用反射式光电显微镜进行分离间隙精密测定

本文介绍了间隙测量的原理、试验装置、方法及结果,并对反射式光电显微镜进行分离间隙测定的方法进行了分析比较,认为不论从理论上还是在实验中,该方法用于一般光刻中的间隙测量是可行的。     

变间隙密封液压缸密封间隙测量技术研究

为了实现变间隙密封液压缸密封间隙量的测量,以活塞唇边简化为厚壁圆筒模型,以迦辽金位移函数为理论基础推导出活塞唇边的变形关系式,采用LabVIEW对液压缸密封间隙进行仿真实验,通过超声波测量来验证测量结果,实现对压力、密封间隙、活塞运动位移量的数据采集和数据处理。结果表明：仿真实验和超声波的测量结果的最大误差为7.94%,其密封间隙的测量方法是可行的。所设计的测量系统缩短了测试时间,为变间隙密封液压缸的性能测试提供了理论和实验的支撑。     

阻尼间隙可调式磁流变阀压降特性仿真分析及实验研究

针对目前磁流变阀结构中阻尼间隙固定不变导致阀口进、出口压力差调节方式单一的不足,提出了一种新型阻尼间隙可调式磁流变阀结构,可通过旋转阀芯改变与阀体之间的相对位置来改变阻尼间隙。采用ANSYS有限元电磁场仿真软件对所设计的阻尼间隙可调式磁流变阀进行电磁场仿真分析,加工出阻尼间隙可调式磁流变阀并进行了初步实验分析,相关仿真和实验结果有利于进一步拓宽磁流变阀的工业应用范围。     

关节间隙对机器人动态特性影响分析

为了分析关节间隙对机器人动态特性的影响,采用L-N非线性弹簧阻尼模型对关节间隙接触碰撞力进行建模,D-H方法建立装配机器人的运动学方程,Lagrange方法建立装配机器人动力学微分方程,推导出关节位移、速度、角加速度、力矩以及接触力的方程;提出采用IMPACT函数对碰撞进行描述,运用ADAMS软件建立含关节间隙机器人虚拟样机,分析不同驱动方式下关节间隙对机器人动态特性的影响;以自行设计的四自由度装配机器人为研究对象搭建实验平台对理论分析与仿真结果进行验证,实验验证了理论分析与仿真分析的合理性,得到了关节间隙对机器人动态特性影响曲线并提出了相应的改善措施。     

超声频间隙脉冲放电加工研究

作者提出了超声频间隙脉冲放电加工新技术，并对该技术进行了理论分析和加工实验。本刊将从本期起分四次刊出超声频间隙脉冲放电加工的基本原理、工作液选择、理论分析和实验研究。     

含间隙关节的双推杆机械臂运动特性研究

建立了间隙关节的数学模型和含间隙关节的双推杆机械臂运动学模型;利用仿真模拟分析了单间隙关节A、单间隙关节B、双间隙关节A和B三种不同间隙关节位置和数量对机械臂末端轨迹、速度和加速度的影响,并采用绝对误差作为评价指标对影响程度进行了定量分析;搭建实验台对仿真结果进行了实验验证。结果表明,间隙关节导致机械臂末端运动轨迹在X轴和Y轴方向产生误差,且双间隙关节A和B造成的轨迹误差近似为两个单间隙关节的轨迹误差之和;机械臂末端速度和加速度曲线因间隙的存在而产生脉冲波动,其中单间隙关节A和单间隙关节B对曲线的影响程度相当,双间隙关节A和B在耦合作用下对曲线的影响程度远大于单间隙关节的影响程度。     

