共查询到20条相似文献,搜索用时 15 毫秒
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燃气轮机透平叶顶区域存在复杂的流动和换热问题,承受很高的热负荷。为了降低透平动叶叶顶温度,在透平叶顶现有结构的基础上提出气膜冷却和气膜+内冷通道冷却两种叶顶冷却方案,并通过流热耦合计算分析冷却升级前后叶顶区域的换热和流动特性。研究发现:叶顶气膜冷却方案可有效降低叶顶温度,特别是叶顶前缘至中弦区域;而气膜+内冷通道冷却方案基于外部气膜冷却,结合内部冷却通道设计,可进一步降低叶顶尾缘的温度;与原型叶片相比,气膜+内部冷气通道的复合冷却设计可以使叶顶尾缘最高温度降低24 K。 相似文献
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考虑气体温度梯度对工质物性及轴承热稳定性的影响,以及润滑气体和多孔介质的传热耦合,在满足Darcy定律条件下三维求解雷诺方程,计算了轴承间隙和多孔介质中气体的压力及温度分布。分析了3个给定供给压力(0.5、0.65和0.8 MPa)、3种轴承偏心率(0.2、0.5、0.8)对轴承的承载能力、偏位角及润滑流量的影响,计算结果表明:在不同的轴偏心率下均存在有一段轴承最佳渗透系数范围,表征该范围承载能力最强;偏心率越大,轴承承载能力越高,最佳渗透系数区间也越明显;轴承压缩数越大承载能力也越高;间隙中温度分布不均匀导致轴承承载能力降低,通过调整压力和偏心率增加介质的润滑流量,及时导出摩擦产生热量降低间隙中气膜温度,可使轴承平衡稳定运行。 相似文献
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ABSTRACTA physics-based computational simulation of the heat transfer characteristics of an insulated gate bipolar transistor (IGBT) developmental inverter is reported. The simulation considers the fluid/thermal multiphysics interactions via a conjugate heat transfer analysis. The fluid phase includes air and liquid coolant; the solid phase, where the heat is conducted, includes various solid materials. Numerical solutions of the heat conduction and convection phenomena in and around the IGBT modules and the inverter, built as a three-dimensional computational model, are sought for by using parallel computing. Comparisons with the available experimental data show a satisfactory agreement of the inverter temperature at three power levels under two different coolant flow rates. Detailed examination of the flow field reveals that the design features of the rectangular coolant flow chamber in the heat sink and the small clearance between the tips of the pin fin and the walls lead to an evenly distributed coolant flow around most of the pin fins. The temperature distributions of the pin fins depend highly on their locations relative to the IGBT modules. The findings from the current study can be useful in future efforts to optimize the thermal performance of IGBT inverters. 相似文献
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针对涡轮叶片尾缘吸力面热应力集中,容易造成叶片尾部烧毁的现象,提出端部冲击扰流柱结构,采用Realizable k-ε湍流模型和增强壁面函数分析涡轮叶片尾缘内部流场和吸力面换热特性,研究不同冲击孔与扰流柱排列方式的影响,揭示端部冲击扰流柱结构的流场与换热机理。研究表明,端部冲击扰流柱结构对于改善吸力面的换热效果要优于中间冲击扰流柱结构,对端壁的换热有显著提高;各表面平均换热系数均随着压比的增大而增大,顺排结构时,冲击孔换热最强,扰流柱换热次之;叉排结构时,冲击孔换热最强,隔板迎风换热次之;近距离冲击,顺排的综合效果优于其它几种结构,而远距离冲击,叉排的综合效果最好,其吸力面温度分布较均匀。 相似文献
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Prediction of surface heating rates is of prime importance for the hypersonic flow regime. Experimental and conventional computational efforts overlook the heat transfer phenomenon in the solid due to the rigid assumptions involved in the solution methodologies. In order to address this fact, conjugate heat transfer (CHT) studies are carried out using various coupling techniques to examine their implementation abilities. Three types of solution methodologies are adopted, namely, decoupled, strongly coupled, and loosely coupled analysis. This study is also focused on looking into the effect of a hypersonic flow field on wall heat flux for a finite thickness insulating cylinder at moderately large time scales. Increase in wall temperature and decrease in surface heat flux have been noticed using strong and loose coupling techniques with an increase in simulation time. Decoupled fluid and solid domain analysis is found to be useful for typical shock tunnel test durations (~1 ms) while investigations with loose coupling techniques are advisable for time scales corresponding to flight testing (~1 s). Efforts are also made to reason the discrimination in prediction of stagnation point heat flux using conventional computational and experimental analysis. 相似文献
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A numerical study of conjugate heat transfer by turbulent natural convection in a room with three different glazed configurations is presented. The room is modeled as a square closed cavity, where the lower wall is adiabatic, the right wall is semitransparent, and the upper and left walls are opaque conductive surfaces. Governing equations of mass, momentum, and energy were solved by the finite volume method with a two equation turbulence model. The results are presented in terms of streamlines, isotherms, heatlines, turbulent viscosity isolines, and thermal parameters, such as indoor temperatures and heat transfer coefficients. From the three cases considered in this study, the reflective glass window was the optimal configuration from the thermal comfort point of view for both design days. On the contrary, the glass-film configuration showed the worst indoor thermal performance inside the cavity despite of being the configuration that allows lower energy transferred into the room through the glazed surface. A set of useful heat transfer correlations are obtained for building design applications and energy codes in temperate climates. 相似文献
