滑动速度对碳纳米管-银-石墨复合材料电磨损性能的影响

采用粉末冶金法制备了碳纳米管-银-石墨复合材料,研究了圆周速度对复合材料摩擦系数、磨损量的影响。结果表明,当压力一定时,随着速度的加快,机械磨损的摩擦系数减小,而电磨损的摩擦系数增大;复合材料的电磨损量远远大于机械磨损的磨损量,电磨损时磨损量在V=10m/s处出现最小值,而机械磨损的磨损量随速度的加快而减小。     

小型无人船阻力CFD模拟方法

该文基于SolidWorks设计某无人船外型结构,建立无人船水动力学CFD模型,研究吃水深度、航速及流速方向等因素对船体流动阻力的影响。结果表明:吃水深度从4 cm增加到16 cm时,船舶速度减小,压力增大,所受到的水动力阻力从0.25 N增加到4.58 N;船舶航速在0.25～1.25 m/s时,压力和阻力无明显变化, 1.25～2 m/s时,阻力从2.07 N急剧增加到66.90 N;航速与水速夹角从0增大至90°时,速度减小,压力先增后减,阻力不断增大。该研究可为无人船的航线规划及安全航行的控制提供参考。     

含量变化对银-二硫化钼复合材料电磨损性能的影响

采用粉末冶金法制备银-二硫化钼复合材料, 通过改变材料中MoS2与Ag的含量,研究含量变化对复合材料电磨损性能的影响.结果表明,随着材料中MoS2加入量的增加,电刷与换向器之间接触电压降呈上升趋势,复合材料的摩擦系数与表面粗糙度先降低后趋于稳定,磨损率先下降后上升,在MoS2含量为15%时磨损率最低.     

电流密度对CNTs-Ag-MoS2-G复合材料滑动电摩擦磨损性能的影响

滑动电接触材料应具有良好的耐磨性能以及出色的导电性能,在航空航天领域中,制造先进的电接触材料尤为重要.实验中采用粉末冶金法制备CNTs-Ag-MoS2-G复合材料,研究了复合材料电摩擦磨损过程中的接触电阻及磨损率的变化,并通过扫描电子显微镜观察材料磨损后表面形貌.实验结果表明:在电流密度从5A/cm2增加到15A/cm2的过程中,复合材料接触电阻下降,体积磨损量增加,并且由于电弧侵蚀作用的影响,正刷的磨损量大于负刷,碳纳米管的特殊的基体增强作用及一定的导电导热能力使得CNTs-Ag-MoS2-G复合材料磨损量小于Ag-MoS2-G复合材料磨损量.     

电流密度对CNTs-Ag-MoS2-G复合材料滑动电摩擦磨损性能的影响EI

滑动电接触材料应具有良好的耐磨性能以及出色的导电性能,在航空航天领域中,制造先进的电接触材料尤为重要.实验中采用粉末冶金法制备CNTs-Ag-MoS2-G复合材料,研究了复合材料电摩擦磨损过程中的接触电阻及磨损率的变化,并通过扫描电子显微镜观察材料磨损后表面形貌.实验结果表明:在电流密度从5A/cm2增加到15A/cm2的过程中,复合材料接触电阻下降,体积磨损量增加,并且由于电弧侵蚀作用的影响,正刷的磨损量大于负刷,碳纳米管的特殊的基体增强作用及一定的导电导热能力使得CNTs-Ag-MoS2-G复合材料磨损量小于Ag-MoS2-G复合材料磨损量.     

