A feasibility study of using pintle injector as sole-throttling device for shallow throttling condition

Abstract

Feasibility of using the pintle injector as a sole-throttling device was tested with a focus on the acquisition of sufficient injector orifice areas for uniform liquid injection considering the maximum throttling ratio of 4 to 1. Cold flow tests using 95 wt% hydrogen peroxide were performed with a relatively long and a short variable-area continuous-radial orifice of an average surface roughness condition of 1.6 mu m to explore hydraulic and liquid injection characteristics of the sole-throttling concept device. The required orifice gap size in the long orifice case was always larger than that in the short orifice case based on the same throttling ratio owing to lowered discharge coefficients. The transition from the uniform annular sheet injection to injection of jets with the sheet was observed as the decreased orifice gap size reached approximately 0.2 mm in both cases. The liquid injection in the short orifice case was more uniform compared to the long orifice case in the jet-sheet injection region. The feasibility of attaining the uniform annular sheet injection for the shallow throttling level was discussed from the test results.