COMBUSTION OF METHANE AND ETHANE WITH CO2 REPLACING N-2 AS A DILUENT - MODELING OF COMBINED EFFECTS OF DETAILED CHEMICAL-KINETICS AND THERMAL-PROPERTIES ON THE EARLY STAGES OF COMBUSTION

Simulations of methane combustion are developed for a synthetic atmosp here system where nitrogen is replaced as diluent with carbon dioxide. Special attention is given to the role of the detailed chemistry, usi ng a scheme containing similar to 100 separate reactions. The sensitiv ity of the results to the major reactions is analysed, and the approac h to equilibrium is considered. Examination of a set of model problems shows that where there is a large initial concentration of carbon dio xide, the chemical effects are very important. The results for constan t-pressure combustion coincide with conventional expectations, whereas those for a constant-volume system initiated by isotropic auto-igniti on are very much counter to intuition. The methods are validated by si mulating a plug-flow reactor, for which agreement with experiment is g ood. The typical application of this work is to subsea vehicles and ot her closed-environment machines, and the recognition of the importance of chemical effects points to the possibility of chemically modifying performance.