CFD analysis and reduced order modelling of a clustered Aerospike Engine, in presence or not of retro-propulsion

In the last decade, we have witnessed an increasing interest in reusable launchers. The clustered aerospike engine (i.e., a cluster of thrusters, referred to as cells in the following, that feed an aerospike nozzle) is an appealing technology for this application, for at least two reasons. First, an aerospike nozzle allows for continuous altitude adaptation during the atmospheric phases of flight, avoiding issues related to over-expansion that limit the design of conventional nozzles. Second, each cell can be throttled or cut off independently, enabling differential throttling. These features can be exploited twice, during both the ascent and the landing phases. In this context, the needed ability to predict engine performance, with sufficient accuracy and low computational effort, is challenging, especially considering plume interaction during differential throttling or possible failure modes. In the present M.Sc. Thesis, included in the frame of a research collaboration between POLITO and TU-Dresden, I have implemented a procedure to generate a reduced-order model of an arbitrary clustered aerospike engine. This model is capable of predicting, with good accuracy, axial and lateral components of thrust in different configurations. A computational fluid dynamics (CFD) analysis has been carried out, considering a 28-cells aerospike engine at two different operating points, with and without the presence of retro-propulsion. Different simulations were performed using Ansys Fluent in a cold flow configuration, considering only two active cells, aiming for a good compromise between accuracy and computational time. The interaction of plumes originating from cells at a certain angular distance has been evaluated by defining proper interaction coefficients. Subsequently, a reduced-order model has been proposed and tested on another database of simulations from both symmetrical and non-symmetrical configurations. Furthermore, a comparison between the results obtained with retro-propulsion and normal operating conditions has been conducted to investigate the reduced-order model’s performance and highlight potential differences in the interaction coefficients and plume behavior. This work lays the groundwork for future applications, where the database used can be improved by including experimental data when available.