• 대한기계학회논문집B
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• 제40권11호
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• pp.727-736
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• 2016

본 연구에서는 복합화력 화력 발전소용 고압 다단펌프의 레이디얼 디퓨저 형상에 따른 펌프의 성능(양정, 효율)변화를 수치 해석적으로 분석하였다. 레이디얼 디퓨저 설계 변수는 크게 디퓨저 베인수, 디퓨저 외경비($D_4/D_3$), 리턴채널 출구각도(${\alpha}_6$), 압력회복계수($C_p$) 등으로 선정하였다. 수치해석 결과 디퓨저 외경비가 큰 경우 양정 및 효율이 가장 크게 예측되었으며, 리턴채널의 출구각도(${\alpha}_6$)가 60도인 경우 디퓨저 출구에서의 Pre-Swirl로 인해 출구각도가 90도인 것에 비해 양정이 저하되는 것을 알 수 있다.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.57-65
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• 2000

The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures aye measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.

• 대한기계학회논문집B
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• 제25권4호
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• pp.507-513
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• 2001

Time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates are investigated. Pressure distributions from the impeller exit to the channel diffuser exit are measured for various flow rates from choke to near surge condition, and the effects of operating condition are discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.548-554
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• 2000

The aim of this paper is to understand the time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed far various flow rates from choke to near surge condition, and the effect of operating condition is discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• 한국유체기계학회 논문집
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• 제14권6호
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• pp.54-60
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• 2011

This paper presents the steady-state performance analysis of the first stage of a multistage centrifugal pump, composed of a shrouded-impeller, a vaned-diffuser and a return-channel, using the commercially available computational fluid dynamics (CFD) code, ANSYS CFX. The detailed flow fields in the vaned-diffuser with outlet in its side wall and the return-channel are investigated by the CFD code adopted in the present study. The effect of the vaned-diffuser with a downstream crossover bend and the corresponding return-channel on the overall hydrodynamic performance of the first stage pump has also been demonstrated over the normal operating conditions. The predicted hydrodynamics for the diffusing components herein could provide useful information to match the inlet blade angle of the next stage impeller for improving the multistage pump performances.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.69-77
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• 1999

The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures are measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 강연회 및 연구개발 발표회 논문집
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• pp.164-178
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• 1998

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.231-234
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• 2010

고온의 연소가스에 노출되는 디퓨저 냉각에 필요한 열량을 계산하였다. 디퓨저 내부는 공기와 혼합된 연소가스가 흐르고 디퓨저 벽체는 채널로 구성된 공간에 물이 흐르도록 되어 있다. 디퓨저 구조물과 유체 간에 또는 유체 자체적인 열전달과 구조물 내부의 열전달 현상은 복합적인 형태로 나타나는데 고온에서 작동하는 점을 고려하여 복사, 대류, 전도 모두를 적용 하였다. 열전달량 계산은 경험식에 근거한 1차원 해석과 CFD 해석의 2가지 방법으로 수행하였다. 1차원 해석은 경험식을 통해 얻어진 결과를 적용하여 열전달량을 산출하였고, CFD 해석은 DO 복사 열전달 모델을 적용하여 계산하였으며, 계산의 타당성을 검정하기 위하여 두 방법을 비교하였다. 총 열전달량의 차이는 1% 미만으로 거의 같았으나, 1차원 계산은 열전달 모델의 단순화로 디퓨저 입구에서의 순환영역을 구현하지 못하여 전체적인 열전달량 분포에서는 차이를 보였다. 디퓨저의 안정성을 확보하기 위한 냉각수 용량은 2가지 계산 결과를 조합하여 각 구간별로 최대 열전달량을 근거로 도출하였다.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2707-2720
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• 1996

The aerodynamic design of the two-stages of centrifugal compressors in an 1.2MW industrial gas turbine is completed with the application of numerical analyses. The final shape of an intake, the axial guide vanes and a return channel is determined using several interactions between design and two-dimensional turbulent flow analysis, focused on the minimum loss of internal flows. The one-dimensional turbulent flow analysis, focused on the minimum loss of internal flows. The one-dimensional design and prediction of aerodynamic performances for the compressors are performed by two different methods; one is a method with conventional loss models, and the other a method with the two-zone model. The combination methods of the Betzier curves generate three-dimensional geometric shapes of impeller blades which are to be checked with a careful change of aerodynamic blade loadings. The impeller design is finally completed by the applications of three-dimensional compressible turbulent flow solvers, and the effect of minor change of design of the second-stage channel diffuser is also studied. All the aerodynamic design results are soon to the verified by component performance tests of prototype centrifugal compressors.

• 한국추진공학회지
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• 제3권2호
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• pp.1-9
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• 1999

층류 유동을 기준으로 형성된 압력구배기법의 적용성을 난류유동에 대하여 검증하였다. 압력구배기법은 압력 자체보다는 연속방정식을 이용하여 구한 압력의 구배를 활용하므로서 유동장의 해석에 질량보존의 물리적 법칙을 용이하게 반영할 수 있는 특징이 있다. 압력구배기법은 모든 유동변수를 한 점에 위치시키고 압력구배는 그 사이에 위치시키는 준 엇갈림 좌표계를 기준으로 형성되었다. 이러한 격자계는 프로그램하기가 용이하며 유동의 물리적 특성을 올바로 반영할 수 있는 장점이 있다. 난류유동에 대한 검증은 저 레이놀즈수 $\kappa$-$\varepsilon$ 모델을 이용하여 완전히 발달한 채널유동, 후향계단유동, 원추형 디퓨저유동 등에 대하여 수행하였다. 이러한 해석결과로부터 압력구배기법은 난류유동의 해석에 적용이 가능한 것으로 판단된다. 그러나 압력구배기법은 계산시간이 다소 길게 요구되며 압력구배식의 적정 $\gamma$를 구하는 방법이 용이하지 않아 이에 대한 개선이 요구되고 있다.