吳賢芳，陸友東，談明高，劉厚林

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葉片安放角對(duì)軸流泵馬鞍區(qū)運(yùn)行特性的影響

吳賢芳1，陸友東2，談明高2，劉厚林2

（1.江蘇大學(xué)能源與動(dòng)力工程學(xué)院，鎮(zhèn)江 212013；2. 江蘇大學(xué)流體機(jī)械工程技術(shù)研究中心，鎮(zhèn)江 212013）

為分析葉片安放角對(duì)軸流泵馬鞍區(qū)工況運(yùn)行特性的影響，以比轉(zhuǎn)速822的軸流泵為研究模型，試驗(yàn)測(cè)試了不同葉片安放角下的運(yùn)行特性。研究表明：隨著葉片安放角的增大，模型泵最優(yōu)工況處的揚(yáng)程、流量和效率均逐漸增大，-4°到+4°的增幅分別為10.4%，26.7%和0.87%；不同安放角下，泵揚(yáng)程曲線均存在明顯的馬鞍區(qū)；隨著葉片安放角的增大，試驗(yàn)泵馬鞍區(qū)的絕對(duì)位置向右上方偏移，但相對(duì)位置仍主要位于0.5BEP～0.6BEP（BEP為最高效率點(diǎn)對(duì)應(yīng)的額定流量），且均在0.55BEP時(shí)揚(yáng)程達(dá)到最小值;隨著葉片安放角的減小，馬鞍區(qū)內(nèi)相對(duì)揚(yáng)程在逐漸增大，馬鞍區(qū)駝峰特性有所改善；隨著葉片安放角的增大，各個(gè)安放角下馬鞍區(qū)范圍內(nèi)的壓力脈動(dòng)較最優(yōu)工況下更劇烈；葉輪進(jìn)口壓力脈動(dòng)主頻為葉片通過(guò)頻率，泵出口處壓力脈動(dòng)主要受導(dǎo)葉影響，隨流量減小逐漸向高頻移動(dòng)；隨著葉片安放角的增大，葉輪進(jìn)口和泵出口處主頻處的壓力脈動(dòng)幅值均逐漸增大，在葉輪進(jìn)口處，0.6BEP和0.55BEP時(shí)壓力脈動(dòng)幅值最大增幅分別達(dá)1.78和1.65倍，在泵出口處，正安放角下壓力脈動(dòng)幅值相對(duì)負(fù)角度有所增大；內(nèi)流分析表明小流量工況下葉輪進(jìn)口存在回流現(xiàn)象，葉輪出口靠近輪轂處有明顯旋渦，導(dǎo)致小流量下壓力脈動(dòng)幅值增大。

泵；壓力；葉片；軸流泵；葉片安放角；馬鞍區(qū)；水力特性

0 引 言

軸流泵是一種低揚(yáng)程泵，主要依靠葉輪的旋轉(zhuǎn)對(duì)液體產(chǎn)生的作用力使液體沿軸線方向輸送，廣泛應(yīng)用于南水北調(diào)、引嫩入白和三河三湖污染防治等國(guó)內(nèi)重大水利工程[1-3]，在農(nóng)業(yè)灌溉排澇、水環(huán)境治理、城市供水工程和生態(tài)需水工程等方面也發(fā)揮著不可替代的作用[4-6]。

軸流泵在啟動(dòng)或停機(jī)過(guò)程中一般都會(huì)經(jīng)過(guò)流量揚(yáng)程曲線的馬鞍區(qū)[7-9]，此時(shí)泵會(huì)伴隨有劇烈的振動(dòng)噪聲[10-12]，嚴(yán)重影響泵的運(yùn)行穩(wěn)定性和泵站系統(tǒng)的安全性[13-15]，長(zhǎng)時(shí)間處于這種狀態(tài)會(huì)嚴(yán)重影響泵的壽命[16-18]。因此，軸流泵馬鞍區(qū)的特性研究一直是行業(yè)熱點(diǎn)。

