弯管防磨罩弯制装置

适用于普通弯管机使用的弯管防磨罩弯制模具,可满足同一种管子的同一种弯曲半径的不同角度、不同直段长度的弯管防磨罩弯制,具有通用性好、制造工艺性好的特点。     

管子弯制工艺方法讨论

弯管是锅炉制造工艺中应用最多的方法,几乎所有的受热面管子都存在着弯制的问题,弯管如何达到要求通过弯制工艺实现的,通过有芯弯管和无芯弯管的受力分析和理论计算,认为要工艺方法正确,可以实现难度较大的弯管制作。     

浅析蛇形管冷弯后的热处理要求

过器器、省煤器、蛇形管、冷管采用R／D／小于1．4时，为保证弯管质量，必须做弯管工艺评定和弯后热处理。     

φ69.85/R175无直段弯管工艺研究

介绍厚壁弯管机上使用的φ69.85/R175无直段弯管模的结构与改进设计。经实践证明该弯模结构合理,提高了弯管制造质量。     

小R弯管制造工艺探讨

文章介绍了在普通弯管机上弯制小R弯管的工艺方法及模具结构.通过大量工艺试验,针对小R弯管计算的常规公式和经验公式进行了修正,极具参考价值.尤其对一些暂无小R弯管专用设备的厂家,更具指导意义.     

空间弯管的制作与质量控制

本文介绍了锅炉空间弯管的制作过程及工艺措施的改进，并提出空间弯管质量的检验方法。     

弯管进气对离心压气机效率的影响

对弯管进气的离心压气机进行数值模拟计算,通过与直管进气试验和数值模拟结果的分析对比,研究弯管对离心压气机效率的影响,分析在3种不同形式的弯管进气条件下压气机效率的变化。研究结果表明:弯管进气时压气机效率有所降低,不同形式的弯管进气对压气机效率的影响不同。在恒定转速小流量工况下,弯管与直管进气压气机效率相差较小,随着流量的增加,弯管进气与直管进气压气机效率差值逐渐增大;当转速不同时,弯管进气造成叶轮进口严重的气流不均匀流动,使效率下降,高速大流量工况效率下降最为明显,其中普通90°弯管进气效率最大降幅为7%。     

90°水平弯管内水煤浆的阻力特性试验研究

在水煤浆综合输送中试试验台上,将管径为50mm的90°水平弯管配以不同弯径比,对神华煤水煤浆进行了阻力特性试验研究。根据试验结果,对弯管内水煤浆的局部压力损失、摩擦阻力损失及弯管内流动有效长度等方面的一些特性进行总结。结果表明:采用合理的定义及方法,水煤浆弯管内流动的一些特性存在较为明显的规律。     

弯管工艺最小壁厚的回归分析

弯管加工的难易程度与其相对弯曲半径(r/d)和相对壁厚(t/d)有关,上述值越小,弯管出现缺陷的风险越大。在给定的工况下,将一些临界合格的弯管规格作为样本进行回归分析,可以得到该工况下的边界规律,由此判断弯管所需的工艺最小壁厚,降低设计成本和制造风险。     

关于TFR对弯管工艺评定的意义的探讨

EN12952-5标准提出了管子成形比率TFR(Tube Forming Ratio)的概念,并用它来规定弯管工艺评定的有效覆盖范围。TFR能直观地反映出弯管加工的难易程度,但不表示某一弯管工艺评定对于该TFR下所有弯管的成形效果具有普遍代表性。通过数值模拟可验证,在相同工况下,相同TFR的弯管在弯后应变与减薄率方面,有较明显的差异。     

不同折转角弯曲扩压叶栅性能数值研究及优化设计

通过数值模拟研究不同折转角弯曲扩压叶栅中弯高、弯角对其气动性能影响,利用试验设计和遗传算法实施方案选择和优化设计,给出不同折转角下弯高、弯角最佳匹配范围。结果表明,3种折转角情况下弯高、弯角的最佳匹配规律是不同的,随着扩压叶栅折转角的增大,较小的弯高和弯角匹配将更有效减少气动损失。     

Determination of flexibility factors in curved pipes with end restraints using a semi-analytic formulation

Piping systems are structural sets used in the chemical industry, conventional or nuclear power plants and fluid transport in general-purpose process equipment. They include curved elements built as parts of toroidal thin-walled structures. The mechanical behaviour of such structural assemblies is of leading importance for satisfactory performance and safety standards of the installations. This paper presents a semi-analytic formulation based on Fourier trigonometric series for solving the pure bending problem in curved pipes. A pipe element is considered as a part of a toroidal shell. A displacement formulation pipe element was developed with Fourier series. The solution of this problem is solved from a system of differential equations using mathematical software. To build-up the solution, a simple but efficient deformation model, from a semi-membrane behaviour, was followed here, given the geometry and thin shell assumption. The flexibility factors are compared with the ASME code for some elbow dimensions adopted from ISO 1127. The stress field distribution was also calculated.     

