GOX/Methane Combustion Efficiency of a Swirl Coaxial Injector

*† ‡ A swirl coaxial injector element has been examined as part of an ongoing program studying injectors for liquid rocket engines. The propellants used were gaseous oxygen and gaseous methane. For this injector, mixing efficiency was evaluated by measuring the combustion efficiency at three set characteristic chamber lengths. Operating conditions were based on a concept for a liquid oxygen and liquid methane lunar ascent engine. Tests were performed using a modular small-scale rocket engine, which allowed chamber lengths to be varied between 0.089, 0.178, and 0.279 m (3.5, 7, and 11 in). Chamber pressure ranged from 0.689MPa to 1.58 MPa (100 to 230 psia); mixture ratio was held constant at 3.0. By changing these parameters, the rocket engine performance was evaluated using the given propellants via efficiency of the characteristic velocity. Tests were fired for approximately two seconds allowing for steady state operation to be reached. Data comparisons have been made with a similar swirl coaxial injector element tests. This work is a continuation of previous injector studies and will provide comparative data for future injector concepts. Nomenclature c * = characteristic velocity CCD = charge-coupled device CFD = computational fluid dynamics ΔP = pressure drop across injector ΔT = combustion chamber temperature rise η c* = efficiency of characteristic velocity F = thrust