Page 434 - konishipaper

372
T.Konishietal./FireSafetyJournα143(208)363-375
a 25
20
15
10
5
O
b 600 50
U
O 10 20 30 40 C o v e r a g e l e v e l ( L / m 2 )
calculated temperature change brought about by fir・e- fightingbyamid-sizehelicopterat10knotsandatahit rate of 100%，and Fig. 1(d) shows that by a large helicopter under the same conditions. Ac cording to the calculation，ifthebucketof601isused，thefirewilbe extinguishedwithin2rninwithwaterreleaseintervalsof 1min，within9minwiththoseof3min，andwithin25min withthoseof5min.Whereas，ifthebucketof5301isused， thefirewilbeextinguishedwithin2minwithwaterrelease intervalsof1rnin，within6rninwiththoseof3minand within10minwiththoseof5rnin.Althoughthediference oftheextinguishingtimebybucketvolumeissmal，the dif ference of the coverage areas is large; it is 205 m 2 for a 6 0 0 1 b u c k e t a n d 4 3 9 m 2 f o r a 5 3 0 0 1 b u c k e t. F i g s . 1 2 ( a ) - ( f) showtherelationbetwentheextinguishingtimeandthe releaseintervalsforthebucketvolumeof60and5301 withairspedasparameters.Sincecoveragelevelbecomes smalwiththeincreaseofairsped，theextinguishingtime tendstoincrease.Theextinguishingtimewascalculatedby multiplyingthecoveragelevelandthehitprobabilitytothe house(100%，50%and25%).Intheactualexperiment，the rnid-sizehelicoptersoperatedatreleaseintervalsofabout 3min，andthelargehelicopteroperatedatreleaseintervals ofabout 6min.The average hit probability to al the housesbyamid-sizehelicopterwas31% at5knots (9.3km/h)，andthatbyalargehelicopterwas13%betwen 15and25knots(27.7and46.3km/h).Inourexperiments， thefireofthehouseA3wasextinguishedwithinabout2h by20firefightingatacks.ThefireofthehouseB4was nearlyextinguishedwithinabout40rninbyfivefirefighting atacks，butitstartedburningagainandthetemperature recoveredagaintothatbeforewaterdropinginabout 30min.Inoursimulation，theextinguishingtimebyamid- sizehelicopterisabout2hat25%ofhitprobability，at5 knots，and at release interval of 3min as shown in Fig.12(c).Usingalargehelicopter，theextinguishingtime ispredictedtobeabout3.5hatthehitprobabilityof25%， at20knots，andatreleaseintervalof6rninasshownin Fig. 12(f). The results of the simulation are in clear agrementwiththeexperimentbythemid-sizehelicopters. However，inthefirefightingbythelargehelicoptersthefire wasnotextinguishedbyfivefirefightingatacks，therefore， comparison betwe en the simulation and the experiment couldn
4.Conclusions
Weconductedtwoseriesofexperimentsoffiresupres- sionefectsbyaerialfirefightingagainsturbanfiresusing mock-uphousesbyactual lyset tingthemonfire.Inthefirst experiment，mid-sizehelicopters(BK117C1，BK117B2，and
し 400 0.
O H て3
ど 30 2
E吋L司 200
(1) ト
10 O
C 120
~ 10 、-'
U 】 国
80
〉、
H
(1)
〉 。
O
10 20 30 40 Coveragelevel(Llm2)
与司
にJ 60 (1)
H
(1)
ら4
三回 40 与司
乱』
仏
E 20
(1)
ト
O
O 10 20 30 40
Coveragelevel(Llm2)
Fig.10. (a)Thetimeconstantτ，(b)thetemperaturedropd.Tand(c)the
temperaturerecoveryfactorRinrelationtocoveragelevel，respectively.
volumeandairsped，coverageareaandcoveragelevelare decided，as shown in Fig. 5. Water drop intervals for firefightingdependonfedwatercapacityorthenumberof helicopters available.Fig. 1 1(a)-(f) show simulated tem- peraturechangesofaburninghouse，basedonthedata fromourexperimentofFigs.5and10，underthefolowing conditions: the initial temperature at 10oC; the hit probability to the house at 100%，50% and 25%; and waterreleaseintervalsof1，3and5rnin.Fig.l1(a)shows
( ・ 5 5 ) 】 S H 凶ロ o u u g 戸