共查询到19条相似文献,搜索用时 140 毫秒
1.
针对航空涡轮叶片的温度场预测问题,采用CFD(computational fluid dynamics)软件和有限元计算理论与方法,以对流冷却叶片的温度场与热应力求解为例,分别计算了涡轮进口温度均匀和不均匀时叶片的温度场和热应力,分析了涡轮进口温度不均匀对叶片热应力的影响,其中叶片温度场的求解采用气热耦合的方法即直接应用CFD软件计算叶片温度场,再依据温度场进行了有限元热应力分析.结果表明,进口温度不均匀时比进口温度均匀时叶片的热应力增大10%左右. 相似文献
2.
3.
核电汽轮机高压缸三维有限元热应力分析 总被引:1,自引:0,他引:1
在变工况时,核电汽轮机的汽缸表面温度随蒸汽温度快速变化,引起汽缸内部大的温差与热应力;在稳态条件下,汽缸大压差截面处也存在大的温差与热应力。文中着重介绍核电汽轮机高压缸的热应力计算和分析,考虑了中分面的密封分析,计算了冷态起动,加负荷、稳态和甩负荷过程中的瞬态非线性温度场,然后以材料非线性模式求解相应的热应力场。 相似文献
4.
5.
现在对汽轮机热应力的实时计算方法均是采用解析方法,由于解析方法是对转子轴对称二维热传导方程的简化,给热应力的计算带来了误差,应用有限元的中间计算结果,应用Hopfield神经网络的方法,实现有限元计算中热应力整体刚度矩阵代数方程组的快速求解,仿真结果表明,该方法是有效的。 相似文献
6.
本文记录了先进的计算流体动力学(简称CFD)技术在高效率汽轮机设计中的应用,计算方法是通过强词经典的型线设计和一般的汽轮机设计方面,如整个通道的应力分析及几何特性的相互关系来描述的。该方法用于典型的汽轮机设计案例,即汽轮机多级全三维流场、叶片汽封和排汽缸的计算。CFD对设计过程的支持体现在:对复杂的流动特性提供更深入的物理认识,并为进一步研究和优化提供目标。通过比较计算结果和试验结果,评定了目前技术水平下CFD的预测能力。计算结果和试验结果取得很好的一致。还对由结构化网格和非结构化网格计算所得结果进行了相互比较,不仅证明了两者极好的一致性,而且示范了采用非结构网格的CFD软件模化复杂几何形状的特殊能力。总之,发现了CFD方法具备预测现代汽轮机组中发生的复杂三维粘性流动的能力,从而在整体上获得对流体动力机械更好的理解。性能进行预测,并对流场的总体动力特性有更好的了解。因此,先进的CFD技术是西门子发电集团设计高效率汽轮机的一个基本工具。 相似文献
7.
8.
9.
10.
11.
This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (1D) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler 1D analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no ‘or negligible’ temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the 1D isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of events adopts a 1D heat flow that reassembles the conditions of the 1D simple model (for the assessed USC duct geometry); 1D heat flow through the top and bottom fins/sheets as the duct wall reassembles a state of adiabatic condition. 相似文献
12.
以NREL Phase VI风力机为研究对象,对低雷诺数下叶片三维效应翼型气动参数修正进行研究。通过三维CFD数值模拟与二维翼型风洞实验,比较和检验现有的Snel、Lindenburg、Du&Selig、Chaviaropoulos&Hansen这4种修正公式。结果显示修正效果明显不同,以Du&Selig修正公式效果最佳,但它在叶尖和叶根部位的修正误差较大,而且随着尖速比的减小,叶片上的修正值与三维CFD结果吻合的区域减小,尤其不适合负攻角流动的修正。 相似文献
13.
14.
The heat transfer characteristics and flow behavior in a rectangular passage with two opposite 45° skewed ribs for turbine rotor blade have been investigated for Reynolds numbers from 7800 to 19,000. In this blade, the spanwise coolant passage at the trailing edge region whose thickness is very thin is chosen, so the channel aspect ratio (=width/height of channel) is extremely high, 4.76. Therefore the heat transfer experiment in the high‐aspect‐ratio cooling channel was performed using thermochromic liquid crystal and thermocouples. Furthermore, the calculation of flow and heat transfer was carried out using CFD analysis code to understand the heat transfer experimental results. The enhanced heat transfer coefficients on the smooth side wall at the rib's leading end were the same level as those on the rib‐roughened walls. © 2002 Scripta Technica, Heat Trans Asian Res, 31(2): 89–104, 2002; DOI 10.1002/htj.10018 相似文献
15.
Transcritical carbon dioxide (CO2) Rankine cycle has exhibited great potential in the field of low-temperature heat utilization. But its application is restricted by the condensing issue and the safety concern due to the relatively low critical temperature and high critical pressure of CO2. Blending CO2 with organic fluids for the transcritical Rankine cycle is regarded as an effective method to solve these problems. And the turbine performance has great influence on the performance of transcritical Rankine cycle. In this paper, the thermal design of the CO2-based mixture turbine is firstly carried out based on the parametric optimization of the system. Then the computational fluid dynamics (CFD) analysis is performed to examine the turbine performance and validate the reliability of thermal design. Furthermore, the effects of blade tip clearance and nozzle-to-rotor clearance on the turbine performance are investigated. Results show that the turbine is well designed with an isentropic efficiency of 84.54%, and the CFD simulation results basically agree with the thermal design results. The influence of leakage flow on mainstream grows significantly as the blade tip clearance increases. When the blade tip clearance is 2 mm, the relative loss of power output could achieve as large as 7.81%. Larger nozzle-to-rotor clearance leads to more uniform distributions of Mach number and pressure, but the flow losses also increase. The effect of trailing edge disturbance on the flow field at the nozzle outlet is almost negligible if the nozzle-to-rotor clearance is 6 mm or more. 相似文献
16.
