燃烧室出口辐射对气膜冷却传热影响研究

燃气轮机高温透平中包含对流/导热/辐射等复杂传热现象。本文依托高温流热固耦合实验台,提出燃烧室与透平联合计算的方法,采用数值模拟和实验对比的方式分析了平板气膜冷却的对流/导热/辐射传热特性。同时研究了不同燃气吸收系数以及不同进口辐射条件对于平板气膜冷却的表面温度分布的影响。结果表明:辐射传热是燃气轮机首级高温叶片传热特性的重要影响因素,辐射传热使得实验平板温度抬升50～70 K,燃烧室/透平联合计算方法有效地分析了燃烧室出口辐射强度对高温平板气膜冷却辐射传热的影响;高温燃气辐射特性对于平板温度分布具有明显影响。     

高温透平气热耦合通流设计与分析

透平冷却技术的广泛应用带来了冷却透平中主流流动和传热过程的复杂耦合问题。传统透平设计过程中,通常将气动设计与冷却设计分开进行,因而难以充分考虑二者之间的相互影响。本文在某高温轴流透平的初步设计中采用了一种气热耦合的通流设计方法,该方法在传统通流计算的基础上引入了冷却计算模型,并以通流计算得到的主流流场参数作为传热计算的边界条件,由此求得透平所需冷气量及主流流场参数。本文采用ANSYS CFX对设计透平进行了性能分析,结果表明该气热耦合通流设计方法可以在透平初步设计阶段提供较大的借鉴意义。     

基于流网分析的通流计算冷却模型

伴随着复合冷却技术的广泛应用,冷却透平中主流流动和传热过程的复杂耦合现象日趋显著,有必要在初步气动设计阶段充分考虑冷却对主流气动布局的影响。本文基于流网分析提出了适用于气热耦合通流方法的冷却模型,该模型可针对透平叶片进行快速流热分析,并结合主流气动参数计算结果预测掺混冷气流量分布及掺混损失分布。本文采用该冷却模型对C3X叶型进行了气热耦合通流分析,叶片表面温度分布计算值与实验结果符合良好,说明该冷却模型可应用于气热耦合通流方法,为透平初步气动设计及冷却设计提供一定的借鉴意义。     

高温多组分工况下气膜冷却及TBCs传热特性

煤基联合循环电站系统的燃气轮机透平将会工作在高温高湿的环境中。文中基于高温多组分气膜冷却试验台,分析在高温气膜冷却系统中导热/对流/辐射多场耦合作用机理.研究表明,高温环境下辐射作用不可忽略,不同的高温气体组分将对透平传热产生影响;随着主流高温燃气中水蒸气和二氧化碳体积分数之和每增加7%,平板上表面中心线总体冷却效率降低约0.02;TBCs在各组分工况下都有明显的温降效果,且燃气的水蒸气含量越高,温降效果越明显。由于辐射在高温高湿工况下的综合作用,在透平的设计中必须综合考虑不同燃气组分在导热/对流/辐射耦合作用下的气膜冷却传热机理。     

燃机叶片平行肋扰流内冷通道传热特性研究Part2:耦合传热特性

平行肋扰流通道是高温透平叶片常用的冷却结构。本文通过批量(约1000次)的气热耦合数值计算对不同几何结构平行肋扰流冷却通道的流动与耦合传热特性进行研究.对于固定压差通道,存在使固体外壁温度最低的肋片布置形式及对应的最优冷气量,针对某重型燃机动叶设计了不同肋片角度的平行肋扰流冷却通道并进行了气热耦合数值计算,表明60°肋能在最小的冷气量下取得最强的换热,验证了机理研究的结论.     