摩擦条件对Al2O3／Cu复合镀层耐磨性的影响

研究了用复合电沉积法制备的颗粒增强Al2O3／Cu复合材料在10～100N载荷下和0．5～5m／s滑动速度下的耐磨性能及其磨损机制。结果表明，随载荷增加，磨损率升高存在一临界值，在中载时，随滑动速度升高，磨损率在3～4m／s时出现极小值，不同速度载荷时，表现出不同的磨损机制。     

刹车速度对C/C复合材料摩擦磨损性能的影响

以炭纤维针刺毡为预制体,采用CVI法并结合液相法制备了热解炭与树脂炭为基质炭的准三维C/C复合材料,并研究了这种材料在不同刹车速度下的摩擦磨损性能.研究表明:C/C复合材料热解碳结构为粗糙层,材料的摩擦磨损性能随刹车速度变化而变化,摩擦系数在刹车速度为10 m/s时达最大值,磨损量随刹车速度的增加而增加,而氧化磨损在25 m/s时开始大量产生,28 m/s的最大刹车速度时达最大值;X射线检测发现刹车后摩擦面碳结构有序度比次摩擦面低,且随着刹车速度的增大,这种降低程度依次增大.     

压光对彩喷纸涂层性能及喷墨打印性能的影响

目的研究压光条件变化对涂布纸涂层性能和喷墨打印性能的影响,得出最优的压光工艺条件。方法通过改变压光的温度(50,60,70,80℃)、压力(30,50,70,90 N/m)以及速度(7,11,15,19m/min),获得不同压光整饰后的彩喷纸,根据白度、平滑度、阶调以及色密度的测定结果,得出相应的最佳参数。结果白度随压光温度、压力、速度的增加均呈下降趋势;平滑度随压光温度、压力的增加均呈上升趋势,随速度的增加逐渐下降;阶调复制曲线的斜率随压光温度、压力的增加呈下降趋势,在低压光压力下,随着速度的增加曲线斜率先增大后减小;色密度随着压光温度的增加逐渐降低,在高压光速度下,随着压光压力的增加色密度下降,在低压光压力下,随压光速度的增加色密度先增大后减小。结论得出了最优参数设置,白度的参数(温度为70℃,压力为30 N/m,速度为15 m/min);平滑度的参数(温度为70℃,压力为90 N/m,速度为11 m/min);阶调再现性的参数(温度为70℃,压力为30 N/m,速度为11 m/min);色密度的参数(温度为60℃,压力为30 N/m,速度为15 m/min)。     

高温度梯度下Fe——石墨共晶定向凝固的研究

使用液态金属冷却定向凝固技术在G_L≈2lOK/cm,υ=0.5-100μm/s条件下对Fe—石墨共晶进行了试验研究。Fe—石墨共晶的界面形态和凝固组织可分为四种类型:(1)规则界面和定向细片石墨,(2)不规则界面和粗、细片石墨,(3)内生型界面和共晶团,(4)Fe—Fe_3C共晶。石墨片间距入与生长速度υ的关系如下: (1)υ=0.5-2μm/s时,λ=4.74xl0~(-6)υ~(-0.64)cm,υ=0.2μm/s时,石墨片具有良好的定向性;(2)υ=3-5μm/s时,λ随υ的增大而增大;(3)υ=5-10μm/s时,λ≈常数。     

PZT/环氧树脂1-3-2型压电复合材料的制备及性能

采用压电陶瓷基板与1-3型压电复合材料串联连接,沿表面两相互垂直的方向切割PZT陶瓷,在切槽间浇注环氧树脂,制备出新型的1-3-2型压电复合材料.实验测试了材料的压电和介电性能,结果表明其d33常数达到400 pC/N,振动位移113.5pm,声速3500m/s,声阻抗17.6Mraly,厚度机电耦合系数0.62,带宽3.6kHz,相对介电常数817,介质损耗0.02.     

射频磁控溅射纳米二氧化钒薄膜的电致相变特性

采用射频磁控溅射方法和热处理工艺制备了二氧化钒（VO2）薄膜,并制作了金属钨／VO2／金属钨三明治结构,通过改变金属钨／VO2／金属钨三明治结构中VO2薄膜与金属钨电极的接触面积,研究了VO2薄膜的电致相变特性．采用x射线衍射仪（XRD）、扫描电子显微镜（SEM）、四探针和半导体参数测试仪对VO2薄膜的结晶取向、表面形貌、方块电阻和,I-V特性进行了测试．实验结果表明,所制备的VO2薄膜为具有热致相变特性的单一组分VO2纳米薄膜,在热激励下,薄膜的方块电阻相变幅度达到2个数量级;在电压的激励下,VO2薄膜与金属钨的接触面积为12μm×12um时,电流发生跳变的阁值电压为9．4V,随着接触面积的减小,闽值电压也逐渐降低．     

