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 H 2 . 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 the LOX=H 2 injector design can be transferred to LOX=CH 4 injection. The liquid oxygen has been atomized in shear coaxial atomizers, and the sprays and flames have been investigated by visualization methods such as 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=H 2 -and LOX=CH 4 -spray combustion are compared, and 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 the Weber number and the momentum flux ratio. The flame stabilization process has shown a strong influence on the atomization and flame characteristics.

Ignition of a gaseous methane/oxygen coaxial jet

“…Previous studies have shown that for higher chamber pressures, methane/oxygen §ames stabilize attached to the injector [4,7]. For lower pressures, the anchoring of the methane §ame seems to be much more dependent on injection parameters [3,5,8].…”

“…While with hydrogen fuel, the §ame anchors properly at the injector lips in most cases [3 6], the use of methane fuel induces di¨erences in §ame stabilization. The §ame behavior appears to be highly dependent on injection and combustion chamber conditions: for supercritical injected propellants, the LOX/CH 4 §ame stabilizes near the injector [4,7]; however, for subcritical condition, the methane §ame can stabilize either anchored or detached [3,5,8]. Even though the laminar §ame velocity for methane oxygen mixture is about a factor of 2.7 lower than that for hydrogen oxygen mixture [9], the reasons explaining the §ame behavior di¨erence are up to now not clear and further investigations are still going on to better understand the mechanisms of methane §ame stabilization.…”

“…The precedent experimental investigation on ignition of a gaseous H 2 /O 2 coaxial jet [10,11] has already been computed with CFD tools by several groups [12,13], thus demonstrating the interest to such experimental studies. Former studies have also been addressed to the investigation of liquid methane/oxygen ignition phenomena and §ame stabilization [3,5,14].…”

Application and Comparison of Different Combustion Models of High Pressure LOX/CH4 Jet Flames

“…In the cited work, injection is studied for different chamber pressures (in the range 0.1-7 MPa) and under sub-critical and trans-critical conditions; more recently, attention was given also to Methane/Liquid-Oxygen (LO x ) combustion as in [9]. Some works refer to methane combustion in diffusive burners characterized by a too low or high environmental pressure [9,10] or in premixed burners [11].…”

Cryogenic oxygen jet response to transverse acoustic excitation with the first transverse and the first combined longitudinal-transverse modes

“…A measure of this penetration distance is often taken as the axial length of the intact part of the LOx core, from injection to the ¦rst complete break in the core. Woodward et al [12], Yang et al [13], and Locke et al [14], for example, have made systematic measurements of the intact core length in lab-scale, shear-coaxial, single-injector combustors burning LOx/H 2 .…”