg / sdp, passes fair , 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
Changing the medium payroll parameters of the gas environment in time
Fig. 2. Changing the mid-paying temperature of the gas environment in time
Description Graphics: The temperature rise in the first 22 minutes of the fire can be explained by burning in the PRN mode, which is due to sufficient oxygen content in the room. From 23 minutes, the fire turns into PPV mode with a significant decrease in oxygen concentration. From 23 minutes to 50 minutes, the burning intensity is constantly decreasing, despite the continued increase in burning area. Starting from 50 minutes, the fire goes into the PRN mode, which is associated with an increase in oxygen concentration as a result of fuel burning.
Conclusions on schedule: On the temperature schedule, it is possible to conditionally allocate 3 stages of fire development. The first stage is the increase in temperature (approximately 22 minutes), the second is a quasistationary stage (from 23 min. Up to 50 min.), And the third is the attenuation stage (from 50 min. Until full burning of the fuel load).
Fig. 3. Changing the optical density of smoke in time
Description Graphics: In the initial stage of fire, smoke slightly, fullness of combustion is maximal. Basically, smoke begins to stand out after 22 minutes from the start of fire, and exceeding the PDZ on the mid-paying value of the smoke density will occur at about 34 minutes. Starting from 52 minutes, with the transition to the attenuation mode, the smoke decreases.
Conclusions on schedule: The allocation of significant amounts of smoke began only with a fire transition to PRV mode. The danger of a decrease in visibility in the smoke in this room is small - PDZ will be exceeded approximately only after 34 minutes from the start of fire, which can also be explained by the presence in the room of open opening of a large size (door).
Fig. 4. Changing the range of visibility indoors in time
Description Graphics: For 26 minutes of fire development, visibility range remains satisfactory. With the transition to PRV mode, visibility in the burning room is quickly worse.
Conclusions on schedule: The range of visibility is associated with the optical density of smoke by the ratio. That is, the range of visibility is inversely proportional to the optical density of smoke, so with an increase in smoke, visibility range is reduced and vice versa.
Fig. 5. Changing the mid-paying oxygen concentration in time
Description Graphics: In the first 9 minutes of fire development (initial stage), the mid-paying concentration of oxygen almost does not change, i.e. The oxygen consumption is low, which can be explained by the small size of the burning focus at this time. As the combustion area increases, the oxygen content in the room decreases. Approximately 25 minutes from the start of combustion, the oxygen content is stabilized at 10-12 wt.% And it remains almost unchanged to about the 49th minute of fire. Thus, from the 25th to 49th minute, the PRV mode is implemented in the room, i.e. The combustion in conditions of lack of oxygen. Starting with the 50th minute, the oxygen content increases, which corresponds to the attenuation stage at which the incoming air is again gradually fills the room.
Conclusions on schedule: A graph of oxygen concentration, similar to the temperature schedule, allows you to identify the moments of changing the modes and burning stages. The moment of exceeding the PDZ in oxygen on this schedule should not be traced, for this you will need to recalculate the mass fraction of oxygen into its partial density, using the value of the medium-paying gas density and the formula .
Fig. 6. Changing the medium-sharing concentration of the Fire development time
Description Graphics: make a description and conclusions by graphs by analogy with the above.
Conclusions on schedule:
Fig. 7. Changing the mid-payroll concentration of CO2 in time
Description Graphics:
Conclusions on schedule:
Fig. 8. Changing the medium payroll density of the gas environment in time
Description Graphics:
Conclusions on schedule:
Fig. 9. Changing the position of the plane of equal pressure over time
Description Graphics:
Conclusions on schedule:
Fig. 10. Changing the influx of fresh air to the room from the time of fire development
Description Graphics:
Conclusions on schedule:
Fig. 11. Changing the outflow of heated gases from the room from the time of fire development
Description Graphics:
Conclusions on schedule:
Fig. 12. Changing the pressure difference over time
Description Graphics:
Conclusions on schedule:
Fig. 13. Changing the area of \u200b\u200bburning during a fire in time
Description Graphics:
Conclusions on schedule:
Description of the situation in the fire at the time of 11 minutes
According to paragraph 1 of Art. 76 FZ-123 "Technical Regulations on Fire Safety Requirements", the time of arrival of the first division of fire protection to the call site in urban settlements and urban districts should not exceed 10 minutes. Thus, the design of the situation on the fire is held 11 minutes from the beginning of the fire.
