環(huán)形密封瞬態(tài)流場模擬及其動力學(xué)特性研究
發(fā)布時間：2018-08-17 09:29
【摘要】：環(huán)形密封是離心泵內(nèi)部關(guān)鍵結(jié)構(gòu),主要用于抑制內(nèi)泄漏及平衡葉輪軸向推力,如葉輪口環(huán)、級間密封、迷宮密封、平衡盤環(huán)形間隙等。這些環(huán)形流道一般間隙很小,并且兩端壓差很大。流經(jīng)環(huán)形間隙的高壓泄漏流,會對旋轉(zhuǎn)的軸系部件產(chǎn)生動態(tài)激勵作用,影響軸系的振動特性和運行穩(wěn)定性。環(huán)形密封間隙動力學(xué)在上世紀得到了長足的發(fā)展,其分析方法也從一開始的短密封理論、有限長密封理論,逐步發(fā)展到了三維CFD方法。然而,目前的研究方向仍側(cè)重于各類同心密封在偏心小擾動下所表現(xiàn)出的線性動力學(xué)特性。而環(huán)形密封在轉(zhuǎn)子傾斜擾動、上游來流不均勻、轉(zhuǎn)子大偏心和大擾動等狀態(tài)下所表現(xiàn)出的非線性動力學(xué)特性,卻未得到充分研究。另外,對于被廣泛采用的準穩(wěn)態(tài)模擬方法的不足之處以及它所帶來的誤差,也亟需進一步研究和確認。對這些關(guān)鍵問題的探討和解決,無疑將豐富水力機械環(huán)形密封動力學(xué)理論體系,進而促進轉(zhuǎn)子系統(tǒng)流激振動特性的理論研究和工程分析。本文以離心泵內(nèi)光滑壁面環(huán)形密封為研究對象,發(fā)展用于間隙流動模擬和動力學(xué)分析的動網(wǎng)格模型和瞬態(tài)CFD模擬方法,結(jié)合實驗測試,針對大偏心、大擾動和轉(zhuǎn)子傾斜擾動條件下的非線性間隙密封動力學(xué)問題開展研究。同時還面向離心泵,建立了轉(zhuǎn)子-密封系統(tǒng)非線性流固耦合分析模型,適合于復(fù)雜轉(zhuǎn)子/軸承／密封系統(tǒng)的動力學(xué)研究。論文的主要內(nèi)容包括以下五個方面：1、介紹了用于同心環(huán)形密封動力學(xué)特性研究的常用CFD模擬方法,分析了傳統(tǒng)準穩(wěn)態(tài)CFD方法的不足之處,并提出了改進的方法。基于插值理論,發(fā)展了環(huán)形密封流場的動網(wǎng)格模型,進而給出了用于環(huán)形密封動力學(xué)研究的瞬態(tài)CFD方法。基于實驗裝置,對泵葉輪口環(huán)流體力進行了測試,驗證了所提出計算方法的準確性和計算精度。采用大長徑比液體密封,探討了影響動特性系數(shù)計算精度的關(guān)鍵因素,著重討論了準穩(wěn)態(tài)模擬方法和瞬態(tài)模擬方法的異同點及優(yōu)劣勢。2、類比于偏心擾動,給出了傾斜擾動時同心密封動特性系數(shù)的識別方法。鑒于完全瞬態(tài)CFD模擬方法的高耗時性,基于變速渦動思想提出了一種快速求解模式,用于計算液體密封的全部(偏心和傾斜)動特性系數(shù)。通過實驗對比,評估了所提出瞬態(tài)方法的可行性。為了突顯轉(zhuǎn)子傾斜激勵作用,研究了轉(zhuǎn)子復(fù)合(偏心和傾斜)渦動下的密封流體力,以及密封長徑比對兩類(偏心和傾斜)動特性系數(shù)大小關(guān)系的影響。3、建立了包括完整上游流域的環(huán)形密封模型,研究了非均勻來流對密封動力學(xué)特性的影響�；谒矐B(tài)CFD模擬,研究了不均勻來流下環(huán)形密封的剛度系數(shù)以及流體激振力。通過對比均勻來流下的動力學(xué)特性,首次提出了考慮上游來流非均勻性的線性密封力模型。4、基于瞬態(tài)CFD模擬方法,計算了環(huán)形密封在不同偏心下的動特性系數(shù)及泄漏量,并進行了實驗驗證。探討了轉(zhuǎn)子擾動量對偏心密封動特性系數(shù)的影響,以研究線性假設(shè)的適用范圍。為了表述密封流體的非線性激勵,基于Muszynska非線性模型和CFD模擬,擬合出了非線性密封力模型。借助于非線性模型以及瞬態(tài)CFD模擬,計算了環(huán)形密封在各種大擾動下的流體激勵作用,進而探討了密封在大偏心和大擾動下的動力學(xué)特性。5、為了更好地考慮環(huán)形密封的非線性特性,通過編寫密封流場與轉(zhuǎn)子結(jié)構(gòu)場的交互程序平臺,建立了轉(zhuǎn)子-密封系統(tǒng)的流固耦合分析模型,并完成了耦合模型的分析和驗證。研究結(jié)果顯示,本文發(fā)展的環(huán)形小間隙流場的動網(wǎng)格模型和瞬態(tài)計算方法具有良好的計算性能,可適用于各種大長徑比以及復(fù)雜轉(zhuǎn)子擾動條件下的間隙動力學(xué)分析。傳統(tǒng)準穩(wěn)態(tài)CFD模擬方法、改進準穩(wěn)態(tài)CFD模擬方法和瞬態(tài)CFD模擬方法的計算精度和可靠性依次上升,結(jié)果還顯示準穩(wěn)態(tài)假設(shè)會導(dǎo)致密封主質(zhì)量系數(shù)的嚴重低估,而瞬態(tài)CFD模擬方法則可以準確預(yù)測。本文提出的基于變速渦動的瞬態(tài)模擬方法能夠在保持原有精度的同時,減少計算耗時現(xiàn)狀,可用于復(fù)雜液體密封的動力學(xué)研究。隨著密封長徑比的增加,兩類(偏心和傾斜)動特性系數(shù)的差距呈縮小趨勢,尤其是主剛度系數(shù)。因此,對于大長徑比環(huán)形間隙密封,轉(zhuǎn)子傾斜擾動引起的密封流體激勵不應(yīng)被忽略。除入口預(yù)旋和入口損失之外,入口流動的均勻性也對密封剛度影響很大。在大偏心下,環(huán)形密封動力學(xué)特性對轉(zhuǎn)子擾動量非常敏感,極易表現(xiàn)出非線性特性；此外,間隙動力學(xué)特性還與轉(zhuǎn)子的運動形式有關(guān),可能導(dǎo)致非線性密封力模型在大偏心下的可靠性較差。對于這種情況,建立包括密封流場和轉(zhuǎn)子結(jié)構(gòu)場的流固耦合分析方法,將是一個很好的解決思路。本文研究內(nèi)容和結(jié)論為液體環(huán)形間隙密封及轉(zhuǎn)子／密封系統(tǒng)動力學(xué)特性的理論研究及工程分析提供依據(jù)和支撐。
[Abstract]:Annular seal is the key structure in centrifugal pump, which is mainly used to restrain internal leakage and balance axial thrust of impeller, such as impeller orifice ring, stage seal, labyrinth seal, balance disk annular clearance, etc. These annular flow passages generally have small clearance and large pressure difference between the two ends. Dynamic excitation affects the vibration characteristics and operation stability of shafting. The dynamics of annular seal clearance has been greatly developed in the last century, and its analysis method has been gradually developed from short seal theory and finite length seal theory to three-dimensional CFD method. However, the nonlinear dynamic characteristics of the ring seal under the condition of rotor tilt disturbance, upstream incoming flow nonuniformity, large eccentricity and large disturbance have not been fully studied. The study and solution