A hybrid kinetic mechanism reduction scheme based on the on-the-fly reduction and quasi-steady-state approximation

摘要

A hybrid kinetic mechanism reduction approach combining global reduction and dynamic reduction methods is proposed in the present work. The approach is based on the dynamic flux-based on-the-fly reduction and the globally applied quasi-steady-state approximation (QSSA). Globally identified quasi-steady-state (QSS) species are separated from the kinetic ODEs and described by a set of nonlinear algebraic equations. Then the dynamic element flux analysis in the on-the-fly reduction is integrated to determine the active non-QSS species at each time step of the computation. The proposed hybrid reduction procedure reduces the number of species involved in the transport calculation, while still maintaining efficient chemistry calculation. The computational framework of the proposed methodology is demonstrated in a PFR model as well as a two-dimensional engine CFD model with detailed methane mechanism and several optimally selected QSS species sets. The ignition timing is accurately predicted under various reaction conditions compared to that from simulations using the detailed mechanism. Also, the temperature, pressure, and species concentration profiles captured with hybrid reduction scheme are in excellent agreement with the results in the detailed mechanism calculations. Satisfactory performance of the hybrid reduction scheme is achieved in predicting important characteristics of fuel combustion process. The hybrid kinetic mechanism reduction scheme is a promising approach to address combustion problems in complex reactive flow environment, especially for enabling the computational simulations of transport-intensive applications.