共查询到20条相似文献,搜索用时 109 毫秒
1.
为了将计算渗流自由面的弃单元法应用于ANSYS软件中,对其进行了改进,即根据每次迭代计算结果,将节点全部位于自由面以上的单元均删掉,从而使得总体传导矩阵的阶数不断降低,计算效率得到提高。在计算复合单元等效渗透系数时,对复合单元进行二次细分,以减小单元尺寸对计算结果的影响。计算收敛后,对复合单元上的节点插值求出零压头点坐标,再对零压头点进行曲线拟合或曲面拟合即得自由面。基于该方法,利用ANSYS的APDL语言编制了渗流自由面分析程序,并进行了实例分析。结果表明,提出的改进方法结构简单、精度较高。 相似文献
2.
3.
4.
燃气轮机空气冷却系统建模及计算分析 总被引:1,自引:0,他引:1
本文以某型燃气轮机透平叶片的空气冷却系统为研究对象。在分析叶片的内部冷却方式、结构及冷却空气流路构成的基础上,将空气冷却系统模化为由大量不同的通流单元以串连或分支方式组成的复杂网络系统。选用适当的经验关系式或试验关联式计算空气流经各通流单元的压力损失与换热量,建立了描述冷却空气流动与换热特性的流量方程组、压力方程组和温度方程组。采用逐步简化空气冷却系统的方式,求解空气冷却系统内流量的分配。采用以改进并修正的高斯消去法为基础的一种稳定的大型稀疏矩阵线性方程组解法来求解空气冷却系统内空气的压力与温度分布。可以计算得到各流路的压力、温度和流量的分布等参数。 相似文献
5.
无收益水量的合理分配对管网模型计算精度影响较大。为了尽可能真实地反映节点实际用水量,基于供水管网的一致漏损模型,将无收益水量分为真实漏损和表观漏损两部分,在原有管长影响因素的基础上增加考虑了压力及流量,提出了漏失模型法的流量分配方法,并以天津市H区给水管网模型为例进行了计算验证。结果表明,对于沿线流量分配法与漏失模型法两种流量分配方法,其压力监测点处的模拟值在每个时刻与实测值的误差均在±2m之内;二者水力计算所得的节点压力相差约0.2m,漏失模型法的流量分配结果明显更靠近监测点的实测值,精度较高。 相似文献
6.
在汽轮机通流部分流量的计算占有很重要的作用,而公式中流量系数是一个非常关键的参数,流量系数对流量的精确度影响很大。文中针对传统流量公式中流量系数与速度系数之间关系的不准确性,对两者之间的关系进行了修正,使流量系数和速度系数的求解更加细化,通过推导找出了一个修正系数,使二者关系得到了改进,使得流量的求解值更加精确。 相似文献
7.
张刚 《电网与水力发电进展》2011,27(3):81-84
流量节点图在引水式水电站开发环评影响分析中应用较多,它能直观反映出由于水电站引水(或者调水)造成的减脱水段多年平均流量的变化情况。引用"佛坪县金水河流域梯级电站规划环评",浅析了流量节点图在环评影响分析中的应用。 相似文献
8.
9.
川西气田老区进入生产末期,气井产能效益已经非常低,长期以来气田井场管理采用人员巡检抄表值守模式,存在明显的资源管理浪费问题。如今,信息化技术应用已成为降低气田生产成本的有效途径,但气田老区井场工艺单元的全信息化改造面临较高的投资和成本回收风险。为此,本文选取了川西气田下属的SF采气管理区,其低压低产的特点可代表绝大多数川西气田老区的生产情况,通过精简井场工艺的数据源点、改进流量计算方式以及现场应用试验,探索川西气田老区的信息化建设模式。研究结果表明在川西气田老区井场工艺单元中,压力、液位、熄火保护数据源点具备精简空间,经优化精简后数据源点减少率超过50%;测温、测压上传RTU计算流量的数据结果满足气田内部的计量需求,且较常规一体化流量积算仪方式节省1.9万元/计量点。因此,采取精简化数据采集设备和RTU流量计算模式具备经济上、技术上的可行性,为川西气田老区整体信息化建设指明了方向。 相似文献
10.
11.
阵列射流冲击冷却换热特性的数值研究 总被引:1,自引:0,他引:1
运用数值计算的方法对不同流动取向的多排孔冲击射流冷却特性进行了三维模拟,并对有初始横向流的多排孔冲击射流冷却特性进行了数值研究,揭示出射流雷诺数、流动方向、初始横向流对冲击冷却传热特性的影响规律。结果表明:研究范围内,射流雷诺数越大,冲击靶面换热效果越好;冲击腔室两端都设为出口时努赛尔数峰值所对应的射流驻点区向下游偏移最小且换热效果最好;当横流雷诺数与射流雷诺数之比大于0.5之后,有横流时的冲击射流冷却局部努赛尔数比无横流时有较为显著下降。 相似文献
12.
Temperature distribution and variation with time has been considered in the analysis of the influences of the initial level of immersion of a horizontal metallic mesh tube in the liquid on combined buoyant and thermo-capillary flow. The combined flow occurs along with the rising liquid film flow on the surface of a horizontal metallic mesh tube. Three different levels of immersion of the metallic mesh tube in the liquid have been tested. Experiments of 60 min in duration have been performed using a heating metallic tube with a diameter of 25 mm and a length of 110 mm, sealed outside with a metallic mesh of 178 mm by 178 mm, and distilled water. These reveal two distinct flow patterns. Thermocouples and infrared thermal imager are utilized to measure the temperature. The level of the liquid free surface relative to the lower edge of the tube is measured as angle q. The results show that for a smaller q angle, or a low level of immersion, with a relatively low heating power, it is possible to near fully combine the upwards buoyant flow with the rising liquid film flow. In this case, the liquid is heated only in the vicinity of the tube, while the liquid away from the flow region experiences small changes in temperature and the system approaches steady conditions. For larger q angles, or higher levels of immersion, a different flow pattern is noticed on the liquid free surface and identified as the thermo-capillary (Marangoni) flow. The rising liquid film is also present. The higher levels of immersion cause a high temperature gradient in the liquid free surface region and promote thermal stratification; therefore the system could not approach steady conditions. 相似文献
13.
