Experimental study of nonequilibrium expanding flows

An experimental study of nonequilibrium expanding flows has been carried out by measuring the static pressure at several axial locations in a 30° included angle conical nozzle attached to the reflected end of a combustion driven shock tube. In the axial survey, measurements were made at locations corresponding to geometric area ratios of from 36 to 576. Reservoir stagnation conditions were: 1000 psia, 1350°K; 450 psia, 4000°K; and 250 psia, 7000°K. The test gases used in this study were dry room air, extra-dry analyzed air, and a high-purity mixture of 80% nitrogen and 20% oxygen. The data reduction procedures that have been employed in this study are discussed. The methods for treating effects due to boundary-layer growth both on the nozzle walls and on the static-pressure probe, static-pressure probe size, flow gradients in the nozzle, etc., are outlined. It has been found that corrections for these effects are necessary to interpret properly static-pressure data. The apparent disagreement between previous experimental investigations and theoretical analyses is traceable in a large measure to these corrections. The measurements are compared with results obtained using a one-dimensional analysis that incorporates a gas kinetic model based on the best available chemical data. It is shown that the experimental data are in good agreement with the theoretical results.