成立等[19]認(rèn)為水力不穩(wěn)定區(qū)的產(chǎn)生是由軸流泵旋轉(zhuǎn)失速與進(jìn)水條件惡化導(dǎo)致的。劉竹青等[20]對(duì)彎掠葉片和原型葉片高速軸流泵進(jìn)行全三維流道數(shù)值模擬，發(fā)現(xiàn)合理的彎掠葉片可有效改善原型葉片軸流泵出現(xiàn)的“駝峰區(qū)”。劉君等[21]結(jié)合不同工況的數(shù)值模擬，對(duì)模型泵的馬鞍形特性進(jìn)行了分析，發(fā)現(xiàn)造成軸流泵裝置模型效率下降和運(yùn)行不穩(wěn)定的直接原因是葉輪進(jìn)口輪緣和葉輪出口輪轂的二次回流。茅媛婷等[22]通過(guò)數(shù)值模擬和試驗(yàn)相結(jié)合的方法對(duì)軸流泵進(jìn)行了研究，發(fā)現(xiàn)馬鞍形區(qū)存在于大約50%～65%的設(shè)計(jì)流量區(qū)域。程千等[23]研究了前置導(dǎo)葉對(duì)軸流泵小流量工況下馬鞍區(qū)回流渦特性的影響，發(fā)現(xiàn)小流量工況下大量螺旋形回流出現(xiàn)在進(jìn)水流道，在剪切作用下與主流相互影響形成回流渦，引起泵內(nèi)能量損失，導(dǎo)致泵的水力特性下降。鄭源等[24]基于標(biāo)準(zhǔn)-湍流模型和SIMPLEC算法，對(duì)軸流泵裝置馬鞍區(qū)的流動(dòng)特性進(jìn)行了研究，發(fā)現(xiàn)小流量工況下，葉輪出口處存在大量的回流和旋渦，并伴隨著激烈的能量交換，導(dǎo)致軸流泵裝置出現(xiàn)馬鞍形區(qū)。宋希杰等[25]結(jié)合fluent非定常計(jì)算和模型試驗(yàn)研究了軸流泵進(jìn)水漩渦對(duì)壓力脈動(dòng)的影響，發(fā)現(xiàn)葉輪進(jìn)口斷面處的壓力脈動(dòng)與進(jìn)水漩渦誘發(fā)的脈動(dòng)之間存在同步性，漩渦影響著葉輪內(nèi)的壓力脈動(dòng)。石麗建等[26]采用CFD計(jì)算結(jié)合試驗(yàn)研究對(duì)軸流泵葉片進(jìn)行多工況優(yōu)化設(shè)計(jì)，研究結(jié)果使3個(gè)工況點(diǎn)的效率均有所提高，降低了運(yùn)行成本，縮短了優(yōu)化設(shè)計(jì)周期。謝榮盛[27]利用高速攝影試驗(yàn)和CFD仿真計(jì)算研究軸流泵失速形成的機(jī)理，發(fā)現(xiàn)軸流泵的流量揚(yáng)程和流量軸功率曲線出現(xiàn)拐點(diǎn)的原因是葉輪外側(cè)進(jìn)口的誘導(dǎo)速度增大，導(dǎo)致葉輪進(jìn)口沖角變小。Miyabe等[28]采用PIV技術(shù)進(jìn)行研究，發(fā)現(xiàn)在馬鞍區(qū)工況軸流泵運(yùn)行不穩(wěn)定性問(wèn)題十分突出。Goltz等[29-30]利用油流技術(shù)和高速攝影技術(shù)研究發(fā)現(xiàn)小流量工況下泵內(nèi)出現(xiàn)漩渦是導(dǎo)致泵內(nèi)壓力脈動(dòng)劇烈、性能下降的主要原因。Shigemitsu等[31]使用LDV技術(shù)測(cè)量了高比轉(zhuǎn)速軸流泵前后轉(zhuǎn)子之間的流場(chǎng)，揭示了水從前轉(zhuǎn)子流向后轉(zhuǎn)子的流動(dòng)規(guī)律，提出了一種軸流泵設(shè)計(jì)方案。

