Dominant parameter for pressure recovery performance of constant-area mixing tubes of ejector jets

A new variable termed the ejector drive parameter was proposed as a dominant parameter of the pressure recovery ratio of constant-area mixing tubes. It was derived from the one-dimensional analysis of a zero-secondary flow mode. This parameter represented the strength of the normal shock wave generated in the rocket exhaust that is spreading to the entire cross section of mixing tubes under the zero-secondary-flow condition. Parametric studies were carried out for investigating the pressure recovery ratios of the constant-area mixing tubes, and the analytical results were plotted against the ejector drive parameter or several other parameters. It was determined that the influences of each parameter on the pressure recovery ratios were minimized by using the ejector drive parameter. In order to validate the results of the parametric studies, cold flow experiments were conducted by using supersonic-subsonic ejectors with cylindrical or rectangular constant-area mixing tubes. The measured pressure recovery ratios were in good agreement with the pressures predicted by the one-dimensional analysis.