of these key problems will undoubtedly enrich the dynamic theoretical system of the ring seal of hydraulic machinery and promote the theoretical study and engineering analysis of the flow-induced vibration characteristics of the rotor system. The dynamic mesh model and the transient CFD simulation method of gap flow simulation and dynamic analysis were used to study the nonlinear dynamic problems of gap seal under the conditions of large eccentricity, large disturbance and rotor tilt disturbance. The main contents of this paper include the following five aspects: 1. The common CFD simulation methods used in the study of dynamic characteristics of concentric ring seals are introduced. The shortcomings of traditional quasi-steady state CFD methods are analyzed, and the improved methods are proposed. Based on interpolation theory, ring seals are developed. Based on the dynamic mesh model of flow field, a transient CFD method for the dynamic study of annular seal is presented. Based on the experimental device, the fluid force of the impeller orifice ring of the pump is tested, and the accuracy and accuracy of the proposed calculation method are verified. Similar to eccentric disturbance, a method for identifying the dynamic characteristic coefficients of concentric seals under inclined disturbance is presented. Considering the high time-consuming nature of the fully transient CFD simulation method, a fast solution model based on the idea of variable-speed eddy motion is proposed to calculate the fluid flow. All (eccentric and inclined) dynamic characteristic coefficients of body seals. The feasibility of the proposed transient method was evaluated by experimental comparison. In order to highlight the effect of inclined rotor excitation, the sealing fluid force under combined (eccentric and inclined) swirl of the rotor and the effect of the length-diameter ratio of the seal on the dynamic characteristic coefficients of the two types (eccentric and inclined) were studied. 3. An annular seal model including a complete upstream basin is established to study the effect of non-uniform inflow on the dynamic characteristics of the seal. Based on transient CFD simulation, the stiffness coefficient and the fluid exciting force of the annular seal under non-uniform inflow are studied. 4. Based on the transient CFD simulation method, the dynamic characteristic coefficients and leakage of the ring seal under different eccentricities are calculated and verified by experiments. The influence of rotor disturbance on the dynamic characteristic coefficients of the eccentric seal is discussed to study the application range of the linear hypothesis. Based on Muszynska's nonlinear model and CFD simulation, a nonlinear sealing force model is fitted. By means of nonlinear model and transient CFD simulation, the fluid excitation of the ring seal under various large disturbances is calculated, and then the dynamic characteristics of the seal under large eccentricity and large disturbance are discussed. 5. In order to better consider the non-linearity of the ring seal. The results show that the dynamic mesh model and transient calculation method developed in this paper have good computational performance. The accuracy and reliability of traditional quasi-steady-state CFD simulation method, improved quasi-steady-state CFD simulation method and transient CFD simulation method increase in turn. The results also show that the quasi-steady-state assumption leads to a serious underestimation of the main mass coefficient of the seal, while the transient C. The proposed transient simulation method based on variable speed