电弧铣削加工间隙电压预测模型的建立与研究

针对电弧铣削加工过程中极间间隙难以直接测量的问题，通过极间间隙电压的变化判断极间间隙的变化，采用系统辨识理论确定间隙电压预测模型的结构和模型参数，对该预测模型的建立方法进行了详细阐述，对预测模型的拟合程度进行了实验验证。实验结果表明，预测模型的拟合精度随着拟合时间的延长而降低，因此，采用递推最小二乘方法进行间隙电压的在线预测，在线预测的平均误差为6.82%，结果表明所建模型能够稳定、有效地超前一步预测间隙电压，并且模型在线辨识的参数少，模型预测的精度高。     

叶片电化学加工过程多场耦合仿真

针对叶片电化学加工过程难以预测、实验参数修正周期长的问题,建立与温度相关的叶片多场耦合仿真模型,基于COMSOL Multiphysics平台对叶片电化学加工过程进行多场耦合仿真,仿真分析了不同加工电压和不同进液流量对法向平衡间隙的影响。结果表明：加工电压越大,间隙也相应增大,且间隙分布越不均匀;进液流量越大,间隙分布越均匀。采用其中一组仿真参数进行工艺实验,仿真与实验的对比结果表明,叶片轮廓曲率变化缓慢处的仿真结果和实验结果比较贴合,而轮廓曲率变化较快处的仿真值与实验值差别相对较大,但两者的变化趋势相同。     

移动刚体激励悬臂梁的间隙模型与实验研究

利用理论建模与实验研究相结合的方法研究移动质量与悬臂梁导轨之间的动态间隙.利用二状态非线性弹簧-阻尼碰撞模型表征间隙铰,运用模态分析理论建立了含间隙作用移动刚体激励悬臂梁的时变横向振动分布参数模型,进行了数值计算.梁的动态响应与实验吻合较好验证了理论分析的正确性,间隙的时域曲线变化趋势基本相同,实验参数下计算的间隙一阶频率和实验一致.所建模型基本描述了系统的动态特性,为研究含间隙的机械系统提供了参考.     

发动机气门间隙异常仿真分析研究

研究了柴油发动机气门间隙异常对配气机构动力学性能的影响。对配气机构进行了多质量动力学模型计算,建立了配气机构的多体动力学模型,设置3种不同的气门间隙进行分析。分析结果表明:气门间隙变大会造成气门速度、加速度增大以及气门连接部件的冲击力增大,会使发动机产生异响;气门间隙变大也会使配气机构之间的接触力增大,加速凸轮轴的点蚀磨损,气门发生故障的危险系数增加;相对而言,排气门发生故障的概率远大于进气门。所进行实验的验证结果与模拟分析结果相同,从而证明了仿真模型的有效性;经过实验验证发现:排气门间隙过小将会使气门与活塞头部碰撞,造成活塞头部损坏。     

空调用贯流风机气动噪声预测的研究

基于N-S方程和雷诺输运应力方程(RSM),对空调用贯流风机进行了非稳态内流计算,并应用基于Lighthill声学类比理论的FW-H方程时域解法,预测了由叶轮表面压力波动和蜗舌表面压力波动所产生的远场气动噪声,同时还比较了不同蜗舌间隙对气动噪声的影响.     

后置蜗壳斜流风机整机数值模拟

使用商业软件Numeca的Fine／Turbo模块，对包含斜流叶轮与蜗壳一体的斜流风机进行整机计算。对一斜流风机在设计转速下不同工况点进行了数值模拟，并与试验结果进行了比较，吻合较好。通过特定截面的不同流动图谱，证实了蜗壳、叶轮相互作用引起的整机流场的不对称性。研究结果表明，叶轮内部叶顶间隙区二次流动和叶轮与蜗壳相互作用引起的涡系是影响斜流风机效率的主要原因。     

