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Using non-viscosity dynamic structure Large Eddy Simulations (LES) turbulence model, spray=induced turbulence is investigated on a number of different Computational Fluid Dynamics (CFD) grids of varying mesh sizes (from 0.5 to 2 mm mesh). Turbulent flow is induced inside a quiescent chamber by liquid fuel spray and then left to decay after end of injection by virtue of its molecular viscosity and turbulent dissipation. Coherent structures (CS) of this turbulent flow are constructed and visualized using λ2 definition. Using CS, analysis is performed on the turbulent flow around the liquid spray jet. These CS from LES are then compared against the results from RANS calculations as well. The visualization of CS helps to explain the mechanism of fuel-air mixing obtained from LES results and its difference with RANS calculations.

Numerical investigation is carried out to explore various strategies of combustion mode switching in a diesel engine operating at high power. Numerical results are compared with high power single cylinder (CAT 3401E) experiments for combustion phasing and emission characteristics. In this study CFD calculations are carried out using the KIVA CFD code with Large Eddy Simulation turbulence model and Direct Chemistry Solver sub-models. The advanced turbulence and combustion sub-models enabled more realistic visualization of the effects of single-cycle mode switching on in-cylinder flow structures, fuel-air mixing behavior and combustion phasing. Two circumstances of mode switch are presented in this study. Mode switches are performed from traditional High Temperature Combustion to early injection PCCI combustion and vice versa. In this investigation several aspects of combustion control are investigated.

Numerical investigation is carried out in order to explore diesel combustion using advanced turbulence and combustion models. Turbulence is modeled by one-equation non-viscosity dynamic structure Large Eddy Simulation (LES) model. Sub-grid fuel-air mixing is calculated using a dynamic scale similarity sub-grid scalar dissipation model to represent the local state of combustion. Fuel-air mixing time scale is used in order to determine the local in-homogeneity and rate of mixing of fuel and air. Diesel combustion is studied and compared with experimental results for high power diesel engine setup at different conditions representing both low temperature combustion and traditional high temperature combustion regimes. Further studies are carried out in diesel engine to investigate in-cylinder fuel air mixing and the onset of ignition.

Diesel engine combustion is simulated using Large Eddy Simulation (LES) with a multi-mode combustion (MMC) model. The MMC model is based on the combination of chemical kinetics, chemical equilibrium, and quasi-steady flamelet calculations in different local combustion regimes. The local combustion regime is identified by two combustion indices based on the local temperature and the extent of mixture homogeneity. The LES turbulence model uses the dynamic structure model (DSM) for sub-grid stresses. A new spray model in the LES context is used, and the Reynolds-averaged Navier-Stokes (RANS) based wall model is retained with the LES derived scales. These models are incorporated in the KIVA3V-ERC-Release 2 code for engine combustion simulations. A wide range of diesel engine operating conditions were chosen to validate the combustion model.

Preliminary empirical and modeling analyses are conducted to evaluate the energy efficiency of in-cylinder and external fuel injection strategies and their impact on the energy required to enable diesel particulate filter (DPF) regeneration for instance. During the tests, a thermal wave that is generated from the engine propagates along the exhaust pipe to the DPF substrate. The thermal response of the exhaust system is recorded with the thermocouple arrays embedded in the exhaust system. To implement the external fuel injection, an array of thermocouples and pressure sensors in the DPF provide the necessary feedback to the control system. The external fuel injection is dynamically adjusted based on the thermal response of the DPF substrate to improve the thermal management and to reduce the supplemental energy. This research intends to quantify the effectiveness of the supplemental energy utilization on aftertreatment enabling.