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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.

This paper describes an experimental investigation to explore and optimise the performance, economy and emissions of a direct injection gasoline engine. Building on previous experimental direct injection investigations at Ricardo, a single cylinder engine has been designed to accommodate common rail electronically controlled fuel injection equipment together with appropriate port configuration and combustion chamber geometry. Experimental data is presented on the effects of chamber geometry, charge motion and fuel injection characteristics on octane requirement, lean limit, fuel consumption and exhaust emissions at typical automotive engine operating conditions. The configuration is shown to achieve stable combustion at air/fuel ratios in excess of 50:1 enabling unthrottled operation over a wide operating range. Strategies are demonstrated to control engine out emissions to levels approaching conventional port injected gasoline engines.