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火焰筒内环向多孔径向射流的流场研究 总被引:2,自引:0,他引:2
环向径向射流对燃烧室火焰筒内的流场有着重要的影响。本文采用三雏标准k-£湍流模型详细模拟了燃烧室火焰筒内外的等温流场,给出了火焰筒不同截面位置的轴向速度和径向速度分布。并对数值模拟结果与实验数据进行了比较,结果符合较好,同时还分析了数值模拟结果与实验数据的差异。研究了火焰筒内多孔径向射流的流场特性,并比较了不同环向径向射流流量对火焰筒内流场的影响。研究结果表明:在射流孔附近,火焰筒内轴向速度和径向速度沿径向的梯度增大;而在火焰筒外,轴向速度沿径向的梯度变化不大,径向速度变化较大,但随着流体的流动,火焰筒外径向速度很快趋于均匀。当射流流量增加时,火焰筒内射流孔中心截面的两对称旋涡逐渐增大。 相似文献
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通过实验和数值模拟来研究气体在渐缩微喷管内流动,基于连续介质模型研究了二维微喷管内的流场及推力特性,研究分析了流量和气体入口温度对微喷管流场结构和喷管性能的影响。研究结果表明,随着流量的不断增加,气体稀薄效应相应减小,粘性力对喷管流动的影响降低,边界层逐渐变薄,马赫数不断增大,微喷管的推力大小近似与流量成线性变化,但流量变化对微喷管流场结构影响并不显著。当温度增大时,粘性损失对喷管影响较大,导致边界层变厚,影响了微喷管推进性能,流场马赫数和微喷管推力随温度的升高而下降,说明低温气体有利于提高微喷管的推进性能。 相似文献
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应用大涡模拟方法对一台二冲程发动机缸内冷态湍流流场进行了三维瞬态数值分析。探索缸内流场的速度、压力及温度的变动情况,并与PIV流场测试结果进行了对比。三维模拟的缸压曲线与试验及一维模拟均吻合较好,但在速度概率密度函数方面与试验存在一定差异。模拟结果表明:本文建立的三维模型能够自然再现缸内冷态流动的随机大尺度涡流情况,模型可靠有效。模拟能够较好地反应火花塞位置附近速度随机波动情况,其结果对于后续研究缸内大尺度涡流对燃烧循环变动的影响机理具有一定的指导意义。 相似文献
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采用数值模拟的方法,对在旋转情况下的有弦向出流的梯形扰流柱通道内的三维流场进行了模拟研究。重点研究了在固定出流比的情况下,不同转速对扰流柱通道内的流动情况及端壁平均换热系数的影响。计算结果表明:R_o不为0时,通道内的流场与静止时相比有较大变化,在扰流柱区域内的扰动强度明显增大,流动更加紊乱,在扰流柱区域和无柱区域内均有涡旋现象发生;当Re数一定时,通道的压降和端壁的平均换热系数随着旋转数R_o的增大而增加;旋转对扰流柱通道的压降和端壁换热系数有明显影响,旋转对扰流柱通道流动及换热的影响随通道数Re数的增大而增强。 相似文献
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In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow charact... 相似文献
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《Applied Thermal Engineering》2001,21(5):599-611
To elucidate an excessive erosion damage produced by solid particles in the fourth stage rotor disc of a 110 MW double flow geothermal turbine, a bi-dimensional modelling investigation has been conducted. The study was based on a set of results from a computational model using a Reynolds stress, RSM, turbulence model. The predicted results confirmed characteristic flow conditions that may play a main role in the serious erosion of the fourth stage rotor disc governor side, which has been detected in periodic overhauls. The results show a jet of vapour that hits the disc transition radius surface at velocities around 112 m/s. These conditions are produced by the flow outgoing from the labyrinth seal, which passes through a drastic cross-section reduction in the last seal strip. The flow was then simulated introducing specific changes to the geometry and the grid in order to modify the flow patterns favourably. Actually, the suggested changes have been envisaged indeed to be practically feasible of being implemented. The new results showed that it is possible to reduce the erosion process up to 86% by increasing the distance from the labyrinth seal to the rotor disc, which produces a 38% velocity reduction of the vapour flow in that zone. The design proposed in this work produces a flow pattern of a lower velocity on disc surface together with a modified angle of flow incidence. Furthermore, the proposed design also reduces a recirculating flow at the exit of the last seal strip. Based on these results, an analysis of erosion against velocity demonstrates that the redesigned rotor disc proposed here leads to the duplication of the time period used at present between maintenance repairs. 相似文献
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To control the film thickness of zinc in the process of continuous hot-dip galvanizing,it is known from the earlydays that the gas wiping through an air knife is the most effective one.The gas wiping using in galvanizing proc-ess brings about a problem of splashing from the strip edge for a certain high speed of coating.So,in the presentstudy,the effects of the deflection angle of Coanda nozzle on jet structure and the distribution of impinging pres-sure at the plate surface are investigated numerically and experimentally.In numerical analysis,the governingequations consisted of three-dimensional time dependent full Navier-Stokes equations,standard k-ε turbulencemodel to solve turbulent stress and so on are employed.In experiment,16 channel pressure scanning valve and3-axis auto traversing unit are used to measure the impinging pressure at the strip surface.As a result,it is foundthat the smaller the deflection angle for the same nozzle slit of air knife is,the larger the impinging pressure is.Toreduce the size of separation bubble and to enhance the cutting ability,it is recommendable to use an air knifewith the Coanda nozzle. 相似文献
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3-D temperature and stress distributions of strip in preheating furnace of continuous annealing line
Tei-Chen Chen Chang-Hsien Ho Jia-Ching Lin Li-Wen Wu 《Applied Thermal Engineering》2010,30(8-9):1047-1057
