Development of a Preliminary Framework for the Evaluation of Oxygen-Hydrogen Combustion Characteristics

• Autor(a) principal: Pedrosa, João Ricardo de Sousa
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10400.6/13768
• topic: Combustão de Hidrogénio-Oxigénio; Combustão em Condições Supercríticas; Motor Foguete de Propelente Líquido; Temperatura Adiabática de Chama

Rocket engine development always involves maximizing performance and reliability and minimizing costs. The experimental tests that are part of that development can be costly and complex to execute. Therefore, there has been a search to complement these numerical tests with the computational power of computers through numerical tools. In this way, it is possible to direct experimental campaigns to regions or phenomena of interest, reducing their costs. Specifically, for liquid rocket engines, the need for higher performance, that is, higher specific impulse, led to an increase in the chamber pressure of these propulsion systems. Moreover, gaseous-hydrogen and liquid-oxygen is one the propellant combinations that offers high performance (specific impulse) because of its high heating value, which results in high adiabatic flame temperature and low molecular weight. These are the reasons why this propellant combination has been used in many liquid rocket engine propulsion systems. In this work, a numerical tool is developed to compute the adiabatic flame temperature and the corresponding chemical equilibrium composition for a given value of pressure and equivalence ratio for the combustion reaction between hydrogen and oxygen. As temperature values are very high, the dissociation of combustion products is taken into account. Three chemical reaction equations are considered, each with a different number of species. The minimization of the Gibbs free energy is done to calculate the chemical equilibrium composition. A thermodynamic library is used to compute thermodynamic properties for individual species. Results of calculations show that an increase in pressure translates into an increase in the adiabatic flame temperature. Also, as the number of species increases, the adiabatic flame temperature decreases. The maximum adiabatic flame temperature is obtained for slightly rich mixtures.