雖然目前有關(guān)軸流泵馬鞍區(qū)運(yùn)行特性的研究比較多，但葉片安放角對(duì)馬鞍區(qū)特性的影響的研究還比較少。本文采用試驗(yàn)和CFD數(shù)值計(jì)算相結(jié)合的方法對(duì)馬鞍區(qū)內(nèi)軸流泵的能量特性和壓力脈動(dòng)特性進(jìn)行了分析，研究了葉片安放角改變后軸流泵馬鞍區(qū)運(yùn)行特性的變化，研究結(jié)果可為提高軸流泵在小流量工況下的運(yùn)行穩(wěn)定性提供一定的參考。

1 試驗(yàn)?zāi)Ｐ?/h2>

1.1 試驗(yàn)對(duì)象

以比轉(zhuǎn)速s=822的軸流泵作為研究對(duì)象，其設(shè)計(jì)參數(shù)為流量d=0.33 m3/s、轉(zhuǎn)速=1 450 r/min、揚(yáng)程=6.05 m、比轉(zhuǎn)速s=822、葉片數(shù)=4、導(dǎo)葉葉片數(shù)d=6。模型泵的主要結(jié)構(gòu)參數(shù)：葉輪直徑=300mm，輪轂直徑h=135 mm。葉片安放角為葉片安置在輪轂上的角度，試驗(yàn)中葉輪原葉片安放角為0°，安放角通過(guò)葉片旋轉(zhuǎn)進(jìn)行調(diào)節(jié)；葉片安放角調(diào)節(jié)共有+4°、+2°、?2°和?4°等4個(gè)方案，其中正號(hào)表示逆時(shí)針旋轉(zhuǎn)葉片，負(fù)號(hào)反之。葉輪實(shí)物如圖1所示。

圖1 葉輪模型

1.2 試驗(yàn)系統(tǒng)

試驗(yàn)在江蘇大學(xué)國(guó)家水泵研究中心實(shí)驗(yàn)室進(jìn)行，試驗(yàn)裝置主要由汽蝕罐、模型泵、出水罐、增壓泵、穩(wěn)壓罐、進(jìn)水罐、電磁流量計(jì)、壓力傳感器等組成，試驗(yàn)臺(tái)結(jié)構(gòu)如圖2所示。

流量用開封儀表有限公司MF/C3511021100CR102電磁流量計(jì)測(cè)量，精確度為 0.3%；進(jìn)出口壓力用上海威爾泰儀器儀表有限公司W(wǎng)T2000智能壓力變送器測(cè)量，精度等級(jí)為0.1級(jí)非線性：≤±0.1%F.S（量程比＜10:1）；轉(zhuǎn)速由?，敼拘吞?hào)為AR926激光轉(zhuǎn)速測(cè)量?jī)x確定，分辨率為1 r/min，測(cè)量精度為0.1%；扭矩采用湘儀動(dòng)力測(cè)試儀器有限公司JW-3扭矩儀和JC型轉(zhuǎn)矩轉(zhuǎn)速傳感器測(cè)量，測(cè)量精度為±0.1% F.S；壓力脈動(dòng)傳感器采用成都泰斯特電子信息有限責(zé)任公司CY200數(shù)字壓力脈動(dòng)傳感器，傳感器采樣頻率1 000 Hz，綜合精度0.1%FS。

對(duì)軸流泵葉輪進(jìn)口測(cè)點(diǎn)P1和泵出口測(cè)點(diǎn)P2的壓力脈動(dòng)信號(hào)進(jìn)行測(cè)試，壓力脈動(dòng)測(cè)點(diǎn)如圖3所示。

1.電動(dòng)機(jī) 2.試驗(yàn)泵 3.進(jìn)口測(cè)壓孔 4.出口測(cè)壓孔 5.電動(dòng)閥 6.汽蝕罐 7.電動(dòng)閥 8.流量計(jì) 9.穩(wěn)壓罐 10.增壓泵

1.Electromotor 2.Test pump 3.Inlet pressure measurement hole 4.Onlet pressure measurement hole 5.Electric valve 6.Cavitation tank 7.Electric valve 8.Flowmeter 9.Steadying pressure-pump 10.Booster pump

注：汽蝕罐外接真空泵。

Notice: Cavitation tank is connected with the vacuum pump.