eddy motion can be used to study the dynamics of complex liquid seals while maintaining the original accuracy and reducing the computational time consuming. With the increase of the length-diameter ratio of the seals, the difference between the dynamic characteristics coefficients of the two types (eccentric and inclined) tends to decrease, especially. It is the principal stiffness factor. Therefore, the fluid excitation caused by rotor tilt disturbance should not be neglected for large aspect ratio annular clearance seals. In addition to inlet pre-rotation and inlet loss, the uniformity of inlet flow also has a great influence on the sealing stiffness. In addition, the clearance dynamics is also related to the motion of the rotor, which may lead to poor reliability of the nonlinear sealing force model under large eccentricity. In this case, the establishment of fluid-solid coupling analysis method including the sealing flow field and rotor structure field will be a good solution. The conclusions provide the basis and support for the theoretical study and engineering analysis of the dynamic characteristics of liquid annular clearance seal and rotor/seal system.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TH136
本文編號：2187189
[Abstract]:Annular seal is the key structure in centrifugal pump, which is mainly used to restrain internal leakage and balance axial thrust of impeller, such as impeller orifice ring, stage seal, labyrinth seal, balance disk annular clearance, etc. These annular flow passages generally have small clearance and large pressure difference between the two ends. Dynamic excitation affects the vibration characteristics and operation stability of shafting. The dynamics of annular seal clearance has been greatly developed in the last century, and its analysis method has been gradually developed from short seal theory and finite length seal theory to three-dimensional CFD method. However, the nonlinear dynamic characteristics of the ring seal under the condition of rotor tilt disturbance, upstream incoming flow nonuniformity, large eccentricity and large disturbance have not been fully studied. The study and solution of these key problems will undoubtedly enrich the dynamic theoretical system of the ring seal of hydraulic machinery and promote the theoretical study and engineering analysis of the flow-induced vibration characteristics of the rotor system. The dynamic mesh model and the transient CFD simulation method of gap flow simulation and dynamic analysis were used to study the nonlinear dynamic problems of gap seal under the conditions of large eccentricity, large disturbance and rotor tilt disturbance. The main contents of this paper include the following five aspects: 1. The common CFD simulation methods used in the study of dynamic characteristics of concentric ring seals are introduced. The shortcomings of traditional quasi-steady state CFD methods are analyzed, and the improved methods are proposed. Based on interpolation theory, ring seals are developed. Based on the dynamic mesh model of flow field, a transient CFD method for the dynamic study of annular seal is presented. Based on the experimental device, the fluid force of the impeller orifice ring of the pump is tested, and the accuracy and accuracy of the proposed calculation method are verified. Similar to eccentric disturbance, a method for identifying the dynamic characteristic coefficients of concentric seals under inclined disturbance is presented. Considering the high time-consuming nature of the fully transient CFD simulation method, a fast solution model based on the idea of variable-speed eddy motion is proposed to calculate the fluid flow. All (eccentric and inclined) dynamic characteristic coefficients of body seals. The feasibility of the proposed transient method was evaluated by experimental comparison. In order to highlight the effect of inclined rotor excitation, the sealing fluid force under combined (eccentric and inclined) swirl of the rotor and the effect of the length-diameter ratio of the seal on the dynamic characteristic coefficients of the two types (eccentric and inclined) were studied. 