Evaluation of Chemical Equilibrium and Non-Equilibrium Properties for LOX/LH2 Reaction Schemes

Abstract

Nine chemical reaction models for equilibrium schemes and six chemical models for non-equilibrium ones are studied, considering different conditions found in real liquid oxygen/liquid hydrogen rocket engines. Comparisons between two eight-species models have shown that the most complex is the best one. Besides, it was also verified that the most complex model has been the fastest, among sixand eight-species models. Both combustion temperature and thermochemical/transport properties depend only on the chemical species considered by the used model. Comparisons among results from the implemented code (Gibbs 1.3), Chemical Equilibrium with Applications and Thermochemical Information and Equilibrium Calculations, these last two codes from NASA, have shown that Gibbs 1.3 evaluates correctly both combustion temperature and thermochemical properties. Furthermore, analyses have shown that mass generation rates are very dependent on third body reaction equations and forward reaction constants.

Working process model development of the gas turbine engine combustor fueling on methanol

“…Traditionally, it is believed that the enthalpy of combustion products does not depend on pressure [2][3][4][5][6][7]. However, at high pressures of the gas mixture, its individual components (water and carbon dioxide) may have partial pressures exceeding the saturation pressure value at standard temperature Т 0 .…”

“…The first is the transition from pressure p 1 to pressure p 0 for the reactants, and the second is the transition from pressure p 0 to pressure p 2 for the combustion products (in the Brayton cycle, p 1 and p 2 coincide). In the works [2][3][4][5][6][7], which assume the independence of enthalpy from pressure, this circumstance is not taken into account, leading to a systematic error in determining the temperature at the end of the combustion process. Moreover, its discrepancy with the experiment is entirely attributed to the phenomenon of thermal dissociation [6,7].…”

“…It is noted that a mixture of ethanol and hydrogen appears to be a viable option from both an economic and environmental standpoint. In [7], six chemical nonequilibrium models are compared under various conditions encountered in real rocket engines. Unlike [2][3][4][5], the works [6,7] consider thermal dissociation of combustion products but do not accurately describe the equivalent chemical reaction path.…”

“…Thus, a common drawback of the mathematical models presented in [2][3][4][5][6][7] is the lack of analysis of the equivalent chemical reaction path at pressure other than standard one. Specifically, the absence of two additional isothermal processes: transitioning from actual pressure to standard one and reversing from standard pressure to actual one.…”

“…To account for the influence of pressure and thermal dissociation, two approaches can be employed: solving a system of chemical kinetics equations with a large number of equations [6,7], or utilizing experimental values of enthalpies or specific isobaric heat capacity с р as functions of temperature Т and pressure p [8]. Additionally, by adopting the second approach to determine the enthalpy of combustion products, we obtain a correctly formulated equivalent chemical reaction path.…”