An Investigation of the Relationship Between Measured Intake Temperature, BDC Temperature, and Combustion Phasing for Premixed and DI HCCI Engines
An Investigation of the Relationship Between Measured Intake Temperature, BDC Temperature, and Combustion Phasing for Premixed and DI HCCI Engines
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DOI：
10.4271/2004-01-1900
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发表时间：
2004-06
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通讯作者：
Magnus Sjöberg;J. Dec
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文献类型：
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作者：
Magnus Sjöberg;J. Dec
燃烧相位是HCCI运行必须解决的一个重要问题。可以调节进气温度以在期望的曲柄角处实现点火。然而，在进气过程中的热传递将使有效进气温度不同于在转轮中测量的温度。此外，取决于发动机速度和端口配置，动态流动效应引起不同程度的充量加热。另外，来自前一循环的残余物可对压缩冲程开始时的充气温度具有显著影响。最后，燃料的直接喷射将影响充气温度，因为蒸发需要热量。本研究采用Ricardo的WAVE，结合实验和循环模拟，系统地研究了这些影响。结果表明，由于在诱导期内的热传递发生的充电加热/冷却的量可以计算从容积效率的变化。与直接喷射的燃料的汽化相关联的进气冷却量随着喷射正时而变化，并且可以与容积效率相关。提出了一种估算进气冲程结束时混合气温度的简单方法。给出了几个例子，这个程序可以用来解释实验观察到的点火HCCI操作，在进气冲程结束时的充电温度有关的燃烧相位。异辛烷被用作汽油替代品，因为它有助于与化学动力学模型进行比较，在这种情况下，详细的异辛烷机制来自LLNL。虽然该程序是为HCCI操作开发的，但它也可以应用于其他类型的发动机。例如，在进气过程期间发生的进气温度的变化对于SI发动机中爆震的发生和柴油发动机中NOx的形成都是重要的。
Combustion phasing is one important issue that must be addressed for HCCI operation. The intake temperature can be adjusted to achieve ignition at the desired crank angle. However, heat-transfer during induction will make the effective intake temperature different from the temperature measured in the runner. Also, depending on the engine speed and port configuration, dynamic flow effects cause various degrees of charge heating. Additionally, residuals from the previous cycle can have significant influence on the charge temperature at the beginning of the compression stroke. Finally, direct injection of fuel will influence the charge temperature since heat is needed for vaporization. This study investigates these effects in a systematic manner with a combination of experiment and cycle simulation using WAVE from Ricardo. The results show that the amount of charge heating/cooling that occurs due to heat-transfer during the induction period can be computed from changes in the volumetric efficiency. The amount of charge cooling associated with vaporization of directly injected fuel changes with injection timing and can be related to the volumetric efficiency. A simple procedure for estimating the charge mixture temperature at the end of the intake stroke is presented. Several examples are given where this procedure can be used beneficially to explain experimental observations for fired HCCI operation where the charge temperature at the end of the intake stroke was related to the combustion phasing. Iso-octane was used as a gasoline surrogate since it facilitates comparison with chemical-kinetics models, in this case the detailed iso-octane mechanism from LLNL. Although this procedure is developed for HCCI operation, it can be applied to other types of engines as well. For example, the changes to the charge temperature that occur during the induction process are important for both tH'e occurrence of knock in Sl engines and NO x formation in Diesel engines.