Development of the Integrated Process for Torque Converter Design and Analysis

Development of TDOS (Torque converter Design Optimization System), an integrated design process, is presented. The main functional groups of TDOS are torque converter geometry designer, 3D CFD analysis module, and design optimizer. For the geometry design, an in-house code BPG (Blade Profile Generator), is employed to create the 2D torus and 3D blade coordinates with given design constraints. To obtain an accurate performance results, an automated CFD analysis module is created which includes 3D geometry modeling, mesh generation, solving and result analysis. All CFD parameters that affect the accuracy of solution such as mesh size, simulation scheme and boundary conditions are predefined for the automated CFD analysis. The optimal parameters for CFD analysis are determined from the previous study of mass-produced torque converters. Having automated the geometry design and CFD analysis process, an optimization procedure of torque converter geometry is developed. A simple-to-use GUI is introduced to enhance the accessibility and usability of TDOS. To demonstrate the capability of TDOS, following two cases are considered: 1) design parameter study on the hydraulic performance of torque converter and 2) blade profile optimization to satisfy a given performance target. The results show that the design of torque converter can be optimized to meet the target performance at 1/30 the man-hour cost compared to the traditional way. In general, further reduction of computational cost can be expected since the automated process eliminates additional cost that can rise from possible human error. With fast turn-around time, design engineers can concentrate on the design task with quick review of their designs. This improves the overall efficiency of torque converter development. INTRODUCTION Torque converter transfers the torque and power from engine to transmission by the hydraulic operation of transmission oil. Despite of its ability to provide good acceleration performance and absorb excessive vibration, its mechanical efficiency is relatively low. Nowadays, a few new techniques are in use to overcome the low efficiency. The two representative methods are 1) the application of the locking clutch of the turbine to the pump and 2) the optimized design of shape of torus and blades to enhance the hydraulic performance. The first technique is very effective when vehicle is moving at constant and a little bit of high speed. The second technique is effective at the wider range of vehicle speed, but not easy to obtain an optimized shape since no less than 20 design parameters are involved. Typically, several torque converters are designed and tested by CFD and experiment until the target performance is met. Due to increasing computing power, CFD analysis becomes a very popular tool since it is more accurate than one-dimensional method[1] and more effective than experiments in terms of time and cost limitation. However, to apply CFD analysis to engineering design, design engineers should know about the relevant knowledge such as design theory, geometry modeling, CFD theory, and optimization methods. Especially, advanced CFD theory and knowledge are taking quite a bit of time to be proficient. This is the main reason why an automated design process is needed. The integrated design process, named as TDOS(Torque converter Design Optimization System),is presented to offer the followings: 1) the automated procedure of geometry designer and CFD analysis, 2) accurate prediction of performance, 3) design optimizer, and 4) intuitive and simple-to-use GUI based on Excel.