At the initial moments of time, with the free development of the fire, the parameters of the gas environment in the room reach the following values:
The temperature of 97 ° C is achieved (the threshold value is 70 ° C);
Visibility range has practically changed and is 64.62 m, i.e. not yet passes the threshold value of 20 m;
Partial gas density is:
c \u003d 0.208 kg / m3, which is less than the limit partial density of oxygen;
c \u003d 0.005 kg / m3, which is less than the limiting partial density of carbon dioxide gas;
c \u003d 0.4 * 10-4 kg / m3, which is less than the limit partial density of carbon monoxide gas;
PDP will be at the level of 0.91 m;
the area of \u200b\u200bburning will be 24.17 m2 .
Thus, the calculations have shown that by 11 minutes the free development of the fire, the following OFP will reach their maximum permissible value: the mid-paying gas temperature (for 10 minutes).
. Time to achieve threshold and critical IPP values
According to FZ-123, the "Technical Regulations on Fire Safety Requirements", the necessary evacuation time is the minimum time to achieve one of the dangerous factors of its critical value.
Required evacuation time from the room according to mathematical modeling
Table 2. Time to achieve threshold values
NU N / F / POPGNAY VALLS OF ACHIEMENT, MIN1 RECEMENT GLANGE TEMPERATURE T \u003d 70 ° C102Critical visibility range 1 kr \u003d 20 m333 The permissible partial density of oxygen with \u003d 0.226 kg / m 3104 The permissible partial density of carbon dioxide (with )fore \u003d (S. )fore \u003d 0.11 kg / m 3the permissible partial density of carbon oxide is not achieved (with )fore \u003d (S. )fore = 1,16*10 -3 kg / m 3it is not achieved with a maximum average sharing temperature of the gas environment T m. \u003d 237 + 273 \u003d 510 K307Critical temperature for glazing T \u003d 300 ° CNA is achieved8Porovaya temperature for thermal detectors IP-101-1A Tpopor \u003d 70 ° C9
In this case, the minimum time for evacuation from the warehouse room is the time to achieve the maximum temperature of the gas medium, equal to 10 minutes.
Output:
a) characterize the dynamics of the development of individual OFP, the sequence of the onset of various events and in general describe the forecast for the development of the fire;
b) make a conclusion about the timeliness of the operation of fire detectors installed indoors (see paragraph 8 of Table 2). In the event of an ineffective work of fire detectors, to offer them an alternative (Appendix 3).
Determining the time from the beginning of the fire before blocking
evacuation paths dangerous fire factors Calculate the required time of evacuation for the room with dimensions 60 · 24 · 6, the fireload in which is cotton in bales. The initial temperature indoor 20 ° C.
Initial data:
room
free volume
dimensionless parameter
temperature T0 \u003d 20 ° C;
view of a fuel material - cotton in bales - TGM, N \u003d 3;
heat combustion Q \u003d 16.7;
specific burnout \u003d 0,0167;
flame propagation rate on the surface of the GM;
smoke-forming ability d \u003d 0.6;
oxygen consumption \u003d 1.15;
the release of carbon dioxide \u003d 0.578;
separation of carbon oxide \u003d 0.0052;
fullness of combustion of um;
other parameters
reflection coefficient b \u003d 0.3;
initial illumination E \u003d 50 LCs;
specific isobaric heat capacity cf \u003d 1,003? 10 -3 MJ / kg? K;
limit range of visibility \u003d 20 m;
the limit values \u200b\u200bof the concentration of toxic gases:
0.11 kg / m3;
1,16? 10-3 kg / m3;
Calculation of auxiliary parameters
A \u003d 1.05 ?? \u003d 1.05? 0,0167? (0,0042) 2 \u003d 3,093? 10-7 kg / c3
B \u003d 353? Wed? V / (1-) ?? Q \u003d 353? 1,003? 10-3? 6912 / (1-0.6)? 0.97? 16,7 \u003d 377.6 kg
V / A \u003d 377.69 / 3,093? 10-7 \u003d 1,22? 109 C3
Calculation of the onset of PDZ OFP:
1)at elevated temperature:
2)by loss of visibility:
3)by low oxygen content:
4)on carbon dioxide CO2
a negative number is obtained under the logarithm sign, therefore this factor is not dangerous.
