基于流固耦合的秸秆抛送叶轮有限元分析及动态特性优化
发布时间：2018-12-25 20:27
【摘要】：秸秆揉碎机是我国自行研制的一种介于切草机与粉碎机之间的新型饲草加工设备,主要由揉碎装置和叶片式抛送装置两部分组成,秸秆经揉碎装置揉碎后由抛送装置抛出机外。叶片式抛送装置抛送物料的过程中,抛送叶轮需要承受高速旋转产生的机械离心力、叶轮重力以及高速气固两相流产生的压力等,而且伴随着振动和冲击,因此抛送叶轮的静态和动态性能直接影响整个叶片式抛送装置的工作性能。为了保证抛送装置安全、可靠、稳定地运行,本文在对9R-40型秸秆揉碎机叶片式抛送装置内气固两相流流场模拟计算基础上,以抛送叶轮为研究对象,采用单向流固耦合的方法对其进行有限元分析,得到抛送叶轮在空气与物料两相流压力、离心力及重力等载荷综合作用下的应力分布和应变情况;基于有限元模型进行抛送叶轮自由模态仿真,采用激光测振技术测得抛送叶轮自由模态频率及振型,验证仿真结果的可靠性;在有限元模态分析可信的基础上,进一步分析抛送叶轮的预应力模态及工况共振情况;对比分析不同叶轮结构参数对其应力、应变及振动模态的影响,以抛送叶轮结构参数(叶片厚度、架板半径及架板厚度)为设计变量对其进行动态优化。研究结果表明:(1)抛送揉碎后的玉米秸秆时叶轮最大等效应力为48.98MPa,出现在叶片与加强板和圆形架板外边缘连接处,应变与应力的变化趋势相同;叶轮最大变形量为0.046mm,出现在叶片外边缘,叶片整体存在向外扩张并沿切向弯曲的趋势。经过校核,叶轮强度和刚度满足要求。(2)叶片厚度对叶轮的最大应力、应变及总变形影响较小;叶片长度增大,叶轮最大等效应力、应变随之减小;叶轮转速增加,最大等效应力、应变及变形量随之增大;加强筋结构能够减小叶轮的等效应力、应变及总变形;叶轮应力及应变分布规律不随叶片长度、叶片厚度、工况转速及有无加强筋而改变。(3)试验模态与计算自由模态频率最大相对误差为3.99%,各阶振型基本相同,最大振幅的位置基本一致,试验证明有限元模拟结果可信。(4)预应力使各阶模态频率有所提高,其中第1阶和第2阶频率增大较明显。(5)共振分析显示抛送揉碎后的玉米秸秆时,叶轮第1阶预应力模态频率与激振基频避开率满足要求,但第2阶和第3阶频率分别与激振频率2倍频和3倍频接近。为了改善叶轮的动态特性,需对其进行优化。(6)架板厚度对预应力模态低阶频率影响最大,叶片厚度次之,架板半径影响较小;抛送叶轮优化后一阶频率避开率由21.98%提高到35.82%,二阶频率避开率由8.76%提高到11.11%,三阶频率避开率由4.27%提高到7.55%,叶轮总质量减小了0.31Kg。优化后叶轮强度和刚度均能够满足工况要求,优化结果可行。
[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.
【学位授予单位】：内蒙古工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S817.12
本文编号：2391603
[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.
【学位授予单位】：内蒙古工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S817.12
【参考文献】
相关期刊论文 前2条
1 贾洪雷,王增辉,马成林,陈忠亮;玉米秸秆切碎抛送装置的试验研究[J];农业机械学报;2003年06期
2 贾洪雷,马成林;曲面直刃刀切碎与抛送变量的研究[J];农业机械学报;2002年06期
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