The influence of blow-by on indicated work output from a diesel engine under cold start conditions

Abstract

The start-up time of automotive, light-duty diesel engines increases as ambient temperature falls. One contributory cause is a reduction in indicated work output. The influence of blow-by in bringing about the reduction has been investigated. The experimental study was carried out at 20° C on four-cylinder direct injection (DI) engines with a capacity of around 2 l. Blow-by losses were inferred from measurements of gas flow from the crankcase. Indicated mean effective pressure was shown to decrease linearly with increasing blow-by rate. The relationship accounts for almost all the reduction in work output at low temperatures. The reduction is associated with the influence of blow-by on heat released during combustion, rather than with the transport of enthalpy from the cylinder.