• Title/Summary/Keyword: Total Pressure Loss

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이중 Orifice를 지나는 압축성 유동에 관한 해석적 연구 (Analytical Study on the Compressure Flow Through a Double Orifice)

  • 김희동;김태호;우선훈
    • 한국추진공학회지
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    • 제1권2호
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    • pp.41-47
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    • 1997
  • 본 연구에서는 이중 orifice를 지나는 압축성 유동을 해석하기 위하여 압축성 유체에 대한 이론계산을 수행하였다. 이중 orifice의 단면적비, orifice 상류의 마하수 및 orifice 사이의 전압손실을 변화시켜, orifice로 인하여 발생하는 축류부에서 유동이 초우크하게 되는 조건을 구하였다. 본 연구의 결과로부터 유동의 초우크 현상은 orifice 단면적비뿐만 아니라 전압손실에도 의존함을 알 수 있다.

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75 kW 용융탄산염 연료전지 (MCFC) 스택 내 압력 손실 해석 (Pressure Loss Analysis of the 75 kW MCFC Stack with Internal Manifold Separator)

  • 김범주;이정현;김도형;강승원;임희천
    • 한국수소및신에너지학회논문집
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    • 제19권5호
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    • pp.367-376
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    • 2008
  • To obtain the data of the pressure loss and differential pressure at the inside of the stack that was composed of 126 cells with 7,500 cm2 electrode area, 75kW molten carbonate fuel cell system has been operated. Computational fluid dynamics was applied to estimate reactions and thermal fluid behavior inside of the stack that was adopted with internal manifold type separator. The pressure loss coefficient K showed 72.29 to 84.01 in anode and 6.34 to 8.75 in cathode at low part of cells at the inside of 75 kW MCFC stack respectively. Meanwhile, the pressure loss coefficient of the higher part of cells at the interior of the stack showed 15.36 and 56.44 in anode and cathode respectively. These results mean that there is no big total pressure difference between anode and cathode at the inner part of 75 kW MCFC stack. This result will be reflected in 250kW MCFC system design.

메탈 할라이드 램프 외관의 최적 봉착조건에 관한 연구 (A Study for Optimal filling Condition in Outer Enclosure of Metal Halide Lamp)

  • 지철근;이성진
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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    • pp.296-299
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    • 1987
  • The purpose of this paper is to increase the lamp efficacy by filling the optimal Nitrogen gas pressure in the outer enclosure of metal halide lamp. This study presents a new model of Langmuir in the outer enclosure of discharge lamp. In this paper, in the first place, the diameter of Langmuir sheath and the total gab loss were calculated. Secondly, the each gas loss was computed if the arbitrary gas pressure is filled, With the calculated data, flash over which affects the lamp efficacy, lamp life and color rendering was considered. In case of the established discharge lamp, the gab pressure has been filled by experience only roughly. The gas loss is converted into the radiation output. Therefore, the lamp efficacy is improved by reducing the gas loss.

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3차원 축류형 터빈에서 입사각의 영향에 관한 실험적 연구 (An Experimental Study of Incidence Angel Effect on 3-D Axial Type Turbine)

  • 김동식;조수용
    • 대한기계학회논문집B
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    • 제26권9호
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    • pp.1292-1301
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    • 2002
  • An experimental study of turbine performance is conducted with various incidence angles on a rotating turbine rotor. 5 different incidence angles are applied from -17$^{\circ}$to 13$^{\circ}$with 7.5$^{\circ}$gaps. In order to precisely set up the incidence angles at the rotor inlet, 5 turbine discs are manufactured with the different fir tree section. Total-to-total efficiencies are obtained on the several off-design points with considering the exit total pressure, which is meas fred at 12 locations between the hub and casing using a pressure rake. The degree of reaction is 0.373 at the mean radius, and Reynolds number based on the rotor chord is 0.86$\times$10$^{5}$ at the turbine inlet on the design point experiment. The experiment on a single-stage turbine is conducted at the low-pressure and low-speed state, but it is sufficient to consider the blade loading effect due to the rotating apparatus even though the total pressure loss at the exit is increased proportionally to the turbine output power. The experimental results recommend 6$^{\circ}$as an optimum incidence angle on the turbine blade design. The total-to-total efficiency is steeply decreased when the incidence angle is over $\pm$9$^{\circ}$ from the optimum incidence angle. In the range of less than -10$^{\circ}$incidence angle, 7.5$^{\circ}$ reduction of incidence angle generates 15% decrease of total-to-total efficiency. This result is obtained on the same rotor blade by changing only the rotational speed to minimize the effect of profile and secondary flow loss in the passage. Experimental results show that the change rate of total-to-total efficiency according to the incidence angle change is unchanged although the turbine operates at the off-design condition.

선형터빈 익렬의 익단간극유동에 대한 수치해석적 연구 (Numerical simulation of tip clearance flows through linear turbine cascades)

  • 이훈구;유정열
    • 대한기계학회논문집B
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    • 제21권6호
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    • pp.813-821
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    • 1997
  • Three-dimensional turbulent incompressible flow through the tip clearance of a linear turbine rotor cascade with high turning angle has been analyzed numerically. As a preliminary study to predict the tip clearance loss realistically, a generalized k-.epsilon. model derived by RNG (renormalized group) method is used for the modeling of Reynolds stresses to account for the strain rate of turbulent flow. The effects of the tip clearance flow on the passage vortex, the total pressure loss are considered qualitatively. The existences of vena contract and tip clearance vortex have been confirmed and it has been shown that as the size of the tip clearance increases, the accumulated flow through the tip clearance and the total pressure loss downstream of the cascade increase.

