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Mixture formation in modern SI engines is still lacking effective means of control. Widely known air, wall and spray-guided mixture formation solutions have been applied more or less successfully by different manufacturers. Spray-guided systems have the advantage of requiring only a precise control of the spray features, allowing for simpler air intake devices. But air entrainment by spray is not always sufficiently effective to create the mixing conditions of a good combustion. This paper aims at further understanding the processes of air entrainment by sprays. A pressure vessel with optical access is equipped with a gasoline injector tested for different injection and ambient pressures, injection times and other parameters. A fluorescent/MIE dual PIV technique is used to obtain simultaneous 2D velocity fields of spray droplets and seeding particles of surrounding gas. Fuel used is iso-octane, doped with fluoranthene as fluorescent tracer.

A new high performance 1.4 litre naturally aspirated IDI engine with advanced comet type precombustion chamber has been designed and developed within a duration of 2.5 years for Tata Minicar. The prototype could be developed in a short time of 8 months due to extensive use of CAD/CAM facilities and close interaction with suppliers along with simultaneous engineering methods. A power rating of 40.5 hp/lt could be achieved due to extensive optimisation of combustion parameters such as geometry of precombustion chamber and fuel injection parameters. This paper describes the features of this engine along with development strategy adopted to achieve the performance and durability targets.