A 4-species, 4-step Global Reaction Mechanism (GRM), developed by Zhu et al. (2012) and derived from detailed chemistry using a thermochemical approach, is evaluated for a range of premixed reactive mixtures. While detailed Elementary Reaction Mechanisms (ERMs) provide the most fundamental and precise description of reactive flows, the large number of species, reactions, and associated computer requirements to process their chemical data prevents them from being applied to large-scale and high resolution numerical simulations. Moreover, for detonation problems in particular, there has been an insufficient replication of the complex reality of the phenomenon through adequately resolved numerical simulations, which has lead to a constant demand for more accurate and affordable models. In contrast to ERMs, idealized GRMs simplify the reaction mechanism by using global reaction groups of species instead of individual elementary chemical species. The most common example of a GRM is the classical one-step model which considers only two global species but is incapable of producing some fundamental features of real combustion chemistry, such as independent control of induction and reaction lengths. Unfortunately, this reduces the scope of applicability of the derived model since the mixture chemistry has a vital influence on several key aspects of the detonation phenomenon like ignition, quenching, and the structure of the detonation wave front. While two- and three-step models are known to allow for better ignition control, the proposed 4-step model is advantageous as non-equilibrium effects may also be accounted for. As part of this work, we have developed an automated procedure in Python, using Cantera, to acquire the 4-step GRM model parameters derived from a detailed ERM for any premixed gas. The GRM itself involves four species that exhibit equivalent thermodynamic properties to the ERM by mimicking the thermodynamic paths produced by detailed chemistry. These global reaction species, along with their corresponding molecular weight and enthalpy, are first derived from real equilibrium properties using a reference ERM. Reaction paths and rates are then determined for these global species by conducting constant volume ignition problems and examining their evolution under varied conditions. Finally, we derive a leading-order analytical solution for easy calibration of the induction delay. The proposed mechanism is then validated against various ERMs by computing constant volume and constant pressure ignition problems, and also the steady detonation ZND structure in one-dimension. Mixtures involving hydrogen, methane, acetylene, and propane are investigated, each known to exhibit different degrees of detonation instability in unsteady and multi-dimensional simulations.


Performance of a Generic 4-Step Global Reaction Mechanism With Equilibrium Effects for Detonation Applications

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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