圖2 模型泵測(cè)試試驗(yàn)臺(tái)

Fig.2 Test rig of model pump

注：P1為軸流泵葉輪進(jìn)口測(cè)點(diǎn)，P2為泵出口測(cè)點(diǎn)。

2 試驗(yàn)結(jié)果分析

2.1 能量特性曲線

圖4給出了不同葉片安放角下泵的能量特性曲線。從圖4中可以看出，葉片安放角為+4°、+2°、?2°和?4°時(shí)，各個(gè)安放角下最高效率點(diǎn)分別位于0.364、0.34、0.299和0.273m3/s流量工況；+4°和+2°最優(yōu)工況處流量較葉片安放角為0°時(shí)分別提高了15.5%和9.8%，?2°和?4°時(shí)最優(yōu)工況處流量較葉片安放角為0°時(shí)分別降低了5%和13.3%。從?4°變化到+4°最優(yōu)工況處揚(yáng)程、流量和效率分別增大了10.4%、26.7%和0.87%。

圖4中揚(yáng)程的增加是由于隨著葉片安放角的增大，葉輪出口速度的圓周分量增加，根據(jù)泵的基本方程（1）可知，揚(yáng)程必定會(huì)增加；隨著葉片安放角的增大，葉片液流軸面速度也在增加，因此流量也會(huì)增大。

式中Ht為理論揚(yáng)程，m；ω為葉片旋轉(zhuǎn)角速度，rad/s；vu2為葉輪出口絕對(duì)速度圓周分量，m/s；R2為葉輪出口半徑，m；vu1為葉輪進(jìn)口絕對(duì)速度圓周分量，m/s；R1為葉輪進(jìn)口半徑，m；g為重力加速度，g=9.8 m/s2。

圖4表明各個(gè)安放角下模型泵-曲線均存在明顯的馬鞍區(qū)，并且隨著葉片安放角的增大，馬鞍區(qū)逐漸向右上方偏移。統(tǒng)計(jì)了不同葉片安放角下馬鞍區(qū)相對(duì)區(qū)域，如表1所示。

表1 不同葉片安放角下馬鞍區(qū)范圍

注：BEP為最高效率點(diǎn)對(duì)應(yīng)的額定流量，-4°到+4°分別為0.364、0.34、0.33、0.299和0.273 m3·s-1。葉片安放角正號(hào)表示逆時(shí)針旋轉(zhuǎn)葉片，負(fù)號(hào)反之。

Note:BEPrepresents rated flow when efficiency reaches the maximum, andBEPare 0.364, 0.34, 0.33, 0.299 and 0.273 m3·s-1from -4° to +4° respectively. The positive vane angles represent that the blade is rotated counterclockwise, and the negative is reversed.

由表1可知，隨著葉片安放角的增大，馬鞍區(qū)的相對(duì)位置發(fā)生了一定的改變，但變化幅度比較小，基本可以認(rèn)為馬鞍區(qū)范圍仍在0.5BEP～0.6BEP區(qū)間內(nèi)，且在0.55BEP附近工況下?lián)P程在馬鞍區(qū)內(nèi)達(dá)到最小值。

為了衡量馬鞍區(qū)內(nèi)駝峰程度，引入“相對(duì)揚(yáng)程系數(shù)”的概念，其定義為：各角度下馬鞍區(qū)最低點(diǎn)0.55BEP處的揚(yáng)程與最優(yōu)工況揚(yáng)程的比值，該值越大越說(shuō)明泵的馬鞍區(qū)駝峰較小。

葉片安放角為+4°、+2°、0°、?2°和?4°時(shí)的相對(duì)揚(yáng)程系數(shù)分別為1.69、1.96、2.08、2.43、2.85，可見(jiàn)隨著葉片安放角的減小，相對(duì)揚(yáng)程系數(shù)在逐漸增大，說(shuō)明隨著葉片安放角的減小，馬鞍區(qū)駝峰情況有所改善。