3. An annular seal model including a complete upstream basin is established to study the effect of non-uniform inflow on the dynamic characteristics of the seal. Based on transient CFD simulation, the stiffness coefficient and the fluid exciting force of the annular seal under non-uniform inflow are studied. 4. Based on the transient CFD simulation method, the dynamic characteristic coefficients and leakage of the ring seal under different eccentricities are calculated and verified by experiments. The influence of rotor disturbance on the dynamic characteristic coefficients of the eccentric seal is discussed to study the application range of the linear hypothesis. Based on Muszynska's nonlinear model and CFD simulation, a nonlinear sealing force model is fitted. By means of nonlinear model and transient CFD simulation, the fluid excitation of the ring seal under various large disturbances is calculated, and then the dynamic characteristics of the seal under large eccentricity and large disturbance are discussed. 5. In order to better consider the non-linearity of the ring seal. The results show that the dynamic mesh model and transient calculation method developed in this paper have good computational performance. The accuracy and reliability of traditional quasi-steady-state CFD simulation method, improved quasi-steady-state CFD simulation method and transient CFD simulation method increase in turn. The results also show that the quasi-steady-state assumption leads to a serious underestimation of the main mass coefficient of the seal, while the transient C. The proposed transient simulation method based on variable speed eddy motion can be used to study the dynamics of complex liquid seals while maintaining the original accuracy and reducing the computational time consuming. With the increase of the length-diameter ratio of the seals, the difference between the dynamic characteristics coefficients of the two types (eccentric and inclined) tends to decrease, especially. It is the principal stiffness factor. Therefore, the fluid excitation caused by rotor tilt disturbance should not be neglected for large aspect ratio annular clearance seals. In addition to inlet pre-rotation and inlet loss, the uniformity of inlet flow also has a great influence on the sealing stiffness. In addition, the clearance dynamics is also related to the motion of the rotor, which may lead to poor reliability of the nonlinear sealing force model under large eccentricity. In this case, the establishment of fluid-solid coupling analysis method including the sealing flow field and rotor structure field will be a good solution. The conclusions provide the basis and support for the theoretical study and engineering analysis of the dynamic characteristics of liquid annular clearance seal and rotor/seal system.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TH136
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相關(guān)期刊論文 前2條
1 黃文虎,武新華,焦映厚,夏松波,陳照波;非線性轉(zhuǎn)子動力學(xué)研究綜述[J];振動工程學(xué)報;2000年04期
2 邢景棠,周盛,崔爾杰;流固耦合力學(xué)概述[J];力學(xué)進展;1997年01期
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