【摘要】：反應(yīng)堆冷卻劑泵(核主泵)為核反應(yīng)堆提供驅(qū)動壓頭,是核電站中最核心的設(shè)備之一。在發(fā)生小破口失水事故后,由于壓力條件的改變和冷卻劑的汽化,核主泵將會在復(fù)雜的汽液兩相流工況下運行。由于水蒸汽的變化非常復(fù)雜,參考相關(guān)研究,本文用空氣代替水蒸汽進行汽液兩相流數(shù)值模擬。根據(jù)現(xiàn)有的比較成熟的核主泵水力模型,設(shè)計并制造出相應(yīng)的水力樣機,并在水力樣機上進行試驗研究,通過對比試驗數(shù)據(jù)和模擬結(jié)果數(shù)據(jù),發(fā)現(xiàn):液相工況下兩者具有較高的吻合度,在低含氣率工況下的吻合程度優(yōu)于在高含氣率工況,說明數(shù)值模擬的方法是可信的。為了解核主泵在氣液兩相流工況下運行的流動特性,對現(xiàn)有的比較成熟的核主泵模型進行了不同含氣率工況下定常和非定常數(shù)值模擬。通過定常數(shù)值模擬,揭示了不同含氣率下核主泵外特性曲線、內(nèi)部氣體分布和速度矢量云圖的變化規(guī)律:由于離心力和壓力梯度的作用造成葉輪進口和背面位置容易出現(xiàn)氣體聚集現(xiàn)象;扭曲型徑向空間導(dǎo)葉結(jié)構(gòu)容易造成氣體滯留現(xiàn)象;類球形的蝸殼結(jié)構(gòu)容易造成局部氣體聚集區(qū)。通過非定常數(shù)值模擬,揭示了含氣率對壓力脈動影響的規(guī)律:含氣率和葉輪出口處壓力不均勻分布存在一定的正相關(guān)性;較高含氣率對葉輪出口處壓力不均勻分布和葉輪工作面處壓力脈動波動幅度都具有加強作用;含氣率與導(dǎo)葉內(nèi)壓力脈動波動幅度呈負(fù)相關(guān)性。為進一步了解核主泵在兩相流工況下的運動特性,對核主泵的反轉(zhuǎn)全工況不同含氣率下的泵水力性能、流道內(nèi)部氣體體積分布情況進行分析,發(fā)現(xiàn):隨著含氣率的增大,核主泵揚程曲線和扭矩曲線的下降速度變慢;隨著流量的增大,在反轉(zhuǎn)逆流制動工況和反轉(zhuǎn)水泵工況,含氣率對于核主泵扭矩特性的影響逐漸減弱,在反轉(zhuǎn)正流制動工況剛好相反;在反轉(zhuǎn)逆流制動工況和反轉(zhuǎn)水泵工況,高含氣率主要集中在葉輪葉片進口前區(qū)域,在葉輪流道內(nèi)氣體體積分?jǐn)?shù)分布極其不均勻。當(dāng)一回路發(fā)生失水事故后,核主泵將會在汽液兩相流工況下運行,此時核主泵的性能將會發(fā)生復(fù)雜的變化,為探究其性能的變化規(guī)律對核主泵進行了小破口失水事故下的瞬態(tài)模擬。通過數(shù)值模擬,得到了含氣率對核主泵非穩(wěn)態(tài)特性的影響規(guī)律:隨著含氣率不斷增加、流量值持續(xù)減小,核主泵的軸扭矩和效率都出現(xiàn)下降,小的變化規(guī)律揚程值出現(xiàn)先增大后減;隨著含氣率逐漸增大,在葉輪進口背面、中間后蓋板處和出口背面處出現(xiàn)較高程度的氣體聚集現(xiàn)象,導(dǎo)葉內(nèi)沿液流方向含氣率波動幅度逐漸減小且具有明顯的跟隨性;瞬態(tài)徑向力隨含氣率增大逐漸變小且兩類徑向力極大值的差值變小,葉輪和類隔舌處瞬態(tài)壓力出現(xiàn)先增大后減小的變化規(guī)律,沿液流方向?qū)~內(nèi)壓力逐漸增大但波動程度減弱;隨著含氣率的增大,蝸殼內(nèi)的低速區(qū)不斷擴大,說明類球形蝸殼不利于氣體的順利出流。在結(jié)合多種優(yōu)化方法的基礎(chǔ)上,采用經(jīng)過驗證的數(shù)值模擬方法,對核主泵的葉輪進行優(yōu)化設(shè)計。為了設(shè)計出在液相和低含氣率下具有優(yōu)秀水力性能的核主泵水力模型,選取葉輪進口直徑Dj、葉片包角φ、葉片出口寬度b2、葉輪出口平均直徑D2、葉輪出口安放角β2、葉片出口傾斜角γ和葉片數(shù)Z7個對核主泵外特性影響較大的因素進行正交試驗設(shè)計。通過設(shè)計,得到了一組最佳的葉輪幾何參數(shù)組合,以及7個因素對核主泵在液相和較低含氣率工況下外特性影響的主次順序;根據(jù)得到的參數(shù)對泵外特性影響主次順序表,選取出口安放角和包角作為進一步優(yōu)化的參數(shù),通過進一步優(yōu)化得到了使核主泵在液相和低含氣率下具有優(yōu)秀水力性能的最優(yōu)葉輪幾何參數(shù)組合。
[Abstract]:Reactor coolant pump (nuclear main pump) is one of the most important equipments in nuclear power plant, which provides the driving pressure head for nuclear reactor. In this paper, air is used to simulate the vapor-liquid two-phase flow instead of water vapor. According to the existing mature hydraulic model of nuclear main pump, the corresponding hydraulic prototype is designed and manufactured, and the experimental study is carried out on the hydraulic prototype. In order to understand the flow characteristics of the nuclear main pump under the gas-liquid two-phase flow condition, the steady and unsteady numerical simulation of the existing mature nuclear main pump model under different gas holdup conditions was carried out. The simulation results reveal the variation laws of gas distribution and velocity vector nephogram of the main nuclear pump under different air content: gas accumulation is easy to occur at the inlet and back of the impeller due to the action of centrifugal force and pressure gradient; gas trapping is easy to occur in the twisted radial guide vane structure; the spherical volute is easy to occur; the gas trapping phenomenon is caused by the twisted radial guide vane structure. The unsteady numerical simulation reveals that there is a certain positive correlation between the gas holdup and the uneven distribution of pressure at the impeller outlet, and that the uneven distribution of pressure at the impeller outlet and the amplitude of pressure fluctuation at the impeller working face are both affected by the higher gas holdup. In order to further