The potential of a progress variable formulation for predicting autoignition and subsequent kernel development in a nonpremixed\r\njet flame is explored in the LES (Large Eddy Simulation) context. The chemistry is tabulated as a function of mixture fraction and\r\na composite progress variable, which is defined as a combination of an intermediate and a product species. Transport equations\r\nare solved for mixture fraction and progress variable. The filtered mean source term for the progress variable is closed using a\r\nprobability density function of presumed shape for the mixture fraction. Subgrid fluctuations of the progress variable conditioned\r\non the mixture fraction are neglected. A diluted hydrogen jet issuing into a turbulent coflow of preheated air is chosen as a test case.\r\nThe model predicts ignition lengths and subsequent kernel growth in good agreement with experiment without any adjustment\r\nof model parameters. The autoignition length predicted by the model depends noticeably on the chemical mechanism which the\r\ntabulated chemistry is based on. Compared to models using detailed chemistry, significant reduction in computational costs can\r\nbe realized with the progress variable formulation.
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