Pitot pressure and heat-transfer measurements in hydrazine thruster plumes

Abstract

Pitot pressure and heat-transfer measurements have been made in plumes of 0.5-N (conical nozzle), 2-N, and 5-N (contoured nozzles) monopropellant hydrazine thrusters. The main objectives are to check the DFVLR simple plume model and to determine reliable model input values for real thrusters. The methods used for the heattransfer measurements (applying a sphere probe), the recovery temperature determination, and the evaluation of the plume quantities relevant for plume impingement calculations are outlined. The Pitot pressure measurements showed the existence of shock disturbances in the near plume flowfield of the contoured nozzles. Stagnation temperatures between 900 and 1350 K were deduced from the measured recovery temperatures. The corresponding molecular weight range was found to be between 11 and 14.5 and the most reasonable mean effective ratio of specific heats to be K = 1.4 ±0.03 for the expansion from the stagnation chamber to the continuum plume flow. This value is proposed for simple plume model calculations. The model heat-transfer results agree well with the experiments.