史廣泰 楊軍虎 劉小兵 劉洋
摘要: 為了提高液力透平工作時(shí)的穩(wěn)定性,降低機(jī)組的振動(dòng),在液力透平葉輪進(jìn)口前添加不同數(shù)量的導(dǎo)葉,采用SST kω湍流模型,利用FLUENT軟件通過在各過流部件內(nèi)設(shè)置監(jiān)測(cè)點(diǎn)計(jì)算在不同導(dǎo)葉數(shù)下液力透平內(nèi)的壓力和壓力脈動(dòng)情況,然后通過快速傅里葉變換將壓力脈動(dòng)的計(jì)算結(jié)果進(jìn)行處理,分析液力透平各過流部件內(nèi)壓力脈動(dòng)的時(shí)域和頻域分布,最后總結(jié)導(dǎo)葉數(shù)對(duì)液力透平機(jī)組工作時(shí)穩(wěn)定性的影響規(guī)律。研究表明:當(dāng)導(dǎo)葉數(shù)等于9時(shí)蝸殼內(nèi)的壓力脈動(dòng)主頻幅值最??;隨著導(dǎo)葉數(shù)的增加,葉輪內(nèi)的最大壓力脈動(dòng)幅值逐漸減小,而導(dǎo)葉數(shù)對(duì)尾水管內(nèi)壓力脈動(dòng)幅值的影響較小;要提高液力透平機(jī)組的穩(wěn)定性需降低液力透平內(nèi)的壓力脈動(dòng)幅值,而通過葉輪進(jìn)口前添加導(dǎo)葉的方法可以很好地降低液力透平內(nèi)的壓力脈動(dòng)幅值,但導(dǎo)葉數(shù)不能太少也不能過多。關(guān)鍵詞: 導(dǎo)葉; 液力透平; 穩(wěn)定性; 壓力脈動(dòng); 振動(dòng)
中圖分類號(hào): TH311; TK730文獻(xiàn)標(biāo)志碼:A文章編號(hào):10044523(2016)04060907
DOI:10.16385/j.cnki.issn.10044523.2016.04.007
引言
液力透平作為一種能量回收裝置,其葉輪在高壓液體的作用下旋轉(zhuǎn),將液體所具有的能量部分轉(zhuǎn)化為液力透平的機(jī)械能,從而達(dá)到能量回收的目的[12]。但液力透平在工作過程中由于葉輪與蝸殼之間的動(dòng)靜耦合導(dǎo)致液力透平內(nèi)出現(xiàn)壓力脈動(dòng),這種壓力脈動(dòng)會(huì)引起周期性的壓力波,這將導(dǎo)致液力透平各元件中出現(xiàn)周期性的振動(dòng)和噪聲,降低液力透平機(jī)組工作時(shí)的穩(wěn)定性[34]。
目前對(duì)液力透平的研究主要集中在液力透平的選型和高效設(shè)計(jì)方法兩方面,對(duì)于液力透平的選型,主要通過換算關(guān)系將泵工況換算為液力透平工況[56];而對(duì)于液力透平的高效設(shè)計(jì)主要通過優(yōu)化葉輪各幾何參數(shù)、優(yōu)化葉片形狀、添加長(zhǎng)短葉片以及改進(jìn)葉片設(shè)計(jì)方法等[78],還有對(duì)蝸殼截面形狀和幾何參數(shù)等的優(yōu)化研究[9]。除了上述關(guān)于幾何參數(shù)和形狀的研究方法之外,文獻(xiàn)[10]還通過理論的方法對(duì)液力透平的性能進(jìn)行了研究,提出了在考慮葉輪內(nèi)滑移時(shí)液力透平的基本能量方程。當(dāng)離心泵反轉(zhuǎn)用作液力透平時(shí)雖然能夠較好地回收能量,但機(jī)組運(yùn)行并不穩(wěn)定,為了解決液力透平運(yùn)行時(shí)不穩(wěn)定的問題,文獻(xiàn)[11]在液力透平葉輪進(jìn)口前添加導(dǎo)葉,研究發(fā)現(xiàn)添加導(dǎo)葉后各流道間壓力分布更為對(duì)稱??梢?,添加導(dǎo)葉的確可以改善液力透平運(yùn)行時(shí)的穩(wěn)定性。
由于壓力脈動(dòng)也是引起液力透平機(jī)組工作時(shí)不穩(wěn)定的因素之一,所以為了提高液力透平機(jī)組工作時(shí)的穩(wěn)定性,本文通過在液力透平葉輪進(jìn)口前添加不同數(shù)量的導(dǎo)葉來研究導(dǎo)葉數(shù)對(duì)液力透平內(nèi)壓力脈動(dòng)的影響,總結(jié)導(dǎo)葉數(shù)對(duì)液力透平機(jī)組穩(wěn)定性的影響規(guī)律,從而為提高液力透平機(jī)組的穩(wěn)定性提供理論參考。
Abstract: In order to enhance the stability of hydraulic turbine, and reduce the vibration of hydraulic turbine when it is working, this paper added a set of guide vanes at the impeller import of hydraulic turbine, set the monitoring points through ANSYSCFD software in the each flow passage components, and calculated the changes rule of pressure and pressure fluctuation within hydraulic turbine under the different guide vane numbers by using the turbulence model SST k-ω, transformed the calculation results of pressure fluctuation by FFT, analyzed the distribution of time domain and frequency domain within each flow passage components, finally, analyzed and summarized the results. The study found that the dominant frequency amplitude of pressure fluctuation is minimum in the volute when the guide vane numbers is equal to nine. With the increase of guide vane numbers, the greatest amplitude of pressure fluctuation is gradually decreased in the impeller, but the effect of the guide vane numbers on amplitude of pressure fluctuation is smaller in the draft tube. The method that a set of guide vanes are added to the impeller import of hydraulic turbine can good reduce amplitude of pressure fluctuation, enhance the stability of hydraulic turbine, but the guide vane numbers neither too much nor too little.
Key words: guide vane; hydraulic turbine; stability; pressure fluctuation; vibration