Jiancong Dong Tuo Zhou Xiaojiang Wu Jian Zhang Haojie Fan Zhongxiao Zhang 《热科学学报(英文版)》2018,27(6):592-601
This paper presented a coupled heat transfer model combining the combustion in the furnace and the ultra-supercritical(USC) heat transfer in the water wall tubes. The thermal analysis of the spiral water wall in a 1000 MW double reheat USC boiler was conducted by the coupled heat transfer simulations. The simulation results show that there are two peak heat flux regions on each wall of spiral water wall, where the primary combustion zone and burnt-out zone locate respectively. In the full load condition, the maximal heat flux of the primary combustion zone is close to 500 kW/m~2, which is higher than that in the conventional single reheat USC boilers. The heat flux along the furnace width presents a parabolic shape that the values in the furnace center are much higher than that in the corner regions. The distribution of water wall temperature has a perfect accordance with the heat flux distribution of the parabolic shape curves, which can illustrate the distribution of water wall temperature is mainly determined by heat flux on the water wall. The maximal water wall temperature occurs at the middle width of furnace wall and approaches 530°C, which can be allowed by the metal material of water wall tube 12Cr1MoVG. In the primary combustion zone, the wall temperatures in half load are almost close to the values in 75% load condition, caused by the heat transfer deterioration of the subcritical pressure fluid under the high heat flux condition. The simulation results in this study are beneficial to the better design and operational optimization for the double reheat USC boilers. 相似文献
17.
采用流固耦合方法对燃气轮机高温涡轮叶片旋流冷却结构进行数值模拟分析。探究了不同冷气/燃气温度比条件下旋流冷却的流动与传热特性、叶片前缘区域固体温度、热应力以及热应变分布。研究表明:在进气腔入口雷诺数固定的条件下,随着温度比升高,冷气密度降低,冷气流速逐渐提升,同时湍动能升高,靶面努塞尔数逐渐升高;当温度比较低时冷气的流速较低、单位时间冷气带走的热量较少,当温度比较高时冷气温度较高、单位质量冷气所能吸收的热量有限,靶面处热流密度先升高后降低。受靶面热流密度分布影响,随着温度比升高,叶片前缘固体的温度、热应力以及热应变先降低后升高。 相似文献
18.
This paper describes a transient cooling technology for electronic equipments using phase-change material (PCM). The module is made of low-cost materials, yet it is designed to achieve a reasonably high level of heat transfer performance. Paraffin is used as the PCM. In previous our report, we can estimate the cooling performance of PCM by using a thermal network method, which cannot calculate melted PCM flow. In this paper, we consider the heat transfer phenomena of PCM module more deeply by using computational fluid dynamics (CFD) analysis with an enthalpy porosity method. By using this method, we can calculate phase-change phenomena and flow phenomena of melted PCM with CFD analysis. First, we briefly explain the results of the experiment and the thermal network analysis. Then we describe the details of CFD analysis with the enthalpy porosity method. In this calculation, melted PCM flow and heat absorption of latent heat can be analyzed. Therefore, we can discuss the reason why the thermal network analysis can estimate cooling performance of PCM module without dealing with melted PCM flow. The calculation results showed that natural convective flow of melted PCM affects the cooling performance of the PCM module. In the case where the PCM module is set vertically, high temperature and low temperature locations exist on the substrate. If several devices are cooled with the PCM module, device consuming the most power must be set in the lower part of the PCM module. From these results, we can conclude that no natural convective flow occurs in our experiment due to the shape of the PCM module. 相似文献
19.
The aeroelastic response and the airloads of horizontal-axis wind turbine rotor blades were numerically investigated using a coupled CFD–CSD method. The blade aerodynamic loads were obtained from a Navier–Stokes CFD flow solver based on unstructured meshes. The blade elastic deformation was calculated using a FEM-based CSD solver which employs a nonlinear coupled flap-lag-torsion beam theory. The coupling of the CFD and CSD solvers was accomplished in a loosely coupled manner by exchanging the information between the two solvers at infrequent intervals. At first, the present coupled CFD–CSD method was applied to the NREL 5MW reference wind turbine rotor under steady axial flow conditions, and the mean rotor loads and the static blade deformation were compared with other predicted results. Then, the unsteady blade aerodynamic loads and the dynamic blade response due to rotor shaft tilt and tower interference were investigated, along with the influence of the gravitational force. It was found that due to the aeroelastic blade deformation, the blade aerodynamic loads are significantly reduced, and the unsteady dynamic load behaviors are also changed, particularly by the torsional deformation. From the observation of the tower interference, it was also found that the aerodynamic loads are abruptly reduced as the blades pass by the tower, resulting in oscillatory blade deformation and vibratory loads, particularly in the flapwise direction. 相似文献