Keynote Speakers

Refined Chemical Equilibrium Modeling for Cryogenic Combustion and Phase Transitions

Chemical equilibrium calculations are a cornerstone of modern propulsion system design and analysis, providing critical predictions of thermodynamic properties, species compositions, and phase behavior in reacting flows. Accurate modeling of equilibrium compositions is particularly important in cryogenic combustion systems and low mixture ratio regimes, where condensed-phase species, polymorphic transitions, and triple-point phenomena significantly influence system performance. Computational tools such as NASA CEA and RPA have become standard references in this domain. However, their implementations exhibit notable limitations when applied to these challenging conditions. In particular, inconsistencies have been observed between the theoretical formulations reported in NASA documentation and their algorithmic realization, leading to discontinuities in temperature-mixture ratio profiles and inaccuracies in the evaluation of thermodynamic properties. To address these deficiencies, this work reconstructs the NASA CEA methodology from first principles, retaining the original Gibbs free energy minimization framework based on the method of chemical potentials. Several algorithmic refinements and corrective plugins have been incorporated to enhance numerical stability, ensure consistent treatment of condensed phases, and resolve issues related to triple-point and polymorphic solid transitions. The revised solver provides continuous and physically consistent predictions of temperature, enthalpy, and species compositions across multiphase domains. The effectiveness of the proposed approach is demonstrated using representative cryogenic combustion systems, including liquid methane and liquid oxygen and liquid hydrogen and liquid oxygen mixtures. The refined model accurately reproduces expected triple-point behavior and smooth polymorphic phase transitions, highlighting its potential for high-fidelity combustion simulations and integration with CFD solvers for advanced propulsion applications. The reconstructed chemical equilibrium framework demonstrates that algorithmic refinements significantly improve the predictive accuracy of thermodynamic properties in cryogenic and low mixture ratio combustion systems. By addressing deficiencies in the treatment of condensed species, polymorphic solid transitions, and triple-point conditions, the refined solver eliminates discontinuities in temperature-mixture ratio profiles and produces physically consistent enthalpy and composition predictions. Applications to liquid methane and liquid oxygen and liquid hydrogen and liquid oxygen combustion illustrate the practical implications of these improvements.

In CH4-O2 and H2-O2 mixtures, the solver reproduces the expected triple-point temperature and smooth phase behavior, which is critical for accurate modeling of low-O/F propellant regimes. Moreover, the refined model ensures continuity in both thermodynamic and compositional outputs, overcoming limitations observed in NASA CEA and RPA. These results highlight that even minor deviations in conventional solvers can propagate into significant errors in related mixtures, emphasizing the importance of rigorous algorithmic treatment for condensed-phase phenomena. The proposed methodology establishes a robust, physically consistent foundation for chemical equilibrium calculations and facilitates integration with CFD solvers, enabling high-fidelity simulations of advanced propulsion systems. This approach provides both theoretical rigor and practical utility, supporting improved design, analysis, and optimization of cryogenic engines. The refined chemical equilibrium solver corrects deficiencies in NASA CEA and RPA, accurately modeling condensed species, triple points, and polymorphic transitions. Validation with CH4-O2 and H2-O2 demonstrates smooth, physically consistent predictions, enabling high-fidelity cryogenic propulsion simulations.

Parviz Abdullayev, PhD., Professor, In 1990 he graduated Leningrad Mechanical Institute (Russia) in Flight Vehicles Engines field. Since 2003 he is Head of the Flight Vehicles and Jet Engines Department of the National Aviation Academy (Azerbaijan). He defended the Ph.D. thesis in 2001 and the D.Sc. thesis in 2014. Author of 104 scientific papers, 3 patents and 5 books. His research interest: mathematical modeling of aircraft and rocket engines, thermo-gas-dynamics, diagnostics with soft computing and machine learning.

1- aircraft engines
2- rocket engines
3-health monitoring and diagnostics
4- soft computing