The Effect of Swirl on Spark-Ignition Engine Combustion

In order to investigate the effect of swirl on combustion in a spark-ignition engine, a new experimental apparatus was developed. The test engine has a 78 mm bore, an 85 mm stroke and a pancake type combustion chamber. In this test engine, the combustion phenomena for various intensities of swirl flow can be investigated. The swirl flow in the cylinder was visualized by a smoke-wire method, and a laser Doppler anemometer and a hot-wire anemometer were adopted for the measurement of the velocity. The turbulence intensity was determined on the basis of the hot-wire data. Stoichiometric propane and air mixture was ignited at the center of the combustion chamber. The effect of swirl on combustion in the cylinder was investigated under various conditions of compression ratio and engine speed. As a result, it was found that the burn duration could be expressed as a function of the turbulence intensity. The effects of engine speed and the swirl ratio are not explicit and are included implicitly in the term of turbulence intensity.