An Experimental Investigation into Diesel Engine Size-Scaling Parameters

With recent increases in global fuel prices there has become a growing interest in expanding the use of diesel engines in the transportation industry. However, new engine development is costly and time intensive, requiring many hours of expensive engine tests. The ability to accurately predict an engine's performance based on existing models would reduce the expense involved in creating a new engine of different size. In the present study experimental results from two single-cylinder direct injection diesel engines were used to examine previously developed engine scaling models. The first scaling model was based on an equal spray penetration correlation. The second model considered both equal spray penetration and flame lift-off length. The engines used were a heavy-duty Caterpillar engine with a 2.44L displacement and a light-duty GM engine with a 0.48L displacement. Several modifications were performed to the Caterpillar engine before testing in order to be consistent with the scaling models. These modifications included: a common geometry piston, a scaled injector nozzle, a scaled rate of injection profile by utilizing a flexible Hydraulic Electronic Unit Injector (HEUI), and an increased swirl ratio. This paper compares these engines operating across a conventional diesel combustion regime to examine the validity of the scaling arguments and to test the effects of engine speed and swirl ratio.