Impact of Modeling Fidelity on Rocket Engine Performance Parameters

摘要

The overall objective of this research is to establish a design methodology for gas/gas injectors. This paper, however, focuses on a computational methodology to efficiently, accurately, and robustly obtain high- fidelity solutions of combusting rocket engine flows to gain a knowledge and understanding of their features. To that end, simulations of a single-element, shear-coaxial, H2/O2 engine are being performed to characterize its flowfield and to validate the CFD++ flow solver for this class of problems. previous work has focused on obtaining solutions on a grid three to four times finer than those reported by other researchers and resolving numerical issues that reduce the computational efficiency of this inherently unsteady flow. Comparisons of two-dimensional and three-dimensional steady and averaged time-accurate solutions have also shown that a steady solution may not provide an accurate depiction of the combusting flow field over time. Other simulations have shown that flow features unique to an experimental configuration, such as a nitrogen curtain purge used to cool the optical access, can influence both the experimental and computational results. Figure 2 shows that when the nitrogen curtain purge present in the experiment is modeled, the predicted hydrogen profile is more consistent with the experimental data. This is due to the fact that when the nitrogen is present, the hydrogen is unable to radially diffuse to the engine walls as quickly as when the nitrogen is absent. It is clear that the nitrogen has had an influence on the experimental data and both the experimenter and the modeler should take care when interpreting their results. The converging section of the nozzle and the throat were omitted in these previous studies while numerical issues associated with the calculations were resolved and because the region of interest was far upstream of the outlet.