Computational fluid dynamics modeling of reacting flowfields in rocket engines.

摘要

The objectives of the present research are to improve design capabilities for low thrust rocket engines through understanding of the detailed mixing and combustion processes. A Computational Fluid Dynamic (CFD) technique is employed to model the flowfields within the combustor, nozzle and near-plume field. Detailed modeling of rocket engine flowfields requires the application of the complete Navier-Stokes equations coupled with species diffusion equations. Of particular interest is a small gaseous hydrogen-oxygen thruster which is considered as a coordinated part of an on-going experimental program at NASA LeRC. The numerical procedure is performed on both time-marching and time-accurate algorithms, using LU approximate factorization in time, and flux split upwinding differencing in space. The unsteady version of the numerical code is validated against the linear stability theory for a shear layer involving velocity differences, molecular weight differences and chemical heat release as well as experimental shear layer data. The steady version is validated by comparing with the physical measurements in the rocket engine. The emphasis in the research is focused on using numerical analysis to predict global rocket engine performance as well as detailed local flowfield characteristics. These include three-dimensional fuel jet injection, mixing, and combustion the shear layer dynamics between the fuel cooling film and the core gas the integrity and effectiveness of the coolant film and their impacts on engine performance. Comparisons with experimental data for both global engine performance and detailed local flowfields are discussed. The computational analyses can be used in a complementary fashion with the experimental program to refine and enhance the engine performance prediction capabilities.