Prevention of Idling Knock of a Diesel Engine by Means of Inlet Throttling

Abstract

With a view to preventing the idling knock of a pre-combustion chamber type Diesel engine, a method to raise the compression temperature by means of inlet throttling has been applied to a test engine to examine the availability of the device. From measurement of engine noise and indicator diagrams, it has been revealed that by an adequate throttling the combustion noise, even if rather hard knock, is weakened to knock-free running, e.g. maximum rate of presure rise in the main combustion chamber from 6.5kg/cm²/deg.C.A. to 2.0kg/cm²/deg.C.A. at 60°C of temperature at cooling water exit. The reduction, however, is limited when knock is too hard, since abridgement of ignition delay of the fuel caused by the throttling does not serve to prevent the combustibles from passing into the main combustion chamber.