本文選題：軸流葉輪 + 流固耦合�。� 參考：《華北電力大學》2014年碩士論文

【摘要】：風機在國民經濟的諸多領域都有十分廣泛的應用，隨著電站機組容量的不斷增加，大機組采用多級動葉可調軸流式風機已經成為發(fā)展趨勢。作為風機的核心部件，葉輪的強度不足會對風機運行產生一定的安全隱患，有可能引發(fā)疲勞破壞。在傳統(tǒng)的風機強度計算中，對葉輪尤其是葉片的結構進行了大量的簡化，導致較大的計算誤差，不利于葉輪安全性的準確預估，采用有限元法能夠很好地彌補這一不足。 本文采用數(shù)值模擬技術，結合流固耦合分析方法，對電站兩級動葉可調軸流風機葉輪進行了靜態(tài)特性分析。分析結果表明，氣動力對葉輪的靜態(tài)特性有較大影響，考慮流固耦合作用后，氣動力與離心力對葉輪的作用效果在一定程度上相互抵消，葉片表面等效應力分布情況發(fā)生變化，等效應力最大值減小，并且葉片變形趨勢有較為顯著的改變。對葉輪運行的安全性進行了預估，葉輪峰值等效應力遠小于葉輪材料的許用應力90MPa，故該軸流風機的靜強度符合要求。 本文對軸流葉輪的動力特性進行了分析，分別計算了葉片、輪盤及葉輪的模態(tài)。施加預應力后葉片固有頻率有一定程度的增長，其中離心力對振動頻率的影響最大，并且轉速越快，振動頻率越大。對單扇區(qū)葉輪模型進行模態(tài)計算，得到了葉輪不同節(jié)徑下的各階振動頻率，著重對葉輪1節(jié)徑各階模態(tài)進行了詳細分析，第五階與第六階振動頻率與監(jiān)測得到的氣動力主頻率之間的頻率余量約為9.4%，，小于頻率余量的工程安全裕度，即氣流激振力的主頻率落入第五階與第六階模態(tài)的局部共振區(qū)域。葉輪共振的表現(xiàn)形式為葉片的局部振動，考慮到葉頂位置的等效應力值很小，遠小于葉片材料的屈服極限，因此葉輪該區(qū)域不會發(fā)生疲勞破壞。
[Abstract]:Fan has been widely used in many fields of national economy. With the increasing capacity of power plant units, it has become a development trend for large units to adopt multi-stage movable vane adjustable axial flow fan. As the core component of fan, the strength of impeller will cause some safety hidden trouble to fan operation, which may lead to fatigue damage. In the traditional calculation of fan strength, the structure of impeller, especially blade, is simplified, which leads to a large calculation error, which is unfavorable to the accurate prediction of impeller safety. The finite element method can make up for this deficiency. In this paper, the static characteristics of two stage adjustable axial fan impeller of power station are analyzed by using numerical simulation technique and fluid-solid coupling analysis method. The results show that aerodynamic force has great influence on the static characteristics of impeller. Considering the fluid-solid coupling, the effect of aerodynamic force and centrifugal force on impeller is offset to a certain extent, and the distribution of equivalent stress on the blade surface changes. The maximum equivalent stress decreases and the deformation trend of the blade changes significantly. The safety of impeller operation is estimated. The equal effect force of impeller peak value is much less than the allowable stress of impeller material at 90 MPa, so the static strength of the axial fan meets the requirement. In this paper, the dynamic characteristics of axial impeller are analyzed, and the modes of blade, disk and impeller are calculated. The natural frequency of the blade increases to a certain extent after prestressing. The centrifugal force has the greatest influence on the vibration frequency, and the faster the speed is, the greater the vibration frequency is. The modal calculation of the single sector impeller model is carried out, and the vibration frequencies of the impeller with different nodal diameters are obtained, and the modes of the first pitch diameter of the impeller are analyzed in detail. The frequency margin between the fifth and sixth order vibration frequency and the monitored aerodynamic main frequency is about 9.4, which is less than the engineering safety margin of the frequency margin, that is, the main frequency of the airflow excitation force falls into the local resonance region of the fifth and sixth modes. The form of the impeller resonance is the local vibration of the blade. Considering that the equal effect force at the top of the blade is very small and is far less than the yield limit of the blade material, the impeller will not have fatigue failure in this region.
【學位授予單位】：華北電力大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM62

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