綜合以上分析，隨著葉片安放角的增大，馬鞍區(qū)的絕對(duì)位置向右上方偏移，但馬鞍區(qū)的相對(duì)位置仍主要位于0.5BEP～0.6BEP流量范圍內(nèi)；葉片安放角的減小可以改善馬鞍區(qū)的駝峰程度。

2.2 葉輪進(jìn)口的壓力脈動(dòng)特性分析

2.2.1 壓力脈動(dòng)特性時(shí)域分析

為了進(jìn)一步分析葉片安放角對(duì)軸流泵內(nèi)壓力脈動(dòng)的影響，對(duì)0.55BEP、0.6BEP和1.0BEP3個(gè)不同工況下軸流泵葉輪進(jìn)口P1點(diǎn)的壓力脈動(dòng)信號(hào)進(jìn)行時(shí)域分析，軸流泵葉輪旋轉(zhuǎn)一圈的時(shí)間為，用表示時(shí)間內(nèi)周期的個(gè)數(shù)，則=/。用壓力脈動(dòng)系數(shù)p來(lái)表示壓力脈動(dòng)幅值。

圖5為葉片安放角+4°、+2°、0°、?2°和?4°時(shí)葉輪進(jìn)口P1處壓力脈動(dòng)時(shí)域圖。由圖6可知，不同葉片安放角時(shí)最優(yōu)工況下葉輪進(jìn)口P1處的壓力脈動(dòng)單個(gè)周期內(nèi)4波峰4波谷的特征比較明顯，與葉輪葉片數(shù)相同，故葉輪進(jìn)口處壓力脈動(dòng)主要受葉輪影響。

圖5中各安放角下葉輪進(jìn)口P1處的壓力脈動(dòng)峰峰值隨著流量的減小逐漸增大；1.0BEP到0.6BEP工況時(shí)，各葉片安放角下壓力脈動(dòng)峰峰值變化較??；0.6BEP到0.55BEP工況時(shí)，各個(gè)葉片安放角下的壓力脈動(dòng)峰峰值變化劇烈，這是由于隨著流量的減小泵內(nèi)出逐漸現(xiàn)了回流和失速等不穩(wěn)定流動(dòng)，使得泵內(nèi)部流動(dòng)狀態(tài)進(jìn)一步惡化，從而導(dǎo)致壓力波動(dòng)更加劇烈。

2.2.2 壓力脈動(dòng)特性頻域分析

對(duì)壓力脈動(dòng)時(shí)域信號(hào)進(jìn)行傅里葉變換，分析其頻率成分。壓力脈動(dòng)傳感器采樣頻率s為1 000 Hz，取=10 000個(gè)采樣點(diǎn)的數(shù)據(jù)進(jìn)行傅里葉分析，頻率分辨率D=s/=0.1 Hz。試驗(yàn)泵葉輪葉片數(shù)為4，導(dǎo)葉葉片數(shù)6，轉(zhuǎn)速為1 450 r/min，因此葉頻（blade passing frequency，BPF）為96 Hz，軸頻（axial passing frequency，APF）為24 Hz。用p代表葉頻，n代表軸頻，p=4n。圖6為葉輪進(jìn)口P1處在不同葉片安放角下的壓力脈動(dòng)頻域圖。

由圖6可知，在馬鞍區(qū)工況內(nèi)，各安放角下壓力脈動(dòng)幅值較最優(yōu)工況明顯增大，隨著葉片安放角的增大，葉輪進(jìn)口P1處出現(xiàn)更多的低頻脈動(dòng)；不同流量各個(gè)葉片安放角下壓力脈動(dòng)峰值主要位于軸頻p及其諧頻處，且不同葉片安放角下壓力脈動(dòng)的主頻均為葉頻p；隨著葉片安放角的增大，不同流量工況下主頻處的壓力脈動(dòng)幅值均逐漸增大，0.6BEP時(shí)壓力脈動(dòng)幅值最大增幅達(dá)1.78倍，0.55BEP時(shí)壓力脈動(dòng)幅值最大增幅達(dá)1.65倍。

