The Role of CFD Combustion Simulation in Diesel Burner Development

Diesel burners introduce combustion of diesel fuel to raise exhaust gas temperature to Diesel Oxidization Catalyst (DOC) light-off or Diesel Particulate Filter (DPF) regeneration conditions, thereby eliminating the need of engine measures such as post-injections. Such diesel combustion requirement nevertheless poses challenges to burner development especially in combustion control and risk mitigation of DPF material failure. In particular, burner design must satisfy good soot distribution and heat distribution at DPF front face after meeting minimum requirements of ignition, heat release, and backpressure. In burner development, Computational Fluid Dynamics (CFD) models have been developed based on commercial codes for burner thermal and flow management with capability of predicting comprehensive physical and chemical phenomena including turbulence induced mixing, fuel injection, fuel droplet transport, diesel combustion, radiation, conjugate heat transfer and etc. These models, in combination with validation tests, have been proven valuable in appraising overall system performance and improving thermal mixing performance of multiple mixer and liner configurations. Two commercial CFD codes of Fluent and Star-CD are used in this development with STAR-CD having been applied in all phases of development including sub-model studies, sensitivity studies and full combustion simulations. Encouraging validations with test data have been achieved. Fluent is being used for benchmark purpose and developed as an alternative tool. Thus far, Fluent can predict similar results and design directions within the scope of multiple cases studies in this paper.