發(fā)布時(shí)間：2018-08-19 18:46

【摘要】：近年來,隨著混流式水輪機(jī)裝機(jī)尺寸與單機(jī)容量逐漸增大,水輪機(jī)的振動(dòng)問題日益突出。其中活動(dòng)導(dǎo)葉與轉(zhuǎn)輪相互作用引起的壓力脈動(dòng)是造成水輪機(jī)運(yùn)行不穩(wěn)定的主要原因之一,它會(huì)誘發(fā)機(jī)械振動(dòng),使轉(zhuǎn)輪葉片產(chǎn)生裂紋,影響機(jī)組的穩(wěn)定運(yùn)行。本文以Francis-99混流式模型水輪機(jī)為研究對(duì)象,對(duì)其進(jìn)行全流道數(shù)值計(jì)算,并進(jìn)行活動(dòng)導(dǎo)葉與轉(zhuǎn)輪間無葉區(qū)壓力脈動(dòng)及其傳播特性探究,為水輪機(jī)的安全穩(wěn)定運(yùn)行提供一定的參考。研究工作主要包括了下列幾部分內(nèi)容:首先,對(duì)不同導(dǎo)葉開度的水輪機(jī)進(jìn)行了數(shù)值模擬,獲得水輪機(jī)運(yùn)行特性參數(shù),并與模型試驗(yàn)數(shù)據(jù)進(jìn)行對(duì)比分析。結(jié)果表明:水輪機(jī)的效率、水頭、力矩及各監(jiān)測(cè)點(diǎn)壓力均值的數(shù)值計(jì)算值與試驗(yàn)值吻合較好;壓力脈動(dòng)的數(shù)值計(jì)算結(jié)果也和模型試驗(yàn)結(jié)果基本上一致。其次,對(duì)3種導(dǎo)葉開度的水輪機(jī)進(jìn)行了全流道非定常數(shù)值模擬,分析了不同工況下水輪機(jī)內(nèi)部流動(dòng)特點(diǎn),深入研究了活動(dòng)導(dǎo)葉與轉(zhuǎn)輪間無葉區(qū)壓力脈動(dòng)特性。結(jié)果表明:最優(yōu)工況下,活動(dòng)導(dǎo)葉和轉(zhuǎn)輪間無葉區(qū)由動(dòng)靜干涉效應(yīng)引起的壓力脈動(dòng)主要以轉(zhuǎn)輪葉片通過頻率及其倍頻為主,且壓力脈動(dòng)幅值遠(yuǎn)大于其他位置。無葉區(qū)壓力脈動(dòng)沿水輪機(jī)流道傳播至整個(gè)流場(chǎng),向上游和下游傳播過程中,其幅值都不斷減小。通過對(duì)不同工況下無葉區(qū)壓力脈動(dòng)進(jìn)行詳細(xì)分析,發(fā)現(xiàn)無葉區(qū)壓力脈動(dòng)的主要頻率不受活動(dòng)導(dǎo)葉開度的影響,但是偏離最優(yōu)工況點(diǎn)越遠(yuǎn),壓力脈動(dòng)頻率成分越為復(fù)雜。最后,對(duì)同一導(dǎo)葉開度(小開度)不同流量下的水輪機(jī)進(jìn)行數(shù)值模擬,分析轉(zhuǎn)輪域的內(nèi)部流場(chǎng)分布與壓力脈動(dòng)特性。結(jié)果表明:兩種工況下,轉(zhuǎn)輪域都有明顯的葉道渦產(chǎn)生,水流流態(tài)較差,尤以靠近上冠處最差,偏離上冠越遠(yuǎn),水流流態(tài)越好;隨著流景的增大,轉(zhuǎn)輪域的水流流態(tài)整體上得到了改善,葉道渦的范圍減小,撞擊現(xiàn)象減弱。葉片上各監(jiān)測(cè)點(diǎn)的壓力脈動(dòng)主頻均為28fn,為活動(dòng)導(dǎo)葉通過頻率;且葉片壓力面面的門報(bào)力脈動(dòng)幅值高于吸力面,轉(zhuǎn)輪域中壓力脈動(dòng)幅值的最大值出現(xiàn)在葉片進(jìn)口位],沿著水流流動(dòng)方向,由進(jìn)口至出口壓力脈動(dòng)幅值不斷的降低;葉片壓力面進(jìn)口處壓力脈動(dòng)幅值從上冠到下環(huán)逐漸減小,但在葉片中間和出口處卻不斷增大。葉片吸力面壓力分布規(guī)律和壓力面基本上一致。
[Abstract]:In recent years, with the increasing of the size and capacity of Francis turbine, the vibration problem of turbine becomes more and more serious. The pressure pulsation caused by the interaction between the moving guide vane and the runner is one of the main reasons for the unstable operation of the turbine. It will induce mechanical vibration and make the runner blade crack and affect the stable operation of the turbine. In this paper, the full-channel numerical calculation of Francis-99 Francis turbine is carried out, and the pressure pulsation and its propagation characteristics in the vaneless zone between the active guide vane and the runner are investigated, which provides a certain reference for the safe and stable operation of the turbine. The research work mainly includes the following parts: firstly, the hydraulic turbine with different guide vane opening is numerically simulated, and the operating characteristic parameters of the turbine are obtained, and compared with the model test data. The results show that the calculated values of the efficiency, head, torque and the mean pressure of each monitoring point are in good agreement with the experimental values, and the numerical results of pressure fluctuation are basically in agreement with the model test results. Secondly, the unsteady numerical simulation of three kinds of hydraulic turbines with guide vane opening is carried out, and the characteristics of flow inside the turbine under different operating conditions are analyzed, and the pressure pulsation characteristics in the vaneless zone between the guide vane and the runner are studied in depth. The results show that the pressure pulsation caused by the static and static interference in the leafless region between the active guide blade and the runner under the optimal working condition is mainly caused by the passing frequency and the frequency doubling of the runner blade, and the amplitude of the pressure fluctuation is much larger than that of other locations. The pressure pulsation propagates along the turbine runner to the whole flow field, and the amplitude decreases continuously during the upstream and downstream propagation. Through the detailed analysis of the pressure pulsation in the leafless region under different operating conditions, it is found that the main frequency of the pressure pulsation in the leafless region is not affected by the opening of the active guide vane, but the farther away from the optimal operating condition, the more complex the pressure fluctuation frequency component is. Finally, the numerical simulation of the turbine with the same guide blade opening (small opening) and different flow rate is carried out to analyze the internal flow field distribution and pressure pulsation characteristics of the runner. The results show that under both conditions, there are obvious blade vortex in the runner domain, and the water flow pattern is worse, especially near the upper crown. The farther away from the upper crown, the better the water flow pattern, and with the increase of the flow scene, As a whole, the flow pattern in the runner domain is improved, the range of blade vortex decreases, and the impingement phenomenon is weakened. The main frequency of pressure pulsation in each monitoring point of blade is 28fn, which is the passing frequency of active guide vane, and the amplitude of gate force pulsation of blade pressure surface is higher than that of suction surface. The maximum amplitude of pressure pulsation appears in the inlet position of the blade] in the runner domain. Along the flow direction, the amplitude of pressure pulsation decreases continuously from inlet to outlet, and the amplitude of pressure pulsation decreases gradually from the top crown to the lower ring at the inlet of the blade pressure surface. But in the middle of the blade and at the outlet is increasing. The pressure distribution of the suction surface of the blade is basically the same as that of the pressure surface.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TV734

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