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능동형 리어 디퓨져 장치를 이용한 고속 주행 시 승용차의 공기저항 감소 기법에 관한 연구
조준호(Jun-Ho Cho),강승은(Seung-On Kang),박훈일(Hoon-Il Park),송기선(Ki-Sun Song),기정도(Jung-Do Ki),김규홍(Kyu-Hong Kim),이동호(Dong-Ho Lee) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
This paper suggests a technique that reduces aerodynamic drag of a fast cruising passenger car using actively translating rear diffuser. Actively translating rear diffuser is hidden under the trunk when a passenger car is parked and is driven slowly. And it slides out from under rear car body only at high speed driving condition not to ruin the external design of the car. 5 types of rear diffuser devices whose slid out lengths are ranging from 200mm to 450mm were installed under the car body and Computational Fluid Dynamics (CFD) analyses were performed under moving ground and rotating wheel conditions. The main purpose of this study is to explain the aerodynamic drag reduction mechanism of a passenger car cruising at a high speed via an actively translating rear diffuser device and find a length which shows the best aerodynamic performance. The diffuser device raises pressure of underbody flow with diffusing process and then underbody flow and upperbody flow mix strongly. They make strong vortices and the vortices hit the rear surface of the trunk, bringing about an aerodynamic drag reduction. Finally, aerodynamic drag of the passenger car is reduced by an average of more than 5%, which helps to improve the fuel efficiency.
승용차의 공기저항 감소를 위한 후면 형상의 공력 최적설계
송기선(Ki-sun Song),강승은(Seung-on Kang),전상욱(Sang-ook Jun),박훈일(Hoon-il Park),기정도(Jung-do Kee),김규홍(Kyu-hong Kim),이동호(Dong-ho Lee) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
This study proposed an aerodynamically optimized outer shape of a sedan using Artificial Neural Network (ANN) and focused its attention on modifying the rear body shapes of the sedan. To determine the optimization variables, the unsteady flow field around the sedan cruising very fast was scrutinized by CFD simulation, and thereby, the fluctuations of the drag coefficient (CD) and pressure around were confirmed. Regarding the baseline result for CFD, 6 local parts of the end from the sedan were chosen as the design variables for the optimization. Moreover, the ANN approximation model was established with 64 experimental points generated by the D-optimal methodology. As a result, an aerodynamically optimized shape for the rear end of the sedan in which the drag was minimal was proposed with its aerodynamic performance improving by about 5.517%, compared with that of the baseline. Finally, it is expected that in the proper range of shape modifications for a rear body, the aerodynamic performance of a sedan can be enhanced, and thereby, the fuel efficiency of the sedan can be improved. The YF SONATA, a sedan manufactured by Hyundai Motors Company, played a major role in this research as the baseline vehicle.