1995-10-01

Comparison of the Effects of Intake-Generated Swirl and Tumble on Turbulence Characteristics in a 4-Valve Engine 952457

An experimental investigation is carried out on the effect of Swirl and Tumble on turbulence and combustion characteristics in four-valve spark ignition engines. This study is conducted on an optically accessed single cylinder research engine. The in-cylinder motion is varied by means of flow-control baffle located between the intake manifold and the cylinder head. Several baffle sizes and shapes have been designed to induce various in-cylinder flow fields. The equivalent angular speed of the tumble and swirl vortices, occurring inside the cylinder, are determined from Laser Doppler Velocimetry. Comparisons with measurements from a conventional steady flow rig which measures air motion speed with a paddle wheel anemometer are presented and show a good correlation between the two measurement techniques. The turbulence and local velocity in the combustion chamber at ignition are measured and correlated with combustion characteristics obtained from analysis of the combustion in the cylinder.
The influence of tumble and swirl levels on the characteristics of turbulence and combustion is analysed. As the tumble intensity increases, the breakdown of the tumbling motion into turbulence occurs earlier in the compression stroke. For swirl configurations, the location of the center of rotation has a significant impact on the characteristics of turbulence at the spark plug location. Turbulence intensity measured at the spark plug location correlates well with combustion characteristics such as stability, delay angle, burn angle obtained from heat release rate analysis.
* Numbers in parentheses designate references at end of paper.

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