Measurement of Quenching Layer Thickness by a Thermocouple

Abstract

Unburned hydrocarbons remaining in a wall quenching layer have been proposed as a major source of hydrocarbon emissions in spark-ignited internal combustion engines. Although quenching layer thickness can be measured by an optical method, this method cannot usually apply to the combustion chambers of spark-ignited engines where flame propagation is very complex. Therefore quenching layer thickness have been often calculated by the data of quenching distances measured by quenching disks or residual gas analysis.In this paper, the direct measurement system of quenching layer thickness by a thermocouple is described. In consequence, it is found that this method is valid to measure directly quenching layer thickness, because the tendency of the data in this experiment agrees well with that of the quenching distances. A quenching layer is separated into two parts. One is a perfect unreaction layer and the other is a partial reaction layer. The perfect unreaction layer thickness which dominates hydrocarbon emissions is about one-fifth of the quenching layer thickness. Hydrocarbon emissions in spark-ignited internal combustion engines can be estimated by this measurement system.