消防直升机灭火外文文献

Fire Safety Journal 43 2008 363 375 Aerial fi refi ghting against urban fi re Mock up house experiments of fi re suppression by helicopters Tadashi Konishia Hironori Kikugawaa Yusaku Iwatab Hiroshi Kosekib Kohei Sagaeb Akihiko Itoc Katsutoshi Katoa aDepartment of Mechanical Engineering Oita National College of Technology Maki 1666 Oita 870 0152 Japan bNational Research Institute of Fire and Disaster 4 35 3 Shindaiji Higashi Chofu Tokyo 182 8508 Japan cDepartment of Intelligent Machine and System Engineering Hirosaki University 3 Bunkyo cho Hirosaki Aomori 036 8561 Japan Received 8 February 2007 received in revised form 24 October 2007 accepted 25 October 2007 Available online 3 December 2007 Abstract The Great Hanshin Earthquake in 1995 claimed approximately 6400 lives The majority was killed in large fi res after the earthquake Roads were cut off and collapsed buildings blocked the access of fi re engines to fi re fi elds Water mains were broken and lack of water prevented fi refi ghting efforts If aerial fi refi ghting had been effectively applied many lives could have been saved In an effort to prevent similar disasters the National Research Institute of Fire and Disaster NRIFD in Japan conducted two large scale experiments in order to investigate advantages and disadvantages of aerial fi refi ghting against urban fi res by helicopters in Tokyo in 1996 and 1997 and in Hokkaido in 1999 A successive experiment which was conducted in Oita in 1999 was carried out more extensively and with the cooperation of the fi re department authorities of several local governments and the Japan Ministry of Defense Aerial fi refi ghting was conducted against burning mock up houses that simulated urban fi res This report provides useful data for making operation plans for fi re suppression by helicopters r 2007 Elsevier Ltd All rights reserved Keywords Aerial fi refi ghting Urban fi re Fire suppression Helicopter Operation planning 1 Introduction Aerial fi refi ghting against forest fi res is common practice throughout the world The US Department of Agriculture USDA Forest Service in particular has been improving technologies in this area 1 In Japan aerial fi refi ghting is carried out against forest fi res dozens of times a year 2 4 and has been increasing as many local governments have been deploying helicopters Aerial fi refi ghting has not been carried out against urban fi res in Japan because water dropping does not seem effective with the roof of a building serving as an extinction hindrance However we argue that in urban fi res after a great earthquake when large scale fi re damage is antici pated aerial fi refi ghting especially using helicopters is the only possible hope for fi re suppression because of the following reasons In Japanese large cities such as Tokyo and Osaka many wooden residential houses are built close to one another Damaged roads and collapsed houses may hinder or prevent the access of ground fi re engines to fi re fi elds Besides fi re hydrant systems may be destroyed and water supplies may run short After a great earthquake buildings ignite easily due to collapsed houses and combustibles scattered on roads and the danger of fi re spreading increases Several models for predicting the fi re behaviors and the suppression were previously presented 5 8 Therefore it may become necessary to dump water until danger of reignition disappears requiring a long time for fi re fi ghting and a great amount of water Considering the above there are two defects in aerial fi re fi ghting One is that aerial fi re fi ghting is limited to daytime operations as fl ights over the mountains and cities at night ARTICLE IN PRESS resaf 0379 7112 see front matter r 2007 Elsevier Ltd All rights reserved doi 10 1016 j fi resaf 2007 10 005 Corresponding author Tel 81975526921 fax 81975526975 E mail address konishi oita ct ac jp T Konishi are highly dangerous To prevent the fi re spreading it is obviously important to dump water onto the fi res as much and as early as possible during the limited daytime This leads to the other defect The water dump by helicopters is not always suffi cient to control large fi res since the Japanese fi re fi ghting helicopters operated by fi re depart ments of local governments can carry less than 1 5 tons of water and the amount of water that can be carried aloft is a critical issue Although many helicopters fl ying parallel can dump larger amount of water the possibility of collisions due to