A Study on Flow Analysis for Pump Sump Model and Design Methods of Anti-Vortex Device

Worldwide, an increasing demand of electricity leads to a many number of constructions of power plant. In power plant producing huge amount of electricity, a large-scale pump with high flow rate is installed. Although a performance of the large-scale pump is determined by the stage of design and manufacture, the Pump intake design is the most significant consideration for pump performance and life. As a crucial part of the pumping station, sump is designed to provide uniform. To attain the uniform flow in the sump needs a civil construction of large scale. By contrast, compact design of pumping station is main concern for global construction companies. However, the compact pump intake design without sump model test can result in undesired flow conditions. For instance, a flow passing through an insufficient length of sump arrives at pump entrance as non-uniform flow, and it causes deleterious effects on pump such as vibration and noise. In addition, a vortex due to inappropriate design of sump can leads to cavitation nearby the intake pipe which not only impacts on the impeller but also generates vibration. The decline of pump performance and high maintenance can be acquired due to these undesired flow behavior. Thus, to predict the flow behavior the model test of sump is conducted. The sump model test is commonly processed during the new or the period of pump replacement. Through the model test an optimized AVD (Anti-Vortex Device) for sump wasinvestigated and designed, and its performance was assessed. Currently, numerous needs of sump model test has been requested due to the rapid increase of pump demands globally, and to fulfill the demands the development of AVD technology is emphasized. In this study, the comparative analysis of flow behavior around intake entrance by PIV method, which visualizing the fluid field, and ANSYS CFD tool was conducted. A swirl angle of swirl meter for the sump model test was investigated at different types and locations. Design parameters of AVD were determined based on various types of sump, and it was verified through the 30 cases of sump model tests with different geometries. In addition, the combination of sump model and AVD is suggested. A swirl angle varies by 10% with the amount of flow rate of sump, and the averaged range of swirl angle by ANSI/HI 9.8 standard guideline is dictated from 0.5 to 5 degree. The maximum error of swirl angle was 8% according to materials, thickness and weight of swirl meter, and the range of 0.4 to 5 degree is the averaged range of swirl angle by ANSI/HI 9.8. In constant flow rate, the swirl angle according to different locations of swirl meter at 4d was 5% lower than at 0.5d, and it has an error by 0.25 degree at the averaged 5 degrees of swirl angle. From numerical analysis of sump by ANSYS CFD the maximum gap of swirl angle was 3.5% compared to experimental result. When eliminating submerged vortices and with bottom AVD the result of swirl angle was decreased as 0 ~10%, and also the angle was decreased as 20% when surface vortices were removed. The reduction of swirl inside the intake pipe was obtained by the installation of AVD. The relation formula according to design parameters of AVD such as diameter and cross-sectional area of sump, distance between intake entrance and the bottom, and distance between the center of intake pipe and the back wall is illustrated. A stabilization of the flow was verified by that submerged and free surface vortices were removed by the combination of AVD manufactured with the design method, Curtain wall and distributors.1. 서 론 1.1 연구배경 1 1.2 연구동향 3 1.3 연구목적 4 2. 흡수정 모델 시험을 통한 AVD 설계 2.1 와류제거장치(AVD) 개요 5 2.2 흡수정 시험 방법 8 2.2.1 상사조건 8 2.2.2 측정 및 운전장치 10 2.2.3 보텍스 구분 및 판정기준 12 2.3 흡수정 시험 16 2.3.1 냉각탑 유형 16 2.3.2 좁은 입구 유형 38 2.3.3 넓은 입구 유형 62 2.4 와류제거장치의 설계 84 2.4.1 와류제거장치의 설계 요인 84 2.4.2 형상에 따른 와류제거장치 설계 요소 85 3. 흡수정 모형실험 3.1 실험장치 88 3.1.1 흡수정 모형설계 88 3.1.2 흡입관 91 3.1.3 순환펌프와 인버터 92 3.1.4 흡수정 모형 실험장치 93 3.2 실험조건 및 계측방법 94 3.2.1 보텍스 브레이커 설치 유무 94 3.2.2 스월메타 종류 95 3.2.3 스월메타 설치 위치 97 3.2.4 흐름분배기 99 3.2.5 와류제거장치 부착 100 3.2.6 실험 케이스 정리 102 3.3 흡수정 실험 결과 및 고찰 103 3.3.1 보텍스 브레이커 설치 유무에 따른 스월각 비교 103 3.3.2 스월메타 타입에 따른 스월각 비교 104 3.3.3 스월메타 설치 위치에 따른 스월각 비교 107 4. 흡수정 PIV 유동계측과 수치해석 4.1 PIV 유동가시화 109 4.1.1 PIV 개요 109 4.1.2 PIV 실험장치의 구성 111 4.1.3 조명 및 추적입자 112 4.1.4 영상입력 및 저장장치 113 4.1.5 동일입자 추적 114 4.2 수치해석 개요 115 4.2.1 지배방정식 115 4.2.2 이산화방법 117 4.2.3 난류모델 124 4.3 PIV 계측 129 4.3.1 흐름분배기 유동특성 129 4.3.2 흡입관 주위의 유동특성 133 4.3.3 와류제거장치 주위의 유동특성 (AVD-1) 136 4.3.4 와류제거장치 주위의 유동특성 (AVD-2) 141 4.3.5 와류제거장치 주위의 유동특성 (AVD-3) 145 4.3.6 와류제거장치 주위의 유동특성 (AVD-4) 148 4.4 수치해석 149 4.4.1 3D 형상과 격자생성 149 4.4.2 경계조건과 계산조건 151 4.4.3 수치해석 결과 152 5. 결론 169 감사의 글 171 참고문헌 17

