This work studies the optimum heat release law of a direct injection diesel engine under constrained conditions. For this purpose, a zero-dimensional predictive model of a diesel engine is coupled to an optimization tool used to shape the heat release law in order to optimize some outputs (maximize gross indicated efficiency and minimize NO x emissions) while keeping several restrictions (mechanical limits such as maximum peak pressure and maximum pressure rise rate). In a first step, this methodology is applied under different heat transfer scenarios without restrictions to evaluate the possible gain obtained through the thermal isolation of the combustion chamber. Results derived from this study show that heat transfer has a negative effect on gross indicated efficiency ranging from −4% of the fuel energy (ṁfHv), at high engine speed and load, up to −8% ṁfHv, at low engine speed and load. In a second step, different mechanical limits are applied resulting in a gross indicated efficiency worsening from −1.4% ṁfHv up to −2.8% ṁfHv compared to the previous step when nominal constraints are applied. In these conditions, a temperature swing coating that covers the piston top and cylinder head is considered obtaining a maximum gross indicated efficiency improvement of +0.5% ṁfHv at low load and engine speed. Finally, NO x emissions are also included in the optimization obtaining the expected tradeoff between gross indicated efficiency and NO x . Under this optimization, cutting down the experimental emissions by 50% supposes a gross indicated efficiency penalty up to −8% ṁfHv when compared to the optimum combustion under nominal limits, while maintaining the experimental gross indicated efficiency allows to reduce the experimental emissions 30% at high load and 65% at low load and engine speed.

中文翻译：

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评估受限条件下的最佳燃烧

本工作研究了约束条件下直喷柴油机的最佳放热规律。为此，柴油发动机的零维预测模型与用于塑造放热规律的优化工具相结合，以优化某些输出（最大化总指示效率并最小化 NOx 排放），同时保持几个限制（机械限制，例如最大峰值压力和最大压力上升率）。在第一步中，该方法应用于不同的传热场景，不受限制，以评估通过燃烧室的热隔离获得的可能增益。本研究得出的结果表明，热传递对总指示效率有负面影响，范围为 -4% 的燃料能量 (ṁfHv)，在高发动机转速和负载下，高达 −8% ṁfHv，在低发动机转速和负载下。在第二步中，应用不同的机械限制导致总指示效率从 -1.4% ṁfHv 恶化到 -2.8% ṁfHv 与应用名义约束时的前一步相比。在这些条件下，覆盖活塞顶部和气缸盖的变温涂层被认为在低负载和发动机转速下获得了 +0.5% ṁfHv 的最大总指示效率改进。最后，NO x 排放也包括在获得总指示效率和NO x 之间的预期折衷的优化中。在这种优化下，与标称限制下的最佳燃烧相比，将实验排放量减少 50% 假设总指示效率损失高达 -8% ṁfHv，