螺杆空压机转子受力有限元计算研究

螺杆压缩机转子受力的准确计算是保障压缩机可靠性的基本条件。本文利用有限元方法对螺杆空压机阴阳转子所受气体力进行了分析计算,提出了实现转子受力计算的有效、快速的方法及实施方案。同时对转子所受轴向力进行了试验测试,验证了该方法的准确性。     

螺杆压缩机转子受力计算

螺杆转子旋转时，基元容积的密封线，只用轴向平移，而不改变其形状。因此可利用这一特性，将密封线投影到相关平面来进行转子受力分析。用微元齿间容积的轴向、径向、切向气体分力．沿整个转子长度方向积分，即可得到作用在转子上的力，同时解出轴承支反力。     

轴向车铣薄壁回转体的动力学分析

根据弹性体动力学理论,建立轴向车铣加工薄壁回转体的动力学模型,得到了各阶固有频率和主振型的计算公式,分析了在简谐激励下薄壁回转体强迫振动的动力学响应。利用ANSYS对ZL101薄壁回转体的轴向车铣加工进行了模态分析和谐响应分析,得到了振动峰值的频率和幅值,且与理论计算的结果一致。研究结果表明,在薄壁回转体的轴向车铣加工中,合理选择铣刀转速和齿数,可使切削力频率避开共振区间,有利于得到更好的表面质量。     

制粒过程中环模力学模型的建立及有限元分析

环模制粒机广泛地应用于饲料工业、新能源技术和制药等领域,而环模和压辊是其关键部件。建立了环模挤压力学模型,并在此基础上应用ANSYS软件对环模进行了有限元力学分析,获得了沿环模轴向和周向的应力和位移数据。分析结果表明:环模沿轴向受到的是非均匀载荷,疲劳断裂是环模的一种失效形式。为改善环模的受力状况、降低环模磨损提供了一定的参考。     

Study on precision grinding of screw rotors using CBN wheel

With increasing demands for high-speed and high-precision machining technology, CBN shape grinding is an effective means in the field of precision machining for screw rotors. Aiming at the high precision machining of screw rotors, a mathematical model for the axial profiles of the CBN wheel for machining screw rotors is developed based on theory of gear engagement. Small electroplated CBN wheel is firstly used to grinding screw rotors. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of CBN wheel. For reducing the tooth profile errors of screw rotors induced by mounting errors and wears of CBN wheel, a mathematical model of the error analyses is established and the influence curves of the profile errors affected by mounting errors and radius error of grinding wheel are proposed. The electroplated CBN wheels for the screw rotors are made to verify the validity and effectiveness of the presented method and the machining experiments were performed. Results of this study reveals that the method proposed in this paper can be used as the precision grinding of screw rotors.     

两段预紧的端齿连接转子轴向预紧力的确定

现代涡桨,轴发动机多采用前、后两段分别轴向预紧的端齿连接转子,确定其预紧力的大小是一个极为重要而又非常困难的问题,在已知转子工作时各种载荷引起的轴向松弛力和压紧力的前提下,本文作者曾提出过一个综合考虑紧度裕度,强度裕度、装配关系等多因素的轴向预紧力确定准则。     

基于简化基本折叠单元法的蜂窝耐撞性优化设计

采用简化基本折叠单元法,即基于简化基本折叠单元的超折叠单元理论对三种常用蜂窝结构的轴向平均压缩应力进行理论求解。为验证理论解的准确性,采用基于LS-DYNA的非线性有限单元法对这三种常用蜂窝结构的轴向压缩进行仿真计算,仿真结果与理论结果吻合很好。基于轴向平均压缩应力理论解,进一步采用多目标粒子群算法分别对这三种预压缩常用蜂窝结构的耐撞性进行多目标优化,发现在所研究的三种常用蜂窝结构中,正六边形蜂窝结构的耐撞性最好。采用LS-DYNA对优化设计的蜂窝结构进行轴向压缩仿真,仿真结果与基于所给出理论公式的耐撞性优化结果相差不大,说明基于所给出理论公式的蜂窝结构耐撞性优化是可行且有效的。     

On the orientation of a gyrostat using internal rotors

A control scheme is proposed to guarantee three axial orientations of a gyrostat. The gyrostat is controlled by the action generated by rotating internal rotors. The control problem is concerned with the exponential stability of equilibrium positions of the gyrostat using servo-control moments which are applied to the internal rotors. The non-linear control law is obtained from the conditions that ensure the exponential stability of the desired position. The general solution of the equations of the perturbed motion is obtained as a function of time.     

