Formation of Oxides of Nitrogen in a Diesel Engine : In the Case of Swirl Chamber Type

Abstract

Similarly to other combustion systems, reduction of ixides of nitrogen emitted from diesel engines is one of the urgent problems to be solved from the viewpoint of photochemical smog. However, their formations are not fully understood yet and the effects of engine variables on their emissions are still not well known. In this paper, the tendency of the nitric oxide emission has been investigated with a swirl chamber diesel engine, by systematically changing some engine parameters. As the result, the following facts have been revealed : Some factors effective to flame cooling supress the nitric oxide formation at lower fuel-air equivalence rations, while they have less efect at higher ratios. In the latter range, the nitric oxide decreases with this ratio, which is attributable to the increase in the local fuel-overrich zone somewhere in the combustion space, and its decrease is largely dependent on the outflow of gas from the swirl chamber into the main chamber.