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The influence of a typical stator and support arm on the performance of an automotive engine cooling module is evaluated. Measured lift (CL) and the drag (CD) coefficients are compared for a typical stator and support arm under real unsteady inlet conditions. These inlet conditions are based on Laser Doppler Velocimetry (LDV) data taken in the flow downstream of an automotive cooling fan. The quality of the experimental results is assessed upon comparison with the well-established flat plate data. It is found that inlet conditions dramatically affect the aerodynamic performance of both the stator and the support arm. A suitable range of inlet conditions on which to base the design is presented. The second objective of the current study is to establish accurate numerical simulation guidelines for future fan designs. Various turbulence models are evaluated based on comparison with experimentally measured data for a stator and a support arm at various angles of attack.

A numerical model to assess the aerodynamic performance of typical automotive cooling fan stators or support arms is presented. Under real operating conditions, the flow over stators or support arms resembles bluff body flow. Hence, the time and spatial resolution are selected based on previous numerical simulations for the flow around a normal flat plate. Turbulence modeling is based on the Unsteady Reynolds-averaged Navier-Stokes (URANS) equations retaining the Boussinesq eddy-viscosity hypothesis. The ability of the URANS model to predict the periodic nature of the flow is demonstrated here. Furthermore, comparison with experimental data shows that the proposed numerical model can predict the global flow parameters, namely lift and drag within good accuracy. As a first attempt to assess the interaction of the cooling fan with its system environment, the proposed numerical model is expanded to model the interaction of the fan blades with the adjacent stators or support arms.

The effects of the physical and chemical properties of biodiesel fuels on the combustion process and pollutants formation in Direct Injection (DI) engine are investigated numerically by using multi-dimensional CFD models. In the current study, methyl butanoate (MB) and n-heptane are used as the surrogates for the biodiesel fuel and the conventional diesel fuel. Detailed kinetic chemical mechanisms for MB and n-heptane are implemented to simulate the combustion process. It is shown that the differences in the chemical properties between the biodiesel fuel and the diesel fuel affect the whole combustion process more significantly than the differences in the physical properties. While the variations of both the chemical and the physical properties between the biodiesel and diesel fuel influence the soot formation at the equivalent level, the variations in the chemical properties play a crucial role in the NO emissions formation.

The current work aims to develop a reliable numerical model simulating the depletion and decomposition process of urea-water solution (UWS) droplets injected in a hot exhaust stream as experienced in an automotive urea-based selective catalytic reduction (SCR) system. The depleting process of individual UWS droplets in heated environment is simulated using a multicomponent vaporization model with separate depletion law for each component. While water depletion is modeled as a vaporization process, urea depletion from the UWS droplet is modeled using two different approaches. The first approach models urea depletion as a vaporization process with an experimentally determined saturation pressure. The second approach models urea depletion as a direct thermolysis process from molten urea to ammonia and isocyanic acid using various sets of kinetic parameters. Comparison with experimental data shows the superiority of modeling urea depletion as a vaporization process.

Improving the NOx removal efficiency of an automotive urea-based SCR system requires optimized injection system to minimize wall deposition while providing uniform distribution of exhaust gases and reductant mixture at the entrance of the catalyst. The focus of the current study is to develop and validate a three-dimensional computational model capable of simulating the urea-water-solution (UWS) spray/wall interaction. The interaction between the injected UWS spray droplets and the surrounding gas is modeled using the Eulerian-Lagrangian approach,. A specially developed multicomponent vaporization model is implemented to simulate the depletion mechanism of individual UWS droplets. The spray/wall interaction mechanism involves spray/wall impingement and wall film formation. While the spray/wall impingement mechanism is modeled using a standard criteria, the O'Rourke and Amsden model for wall film formation is modified to account for the multicomponent nature of the UWS spray.