高速客车轴箱轴承的偏载分析及轴承滚子非对称修形

通过对铁路高速客车轴箱轴承在偏载下滚动体与内外圈的接触应力和位移等所进行的有效元分析，提出了滚子非对称修形新概念。有限元分析结果表明，由于轴向载荷的影响，滚动体与内外圈的接触应力和位移等沿滚动体轴线的分布发生偏移，传统的对称修形虽然可以避免滚动体两端的边界应力集中，但无法克服“偏载效应”。为了同时避免所谓的“边缘效应”和克服“偏载效应”，必须根据偏载下滚动体与内外圈的接触应力或位移的偏移分布规律对滚子进行相应的非对称母线修形，从而使非对称修形滚子轴承有更高的可靠性和使用寿命。     

无油螺杆空气压缩机转子变形分析

利用ANSYS对一对中空的铝转子,在两种不同工况下进行热、力变形分析的研究。发现转子的力变形比热变形要小得多;虽然整个转子的温差不大,但是转子径向变形沿长度方向依然存在差别;对阴、阳转子沿接触线径向变形的分析发现,总变形量和温度基本呈线性变化趋势。     

轴向间隙对对旋风机气动特性及总性能的影响

以一台矿用对旋风机为对象,采用CFD方法对6种不同轴向间隙方案下风机的气动性能进行了三维非定常数值计算,对不同轴向结构对风机压力脉动特性、性能和流场的影响进行分析研究。研究表明:对旋风机的非定常性受轴向间隙的影响较大,增加间距不仅能较好地削弱下游转子的位势干扰作用,同时也能降低上游转子的叶片尾迹影响;轴向间隙对风机效率、静压升以及两级效率、轴功率均有显著影响;增大轴向间隙会加剧掺混损失对风机性能的影响。     

扭曲管换热器管板的有限元分析

采用有限元分析软件ANSYS,对扭曲管换热器的管板在三种工况下的应力进行计算,分析了扭曲管轴向刚度削弱系数对管板应力强度及扭曲管轴向应力的影响。结果表明,扭曲管的轴向变形补偿能力优于普通直管,可以降低在温差载荷作用下管板中的应力,但会提高压力作用下的管板应力。在压力载荷作用下,扭曲管上的平均应力大小与普通直管差别不大,但扭曲管的轴向应力在管子横截面上的分布不均匀,局部的轴向应力远远高于平均应力水平,因此扭曲管抗疲劳和应力腐蚀开裂的能力不如直管。不同厚度的管板受扭曲管管束轴向刚度的影响不同,当管板厚度较小时,扭曲管管束轴向刚度的影响较大。     

掠动叶对小型轴流风扇转子气动及声学特性的影响研究

通过前掠、后掠以及径向小型轴流风扇转子流场的数值分析，研究了掠动叶对转子气动及声学特性的影响及其作用机理，并给出了由转子尾缘旋涡脱落而诱发的紊流噪声压值分布，该分布说明了前掠动叶提高了转子的声学特性。     

电磁型平面微电机及其制作工艺

为得到一种尺寸小、输出力矩大、转速高的直流可调速微电机,提出了一种利用微机械加工工艺制作微电机的方法。定子和转子都做成平面结构,定子线圈采用了平面型、无槽式集中绕组;线圈之间采用了三相星形连接方式,采用了微机械LIGA工艺和硅微机械加工工艺;转子采用钕铁硼永磁材料,进行轴向充磁,成辐射状间隔分布。装配时转子分布于定子两侧,不但减小了电机尺寸,还有利于定子的散热。把装配完毕的微电机接通三相半控控制电路对其转速和力矩进行了测试,测试结果表明,电机运转平稳,输出力矩大。     

径向受载型金属垫片法兰密封结构的力学特性研究

介绍了一种径向受载型金属垫片法兰密封结构,分析了其受力特点和密封机理。利用有限元分析方法对它的力学特性进行了研究,计算了不同的法兰锥形张角在不同轴向压缩量下的轴向力、径向力以及密封面上的最大von Mises应力,分析了其规律及对密封结构装配特性、密封特性的影响。与普通轴向受载型金属垫片法兰密封结构相比,其所需的紧固载荷较小,用较轻的法兰及较小的螺栓载荷即能实现密封作用,尤其适用于装配空间小、装配时间要求短、有辐射、需远距离操作等场合。     

