http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
길이 대 직경 비와 입구 모서리 반경에 따른 회전 오리피스의 송출 특성
하경표,강세원,고상근,Ha, Kyoung-Pyo,Kang, Se-Won,Kauh, Sang-Ken 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.7
The effect of rotation on the discharge coefficient of orifices with various length-to-diameter ratios and two different inlet corner radii was studied. Length-to-diameter ratios of the orifices range from 0.2 to 10, while the inlet shapes are square edged, or round edges of radius-to-diameter ratio of 0.5. From the experiment, we found that rotational discharge coefficient and Rotation number, when based on ideal exit velocity of the orifice considering momentum transfer from the rotor, describe the effect of rotation very well. In this study, the discharge coefficients of rotating orifices are shown to behave similar to those of the well-known non-rotating orifices. For both rotating and non-rotating orifices, the discharge coefficients increase with the length-to-diameter ratio until a maximum is reached. The flow reattachments in the relatively short orifices are responsible for the increase. The coefficient then decreases with the length-to-diameter ratio due to the friction loss along the orifice bore. The length-to-diameter ratio that yields maximum discharge coefficient, however, increases with the Rotation number because the increased flow-approaching angle requires larger length-to-diameter ratio for complete reattachment. The length-to-diameter ratio for complete reattachment is shorter for round edged orifices than that of square edged orifices by about a unit length-to-diameter ratio.
하경표,구남희,고상근,Ha, Kyoung-Pyo,Ku, Nam-Hee,Kauh, S.Ken 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.7
Pressure coefficient in rotating discharge hole was measured to gain insight into the influence of rotation to the discharge characteristics of rotating discharge hole. Pressure measurements were done by the telemetry system that had been developed by the authors. The telemetry system measures static pressure using piezoresistive pressure sensors. Pressure coefficients in rotating discharge hole were measured in longitudinal direction and circumferential direction with various rotating speed and 3 pressure ratios. From the results, the pressure coefficient, and therefore the discharge coefficient, is known to decrease with the increase of Ro number owing to the increase of flow approaching angle to the discharge hole inlet. However, there exists critical Ro number where the decrease rate of discharge coefficient with the increase of Ro number changes abruptly; flow separation occurs from the discharge hole exit at this critical Ro number. Critical Ro number increases with the increase of length-to-diameter ratio, but the increase is small where the length-to-diameter ratio is higher than 3. The decrease rate of discharge coefficient with the increase of Ro number depends on the pressure recovery at the discharge hole, and the rate is different from each length-to-diameter ratio; it has tendency that the short discharge hole shows higher decrease rate of discharge coefficient.
하경표(Kyoung-Pyo Ha),이석재(Seog Jae Lee),김우태(Woo Tae Kim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Friction reduction is one of the most important factors to improve fuel economy of an engine. Present investigation of an engine’s friction is based on the strip-down method, and present study improved the method to break-down engine’s friction into more components. This was done by cam torquemeter developed by the authors and the torquemeter can separate chain friction from cam shaft friction. Several factors influencing chain guide friction were tested and three major factors were chosen to reduce chain friction by 48%; these factors include chain tensioner spring, oil pressure and chain layout. Fuel economy was measured to increase by 0.8% with the chain friction factors at 2,000 rpm and BMEP 2.0 bar condition. Friction factors of cam shaft, crank shaft and oil pump were also discussed.
하경표(Kyoung-Pyo Ha),오대윤(Dae Yoon Oh),김우태(Woo Tae Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Aeration rate in engine oil is one of the most important data in the development of engine lubrication system. Several methods were reported to measure oil aeration, but none of them ca measure it in real time.<br/> Thus, a new oil aeration meter that can measure oil aeration in real time was developed in this study. The system measures density variation of engine oil with the increase of oil aeration. The density measurements were done in running fluid in order to measure oil aeration in real time. The measurement uncertainty of the present oil aeration meter is about 1%. The oil aeration meter is connected to the place of engine where oil filters attached to, thus present measurement system is very convenient to install and does not need modification of engine. The system is successfully applied to the tests with good accuracy and repeatability.
하경표(Kyoung-Pyo Ha),김우태(Woo Tae Kim),이춘우(Choon Woo Lee),김형익(Hyung Ick Kim),최명식(Myung Sik Choi),한동희(Dong Hee Han),서인기(In Gee Suh),김백식(Back Sik Kim),김대성(Dae Sung Kim) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this study. a novel system of Continuously Variavle Valve Lift (CVVL) engine was developed. The system consists of seven elements while reference engine has four elements: those additional elements are listed as oscillating cam, controller, and connecting link. The system transmits driving torque from rotating cam to cylinder valve via the connecting link and the oscillating cam, and the system changes peak valve lift by adjusting the controller. The CVVL system is characterized by timing advance and duration reduction when the peak valve lift decreases. The CVVL system has good friction behaviors compared with reference engine considering operating conditions of real engine in vehicle. The CVVL system has higher maximum power and lower fuel consumption rate than reference engine. And the system has good durability and dynamic performances. However, the system is in need of brake torque improvement in low and middle engine revolution speed by modifying valve profile.
하경표(Kyoung-Pyo Ha),공진국(Jin Kook Gong),김우태(Woo Tae Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The mechanical energy of engine is lost by engine friction and in driving the engine's auxiliary components, and then transmitted to transmission. Thus, it is very important to know the exact value of engine friction and the driving torque of engine's auxiliary components in order to reduce fuel consumption of engine by reducing these losses. And, it is also helpful to know the braking torque of engine in vehicle so as to improve vehicle's driving performance. For these reasons, present study developed engine torquemeter for in-vehicle application, and measured braking torque of engine in vehicle and analyzed fuel consumption contributions of engine's auxiliary components.
조명래,하경표,김중수,오대윤,한동철,Cho, Myung-Rae,Ha, Kyoung-Pyo,Kim, Joong-Soo,Oh, Dae-Yoon,Han, Dong-Chul 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.1
The aim of this paper is to investigate the friction characteristics of piston assembly, which composed of ring pack and piston skirt. The friction force of piston assembly was measured by using the movable liner in the single cylinder engine, and the various parameters were tested. The friction force was suddenly increased at the expansion stroke due to higher cylinder pressure. The viscous friction was dominant at the mid stroke, but the boundary friction was dominant at the top and bottom dead centers. Through the experiment, we could validate previous theoretical study, and confirm that th e radial clearance and ring tension were very effective to reduce friction loss of piston assembly.
구남희,고상근,하경표,Ku, Nam-Hee,Kauh, Sang-Ken,Ha, Kyoung-Pyo 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.9
Pressure coefficient in a rotating discharge hole was measured to gain insight into the influence of rotation on the discharge characteristics of rotating discharge holes. Pressures inside the hole were measured by a telemetry system that had been developed by the authors. The telemetry system is characterized by the diversity of applicable sensor type. In the present study, the telemetry system was modified to measure static pressure using piezoresistive pressure sensors. The pressure sensor is affected by centrifugal force and change of orientation relative to the gravity. The orientation of sensor installation for minimum rotating effect and zero gravity effect was found out from the test. Pressure coefficients in a rotating discharge hole were measured in longitudinal direction as well as circumferential direction at various rotating speeds and three different pressure ratios. From the results, the behaviors of pressure coefficient that cannot be observed by a non-rotating setup were presented. It was also shown that the discharge characteristics of rotating discharge hole is much more influenced by the Rotation number irrespective of pressure ratio.