Direct Injection as a Combustion Process for Light Diesel Engines 785001

Despite their higher fuel consumption, indirect-injection Diesel engines are commonly used for light vehicles due to the drawbacks of direct-injection Diesel operation, namely, smaller RPM ranges, lower specific power output, higher noise levels, and greater NOx and HC emissions. Despite previous attempts, no practical solutions have been found to permit the use of direct-injection operation. The paper discusses some of the results of a project spanning several years, undertaken to overcome these problems of direct-injection Diesels. Particular modifications of the combustion process include a spiral inlet-channel for combustion air turbulence, a specially shaped combustion space, a special multi-hole injection jet, and compression ratios of at least 21.5:1. Subsequent careful engine tuning permitted substantial improvements in air utilization factors, overall performance, emissions, starting characteristics, engine cooling requirements, and noise levels, among others. Results, as portrayed graphically, are based on tests of a converted 2.2 l engine and a 2.1 l prototype engine. Further improvements are expected.


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