5)on carbon monoxide
a negative number is obtained under the logarithm sign, therefore this factor is not dangerous.
Critical duration of fire:
tKR \u003d miníý \u003d í746; 772; ý \u003d 746 p.
The critical duration of the fire is due to the occurrence of the maximum permissible temperature in the room.
Necessary time evacuation of people from warehouse:
tNV \u003d 0.8 * TKR / 60 \u003d 0.8 * 746/60 \u003d 9.94 min.
Make a conclusion about the sufficiency / failure of the evacuation of the calculation.
Output: compare the necessary evacuation time obtained by various methods, and, if necessary, explain differences in the results.
. Calculation of the dynamics of OFP for the level of the working area. Analysis of the situation on a fire at the time of 11 minutes
The level of the working area according to GOST 12.1.004-91 "Fire safety. General requirements "is taken equal to 1.7 meters.
The relationship between the local and medium-sharing values \u200b\u200bof the Office at the height of the room has the following form:
(OFP? OFPO) \u003d (OFP? OFPO) · Z,
where is the OFP? local (threshold) value OFP;
OFFO? initial IPP value;
OFP? Medium sharing value of a hazardous factor;
Z? The dimensionless parameter calculated by the formula (see clause 4.2).
Table 3. Dynamics of the development of OFP at the working area level
Time, Mintm, OS, Mass%,
NP / M. , M. , mass% , mass% , kg / m 3M120,023.0000,000000064,00,000000000001,005171,000001,005171,970,0000,412,970,0000,1261,004161,0063,20,92,9920,0000,84,620,0000,003,0,620,0000,003791,201471,273422. 122,9790,0000064,620,000000,009271,196371,251524,22,95,90,000064,620,0000,0064,620,0000,0161,61,188661,243626,72,9280,00,064,620,00420,032861,0,0,032861,0,522. 8840,0000064,620,000420,053501,065531,639834,72,620,0,0,0,080,620,040,0,080,69,250,0,0,24393,64,620,100,0,11,620,001,11,7541,13,11,25,41,1,10,1,21,10,41,72,6410 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 working area level is 52.4 0C, which does not reach PDZ, equal to 70 0 FROM.
Visibility distance in the room has not changed and is
2.38 / 0.00042 \u003d 5666 m.
Oxygen concentration normally: 22,513 mass%.
Partial densities O2, CO and CO2 at the level of the working area are equal, respectively:
1,09948? 22,513 / 100 \u003d 0.247 kg / m3;
1,09948? 0.00211 / 100 \u003d 2.3 * 10-5 kg \u200b\u200b/ m3;
1,09948? 0,22328 / 100 \u003d 0.00245 kg / m3.
Thus, the calculations showed that the partial density of oxygen is above the PDZ, and toxic gases below.
Fig. 14. Scheme of gas exchange indoors at the time of 11 minutes
At 11 minutes of burning, gas exchange proceeds with the following indicators: the inflow 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 smoked heated gases from the room, the plane of equal pressure is at the level of 1.251 m, which is lower than the level of the working area.
Output: based on the results of the calculations, give a detailed characteristic of the operational situation at the time of the arrival of fire units, to propose measures to carry out a safe evacuation of people.