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透平叶片尾缘冷却结构唇板构型对流动和传热的影响 总被引:1,自引:0,他引:1
为了提高尾缘冷却效果和降低叶栅气动损失,采用SST k-ω模型研究简化的压力面射流冷却结构唇板构型对冷却效果的影响。结果表明:唇板改型可以提高射流出口段的传热强度,但会增大气动损失;在研究范围内抬升一倍下板尾部边界层厚度时综合效果最佳;速比0.5和1.0时,原型的射流出流后向上抬升,在下板表面附近产生低速区,降低当地传热强度;速比0.5时,原型下板尾缘出现分离区,并与板后的回流区发生掺混,改型结构增强射流刚性,分离点后移;改型结构在不同速比下的传热系数均有所增强,平均传热系数在3个速比下分别提高了26.31%、34.72%和15.33%,其中速比1.0的综合传热因子最高,传热系数增加的幅值最大,且总压损失增加不显著。 相似文献
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To enhance specific power output and thermal efficiency of gas turbine engines, industry searches for ways to increase the turbine inlet temperatures. Therefore, temperatures of turbine blades increase as well and necessitate active cooling of these components. Experimental design work on such internal cooling schemes is carried out to find acceptable compromises between heat transfer and pressure losses. It is often carried out by using transient thermochromic liquid crystal techniques in combination with Plexiglas models. However, for real turbine blades this experimental technique is inappropriate due to the lack of optical access. Therefore, to study actual turbine blades there is need for development of noninvasive, nondestructive methodologies. This article describes a measurement technique that allows determination of internal heat transfer coefficients of real turbine blades experimentally. Thus, a test rig with a rapidly responding heater was designed to fulfill the requirement of a sudden increase in the air temperature within the cooling passages. The outer surface temperatures were measured using infrared thermography. To estimate the spatial distribution of internal heat transfer coefficients from transient surface temperatures the inverse heat transfer problem was solved. As optimization algorithm the Levenberg–Marquardt method was chosen. Outer surface temperature data was measured for a rectangular reference model with rib turbulators and compared with simultaneously acquired data using the thermochromic liquid crystal technique. It is concluded that the new experimental measurement technique could be used to quantitatively determine internal heat transfer coefficients. 相似文献
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在热冲击与脉动热流边界条件下,应用数值方法求解一维非傅立叶导热方程,分析双层结构热障涂层内的一维非定常传热特性。计算模型引入壁面曲率修正,考虑了涡轮叶片表面的型线曲率影响。分析结果表明:涂层材料热松弛时间的长短是瞬态传热特性的决定因素。边界受瞬态冲击热流条件下,涂层内的温度分布在10倍的松弛时间后达到平衡分布。边界热流脉动周期与松弛时间相当时,涂层内热流出现了波状传输,热障涂层内的温度呈波状分布。非傅立叶导热方程预测的温度交变厚度大于抛物型方程预测的厚度,显示了高频热流作用下,涂层材料可能发生疲劳破坏。叶片表面的的凸形曲率以指数率形式,增强了涂层内温度波幅度,解释了叶片前缘等处涂层易出现裂纹的现象。 相似文献
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R. W. GRAHAM 《传热工程》2013,34(1):39-47
The quest for improved efficiency has motivated the elevation of turbine inlet temperatures in all types of advanced aircraft gas turbines. The accommodation of higher gas temperatures necessitates complex blade cooling schemes so as not to sacrifice structural integrity and operational life in advanced engine designs. Estimates of the heat transfer from the gas to stationary (vanes) or rotating blades poses a major uncertainty because of the complexity of the heat transfer processes. The gas flow through these blade rows is three-dimensional with complex secondary viscous flow patterns that interact with the end walls and blade surfaces. In addition, upstream disturbances, stagnation flow, curvature effects, and flow acceleration complicate the thermal transport mechanisms in the boundary layers. Some of these fundamental heat transfer effects will be discussed. The chief purpose of this paper is to acquaint those in the heat transfer community, who are not directly involved in gas turbines, with the seriousness of the problem and to recommend some basic research that would improve the predictions of gas-side heat transfer on turbine blades and vanes. 相似文献
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For the conjugate heat transfer simulation, two-equation turbulence models will predict an anomalously large growth of turbulent kinetic energy in high strain rate flows, and then the flow and heat transfer will be unreasonable. The current study improved the low Reynolds number Chien k-? two-equation model using the “realizability” based C μ limiter and the production term P k limiter. This study was conducted based on a developed preconditioned density-based conjugate heat transfer algorithm. Calculations are presented for the flat plate turbulence flow and the conjugate heat transfer of the MarkII cooling turbine blade using the improved model. The results were analyzed and compared with semi-empirical formula and experimental data. Significant improvement in the turbulent kinetic energy anomaly was obtained using both limiters. The prediction accuracy of the Chien k-? model for the flow and heat transfer in the conjugate heat transfer simulation was significantly enhanced. The changes in the model are guaranteed to not have unfavorable influence on the simulation of low strain rate flows. 相似文献