RU2702018C1 - Fire propagation limitation method in room - Google Patents

Abstract

FIELD: fire safety.

SUBSTANCE: invention relates to firefighting equipment and is intended to prevent the spread of fire between fire hazardous articles and objects using sprayed water, for example between cars in closed parking lots. Disclosed is fire propagation restriction method consisting in pulsed supply of sprayed water to combustion source from below from floor level in pulsating mode, wherein the interval between pulsed water pulses depends on the time of evaporation of the droplet flow of the sprayed water in the gas phase of the combustion source from the previous pulsation of the said flow. At conventional installation of sprinkler with location on top (ceiling) during its operation, reduction of heat flow from fire source occurs during movement of sprayed water flow towards heat flow. Said flows are intermixed with additional air inflow to form considerable area of turbulent mode between flows along vertical line. During installation of sprinkler with location at floor level and pulse water supply, during operation of sprinkler, heat flow movement from fire source and sprayed water flow takes place in pulse mode in one direction – upwards. As a result of movement of two flows in one direction, the area of turbulent mode shifts vertically upwards from the level of the floor, if compared with the traditional installation of the sprinkler at the top. At the same time water flow is reduced (approximately by two times) and its usage coefficient is considerably increased (water does not flow on the floor, but evaporates completely and participates in prevention of heat flow propagation between fire hazardous product and (or) objects and burning focus at return of water drops at movement of water flow downwards).

EFFECT: reduction of heat flow during fire extinguishing due to optimization of flow of fire extinguishing agent and saving of water due to pulsating mode of its supply.

1 cl, 3 tbl, 9 dwg

Description

The invention relates to fire fighting equipment and is intended to prevent the spread of fire between fire-hazardous products and objects using sprayed water, for example, between cars in closed parking lots.

A feature of fires in these structures is the possibility of intensive development of combustion in the initial stage and the accumulation of released heat by combustion products, fuel load and building structures.

Known deluge installation of water fire extinguishing (NF Bubyr and others. "Operation of fire automatics", M .: Stroyizdat, 1986, S. 136-145). The unit is designed to simultaneously extinguish a fire throughout the protected area.

The installation consists of a water feeder (pump station), a distribution pipeline, divided (using section shut-off valves) into deluge sections with deluge sprinklers installed on it and fire detection tools. If a fire is detected, for example, using a fire alarm system, the shutoff valve of the corresponding deluge section opens and water from the water source is supplied to the protected area.

The disadvantage of this installation is that the total water flow required to extinguish a fire with sprayed water reaches high values, so the use of this installation can create a problem of uninterrupted water supply with an existing water supply system at the facility (E.N. Ivanov, Fire protection of open installations . M., Chemistry, 1986, S. 83-95).

Numerous methods are known for automatic pulse fire extinguishing and devices for its implementation (JP Patent No. 4352972, А62С 37/36, publ. 08.12.1992; RU Patent No. 2046613, А62С 35/11 (1995.01), А62С 37/40 (1995.01), А62С 37/46 (1995.01), publ. 10/27/1995; Patent RU No. 2048825, А62С 3/08 (1995.01), publ. 11/27/1995; Patent RU №2104073, А62С 37/00 (1995.01), publ. 02/10/1998 ; Patent RU No. 2288015, A62C 3/00 (2006.01), A62C 37/00 (2006.01) publ. 11/27/2006).

In these technical solutions, the supply of the extinguishing agent is carried out in a pulsed mode from the barrel devices, and the direction of the jet of the extinguishing agent is adjusted in various ways.

However, the efficiency of spending fire extinguishing composition in these technical solutions is extremely low.

A common drawback of all the above methods and devices for automatic pulse fire extinguishing is the irretrievable loss of the cooling agent, which necessitates the provision of large reserves. Obviously, a huge amount will be required to protect extended objects of the cooling agent.

