Inner Jet Spread Angles of Coaxial Jets from Subcritical to Supercritical Conditions with Preliminary Numerical Results

摘要

A study is performed to analyze the behavior of the inner jet spread angles in a coaxial jet flow configuration similar to those used in liquid rocket engines. These angles are measured from back-lit images. Data is presented for sub-, near-, and supercritical non-reactive N2 coaxial jets. In the subcritical regime, the effects of an externally-imposed transverse acoustic field are also analyzed. The acoustic field is generated using two piezo-sirens and driven at a frequency of 3.0 - 0.1 kHz. Pressure oscillations vary from 16 to 22 kPa, peak to peak, at the location of the jet with background pressure of 1.5 MPa. For all cases, by varying the inner and outer jet temperatures and mass flowrates, outer to inner jet velocity ratios from 0.25 to 23 and outer to inner jet momentum flux ratios (J) from 0.02 to 23 are achieved. In the case where no acoustic excitation is applied the angles for the near- and supercritical cases show more spread compared to their subcritical counterparts for 1.0.