CFD Analysis of a Hybrid Rocket Motor's Post-Combustion Chamber

The present work has the purpose of presenting the results of a Computational Fluid Dynamic Analysis of a Hybrid rocket engine. This work has been conducted in parallel with Lucia Squillari, who did the Transient Thermal analysis of the half end of the motor, some data are directly taken from her thesis. The report describes the path followed during the analysis and calculations: identify the goals, find motivations and main parameters needed, computational process, analysis of the results obtained. The first chapters explain the motivations behind the concept of a new market based on small-satellites and dedicated mini-launchers. After an initial description of propulsion systems, hybrid propulsion is introduced, enumerating advantages and disadvantages compared to liquid and solid propulsion. At this point HyImpulse is introduced. It is the Start-Up where this thesis work was made. HyImpulse main purpose is to develop a complete hybrid propelled mini launcher. A chapter is dedicated to the theory behind the CFD analysis: the description of the physical equations, the discretize process, the transition from the Navier-Stokes differential equations to a set of algebraic equations which can be solved by simulation software and the process needed to be followed after the model results. The software used for the simulation is Ansys Fluent, whose way of working is portrayed in the theory chapter together with the models used during the analysis to simulate the combustion process inside a hybrid engine. The first analysis performed is on the post-combustion chamber and nozzle of a 10 kN engine that is tested by HyImpulse. The purpose of this simulation is to validate a 3d model with an analytical equation for a following analysis. The subsequent step is the analysis of the combustion process of a small motor tested at thedlr for a experimental validation of combustion model and the Transient Thermal model created by Lucia in a composite structure. Once validated the models, a parametric analysis is performed on different possible configuration of mixer geometry. The mixer is placed in different position in the post-combustion chamber and the purpose of this work is to analyse how its geometry and position could affect the combustion efficiency of a hybrid engine.