the frequent fl ights may increase substantially 9 10 Nevertheless if aerial fi refi ghting can inhibit fi re spread ing until a ground fi re brigade arrives at the fi re fi eld even though the fi re is not completely extinguished it can be judged that aerial fi refi ghting is effective In order for aerial fi refi ghting to be most effective accurate engineering data on the optimum water dump from helicopters to fi res is needed The fl ow patterns of the dropping water from helicopters and aircrafts are investigated in CFD simula tions 3 11 and by real aircraft tests and water supply 1 12 13 What is crucially important in determining the fi refi ghtingstrategies 12 14 15 are fl yingspeed the quantity of water and water release intervals National Research Institute of Fire and Disaster NRIFD in Japan conductedthreelarge scaleexperimentsinorderto investigate advantages and disadvantages of aerial fi re fi ghting using helicopters in Tokyo in 1996 and 1997 and in Hokkaido in 1999 16 18 This paper is a report of a series of experiments that were conducted in Oita in 1999 in cooperation with the fi re department authorities of Oita city government four prefecturalgovernmentsandtheJapanMinistryof Defense This experiment examined the possibility of aerial fi refi ghting in an urban area with combustibles scattered on the road and with roofs of houses damaged This extensive experiment which has provided detailed information about aerial fi refi ghting against urban fi res is the fi rst of its kind in the world as far as the author knows The data provided by this report will be very helpful in determining fi re fi ghting strategies using helicopters in emergent urban fi res 2 Experimental methods 2 1 Mock up houses We conducted two experiments one using mid size helicopters and the other using large helicopters In simulating urban fi res after an earthquake a group of mock up houses were assembled for both the experiments Fig 1 a shows a schematic illustration of the mock up houses used for the fi rst experiment The fi rst experiment fi eld which was prepared for aerial fi refi ghting by mid size helicopters consisted of fi ve wooden houses All the walls and columns were made of wood The large center house 7 2m long 7 2m wide and 1 8m high was built in the center of the experimental fi eld The other four houses were built 3m apart from the outer wall of the center house and their size was the same 7 2m long 7 2m wide and 0 5m high Only the center house had a roof and the others did not In order to imitate scrap wood that would be scattered on the road after an earthquake piles of wood were laid ARTICLE IN PRESS W 25 kg m2 W 25 kg m2 W 25 kg m2 W 25 kg m2 W 150 kg m2 A1 A3A4A2 A5 7 2 m 7 2 m3 m 7 2 m3 m W 25 kg m2 W 50 kg m2 1 8 m 0 9 m Top view Side view Wind direction N Ignition by methanol soaked cotton rags Mock up houses Lumber Mock up houses Wood trails Wood trails W 150 kg m2 W 150 kg m2 W 150 kg m2 W 150 kg m2 W 150 kg m2 B2 B5B4B6 B7 7 2 m 7 2 m3 m 7 2 m3 m W 25 kg m2W 50 kg m2 1 8 m Top view Side view N W 100 kg m2W 50 kg m2 B1B3 Lumber Mock up houses Mock up houses Wind direction Ignition by methanol soaked cotton rags Wood trailsWood trails Fig 1 Schematic illustration of mock up houses used for a the fi rst experiment and b the second experiment T Konishi et al Fire Safety Journal 43 2008 363 375364 between the houses which we called wood trails Also in order to imitate the houses struck by an earthquake the fl oors of the houses were covered with piles of scrap wood The fi re load of the center house and the surrounding houses were 150 and 25kg m2 respectively The fi re load of the wood trails was 25 and 50kg m2 Fig 1 b shows a schematic illustration of the mock up houses used for the second experiment The second experiment fi eld which was prepared for aerial fi refi ghting by large helicopters consisted of seven wooden houses The walls and columns of the houses were made of wood They were of the same size each measuring 7 2m long 7 2m wide and 1 8m high The houses were built 3m apart from each other and scrap wood was laid between the houses making wood trails All the houses had a roof and their fl oors were covered with piles of scrap wood The fi re load of the houses was 150kg m2and that of the wood trails were 25 and 50kg m2 In the fi rst experiment the center house that was marked by the illustration of fi re was ignited as shown in Fig 1 a In the second experiment four houses were ignited at the same time as