The cold-rolled steel sheets produced by continuous annealing line (CAL) exhibit a significant phenomenon of warping during punching process. The phenomenon of warping is attributed to the non-uniform residual stress of steel strip, which may result from the non-uniform distributions of the temperature and plastic deformation along both the width and thickness of strip when it passes through the rolls in the CAL. In this study, only the distributions of the temperature and thermal stresses of strip in the preheating zone, one of several zones in CAL, are investigated first. Both the thermal and mechanical analyses are performed by using the finite element code ANSYS to investigate the effects of heating conditions in the preheating furnace. The equivalent emission of radiation of the strip corresponding to the complicated furnace environment is evaluated inversely with the aid of strip temperature estimated by energy balance model. Moreover, three-dimensional (3-D) distributions of the temperature and deformation of strip are then iteratively evaluated by the energy and mechanical models due to their coupling effect until a satisfied convergence in numerical solutions is obtained. The results show that the taper rolls tend to introduce a significantly non-uniform distribution of the temperature along the width. This temperature pattern might lead to an unfavorable consequence of enormously non-uniform distribution of stress along the width. 相似文献
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用心形线表征了一种涡轮增压器无叶蜗壳梨形流道横截面轮廓,用有限差分法计算了涡轮增压器蜗壳流场,分析了无叶喷嘴出口气流速度和气流角的分布,经与测量结果比较,两者吻合较好。在此基础上,研究了三种不同蜗壳型线对喷嘴出口速度场的影响。结果表明,C型线蜗壳喷嘴出口的总速度v和气流角α分布均匀,A,B型线蜗壳喷嘴出口的总速度v和气流角α分布不均匀。 相似文献
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机械镀锌是一种在常温常压下利用化学吸附和机械碰撞使金属锌粉沉积在工件表面形成镀层的工艺,与传统的热镀锌、电镀锌相比,具有生产过程能耗低、对环境污染小等优点,是一种清洁低耗镀锌技术。简要介绍机械镀锌工艺及设备,将机械镀锌、热镀锌和电镀锌的性能、特点、环境影响进行了对比,探讨了机械镀锌技术的发展及应用前景。 相似文献
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The present numerical investigation describes the influence of a transverse magnetic field on the heat and mass transfer characteristics of time‐dependent squeezed flow of Prandtl‐Eyring fluid past a horizontal sensor surface. The current physical problem is modeled based on the considered flow configuration. Also, the present problem is analyzed under the influence of Lorentz forces, to explore the impact of a magnetic field on the flow behaviour. The considered physical problem in the present study gives highly nonlinear coupled time‐dependent, two‐dimensional partial differential equations. The governing flow equations are reduced to the system of nonlinear ordinary differential equations by imposing the suitable similarity transformations on the laws of motion. Due to the inadequacy in the analytical methods, the present problem is solved by using the Runge‐Kutta fourth order integration scheme with shooting method. The flow and heat transfer behaviour of various control parameters are studied and presented in terms of graphs and tables. From the current investigation it is noticed that, the increasing magnetic parameter enhances the velocity field and diminishes the temperature profile in the flow region. Also, the magnifying permeable velocity parameter decreases the temperature field. The present similarity solutions are found to be in good agreement with previously published results. 相似文献
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《Applied Thermal Engineering》2014,62(1):1-12
After the heat treatment in continuous annealing line (CAL), the strip always exhibits phenomenon of residual warpage during punching process. This geometric defect is mainly attributed to the residual stress induced in the line and has a close relation with the temperature history of the strip. It becomes more serious for the wider strip and may significantly degrade the quality of the products. The contents of this study are mainly composed of establishing the energy model of the strip and roll to estimate the temperature distributions of the strip and the surface temperature of the roll, estimating the emissivity and equivalent heat transfer coefficient of the strip in each section of CAL, and establishing mechanical model of the strip to evaluate the distributions of contact pressure and residual stress of the strip especially along the width direction. Finally, the longitudinal residual warpage was calculated accordingly by virtual layers method (VLM). It was found that the residual warpage at both sides is larger than the central region. Moreover, the numerical results of strip warpage are well consistent with the experimental data which demonstrates the accuracy and reliability of the proposed method. 相似文献