Hot Surface Ignition

Undesirable hot surface ignition of flammable liquids is one of the hazards in ground and air transportation vehicles, which primarily occurs in the engine compartment. In order to evaluate the safety and sustainability of candidate replacement fuels with respect to hot surface ignition, a baseline low lead fuel (Avgas 100 LL) and four experimental unleaded aviation fuels recommended for reciprocating aviation engines were considered. In addition, hot surface ignition properties of the gas turbine fuels Jet-A, JP-8, and JP-5 were measured. A test apparatus capable of providing reproducible data was designed and fabricated to experimentally investigate the hot surface ignition characteristics. A uniform surface temperature stainless steel plate simulating the wall of a typical exhaust manifold of an aircraft engine was used as the hot surface. Temperature uniformity of ±5°C was achieved on the stainless steel plate by virtue of its being bolted to a copper plate in which five automatically controlled 1000 W electrical cartridge heaters were inserted. A programmable syringe pump was used to dispense ~25 μL fuel drops onto the hot surface. Testing was performed in a quiescent environment with the exception of a mild upward flow created by an exhaust fan aiding the buoyant plume created by the hot plate. Ignition and flame propagation events were recorded using visible and mid-infrared still and video imaging. The ignition and flame propagation events are transient and occur at randomly distributed locations on the hot surface. To characterize the ignition event statistically, the surface temperature leading to at least one ignition out of the number of drops and the surface temperature resulting in the ignition of all of the drops were recorded. The results of the experiment confirmed that the experimental variations in the drop size, drop velocity, plume characteristics, surface properties including temperature changes, and the nonlinear dependence of temperature of the chemical reaction rate lead to the probabilistic nature of the ignition event. The results of the experiment are of practical value in designing vehicular ignition and safety systems

A study of flame spread measurements of aviation fuels

The study of a fire spread has always been very challenging and complex subject. Several properties of fire such as its flame spread rate, burning rate and radiation feedback should be known prior to any fire extinguishment operation. In this study, the flame spread rates of different liquid fuels are investigated at different initial temperatures using a novel temperature controlled experimental apparatus. Flame spread rates and different flame spreading regimes have been measured and analyzed for the conventional fuel Jet-A and three other alternative aviation fuels based on the processes such as Fischer-Tropsch-S8 (FT-S8), synthetic iso-paraffin (SIP) and hydro-processed esters and fatty acids (HEFA). A propane torch was used as an ignition source for the tests below the flashpoint of the fuel and an Nd:YAG laser was used as an ignition source for the tests above flashpoint of the fuel. Sixteen k-type thermocouples are installed along the length of the pan at equal distances to measure transient liquid-phase and gas-phase temperatures. Three different cameras namely, a Phantom v7.1 black and white high-speed camera, a Canon low-speed color camera, and a FLIR SC6100 high-speed infrared camera were used for recording flame propagation, measurement and calculation of the flame spread rate for the test fuel. Experiments were conducted for a wide range of liquids’ initial fuel temperatures ranging from 25°-100°C for Jet-A, HEFA, FT-S8 based jet fuel and from 110-130°C for SIP based jet fuel. Flame spread rate for all fuels increased exponentially with increasing fuel’s initial temperature. Flame spread rate is as low as ~6 cm/sec for Jet-A, HEFA, FT-S8 for 25°C initial fuel temperature and goes to as high as 160 cm/sec for 80°C initial fuel temperature. For SIP based jet fuel, flame spread rate is ~160 cm/sec for initial fuel temperature of 128°C

A Study of Flame Spread Measurements of Aviation Fuels

The study of a fire spread has always been very challenging and complex subject. Several properties of fire such as its flame spread rate, burning rate and radiation feedback should be known prior to any fire extinguishment operation. In this study, the flame spread rates of different liquid fuels are investigated at different initial temperatures using a novel temperature controlled experimental apparatus. Flame spread rates and different flame spreading regimes have been measured and analyzed for the conventional fuel Jet-A and three other alternative aviation fuels based on the processes such as Fischer-Tropsch-S8 (FT-S8), synthetic iso-paraffin (SIP) and hydro-processed esters and fatty acids (HEFA). A propane torch was used as an ignition source for the tests below the flashpoint of the fuel and an Nd:YAG laser was used as an ignition source for the tests above flashpoint of the fuel. Sixteen k-type thermocouples are installed along the length of the pan at equal distances to measure transient liquid-phase and gas-phase temperatures. Three different cameras namely, a Phantom v7.1 black and white high-speed camera, a Canon low-speed color camera, and a FLIR SC6100 high-speed infrared camera were used for recording flame propagation, measurement and calculation of the flame spread rate for the test fuel. Experiments were conducted for a wide range of liquids’ initial fuel temperatures ranging from 25°–100°C for Jet-A, HEFA, FT-S8 based jet fuel and from 110–130°C for SIP based jet fuel. Flame spread rate for all fuels increased exponentially with increasing fuel’s initial temperature. Flame spread rate is as low as ~6 cm/sec for Jet-A, HEFA, FT-S8 for 25°C initial fuel temperature and goes to as high as 160 cm/sec for 80°C initial fuel temperature. For SIP based jet fuel, flame spread rate is ~160 cm/sec for initial fuel temperature of 128°C