shown in Fig 1 b For igniting them methanol soaked cotton rags laid on the scrap wood in the houses were used As to the weather conditions of the experiment days the wind speed of the fi rst experiment day was 1 5 2 5m s from north to northwest and the peak gust was about 4m s The atmosphericpressurewas1013hPa theatmospheric temperature was 181C and humidity was 79 The wind speed of the second experiment day was 8 5 11 0m s from north northwest and the peak gust was about 15 8m s The atmospheric pressure was 1016 5hPa the atmospheric temperature was 141C and the humidity was 52 2 2 Helicopters and helibuckets Several factors can affect the ground distribution pattern of water dispersion by aerial water drops These include drop height drop speed volume and fl ow rate of the liquid released wind speed and directions and pilot profi ciency As drop height and drop speed increases water coverage area increases and coverage level decreases Although the accuracy rate of water hits against fi re tend to increase the fi re suppression effect decreases if the coverage level is not suffi cient to retard the spread of fi re Knowing the characteristics of the ground pattern obtained from specifi c helicopters is an important component of proper applica tion Much useful data about water dispersal for aerial equipment is collated on the USDA Forest Service Wildland Fire Chemical Systems homepage 1 For the fi rst experiment three types of helicopters BK117C1 BK117B2 and SA365N1 belonging to the fi re department authorities of the local governments that cooperated in this experiment were used The former two helicopters BK117C1 BK117B2 can carry a 600 l heli bucket and the last one SA365N1 can carry a 540 l helibucket The fl ight height of these three helicopters ranged from 86 to 144ft 26 2 43 9m and the airspeed ranged from 0 knots hovering to 24 knots 44 4km h For the second experiment three large helicopters CH47J which are assigned to Japan Ministry of Defense were used The CH47J can carry a 6000 l Griffi th Big Dipper helibucket 1 We used this bucket with 5300l of water The fl ight height of CH47J ranged from 147 to 160ft 44 8 48 8m and the airspeed ranged from 0 knots hovering to 25 knots 46 3km h Our experiment involves not only quantifying ground patterns of drop water from mid size and large helicopters but also determining fi re suppression effects by dropping water over burning mock up houses thus making it possible to provide information required in making urban fi re suppression plans using helicopters The coverage area was determined by the photographs taken by six digital video cameras Sony DSR 300F that were installed on platforms at 2m high above the ground at the locations shown in Fig 2 The coverage level was calculated by dividing the volume of dropping water by the coverage area 2 3 Temperature measurements The fi re suppression effect by aerial fi refi ghting can be detected by temperature changes in the burning houses Twotemperaturemeasurementmethodsweretaken thermocouples point by point measurement for detecting penetration of drop water into the houses and infrared cameras area measurement for detecting overall tempera ture changes of the houses The thermocouples used were fl exible sheath K type 100m long heatproof temperature 8701C The center house of the fi rst experiment A3 as shown in Fig 1 a and that of the second experiment B5 as shown in Fig 1 b were installed with three thermocouples at height of 50 100 and 170cm from the ground The other four houses in the fi rst experiment A1 A2 A4 and A5 as shown in Fig 1 a and four houses in the second experiment B2 B4 B6 and B7 as shown in Fig 1 b were installed with two thermocouples at height of 50 and 100cm from the ground The confi gurations of thermo couples setup are shown in Figs 7 and 8 To prevent the wires from disconnecting by collapsing scrap wood piled up in the houses and to prevent short circuits by drop water penetrating into the thermocouples the thermocouples were installed in iron poles with an outside diameter of 40mm which were fi rmly fi xed at the center of each house The sheath sections of the thermo couples of over 100m were protected by aluminum tape from drop water Two infrared cameras Avionics Inc TVS600 with a detection wavelength of 7 13mm a minimum detection temperature of 0 1K and a scanning rate of 1 60s were used They were installed at two locations 80m away from the center house both in the fi rst and the second experiments as shown