Search Results

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 increasing cost of prototype engine design and development has placed new emphasis on the importance of accurate analysis of combustion chamber components. A method to assess and improve the quality of thermal boundary conditions is described. The integration of analytical approaches and experimental techniques to validate and improve thermal boundary conditions is dependent on continuous improvement of theoretical models and correlation with measured results. To monitor and improve quality, it is important to operate a closed loop of prediction, measurement and feedback to the analysis system. The development of advanced computational methods, particularly the Finite Element Method (FEM) has increased the opportunities to include detailed component thermal analysis in combustion chamber design studies. In using FEM, much emphasis is traditionally placed on “accurate” mesh generation in order to minimise element distortion and optimise element polynomial order.

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.