燃气透平叶片表面颗粒沉积特性数值研究进展

污染物颗粒在燃气透平叶片表面及冷却通道内的沉积将影响透平叶片的冷却特性和安全服役寿命。国外许多研究机构对燃气透平叶片表面污染物颗粒沉积特性及其与叶片气膜冷却的相互作用机制进行了持续研究。本文首次系统总结了近年来燃气透平叶片表面污染物颗粒沉积特性数值研究进展,重点介绍了燃气透平叶栅流道内污染物颗粒的沉积机制、颗粒沉积和脱离物理模型以及颗粒沉积与透平叶片冷却特性相互作用的数值模拟方法和研究成果。基于当前研究热点和发展趋势,结合作者的研究经历,指出了国内在研发先进燃气轮机透平冷却结构时应注意的问题和方向,为高效、燃料适应性更广的燃气轮机技术自主开发奠定基础。     

压气机级间抽气的数值模拟

燃气轮机的压气机抽气配管是燃气轮机设计以及运行使用中的一个重要环节,是一组连接燃气轮机压气机和透平的通流部件.它从压气机的某几级中抽取一部分压缩气体通入透平或其后排气通道.本文通过数值模拟的方法研究了压气机抽气级的流动特性,考察了抽气流量和抽气槽角度对压气机主流流场的影响.     

燃气轮机一级透平动静叶交互作用的气膜非定常特性及泛冷却效应:Part 1-静叶栅

采用三维非定常数值模拟计算某重型燃气轮机第一级透平的全气膜冷却特性,探讨级环境下静叶表面与静叶端壁及动叶表面与动叶平台的气膜非定常特性及泛冷却效应。燃气轮机泛冷却是指燃气轮机透平冷却气体出流在非设计位置所引起的附加效果。该部分工作包含两部分内容,其中第一部分关注级环境下静叶全气膜及燃烧室与静叶间的环缝密封出流在静叶端壁上的气膜覆盖,以及环缝密封出流在下游静叶栅中所形成的泛冷却效应。结果表明,在时均来流条件下,静叶表面及端壁气膜冷却效率分布非定常特征并不明显;燃烧室与静叶环缝密封出流在端壁上形成气膜覆盖,同时在静叶吸力面轴向Z/C>0.5和叶高S/H<10%区域形成泛冷却效应,且泛冷却效率随着环缝密封流量的增大而呈指数关系快速上升,设计工况下最大泛冷却效率达0.11。     

带肋通道和气膜冷却交互下的绝热和耦合传热研究

燃气轮机透平叶片冷却中,内部肋片扰流对气膜冷却效果有显著影响,当边界条件为金属壁面绝热和金属壁面耦合时,冷却效率会有不同的表现。本文采用数值计算方法,分别计算绝热边界和耦合边界条件下,气膜孔进口与内部冷却扰流肋片不同相对位置条件下的绝热气膜冷却效率和耦合条件下的整体冷却效率进行计算。结果表明当气膜进口位于肋后扰流区时,绝热气膜冷却效率较差。绝热边界和耦合边界条件下流场相似,气膜孔与肋片相对位置对于气膜孔下游整体冷却效率的影响与绝热条件相似。     

PG9351FA燃机建模及改烧合成气的通流调整分析

在透平冷却空气量估算的基础上,建立了透平逐级计算、考虑IGV角度对压气机特性曲线影响的PG9351FA燃机变工况模型.针对改烧合成气带来的压气机喘振、通流匹配等问题,分析了关小IGV角度、增大透平通流面积、降低燃气轮机T3温度等几种不同的通流调整措施对燃气轮机最大出力、压气机喘振裕度以及燃气轮机整体性能的影响,提出了一...     

振荡流共轭换热格子——Boltzmann模拟

振荡流共轭换热现象广泛存在于热声热机等工程应用中.基于双分布格子-Boltzmann模型,对平行平板间振荡流共轭换热进行了数值模拟.通过假定共轭界面处流体和固体的未知内能分布函数均为对应的平衡态滑移修正格式,提出了一种处理共轭换热边界的新方法.模拟结果表明,该方法可以保证共轭界面上温度连续和热流连续.分析了不同流体与固体导热系数比情况下振荡流共轭换热的速度场、温度场以及热流分布的特点.     