열교환기가 공기조화용 터보팬의 성능에 미치는 영향에 대한 실험적 연구 (An Experimental Study on the Effect of heat exchanger on turbo fan for air conditioning)

  • 장승용;남임우;주원구;조강래
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.615-618
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    • 2002
  • Turbo-fan for ceiling cassette type air conditioner doesn't operate in general volute. It is operated by porous material, heat exchanger. Heat exchanger increases resistance of air conditioning system and disturbs exit-flow of impeller. Therefore it has some influences on impeller capacity. In this study, we want to how that influence of exchanger on impeller capacity for ceiling cassette type air conditioner. To research, we made circular case that didn't have asymmetric part unlike rectangular case. With and without heat exchanger we measured total pressure and static pressure of impeller and three-dimensional rear flow field From the result, a turbo fan , installed in the 35mm back of fan and operated in heat exchanger, experienced $2{\%}{\~}5{\%}$% total pressure loss over all flow rate. With heat exchanger impeller efficiency decrease as flow rate decrease when flow rate coefficient was below 0.18. Especially when flow rate coefficient was below 0.12, there was $20{\%}{\~}30{\%}$ decrease of impeller efficiency.

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75톤급 액체로켓 엔진 터보펌프 터빈의 성능특성연구 (Investigation on the Performance Characteristics of the 75ton Class Turbopump Turbine)

  • 정은환;이항기;박편구;김진한
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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    • pp.38-44
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    • 2010
  • 75톤급 개방형 액체로켓용 터보펌프 터빈의 성능시험을 수행하였다. 넓은 압력비와 회전수 영역에서 터빈의 출력을 측정하였으며 이를 통해 터빈로터 전후의 유동특성을 파악하였다. 이와 함께 터빈의 효율 변화 및 측정된 로터입구의 압력을 기 개발된 30톤급 터빈과 비교하여 설계 의도에 부합되는 향상된 성능의 동익을 재설계하였다.

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선형터빈 케스케이드 통로내의 2차 유동과 손실에 관한 연구 (The Experimental Investigation of the Secondary Flow and Losses Within the Plane Turbine Cascade Passage)

  • 이기백;양장식;나종문
    • 대한기계학회논문집
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    • 제19권3호
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    • pp.784-795
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    • 1995
  • This paper represents the results of the experiments of the three-dimensional flow and the aerodynamic loss caused by the three-dimensional flow within the plane bucket blades. To research the secondary flow and the aerodynamic loss, the large-scale plane bucket blade of lst-stage in the low pressure steam turbine is made of FRP. The detailed investigation of the secondary flow and the aerodynamic loss using 5-hole pressure probe within turbine cascade has been carried out in the low speed wind tunnel. The limiting streamlines of the suction and endwall surface have been visualized by the oil film method. The flow visualization of the secondary flow has been performed by the laser light sheet technique and image processing system. By using the method mentioned above, it is possible to observe the evolution of the pitchwise mass-averaged flow deviation angle and total pressure loss coefficient, the secondary flow, and the aerodynamic loss through the cascade.

초음속 공기유동으로의 연료 분사노즐 종횡비 변화에 대한 연소특성 연구 (Effects of Aspect Ratio of a Fuel Injection Nozzle into a Supersonic Air Stream on Combustion Characteristics)

  • 김경무;백승욱;김윤곤
    • 한국추진공학회지
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    • 제8권1호
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    • pp.44-53
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    • 2004
  • 본 논문에서는 슬릿형 분사노즐의 출구 종횡비에 따라 3차원 화학반응 유동장을 수치적 계산을 통하여 그 특성을 조사하고 연소/혼합 촉진 방법을 고찰하였다. 내부유입유동과 슬릿측면 와동들 둘 다 혼합관점에서 고려되어야 한다는 것을 보여 주었다. 연소효율은 종횡비1.0을 기준으로 작은 경우가 낮고 압력손실 역시 종횡비가 작은 경우가 적다. 모든 결과들은 유동방향으로 긴 슬릿이 연소와 압력손실에 대해 바람직함을 나타내고 있다.

An Experimental Investigation of Side-Orifice Effects on Pressure Drop for Single-Phase Flow

  • Seo, Kyong-Won;Chun, Moon-Hyun;Nam, Ho-Yun;Park, Seok-Ki;Lee, Yong-Bum
    • 한국원자력학회:학술대회논문집
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    • 한국원자력학회 1996년도 추계학술발표회논문집(1)
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    • pp.295-300
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    • 1996
  • To investigate the effects of the side-orifice on the pressure drop for single-phase flow, a series of experiments have been carried out with 16 different downstream test sections with various combinations of side-orifice shapes, different numbers of side-orifices, and different arrangements of the side-orifice using water as a working fluid. From the measurements of the pressure drop and the flow rate, the pressure loss coefficient of the side-orifice(s) has been evaluated. Based on the total number of 529 present data, an empirical correlation for the pressure loss coefficient has been developed in terms of Reynolds number and geometric parameters, such as area ratio, equivalent diameter, leading edge, and average width of side-orifice.

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