Transactions of Nanjing University of Aeronautics & Astronautics
Stagnation Pressure Effect on the Supersonic Two-Dimensional Plug Nozzle Design
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Abstract:
The aim of this work is to develop a new calculation program to study the stagnation pressure effect of the combustion chamber on the design of the supersonic two-dimensional plug nozzle giving a uniform and parallel flow at the exit section. The model is based on the use of the real gas（RG） approach. The co-volume and the intermolecular interaction effect are taken into account by the use of the Berthelot state equation. The molecular vibration effect is taken into account in our model to evaluate the behavior of the gas at high temperature. The stagnation pressure and the stagnation temperature are important parameters in our model. At the lip， the temperature and the density are given by the resolution of a two nonlinear algebraic equations， which are formulated by an integration of four complex functions. The resolution is made by a new， robust and a fast algorithm. The other parameters are determined by analytical relations. The flow expansion in the nozzle is of the Prandtl Meyer type. The nozzle contour determination is made by discretizing the expansion zone at the nozzle lip by several points. The Mach number， flow deviation， pressure， temperature and density parameters are determined after inversion of the two-variable Prandtl Meyer function. The integration of the functions presented in the calculation is made by the Gauss Legendre quadrature of order 30. The validation of the results is controlled numerically by the convergence of calculated critical sections ratio to that obtained by the theory， because the flow at the throat and the exit section is unidirectional. In this case， the nozzle contour and the flow parameters， like the mass of the nozzle， the length and the thrust coefficient converge automatically to the exact solution. Our new RG model is considered as a generalization to the two perfect gas （PG） and high temperature（HT） models. The two latter can make the design for low stagnation pressure， and do not give any information on the variation of the stagnation pressure. So if the latter is high， it is necessary to correct the results given by the PG and HT models by considering our developed RG model. The plug nozzle has better performances and design parameters compared to other existing nozzles like the minimum length nozzle（MLN）. The mass， the length and the thrust coefficient of our plug nozzle for the PG and HT models are corrected by the use of our developed RG model. The application is made for air.
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Clc Number:
V925
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