In (Collier PCR Car Parks-Fires Involving Modern Cars and Stacking System. BRANZ Study Report 255. BRANZ Ltd, Judgeford, New Zealand, 2011, 101 p .; Gewain RG Fire experience and fire tests in automobile parking structures. Fire Journal, July 1973, pp. 50-54; Murrell JV, Crowhurst D., Rock P. Experimental study of the thermal radiation attenuation of sprays from selected hydraulic nozzles, Halon Options Technical Working Conference 1995: Albuquerque USA, 1995, Building Research Establishment, 1995 , pp. 369-378; Pretrel H., Buchlin JM. Thermal radiative shielding by water spray curtain. Karman Institute for fluid Dynamics, pp. 432-440; Fire spread in car parks. BD 2552. Department for Communities and Local Government, London, December 2010, 111 p.) Describes experimental studies of the spread of fire between cars in enclosed spaces. According to the results obtained, it can be concluded that the main route for the spread of fire is the scenario:

- ignition of the passenger compartment with a large amount of fire load and the destruction of the glazing of a burning vehicle;

- the effect of heat flux on a neighboring car and the ignition of combustible materials that make up the exterior of a nearby car.

The main way to prevent the implementation of this scenario is to equip parking lots with fire extinguishing systems, which are the layout of water pipelines with sprinklers of finely sprayed water flowing from the ceiling of the room (from top to bottom).

To successfully extinguish a fire with sprayed water, the extinguishing method must meet the following basic requirements:

- cover immediately the entire combustion area;

- evenly distribute the flow of sprayed water over the irrigation area;

- provide the optimal intensity of the sprayed water per unit area of combustion;

- provide the optimal average droplet size (the required degree of dispersion).

A known method of extinguishing cars in closed parking lots, adopted for the prototype, which consists in the supply from the ceiling (top to bottom) with sprayed water (GV [Roberts GV An Experimental Investigation of Thermal Absorption by Water Sprays. Research Report Number 2/2001, ISBN 1-84082- 602-9, Home Office, Fire Research and Development Group, Horseferry House, Dean Ryle Street, London, 2001, 38 p.). In this work, similar studies were carried out on car extinguishing in parking lots, however, the distance between the radiating panel and the heat flux sensor between which the sprayed water was supplied was 1 m. These experiments prove that in real objects, where the distances between combustible substances are much smaller (for example, the distance between cars in closed parking lots is 0.5-0.9 m) is a significant drawback of existing fire extinguishing systems with atomized water, used to protect displacements for various purposes, including parking, and is characterized by low attenuation coefficient of thermal flux emitted hearth burning. As a result, in a real fire, even when fire extinguishing systems work, it often spreads to nearby objects and combustible materials of enclosing structures.

It is known (E.N. Ivanov, Fire protection of open installations. M., Chemistry, 1986, p. 84) that when calculating the water recovery system operating in the fire extinguishing mode, it is important to determine as accurately as possible the duration of the system in this mode, the frequency of occurrence fires, the likelihood of simultaneous fires, etc. The quality of the functioning of the system and its economic justification depend on the accuracy of the determination of these parameters.

When creating the present invention, it was taken into account that the possibilities for the efficiency of the consumption of atomized water are far from exhausted. In particular, the analysis of modern theoretical ideas about the processes of measuring the heat flux density when spraying water is supplied during fire fighting over the entire protected area in the premises showed a great prospect for the application of the claimed technical solution.

The objective of this technical solution is to increase the efficiency of the consumption of atomized water intended for fire fighting by optimizing the flow of the extinguishing agent and saving water due to the pulsating mode of its supply.

The essence of the proposed method lies in the fact that in the method of limiting the spread of fire in the room, which consists in the supply of sprayed water to the combustion zone, the sprayed water is pulsed from below the floor in pulsating mode, and the interval between the supplied pulsations of sprayed water depends on the time of evaporation of the droplet the flow of atomized water in the gas phase of the combustion zone from a previous pulsation of the named stream.

