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Vehicle Aerodynamic Performance Assessment through Scaled Clay Model Test and CFD Simulation
하종백(JongPaek Ha),김은석(EunSeok Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The challenge today is to be able to simulate accurately very complex fluid phenomena and to get CFD(Computational Fluid Dynamics) results fast in order to effectively apply them in the dynamic design development. Also, simultaneously, aerodynamic wind tunnel test(WTT) has to be executed during the development. This paper is on the ways of evaluating and validating the vehicle aerodynamic performances by CFD and scaled clay model aerodynamic wind tunnel test. These initial assessments and those validation methodologies has being developed by engineering viewpoints. Through these engineering approaches, we can provide the vehicle exterior design guideline by optimization on exterior design. And, also through the co-relation with simulation and test result, we can provide more upfront engineering deliverables to drive vehicle performance improvements. By these simultaneous engineering assessments, the numerical and modeling errors in simulation can be corrected through the actual vehicle test, and the test scenarios can be minimized and optimized through simulation guidelines.
하종백(JongPaek Ha),김형철(HyungChel Kim),구병모(ByungMo Kee) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_3
The base HVAC(Heating, Ventilation, and Air Conditioning) system of GMDAT(General Motors Daewoo Automotive & Technology) small car with four different mode - Vent, Foot, Defrosting, and Bi-level Mode - has been studied in this paper. The main objective of this analysis is to look at the flow field inside the HVAC system including each of the ducts and to find out the thermo-fluid dynamic performance at the early stage of development in terms of the flow distribution and pressure drop, With these sorts of initial assessments through vehicle development process, the engineering proposals on base HVAC system such as the optimized nozzle angle for aiming. the characteristics of cabin flow, and defrosting/deicing patterns on windshield and side glass, etc. can be deduced.
Active Aero Shutter를 통한 차량의 Drag 성능 개선
이동현(Donghyun Lee),하종백(Jongpaek Ha),김영호(Youngho Kim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
After vehicle design fixed, aerodynamic performance development has many restriction. It is due to major factor of Aerodynamic performance is vehicle styling. Among of restriction, cooling performance is one of biggest restriction. For vehicle cooling, large amount of airflow should be go through heat exchanger which called cooling drag. The cooling drag takes biggest part of overall vehicle drag. So, we always try to optimize vehicle front grille opening position, size and texture to reduce cooling drag within cooling requirement at early vehicle development stage. But, after style fixed and even grille opening optimized, there are need to reduce vehicle drag due to better fuel economy. For this many additional part applied to vehicle exterior, but drag performance improvement by additional part is not effective. At this study, applying active aero shutter, minimize cooling drag without any influence cooling performance, effectively improve vehicle drag performance.
여경차의 공력 성능 강화를 위한 차량 전면 부분 개발에 대한 연구
김용년(Yongnyun Kim),하종백(Jongpaek Ha),박정렬(Jeongryul Park) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
Fuel economy is one of important factor to buy/select a vehicle by customer and develop a vehicle by Auto company because cost of fuel is increased continuously. And aerodynamics, one of parts to improve fuel economy also has importance in the vehicle development. Development and purchase point of Mini vehicle, smallest class in the vehicle grade, are focused on fuel economy and most of global auto company makes efforts to improvement of fuel economy thru Aerodynamic performance enhancement. Aero development is quite limited in mini vehicle development because this vehicle has lots of regulation in the dimensional standard and it is not easy to approach to optimize exterior shape because of characteristic of mini vehicle. There are lots of development to use additional parts to recovery dimensional limitation. We studied to enhance performance of Aero using front tire deflector, CRFM baffles, Engine room under cover as Additional parts for for-body development. In this paper, Matiz Creative vehicle developed in GM Daewoo Auto & technology is studied to improve its Aero performance in the stage for midcycle enhancement. We performed CFD simulation and wind tunnel test for this development.
휠 회전과 지면효과를 고려한 CFD 모델에서의 차량공력성능
김영호(Youngho Kim),하종백(Jongpaek Ha) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
Recently automotive manufacturer continue their effort to efficient powertrain development, reduction mass and drag for following fuel economy improvement and emission regulation. Particularly, drag reduction is valuable fuel economy enabler for cost. There are many wind tunnels to measure drag reduction in the world. Each wind tunnel has its own setting. According to each own setting, different drag coefficient could be measured for same production vehicle. In this paper, build analysis model for CFD(Computational Fluid Dynamics) from real wind tunnel which be able to measure drag force of vehicle. And, compare drag coefficient from physical wind tunnel test and drag coefficient from CFD simulation for each ground condition and wheel rotating.
