Abstract Cold start is one of the most problematic combustion phases for diesel engines. During this phase, a large proportion of pollutants are produced within the cylinder due to misfiring and incomplete combustion due to the low engine temperatures. Furthermore, exhaust after-treatment devices work inefficiently since their minimum operation temperatures cannot be reached. In addition to this, at temperatures below 0 °C the possibility of continuous misfiring could actually impede the engine start. Ambient temperature is one of the most important factors affecting the diesel engine cold startability. The aim of this study is to improve diesel engine startability under low temperatures by vortex tubes. A vortex tube was used to increase the intake air temperature in a six cylinders, four stroke and direct injection diesel engine of a truck. The hot air obtained from the hot outlet of the vortex tube was mixed with the air coming from the inlet of the intake manifold and the warmer air was sent to the cylinders. The compressed air required for the operation of the vortex tube was provided from the air tank of the compressed-air brake system of the truck. The effects of variation in ambient temperature on the engine cranking speed and in-cylinder pressure were analyzed and presented. Experiments were conducted for ambient air temperatures of − 5 , 0 and + 4 °C. It was found that the reduction in ambient temperature resulted in prolonged cranking periods along with the longer time taken to reach idling speed as well as increased combustion instability for the engine without vortex tube. The use of the vortex tube increased the intake air temperature, which decreased durations of engine starting–cranking, cranking–idling, and idling–stabling. These results indicate that the cold starting performance of the diesel engine could be improved by using vortex tubes.

中文翻译：

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涡流管改善柴油机低温启动性

摘要 冷启动是柴油发动机最有问题的燃烧阶段之一。在此阶段，由于发动机温度低导致的不点火和不完全燃烧，气缸内会产生很大比例的污染物。此外，排气后处理装置由于无法达到其最低操作温度而工作效率低下。除此之外，在低于 0 °C 的温度下，持续失火的可能性实际上可能会阻碍发动机启动。环境温度是影响柴油机冷启动性的最重要因素之一。本研究的目的是通过涡流管提高柴油发动机在低温下的启动性。涡流管用于提高卡车的六缸四冲程直喷柴油发动机的进气温度。从涡流管的热出口获得的热空气与来自进气歧管入口的空气混合，较暖的空气被送到气缸。涡流管运行所需的压缩空气由卡车压缩空气制动系统的储气罐提供。分析并展示了环境温度变化对发动机曲轴转速和缸内压力的影响。实验是针对 - 5、0 和 + 4 °C 的环境空气温度进行的。发现环境温度的降低导致起动时间延长以及达到怠速所需的时间更长，以及没有涡流管的发动机的燃烧不稳定性增加。涡流管的使用提高了进气温度，这减少了发动机启动 - 盘车、盘车 - 怠速和怠速 - 稳定的持续时间。这些结果表明使用涡流管可以提高柴油机的冷启动性能。