A Note on Unburned Hydrocarbon Emissions from Automotive Engines

Abstract

A careful treatment of a n unsteady one-dimensional laminar model of the interaction of a propagating premixed fuel-lean flame with a cooled wall is undertaken. For the reciprocatingpiston-type automotive-engine context of interest, expansional cooling of the power stroke, and thermal nonuniformity in the burned gas owing to nonisobaric combustion. are included; nevertheless, nearly complere oxidation of residual near-wall hydrocarbons prior to blowdown is confirmed. Measurement of a significant peak at blowdown for hydrocarbon content of the cylinder exhaust under heavy-load operation, once explained in terms of head-wall-quench-layer content, now seems puzzling, and the alternative crevice-content explanation appears forced. Suggestions for further experimental and theoretical investigations concerning piston-crevice contributions to unburned. hydrocarbon emissions, and their reduction, are set forth.

Flame Wall-Quenching by Radiation and Conduction in Combustion of Condensed Fuels

“…It has long been regarded as a major contributing mechanism which results in unburned hydrocarbons being exhausted from automotive engines (Daniel, 1956). However, recent experimental results suggest that the contribution by wallquenching may be less significant than it had once been thought (Adamczyk et al, 1982;Fendel et a/., 1983).…”