本文選題：導葉式離心泵 + 液力透平��； 參考：《蘭州理工大學》2017年碩士論文

【摘要】：液體余壓能的高效回收利用對節(jié)能降耗,促進可持續(xù)發(fā)展具有重要意義。采用離心泵反轉作液力透平工況運行,以達到液流余能轉化為其他形式能量是行業(yè)內正積極探索,大力推廣的方向。本文在自主設計的導葉式離心泵基礎上,嘗試以其反轉運行工況為研究對象,采用大渦模擬與Mixture多相流模型相結合的數(shù)值計算方法,對液力透平運行在不同流量工況下,分別過流清水介質和含沙水介質的外特性和內流場特性展開研究。首先,采用標準k-ε兩方程模型和Mixture多相流模型對清水介質和固液兩相介質進行定常計算,得到了液力透平0.7~1.4QBEP(QBEP為最優(yōu)效率流量)工況下的外特性曲線。分別對清水介質和含沙水介質在0.7 QBEP、1.0QBEP、1.3QBEP三種不同流量工況流道內壓力、速度、渦量和流線等物理量和固相顆粒分布情況進行了對比分析。定常計算結果表明:在流量較小的情況下,固液兩相介質下的壓頭高于清水時的壓頭,而當流量增大至1.0QBEP左右時,固液兩相介質下的壓頭開始低于清水時的壓頭;固液兩相介質下的效率始終明顯低于清水介質,且最高點并未出現(xiàn)在清水介質下1.0QBEP處,而是向大流量處偏移。沿透平工況的液流方向,壓力和速度均呈階梯式遞減規(guī)律分布,固液兩相介質時流道內整體壓降較清水介質大。小流量時,顆粒的存在對流場紊亂程度的影響較大,大流量時,顆粒存在對流場紊亂程度的影響較小。其次,采用大渦模擬和Mixture多相流模型分別對清水介質和含沙水介質進行了非定常計算,對0.7 QBEP、1.0QBEP、1.3QBEP三種流量工況下流道內壓力脈動情況進行了對比分析,對1.0QBEP工況下動靜葉柵流道內渦量分布的變化情況進行了追蹤。非定常計算結果表明:動靜葉柵交界面處和導葉內監(jiān)測點壓力脈動時域周期性受到葉輪內壓力梯度的交替變化影響明顯,且與葉片通過周期一致。各監(jiān)測點的壓力系數(shù)隨著流量的增大而逐漸增大,脈動幅度隨流量增大而逐漸減小。流道內越靠近干涉區(qū)域,壓力脈動幅度越大,且脈動高頻成分越多。不同工況壓力脈動的主頻均為葉片通過頻率,諧頻為葉頻的倍數(shù),其脈動幅值呈指數(shù)形式衰減。在小流量工況下,葉輪內部渦流誘導了明顯的二次諧波,顆粒的存在增強了動靜葉柵附近的高頻壓力脈動。大流量工況下,顆粒的存在削弱了動靜葉柵附近的高頻壓力脈動。隨著葉輪葉片逐漸接近導葉葉片出口,葉輪葉片背面生成大量渦旋,沿水流方向出現(xiàn)拉伸、合并等多種復雜演化形式后逐漸耗散。固液兩相流體粘性更大,加速了流場中大尺度渦的破裂和小尺度渦的消亡。
[Abstract]:The efficient recovery and utilization of liquid residual pressure energy is of great significance for energy saving and sustainable development. It is an active exploration and popularizing direction in the industry to use the centrifugal pump to reverse the hydraulic turbine working condition so as to convert the residual energy of liquid flow into other forms of energy. On the basis of the self-designed guide vane centrifugal pump, this paper attempts to take its reverse operation condition as the research object, and adopts the numerical calculation method combining the large eddy simulation and the mix multiphase flow model to calculate the hydraulic turbine operating under different flow conditions. The external characteristics and internal flow field characteristics of overflowing water medium and sand bearing water medium are studied respectively. Firstly, the standard k- 蔚 two-equation model and Mixture multiphase flow model are used to calculate the steady state of clear water medium and solid-liquid two-phase medium, and the external characteristic curve of hydraulic turbine 0.7 ~ 1.4QBEP (QBEP is the optimal efficiency flow rate) is obtained. The distribution of solid particles and pressure, velocity, vorticity and streamlines in the flow channel of 0.7 QBEPU 1.0QBEPU 1.3QBEP in clear water medium and sand bearing water medium were compared and analyzed respectively. The steady calculation results show that when the flow rate is small, the pressure head in solid-liquid two-phase medium is higher than that in clear water, but when the flow rate increases to about 1.0 QBEP, the pressure head in solid-liquid two-phase medium is lower than that in clear water. The efficiency of the solid-liquid two-phase medium is always lower than that of the clear water medium, and the highest point does not appear at 1.0QBEP under the clear water medium, but deviates to the high flow rate. Along the flow direction of turbine, the pressure and velocity are all distributed in step decreasing law, and the whole pressure drop in the channel is larger than that in the clear water medium in the solid-liquid two-phase medium. When the flow rate is small, the influence of the disturbance degree of the flow field is greater than that of the large flow rate. Secondly, the unsteady calculation of clear water medium and sand bearing water medium is carried out by using large eddy simulation and mix multiphase flow model, and the pressure pulsation in flow channel under 0.7 QBEPU 1.0 QBEPU 1.3 QBEP flow condition is compared and analyzed. The variation of vorticity distribution in static and static cascade flow channels under 1.0 QBEP condition was tracked. The unsteady calculation results show that the time domain pressure pulsation at the interface between the static and static cascades and the monitoring points in the guide vane is obviously influenced by the alternating variation of the pressure gradient in the impeller and is consistent with the passing period of the blade. The pressure coefficient of each monitoring point increases gradually with the increase of flow rate, and the amplitude of pulsation decreases with the increase of flow rate. The closer the channel is to the interference region, the greater the pressure fluctuation amplitude is and the more the high frequency components of the pulsation are. The main frequency of pressure pulsation in different working conditions is the blade passing frequency, the harmonic frequency is the multiple of the leaf frequency, and its pulsation amplitude is exponentially attenuated. Under the condition of small flow rate, the eddy current in the impeller induces obvious second harmonic waves, and the presence of particles enhances the high frequency pressure fluctuation near the stator and stator cascades. Under large flow conditions, the presence of particles weakens the high frequency pressure pulsation near the dynamic and static cascades. With the impeller blade approaching the outlet of the guide blade, a large number of vortices are formed on the back of the impeller blade, stretching along the direction of the water flow and gradually dissipating after merging various complex evolution forms such as the impeller blade. The viscosity of solid-liquid two-phase fluids is stronger, which accelerates the rupture of large-scale vortices and the extinction of small-scale vortices in the flow field.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH311

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