Turbulent Transient Gas Injections

Abstract

Compressible transient turbulent gaseous jets are formed when natural gas is injected directly into a diesel engine. Multi-dimensional simulations are used to analyze the penetration, mixing, and combustion of such gaseous fuel jets. The capability of multi-dimensional numerical simulations, based on the k-ε turbulence model, to reproduce the experimentally verified penetration rate of free transient jets is evaluated. The model is found to reproduce the penetration rate dependencies on momentum, time, and density, but is more accurate when one of the k-ε coefficients is modified. The paper discusses other factors affecting the accuracy of the calculations, in particular, the mesh density and underexpanded injection conditions. Simulations are then used to determine the impact of chamber turbulence, injection duration, and wall contact on transient jet penetration. The model also shows that gaseous jets and evaporating diesel sprays with small droplet size mix at much the same rate when injected with equivalent momentum injection rate. [S0098-2202(00)02304-X]