Regression analysis of impulse characteristics shorted supersonic nozzle
Keywords:shortened supersonic nozzle, bell-shaped nozzle, pressure, impulse characteristic
When designing and testing rocket engines, an important problem is the choice of the contour of the supersonic part of the nozzle. Recently, with the development of rock-et and space technology, different contours of nozzles have appeared that meet new tasks, requirements for the density of the layout, the need to increase the momentum co-efficient, accounting for various operating conditions, etc. Therefore, the relevance of the work is determined by the need to choose the contour of the supersonic part of the nozzle to increase the impulse characteristics of the flow in the shortened nozzle. The goal of the work is to choose the optimal contour of a shortened nozzle with a bell-shaped nozzle, taking into account geometric and technological parameters. The regres-sion model of the supersonic flow in a shortened nozzle with a nozzle considered in the work was created on the basis of previously obtained simulation results in the ANSYS package. It has been found that the flow patterns in the nozzle are affected by the length of the inlet cone, the total length of the nozzle and the operating conditions of the noz-zle, i.e. inlet pressure and ambient pressure. The nature of the separation flow in the nozzle, and hence the momentum coefficient depends on the degree of expansion of the flow from the shortened nozzle, therefore it is necessary to identify the main geometric and technological parameters of the flows in the shortened nozzle with a bell-shaped tip and determine the dependence of the momentum coefficient on them. Data analysis was carried out on the basis of the STATGRAPHICS Plus program. The influence values of each adopted factor and their mutual influence on increasing the flow impulse charac-teristics in the shortened nozzle are obtained. Three-dimensional graphs of the depend-ence of the momentum coefficient on the geometric parameters, the pressure at the noz-zle inlet, and the pressure of the external environment were obtained. The formula for the dependence of the impulse coefficient on the length of the conical part, the total length of the nozzle, the pressure at the nozzle inlet and the pressure of the external space was determined. It was established that an increase in the pressure of the external space leads to an increase in the impulse characteristic at the average value of the pres-sure at the nozzle inlet. The built regression model allows you to choose the optimal contour of a shortened nozzle with a tip.
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