双体均速管流量计的创新优化设计

基于流动控制原理,将文丘里效应应用到均速管流量计中,建立了几种双体均速管模型。通过数值分析不同模型的流量系数及其引起的永久压损随速度的变化规律,并与威力巴原型进行比较,从中选取最优模型。     

新型插入式双V型流量计优化设计及数值模拟

基于插入式流量计差压原理与安装方式,设计了一种新型插入式双V型流量计。在不同的流速条件下,对400mm口径管道新型流量计进行数值模拟。引用k-ε湍流模型及SIMPLIC算法进行计算,得到了流量系数随速度的变化规律。以威力巴流量计作为参照对象进行同等条件下的数值模拟,将二者特性进行对比分析。结果表明:新型插入式双V型流量计集合了威力巴流量计与文丘里管的优势,大幅度提升了输出压差,压损比较威力巴降低了7.7%,扩大了低速稳定范围,其性能更优。     

适用水泥行业的新型流量计

在化工、石化、钢铁、电力、供热和水处理等行业各种流量计应用十分普遍．用于测量各种液体和气体的流量。随着工业领域对流量测量的要求不断提高．在市场上各种新型的流量计已不是很新鲜的事物。它们根据测量机理冠以不同的修饰术语，如科里奥利，超声波、电磁、涡街流量计．比起传统的容积式、文丘里管、机械孔板式流量计来，新型流量计有更新颖的特点．在精确度、可靠性、重复性、可维护性方面和老式的流量计相比有显著的差异。     

Verabar均速管流量传感器计算软件的使用

本文介绍了Verabar均速管流量传感器的计算软件-Veracalc的使用,对该软件的操作界面和使用步骤作了详细的说明。     

内外管压差流量计的压力损失

针对现有流量计的节流方式存在压损大、扰动大以及差压信号稳定性不足等问题,设计了一个新型内外管差压流量计。在介质为水的情况下,对不同管径的六种模型进行Fluent仿真对比,结果表明异径管管径为10/20这一模型为最优模型。此外,在相同条件下,将该最优模型与等径比β为0.6的V锥流量计进行压损对比,得出该内外管压差流量计耗能仅为常规V锥流量计的不到10%的结论。     

均速管流量计气固两相绕流固粒分布特性的研究

采用大涡模拟的方法,对威力巴流量计在气固两相流中的特性进行了数值模拟。初步揭示了连续相中固粒在检测杆截面周围的分布特性以及不同粒径的固体颗粒对检测杆碰撞而产生的磨损量。     

The effect of low Reynolds number flows on pitot tube measurements

An investigation on the low Reynolds number effect on hemispherical-tipped Pitot tube measurements was performed by measuring the center-line velocity during the laminar flow of a Newtonian fluid in a 25 mm (1 in.) diameter vertical recirculating pipe loop. The primary objective of the study was to reconsider the available low Reynolds number Pitot tube data in the literature with modern instrumentation.Using the results of this experimental study, a correlation that accurately predicts the low Reynolds number Pitot tube behavior has been developed. The correlation accounts for an additional viscous term in the relationship for the pressure coefficient (C_p) which is not accounted for in Bernoulli's Equation. The correlation is semi-empirical and accurately fits experimental data gathered in this study, as well as a significant body of experimental data available in the literature. The correlation, which is based on a Pitot tube Reynolds number calculated using the opening diameter (d), has been shown to be provide more accurate predictions of C_p for a wide range of opening diameter to outer diameter ratios (0.22≤d/D≤0.6) than available correlations based on outer diameter.The transition Pitot tube Reynolds number, below which Bernoulli's Equation is no longer appropriate, was predicted to be approximately 35, compared to a value of 79 obtained from fitting data collected by Barker. The correlation developed in this study provides smoother transitions at both ends of the low Reynolds range. At the low end (Re<10) it converges with a Stokes Law’ analogy, while at the critical transition (Re~35) it converges asymptotically with Bernoulli's Equation. The correlation also accurately predicts the behavior of the pressure coefficient with Reynolds numbers between these ranges.     