圖5 不同葉片安放角下葉輪進(jìn)口P1處壓力脈動(dòng)時(shí)域圖

圖6 多工況下葉輪進(jìn)口P1處壓力脈動(dòng)頻域圖

2.3 泵出口壓力脈動(dòng)特性分析

2.3.1 壓力脈動(dòng)時(shí)域分析

圖7為葉片安放角+4°、+2°、0°、-2°和-4°時(shí)泵出口P2處壓力脈動(dòng)時(shí)域圖。由圖7可知，與葉輪進(jìn)口相似，不同葉片安放角時(shí)最優(yōu)工況下泵出口P2處壓力脈動(dòng)曲線為規(guī)則的正弦波形，各個(gè)周期內(nèi)同樣存在4波峰4波谷特性；泵出口P2處的壓力脈動(dòng)峰峰值隨著流量的減小逐漸增大；馬鞍區(qū)內(nèi)壓力脈動(dòng)峰峰值明顯大于最優(yōu)工況下，且馬鞍區(qū)內(nèi)的波動(dòng)規(guī)律性較差；隨著葉片安放角的增大，0.6BEP工況下的壓力脈動(dòng)波動(dòng)變得劇烈，0.55BEP工況下壓力脈動(dòng)出現(xiàn)先增大后減小的趨勢(shì)。

圖7中各安放角下泵出口的壓力脈動(dòng)峰峰值較葉輪進(jìn)口處明顯降低，這應(yīng)該是由于導(dǎo)葉對(duì)流體的整流作用。隨著相對(duì)流量的減小，各安放角下壓力脈動(dòng)峰峰值在逐漸增大；隨著葉片安放角的增大，泵出口處的壓力脈動(dòng)峰峰值也逐漸增大，壓力脈動(dòng)變得劇烈。

2.3.2 壓力脈動(dòng)頻域分析

圖8為不同葉片安放角下泵出口P2的壓力脈動(dòng)頻域圖。從圖8可以看出，泵出口處主頻隨流量減小逐漸向高頻移動(dòng)；馬鞍區(qū)工況下壓力脈動(dòng)主頻基本穩(wěn)定在6倍軸頻（axial passing frequency），次頻穩(wěn)定在4倍軸頻（axial passing frequency），說(shuō)明了泵出口壓力脈動(dòng)主要受導(dǎo)葉的影響，同時(shí)也受葉輪的影響；隨著葉片安放角的增大，馬鞍區(qū)工況內(nèi)泵出口處的低頻脈動(dòng)變化劇烈，與葉輪進(jìn)口一致，表明泵出口的壓力脈動(dòng)受著葉輪處流動(dòng)分離的影響；隨著相對(duì)流量減小至馬鞍區(qū)，同一葉片安放角下壓力脈動(dòng)的幅值明顯增大，這可能是由于流量減小時(shí)出水彎管內(nèi)產(chǎn)生的旋渦導(dǎo)致的；正安放角下壓力脈動(dòng)幅值相對(duì)負(fù)角度有所增大，葉片安放角為-4°，-2°，+2°和+4°時(shí)最優(yōu)工況下壓力脈動(dòng)幅值分別為0°的0.32，0.32，0.56和0.76倍，馬鞍區(qū)最低點(diǎn)0.55BEP下壓力脈動(dòng)幅值分別為0°的0.66，0.48，0.47和0.82倍，這可能是因?yàn)殡S著葉片安放角的增大，流體軸面速度增大，過(guò)流面積增大，泵出口處螺旋出流加劇，導(dǎo)致壓力脈動(dòng)的增幅。

