Combustion Characteristics of Shear Coaxial Injectors with Different Recess Lengths Under Wide Operating Conditions

The advancement of space launch technologies necessitates engines with a broad thrust control range. This study examines the impact of injector recess length on combustion performance in shear coaxial injectors, crucial for liquid rocket engines using methane. This investigation explores how recess lengths (0 mm, 2.5 mm, and 5.0 mm) affect combustion under various conditions, including combustion chamber pressures (45–9 bar) and mixture ratios (2.72–4.08). The research distinguishes itself by assessing the nuanced effects of recess length on combustion efficiency, heat flux, and stability, aiming to optimize methane engines for reusable vehicles. Experimental findings indicate significant improvements in combustion efficiency and heat flux as recess length increases without chugging instability. This highlights the design's critical role in engine performance, underscoring shear coaxial injectors' potential for efficient, stable combustion over a wide thrust range. The study innovates by elucidating the recess length's impact in the uni-element thrust chamber on combustion, contributing to future optimized engine designs.