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Technical Paper

Multidimensional Modeling of a Six-Mode Diesel Test Cycle using a PDF Combustion Model

In this study, a new combustion model for simulating the diesel combustion process is introduced. This model was verified by comparing numerical simulations to experimental data for a six-mode test cycle using a Caterpillar 3400 series engine. Additional comparisons are made for baseline cases for both a Caterpillar 3500 series engine and a Sandia optical access engine. In the combustion model, reactions limited by diffusion are modeled using a probability density function (PDF) model. For kinetically limited (premixed) combustion, an Arrhenius rate is used. To include effects of temperature fluctuations, this reaction rate is weighted by a temperature probability density function. A transport equation for premixed fuel was implemented to transition between the premixed and diffusion burning modes. The ratio of fuel in a computational cell that is premixed is used to determine the combustion mode.