Effects of Pressure on Minimum Hot Surface Ignition Temperatures (MHSIT) in Hot Air Crossflows

摘要

Hot surface ignition of flammable liquids in ground and air transportation vehicles is a risk that must be mitigated. Hot surfaces are typically exposed to airflow, and leaking fuel, oil and hydraulic fluid heated by these surfaces may vaporize and mix. The minimum hot surface ignition temperature (MHSIT) of flammable liquids depends on several factors including leak type (spray or stream), liquid temperature, air temperature, velocity, and pressure. ASTM standardized methods for ignition are limited to stagnant and falling drops downward (autoignition) at atmospheric pressure (ASTM E659, ASTM D8211, and ASTM E1491) and at pressures from 2.1 to 20.7 MPa (ASTM G72). Past studies have shown that MHSIT decreases with increasing pressure, but the available databases lack results of extensive testing. Therefore, such data for pressures between 100 kPa to 250 kPa are missing or inadequate. A previously designed experimental apparatus was modified to produce the 100 kPa to 250 kPa air duct pressure levels representative of a typical turbofan engine. In this paper, the modifications over a relevant range of air duct pressures are discussed.