不同空气侧风速下微通道蒸发器换热特性实验研究

搭建微通道蒸发器性能实验台,采用控制变量法研究不同空气侧风速下微通道蒸发器表面温度分布、制冷剂进出口压力的变化规律,计算换热量和换热系数,从而分析空气侧风速对微通道蒸发器的流量分配特性和换热效果的影响。结果表明,随着风速增大,微通道蒸发器制冷剂流量分配不均匀性增大,进出口压力波动振幅和周期增加,压降增大,风速2 m/s时微通道蒸发器换热效果最佳。     

Pressure-drop reduction and heat-transfer deterioration of slush nitrogen in horizontal pipe flow

Cryogenic slush fluids such as slush hydrogen and slush nitrogen are two-phase, single-component fluids containing solid particles in a liquid. Since their density and refrigerant capacity are greater than those of liquid-state fluid alone, there are high expectations for the use of slush fluids in various applications such as clean-energy fuels, spacecraft fuels for improved efficiency in transportation and storage, and as refrigerants for high-temperature superconducting equipment. Experimental tests were performed using slush nitrogen to obtain the flow and heat-transfer characteristics in two different types of horizontal circular pipes with inner diameters of 10 and 15 mm. One of the primary objectives for the study was to investigate the effect of pipe diameter on the pressure-drop reduction and heat-transfer deterioration of slush nitrogen according to changes in the pipe flow velocity, solid fraction and heat flux. In the case of an inner diameter of 15 mm, pressure drop was reduced and heat-transfer characteristics deteriorated when the pipe flow velocity was higher than 3.6 m/s. On the other hand, in the case of an inner diameter of 10 mm, pressure drop was reduced and heat-transfer characteristics deteriorated when the pipe flow velocity was higher than 2.0 m/s. From these results, it can be seen that a larger pipe diameter produces a higher onset velocity for reducing pressure drop and deteriorating heat-transfer characteristics. Furthermore, based on observations using a high-speed video camera, it was confirmed that pressure drop was reduced and heat-transfer characteristics deteriorated when the solid particles migrated to the center of the pipe and the flow pattern of the solid particles inside the pipe was pseudo-homogeneous.     

电镀锌板摩擦系数的影响因素分析

采用销盘摩擦试验研究了正压力和速度对电镀锌板摩擦系数的影响规律,运用正交试验及方差分析的方法研究了正压力、速度、镀锌层对摩擦系数的影响水平.结果表明:当速度在5654.86～9424.78 mm/min,正压力在0.3～5 N的范围内,随着正压力的增大,镀锌板的摩擦系数逐渐降低,随着速度的增大,摩擦系数也逐渐增大,镀锌层对镀锌板摩擦系数影响最大.     

变压吸附制氧过程数值模拟与分析

根据变压吸附制氧理论,对制氧量为3 m3/h的小型PSA制氧系统进行吸附过程数值模拟及分析,结果表明:产品纯度随吸附床层间隙率减小而递增,但需付出增加耗能的代价;随着速度的增加,进出口压降基本呈线性增加,而产品纯度呈类抛物线状减小;当吸附床层高径比增加时,进出口压降呈线性增加,而产品纯度在较低值时增长较快;流体相最佳流速控制在0.05 m/s左右.间隙率控制在0.35-0.4之间,高径比控制在9.5-12之间,能够很好地降低进出口压差,使整体吸附具有节能的效果.     