耦合传热和冷却流通道流动对气膜冷却的影响

本文通过数值模拟的方法同时考虑了耦合传热和冷却流通道流动对气膜冷却的影响.计算结果表明,在考虑耦合传热的情况下,冷却流通道流动的影响仍然存在,但随着壁面导热系数的增大,这种影响减弱;同时在考虑耦合传热的情况下,受保护壁面温度场分布更加均匀,冷却效果更好.计算结果还表明吹风比为0.5时的冷却效果优于吹风比为1.0的情况.     

基于辐射光谱法的高温颗粒辐射传热参数在线测量方法研究

针对在高温燃烧环境中的颗粒辐射传热问题,基于普朗克辐射定律,提出了用于高温颗粒辐射传热参数在线测量的辐射光谱法,根据高温颗粒可见波段辐射光谱随波长变化情况,通过参数拟合方法直接获得颗粒温度及辐射强度等辐射传热参数。为验证该方法测量准确性,搭建了高温黑体炉辐射测量系统,实验测量结果显示：温度测量值与设定温度相对偏差小于3%;辐射强度测量值与理论计算值相对偏差小于5%。以此为基础,设计了应用于高温燃烧环境下的颗粒辐射传热参数测量的水冷结构探针,并利用该探针开展了高温燃烧环境气固两相流200～1 100 nm波段辐射光谱测量,基于上述方法,直接获得了高温颗粒温度、辐射强度等辐射传热参数沿截面分布情况,有效剥离了高温气体对流传热的影响,为高温颗粒辐射传热研究提供数据支撑。     

Modeling of complex flows and heat transfer

This paper presents the numerical modeling of complex flows and heat transfer. The Finite Analytic method is used to discretize the transport equations. The diagonal Cartesian method is proposed to model fluid flows and heat transfer over complex geometries. A three-dimensional channel flow with conjugate heat transfer is simulated. By the diagonal Cartesian method and 5-point Finite Analytic scheme, a grooved channel flow and flow in a casting bank at different Reynolds numbers are modeled. Simulations by both the diagonal Cartesian method and the traditional saw-tooth Cartesian method indicates the diagonal Cartesian method improves the modeling of flows, due to the more accurate approximation of complex boundaries. Heat transfer in two-dimensional finned compact heat exchanger is also studied. An improved heat exchanger is proposed based on the numerical prediction of heat transfer.     

A composite grid solver for conjugate heat transfer in fluid–structure systems

We describe a numerical method for modeling temperature-dependent fluid flow coupled to heat transfer in solids. This approach to conjugate heat transfer can be used to compute transient and steady state solutions to a wide range of fluid–solid systems in complex two- and three-dimensional geometry. Fluids are modeled with the temperature-dependent incompressible Navier–Stokes equations using the Boussinesq approximation. Solids with heat transfer are modeled with the heat equation. Appropriate interface equations are applied to couple the solutions across different domains. The computational region is divided into a number of sub-domains corresponding to fluid domains and solid domains. There may be multiple fluid domains and multiple solid domains. Each fluid or solid sub-domain is discretized with an overlapping grid. The entire region is associated with a composite grid which is the union of the overlapping grids for the sub-domains. A different physics solver (fluid solver or solid solver) is associated with each sub-domain. A higher-level multi-domain solver manages the entire solution process.     

Lattice Boltzmann simulation of viscous-fluid flow and conjugate heat transfer in a rectangular cavity with a heated moving wall

In the present work, conjugate heat transfer in a rectangular cavity with a heated moving lid is investigated using the lattice Boltzmann method (LBM). The simulations are performed for incompressible flow, with Reynolds numbers ranging from 100 to 500, thermal diffusivity ratios ranging from 1 to 100, and Prandtl numbers ranging from 0.7 to 7. A uniform heat flux through the top of the lid is assumed. Results show that LBM is suitable for the study of heat transfer in conjugate problems. Effects of the Reynolds number, the Prandtl number and the thermal diffusivity ratio on hydrodynamic and thermal characteristics are investigated and discussed. The streamlines and temperature distribution in flow field, dimensionless temperature and Nusselt number along the hot wall are illustrated. The results indicate that increase of thermal diffusivity yields the removal of a higher quantity of energy from lid and its temperature decreases when increasing the Reynolds and the Prandtl numbers.     