General withdrawal
Make a general conclusion for work, including:
a) a brief description of the object;
b) general characteristics The speakers of the OFP with the free development of the fire;
c) comparing the critical time of the PDZ on dangerous fire factors according to the calculations of the INTMODEL computer program and the method of determining the time from the beginning of the fire before blocking the evacuation paths as a result of the dissemination of dangerous fire factors according to Appendix No. 5 to the order of the Ministry of Emergency Situations of Russia of July 10, 2009 No. 404;
(d) Analysis of the triggering of fire detectors installed in the premises if necessary to replace them;
(e) Characteristics of the operational situation at the time of arrival of fire units, proposals for the safe evacuation of people;
(f) Conclusion about the feasibility and prospects for using computer programs to calculate the dynamics of OFP during a fire.
Literature
1.Thistev D.I. Forecasting hazardous factors of fire. Course of lectures / D.I. Terentyev, A.A. Subacheva, N.A. Tretyakova, N.M. Barbin // FGBOU VPO "Ural Institute of GPS Emergencies Ministry of Russia." - Ekaterinburg, 2012. - 182 p.
2.Kushmarov Yu.A. Forecasting OFP indoors: Tutorial / Yu.A. Nightmares / - M.: Academy of GPS Ministry of Internal Affairs of Russia, 2000. -118 p.
Federal Law of the Russian Federation of July 22, 2008 No. 123-FZ "Technical Regulations on Fire Safety Requirements".
The order of the Ministry of Emergency Situations of the Russian Federation of July 10, 2009 No. 404 (as amended on December 14, 2010) "On approval of the methodology for determining the calculated magnitude of fire risk in production facilities". - fire safety. - №8. - 2009. - p. 7-12.
Order of the Ministry of Emergency Situations of the Russian Federation of 30.06.2009 No. 382 (as amended on April 11, 2011) "On approval of the methodology for determining the calculated values \u200b\u200bof fire risk in buildings, structures and buildings of various classes of functional fire danger" - Fire safety number 3. - 2009. - p. 7-13.
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Ministry of the Russian Federation for Civil Defense, Emergency
Situations and elimination of natural disasters
Voronezh Institute of State Fire Services
Department of Applied Mathematics and Engineering Graphics
Training edition
Specialty 280705.65 - "Fire Safety"
Forecasting dangerous fire factors indoors
D.V. Russian
Voronezh 2013.
UDC 536.46 + 614.841
BBK 24.54 + 31.31 + 38.96
Published by decision of the Methodological Council of FGBOU VPO Voronezh Institute of GPS EMERCOM of Russia
Reviewers:
associate Professor of the Department of Equations in Partial Derivatives and Probability Theory,
candidate of Physical and Mathematical Sciences, Associate Professor A.S. Ryabenko (VSU);
associate Professor of the Department of Physics,
candidate of Physical and Mathematical Sciences A. B. Plaksitsky (VI GPS Ministry of Emergency Situations of Russia)
R83 Russians D.V.
Forecasting hazardous fire factors indoors. Workshop with options for tasks to perform course work on discipline
"Forecasting hazardous fire factors" for cadets and students of full-time education and listeners of the Faculty of absentee training.
Specialty 280705.65 - "Fire safety". D.V. Russians, S.A.
Donets [Voronezh Institute of GPS EMERCOM of Russia]. - Voronezh, 2013. - 83 p.
The workshop contains short theoretical information, examples of solving typical tasks, including using a personal computer, options for tasks and guidelines to perform a course (control) work.
Workshop is intended for cadets and full-time students and listeners of the Faculty of absentee training in the specialty
280705.65 - "Fire safety".
© Russian D.V., Donets S.A., 2013
© FGBOU VPO Voronezh Institute of GPS EMERCOM of Russia, 2013
Introduction
1.1 Basic concepts
1.2 Description of the integral mathematical model in the room
1.3 Description of the differential mathematical model of a fire indoor
1.4 Description of the zone mathematical model in the room
2. Calculation of the dynamics of dangerous fire factors indoors
2.1 Original data
2.2 Using an integral mathematical model
2.3 Determination of the critical duration of the fire and time of blocking the ways of evacuation
2.6 Using a zone mathematical model
3. Methodical instructions for the execution of the course (control) work
3.1 Goals and Tasks
3.2 Selection of the topic of course work and an individual task option
3.4.1 Original data
3.4.2 Description of integral and zone mathematical models of fire development
3.4.3 Calculation of the dynamics of dangerous fire factors indoors using an integral mathematical model
3.4.4 Determination of the critical duration of the fire and the time of blocking evacuation paths
3.4.5 Forecasting the situation on a fire by the time the arrival of the first extensions for extinguishing
3.4.6 Calculation of fire resistance of enclosing building structures, taking into account the parameters of a real fire
3.4.7 Calculation of the dynamics of dangerous fire factors indoors using a zone mathematical model
3.5 Currency Design Requirements (Control)
Literature
Appendix A.
