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Until quite recently, it appeared that there was an effective lower limit on bore size in open-chamber diesel engines. This paper presents a technique for improving combustion in the small open-chamber diesel engine. Recent work at MIT on a 2-1/2 in bore, short-stroke diesel engine has demonstrated that good efficiency can be obtained through a combination of a large-hole nozzle and the use of air swirl to prevent overpenetration. There is some indication that good efficiency can be obtained over a wider operating range than standard diesel practice. A method of design analysis for this type of engine is presented, along with techniques for estimating the swirl and nozzle design parameters.

A model has been developed to predict the performance of the Texaco Controlled Combustion, Stratified Charge Engine starting from engine geometry, fuel characteristics and the operating conditions. This performance model divides the engine cycle into the following phases: Intake, Compression, Rapid Combustion, Mixing-Dominated Expansion, Heat-Transfer Dominated Expansion and Exhaust. During the rapid combustion phase, the rate of heat release is assumed to be controlled by the rate of fuel injection and the air-to-fuel ratio. The burning rate in the mixing controlled stage appears to be dominated by the rate of entrainment of the surrounding gas by the plume of burning products and this rate is assumed to be controlled by the turbulent eddy entrainment velocity. A plume geometry model has been developed to obtain the surface area of the plume for entrainment during the mixing dominated phase.