农业工程学报
農業工程學報
농업공정학보
2014年
23期
94-100
,共7页
数值分析%水轮机%叶轮%泥沙磨损%固液两相流
數值分析%水輪機%葉輪%泥沙磨損%固液兩相流
수치분석%수륜궤%협륜%니사마손%고액량상류
numerical analysis%hydraulic turbine%impellers%sediment erosion%solid-liquid two-phase flow
为了掌握泥沙介质在水轮机转轮中的分布规律以及对转轮压力场的影响,该文应用固液两流体多相流动模型,充分考虑了固液两相间的相互作用,通过求解雷诺时均N-S方程和重正化群k?ε湍流方程,对不同泥沙介质条件下水轮机转轮通道中的流动进行数值研究。研究结果表明,含沙水会导致水轮机转轮叶片表面压力载荷增大,固液两相间速度差异是导致叶片表面泥沙体积浓度分布的变化的主要原因。小粒径泥沙在叶片表面分布均匀且体积浓度低,大粒径泥沙会集中分布在叶片的前缘及出水边等区域。该研究可为多泥沙电站水轮机转轮抗泥沙设计提供参考。
為瞭掌握泥沙介質在水輪機轉輪中的分佈規律以及對轉輪壓力場的影響,該文應用固液兩流體多相流動模型,充分攷慮瞭固液兩相間的相互作用,通過求解雷諾時均N-S方程和重正化群k?ε湍流方程,對不同泥沙介質條件下水輪機轉輪通道中的流動進行數值研究。研究結果錶明,含沙水會導緻水輪機轉輪葉片錶麵壓力載荷增大,固液兩相間速度差異是導緻葉片錶麵泥沙體積濃度分佈的變化的主要原因。小粒徑泥沙在葉片錶麵分佈均勻且體積濃度低,大粒徑泥沙會集中分佈在葉片的前緣及齣水邊等區域。該研究可為多泥沙電站水輪機轉輪抗泥沙設計提供參攷。
위료장악니사개질재수륜궤전륜중적분포규률이급대전륜압력장적영향,해문응용고액량류체다상류동모형,충분고필료고액량상간적상호작용,통과구해뢰낙시균N-S방정화중정화군k?ε단류방정,대불동니사개질조건하수륜궤전륜통도중적류동진행수치연구。연구결과표명,함사수회도치수륜궤전륜협편표면압력재하증대,고액량상간속도차이시도치협편표면니사체적농도분포적변화적주요원인。소립경니사재협편표면분포균균차체적농도저,대립경니사회집중분포재협편적전연급출수변등구역。해연구가위다니사전참수륜궤전륜항니사설계제공삼고。
Sediment erosion of hydraulic turbine is the complicated engineering problem related to such factors as operating conditions of hydraulic turbine, solid-liquid two-phase flow characteristics and sediment properties. In this paper, the three dimensional full channel geometric model of prototype turbine is established to understand change in internal pressure of runner and sediment distribution in runner channel under different sediment flow conditions. The hydraulic turbine mainly consists of spiral case, vane, runner and draft tube. Every part generates its corresponding independent meshes, and then is connected with each other by internal interfaces. The total number of grid cell is 7 888 784 in computational domain. Considering solid-liquid interactions fully, based on Eulerian-Eulerian multiphase flow model, Reynolds-averaged Navier-Stokes and RNG k-ε turbulence equations are numerically solved to study internal flows of hydraulic turbine runner under different sediment flow conditions. <br> Research results show that pressure distributions on runner blade surfaces are similar under clear and sandy water flow conditions, i.e., from blade inlet to outlet edges, pressure gradually decreases, and there is a uniform transition without obvious local distortion in pressure field, but the surface pressure is slightly higher in the case of sediment flow. It is further found that surface pressure increases linearly with sediment concentration, and first increases and then decreases with the increase of sediment particle size. Sediment concentration is low on the pressure surface of blade near inlet edge, gradually increases towards the edge and attains its maximum value on the edge. Solid-liquid two-phase flow speed is high and blade thickness is small near outlet edge, so erosion destruction is easy to occur there. Under the conditions of the same sediment particle size, change in sediment concentration has little effect on sediment distribution on blade surface. Also, under the conditions of the same sediment concentration, small sediment particles evenly distribute on runner surface with low concentration, and large ones are clustered in the regions of blade leading and outlet edges to cause local serious erosion of runner blades. <br> Finally, velocity difference between solid and liquid phases is discussed to analyze reasons for change in sediment distribution on blade surface in this paper. The results show that as far as this study is concerned, with the increase in sediment concentration, velocity difference changes a little under the conditions of the same sediment particle size. In this case, the solid-liquid two-phase flow structure is maintained, and pressure distribution is basically the same on blade surface. On the other hand, with the increase of sediment particle size, velocity difference gradually increases under the conditions of the same sediment concentration. The ability of sediment particle to follow water movement becomes bad, which makes sediment particle easily deviate from water streamline under the conditions of large-size sediment flow. Flow separation occurs in the flow direction and the regions where flow velocity changes significantly, and sediment particles hit blade surface to cause serious erosion of blade surface material. This study can provide technical references for the sediment control design of turbine runner operating in sediment-laden rivers.