차량 형상에 따른 브레이크 냉각성능과 공기역학적 성능과의 상관관계에 관한 수치해석적 사례연구
최상열(Sangyeol Choi),백봉범(Bongbum Baek),하종백(Jongpaek Ha) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The cooling performance of ventilated brake disk of vehicle depends on convective heat transfer rate governed by air flow entering to brake system. To improve the cooling performance, it is obvious that heat released area of objectives should be larger and cooling air flow should be induced to brake system effectively by design optimization of vehicle front end and underbody configurations. However, increasing the brake disk size which is related with heat release causes not only poor fuel economy by increment of vehicle weight and also development cost increases. In addition, it could be concerned about aerodynamic performances due to the geometric changes. Accordingly, it would be more competitive to precede and optimize the co-relation with each performance. Therefore, the aims of this case study with CFD are to support the effect of additional parts and design changes on the brake cooling performance and to provide the advanced backups for the further development.
Grille opening size 변화에 따른 soaking구간에서의 underhood 온도변화에 대한 해석적 연구
유연준(Yeunjun Yoo),이충혁(Chunghyuk Lee),하종백(Jongpaek Ha),이태원(Taewon Lee) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
Heat source information on design parameters of components located in and underbody are required because these parameters affect final heat damage. Most of automotive makers have their own data of heat impact on the relationship between design parameters and heat source, which was mostly obtained by experimental and trial-and-error methods in the past. Thermal soak study and issues execute in an early stage of the development phase of a new vehicle. Thermal soak results from vehicle with high load after driving and shutting off engine. Underhood and underbody flow are stagnant pattern, and these are simulated by natural convection. At this time, the components close to exhaust system are affected by thermal fluid. For the complex geometry, a 3-D computational program is used to consider heat transfer, which results in steady and transient analysis. Based on these premises a numerical method is developed and validated for a simplified test case as well as for a full vehicle.
Front End Airflow의 유동해석을 위한 차량용 냉각홴의 MRF 모델링
김영호(Youngho Kim),이동현(Donghyun Lee),하종백(Jongpaek Ha),이태원(Taewon Lee) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The radiator cooling fan is essential component to remove coolant heat for powertrain cooling. Also, accurate fan modeling is one of the most important factor to simulate aerodynamic and powertrain cooling performance. MRF(Multiple Reference Frame) method is steady state approach for rotating domain and effective way to describe swirl motion with fan shape. In this paper, compared MRF method to surface boundary condition ; pressure jump, pressure jump with swirl. For aerodynamics, it is noticed that MRF method is effective drag force prediction way in engine room component. but, pressure jump fan boundary condition can be used as alternative for drag coefficient prediction. For powertrain cooling simulation, radiator and fan flow rate can be predicted by scaling law of previous paper about MRF method.
Plenum Water Drainage Hole 과 Cowl Cover Hole의 상관관계에 대한 수치해석적 연구
김성현(Sunghyun Kim),김용년(Yongnyun Kim),하종백(Jongpaek Ha),이태원(Taewon Lee) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The role of the Heating, Ventilation and Air Conditioning (HVAC) System of passenger vehicle is to maintain the ambient environment within the vehicle at a temperature and humidity comfortable for the occupants, regardless of the external weather conditions. A typical HVAC system consists of a heater, air conditioning part, blower to maintain airflow, and an inlet plenum chamber. The role of the plenum chamber is to trap primarily water drops but also large particles in the airflow such as, leaves, pollen and dust, as well as to provide a uniform airflow field into the rest of the HVAC system. An air filter in the airflow assists in these functions. A commonly occurring problem in vehicles incorporating an HVAC system is that of unwanted water ingress into the cabin space. This occurs mainly in wet weather conditions, and is caused by the penetration of water through the cowl box and air filter. Large droplets are broken up by the blower motor into a fine mist that can collect in the interior of the car, causing window fogging, damage to blower motor and passenger discomfort. A numerical study is conducted to estimate cowl inlet hole size and to simulate plenum water drainage performance.