Development of a skeletal mechanism for heavy-duty engines fuelled by diesel and natural gas

Abstract

The purpose of this work is to develop a skeletal dual-fuel mechanism for heavy-duty engines fuelled by diesel and natural gas. With diesel fuel modeled as n-heptane, and natural gas modeled as methane, the skeletal mechanism was constructed by coupling the two skeletal mechanisms reduced detailed mechanisms: n-heptane and methane mechanisms. Directed relation graph error propagation and sensitivity analysis, computational singular perturbation and reaction rate adjustment methods were employed for mechanism reduction. The final skeletal dual-fuel mechanism is composed of 61 species and 199 reactions. So as to validate the fidelity of the novel skeletal dual-fuel mechanism, zero-dimension ignition delay testing against shock tube experimental results and 3-dimensional engine validation about in-cylinder pressures, heat release rates and NOx and CO emissions against engine testing results were performed under various operating conditions. The validation results indicate that the dual-fuel mechanism can accurately reproduce the ignition behaviors, combustion characteristics and emission trends in heavy-duty diesel/NG dual-fuel engines. Besides, a parallel computing method based on the round-robin algorithm was developed which can significantly save the time for calculating. Combined with the new developed skeletal dual-fuel mechanism, the 3D CFD simulation for the combustion in heavy-duty engines can be done in a reasonable computational time.