The aim of this work is to develop a calculation model based on the method of characteristics making it possible to study the effect of the stagnation pressure of the combustion chamber on the 2D and axisymmetric minimum length nozzle design giving a uniform and parallel flow at the exit section. The model is based on the use of the real gas approach. The co-volume and the intermolecular interaction effect are taken into account by the use of the Berthelot state equation. The effect of molecular vibration is considered in our model to evaluate the behaviour of gas at a high temperature. In this case, the stagnation pressure and the stagnation temperature are important parameters in our model. The resolution of the algebraic equations is done by the finite difference corrector predictor algorithm. The validation of the results is controlled by the convergence of the critical section ratios calculated numerically as obtained by the theory. The mass and the thrust are evaluated to improve the efficiency of the nozzle. The comparison is made with the high temperature and perfect gas models. The application is made for air.

When the stagnation temperature of a perfect gasincreases, the specific heats and their ratio do notremain constant and start to vary with thetemperature. The gas remains perfect; its stateequations remain valid, so it can be named ascalorifically imperfect gas. The aim of thisresearch is to develop the necessary thermodynamicand geometrical equations and to study thesupersonic flow at high temperature, lower than thedissociation threshold. The results are found by theresolution of nonlinear algebraic equations andintegration of complex analytical functions wherethe exact calculation is impossible. The dichotomymethod is used to solve the nonlinear equations andSimpson’s algorithm for the numerical integrationapplied. A condensation of the nodes is used. Thefunctions to be integrated have a high gradient atthe extremity of the interval of integration. Thecomparison is made with the calorifically perfectgas to determine the error. The application is madefor air in a supersonic nozzle.