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As part of an ongoing investigation, the influence of in-cylinder charge density, and injector nozzle geometry on the behaviour of diesel sprays were examined using high-speed imaging. Both liquid and vapour penetration profiles were investigated in operating conditions representative of a modern turbocharged after-cooled HSDI diesel engine. These conditions were achieved in an optical rapid compression machine fitted with a common rail fuel injection system. Differences in spray liquid and vapour penetrations were observed for different nozzle geometries and in-cylinder conditions over a range of injection fuelling representative of those in a typical engine map. Investigation into the differences in spray structure formed by multi-hole and single-hole injections were also undertaken.

The important influence of engine friction on fuel economy has aroused new interest in its accurate measurement. Ricardo have developed a new system of instrumentation capable of measuring mechanical friction under any steady engine running conditions, and isolating the proportion of engine power absorbed by each of the auxiliary drives. Furthermore, auxiliary drive torque is measured instantaneously as a function of crank angle, enabling the dynamics of the drives to be studied. The instrumentation can be easily adapted to fit most engine types and configurations whilst retaining the original auxiliary drive design. Results obtained from gasoline and diesel versions of a 1.6 litre automotive engine using this instrumentation are described. Mechanical friction, pumping losses and auxiliary drive losses were measured with engine load, speed and coolant temperature varied.