Search Results

LDA measurements of the flow in a motored engine near TDC of compression have been obtained, along with burnrate data in a firing engine having a near-central spark plug location. Results are reported for two different intake ports and four intake valve lifts varying from 25% to 100% of full lift. Opposite trends of swirl vs valve lift were found for the two ports, and the rms velocity fluctuation was found to be relatively insensitive to changes in valve lift. Regression analysis of the burn duration data was conducted, with swirl ratio and rms as independent variables. The analysis indicated that burn duration decreases with an increase in swirl ratio and/or rms velocity fluctuation. In light of the experimental findings, a new conceptual model is proposed regarding the effect of valve lift on the dissipation of turbulent velocity via changes in the length scale.

During combustion in a diesel engine radiation heat transfer is the same order of magnitude as the convection heat transfer. Therefore for a reliable engine simulation the radiation transfer equation should be solved simultaneously with the flow and energy equations. A rigorous solution for the radiative transfer is, however, neither warranted nor cost effective. An approximation is needed at a level consistent with those used in modeling the fuel spray, the chemical kinetics, the soot and the turbulence. The approximation should account for the anisotropic behavior of radiation in the engine and be easily integrated into finite difference codes. This paper illustrates use of the first and the third order spherical harmonics approximation to the radiative transfer equation and the delta-Eddington approximation to the scattering phase function for droplets in the flow.