The technical effect of the proposed method is to reduce the heat flux during extinguishing a fire by optimizing the flow of the extinguishing agent and saving water due to the pulsating mode of its supply.

The work (AN Baratov. Combustion-Fire-Explosion-Safety. - M.: FGU VNIIPO EMERCOM of Russia, 2004, p. 219) noted the high efficiency of the use of sprayed water. In particular, it was found that the intensity of the decrease in the flame reaction rate and, accordingly, the efficiency of its suppression by increasing the activation energy of chemical interaction in the flame and by cooling it are equal. Moreover, flame cooling is even more promising than inhibition, since an increase in activation energy, in contrast to a decrease in temperature, is limited by the molecular strength of the reaction components.

Therefore, when extinguishing with sprayed water, it is necessary to constantly maintain the evaporation of a droplet stream of sprayed water in the gas phase of the combustion zone for intensive cooling of this combustion zone.

The pulsed water supply from below from the floor level in pulsating mode allows the turbulent mode region to be shifted upward from the floor level in comparison with the traditional sprinkler installation at the top.

Creating a break between the supplied pulses of sprayed water equal to the time for evaporation of the droplet stream of sprayed water in the gas phase of the combustion zone of the previous pulse of the named stream allows you to:

- reduce the consumption of water used to extinguish a fire in the room;

- significantly increase the coefficient of its use (water does not flow down the floor, but completely evaporates and is involved in preventing the spread of heat flow between the fire hazardous product and (or) objects and the burning area when water droplets return when the water stream moves down.

According to the authors of the invention, the characteristics given in the claims are necessary and sufficient to achieve the specified technical result, that is, they are essential.

Thus, the distinguishing features of the proposed technical solution are new and meet the condition of patentability "novelty."

When determining the conformity of the distinguishing features of the present invention with the patentability condition “inventive step”, the prior art and, in particular, known methods and devices related to technical solutions related to preventing the spread of fire between fire hazardous products and objects using sprayed water were analyzed.

A known method of extinguishing a fire and a device for its implementation (Patent RU No. 2421259, А62С 3/06 (2006.01), publ. 06/20/2011). The method consists in the fact that a group of fire extinguishing means supply pulsed interrupted compressed air to the storage areas for individual fire extinguishing equipment allocated on each floor of the fire hazardous facilities. The latter are made in the form of fire extinguishers-spray guns, which are supplied to groups of rooms and when used, they carry out pulsed explosive exhaust emissions that knock down tongues of flame. At the same time as air exhausts, fire-extinguishing water-droplet injections, repeated and short-term injections of powder clouds or air-mechanical foam are carried out, and when extinguishing objects and equipment that is energized, repeatedly-brief injections of a fire-extinguishing aerosol are carried out. The group fire extinguishing means of the device have devices for the production and distribution of explosive pulses of compressed air and hoses with valves for coupling with spray fire extinguishers, which allow to give pulse explosive exhausts of compressed air through their nozzles together with the injection of fire extinguishing clouds of water droplets, aerosol and air-mechanical foam.

The disadvantage of this method is that the supply of pulsed air flows can intensify the combustion of the fire load and thereby lead to an increase in the foci of combustion in the room, and not to knock down the flame.

Known knapsack installation of pulse fire extinguishing (Patent for utility model RU No. 89397, А62С 15/00 (2006.01), В05В 1/30 (2006.01), publ. 10.12.2012), in which the fire extinguishing operator can change the flow rate of the extinguishing liquid stream and receive jets with different spray patterns.

However, this installation is designed for local fire extinguishing in small and non-residential premises, and the parameters of the extinguishing liquid supplied with pulsed supply from a backpack installation depend on the experience of the fire extinguishing operator.

Analysis of other technical solutions showed that the known methods and devices do not solve the previously mentioned problems, solved by the claimed method.

Based on the foregoing, we can conclude that the claimed technical solution meets the criterion of "inventive step", and the invention itself is new.

