碳纤维复合材料薄壁圆筒的轴向导热系数测试

碳纤维复合材料薄壁圆筒为各向异性导热，其轴向导热系数是筒体温度场理论计算、成型工艺优化的重要参数。碳纤维复合材料圆筒由于较小的截面面积给筒体加热、热量有效传递带来了较大困难。本文以平板材料导热系数的稳态法测试国家标准为基础，基于傅里叶一维稳态导热原理，设计了一套用于薄壁圆筒轴向导热系数测试的装置，采用双试件对称加热、辐射换热防护及热对流环境控制等实现了热量沿筒体轴向的有效传导，利用该装置对导热系数已知的铝筒进行测试，验证了该装置设计的可行性，得到了碳纤维复合材料薄壁圆筒的轴向导热系数为（4.60±0.13） W/(m•K)。     

Drilling machinability of engineering ceramics under low-frequency axial vibration processing by sintering/brazing composite diamond trepanning bit

Thin-wall diamond trepanning bits are extensively used for processing hard and brittle materials such as engineering ceramics. However, it is difficult to achieve high-efficiency processing of engineering ceramics at a constant feed speed, because of high dynamic compressive strength, high hardness, and low density of engineering ceramics. In this study, a novel composite diamond bit combining sintering and brazing has been designed, along with the low-frequency axial vibration technology, to realize the continuous hole processing of engineering ceramics. Drilling experiments have been conducted on Al₂O₃ and SiC engineering ceramics with a constant feed speed. The variation of axial force, micromorphology of hole wall surface drilled, as well as the method of removing nesting during the drilling process were analyzed. According to the results, the novel composite diamond bit fabricated by combining sintering and brazing, can achieve the continuous hole processing of engineering ceramics at a constant feed speed, including Al₂O₃ and SiC. Compared to the conventional drilling (CD), the low-frequency axial vibration drilling (LFVD) can significantly reduce the axial force, and produce fewer plastic scratches on the hole wall surface drilled. In particular, the automatic blanking ratio approaches to 100% by LFVD, and only about 73.58% by CD. It can be concluded that LFVD technology can be used to realize continuous hole processing of engineering ceramics. The research results achieved in this study show that the drilling machinability of engineering ceramics by LFVD and novel composite diamond bit is good. Accordingly, this study provides a useful reference for continuous processing or batch production of engineering ceramics at a constant feed speed.     

BHA轴向磁干扰对方位测量误差的影响——基于人工磁场模拟方法

井下钻具组合（BHA）磁化形成的轴向磁场干扰是定向组件磁方位测量的一个重要的误差因素。为了对该误差因素进行独立分析，建立了大型三轴亥姆霍兹线圈人工磁场系统作为研究环境，使用不同磁通量的多个磁化组件作为干扰源研究在理想环境中轴向干扰磁场对定向组件的影响，并在此基础上提出了一种估算磁化组件磁极强度和校正轴向干扰的方法，通过改变空间姿态和三轴亥姆霍兹线圈磁场强度，分析了在不同井斜角、方位角和磁倾角的井眼轨迹中，轴向磁干扰对定向组件方位测量误差的影响，最后证明了校正磁性组件的轴向干扰方法，可以有效地提升BHA定向组件的方位测量精度。     

入口弯管对矿用轴流通风机气动性能影响的数值研究

以某大型矿用低压轴流式通风机为研究对象, 采用气体动力学性能试验和数值模拟的方法研究了不同入口弯管对风机性能的影响, 重点分析了入口弯管引起的叶轮内部流动特征和损失分布的变化规律。研究结果表明, 风机入口采用弯管连接缩短了进口管道的轴向长度, 节省了地下空间, 但同时来流的均匀性受到影响。弯管内气流速度梯度较大, 管道内侧易发生流动分离, 产生回流区, 增大了流体流动时的能量损失, 风机的整体性能下降。弯管与叶轮入口之间的连接长度会影响内部流场, 当附加直管段较长时, 来流均匀性得到提高, 风机性能有所改善。     

带式输送机驱动滚筒的有限元分析

针对带式输送机驱动滚筒轴向受力情况,提出了正态分布模型,结合ANSYS-APDL的语言编辑能力,用ANSYS Workbench对均匀分布、一阶正弦分布和正态分布的4种模型进行有限元分析,得到驱动滚筒应力应变图及位移变形的对比情况,为日后实验验证与优化设计提供理论支持。     

KJS-Y系列矿用水动力降尘器的改进设计

针对当前KJS-Y系列降尘器效率低的问题,通过调整叶轮轴向间隙与径向间隙参数,分别对不同安装参数的降尘器进行数值模拟,通过数值模拟分析特定截面压力分布情况,确定了叶轮最佳安装参数,大大提高了降尘器的工作效率,同时降低了设计成本。     

Comparative analysis of energy absorption behavior of tapered and grooved thin-walled tubes with the various geometry of the cross section

ABSTRACT

In this paper, Crush force efficiency (CFE), Specific Energy Absorption (SEA), Energy Absorption per Crush Length (E_cl), Maximum and average crush forces of straight and grooved tapered thin-walled tubes with various cross-section shapes (circle, ellipse, square, rectangle, hexagon, and octagon) have been studied. The effects of taper, the groove (as initiator) and their interaction have been presented in the current study using Finite Element Method as a numerical method. The tubes have the same volume, height, average cross-section area, thickness and material and have been subjected to axial and oblique dynamic loading. The results of simulations show that the section's geometry, taper and groove addition have a significant effect on energy absorption behavior and the hexagon cross section have better energy absorption behavior compared with other considered geometries. On the other hand, it was found that the behavior of these structures could improve against dynamic axial and oblique impact loading with the cost-effective geometry modifications. These results could help to improve and choose appropriate energy absorber structure based on desirable crush force and energy absorbing characteristics.     

Mixing characteristics for the single and air-water two-phase flows in miniaturized parallel multichannel-based devices

Investigation on the miniaturized parallel multichannel-based devices packed with glass beads to improve the mass exchange execution is the critical focal point of the current study. One of the essential parameters to specify the miniaturized devices' flow distribution is the residence time distribution (RTD). In the present context, the RTDs of a liquid tracer were investigated for the air-water multiphase flows (concurrent) across the multichannel-based miniaturized devices (comprising of 11 similar dimensional parallel channels). The devices were variable in height and packed with glass beads. The conductivity estimations generated the RTD curves and were addressed by the axial dispersion model (ADM). The fluid-flow rates differed within the range of 5–23 ml min⁻¹. The axial dispersion coefficients and the rate of the specific energy dispersion were investigated. The effects of pressure difference and geometry on the hydrodynamic attributes and mixing properties were well-illustrated, and the new correlations were suggested.     

气动齿轮马达泄漏量的计算研究

由于气动齿轮马达具有许多优点,在工程中广泛应用。根据齿轮式气动马达的结构和工作原理,按照流体力学方法推导了气动齿轮马达的径向泄漏耗气量和轴向泄漏耗气量,对一种锚杆钻机使用的气动齿轮马达进行了泄漏量计算。