Development-of-a-small-scale-burnthrough-test-equipment.pdf
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1、1 Development of a small scale burnthrough test equipment Jean-Franois Petit and Anne Mansuet Centre dEssais Aronautique de Toulouse 23, avenue Henri Guillaumet F-31056 Toulouse - France Abstract Fire entering into the cabin by burning through the fuselage has been observed in some accidents of comm
2、ercial aircraft. As a result, numerous research programs have been initiated by the CAA and FAA to study this issue. Full scale and medium scale tests have been conducted to investigate ways of improving the burnthrough resistance of aircraft fuselages. As a complement to full and medium scale tests
3、, the need for a small scale test has been identified to evaluate materials themselves. This paper describes the test equipment developed at the Centre dEssais Aronautique de Toulouse (CEAT). Developed in the same way as the cargo liner burnthrough test, it consists of a kerosene burner adjusted to
4、deliver a flame of 20 W/cm2 and 1100C and a 1m2 sample holder attached to a 1m3 smoke chamber. The first results and future developments will be presented. Introduction In survivable accidents of commercial aircraft, a significant number of deaths is caused by the effects of fire. The investigations
5、 conducted after the accident at Manchester Airport in 1985 show that the external fuel fire entered into the passenger cabin by burning through the fuselage skin(1). As a result, numerous studies have been initiated on this subject in the UK and in the US. Series of large scale(2) and medium scale(
6、3) tests, supported by the FAA and the CAA have been conducted to investigate the following issues : - the delay for an external fuel fire to enter the cabin through the fuselage - the most vulnerable areas of the fuselage - the fire entry paths into the cabin - the ways of improving the burnthrough
7、 resistance of fuselages. As a complement to full scale and medium scale tests, the need for a small scale test has been identified(4) to be used as a screening device for evaluating aircraft materials themselves. This small scale test equipment should be developed in the same way as the FAR 25 burn
8、through test method for cargo liners and should meet the following objectives : - good correlation with medium and full scale test results - easy to duplicate - low cost of use and fabrication - be applicable to a large range of materials and design features. In this paper, the small scale test equi
9、pment developed at the Centre dEssais Aronautique de Toulouse will be described. Then, first results and future considerations will be presented and discussed. General description of the small scale test rig The small scale test equipment developed at CEAT takes inspiration from the design of the te
10、st equipment used to demonstrate the compliance of cargo liners with the FAR 25 fire containment requirements. It basically consists of (see figure 1) : - the 2 gph oil burner modified to reach appropriate flame temperature and heat flux - a specimen holder - a smoke chamber 2 Figure 1 : Small scale
11、 burnthrough test rig Test articleOil burner Video camera Smoke chamber The detailed characteristics of each component are given below. Characteristics Fire source Considering existing data on large external fuel fires, as reported by H. Webster(2), the kerosene burner was modified to deliver a flam
12、e at 1150C and 200 kW/m2. To reach these levels of temperature and heat flux the following modifications were undertaken : - the existing nozzle was replaced with a 45 PLP 7 gph - the air flow rate was adjusted to 10 m/s, measured with a vane air velocity sensor (diameter 90mm) - the extension cone
13、used in other FAA fire test standards was maintained Flame calibration records are presented on figure 2. Time (s) 10 12 14 16 18 20 22 3 Time (s) 0 200 400 600 800 1000 1200 TH1 TH2 TH3 TH4 TH5 TH6 TH7 Figure 2 : flame calibration records Specimen holder The specimen is held in the vertical positio
14、n. The specimen holder consists of a 1m x 1m steel frame in which the test article is attached to a metallic inner frame. The specimen dimensions can be adjusted from 400mm x 400mm up to 1m x 1m. Smoke box Previous experiments conducted at CEAT(5) and other published test data showed that flame pene
15、tration was not the only potential threat to be considered. Smoke and toxic gases released before the fire entry into the cabin had to measured and data taken into account for the study of burnthrough. Thus, it was decided to equip the burnthrough test rig with a smoke box allowing smoke measurement
16、s and gas sampling. The smoke box has a volume of 1m3 and is fitted to the back side of the specimen holder. It is equipped with : - a smoke measurement device adapted from a NBS smoke chamber system - a sampling device for gas analysis - a video camera positioned behind a protection window to obser
17、ve the degradation on the back side of the specimen. A sketch of the smoke chamber is presented on figure 3. 4 1 m Smoke measurement device Figure 3 : 1m3 Smoke chamber Sampling probe Test procedure and definitions For each test, the oil burner flame is applied to the specimen after a warm-up period
18、 of 2 minutes. Burnthrough time is defined as the time when the oil burner flame itself penetrates the specimen. Tests on aluminum sheets In a first attempt, series of tests have been carried out on 2 millimeter thick aluminum sheets in order to compare measured burnthrough times with published test
19、s or accident data. Burnthrough of the aluminum skin itself was observed after 30 to 60 seconds as reported by H. Webster(2) during large external fuel fire tests on aircraft fuselages. At the FAA TC, full scale burnthrough tests on fuselage materials showed that the fire burnt through the aluminum
20、skin within 30 seconds(6). In the same way, medium scale tests conducted at Faverdale on a 2.0mm aluminum panel gave a burnthrough time of 43 seconds(6). Tests conducted on 2.0mm aluminum sheets using the small scale burnthrough test rig developed at CEAT showed burnthrough times ranging from 30 to
21、40 seconds. Other tests were conducted on different grades and thicknesses of aluminum. As shown on figure 4, burnthrough times measured on 2.5 and 4.0mm thick Al 2017A (close to 2024 alloy) correlates well with results obtained on Al 5053 sheets in 1.0, 2.0 and 5.0mm thick. As already observed at F
22、averdale(6), burnthrough time increases as material thickness increases. 5 Thickness (mm) 0 10 20 30 40 50 60 70 80 90 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 Al grade 5083 Al grade 2017A Figure 4 : Burnthrough time vs. Al thickness Tests on current insulation materials The performance of these tests
23、led us to define a specific configuration of the test specimen. It was decided to associate the thermal acoustical insulation material with a 2.0mm thick aluminum skin (see figure 5). The aluminum skin is attached to the specimen holder, on the face inside the smoke chamber, with four steel fixtures
24、. Each fixture is equipped with 2 pointed bolts to hold the insulation material. The dimensions of the aluminum skin are 600mm x 600mm and the overall dimensions of the test article are 700mm x 700mm including 50mm wide sealed edges. STEEL FRAME BURNER STEEL FIXTURE WITH POINTED BOLTS SPECIMEN : INS
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