薄壁机匣结构复杂冲击载荷与等效试验方法研究

航空发动机机匣属于典型薄壁框架结构，针对断轴后其承受的由涡轮转子的轴向冲击与周向扭转冲击构成的复杂冲击载荷，建立了包含涡轮转子与排气机匣等关键部件的数值仿真模型，以仿真结果中排气机匣的复杂冲击载荷与能量耗散为切入点，获得了复杂冲击过程中二者的动态响应；指出在涡轮转子的高速旋转与轴向移动复合运动因素中，初始转速对冲击载荷与能量耗散无明显影响；进一步转换涡轮转子与排气机匣的相对运动关系，分析结果表明，转换后的冲击载荷和能量耗散结果与转换前保持高度相似。在后续的等效试验方法中，这些研究结论可成为简化试验台结构设计的参考。     

COMPUTATIONAL AND EXPERI- MENTAL STUDY ON TIP LEAKAGE VORTEX OF CIRCUMFERENTIAL SKEWED BLADES

In the steady operation condition,the experiments and the numerical simulations are used to investigate the tip leakage flow fields in three low pressure axial flow fans with three kinds of circumferential skewed rotors,including the radial rotor,the forward-skewed rotor and the back-ward-skewed rotor. The three-dimensional viscous flow fields of the fans are computed. In the ex-periments,the two-dimensional plane particle image velocimetry (PIV) system is used to measure the flow fields in the tip region of three different pitchwise positions of each fan. The results show that the computational results agree well with the experimental data in the flow field of the tip region of each fan. The tip leakage vortex core segments based on method of the eigenmode analysis can dis-play clearly some characteristics of the tip leakage vortex,such as the origination position of tip leak-age vortex,the development of vortex strength,and so on. Compared with the radial rotor,the other two skewed rotors can increase the stability of the tip leakage vortex and the increment in the for-ward-skewed rotor is more than that in the backward-skewed one. Among the tip leakage vortices of the three rotors,the velocity of the vortex in the forward-skewed rotor is the highest in the circumfer-ential direction and the lowest in the axial direction.     

Second Generation Wavelet Finite Element and Rotor Cracks Quantitative Identification Method

The presence of cracks in the rotor is one of the most dangerous and critical defects for rotating machinery. Defect of fatigue cracks may lead to long out-of-service periods, heavy damages of machines and severe economic consequences. With the method of finite element, vibration behavior of cracked rotors and crack detection was received considerable attention in the academic and engineering field. Various researchers studied the response of a cracked rotor and most of them are focused on the crack detection based on vibration behavior of cracked rotors. But it is often difficult to identify the crack parameters quantitatively. Second generation wavelets (SGW) finite element has good ability in modal analysis for singularity problems like a cracked rotor. Based on the fact that the feature of SGW could be designed depending on applications, a multiresolution finite element method is presented. The new model of SGW beam element is constructed. The first three natural frequencies of the rotor with different crack location and size were solved with SGW beam elements, and the database for crack diagnosis is obtained. The first three metrical natural frequencies are employed as inputs of the database and the intersection of the three frequencies contour lines predicted the normalized crack location and size. With the Bently RK4 rotor test rig, rotors with different crack location and size are tested and diagnosed. The experimental results denote the cracks quantitative identification method has higher identification precision. With SGW finite element method, a novel method is presented that has higher precision and faster computing speed to identify the crack location and size.     

A precision grinding method for screw rotors using CBN grinding wheel

Aiming at the high precision machining of screw rotors, a new grinding method for screw rotors using cubic boron nitride (CBN) grinding wheel is presented in this paper. Small electroplated CBN grinding wheel is firstly used to grind screw rotors. The mathematical model for the axial profiles of CBN grinding wheel is developed based on gear engagement theory. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of the CBN grinding wheel. Wire cut electrical discharge machining low speed (WEDM-LS) was used to machine the base body of the CBN grinding wheel. The formed turning tools of the base body of CBN grinding wheel using WEDM-LS and the wheel shapes of CBN grinding wheel using the formed turning tool were performed. The CBN grinding wheels for the screw rotors were made to verify the validity and effectiveness of the presented method. The electroplated CBN grinding wheels were used to machine the screw rotors, and the machining experiments were performed. The data obtained in the experiments reach the fifth class of Chinese Standard GB10095-88.     

Finite element analysis of rotorsAhaлмв кoлebhий potopob metoдoм кoнeыш элeмeнтoв

A finite element formulation for the natural vibration analysis of tapered and pretwisted rotors has been presented. Numerical results for natural frequencies for various values of the geometric parameters and rotational speeds, have been computed for the case of rotors with and without pretwist. A Galerkin solution for the fundamental has also been worked out and has been used to provide a comparison for the finite element results. Charts for rapid estimation of the fundamental frequency parameter of tapered rotors, have been included.