Computational fluid dynamics simulations are performed to investigate the combustion and emission characteristics of a diesel/natural gas dual-fuel engine. The computational fluid dynamics model is validated against experimental measurements of cylinder pressure, heat release rate, and exhaust emissions from a single-cylinder research engine. The model predictions of in-cylinder diesel spray distribution and location of diesel ignition sites are related to the behavior observed in measured and predicted heat release rate and emissions. Various distributions of diesel fuel inside the combustion chamber are obtained by modifying the diesel injection timing and the spray included angle. Model predictions suggest that the distribution of diesel fuel in the combustion chamber has a significant impact on the characteristics of heat release rate, explaining experimental observations. Regimes of combustion in the dual-fuel engine are identified. Turbulent flame speed calculations, premixed turbulent combustion regime diagram analysis, and high-temperature front propagation speed estimation indicated that the dual-fuel combustion in this engine was supported by successive local auto-ignition and not by turbulent flame propagation.

中文翻译：

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柴油-甲烷双燃料发动机大范围喷射正时燃烧特性和排放的数值研究

执行计算流体动力学模拟以研究柴油/天然气双燃料发动机的燃烧和排放特性。计算流体动力学模型根据单缸研究发动机的气缸压力、放热率和废气排放的实验测量值进行了验证。缸内柴油喷雾分布和柴油点火点位置的模型预测与在测量和预测的热释放率和排放中观察到的行为有关。通过改变柴油喷射正时和喷雾夹角，得到燃烧室内柴油的各种分布。模型预测表明，柴油在燃烧室中的分布对放热率特性有显着影响，解释实验观察。识别双燃料发动机中的燃烧状态。湍流火焰速度计算、预混湍流燃烧状态图分析和高温前沿传播速度估计表明，该发动机的双燃料燃烧是由连续局部自燃支持，而不是由湍流火焰传播支持。