Formation and Combustion of Carbon in a Diesel Engine

The effects of the shape of the injection diagram, injection period, and injection nozzle on diesel engine smoke have been studied for a wide range of injection timings and engine speeds on a 1-litre direct-injection type engine cylinder. Cycle temperatures were also varied by raising inlet air temperature and by introducing water mixed with diesel fuel. An analysis of these results shows that the exhaust smoke level is mainly determined by the concentration of soot at the end of heat release (net soot release), i.e. any subsequent combustion of the net soot release before exhaust valve opening is unimportant. The net soot release in a diesel engine cylinder, for a given fuel, is controlled by the amount and rate of diffusion burning and the flame temperatures.