in Fig 2 Thermal emissivity of infraredcameraswassetto0 90 Theamountof ARTICLE IN PRESS T Konishi et al Fire Safety Journal 43 2008 363 375365 temperature drop temperature recovery time and recovery temperature by aerial fi refi ghting were analyzed from the house temperature changes measured by the two infrared cameras 3 Results and discussions 3 1 Determination of coverage area and level Twenty challenges of aerial fi refi ghting against the burning mock up houses were carried out in the fi rst experiment and fi ve challenges in the second experiment Fig 3 a and b are two of the photos from the fi rst and the second experiments respectively Three helicopters under the fi re department authorities of Oita and Nagasaki prefectures and Fukuoka City were used in the fi rst experiment The helicopter used for the 1st 3rd 5th 7th and 9th challenges was from Oita prefecture the one used for the 11th 13th 15th 17th and 19th was from Nagasaki prefecture the one used for the other challenges was from Fukuoka municipal government The coverage areas of dropping water of the fi rst experiment whichareshownbyencircledareasin Fig 4 a were analyzed by the video images taken by the six video cameras The locations of the video cameras are shown in Fig 2 The coverage level was calculated by dividing the mass of dropping water by the coverage area The information about fl ight height airspeed coverage area and coverage level are shown in Fig 4 a The hit probabilities to all the houses were 58 at 0 knots 31 at 5 knots 9 3km h and 35 between 16 and 24 knots 29 6 and 44 4km h The results of aerial fi refi ghting by the large helicopter under Japan Ministry of Defense are shown in Fig 4 b The hit probabilities to all the houses were 19 at 0 knots hovering 13 between 15 and 25 knots 27 7 and 46 3km h Fig 5 indicates that with the increase of the airspeed coverage area increases and coverage level deceases The correlations between airspeed and coverage area and coverage level are expressed in the following equations S1 46 6 15 8V 1 D1 7 60 0 348V 2 S2 151 1 28 8V 3 D2 33 6 1 23V 4 where S is the coverage area m2 D is the coverage level l m2 V is the airspeed knots and where subscripts mean 1 is the fi rst experiment and 2 is the second experiment Substituting Eq 1 into 2 and substituting Eq 3 into 4 produce the following relations D1 8 63 0 0219S1 5 D2 40 0 0 0426S2 6 Fig 5 also shows the coverage level changes of Bambi 324 gallon and Griffi th 1000 gallon buckets with the airspeed change 1 This data shows similar tendencies as the data weobtainedwiththe5300lbucketinthesecond experiment We must bear in mind that for suppressing urban fi res a larger coverage level is required than for wildfi res because drop water does not easily penetrate into buildings while in suppressing wildfi res which spread easily larger cover age area is required Fig 6 shows the relation between coverage area and coverage level expressed by Eqs 5 and 6 with the airspeed as parameters In making a suppression plan against an urban fi re by using helicopters required coverage area and coverage level can be obtained by determining helibucket volume and airspeed of helicopters For example in case of a burning area of 200m2 if the 600 l helibucket is used the coverage level 4 3l m2will be ARTICLE IN PRESS A1A3 A4 A2 A5B2B5 B4 B6 B7 B1 B3 150 m 150 m 80 m80 m 80 m80 m Digital video camera Digital video camera Digital video camera Infrared camera Digital video camera Digital video camera Fig 2 Positions of six digital video cameras and infrared cameras The video cameras were installed on platforms at 2m high above the ground T Konishi et al Fire Safety Journal 43 2008 363 375366 obtained at airspeed of 10 knots If the 5300 l helibucket is used under the same conditions the coverage level 31 5l m2will be obtained at airspeed of 2 knots From the close relation between coverage level and the amount of temperature drop temperature recovery time and recovery temperature as shown in Figs 5 and 10 fi re extinction ARTICLE IN PRESS Fig 3 Photos from a the fi rst and b the second experiments 1 117ft 16kt 2 11ft 12kt 3 105ft 17kt 4 92ft 14kt 5 113ft 15kt 386 m2 1 6L m2178 m2 3 0L m2339 m21 8L m2192 m22 8L m2374 m21 6L m2 252m2 2 1L m2339m2 1 8 m2207m2 2 6L m2374m2 1 6L m2122m2 4 4L m2 6 86ft 18kt 7 114ft 15kt 8 102ft 12kt 9 119ft 18kt 10 103ft 6kt 11 91ft6kt 12 109ft 10kt 13 96ft 5kt 14 104ft 11kt 15 128ft 12kt 164m2 3 7L m2146m2 3 7L m2146m2 4 1L m2129m2 4 2L m2306m2 2 0L m2 50m2 10 8L