Computational Fluid Dynamics of IC Engine Performance and Emissions (Research)
This paper describes the status of an ongoing research program conducted by Radian International for GRI to model fuel/air mixing, scavenging efficiency, and NOx emissions from natural gas IC engines using Computational Fluid Dynamics (CFD). The CFD tool is currently being used to identify and correlate key engine design parameters with NOx and formaldehyde emissions and to characterize the differences in these key parameters among engine designs. NOx emissions are explicitly predicted in the CFD model using an extended Zeldovich mechanism modified for spark-ignited internal combustion, while formaldehyde emissions are correlated outside the CFD model with fuel/air mixing and scavenging efficiency. The CFD tool has been used to evaluate the effects of fuel manifold, air manifold, and exhaust manifold pressures on NOx emissions, fuel/air mixing and scavenging efficiency. The CFD models for both a Clark TLA and a Cooper GMVH engine have been validated against field measurement data for bulk air flow, exhaust gas temperature, exhaust gas composition, and peak firing pressure. Comparative engine performance prediction results are presented in the paper for the Clark and Cooper engines, as well as some operational and design modification impacts modeling results which illustrate the usefulness of the CFD tool to evaluate various equipment retrofit alternatives.