Applied Mechanics and Materials Online: 2012-05-14 ISSN: 1662-7482, Vols. 166-169, pp 2731-2734 doi:10.4028/www.scientific.net/amm.166-169.2731 2012 Trans Tech Publications, Switzerland Research on Mobile Water Spray Device Reducing the Temperature of Metro Fire Yu Li a and Lexia Dong b School of Civil & Safety Engineering, Dalian Jiaotong University, Dalian,Liaoning,116028, China a liyu381@yahoo.cn, b donglexia@126.com Keywords: Mobile Water Spray Device, Metro Fire, Emergency Rescue, Cooling. Abstract. Reducing the temperature is one of the key technologies in the metro fire emergency rescue, so it is the basic work to be done. Rapid and effective cooling can reduce the casualties caused by the metro fire. Water spray can quickly absorb a lot of heat for its large surface area. Water spray can quickly cool down the temperature of the metro fire and reduce the casualties caused by high temperature. Mobile water spray device is used in emergency rescue of the metro fire in this paper. Research on the mobile water spray device can do contribution to reduce casualties caused by metro fire. Introduction With the development of the city, traffic congestion has become a serious problem, the metro as an effective way to ease the pressure on urban traffic is large-scale construction. Fire has become an important problem along with the rapid development of the metro. The major metro fires of the world since the 1990s are shown in Table 1 [1, 2]. The metro fire has been paid for more and more attention. Table 1. World major fires in metro since 1990s Time Place Cause Casualty 1991 April 28,1995 October 28, 1995 June 11, 1996 November 11,2000 February 18, 2003 February 6, 2004 Zurich, Switzerland metro Daegu Subway Azerbaijan Baku Moscow Austrian Daegu Subway Moscow Short circuit of locomotive caused the train collided with another one Leaking gas caused explosion during the construction Aged and short circuit of locomotive caused on fire Train suddenly exploded in marching way Electric warming air conditioning overheating made fire Psychopath arson Explosion in rush hour 58 persons were seriously injured 103 persons died and 230 558 persons died and 269 4 persons died and 7 persons were injured 155 persons died and 18 198 persons died and 146 40 persons died and 120 From Table 1, it can be seen that metro fire often results in death or serious injury. Effective emergency rescue is particularly important because it can reduce casualties in metro fire. Foreign emergency rescue research is most about emergency plan on setting institutions, procedures, operation plans and so on. Domestic emergency rescue research is the general view on emergency rescue procedures and plan. Research on key techniques of metro fire emergency rescue is still in the blank stage. Three key techniques on emergency rescue in metro fire are get out through research. First, reducing temperature of fire field; second, adsorbing, purifying or converting the toxic gases; third, spraying oxygen to human location. Mobile water spray device is first used to reduce the temperature of metro fire. The mobile water spray device is an emergency rescue train which is installed in water spray device. Water spray is sprayed to fire field by the movement of train then the temperature of the fire field is reduced. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-07/03/16,00:20:02)
2732 Progress in Structures Water spray device Water spray is weighted cumulative distribution of water droplets flow less than 1000µm in the minimum working pressure defined by National Fire Protection Association (NFPA). It uses small water droplets into the flame region for fire fighting. The advantage of water spray device. Water spray device will change the water into small dripping which can be used to put out the fire. The superficial area of water droplet is much larger than jet-flow when they have the same volume. The water spray can be quickly boiled-off when it reaches the burning area, and then the temperature of the burning area can rapidly fall. The high density and quick evaporation can produce strength endothermic barrier to end the pass of radiant heat. The volume inflates when the water spray evaporates, 1kg water vapor can absorb 4504KJ heat, and it s superficial area is 1680 times larger than 1kg water, then the burning substance can be quenched because of oxygen lack. Research on Decreasing Temperature Technology of Emergency Rescue in Metro Fire [5] has calculate the heat of Metro Fire is 5.181 109J. The small dripping can completely vaporize and absorb the heat during fire fighting, according to the analysis, 1kg water can absorb 4504KJ heat quality from 5 (278K)to 712 (985K). According to energy conservation law, the releasing heat is the same as the absorbing. (1) 5.181 109=4.504 106m w, then m w =1150kg. When the fire is put off, it still needs to reduce the temperature of the fire field. Considering the enduring ability of human beings, 60 is decided as the last temperature in this paper. Similarly, reduce the temperature to 60 need 21280kg water. Then, putting off 5MW fire and reduce temperature to 60 need 5 water 22430kg. It needs 33645kg water consider of the factor of 1.5. According to the calculation, the system of water spray consumes much less water than the traditional water system. The feasibility of mobile water spray device. Mist