發(fā)布時間：2018-12-25 20:27

【摘要】：秸稈揉碎機是我國自行研制的一種介于切草機與粉碎機之間的新型飼草加工設(shè)備,主要由揉碎裝置和葉片式拋送裝置兩部分組成,秸稈經(jīng)揉碎裝置揉碎后由拋送裝置拋出機外。葉片式拋送裝置拋送物料的過程中,拋送葉輪需要承受高速旋轉(zhuǎn)產(chǎn)生的機械離心力、葉輪重力以及高速氣固兩相流產(chǎn)生的壓力等,而且伴隨著振動和沖擊,因此拋送葉輪的靜態(tài)和動態(tài)性能直接影響整個葉片式拋送裝置的工作性能。為了保證拋送裝置安全、可靠、穩(wěn)定地運行,本文在對9R-40型秸稈揉碎機葉片式拋送裝置內(nèi)氣固兩相流流場模擬計算基礎(chǔ)上,以拋送葉輪為研究對象,采用單向流固耦合的方法對其進行有限元分析,得到拋送葉輪在空氣與物料兩相流壓力、離心力及重力等載荷綜合作用下的應(yīng)力分布和應(yīng)變情況;基于有限元模型進行拋送葉輪自由模態(tài)仿真,采用激光測振技術(shù)測得拋送葉輪自由模態(tài)頻率及振型,驗證仿真結(jié)果的可靠性;在有限元模態(tài)分析可信的基礎(chǔ)上,進一步分析拋送葉輪的預(yù)應(yīng)力模態(tài)及工況共振情況;對比分析不同葉輪結(jié)構(gòu)參數(shù)對其應(yīng)力、應(yīng)變及振動模態(tài)的影響,以拋送葉輪結(jié)構(gòu)參數(shù)(葉片厚度、架板半徑及架板厚度)為設(shè)計變量對其進行動態(tài)優(yōu)化。研究結(jié)果表明:(1)拋送揉碎后的玉米秸稈時葉輪最大等效應(yīng)力為48.98MPa,出現(xiàn)在葉片與加強板和圓形架板外邊緣連接處,應(yīng)變與應(yīng)力的變化趨勢相同;葉輪最大變形量為0.046mm,出現(xiàn)在葉片外邊緣,葉片整體存在向外擴張并沿切向彎曲的趨勢。經(jīng)過校核,葉輪強度和剛度滿足要求。(2)葉片厚度對葉輪的最大應(yīng)力、應(yīng)變及總變形影響較小;葉片長度增大,葉輪最大等效應(yīng)力、應(yīng)變隨之減小;葉輪轉(zhuǎn)速增加,最大等效應(yīng)力、應(yīng)變及變形量隨之增大;加強筋結(jié)構(gòu)能夠減小葉輪的等效應(yīng)力、應(yīng)變及總變形;葉輪應(yīng)力及應(yīng)變分布規(guī)律不隨葉片長度、葉片厚度、工況轉(zhuǎn)速及有無加強筋而改變。(3)試驗?zāi)B(tài)與計算自由模態(tài)頻率最大相對誤差為3.99%,各階振型基本相同,最大振幅的位置基本一致,試驗證明有限元模擬結(jié)果可信。(4)預(yù)應(yīng)力使各階模態(tài)頻率有所提高,其中第1階和第2階頻率增大較明顯。(5)共振分析顯示拋送揉碎后的玉米秸稈時,葉輪第1階預(yù)應(yīng)力模態(tài)頻率與激振基頻避開率滿足要求,但第2階和第3階頻率分別與激振頻率2倍頻和3倍頻接近。為了改善葉輪的動態(tài)特性,需對其進行優(yōu)化。(6)架板厚度對預(yù)應(yīng)力模態(tài)低階頻率影響最大,葉片厚度次之,架板半徑影響較小;拋送葉輪優(yōu)化后一階頻率避開率由21.98%提高到35.82%,二階頻率避開率由8.76%提高到11.11%,三階頻率避開率由4.27%提高到7.55%,葉輪總質(zhì)量減小了0.31Kg。優(yōu)化后葉輪強度和剛度均能夠滿足工況要求,優(yōu)化結(jié)果可行。
[Abstract]:Straw crusher is a kind of new forage processing equipment which is developed by our country. It is mainly composed of two parts: crusher and blade throwing device. The straw is crumpled by crusher and then thrown out by throwing device. In the process of throwing material by vane throwing device, the throwing impeller needs to bear the mechanical centrifugal force produced by high speed rotation, the gravity of impeller and the pressure produced by high speed gas-solid two-phase flow, and it is accompanied by vibration and shock. Therefore, the static and dynamic performance of the throwing impeller directly affects the performance of the whole blade throwing device. In order to ensure the safe, reliable and stable operation of the throwing device, based on the simulation calculation of the gas-solid two-phase flow field in the vane throwing device of 9R-40 type straw crusher, this paper takes the throwing impeller as the research object. The stress distribution and strain of the throwing impeller under the combined loads of air and material two-phase flow pressure, centrifugal force and gravity are obtained by using the unidirectional fluid-solid coupling method. Based on the finite element model, the free modal frequency and mode shape of the throwing impeller are measured by laser vibration measurement technology, and the reliability of the simulation results is verified. On the basis of the credible finite element modal analysis, the prestressing mode and resonance of the throwing impeller are further analyzed. The influence of different impeller structural parameters on stress, strain and vibration mode is analyzed, and the structural parameters of throwing impeller (blade thickness, plate radius and plate thickness) are dynamically optimized. The results showed that: (1) the maximum equivalent stress of the impeller was 48.98 MPA when the corn straw was thrown and crumpled, which appeared at the junction of the blade with the outside edge of the stiffener and the circular frame, and the variation trend of strain and stress was the same; The maximum deformation of the impeller is 0.046 mm, which appears on the outer edge of the blade, and the whole blade expands outward and bends along the tangential direction. After checking, the strength and stiffness of the impeller meet the requirements. (2) the thickness of the blade has little effect on the maximum stress, strain and total deformation of the impeller, and the maximum equivalent stress of the impeller decreases with the increase of blade length. The maximum equivalent stress, strain and deformation increase with the increase of impeller speed, and the equivalent stress, strain and total deformation of impeller can be reduced by strengthening the steel bar structure. The distribution of stress and strain of impeller does not change with blade length, blade thickness, operating speed and reinforcement. (3) the maximum relative error between test mode and free mode frequency is 3.99, and all modes are basically the same. The position of the maximum amplitude is basically the same. The experimental results show that the finite element simulation results are reliable. (4) Prestress increases the frequency of each order modal. The first and second order frequencies increase obviously. (5) Resonance analysis shows that the first order prestressing mode frequency and the exciting fundamental frequency escape rate of the impeller meet the requirements when the corn straw is thrown and crushed. However, the second and third order frequencies are close to the excitation frequencies of 2 and 3 times respectively. In order to improve the dynamic characteristics of impeller, it is necessary to optimize it. (6) the thickness of frame plate has the greatest influence on the low-order frequency of prestressing mode, the thickness of blade is the second, and the radius of frame plate is less; After the optimization of the throwing impeller, the first order frequency avoiding rate was increased from 21.98% to 35.82%, the second order frequency avoiding rate increased from 8.76% to 11.11, the third order frequency avoiding rate increased from 4.27% to 7.55%. The total mass of impeller decreased by 0.31 kg. After optimization, the strength and stiffness of impeller can meet the requirements of working conditions, and the optimized results are feasible.
【學位授予單位】：內(nèi)蒙古工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：S817.12

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本文編號：2391603