基于数值仿真的某型火炮身管设计压力曲线系统分析

火炮身管设计压力曲线给出火炮发射过程中身管各截面承受的最大压力,是设计身管壁厚的依据。高低温压力法只考虑了装药温度变化对膛压的影响,从系统的角度考虑,装药质量、药室增长量、弹丸质量变化也会对膛压造成影响。通过对某型火炮内弹道模型进行数值仿真,分析上述因素变化对膛压和身管设计压力曲线的影响,并给出了各因素综合作用下的身管设计压力曲线。研究表明,装药质量、装药温度和药室增长量变化均对膛压有较大影响;装药质量和装药温度直接影响身管设计压力曲线的组成。     

内置传感器的管道数值模拟及优化设计

在机械设计等工程实际中,管道的压力损失计算是其设计的一项非常重要的任务.为了确定某管道内置传感器的最佳插入点,就要计算因传感器而引起的管道流动损失,建立了不同设计的内置传感器管道的数学模型,使用目前通用的专业CFD数值计算软件FLUENT对管道内流场进行三维数值模拟,并将不同设计的计算结果进行对比分析,认为流动损失相对较小且流场流速稳定度较好的型4为最优设计,计算结果为该管道的进一步优化设计提供了参考.     

Process simulation and optimization of laser tube bending

A 3D thermomechanical finite element analysis model for laser tube bending is developed based on the software MSC/Marc. The processes of single- and multi-scan are analyzed numerically. The gradient and development of the temperature between the laser scanning side and the nonscanning side leads to the changing complexity of the stress and strain. Consequently, the length of the laser scanning side becomes shorter than that of nonscanning side after cooling. The length difference between both sides makes the tube produce the bending angle. The relationship between the number of scans and the bending angle is about in direct ratio. The bending angle induced by the first irradiated time is largest. Meanwhile, the finite element simulation is integrated with the genetic algorithm. Aiming at different process demands, corresponding objective functions are established. Laser power, beam diameter, scanning velocity, and scanning wrap angle are regarded as design variables. Process optimizations of maximum angle bending and fixed angle bending after single laser scan are realized. Groups of optimized process parameters can be obtained according to different optimization objectives. The bending angle can approach to the maximum when the laser power, spot diameter, scanning velocity, and scanning wrap angle are 381.24 W, 3.37 mm, 16.34 mm/s, and 123.1°, respectively. When the laser power, spot diameter and scanning velocity are 426.12 W, 4.9 mm, 14.31 mm/s respectively, a fixed angle bending can be achieved.     

V形调节球阀的结构优化

利用计算流体力学CFD软件,研究V形调节球阀在不同开度下的流量特性并进行数值模拟分析。结合实验数据,优化V形切口形状,使其与理想的流量特性趋于一致,提高了阀门的调节性能。     

异型排列管束蒸发器壳程流场数值模拟

制冷装置蒸发器应用广泛,其壳程内流体的流体力学行为对蒸发器蒸发性能影响显著.利用Gambit软件建立了5种管束排列方式下蒸发器壳程流体流动的二维模型,采用Fluent软件对流体在壳程通道内的流动进行数值模拟.模拟结果表明,相比管束正方形排列和转角正三角形排列,异型排列方式更有利于壳程流体与管换热面接触,流体绕流异型排列管束的压力损失小于正三角形排列.研究结果为蒸发器设计及生能优化提供参考依据.     

汽车引擎盖内板冲压工艺设计及数值分析

针对复杂的汽车引擎盖内板在冲压成形中容易产生破裂缺陷的问题,利用AutoForm有限元软件对引擎盖内板进行工艺设计以及数值分析.将正交试验设计方法与冲压数值分析相结合,探讨冲压方向、压边力、拉深筋圆角半径、拉深筋深度和摩擦因数对汽车引擎盖内板冲压成形质量的影响,并利用直观分析法,确定最优工艺参数组合,最终达到理想效果.     

皮托管测量风速时GUM评定不确定度的偏差修正

针对不确定度表示指南法(GUM)进行皮托管测量风速值的不确定度评定时,测量结果存在偏差的现状,为确认该方法的适用性,并获取其偏差的修正值,首先采用GUM和蒙特卡洛法(MCM)对皮托管测量风速值的不确定度进行评定;然后,通过JCGM 101:2008 GUM supplement 1给出的方法,对GUM的适用性进行验证;最后,将GUM与MCM获取的风速测量结果进行对比。结果表明,GUM方法依然适用于皮托管进行风速测量时的不确定度的评定; GUM评定的结果标准不确定度产生了负偏差,其相对于实测风速值的偏差率为-0. 611 8×10-5,对应的修正值为"0. 611 8×10-5×实测风速值",由于该值相对于实测风速值较小,因此,在应用时可根据实际情况,决定是否对其进行修正。