The experimental and theoretical investigation of the effect of swirl on the fuel-air mixing process in direct-injection diesel engines is described. The experimental work involved the further development of an existing hydraulic analogue technique which enables excellent flow visualisation. This was followed by the design and construction of a novel high-swirl combustion bomb which reproduces engine conditions under fine control. This experimental apparatus includes facilities for high-speed cine photography and a micro-computer based data acquisition and control system providing flexible software control of the fuel injection equipment and data sampling rates of up to 70 kHz. Typical non-combusting and combusting results are presented. Theoretical models of fuel-air mixing are reviewed. The phenomenological jet-mixing model developed and presented is based on an existing continuum mechanics approach and is solved by an integral method. The model includes momentum, heat and mass transfer and simulates jet cross-section distortion and the non-similarity of property profiles. It is intended that this model will form the basis of a proposed multi-zone combustion model.
|Date of Award||1983|