Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine

The study performs an exergy analysis component-wise on a heavy-duty diesel engine examining its behavior for different injection timings and rates of exhaust gas recirculation (EGR). A calibrated Diesel-RK model is used to simulate the engine operating at steady state over a representative speed-load range. A methodology is used to evaluate key exergy terms; fuel, brake, exhaust, wall heat, and destruction exergy, using a post-processing framework of the same type. The results show that when EGR is increased from 0 to 0.20, the brake exergy fraction decreases from 33% to 14%, and destruction exergy fraction increases from 44% to 73%. This means that EGR dilution increases the irreversibility of combustion

more than wall heat transfer. Without EGR, destruction exergy is usually 39-45% of the total fuel exergy. Advanced injection timing causes heat release to be close to top dead center and redistributes wall heat exergy from the liner, which decreases from 40% to 26%, to the piston and cylinder head, where their contributions increase to about 37-40% each. Under high engine load, moderate advancement of injection timing improves thermodynamic efficiency and too much advancement increases thermal wall loading and lowers the improvement of efficiency. The engine shows increased sensitivity under part load conditions, and this is mostly due to the duration of combustion.

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