Study on the Performance of Injector for a Small Methane Rocket-engine Manufactured by Laser Powder Bed Fusion (L-PBF)

This study evaluates the performance of injectors for a small methane rocket-engine additively manufactured by employing the Laser-Powder Bed Fusion (L-PBF) method through cold-flow and hot-fire tests.Results indicate that in shear-type injectors, surface roughness on the injector's inner wall induces irregular flow separation, leading to unstable spray patterns and consequently degrading spray and combustion performance.Conversely, swirl-type injectors suppress flow separation due to the angular momentum imparted to the incoming flow, forming a stable and uniform spray, thereby demonstrating improved combustion performance.Notably, the injector featuring a trapezoidal inlet geometry achieves higher characteristic velocity and combustion efficiency compared to the injectors with a diamond-shaped inlet geometry.