Effect of Air Swirl on Smoke and Gaseous Emissions from Direct-Injection Diesel Engines

This paper describes and discusses the results obtained from tests of the effect of air swirl variations on smoke and gaseous emissions from direct-injection-type diesel engines. Within the limits of the swirl variations used, an increase in swirl reduced emissions of smoke and carbon monoxide but increased nitric oxide emissions. An increase in swirl also makes it possible to retard appreciably the injection timing for optimum engine efficiency, and this more than compensates for the increase in nitric oxide emission due to the increase in swirl. It is also shown that the air swirl intervenes in the processes of smoke and gaseous pollutant formation by affecting the details of the fuel-air mixing processes.