Materials: Thermal / Acoustic Insulation: Fuselage Burnthrough
Burnthrough Test Method
The laboratory scale test for determining the burnthrough resistance of thermal acoustic insulation blankets was developed using a modified gun-type oil burner. The burner produces a large, fuel-rich flame to simulate an open pooled fuel fire. The temperature of the flame is approximately 1900oF, with an accompanying heat flux of 16 Btu/ft2 sec. An equivalent burner was developed by the FAA Technical Center, the NexGen burner, that provides identical performance to the Park DPL 3400. The plans can be found under the NexGen burner section.
Sample Holder Frame
The sample holder used in the insulation burnthrough test is designed to mimic the typical installation of aircraft blankets behind the fuselage skin. This includes vertical formers, and several horizontal stringers. All members are comprised of steel to allow for repeat testing. Two heat flux transducers with a range of 0-5 BTU/ft2*s are mounted to the back of the frame.
Figure - Sample holder frame with heat flux transducers.
The size and intensity of the burner flame was extrapolated from measurements of temperature and heat flux in full-scale testing. It is necessary to regularly measure the temperature and heat flux of the burner flame in order to be assured the burner is functioning properly. For standardization purposes, all burners are measured with specified calibration devices following a detailed procedure.
Figure - Oil burner calibration, thermocouple rake on the left and heat flux transducer on the right.
Seven 1/8” (3.2 mm) thick ceramic packed, metal sheathed, Type-K (chromel-alumel) grounded junction thermocouples with a nominal 24 American Wire Gauge (AWG) size conductor are used to measure the flame temperature at a location 1” above the cone centerline, and 4” from the cone exit plane. After a two minute warm-up and 1 minute soak time, a 30 second average is taken on each thermocouple, and the temperatures must be 1900°F ±100°F.
Figure - K-type thermocouple.
Flame Heat Flux
Heat flux is measured with a total heat flux, foil type Gardon gauge calorimeter with an appropriate calibration range of 0-20 BTU/ft2*s (0-22.7 W/cm2), accurate to ±3% of the indicated reading. The heat flux is measured 1” above the burner cone centerline, and 4” from the cone exit plane. The calorimeter is soaked in the flame for 1 minute following a two-minute warm-up , and then a 30 second average heat flux reading is measured. The measured heat flux must be 16 BTU/ft2*s ±0.8 BTU/ft2*s.
Figure - Heat flux transducer.