Fuel conversion efficiency improvements in a highly boosted spark-ignition engine with ultra-expansion cycle
Fuel conversion efficiency improvements in a highly boosted spark-ignition engine with ultra-expansion cycle
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DOI：
10.1016/j.enconman.2015.06.078
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发表时间：
2015-10-01
影响因子：
10.4
通讯作者：
Yin, Tao
中科院分区：
文献类型：
--
作者：
Li, Tie;Zheng, Bin;Yin, Tao
将进气增压、进气道燃油喷射（PFI）、火花点火（SI）的四缸发动机改造成三缸发动机，外缸工作在传统的四冲程循环，内缸只工作在膨胀和排气冲程。利用原机的试验数据对发动机循环模拟模型进行标定和验证后，对超膨胀循环三缸发动机的性能进行了数值研究。与原发动机相比，设计合理的超膨胀循环发动机最常用工况下的燃油消耗量可提高9-26%，工作图上的低燃油消耗区大大扩大。尽管如此，超膨胀循环发动机需要更高的进气增压以避免节气门全开（WOT）性能的显著下降，并且必须减小燃烧气缸的压缩比以避免爆震燃烧。然而，尽管压缩比减小，但总膨胀比随着内缸中的工作气体的额外膨胀而增加到13.8。与传统发动机相比，在大部分负载范围内，超膨胀循环的理论热效率因此提高了4.0%以上。能量平衡分析表明，在中高负荷下，燃烧效率的提高、排气能量的减少以及内缸的额外膨胀功是提高燃油转化效率的主要原因。在低负荷时，泵气损失和排气能量的减少是降低燃油消耗的主要原因，而内缸中的额外膨胀功的贡献变得很小。(C)2015爱思唯尔有限公司版权所有。
A four-cylinder, intake boosted, port fuel injection (PFI), spark-ignition (SI) engine is modified to a three-cylinder engine with the outer two cylinders working in the conventional four stroke cycle and with the inner cylinder working only with the expansion and exhausting strokes. After calibration and validation of the engine cycle simulation models using the experimental data in the original engine, the performance of the three-cylinder engine with the ultra-expansion cycle is numerically studied. Compared to the original engine, the fuel consumptions under the most-frequently operated conditions are improved by 9-26% and the low fuel consumption area on the operating map are drastically enlarged for the ultra-expansion cycle engine with the proper design. Nonetheless, a higher intake boosting is needed for the ultra-expansion cycle engine to circumvent the significant drop in the wide-open-throttle (WOT) performance, and compression ratio of the combustion cylinder must be reduced to avoid knocking combustion. Despite of the reduced compression ratio, however, the total expansion ratio is increased to 13.8 with the extra expansion of the working gas in the inner cylinder. Compared to the conventional engine, the theoretical thermal efficiency is therefore increased by up to above 4.0% with the ultra-expansion cycle over the most load range. The energy balance analysis shows that the increased combustion efficiency, reduced exhaust energy and the extra expansion work in the inner cylinder are the primary contributions to improving the fuel conversion efficiency at the middle and high loads. At the low load, reductions in the pumping loss and exhaust energy are the main causes of the reduced fuel consumption, while the contribution of the extra expansion work in the inner cylinder becomes small. (C) 2015 Elsevier Ltd. All rights reserved.