Modelling a Dual-Fuelled Multi-Cylinder HCCI Engine Using a PDF Based Engine Cycle Simulator
Modelling a Dual-Fuelled Multi-Cylinder HCCI Engine Using a PDF Based Engine Cycle Simulator
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使用基于 PDF 的发动机循环模拟器对双燃料多缸 HCCI 发动机进行建模
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发表时间：
2004
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通讯作者：
F. Mauss
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作者：
A. Bhave;M. Kraft;L. Montorsi;F. Mauss
在自燃特性(辛烷值)差异较大的双燃料均质压燃发动机上运行是控制均质压燃运行的一种方法。对一台6缸斯堪尼亚卡车发动机燃用正庚烷和异辛烷，在均质压燃模式下运行时，辛烷值对燃烧、排放和发动机性能的影响进行了数值研究，并与Olsson等人的测量结果进行了比较。[SAE 2000-01-2867]。为了正确地模拟均质压燃发动机的运行，我们实现了一个基于概率密度函数(PDF)的随机反应器模型(包括详细的化学动力学和对组成和温度的不均匀的考虑)，并与基于一维流体力学的发动机循环模拟器GT-POWER相结合。这种耦合被证明是理解燃烧现象以及发动机循环固有的气体动力学过程的理想方法。发动机气缸内的对流换热被建模为一个随机跳跃过程，并考虑了波动和流壁相互作用的影响。湍流混合采用Curl的聚结-弥散模型描述。在基本工况下，缸内压力、点火正时、CO、HC和NOx排放的预测值与实测值之间有很好的一致性。先进的基于PDF的发动机循环模拟器的性能明显优于广泛使用的基于同质模型的全循环发动机模拟器。通过与测量结果的比较，较好地预测了着火曲轴转角和燃烧持续期等燃烧特性随辛烷值变化的趋势。该集成模型提供了可靠的预测缸内温度，CO，HC以及NOx排放的广泛范围的辛烷值研究。
Operating the HCCI engine with dual fuels with a large difference in auto-ignition characteristics (octane number) is one way to control the HCCI operation. The effect of octane number on combustion, emissions and engine performance in a 6 cylinder SCANIA truck engine, fuelled with n-heptane and isooctane, and running in HCCI mode, are investigated numerically and compared with measurements taken from Olsson et al. [SAE 2000-01-2867]. To correctly simulate the HCCI engine operation, we implement a probability density function (PDF) based stochastic reactor model (including detailed chemical kinetics and accounting for inhomogeneities in composition and temperature) coupled with GT-POWER, a 1-D fluid dynamics based engine cycle simulator. Such a coupling proves to be ideal for the understanding of the combustion phenomenon as well as the gas dynamics processes intrinsic to the engine cycle. The convective heat transfer in the engine cylinder is modeled as a stochastic jump process and accounts for the fluctuations and fluid-wall interaction effects. Curl's coalescence-dispersion model is used to describe turbulent mixing. A good agreement is observed between the predicted values and measurements for in-cylinder pressure, auto-ignition timing and CO, HC as well as NOx emissions for the base case. The advanced PDF-based engine cycle simulator clearly outperforms the widely used homogeneous model based full cycle engine simulator. The trends in combustion characteristics such as ignition crank angle degree and combustion duration with respect to varying octane numbers are predicted well as compared to measurements. The integrated model provides reliable predictions for in-cylinder temperature, CO, HC as well as NOx emissions over a wide range of octane numbers studied.