离心压缩机机壳在基频气动力激励下的振动噪声研究

研究了离心压缩机机壳在内部基频气动力激励下的振动辐射噪声。考虑机壳与轮盘、轮盖之间的间隙,采用SSTk-co湍流模型模拟了离心压缩机的整机三维非定常流场,得到蜗壳内表面的脉动压力,然后将脉动压力的基频部分加载到蜗壳上,模拟离心压缩机蜗壳在非定常气动力激励下的振动噪声。研究表明：机壳内壁面基频压力脉动主要分布在无叶扩压器靠近叶轮出口一侧;机壳主要基频振动噪声源位于蜗壳靠近出口管道一侧;该离心压缩机机壳基频振动位移幅值很小,最大振动位移仅为11．8×10^-9m,因此可以忽略机壳的基频振动对离心压缩机运行安全性的影响。     

Investigation on Reduction of Pressure Fluctuation for a Double-Suction Centrifugal Pump

Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap)are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6% of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps.     

低比转数高效率蜗壳泵的开发

为了开发出一种高效率低比转数 (ns<70 )的蜗壳泵 ,总结了比转数ns=60时的两种试验结果 ,进行了叶轮设计和蜗壳设计的优化 ,并进行了新的试验 ,以揭示叶轮与蜗舌之间的流动干扰。结果表明 ,低比转数蜗壳泵不宜采用常规设计 ,进而提出了一种新的设计方法。     

径向吸气室对离心压缩机级性能的影响

采用CFD手段对某离心压缩机级性能在轴向和径向两种不同的进气方式下进行了数值模拟,得出了在这两种进气方式下离心压缩机在3种机器马赫数下的级性能。分析了由于径向吸气室引起的叶轮进口流动参数周向分布不均匀而引起的级性能恶化以及叶轮对吸气室内流动的影响,得出了3点结论。     

多孔材料蜗舌对贯流风机的气动声学性能影响

在不改变蜗舌的几何外形与尺寸的情况下,使用4种不同的多孔材料制作蜗舌,得出某贯流风机蜗舌的4种替换方案.通过对其气动和声学性能的实验测试,比较了多孔材料制作的蜗舌对贯流风机的气动性能和噪声特性的影响.     

离心压缩机蜗壳内部流动的研究

对不同工况整机条件下的离心压缩机蜗壳内流场进行了详细的数值研究,分析了变工况下蜗壳内流动情况以及蜗壳对扩压器内流动的影响,并得出了4点结论。     

Influence of Cross-Sectional Flow Area of Annular Volute Casing on Transient Characteristics of Ceramic Centrifugal Pump

The annular volute is typically used in a slurry pump to reduce the collisions between solid particles and the volute tongue and to achieve a better resistance to blocking. However, only limited studies regarding annular volutes are available, and there is no systematic design method for annular volutes. In this study, the influence of volute casing cross-sectional flow area on the hydraulic loss, pressure pulsations, and radial force under varying working conditions in a centrifugal ceramic pump are discussed in detail. Experimental tests were conducted to validate the numerical results. The results indicated that, when the volute casing flow area increases, the hydraulic performance decreases marginally under the rated working conditions, but increases at the o-design points, specifically under large flow condition. However, the volute casing with a larger flow area has a wider high-e ciency region. In addition, the increase in the volute casing flow area will decrease the pressure pulsations in the volute, regardless of the working condition, and decrease the radial force on the shaft, therefore, providing an improved pump operational stability. It is anticipated that this study will be of benefit during the design of annular volutes.     

CFD investigation of the influence of volute geometrical variations on hydrodynamic characteristics of circulator pump

Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump’s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics(CFD) technology is presented. Five main volute geometrical parametersD3,A8,a0,j0 andRt are selected and 25 different volute configurations are generated by using design of experiments(DOE) method. The 3D unsteady flow numerical simulations, which are based on the SSTk-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parametersD3 andA8 are major influence factors on hydrodynamic characteristics of the pump, whilea0,j0 andRt are minor influence factors. The minimum contribution from bothD3 andA8 is 58% on head, and maximum contribution from bothD3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect toD3/D2 andA8/A10, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect toD3/D2. While for the other volute parametersa0,j0 andRt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.