圖7 不同葉片安放角下泵出口P2處壓力脈動(dòng)時(shí)域圖

圖8 多工況下泵出口P2處壓力脈動(dòng)頻域圖

3 泵內(nèi)CFD內(nèi)流分析

為了進(jìn)一步分析泵內(nèi)壓力脈動(dòng)的變化規(guī)律，圖9給出了葉片安放角為0°時(shí)的模型泵葉輪內(nèi)不同工況下的流線分布。從圖9可以清晰地看出，在最優(yōu)工況下，葉輪內(nèi)部流線分布較均勻。到0.6BEP工況，模型泵開始進(jìn)入馬鞍區(qū)，由于流動(dòng)分離在葉輪進(jìn)口前靠近輪緣處出現(xiàn)了回流，同時(shí)在葉輪出口靠近輪轂處產(chǎn)生了較大的渦，說(shuō)明了此時(shí)泵內(nèi)已經(jīng)出現(xiàn)了很多不穩(wěn)定流動(dòng)；0.55BEP工況較0.6BEP工況葉輪進(jìn)口前的回流明顯加強(qiáng)，同時(shí)葉輪出口靠近輪轂處的渦逐漸擴(kuò)大，接近失速。因此，在小流量工況下葉輪進(jìn)口存在著回流現(xiàn)象，葉輪出口靠近輪轂處存在著明顯旋渦，這就導(dǎo)致了小流量下模型泵內(nèi)部流動(dòng)狀態(tài)紊亂，軸流泵內(nèi)部壓力脈動(dòng)變得劇烈。

圖9 葉片安放角為0°時(shí)葉輪流線分布

4 結(jié)論與討論

1）隨著葉片安放角的增大，軸流泵馬鞍區(qū)內(nèi)的揚(yáng)程、流量和效率均逐漸增大，從?4°變化到+4°，最優(yōu)工況處揚(yáng)程、流量和效率分別增大了10.4%、26.7%和0.87%；+4°和+2°最優(yōu)工況處流量較0°安放角下分別提高了15.5%和9.8%，?2°和?4°時(shí)最優(yōu)工況處流量較0°安放角下分別降低了5%和13.3%。

2）隨著葉片安放角的增大，試驗(yàn)泵馬鞍區(qū)逐漸向右上方偏移，且均在0.55BEP附近工況揚(yáng)程達(dá)到最小值；隨著葉片安放角的減小，馬鞍區(qū)駝峰特性有所改善。

3）在0.55BEP～0.6BEP即馬鞍區(qū)范圍內(nèi)，各個(gè)安放角下的壓力脈動(dòng)較最優(yōu)工況下更劇烈；葉輪進(jìn)口壓力脈動(dòng)主頻為葉片通過(guò)頻率，泵出口處主要受導(dǎo)葉影響；各安放角下泵出口處壓力脈動(dòng)幅值較葉輪進(jìn)口處明顯降低。

4）在馬鞍區(qū)工況下，隨著葉片安放角的增大，葉輪進(jìn)口和泵出口處主頻處的壓力脈動(dòng)幅值均逐漸增大，在葉輪進(jìn)口處，0.6BEP和0.55BEP時(shí)壓力脈動(dòng)幅值最大增幅分別達(dá)1.78和1.65倍，在泵出口處，正安放角下壓力脈動(dòng)幅值相對(duì)負(fù)角度有所增大。

5）小流量工況下葉輪進(jìn)口存在回流現(xiàn)象，葉輪出口靠近輪轂處存在旋渦，使小流量下壓力脈動(dòng)幅值增大。

本文主要研究了軸流泵馬鞍區(qū)內(nèi)的能量特性和壓力脈動(dòng)特性，但研究還存在很多不足，未來(lái)建議采用三維粒子圖像測(cè)速和高速攝影技術(shù)對(duì)馬鞍區(qū)內(nèi)流場(chǎng)進(jìn)行試驗(yàn)測(cè)試。

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Effect of vane angle on axial flow pump running characteristics in saddle zone

Wu Xianfang1, Lu Youdong2, Tan Minggao2, Liu Houlin2

(1.,,212013,; 2.,,212013,)

