Throat Flow Modelling of Expansion Deflection Nozzles

From The Space Library

Author - N.V. Taylor et al

Co-Author(s) - N. V. Taylor; C. M. Hempsell

JBIS Volume # - 57

Page # - 242-250

Year - 2004

Keywords - Rocket nozzles, expansion deflection nozzles, flow modelling

JBIS Reference Code # - 2004.57.242

Number of Pages - 9

[edit] Abstract

Modelling of the supersonic flow within a rocket nozzle of both conventional and expansion deflection (ED) design is well handled by Method of Characteristics based algorithms. This approach provides both a predic- tion of the flowfield, and allows efficient optimisation of nozzle shape with respect to length. However, the Method of Characteristics requires a solution of the transonic flow through the nozzle throat to provide initial conditions, and the accuracy of the description of the transonic flow will clearly affect the overall accuracy of the complete nozzle flow calculation. However, it is relatively simple to show that conventional analytical methods for this process break down when applied to the more complex throat geometry of ED nozzles. This requires the use of a time marching solution method, which allows the analysis of the flow within this region even on such advanced configurations. This paper demonstrates this capability, outlines a general method for ED nozzle throat geometric definition, and examines the effect of various throat parameters on the permissible range of ED contours. It is found that the design of length optimised ED nozzles is highly sensitive to small changes in these parameters, and hence they must be selected with care.

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