Analogy of forced convective heat transfer between developing laminar flows in curved pipes and orthogonally rotating pipes

Based on a quantitative analogy between developing laminar flows in curved pipes and orthogonally rotating straight pipes, a corresponding analogy of forced convective heat transfer in the entry regions of the pipes is described through similarity arguments and computational studies. Three‐dimensional developments of these flows are characterized by secondary flows due to the centrifugal or the Coriolis forces. Similarity considerations taking the secondary flow into account suggest a remarkable effect of the Prandtl number or the heat transfer structure, which is demonstrated by the computational results. When the curvature parameter of curved pipe flow and the Rossby number of rotating pipe flow are sufficiently large, it is shown that the development of the temperature fields and the Nusselt numbers of the two flows are similar when the governing parameters and the Prandtl numbers of the two flows are equal. © 2000 Scripta Technica, Heat Trans Asian Res, 29(6): 512–522, 2000     

CFD技术在汽轮机定子线圈冷却水流量测量中的应用

利用超声波流量计检测大型汽轮发电机定子线圈冷却水流量大小,可直接判断冷却水的堵、漏,从根本上解决定子绕组冷却水堵塞问题,但超声波流量计用于弯管段测量时存在误差。本文利用CFD技术计算了某火电厂定子线圈内冷却水的流速分布,分析了管内流动对超声波测流的影响,获得了不同测点处流量误差的变化趋势。采用CFD技术可确定超声波流量计的最佳安装位置,为获得准确的流量提供理论依据。     

Liquid-solid separation phenomena of two-phase turbulent flow in curved pipes

The present study is to contribute some knowledge of phase separation phenomena of liquid-solid two-phase turbulent flow in curved pipes and provide a basis for the invention and development of a new type of curved pipe separator. Firstly, the solid-liquid two-phase flows in two-dimensional (2D) curved channels were numerically simulated using a two-way coupling Euler-Lagrangian scheme. Phase distribution characteristics of 2D curved channel two-phase flow were examined under conditions of different particle size, liquid flowrate and coil curvature. Based on the numerical results, the dynamic effects and contributions to phase separation of particle-subjected forces, including centrifugal force, drag force, pressure gradient force, gravity force, buoyancy force, virtual mass force and lift force, were exposed by kinematic and dynamic analysis along particle trajectories. Secondly, measurement of particle size and concentration profiles in helically coiled tube two-phase flow was conducted using a nonintrusive Malvern 2600 particle sizer based on laser diffraction. Particle size and concentration distribution characteristics of helically coiled tube two-phase flow and the effect of secondary flow on phase separation were analyzed based on experimental data.     

Effect of a curved duct upstream on performance of small centrifugal compressors for automobile turbochargers

Since the automobile turbochargers are installed in an engine compartment with limited space, the ducts upstream of the turbocharger compressor may be curved in a complex manner. In the present paper, the effect of a curved duct upstream on performance of small centrifugal compressors for automobile turbochargers is discussed. The computational fluid dynamics (CFD) analysis of a turbocharger compressor validated for the compressor model with the straight pipe applied to the compressor with the curved pipe are executed, and the deterioration of the performance for the curved pipe is confirmed. It is also found that the deterioration of compressor performance is caused by the interaction of the secondary flow and the impeller.     

Investigation into the performance of a micro gravitational heat pipe and a micro gravitational heat pipe with artery

The performance of a normal micro gravitational heat pipe was investigated using the analytical and numerical models previously developed. An innovative structure of the heat pipe, i.e. the micro gravitational heat pipe with artery, was then proposed in an attempt to overcome some of the drawbacks of the normal pipe. The thermal behaviour of the new type of heat pipe was simulated, and this was compared with that of a normal micro heat pipe. A performance estimation of both pipes was carried out based on the simulation results. Copyright © 2002 John Wiley & Sons, Ltd.     

Vibration analysis of a 3-dimensional piping system conveying fluid by wave approach

Vibration analysis of a piping system conveying fluid is investigated by employing the wave approach. In this paper, the inviscid fluid-dynamic forces acting on a pipe due to internal fluid flow are approximated by the plug-flow model with the slender-body theory. The straight pipe elements conveying fluid are formulated using a dynamic stiffness matrix in the frequency domain. The curved pipe sections are treated with a single curved pipe element utilizing the mixed methodology of the dynamic stiffness method and the transfer matrix method. The present approach is applied to the frequency response analysis of the 3-dimensional piping system conveying fluid which is composed of straight and curved pipe sections and is compared to the results from the finite-element formulations.     

回填钢管管周土压力分布特性研究

目前市政行业广泛采用Spangler理论进行回填钢管的设计,但水利水电行业中钢管规模和运行条件与市政行业存在较大差距,Spangler理论的适用性有待研究。基于有限单元法,考虑管土之间的接触作用,建立回填钢管三维有限元计算模型,计算不同埋设深度、开槽宽度、管道刚度下回填钢管的管周土压力,通过绘制管周土压力分布图研究管周土压力的分布特性及Spangler理论的适用性。结果表明,竖直土压力在回填钢管管顶和管底处有"波谷"产生,在高埋深、小槽宽时尤为明显;此外,回填钢管刚度越大,管顶土压力越接近抛物线分布,管腰处出现的"波谷"越明显。总体而言,Spangler理论一般更适用于埋深小于2m、管道刚度t/D值小于1/120的回填管道,在实际工程回填钢管的设计中要加以判断。     

弯叶片降低损失机理的实验研究

通过三类低展弦比涡轮叶栅气参数的详细测量与壁面（包括上、下端壁与叶片表面）流动显示,研究了叶片弯曲降低能量损失的机理。实验结果表明：在不叶栅几何参数下,叶片弯曲形式的选择取决于叶栅内涡量场与长量场的适量匹配。