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A flow analysis method with quick turnaround time has been studied for application to flows in the engine compartment of vehicles. In this research, a rapid modeling method based on the Cartesian mesh system was developed to obtain flow field information quickly. With this modeling method, the original shape is approximated by many small cubic cells, allowing automatic mesh generation in significantly less time. Moreover, a hierarchical mesh system that reduces the total number of meshes has been introduced. This multi-level mesh system is also highly capable of representing shapes in detail. Another important issue in flow calculations in the engine bay is the treatment of the boundary conditions such as the radiator and cooling fan. With the proposed method, the fluid dynamics characteristics of such components are measured, and characteristics such as the pressure loss/gain and the rotational vector of the fan are reflected in the flow field as empirical models.

Both the external and internal flows of cars are simulated simultaneously. A third-order upwind-difference scheme is used in these simulations. Computational grids are generated by a multi-block transformation and a trans-finite method. Engine compartments are modeled by grid systems but the heat exchanger is simulated as a pressure loss proportional to the dynamic pressure of the flow passing through it. First, the flow for a very simple test model with no wheels and nothing in its engine compartment is simulated and compared with experimental results in order to validate a simulation method for the engine compartment. Pressure distributions on the inner surfaces agree very well with measured values, while pressure distributions on the external surfaces show reasonable agreement except for the roof end and the leading edge of the floor. The predicted drag coefficient is 7% larger than the experimental value. This method is next applied to a prototype car.

The acceleration performance of a car equipped with a turbocharged, intercooled engine is affected by the volume of cooling air that flows through the core of the intercooler. Additionally, the volume of cooling air entering the intercooler is influenced by the configuration of the air intake provided in the exterior design. Therefore, in planning a new model it is very important to be able to predict acceleration performance, at an early stage of the vehicle development process, in relation to vehicle styling and engine specifications. The procedures employed so far to predict the volume of air flowing through the intercooler have included two-dimensional finite-difference methods and a panel method. However, because of their simple nature, none of these approaches has provided sufficiently accurate results. This paper presents a new numerical analysis method that has been developed to overcome this problem.

It is very difficult to measure and analyze the internal flows of torque converters because of their complicated construction. In this report, an attempt is made to calculate the characteristics of torque converters by the combination of a one-dimensional flow theory and a finite difference calculation. From the computed results however, it is significant to note, that this experimental result is more useful as a rational design procedure than the pure angular momentum theory.

The computation of the Navier-Stokes equations through the three torque converter components (i.e., the pump, the turbine and the stator) is shown. A third-order-upwind scheme is used in the computation. The flow in each component is first calculated individually. Then, the calculation results for each outlet condition are used as the inlet condition of the next component, and the flow in each component is calculated again. This iterative procedure is terminated when the loss of flow pressure in the three components reaches a steady state. The torque converter performance predicted with this method agrees well with experimental data.