Linear Aerospike Contour Design using Angelino’s Method and CFD Validation

• Autor(a) principal: Silva, João Pedro Cristóvão
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/13804
• topic: Aerospike Linear; Design de Contorno de Tubeira; Dinâmica dos Fluidos Computacional; Eupo (Estágio Único para Órbita); Tubeiras de Foguete Avançadas; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

Single-stage-to-orbit (SSTO) vehicles have the potential to enhance space transportation reliability and reduce costs. However, traditional nozzles with conical and bell-shaped contours are limited in their ability to deliver ideal performance across the entire flight envelope. As a result, various advanced rocket designs with altitude adaptive characteristics have been proposed, among which the dual-bell, E-D, and aerospike concepts have shown the most promise. This dissertation focuses specifically on the aerospike concept, aiming to design and evaluate a contour using numerical tools. To achieve this objective, Angelino’s method is implemented using Python to generate the aerospike contour for a specific operating altitude of 15545 meters, corresponding to a pressure ratio (PR) of 188 at the design point. The input parameters provided to the Python code include an exit Mach number of 4.16, an adiabatic index of 1.4 and the specification of 100 expansion lines. The CFD process for the numerical studies of the contour validation is performed using Ansys Workbench, specifically utilizing SpaceClaim for designing the control volume geometry and Fluent for solving the flow. In Fluent, a density-based solver is employed to analyze the flow behavior. Two different viscosity models are considered in the analysis: inviscid and realizable k-e. In addition to the design conditions, three additional PR are simulated: 20 (sea-level), 288 (altitude of 18285 m), and 20480 (altitude of 47750 m). It was concluded that both the inviscid and realizable k-e models exhibit a similar performance prediciton of the aerospike nozzle as it operates at different altitudes, as indicated by the specific impulse. Still, it was the realizable k-e model that demonstrated a higher level of detail in capturing flow phenomena compared to available experimental investigations. This included features such as better modeled Mach diamond and a temperature distribution with values above 7000 K. Regarding the altitude adaptability of the aerospike nozzle, its performance was observed to improve with increasing altitude. Underexpanded conditions demonstrated a nearly axial exhaust plume, showcasing the aerospike’s capability in maintaining thrust efficiency. In contrast, overexpanded conditions resulted in the lowest specific impulse. These findings highlight the advantages of the aerospike nozzle over traditional nozzles, which typically struggle in underexpansion scenarios.