Abstract: In response to the problem of unclear performance characteristics and insufficiently explored optimization potential of the Miller cycle in highly intensified diesel engines under high-load conditions, experiments and simulations of the late intake valve closing(LIVC) Miller Cycle on highly intensified diesel engines are conducted. Based on thermodynamic principles and experimental data, a thorough analysis is performed on the energy flow, exergy flow balance, and their variation patterns across various engine speeds under full-load conditions. A one-dimensional thermodynamic model is constructed using GT-suite, and the LIVC angle is adjusted to implement the Miller cycle aiming to optimize engine performance. The research results indicate that the delayed closing of the intake valve leads to a gradual decrease in the engine's miscellaneous losses, an improvement in brake power, and a reduction in fuel consumption rate, achieving optimal performance at a Miller phase of 10V84. In addition, the proportion of dynamic exergy is improved, the heat transfer exergy and exergy destruction are reduced through the Miller cycle. By analyzing the variation law of exergy change items with crank angle, it is found that Miller cycle can optimize the compression, intake and exhaust processes to improve the cumulative dynamic exergy and reduce the instantaneous heat transfer exergy in the combustion stage, thus the cumulative heat transfer exergy is reduced accordingly.

Key words: high-strength diesel engines, miller cycle, energy balance, exergy balance, exergy variation terms