The implementation of the technical solution inherent in the method of limiting the spread of fire in the room can be implemented as follows.

When implementing the proposed technical solution, the following information must be considered.

In accordance with the requirements of SP 5.13130.2009. Fire protection systems. Automatic fire alarm and fire extinguishing installations. Norms and design rules, S.S. 10-13, 16-17, 71-79 for extinguishing cars in garages and parking lots with a specific fire load of 181 to 1400 MJ / m ² , fire extinguishing parameters should be as follows:

- the irrigation intensity of the protected area, not less than from 0.12 to 0.18 l / s m ² ;

- flow rate, not less than 30 l / s;

- the minimum estimated area of irrigation sprinkler automatic fire extinguishing installation (AUP), not less than 120 m ² ;

- the duration of the water supply, not less than 60 minutes;

- the maximum distance between sprinkler sprinklers is 4 m (for sprinkler AUP, AUP with forced start, sprinkler-deluge AUP).

It should be noted that the requirements for distances between cars are determined only by the overall dimensions of the vehicles. In this connection, in normative documentation this condition is not considered from the point of view of preventing the development of a fire. In addition, when calculating the parameters of automatic fire extinguishing installations with sprayed water, the specifics of the location of vehicles in closed parking lots, as well as the effect of water droplets on the radiant heat flux, are not taken into account. At the same time, most of the water falls on the body of the atomic vehicle, and not in the burning cabin.

A drawback of the extinguishing method described above is that in case of fire and the automatic operation of the fire extinguishing system with sprayed water, there is an increase in the burning rate of the fire source, which is expressed in an increase in the flame height, and most importantly, in the very weak effect of the sprayed water on the heat flux during a fire.

To confirm the efficiency of the consumption of atomized water, designed to reduce the intensity of heat fluxes from the combustion zone by optimizing the flow of the extinguishing agent and saving water due to the pulsating mode of its supply, several series of tests were carried out.

The first series of experiments was performed in the normal mode without pulsed water supply in a pulsating mode.

The tests to extinguish a model combustion site simulating a burning car were performed on a setup presented in the experimental setup diagram (Fig. 1) to study the attenuation of the heat flux under the influence of sprayed water. Installation includes:

1 - cylinder with water; 2 - cylinder with propellant; 3 - gear; 4 - high pressure hoses; 5 - shutoff valve; 6 - pressure gauge; 7 - sprinkler; 8 - meter of heat flux density IPP-2; 9 - model fire center class 5B; 10 - protective shields; 11 - a metal ruler.

For the experiments, finely sprayed water sprinklers, type A and B, were used to extinguish fires in Group 2 rooms according to the degree of danger of fire development depending on their functional purpose and fire load of combustible materials (Appendix B SP 5.13130.2009. Fire protection systems. Installations automatic fire alarms and fire extinguishing. Standards and design rules).

The characteristics of the sprinklers (water flow and droplet diameter depending on pressure) were established experimentally.

In FIG. 2 shows the change in water flow rate of type A and B irrigators depending on pressure. With increasing pressure, the average flow rate of the sprinklers adopted for testing increases, however, the water flow rate through the sprinkler “A” (upper curve) exceeds the flow rate of the sprinkler “B” by an average of 4 times.

Analysis of the results of measurements of the average irrigation intensity of type A and B irrigators (Fig. 3) indicates that with an increase in pressure the irrigator “A” exhibits a decrease in intensity (upper curve), even if the average flow rate is increased. This fact is explained by an increase in the spray angle recorded during measurements. At sprinkler B there was no change in the spray angle, so the average irrigation intensity increases with increasing pressure.

The results of measuring the diameter of the droplets (Table 1) showed that the diameter of the droplets of the sprinkler “A” varies slightly depending on the pressure and averages 430 microns. On the contrary, the sprinkler "B" with an increase in pressure to 0.8 MPa, there was a decrease in the diameter of the droplets more than 4.5 times the diameter at a pressure of 0.2 MPa.