Appendix B.
Introduction
This workshop is intended for cadets and second-year students, as well as listeners of the third year of the Faculty of absenteeism of the specialty 280705.65 "Fire safety" FGBOU VPO Voronezh Institute of GPS EMERCOM of Russia. Written in accordance with the Working Program at the rate "Forecasting of dangerous fire factors",
designed according to the requirements of the Federal State Educational Standard of Higher Professional Education.
The workshop contains theoretical material and detailed disassembled practical tasks To prepare and conduct practical classes in two topics: an integral mathematical model of a fire in the room, the zone mathematical model of a fire in the room.
Options are given and guidelines for performing a course work by cadets and students of the second course and test work by listeners of the third year of the Faculty of absentee learning.
Workshop is written at a high engineering level accessible to language perception. It can be used by studying for independent study of the relevant material, the implementation of the course and control work, as well as to prepare for a test for the discipline "Prediction of dangerous fire factors" in the fourth semester from cadets and full-time students, during the final session in the third year at the listeners Faculty of absentee learning.
In addition, the workshop should help students in those cases
when they were absent for any reason in class or did not have time to record something, as well as in cases where they did not have enough time to perceive the material during the classes.
1. Methods for predicting hazardous fire factors indoors
1.1. Basic concepts
Dangerous factor firethe factor is called, the impact of which leads to injury, poisoning or death of a person, as well as to material damage.
In accordance with Article 9 of the Federal Law No. 123-FZ "Technical Regulations on Fire Safety Requirements" of July 22, 2008, the dangerous factors of fire affecting people and property include:
1) flame and sparks;
2) thermal stream;
3) increased ambient temperature;
4) increased concentration of toxic combustion products and thermal decomposition;
5) reduced oxygen concentration;
6) reducing visibility in smoke.
The concomitant manifestations of dangerous factors of the fire include:
1) fragments, parts of collapsed buildings, structures, buildings, vehicle, technological installations, equipment, aggregates, products and other property;
2) radioactive and toxic substances and materials that have fallen into the environment of destroyed technological installations, equipment, aggregates, products and other property;
3) removal of high voltage to conductive parts of technological installations, equipment, aggregates, products and other property;
4) dangerous explosion factors that occurred due to a fire;
5) Impact of fire extinguishes.
In modern conditions, the development of economically optimal and effective fire-fighting events is unthinkable without a scientifically substantiated forecasting dynamics of dangerous factors of fire (OFP).
Forecasting OFP required:
2) when creating and improving signaling systems and automatic fire extinguishing systems;
3) when developing operational extinguishing plans (planning actions of combat units in a fire);
4) when evaluating the actual limits of fire resistance;
5) for many other purposes.
From scientific positions, dangerous fire factors are physical concepts and, therefore, each of them is represented in quantitatively one or more physical quantities. From these positions and consider the above-mentioned OFP.
The first dangerous factor is the flame and sparks. Flame - This is the visible part of the space (fiery zone), inside which the oxidation process proceeds
(combustion) and heat generation occurs, and toxic gaseous products are generated, and the oxygen is absorbed from the surrounding space. In addition, within the boundaries of this part of the space
(zones) a specific dispersed medium is formed, the specific optical properties of which are due to the processes of the scattering of the energy of light waves due to their repeated reflection from the smallest solid (and liquid)
particles. This process of forming a dispersed medium, worsening visibility, is customary to be called the smoke process.