A Study on the Performance Analysis and Flow Characteristics of the Direct Drive Turbine For Wave Energy Conversion

The purpose of this study is to examine the influence of nozzle shape on the performance and effect of wave conditions on the performance and internal flow of a direct drive turbine (DDT)model for wave energy conversion. The performance of the turbine is calculated by the variation of nozzle shape using a commercial CFD code. Moreover, Three kinds of test turbine models are adopted for the experiments of performance test and internal flow visualization. All the experiments using the test turbine models have been conducted in a 2-D wave channel. Regular waves by various wave conditions of wave height and wave period are applied to the turbine performance test. Influence of turbine configuration by several combinations of turbine nozzle shapes and attachment devices on the turbine performance is also investigated. The results of CFD analysis show that nozzle shape should be designed considering wave height and flow rate entering to the turbine. Best efficiencies of the turbine by 4 types of the nozzle shape do not change largely but overall performances vary mainly by the cross-sectional area of nozzle inlet. The output power of the cross-flow type hydro turbine changes considerably by the nozzle shape, and a partial region of Stage 2 in the runner blade passage obtains maximum regional output power in comparison with the other region of the runner blade passage. Experimental results show that rotational speed, differential pressure, inflow flow rate, maximum output power and best efficiency of the turbine model vary considerably by the wave conditions. Number of rotation time series data of no load condition is shown change of 10%. When wave height rises, the performance increases.(H=20cm , P_(T)=7.2W , η=45.5% -> H=26cm , P_(T)=11.9W , η=51.6%) Installation of front guide nozzle and rear water reservoir to the test turbine improves the turbine performance. Large passage vortex occurs both at the front and rear nozzles in turn by reciprocating flow in the turbine passage.제 1 장 서론 = 1 1.1 연구 배경 = 1 1.2 연구동향 = 2 1.3 연구목적 = 6 1.4 DDT 구동원리 = 8 제 2 장 CFD를 이용한 노즐 형상 결정 = 10 2.1 수치해석 기법 = 10 2.1.1 지배방정식 = 11 2.1.2 이산화 방법 = 11 2.1.3 난류모델링 = 14 2.2 노즐형상과 러너의 형상 = 17 2.3 계산격자 및 경계 조건 = 19 2.3.1 계산격자 = 20 2.3.2 경계조건 = 21 2.4 결과 및 고찰 = 22 2.4.1 성능 곡선 = 22 2.4.2 출력 해석 = 23 2.4.3 속도 벡터와 유선 = 25 2.4.4 속도 분포 = 27 2.4.5 압력 분포 = 30 제 3 장 직접구동터빈(DDT)의 성능 실험 = 33 3.1 실험장치 = 33 3.1.1 2D 조파 장치 = 33 3.1.2 직접구동터빈 모델 = 36 3.1.3 계측 센서 보정 = 40 3.2 실험방법 = 45 3.3 실험결과 및 고찰 = 46 3.3.1 시계열 데이터 = 46 3.3.2 파고변화 = 48 3.3.3 주기변화 = 50 3.3.4 수심변화 = 51 3.3.5 부착장치에 따른 성능 효과 = 56 3.3.6 노즐 방향에 따른 성능 효과 = 58 3.3.7 노즐 입구에서의 속도 변화 = 60 3.3.8 직접구동터빈의 유동가시화 = 61 제 4 장 결론 = 64 참고문헌 = 65 부록 = 67 감사의 글 = 8

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