As a source of thermal radiation for the experiments, a model fire center of class 5B was used in accordance with GOST R 51057-2001 “Fire fighting equipment. Portable fire extinguishers. General technical requirements. Test Methods. "

The model hearth is a round baking sheet made of sheet steel with an inner diameter of 450 mm, with a wall thickness of 1.5 mm and a side height of 100 mm.

As a combustible material we used summer gasoline that meets the requirements of GOST R 51105-97 “Fuel for internal combustion engines. Unleaded gasoline. Specifications "AI-92 brand.

The conditions for the experiments to study the effect of atomized water on the heat flux when it is supplied from top to bottom (experiments No. 1 and 2) and from bottom to top (experiment No. 3) are presented in Table 2.

- 0,2 МПа;

- 0,4 МПа;

- 0,6 МПа;

- 0,8 МПа; фиг. 5 (ороситель Б): изменение плотности теплового потока под воздействием распыленной воды, подаваемой при различном давлении из оросителя Б:

- 0,2 МПа;

- 0,4 МПа;

- 0,6 МПа;

- 0,8 МПа. Незначительное ослабление теплового потока на 3,04% и 5,76% было зафиксировано при давлении 0,6 МПа у оросителя А и при 0,4 МПа у оросителя Б, соответственно. В остальных случаях было зафиксировано повышение значения плотности теплового потока при подаче воды.The results of measurements of the heat flux density when spraying water is supplied from top to bottom depending on pressure (0.2; 0.4; 0.6 and 0.8 MPa) are presented in FIG. 4 (sprinkler A): change in heat flux density under the influence of sprayed water supplied at different pressures from sprinkler A:

- 0.2 MPa;

- 0.4 MPa;

- 0.6 MPa;

- 0.8 MPa; FIG. 5 (sprinkler B): change in heat flux density under the influence of sprayed water supplied at different pressures from sprinkler B:

- 0.2 MPa;

- 0.4 MPa;

- 0.6 MPa;

- 0.8 MPa. A slight weakening of the heat flux by 3.04% and 5.76% was recorded at a pressure of 0.6 MPa for sprinkler A and at 0.4 MPa for sprinkler B, respectively. In other cases, an increase in the density of the heat flux during water supply was recorded.

An increase in the intensity of combustion and, as a consequence, an increase in the heat flux density is explained by the ingress of an additional air flow through the openings in the protective shields into the gasoline combustion zone, as well as by the fact that this air flow is also formed under the influence of the sprayed water flow, since the increase in the heat flux density was recorded during irrigation. An increase in the intensity of gasoline combustion can also be observed when water drops enter the combustion zone, but this was excluded by using protective shields in the experiments.

- направление движения капель воды;

- условное направление теплового потока, излучаемого нагретыми массами;

- направление движения воздушных масс, влияющих на интенсивность горения. При этом не происходит существенного снижения интенсивности теплового потока на рядом стоящие изделия, а воздушные потоки изделия направляются на очаг пожара.According to the results of the experiments, we can conclude that the work of the fire extinguishing system to attenuate the heat flux from the burning fire to a nearby product or object when the sprinklers are located on the ceiling of the room is ineffective (Fig. 7) the effect of sprayed water supplied from top to bottom on the burning rate of the car:

- the direction of movement of water droplets;

- the conditional direction of the heat flux emitted by heated masses;

- the direction of movement of air masses affecting the intensity of combustion. In this case, there is no significant decrease in the intensity of the heat flow to adjacent products, and the air flows of the product are directed to the fire.

- направление движения капель воды;

- условное направление теплового потока, излучаемого нагретыми массами;

- направление движения воздушных масс, влияющих на интенсивность горения.When changing the conditions of the experiments (see experiment conditions No. 3, table. 2), it was possible to achieve a significant decrease in the intensity of thermal radiation from the fire source (Fig. 8), the effect of sprayed water supplied from the bottom up on the burning rate of the car:

- the direction of movement of water droplets;

- the conditional direction of the heat flux emitted by heated masses;

- the direction of movement of air masses affecting the intensity of combustion.