In relation to the volume of the room, filled with gas, the flame zone can be viewed, on the one hand, as a "source" of thermal energy and toxic combustion products, as well as the smallest solid
(liquid) particles, due to which visibility worsens. On the other hand,
as "stock", which goes out oxygen from the room.
In connection with the foregoing, the content of the concept of "flame" is presented in quantitative relations with the following values:
1) characteristic dimensions of the fiery zone (fireplace), such as burning area (fire area)F r, m2;
2) the amount of combusting (oxidized) per unit of time of fuel material (GM) (speed of burnout),kg · s-1;
3) power of heat releaseQ pox; Q mail \u003d Q r n, where Q r n is heat of combustion, j · kg-1;
4) the number of time generated per unit in the flame zone of toxic gasesL i, kg · C-1, where L i is the amount of i -to toxic gas,
formed during combustion unit mass of um;
5) the amount of oxygen consumed in the burning zone L 1, kg · C-1, where
L 1 is the amount of oxygen required for combustion (oxidation) of a unit of mass of um;
6) the optical amount of smoke generated in the burning area D,
Never · m2 · C-1, where D is the smoke-forming ability of a fuel material,
Never · m2 · kg-1.
The second dangerous fire factor is a heat flux.
Third dangerous factor - increased ambient temperature. The temperature of the medium filling the room is the status parameter, it is indicatedT, if Kelvin dimension is used ort,
if the dimension of degrees Celsius is used.
The fourth dangerous factor is an increased concentration of toxic combustion products and thermal decomposition. This factor is quantitatively characterized by partial density (or concentration) of each toxic gas. The partial density of the components of the gas medium indoors is the status parameter. Denotesρ, dimension -
kg · m-3. The amount of partial densities of all components of the gas medium is equal
gas density. The concentration of toxic I -th gas is usually called the ratio of the partial density of this gas I to the gas density, i.e.
i i.
If you multiply the ratio of i 100 percent, then get the value
product concentrations in percent.
The fifth dangerous factor is a reduced oxygen concentration in the room. This factor is quantitatively characterized by the value of the partial density of oxygen1 or its ratio to the density of the gas environment in the room, i.e.
x 1 1.
The sixth dangerous fire factor is to reduce visibility in smoke . This factor is quantified representing a parameter called the optical concentration of smoke. This parameter is denoted by the letterµ , its dimension -
Never · M-1. (Sometimes the parameter μ is called the natural indicator of attenuation.) The distance of visibility in the smoke L view and optical concentration of smoke are related to a simple ratio.
The above values: the temperature of the medium, partial densities (concentrations) of toxic gases and oxygen, the optical density of smoke - are the parameters of the state of the medium filling the room when
fire. They characterize the properties of the gas environment indoors. Starting with the emergence of a fire, in the process of its development, these status parameters are continuously changed over time, i.e.
T F 1, 1 F 2, F 3, O 2 F 4.
The combination of these dependencies is the essence of the dynamics of the OFP.
When considering the impact of the OFP on people, the so-called maximum valid values \u200b\u200b(PDZ) of the state of the state of the medium in the residence area of \u200b\u200bthe people are used (working area). Maximum permissible oFP Received as a result of extensive medical and biological research, in the process of which the nature of the impact of the OFP on people depending on the values \u200b\u200bof their quantitative characteristics.
It should be emphasized that in conditions of fire there are simultaneous
the impact on the person of all OFP. As a result, the danger increases many times. The maximum permissible values \u200b\u200bof the OFP are indicated in GOST 12.1.004-91 and SP 11.13130.2009 (Table 1.1).
Table 1.1. Maximum allowable values \u200b\u200bof OFP
OFP, designation, dimension |
|
Temperature, T, ° C |
|
Partial density, kg · m-1: |
|
oxygen |
|
carbon oxide |
|
carbon dioxide |
|
hydrogen chloride |
|
cyanide hydrogen |
|
nitrogen oxides |
|
serovodorod. |
|
Optical density of smoke, μ, neglect |
2.38 / l PDV * |
Thermal flow, q, w / m2 |
|
* L PDV - maximum permissible visibility range, m.