Prediction of air filter efficiency and pressure drop in air filtration media using a stochastic simulation

In this paper, we discussed the relationship of filter efficiency and pressure drop with the porosity, fiber diameter and filter thickness by Geodict®. We found that filter efficiency has exponential relationship with filter porosity, fiber diameter and thickness. Furthermorethe pressure drop has a linear relationship with filter thickness and exponential relationship with filter porosity and fiber diameter, respectively. The influence of electrostatic charge on the particle deposition has been investigated. Simulation results were compared with the actual test results by TSI 3160.     

红麻料片的压缩特性及压力与压缩密度的数学模型

进行了红麻料片在闭式容器内的压缩试验。对红麻料片的压力－变形曲线分析表明：红麻料片的压缩过程存在松散、过渡和压紧３个阶段。进一步对试验数据进行统计分析,建立了红麻全秆料片的压力ｐ与压缩密度γ在松散阶段的数学模型为γ＝ａ＋ｂｐ,过渡和压紧阶段的数学模型γ＝ａｐ＾ｂ。在松散压缩阶段通过增加压力来提高红麻料片的压缩密度效果较好。     

斜轴式液压变压器效率特性分析

建立了斜轴式液压变压器的排量模型、流量模型、转矩模型和效率模型;在此基础上,绘制了液压变压器的等效率曲线图,揭示了斜轴式液压变压器的效率特性.理论分析与试验结果表明:斜轴式液压变压器在正常工作情况下理论总效率可达到70%左右,而且高效区的范围较宽;液压变压器的总效率随着负载口实际流量或缸体转速的增加有先增大后减小的变化趋势,随着负载口压力或配流盘转角的增加也呈先增大后减小的变化趋势.     

离心泵内部动静干涉作用的数值模

采用压力边界条件对一单级单吸蜗壳式离心泵进行了三维非定常数值模拟计算,模拟过程中给定离心泵入口总压和出口静压,结合滑移网格技术,成功地捕捉了叶轮-蜗壳的动静干涉作用引起的非定常流动特性.计算结果表明,离心泵内流场周期性脉动明显,蜗壳内静压及叶片载荷分别以叶片旋转频率、叶轮旋转频率发生周期性变化.蜗壳几何形状的不对称性影响了动静干涉作用在离心泵内部的传播,引起了离心泵内流动沿周向分布不均匀现象.     

食品超高静压处理中热效应问题的研究进展

在食品的超高静压处理中,由于压缩作功使其温度发生改变,温度随着压力的升高而增加(压致升温),所以不可避免地会产生热效应问题。该文主要综述了食品超高静压处理中温度压力随时间的变化规律,传压介质和食品成分对压致升温的影响,以及食品超高静压处理中的传热和压致升温对微生物的影响等问题。     

双吸离心泵叶轮交替加载设计方法

双吸离心泵内部的压力脉动是影响机组运行稳定性的关键因素之一。为了减轻压力脉动,分析了引起双吸离心泵压力脉动的主要原因,研究了不同类型的叶片载荷曲线对双吸离心泵流态的影响,建立了叶片加载方式、叶片出口倾角和叶轮交错角与泵内二次流及压力脉动的关系,提出了能够抑制二次流、降低压力脉动的叶轮交替加载设计方法。在新的设计方法中,叶片载荷曲线具有盖板前加载、轮毂后加载的混合加载模式。基于该方法所生成的双吸叶轮具有轮毂两侧交错布置、叶片出口边正向倾斜、盖板和轮毂包角差小的特点。通过在一大型引黄灌溉泵站的试验表明,该方法可将双吸离心泵压力脉动主频的幅值降低到原来的1/5左右,同时还可改善泵的最优效率和高效区。该方法为大功率双吸离心泵的优化设计和更新改造提供了一种新的技术途径。     

高压断路器液压操动机构管道特性研究

以550 kV SF6高压断路器液压操动机构为研究对象,分析了液压机构分合闸过程中的管道损失和压力波传递效应,建立了管道损失和压力波动分布参数模型.对系统进行了建模和仿真,讨论了液压机构的管道特性及管道结构参数对系统分合闸性能的影响.试验验证了仿真结果,证明了仿真模型的准确性.     

轴流泵内部流场压力脉动性能预测与试验

基于雷诺时均控制方程和标准k-ε湍流模型,应用SIMPLEC算法,对轴流泵全流场进行三维非定常数值模拟,得到轴流泵在不同工况和不同导叶数内部流场的压力脉动特性.数值分析与试验结果表明:轴流泵内最大压力脉动发生在叶轮进口处;在偏离设计工况点较大的流量时,压力脉动幅值明显增大;导叶数减少会增大导叶出口处的压力脉动;脉动频率受叶轮转动频率控制,导叶数对压力脉动频率基本无影响.     

水润滑塑料合金轴承的弹性变形及其影响

从分析水润滑塑料合金轴承不在动压条件下的弹性变形入手，推导出支承间隙方程式，并通过傅立叶级数对压强函数进行展开，分析了弹性变形和压强的关系。最终得出动压条件下压强分布函数和弹性变形函数，并以此对实际工况的一些现象进行了解释。     

Effects of retinal ganglion cell apoptosis on delayed rectifier K+ currents

AIM: To investigate the effects of rat retinal ganglion cell (RGC) apoptosis on delayed rectifier K⁺ currents (I_K). METHODS: The retinas of 2~3 d newborn Sprague-Dawley rats were dissociated into cell suspension by trypsin digestion. The RGCs were cultured and divided into control group, pressure 0.5 h group, pressure 1 h group, pressure 1.5 h group and pressure 2 h group. The cells were cultured regularly for 6 d in control group, and the cells in other groups were cultured regularly for 6 d and gave pressure of 80 mmHg for 0.5 h, 1 h, 1.5 h and 2 h, respectively. The rhodamine 123 fluorescence from labeled RGC mitochondrion was detected by continuous wavelength multifunctional microplate detection instrument. The membrane capacitance (C_m) in different groups and I_K in the pressure 1 h group were recorded from the RGCs by whole-cell patch-clamp technique. RESULTS: No difference of rhodamine 123 fluorescence in the RGC mitochondria between control group and pressure 0.5 h group was observed. Rhodamine 123 fluorescence in the other 3 groups was significantly lower than that in control group (P<0.05). No difference of the C_m between control group and pressure 0.5 h group was found, and the C_m in the other 3 groups was significantly lower than that in control group (P<0.05). The amplitudes of I_K were higher than that in control group. At the test potential from -10 mV to 60 mV, the current density in pressure 1 h group was significantly higher than that in control group (P<0.05). The maximal conduction (G_max) in pressure 1 h group was significantly higher than that in control group. The voltage for I_K channel half-activation (V_1/2) in pressure 1 h group declined comparison with control group (P<0.01), and the k value had no significant difference between the 2 groups. CONCLUSION: Retinal ganglion cell apoptosis accompanies with delayed rectifier K⁺ current enhancement.