Characteristics of Quenching Crevice Widths in Combustion Chamber of a Spark Ignition Engine.

Abstract

Exhaust HC emissions from spark ignition engines are still creating a major environmental problem. It is difficult to reduce HC emissions during engine warm-up because the catalysts cannot work well at low temperatures. The source of unburned HCs from engines is thought to be crevices in the combustion chamber, oil layer and deposits on the cylinder wall surfaces. Quenching crevice widths in the combustion chamber were measured under various engine operating conditions with an ion probe that could detect flame arrival. Then, an experimental equation of quenching crevice width was estimated as a function of cylinder pressure and cylinder wall temperature. Schlieren photographs of a combustion chamber with a lubricant-free piston were also taken to monitor the flow of gas of unburned HCs emitted from the piston crevice during the expansion and exhaust processes.