System Optimization of Turbo-Compound Engine (Second Report: Effects of Compression Ratio)

The design parameters of a turbo-compound engine system affecting the thermal efficiency and engine output have been analyzed, considering the allowable limit of the maximum cylinder pressure, exhaust temperature and other factors. By adjusting the values of the engine compression ratio to 20, the cross sectional area ratio of the turbine inlet to 0.4, and the compressor pressure ratio to 2.2 at full load and to 1.7 at part load, the thermal efficiencies of approximately 40% at full load and 25% at part load have been obtained in turbo-compound engine. Furthermore, the changes the optimum values are comparatively small, even if the engine compression ratio is greatly changed from 22 to 14.