Numerical Study of Air Compressibility During Horizontal Pneumatic Transport

Using numerical simulations, the effect of the compressibility of air on the flow pattern of particles and pressure drop in the presence of particles during horizontal pneumatic transport operating under negative pressure was examined. The length and inside diameter of the pipeline were 30 m and 40 mm, respectively, and the chosen particles (4 mm in diameter) had densities of ρ_p = 1000 and 2000 kg/m³. The mean air velocities at pipe the inlet were U_inlet = 19, 22, and 28 m/s, and the range of the mass flow rate ratios of particle to air, μ, was varied up to 2.0. For a given inlet air velocity, the difference in the flow pattern between compressible and incompressible flow calculation is generally small. For ρ_p = 1000 kg/m³ particles the additional pressure drop in compressible flow increases when μ is above 0.5 and U_inlet is 28 m/s, μ is above 1.3 and U_inlet is 22 m/s, and μ is above 1.5 and U_inlet is 19 m/s. In these cases, the particle flow pattern is homogeneous. For ρ_p = 2000 kg/m³ particles, the pressure drop increases only when μ is above 1.5 and U_inlet is 28 m/s. The difference is not noticeable when the particle flow pattern is heterogeneous. Also, the difference in the additional pressure drop is much larger during homogeneous flow than heterogeneous flow.     

层状复合材料磁电效应的数值分析

压电与压磁(或磁致伸缩)层合板具有大的乘积效应磁电效应。本文采用有限元分析方法对压电/压磁层合板的磁电转换进行了计算,结果表明:外磁场方向对磁电转换效应有很大的影响,在层合板上下两面增加约束可以大大提高层合板的磁电转化效应;感生电压值随压磁/压电板厚比的增加而增加,而整个层合板的电场强度值在板厚比为1时达到最大。     

粒径对Ni/硅橡胶复合材料压敏性及介电性质的影响

采用不同粒径的Ni粉与硅橡胶(110型)按质量比2.4∶1.0制成Ni/硅橡胶复合材料, 分别测量了其压敏导电性及介电性质, 并结合扫描电镜照片对其微观导电机制进行了分析。结果表明随着填料Ni粉粒径的减小, Ni/硅橡胶复合材料的直流电阻率对外加压强更加敏感: 在低压强下, 粒径为74、48和18 μm的样品的电阻率随压强的变化率分别为1.73×104、2.59×104和3.71×10 4 Ω·m/kPa。样品直流电阻率陡降的区域随粒径的减小向压强较小的方向移动, 显示出复合材料的渗流阈值与填充粒子的粒径有关: 粒径越小, 渗流阈值也越小。Ni/硅橡胶复合材料的交流电导率、介电常数、介电损耗均随填料Ni粉粒径的减小而变大: Ni粉粒径为18 μm的Ni/硅橡胶复合材料的电导率约为10-2 S·m-1, 比74 μm粒径样品的电导率(约10-7 S·m-1)提高了5个数量级; 对应的介电常数由约102提高到约103。改变填料Ni粉粒径可以有效地调节复合材料的弹性和压敏、电输运特性。      

Experimental study on the separation performance of a novel gas–liquid separator

A novel two-stage dynamic separator called high-gravity cyclone separator (HGCS) has been designed for gas–liquid separation. It is mainly composed of a cyclone chamber and rotary drum. In this study, its performance, including the separation efficiency and pressure drop, is experimentally investigated, and the effects of the operating conditions and drum parameters are evaluated. For droplets with a mean diameter of 7 μm, the results indicate that the optimal gas inlet velocity and high-gravity factor are 12 m/s and 59.4, respectively, and the separation efficiency reaches 98 %. The effect of liquid concentration is sensitive to the high-gravity factor. At a liquid concentration of 57 g/m³, the maximum efficiency will be 98.75 % when increasing the high-gravity factor to 85.6. Furthermore, a smaller radial height is preferable when the gas inlet velocity is greater than 12 m/s, and a better separation efficiency can be obtained by increasing the drum length to 190 mm. However, when the length is 235 mm, the efficiency will be poor because of the Kelvin–Helmholtz and Rayleigh–Taylor instabilities. Compared with the predominant roles of gas inlet velocity, drum length and radial height in pressure drop, the effects of liquid concentration and high-gravity factor are small.