droplets are sprayed to fire field by means of mobile water spray device through the movement of the rescue train. Spray area is large and the operation is simple. The device is placed in appropriate location of the metro network, when the fire starts it can be quickly drive to the scene of the fire to carry out rescue. It avoids the firefighters through the thick smoke to enter the scene of the fire, so rescue is the more secure and fast. Extinguishing 5MW metro fire requires 33645kg water, which is equivalent to 4 2.8 3 water tank. 33645kg water can be carried by water spray device. Mobile water spray device is simple and convenient for application. Mobile water spray device consists of water, water equipment, piping, rain valve, spray nozzle, emergency rescue vehicles and others. The technical parameters of the mobile water spray device It relies on one island platform of the Tianjin Metro in this paper. The width of the platform is 11m, length 120m of the effective site, the station a total length of 200m. Station main structure of the net width of 18.2m, the station structure size is 120m x 19.2m 8.13m. Pump head of the mobile water spray device. Working pressure of the spray nozzle should not be less than 0.35Mpa when putting out fire. If the working pressure of the spray nozzle is higher, the atomization of water will be better and the fire will be put out faster. The working pressure of most negative point is chosen 0.8Mpa. The pump head of the water spray in system: (2)
Applied Mechanics and Materials Vols. 166-169 2733 Where, h 1 is the actual working pressure of the most negative point, Mpa; h 2 is the sum of water head loss along the way of system pipe and local water head loss, Mpa; h 3 is elevation difference between the most negative point and system pipe entrance or the lowest water level of fire pool, m. The water head loss along the way h 4 : (4) where, dj is calculation internal diameter of the pipe, m, the value should be less 1mm than pipe diameter;υis water velocity in the pipe, m/s, v 5m/s. The local water head loss is 20% of the water head loss along the way. Because the height of the platform is 8.13m, taking into account the minimum water level of the tank and the maximum height of nozzle, so h 3 is taken 5m. Stand pipe and main pipe select DN100 pipes, branch pipe chooses DN65 pipe. The DN100 pipe s external diameter is 114.3mm, the wall-thickness 4mm and the internal diameter 96.3mm, so the calculation internal diameter of the pipe is 95.3mm. The calculation internal diameter of the DN65 pipe is 63.1mm. The velocity of DN65 take 5m/s, then the velocity of DN100 is 3.3m/s. The length of the main pipe is 20m, stand pipe length 5m and branch pipe length 6m. Calculate the water head loss along the way is 0.063MPa based on (3) (4) formulas. The local water head loss is 0.013MPa.By (2): H = 0.923MPa. The pump head high is selected 1MPa. The flow of the spray nozzle. Formula of calculating the number of spray nozzle: (5) Where, N is the number of spray nozzle; S is area of protected objects, m 2 ; W is spray strength of design, L / (min m 2 ); q is the flow of the spray nozzle, L/min. When used to extinguish the solid fire, the design of spray intensity 15L / (min m 2 ), the protection of area is 240 m 2, the number of nozzle 60, so the flow of the spray nozzle is 60 L / min according to the formula (5). Piping layout and spray nozzle layout of mobile water spray device. The distance between the spray nozzle should not exceed 1.4 times conical bottom radius of water mist of the spray nozzle, and the space between nozzle is set at 2m by analysis, and each location installs two nozzles, one spraying downward and another upward. Piping layout and spray nozzle layout are shown in Figure 2. (3) Figure 2 Piping layout and spray nozzle layout of mobile water spray device
2734 Progress in Structures Conclusions (1)The feasibility of cooling technology in the metro fire emergency rescue is proved in theory. (2) The advantages and feasibility of mobile water spray device is illustrated. (3) The technical parameters of the mobile water spray device are calculated and piping layout and spray nozzle layout are established based on one island platform of the Tianjin Metro. Acknowledgement This research was financially supported by Universities Science and Technology Program of Liaoning Province (L2010089). References [1] Lizhong YANG and Lan ZOU: Review on Tunnel and Subway Fire Researches. Construction and Design for Project. Vol. 11(2005), P.8-12 [2] Yanli DENG and Zhiguang TAN: Review on Subway Fire Researches. Security and Safety. Technology Magazine. Vol. 1(2008), P.6-8 [3] Wenyuan Jiang: Building Fire Fighting Design Manual (China building and industry press, 1997). [4]Yu Li: Building Fire Engineering (China University of Mining and Technology Press, Jiangsu, 2011). [5] Yu Li and Lexia Dong: Research on Decreasing Temperature Technology of Emergency Rescue in Metro Fire. Advanced Materials Research (2012), in press. [6] Lijun Yang: The Evaporation Heat Analysis of Water Spray Droplet in the Process of Extinguishing [7] Ministry of Construction. Ministry of Construction of the People's Republic of China,(1995).
Progress in Structures 10.4028/www.scientific.net/AMM.166-169 Research on Mobile Water Spray Device Reducing the Temperature of Metro Fire 10.4028/www.scientific.net/AMM.166-169.2731