The Effect of Exit Velocity on the Infrared Radiation Intensity of an Exhaust Plume.

Abstract : This report describes the results of a study of the relationship between the exhaust gas velocity and the infrared radiation emitted in the 3 to 5 micrometer band from the exhaust plume of a small rocket engine. The experimental results indicate that, for the cases of both sonic and supersonic exit nozzles, the variation in exit gas velocity has very little effect on the infrared figure of merit under static ambient conditions simulating altitude. The data also show that there is no significant correlation between thrust and infrared figure of merit. In order to make these observations, oxidizer to fuel ratios (O/F) had to be maintained to better than 5% accuracy. Otherwise, the previously described effect of O/F ratio variation is so pronounced as to completely mask the small variations due to exit gas velocity.