Computational Investigation on the Performance Increase of a Small Industrial Diesel Engine Regarding the Effects of Compression Ratio, Piston Bowl Shape and Injection Strategy

This paper describes the simulative approach to calibrate an already extremely highly turbocharged industrial diesel engine for higher low-speed torque. The engine, which is already operating at its cylinder-pressure maximum, is to achieve close to 30 bar effective mean pressure through suitable calibration between the compression ratio, piston-bowl shape and injection strategy. The basic idea of the study is to lower the compression ratio for even higher injection masses and boost pressures, with the resulting disadvantages in the area of emissions and fuel consumption being partially compensated for by optimizations in the areas of piston shape and injection strategy. The simulations primarily involve the use of the 3D CFD software Converge CFD for in-cylinder calibration and a fully predictive 1D full-engine model in GT Suite. The simulations are based on a two-stage turbocharged 1950 cc four-cylinder industrial diesel engine, which is used for validation of the initial simulation. With the maximum increase in fuel mass and boost pressure, the effective mean pressure could be increased up to 28 bar, while specific consumption increased only slightly. Depending on the geometry, NOx or CO and UHC emissions could be reduced.