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

With a view to preventing idling knock of a pre-combustion chamber type Diesel engine, a method to raise the compression temperature by means of inlet throttling was applied to a testing engine examining the availability of the device. From measurement of engine noise and indicator diagrams, it has been revealed that an adequate throttling weakens the combustion noise, e.g. maximum rate of pressure rise in the main combustion chamber has been reduced from 6.5kg/cm2/deg. C.A. to 2.0kg/cm2/deg. C. A. at 60°C of temperature at cooling water exit, namely, from rather hard knocking to knock-free running. The reduction, however, is limited when the intensity of knocking is too high, since the shortened ignition delay of the fuel due to the throttling does not serve to prevent the combustibles from escaping into the main combustion chamber.