Supersonic Combustion and Flame-Holding Characteristics of Pylon Injected Hydrogen in a Mach 2.4 High Enthalpy Flow

Abstract

This work investigates the structure of the reaction zones downstream of a pylon injecting hydrogen fuel into a Mach 2.4 high enthalpy flow, with the aim of characterizing the behavior and evolution of the expected vortical structures. The pylon injector incorporates expansion ramps that serve as vortex generators. Fuel is injected through a thin slit along the entire length of the base of the ramps. Tests were conducted in the Stanford University Expansion Tube Facility at the High Temperature Gasdynamics Laboratory. All the experiments were conducted at a stagnation enthalpy of 2.8MJ/kg, a static temperature of 1400K, a static pressure of 40kPa, and Mach number of 2.4. The total temperature of the injected hydrogen was 300K. The ignition and flame holding characteristics were investigated using schlieren, time-integrated OH* chemiluminescence, and instantaneous OH planar laser-induced fluorescence (OH PLIF) imaging. OH PLIF was applied to capture the evolution of the reactive vortical system in planes normal to the freestream flow direction at a distance of 1.8cm, 4.3cm, 7.6cm and 10.7cm from the fuel exit plane. Resulting images show the distribution of OH radicals in the plume; these images also show a peculiar geometric pattern in the plume shape, suggesting that the vortices generated by the pylon configuration, and the consequent vortex dynamics, played a dominant role in the mixing and combustion processes.