Search Results

A program of development and experimental validation of a multidimensional spray prediction method, based on the discrete droplet model, has been broadened to include computational investigations of the effects of random perturbations of the injection velocity on the spray characteristics, and further detailed examination of the spray structure and development. The results demonstrate strong dependence of the predicted spray penetration length on the precise start-of-injection time and injection velocity data, and relative insensitivity to subsequent variations of the injection velocity. Specifically, it is found that under imposition of random variations of the injection velocity, the variation of the spray-tip penetration and velocity remain smooth, bearing no correspondence to the instantaneous spray injection velocity.

An optical imaging technique has been developed which allows the visual observation of fuel vapour within selected planes in optically accessed combustion chambers of Spark Ignition engines. The technique utilises fluorescence radiation of hydrocarbon molecules to image fuel vapour distribution. This fluorescence radiation is induced by a pulsed laser light sheet projected into the transparent combustion chamber and it can be observed with an intensified camera gated synchronously with the pulsed laser at any selected time instant of the engine cycle. In addition to recording mixture distribution, the camera arrangement also allows visualisation of the gasoline flame propagation. These imaging methods are used for he investigation of mixture formation and flame development in a transparent, disc-shaped combustion chamber under low speed and low load conditions.

Formation, ignition and combustion of diesel fuel sprays have been observed in the combustion chamber of an optically accessed single cylinder diesel engine. Two different combustion chamber geometries allowed the fuel sprays to be studied under quiescent and cross flow conditions. The study of the spatial distribution with different single shot photography techniques is complemented with an investigation of the temporal development of spray and flame propagation by an electronic high-speed line-scan technique. This continuous, time resolved analysis technique allows to resolve the influence of temporal variations imposed on the spray propagation and combustion by the fuel injection schedule. The application of these methods to the investigation of diesel sprays highlights mechanisms which govern the propagation and distribution of fuel sprays, fuel evaporation and the formation of a combustible fuel-air mixture.