Experimental investigation of the ignition characteristics of vaporized RP-3 kerosene in supersonic flow

Abstract

The ignition characteristics of vaporized RP-3 kerosene were experimentally investigated in a cavity-based Mach 2.52 scramjet combustor. The simulated flight condition was Ma 5.5 at 25 km, while the entrance had a stagnation temperature of 1486 K and a total pressure of 1.6 MPa. With high-speed photography and chamber pressure measurement, the effects of fuel temperature on ignition performance were studied under a lean fuel condition, and the mechanism of ignition failure during the fuel temperature increasing was investigated. The results showed that increasing the injection temperature could accelerate the atomization and evaporation processes of the fuel droplets, reduce the ignition delay time, and enhance combustion in the cavity. However, a critical point (about 567 K) was found in vaporized kerosene ignition. When the injection temperature approached this point, the phase of the kerosene jet transited sharply, and the penetration depth increased. It decreased the fuel-air equivalence ratio in the cavity, deteriorating the reaction environment and causing ignition failure. The blow-out process had a similar evolution at different injection temperatures. Flame in-cavity was repeatedly stretched and merged with dissipating heat, and eventually blown off near the bottom. The flame residence time was closely related to the discharge time of the spark plug.