ABSTRACT

The present study aims to investigate the effect on combustion, emission, and spray characteristics with the variation of the nozzle hole diameters (NHD) in a diesel engine. For this a CFD 3D model is developed for a four-stroke diesel engine fueled with neat diesel and three different NHD, i.e., 0.20 mm, 0.26 mm, and,] 0.30 mm. The CFD 3D models were effectively able to predict the turbulence and turbulent-flame propagation interaction, chemistry involved in combustion processes, and the dissociation and reassociation of chemical species. For the model validation, the combustion characteristics of the CRDI-VCR engine are used. The validation results showed good compatibility having the relative error within the range. The analysis showed that increasing the nozzle hole diameter resulted in the decrease of the in-cylinder pressure by about 8.31% and 31.93%, respectively, for 0.26 mm and 0.30 mm diameter compared to 0.20 mm. The AHRR also showed a similar trend with a decrease of about 11.82% and 42.18%, respectively, for 0.26 mm and 0.30 mm diameter as compared to 0.20 mm. Subsequently, the increase in nozzle diameter showed an increase in HC and CO emissions but a decrease in NOx emissions. The CO emissions increase by about 0.65% and 5.08% and HC emissions increase by about 29.90% and 60.13% respectively for 0.26 mm and 0.30 mm diameter compared to 0.20 mm. While the NOx emission reduces by about 41.18% and 70.58% respectively for 0.26 mm and 0.30 mm diameter as compared to 0.20 mm. The effect of different nozzle diameters on spray characteristics is analyzed and verified from previous studies. The increase in nozzle diameter showed an increase in liquid penetration length, breakup length, and SMD. Also, the present study shows the possibilities of the CFD models for the simulation of engines employing different fuels and operative conditions.

摘要

本研究旨在研究柴油机喷嘴孔径 (NHD) 的变化对燃烧、排放和喷雾特性的影响。为此，开发了一个 CFD 3D 模型，用于以纯柴油和三种不同 NHD（即 0.20 毫米、0.26 毫米和] 0.30 毫米）为燃料的四冲程柴油发动机。CFD 3D 模型能够有效地预测湍流和湍流-火焰传播相互作用、燃烧过程中涉及的化学以及化学物质的分解和再结合。对于模型验证，使用了 CRDI-VCR 发动机的燃烧特性。验证结果表明兼容性良好，相对误差在范围内。分析表明，增加喷孔直径导致缸内压力降低约8。与 0.20 毫米相比，0.26 毫米和 0.30 毫米直径分别为 31% 和 31.93%。AHRR 也显示出类似的趋势，与 0.20 毫米相比，0.26 毫米和 0.30 毫米直径的 AHRR 分别下降约 11.82% 和 42.18%。随后，喷嘴直径的增加表明 HC 和 CO 排放量增加，但 NOx 排放量减少。与 0.20 毫米相比，0.26 毫米和 0.30 毫米直径的 CO 排放量分别增加约 0.65% 和 5.08%，HC 排放量分别增加约 29.90% 和 60.13%。与 0.20 毫米相比，直径为 0.26 毫米和 0.30 毫米的 NOx 排放量分别减少了约 41.18% 和 70.58%。从以前的研究中分析和验证了不同喷嘴直径对喷雾特性的影响。喷嘴直径的增加表明液体渗透长度的增加，断裂长度和 SMD。此外，本研究还展示了 CFD 模型用于模拟使用不同燃料和工作条件的发动机的可能性。