understand the movement characteristics of the nuclear main pump under two-phase flow conditions, the hydraulic performance and the gas volume distribution in the flow passage of the nuclear main pump were analyzed under different air content in the reversed full working condition. With the increase of flow rate, the influence of void fraction on the torque characteristics of the nuclear main pump decreases gradually under the reverse flow braking condition and the reverse pump condition, but the reverse flow braking condition is just the opposite; under the reverse flow braking condition and the reverse pump condition, the high void fraction mainly concentrates on the blades. The gas volume fraction distribution in the impeller passage is extremely uneven in the region before the blade inlet. When the loss of water accident occurs in the loop, the nuclear main pump will operate under the condition of vapor-liquid two-phase flow. At this time, the performance of the nuclear main pump will have complex changes. Transient simulation. The influence of void fraction on the unsteady characteristics of the nuclear main pump is obtained by numerical simulation. With the increase of void fraction, the flow rate decreases continuously, the shaft torque and efficiency of the nuclear main pump decrease, and the small change law of the head value increases first and then decreases; with the increase of void fraction, the back of the impeller inlet and the middle back appear. High degree of gas accumulation occurs at the cover plate and the back of the outlet, and the fluctuation amplitude of gas holdup in the guide vane decreases gradually along the direction of liquid flow with obvious follow-up; the transient radial force decreases gradually with the increase of gas holdup and the difference between the maximum values of the two kinds of radial force decreases, and the transient pressure at the impeller and the tongue separation increases first and then decreases. The pressure in the guide vane increases gradually along the direction of liquid flow, but the fluctuation degree decreases. With the increase of air content, the low-speed region in the volute expands continuously, which indicates that the spherical volute is not conducive to the smooth outflow of gas. In order to design the hydraulic model of nuclear main pump with excellent hydraulic performance in liquid phase and low void content, the impeller inlet diameter Dj, blade envelope angle phi, blade outlet width b2, impeller outlet average diameter D2, impeller outlet placement angle beta 2, blade outlet inclination angle gamma and blade number Z7 are selected as the main factors which have great influence on the external characteristics of nuclear main pump. Orthogonal experimental design was carried out. Through the design, a set of optimum impeller geometric parameters and the order of seven factors affecting the external characteristics of the nuclear main pump in the liquid phase and low air content conditions were obtained. According to the sequence table of parameters affecting the external characteristics of the pump, the outlet placement angle and the envelope angle were selected as further optimization. Through further optimization, the optimal impeller geometric parameters combination was obtained to make the nuclear main pump have excellent hydraulic performance in liquid phase and low void content.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM623

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本文編號：2214913