In order to evaluate hot-jet simulation capabilities in cryogenic wind tunnel testing, simple theoretical calculations have been performed. The similarity parameters, isentropic flow properties, and normal shock relations were calculated for a variety of jet simulation techniques. The results were compared with those estimated for a full-scale flight condition. It has been shown that cryogenic wind tunnel testing provides an opportunity for the most accurate hot-jet simulation. By using compressed nitrogen gas at ambient or moderately elevated temperatures as a jet gas, almost all the relevant similarity parameters, including the jet temperature and velocity ratios and the Reynolds numbers, could be set to full-scale flight values. The only exception was the ratio of specific heats for jet flow. In an attempt to match the ratio of specific heats for the turbojet flow, gases other than pure nitrogen were considered. It was found that a nitrogen and methane mixture at moderately elevated temperatures behaved like the real combustion gas. With this mixture used as a jet gas, complete simulation of the full-scale turbojet exhaust became possible in cryogenic wind tunnels.
|Title of host publication||NASA Reference Publication|
|Publication status||Published - 1989 Jul 1|
ASJC Scopus subject areas
- Aerospace Engineering