The effect of combustion chamber geometry layout on combustion and emission

Abstract

In this paper some results concerning the combined effect of the tumble flow and combustion chamber geometry layout variations on flame front shape and its propagation through homogenous mixture of isooctane and air are presented. Spatial distributions of NO in different combustion chamber geometries are presented as well. The basic combustion chamber geometry layout considered consists of the flat head with two vertical valves and a cylindrical bowl subjected to variations of depth and squish area. All results presented were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry with moving objects and boundaries with modified KIVA3 and KIVA3V source codes. Two additional computer codes were applied to generate boundary conditions for KIVA3V calculations with moving valves. The AVL TYCON code was used for the calculation of valve lift profiles, and AVL BOOST code was used for the calculation of relevant data set in the valve regions. Different combustion chamber geometry layouts generate different levels of squish, and the combustion effects in essence depend on the interaction of that flow with tumble. It was found that for particular combustion chamber shapes with different diameter/depth aspect ratios entirely different flame front shapes and propagation velocities were encountered primarily due to variations of fluid flow patterns in the vicinity of top dead center.