Sprinklers were installed at the floor level of the room with the outlet up. The results of measurements of the heat flux density are presented in FIG. 6.

The most effective is the method of supplying sprayed water using B sprinklers: during its operation (hollow spray cone, spray angle of not more than 80 °), water droplets did not enter the combustion zone. As a result, a significant decrease in heat flux density was recorded:

- by 44.6% at a pressure of 0.4 MPa;

- 48.4% at a pressure of 0.6 MPa;

- 48.5% at a pressure of 0.8 MPa.

Thus, due to the location of the irrigator at the floor level, the effect of the heat flux from the burning car on neighboring vehicles is reduced by ~ 50% and most of the water flows directly into the car interior through the destroyed glazing, while the thermal effect on the surrounding products and objects is reduced, as well as the effect of combustion products on humans, increasing the time for safe evacuation of people.

The second series of experiments was carried out when water was supplied from the floor in a continuous and pulsed manner in a pulsating mode. With a pulsed water supply (water flow alternately for 5 s and interruption of its supply for 5 s), the effect of reducing the thermal effect on products and objects is due to the fact that in this mode of supply of sprayed water from the floor, not only drops of water flow are involved in the fire barrier , but also water fog, formed during a pulsed water supply, which evaporates within 5 s (the optimal pulsation period was established experimentally).

Thus, creating a break between the supplied pulses of sprayed water equal to the time for evaporation of the droplet stream of sprayed water in the gas phase of the combustion zone of the previous pulse of the named stream allows the turbulent mode to be shifted upward from the floor level in comparison with the traditional sprinkler installation at the top.

In FIG. Figure 9 presents data on the decrease in the intensity of the heat flow when spraying water is supplied from the floor with a continuous and pulsating water supply.

As can be seen, the values of the intensity of attenuation of the heat flux in both series of the experiment did not change.

Table 3 presents the results of measurements of the average consumption of consumed water when it is supplied from the floor in a continuous mode and in a pulsating mode (alternately, the water flow rate for 5 s and interruption of its supply for 5 s).

As follows from the table, the water flow rate for pulsed supply and achieving a decrease in heat flux by 50% from the combustion zone to the surface of the sample and was approximately two less than in the continuous water supply mode. At the same time, the coefficient of water use turned out to be close to 1 in comparison with the coefficient of its use in the case of non-pulse supply from the floor.

Consequently, the total water supply time is reduced by half and the flow rate is also halved, but the coefficient of water use approaches 1. At the same time, the efficiency of preventing the spread of heat flow remains unchanged, since the flow of droplets (fog) is sprayed during the termination of water supply water from above does not decrease, but returns, continuing to block the heat flow.

Industrial applicability of the claimed technical solution is as follows.

Currently produced in Russia and abroad, means to prevent the spread of fire between fire hazardous products and objects with the help of sprayed water make it possible to implement the claimed invention with little or no refinement of the structural elements and components of the produced automatic fire extinguishing installations.

The inventive method of limiting the spread of fire in a room is simple to operate and can improve the efficiency of the consumption of atomized water, designed to reduce the intensity of the heat flow from a burning product (for example, a car) by optimizing the flow of extinguishing agent (atomized water) and saving water due to the pulsating mode of its supply .

Claims (1)

The method of limiting the spread of fire in the room, which consists in the supply of sprayed water to the combustion zone, characterized in that the sprayed water is supplied by an automatic fire extinguishing installation pulsed from below the floor in pulsed mode through sprinklers with a hollow spray cone and a spray angle of not more than 80 °, and the duration of the supply of atomized water is chosen equal to 5 s, and the interval between the supplied pulsations is selected from the condition of complete evaporation of the droplet stream of atomized water in the gas phase of the source eniya from previous pulsation of said flow equal to 5 seconds.

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