Abstract
A series calculation method from injector nozzle internal flow to in-cylinder combustion in diesel engines has been developed. In this study, the predicted in-cylinder pressure, heat release rate and NO concentration are compared with the experimental results on several conventional operating conditions and a higher EGR rate condition with high boost pressure and high injection pressure. The pressure and heat release rate histories are in reasonable agreement with the experiments, but the NO concentration is underestimated especially on the higher EGR rate condition. Therefore the investigation for improving the quantitative accuracy of NO concentration is performed. The PDF (probability density function) method is able to estimate the real mean reaction rate containing the reaction rate fluctuation by turbulence. However the PDF calculation is prohibitive on the computer resources. In this study, the PDF method only for the calculation of NO formation is developed for striking a balance between improvement of calculation accuracy and calculation cost. The result shows that the effect of reaction rate fluctuation on NO formation has a little on conventional operating conditions, but increases with decreasing the combustion temperature.
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