Steady State Analysis of a Diesel Engine

The diesel engine powers nearly every heavy-duty truck on the globe. During the commissioning of a new Cummins ISX15 engine installation, a heavy-duty engine dynamometer is used to characterize the engine performance at a range of steady-state operating conditions (different speeds and loads). After adding significant new instrumentation, the efficiency and energy split distribution of the engine was acquired at each condition. The specific measurements taken during engine operation were input into a separate program in which the various energy transfers were all accounted. This includes fuel energy input, shaft work output, heat loss to the coolant, heat loss to the exhaust, and estimated heat lost through radiation. Through this data and calculations, the way by which diesel engines achieve high efficiency in general as well as higher efficiency at different speeds and loads was assessed. General trends from the data include a higher efficiency and less heat loss to the radiator at larger torque, as well as a larger exhaust energy content at a higher speed. Future testing will include a larger range of speeds and loads to further bolster these trends and establish concrete data of engine efficiency.