A theoretical study of the performance of resistojet nozzles.
University of Southampton, Faculty of Engineering and Applied Science,
The theoretical development of four computer models of resistojet nozzle performance is reported. Five main energy loss processes are accounted for; these are (i) frozen chemical rate processes, (ii) finite rate vibrational relaxation, (iii) incomplete expansion, (iv) viscous flow and (v) radial flow.
The nozzle flow is assumed to be composed of an inviscid core and a viscous boundary layer, where the boundary layer is represented by the patching together of similar solutions of the laminar boundary layer equations. General similar boundary layer equations have been developed which include the radial dependences accounting for transverse curvature. Four simplified classes of similar equations are identified, and extensive solutions have been obtained for the Falkner-Skan equation and a modified Falkner-Skan equation which includes the effects of transverse curvature, over the range of pressure gradient parameter, g, from 0. to 10. Vibrational relaxation is modelled by using an approximate sudden freezing criterion.
Performance predictions are presented for H2, CH4, CO2 and NH3 for plenum temperatures extending from 300 to 3000°K and plenum pressures from 200 to 10 kNm-2. A wide variety of nozzle geometries is also considered. The results are compared with the predictions of the slender channel model of Rae and with experimental measurements.
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