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Vehicle Modeling Function으로 구현한 3차원 승용차의 후면 형상 변형이 공력성능에 미치는 영향에 관한 Parametric Study
송기선(Ki-Sun Song),강승온(Seung-On Kang),박훈일(Hoon-Il Park),이준호(Jun-Ho Lee),기정도(Jung-Do Kee),김규홍(Kyu-Hong Kim),이동호(Dong-Ho Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
This paper conducts a parametric study on the overall tendencies of changes of aerodynamic characteristics of a sedan depending on the rear body shape modifications through CFD simulation. In these research, the shapes of YF SONATA are represented by vehicle modeling function(VMF) which can generate and change the shapes of YF SONATA very quickly, compared with the realistic complicated model. The vehicle modeling functions are improved; several section functions and variables are added in order to generate the rear body shapes in detail. And the tendency of changes of the aerodynamic characteristics is analyzed. Finally, this paper suggests that the 3D shape of YF SONATA represented by VMF can reduce the overall time cost in designing a car because it takes so less time to know the ultimate car’s aerodynamic performance through proving the overall tendencies of the shape represented by VMF and the rear shape are very similar.
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.
승용차의 공기저항 감소를 위한 외부유동 시뮬레이션 분석
송기선(Ki-Sun Song),강승온(Seung-On Kang),박훈일(Hoon-Il Park),기정도(Jung-Do Kee),김규홍(Kyu-Hong Kim),이동호(Dong-Ho Lee) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
When a passenger car cruises, the characteristics of external fluid flows which pass near the car body vary depending on the aerodynamic shape of the car so that many kinds of aerodynamic drags occur as the results of this phenomenon. According to previous researches, it is well known that the aerodynamic drag affects the fuel efficiency of a car directly. Although this factor has played a powerful motivation for many researchers to conduct many cases of studies on reducing the aerodynamic drag of cars by using CFD simulations, it is true that the quality of the reliability of the CFD results was not reasonable because of the excessive simplifications of the car body shapes. For this reason, in order to overcome and reduce these kinds of limits, a feasibly meshed car body shape of YF SONATA of Hyundai Motors Company for CFD analysis was suggested and the aerodynamic characteristics were studied comprehensively by CFD analysis so that it was analyzed how the external fluid flows around the car body affect the aerodynamic characteristics of the car.
Synthetic jet을 이용한 승용차의 공력저항 감소에 대한 실험적 연구
박훈일(Hoon-Il Park),이영빈(Youngbin Lee),강승온(Seung-On Kang),송기선(Ki-Sun Song),기정도(Jung-Do Kee),이준호(Jun-Ho Lee),정형석(Hyoung-Seog Chung),장영일(Young Il Jang),김규홍(Kyu-Hong Kim),이동호(Dong-Ho Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
This paper describes drag reduction of a passenger car by using synthetic jet in wind tunnel test. For the reduction of aerodynamic drag, 11 synthetic jets are installed at the edge of the trunk on a 1/4 scale passenger car model to control the separation of the flow. Aerodynamic drag reduction is observed according to the jet location, jet direction and jet driving frequency. However, in case of the trunk sideward jet, aerodynamic drag is increased. As a result, drag reducing jet location, jet direction and jet driving frequency are revealed and it shows the possibility of aerodynamic drag reduction of a passenger car can be achieved by the synthetic jet.
능동형 리어 디퓨져 장치의 형상이 자동차 공기저항 감소 효과에 미치는 영향에 대한 연구
조준호(Jun-Ho Cho),강승온(Seung-On Kang),박훈일(Hoon-Il Park),송기선(Ki-Sun Song),기정도(Jung-Do Ki),이준호(Jun-Ho Lee),김규홍(Kyu-Hong Kim),이동호(Dong-Ho Lee) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
The main purpose of this paper is to examine the Influence of active translating rear diffuser configuration to aerodynamic drag reduction of automotive vehicle. Actively translating rear diffuser reduces aerodynamic drag of a fast cruising car. Actively translating rear diffuser is hidden under the trunk when a 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. 10 types of rear diffuser devices whose configuration is different were installed under the car body and Computational Fluid Dynamics (CFD) analyses were performed under moving ground and rotating wheel conditions. Finding a configuration which shows the best aerodynamic drag reduction performance is to explain the aerodynamic drag reduction mechanism of a car cruising at a high speed via an actively translating rear diffuser device. The diffuser device blocks low pressure underbody flow and raises pressure of it with diffusing process and then underbody flow and upperbody flow mix strongly, bringing about an aerodynamic drag reduction. Finally, aerodynamic drag of the car is reduced by an average of more than 7% with plate arc type diffuser, which helps to improve the fuel efficiency.
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.