Efficiency analysis of the diffuser/nozzle fluid pump on the steady laminar flow region using 3D simulations and experiments

박성훈(Sung Hoon Park),고상근(Kauh. S. Ken) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

Recently, as the semiconductor production technology develops, there has been growing interest in the cooling system using micro fluid pump. Among the various types of micro fluid pump, the valve-less diffuser/nozzle has been extensively studied in recent years. However, the flat-walled diffuser/nozzle flow has not been clearly looked into due to its non-linear characteristics. In this paper, the flow characteristics of the flat-walled diffuser/nozzle have been analyzed in the various channel geometries and pressure boundary conditions at the laminar flow region. From these results, the geometries and boundary conditions for the efficient pump operations are investigated, and modified variables are adjusted as the parameters of the pump efficiency. The experiments are conducted based on the similitude method, and the results are compared to the simulations. It shows that the desirable condition does exist for the efficient diffuser/nozzle pump operation.

상사 모델과 전산 수치 해석을 이용한 diffuser/nozzle pump의 정상 상태에 대한 연구

박성훈(Sung Hoon Park),고상근(Kauh S. Ken) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

Recently, as the semiconductor production technology develops, there has been growing interest in the cooling system using micro fluid pump. Among the various types of micro fluid pump, the valve-less diffuser/nozzle has been extensively studied in recent years. However, the flat-walled diffuser/nozzle flow has not been clearly looked into due to its non-linear characteristics. In this paper, the flow characteristics of the flat-walled diffuser/nozzle have been analyzed using similitude model and simulations. Similitude models are designed so that the flow pattern is same as that of 1/10 scale flow by using high viscous fluid as working fluid. The results are compared to the simulations. It is shown that the flow characteristics of 2D simulation are different from 3D simulations at high Re region, and the measured pump efficiency is highly dependent on the pressure difference as well as the channel geometry. From these results, the desirable conditions for the efficient pump is discussed.

무선계측기법을 이용한 회전 송출공의 압력계수 측정

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.

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.

주기적인 통과후류가 막냉각되는 평판의 유동장에 미치는 영향(1);압력면과 흡입면에 대한 영향(1)

국건,이준식,고상근,Kuk, Keon,Lee, Joon-Sik,Kauh, Sang-Ken 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.6

The effect of periodic passing wake on the film-coolant flow issuing normally from a flat plate was investigated experimentally. The passing wake was generated by rotating thin circular bars. Depending on the rotational direction the test plate could be simulated as a pressure surface or a suction surface of a gas turbine blade. The phase-averaged velocity components were measured using an X-type hot-wire probe. The Reynolds number based on the free-stream velocity and injection hole diameter was 23, 500 and the velocity ratio which is the ratio of film coolant velocity to free-stream velocity was 0.5. The velocity-triangle induced by the wake was similar to that induced by the one generated at the blade trailing edge. The vertical velocity component induced by the passing wake, which approaches to the suction surface and moves away from the pressure surface, played a dominant role in the variation of the flow field. The variation in the phase-averaged velocity on the pressure surface was greater than on the suction surface, but the turbulence kinetic energy variation on the suction surface appeared larger than on the pressure surface.

열적 제한요소를 고려한 열회수 증기발생기의 시동 특성 해석

김영일,김동섭,김재환,노승락,고상근,Kim, Young Il,Kim, Tong Seop,Kim, Jae Hwan,Ro, Sung Tack,Kauh, Sang Ken 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.11

A thorough understanding of the transient behavior during start-up is essential in the design and operation of the heat recovery steam generator(HRSG). During this period of time, material that is exposed to high temperature and experiences a large temperature variation is subject to high thermal stress. In this work, a transient formulation of the HRSG is constructed including the estimation of the thermal stress and fatigue of the drum wall. Start-up behavior of a single-pressure HRSG is analyzed and the effect of bypassing part of the gas turbine exhaust flow on the thermal stress evolution is examined. It is found that the modulation of the gas flow rate using a bypass damper is very useful in view of reducing the thermal stress of the drum and ensuring the fatigue lifetime.

액화천연가스의 냉열을 이용한 가스터빈의 성능향상

김동섭,노승탁,이우일,최만수,고상근,Kim, Tong Seop,Ro, Sung Tack,Lee, Woo Il,Choi, Mansoo,Kauh, Sang Ken 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.5

This work describes analysis on the effect of inlet air cooling by the cold energy of liquefied natural gas(LNG) on the performance of gas turbines. Gas turbine off-design analysis program to simulate the influence of compressor inlet temperature variation is prepared and an inlet air cooler is modeled. It is shown that the degree of power augmentation is much affected by the humidity of inlet air. If the humidity is low enough, that is the water content of the air does not condense, the temperature drop amounts to $18^{\circ}C$, which corresponds to more than 12% power increase, in case of a $1350^{\circ}C$ class gas turbine with methane as the fuel. Even with 60% humidity, about 8% power increase is possible. It is found that even though the fuel contains as much as 20% ethane in addition to methane, the power improvement does not change considerably. It is observed that if the humidity is not too high, the current system is feasible oven with conceivable air pressure loss at the inlet air cooler.

[가솔린엔진부문] 가솔린 엔진의 비정상상태에 대한 Map 구성과 공기 및 연료 모델 개선

심연섭(Yonsob Shim),강태성(Taeseong Kang),강승표(Seungpyo Kang),고상근(Sang Ken Kauh) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

For gasoline engines, a three-way catalyst converter is being used for cleaning up the exhaust gas contamination. Precise air/fuel ratio control is necessary to maximize the catalytic conversion efficiency. In transient condition, feedforward air/fuel ratio control that estimates air mass inducted into the cylinder is performed.<br/> In this study, a fuel injection map that makes accurate air/fuel ratio control possible was constructed for the very same transient condition. In the same condition above, intake air model and fuel model were refined so that fuel injection values based on air mass flow through throttle valve and intake manifold pressure are equal to fuel injection values of the map.<br/>