Atomization and Flames in LOX/H2- and LOx/CH4- Spray Combustion

Abstract

Hydrogen is a widely used rocket fuel and methane is particularly of interest in Europe as a promising substitute for H2. Experimental investigation of cryogenic reactive coaxial sprays with oxygen as an oxidizer and hydrogen and methane as fuels is conducted to prove whether concepts from LOX/H2 injector design can be transferred to LOX/CH4 injection. The liquid oxygen has been atomized in shear co-axial atomizers, the sprays and the flames have been investigated by visualization methods like shadowgraphy and imaging of the flame emission. LOX-sprays are characterized for both propellants by the intact core lengths and droplet numbers and the combustion is analyzed in terms of the flame anchoring mechanism and the flame spreading angle. The results for LOX/H2- and LOX/CH4-spray combustion are compared, also the influence of the injection conditions of the propellants on atomization and spray flame is discussed. Significant differences of the sprays and flames have been observed for the two propellant combinations at similar injection conditions as defined by Weber number and momentum flux ratio. The flame stabilization process has shown a strong influence on the atomization and flame characteristics.