Development of a calibrated technique forin situinvestigation of air–fuel mixing in engines

Abstract

This paper presents the role of imaging system design in developing an instrumentation technique to aid the validation of air-fuel mixing design hypotheses for use in next-generation internal combustion engines. In order to meet the challenge of extracting information from a research engine, the instrumentation system design was considered holistically through the application of 'scene constraint' principles. The objective is to obtain a two-dimensional map of fuel concentration in the cylinder, in order to be able to study the mixing process of air and fuel. To meet forthcoming emission regulations, a detailed understanding of this process is critical to the design of next generation (direct injection) gasoline engines. The carefully considered scene constraints, image acquisition and image analysis techniques described in this paper advance the laser-induced fluorescence technique to a point where it permits examination of cycle-to-cycle variability of the fuel-injection process, for example. A new approach to coping with fluorescence dependency on pressure and temperature, the choice of a fluorescence tracer, the determination of the optimum tracer concentration and the complete calibration methodology are described. The paper concludes with examples of calibrated measurements and evidence to indicate that information from this instrumentation technique method concurs with that derived from other experiments.