In order to analyze the influence of the vane angle on the performance in saddle zone of the axial flow pump, the operation characteristics with different vane angles were tested by the axial flow pump with specific speed of 822 RPM. The research shows that with the increase of vane angle, the head, flow and efficiency of the test pump increase at the optimal working conditions at the same time, and the increase ranges are 10.4%, 26.7% and 0.87% respectively when vane angle changes from -4° to +4°. Under different vane angles, the head curves all present obvious saddle area. With the increase of the vane angle, the coefficient of relative head decreases gradually. It shows that the performance of saddle area is improved with the decrease of the vane angle. The absolute position in the saddle zone of the test pump deviates to the upper right, but the relative position is still mainly located in the range of 0.5BEP-0.6BEP(BEPis the flow when efficiency reaches the maximum), and the head reaches a minimum at 0.55BEP. The pressure pulsation at monitoring point of impeller inlet under different vane angels is obvious with the feature of 4 peaks and 4 troughs in a single cycle. Under the optimal operating conditions, the pressure fluctuation curve at monitoring point of pump outlet is a regular sine wave, and there are also 4 wave peaks and 4 wave valleys in each cycle, and the peak value of pressure fluctuating peak at monitoring point of pump outlet increase with the decrease of flow rate. With the change of vane angles, the peak value of the pressure fluctuating peak in the saddle area is obviously larger than the optimal operating condition at the monitoring points ofimpeller inlet and pump outlet. With the increase of the vane angle, the pressure fluctuation in the 0.6BEPbecomes intense, and the pressure fluctuation in the 0.55BEPincreases first and then decreases. When the vane angle increases, the flow rate at monitoring point of impeller inlet decreases and when the flow changes from 1.0BEPto 0.6BEP, the peak value of the pressure fluctuating peak changes gradually, and the pressure fluctuating peak value of each angle changes violently as the flow changes from 0.6BEPto 0.55BEP. With the decrease of the relative flow, the pressure pulsation under different vane angles increases gradually. When the relative flow reached the range of saddle area, the amplitude of low frequency pulsation increases gradually, and when the flow rate continues to decrease, the broadband frequency distribution moves to the low frequency band, and the amplitude of low frequency increases. The main frequency of pressure pulsation at the pump outlet in the saddle area is basically stable at 6 APF (axial passing frequency) and the secondary frequency is stable at 4 APF. It shows that the pressure pulsation of the pump outlet is mainly influenced by the guide vane, and is also influenced by the blade passing frequency. The main frequency of the pressure pulsation at impeller inlet is the blade passing frequency, as the main frequency at the pump outlet is the guide vane passing frequency, and it moves to high frequency with the decrease of flow gradually. With the increase of the vane angle, the amplitudes of main frequency of pressure fluctuation at the impeller inlet, guide vane and pump outlet all gradually increase. At the impeller inlet, the maximum amplitudes of pressure fluctuation at 0.6BEPand 0.55BEPwere 1.78 and 1.65 times respectively, and at the outlet of the pump, the amplitude of pressure pulsation at the positive angles is increased relative to the negative angles. Finally, the results of numerical simulation show that there is a backflow phenomenon at the impeller inlet under the small flow condition, and the vortex near the hub leads to the increase of the pressure fluctuation amplitude in the small flow condition.

pumps; pressure; blades; axial flow pump; vane angle; saddle zone; hydraulic performance

2018-01-21

2018-06-15

國(guó)家自然科學(xué)基金資助項(xiàng)目（51509109，51779108）；江蘇省自然科學(xué)基金（BK20161350）；江蘇省現(xiàn)代農(nóng)業(yè)重點(diǎn)研發(fā)計(jì)劃（BE2017356）；江蘇高校優(yōu)勢(shì)學(xué)科建設(shè)工程資助項(xiàng)目（PAPD）

吳賢芳，副教授，主要研究方向現(xiàn)代泵理論設(shè)計(jì)與方法。Email：wxftmg@ujs.edu.cn

10.11975/j.issn.1002-6819.2018.17.007

TH312

A

1002-6819(2018)-17-0046-08

吳賢芳，陸友東，談明高，劉厚林. 葉片安放角對(duì)軸流泵馬鞍區(qū)運(yùn)行特性的影響[J]. 農(nóng)業(yè)工程學(xué)報(bào)，2018，34(17)：46－53. doi：10.11975/j.issn.1002-6819.2018.17.007 http://www.tcsae.org

Wu Xianfang, Lu Youdong, Tan Minggao, Liu Houlin. Effect of vane angle on axial flow pump running characteristics in saddle zone[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(17): 46－53. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2018.17.007 http://www.tcsae.org