Statistical analysis of the flow characteristics and cyclic variability using Proper Orthogonal Decomposition of highly resolved LES in internal combustion engines
Statistical analysis of the flow characteristics and cyclic variability using Proper Orthogonal Decomposition of highly resolved LES in internal combustion engines
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使用内燃机中高分辨率 LES 的适当正交分解对流动特性和循环变化进行统计分析
DOI：
10.1016/j.compfluid.2014.09.019
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发表时间：
2014
影响因子：
2.8
通讯作者：
R. Knappstein
中科院分区：
文献类型：
--
作者：
F. di Mare;R. Knappstein
本文用本征正交分解法（POD）分析了发动机内部流场的高分辨大涡模拟（LES）结果，目的是得到发动机内部主要速度结构的统计和模态特征。分析已进行的计算域的一个子集，被认为是特别相关的不稳定性的发展，导致循环的变化，位于附近的火花塞。该区域已被证明是充分代表的流场的动态，并已通过一个完全三维的，相位独立的POD检查。调查的基础上的速度的变化取决于当时的曲柄角位置的分析也表明，最强的变化出现在压缩和膨胀冲程。POD加权系数显示相同的行为，这并不令人惊讶。一方面，可以认为，通过POD在所考虑的控制体积中获得的简化系统可以方便地用于在预测的基础上导出用于识别异常周期的可能标准。然而，在另一方面，已经观察到，较弱的模式，忽略了在POD分析的基础上的本征模式的全局能量收敛，发挥了重要的作用，促进和支持循环的变化，也观察到在独立的实验研究。
The results of a highly resolved Large Eddy Simulation (LES) of the flow field in a motored engine have been analysed by means of Proper Orthogonal Decomposition (POD) with the objective of deriving a statistical and modal characterisation of the dominating velocity structures. The analysis has been conducted in a subset of the computational domain, deemed of particular relevance for the development of the instabilities leading to cyclic variability, located in the vicinity of the spark plug. This area has been demonstrated to be sufficiently representative of the dynamics of the flow field and has been examined by means of a fully three-dimensional, phase-independent POD.Investigations based on the analysis of the velocity’s variability depending on the prevailing crank angle position also show that the strongest variations appear during the compression and expansion strokes. The POD weighting coefficients display, not surprisingly, an identical behaviour. On one side, it can be argued that the reduced system obtained via POD in the considered control volume can be conveniently used to derive possibly criteria for the identification of anomalous cycles on a predictive basis. On the other side, however, it has been observed that weaker modes, neglected in the POD analysis on the basis of the global energetic convergence of the eigenmodes, play an important role in promoting and supporting cyclic variability, as also observed in independent experimental studies.
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