F.M. Ali R. Nazar N.M. Arifin A. Ishak I. Pop 《International Communications in Heat and Mass Transfer》2010
In this paper, the problem of unsteady uniform flow across a stretching surface in an arbitrary direction is studied theoretically, where the unsteadiness is caused by the impulsive motion of the stretching surface. Numerical results of the governing partial differential equations are obtained using an implicit finite-difference scheme for the whole transient from the early or initial unsteady-state flow to the final steady-state flow. The early unsteady-state flow is solved analytically. The numerical solution obtained for the reduced skin friction coefficient is compared with previously reported results and the results for velocity profiles, h and g profiles are also presented in this paper. It is found that there is a smooth transition from the small-time solution (initial unsteady flow) to the large-time solution (final steady-state flow). 相似文献
14.
You-Rong Li Xiao-Jun Quan Nobuyuki Imaishi Dan-Ling Zeng 《International Journal of Heat and Mass Transfer》2005,48(10):1952-1960
In order to understand the characteristics of surface patterns on silicon melt in Czochralski furnaces, we conducted a series of unsteady three-dimensional numerical simulations of thermocapillary-buoyancy flow of a shallow molten silicon pool with Czochralski configuration (depth d = 3 mm). The crucible sidewall is maintained at constant temperature. Bottom and free surfaces are adiabatic or allow heat transfer in the vertical direction. The simulation results indicate that two flow transitions occur with increasing the radial temperature difference along the free surface. At first, the steady two-dimensional flow becomes steady three-dimensional flow and then oscillatory three-dimensional flow. The critical conditions for the onset of the instability were determined. Characteristics of the steady and the oscillatory three-dimensional flows were discussed. 相似文献
15.
This paper presents a numerical simulation method developed for separated flow in cascades using the Eulerequations and demonstrates the feasibility of this method.MacCormack's two-steps explicit finite differencescheme is used to discretize the equations in conservation form,and the artificial viscosity is added to the dis-cretized inviscid equations by means of the self-adapted filter technique.The initial separation boundary is givenaccording to simple experimental results.The numerical simulation results including subsonic and transonicturbine cascades flow with or without separation show that the fundamental idea of this numerical method isreasonable and simple.The present study indicates that for solving certain engineering problems it is a simpleand effective tool for adding some viscosity corrections to inviscid flow model,especially the current when theNavier-Stokes equations have not been solved very effectively for various complicated flows in turbomachinery. 相似文献
16.
17.
Experimental and numerical investigation of tip vortex generation and evolution on horizontal axis wind turbines 总被引:1,自引:0,他引:1 下载免费PDF全文
The tip vortex of a wind turbine rotor blade is the result of a distribution of aerodynamic loads and circulation over the blade tip. The current knowledge on the generation of the tip vorticity in a 3D rotating environment still lacks detailed experimental evidence, particularly for yawed flow. The aim of this paper is to investigate how circulation at the blade tip behaves and how vorticity is eventually released in the wake, for both axial and 30° yawed flow conditions through the combination of experimental and numerical simulations. Stereo particle image velocimetry is used to measure the flow field at the tip of a 2m diameter, two‐bladed rotor at the TU Delft Open Jet Facility, for both axial and yawed flow; numerical simulations of the experiments are performed using a 3D, unsteady potential flow free‐wake vortex model. The generation mechanisms of the tip vorticity are established. The spanwise circulation along the blade exhibits a similar variation in both axial and yaw cases. A comparison of the chordwise directed circulation variation along the chord between axial and yawed flow is also presented and shown to be different. The analysis is based on contour integration of the velocity field. The tip vortex trajectory for axial flow confirms previous observations on the MEXICO rotor. The experimental results for yawed conditions have clearly shown how vorticity is swept radially away from the blade under the influence of the in‐plane radial component of flow. Such phenomena were only partially captured by the numerical model. The results of this work have important implications on the modelling of blade tip corrections. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
19.
To improve the aerodynamic performance of small axial flow fan, in this paper the design of a small axial flow fan with splitter blades is studied. The RNG k-ε turbulence model and SIMPLE algorithm were applied to the steady simulation calculation of the flow field, and its result was used as the initial field of the large eddy simulation to calculate the unsteady pressure field. The FW-H noise model was adopted to predict aerodynamic noise in the six monitoring points. Fast Fourier transform algorithm was applied to process the pressure signal. Experiment of noise testing was done to further investigate the aerodynamic noise of fans. And then the results obtained from the numerical simulation and experiment were described and analyzed. The results show that the static characteristics of small axial fan with splitter blades are similar with the prototype fan, and the static characteristics are improved within a certain range of flux. The power spectral density at the six monitoring points of small axial flow fan with splitter blades have decreased to some extent. The experimental results show sound pressure level of new fan has reduced in most frequency bands by comparing with prototype fan. The research results will provide a proof for parameter optimization and noise prediction of small axial flow fans with high performance. 相似文献