Effects of variable specific heat on energy transfer in a high-temperature supersonic channel flow

An energy transfer mechanism in high-temperature supersonic turbulent flow for variable specific heat (VSH) condition through turbulent kinetic energy (TKE), mean kinetic energy (MKE), turbulent internal energy (TIE) and mean internal energy (MIE) is proposed. The similarities of energy budgets between VSH and constant specific heat (CSH) conditions are investigated by introducing a vibrational energy excited degree and considering the effects of fluctuating specific heat. Direct numerical simulation (DNS) of temporally evolving high-temperature supersonic turbulent channel flow is conducted at Mach number 3.0 and Reynolds number 4800 combined with a constant dimensional wall temperature 1192.60 K for VSH and CSH conditions to validate the proposed energy transfer mechanism. The differences between the terms in the two kinetic energy budgets for VSH and CSH conditions are small; however, the magnitude of molecular diffusion term for VSH condition is significantly smaller than that for CSH condition. The non-negligible energy transfer is obtained after neglecting several small terms of diffusion, dissipation and compressibility related. The non-negligible energy transfer involving TIE includes three processes, in which energy can be gained from TKE and MIE and lost to MIE. The same non-negligible energy transfer through TKE, MKE and MIE is observed for both the conditions.     

A study of the heat transfer characteristics of a laser rod in a concentric circular tube

An analytical solution was derived from a two-dimensional heat conduction model with non-uniform boundary conditions for a side-pumped, side-cooled cylindrical laser rod. The convective heat transfer coefficient and the spatially varying fluid temperature were determined from the theoretical solutions or experimental correlations of convective heat transfer in an annular passage with prescribed heat fluxes. The first term of the analytical solution coincides with the result of the one-dimensional model. The other terms indicate that the axial temperature-rise in a laser rod has positive correlations with the axial coolant temperature-rise, the radial Biot number and the length-to-radius ratio of the laser rod. Subsequently, a conjugate numerical simulation that couples up the fluid convection and the solid conduction was performed. Compared with the analytical solution, the conjugate numerical simulation better exhibits the entrance effects of flow and heat transfer; therefore, it may provide more accurate solution in specific cases. PACS 44.10.+i; 44.90.+c     

新型低熔点熔盐黏度的实验研究

熔盐因其具有广泛的使用温度范围,低蒸气压,大热容量,低黏度,良好的稳定性,低成本等诸多特性已成为聚光太阳能热发电中颇有潜力的传热蓄热介质。准确的熔盐热物性对于太阳能发电过程中介质的传热蓄热性能有重要影响。其中熔盐黏度作为重要的热物性之一,对于提高传热效率和降低流动阻力具有决定作用。本文利用研制的高温黏度测量仪对水和HITEC盐的黏度温度特性进行了实验研究,实验结果与文献数据具有较好的一致性,证明了该高温熔盐黏度仪的可靠性。为了降低混合熔盐的熔点,改进其热物性能,本文对Solar Salt进行改性研究,得到两种新型低熔点混合熔盐,并测定得到了黏度温度特性曲线。结果表明,改性后的高温熔融盐黏度有所降低,有利于降低太阳能热发电熔盐传热管路系统的阻力和成本。     

粗糙平板微通道流动和传热的数值模拟

以粗糙平行平板微通道为研究对象,以三角形锯齿状粗糙元模拟固体表面的粗糙度,采用CFD流体固体共轭传热技术数值研究了绝对粗糙度和相对粗糙度对平行平板微通道流动和传热特性的影响,着重分析了粗糙度和流体速度对水力入口段长度和热力入口段长度的影响规律,同时研究了相对粗糙度对微通道转捩雷诺数的影响,为进一步揭示微微通道的流动和传热机理提供了依据.