Holistic Simulation of Rocket Engine Nozzle

Abstract

Methane-fueled rocket engines provide an attractive compromise between performance and engine complexity compared to engines utilizing other fuels such as kerosene or liquid hydrogen. For example, methane has a higher ISP than kerosene while also having a higher storage temperature and density than liquid hydrogen, along with excellent properties for regenerative cooling.

Computational fluid dynamics is an invaluable tool for designing methane-fueled engines, but simulating a rocket nozzle can be a challenge due to the wide range of spatial and temporal scales along with the large temperature gradients between the coolant and nozzle flows. A traditional simulation approach divides the flows across multiple simulations coupled through boundary conditions, requiring multiple simulations which highlights an area that can be improved.

This thesis aims to investigate the possibility of carrying out an aerothermal simulation of an entire nozzle extension, with a holistic approach accounting for both the coolant and flame, as well as the heat transfer between regions in a single simulation. The project also aimed to compare two commercial CFD code Ansys Fluent and STAR-CCM+ using three different cases: 1) a 2D geometry used to identify solver settings to reach convergence, 2) a methane validation against previous work, 3) and a 3D rocket nozzle with a cooling channel for proof of concept.

For the 2D geometry case it was concluded that both simulation tools can achieve a converged solution with similar results, with a small difference likely due to the implementations of turbulence models in the tools. The methane validation case showed a good alignment for both CFD tools against the experimental results validating the method used for simulating the methane. For the 3D rocket nozzle the previous trend continued, showcasing a close match in results between the codes and previous work.

The project reached its final goal of developing a method of acceptable accuracy. This becomes clear when comparing with previous work. Both codes were proven to be suitable for the use of such simulations, allowing for a choice based on user experience along with other factors that are beyond the scope of this project, such as cost.