大型燃气轮机透平第一级静叶表面温度分布的计算方法

利用附加源项法计算叶片外表面换热系数及温度分布,编制叶片内部冷却计算程序及壁面导热程序,应用该程序计算了某大型燃气轮机第一级静叶表面温度分布,对燃气涡轮叶片先进的内外部冷却系统设计方法的消化吸收奠定了基础。     

Numerical simulation of steady state heat transfer in a ceramic-coated gas turbine blade

As gas turbine entry temperature (TET) increases, thermal loading on first stage blades increases and, therefore, a variety of cooling techniques and thermal barrier coatings (TBCs) are used. In the present work, steady state blade heat transfer mechanisms were studied via numerical simulations. Convection and radiation to the blade external surface were modeled for a super alloy blade with and without a TBC. The effects of surface emissivity changes, partial TBC coatings and uncertainties in external heat transfer coefficient were also simulated. The results show that at 1500 K TET, radiation heat transfer rate from gas to an uncoated blade is 8.4% of total heat transfer rate which decreases to 3.4% in the presence of a TBC. The TBC blocks radiation, suppresses metal temperatures and reduces heat loss to the coolant. These effects are more pronounced at higher TETs. With selective coating, substantial local temperature suppression occurs. In the presence of radiation and/or TBC, the uncertainties in convection heat transfer coefficient do not have a significant effect on metal temperatures.     

Evaluation tests of 1700 °C class turbine cooled blades for a hydrogen fueled combustion turbine system

The development of 1700 °C class hydrogen fueled combustion turbine system with output of 500 MW and thermal efficiency of over 60% (HHV) has been conducted in the World Energy Network (WE‐NET) program. This paper describes the development of the first‐stage turbine cooled stator and rotor blades applied to the power generation system. The conceptual design of these cooling blades which were served in hot steam flow was carried out. The hybrid cooling method combining recovery cooling with partial ejection cooling was chosen from several cooling systems from a viewpoint of plant efficiency, operational reliability, and durability of cooled blades. Also, the single crystal superalloy (SC) as a blade substrate and thermal barrier coating (TBC) were applied. The experiments of the scale model turbine cooled blades were carried out using a hydrogen–oxygen combustion wind tunnel with practical steam conditions of 1700 °C and 2.5 MPa. The cooling effectiveness and metal temperature at rated condition and the soundness of TBC and blade substrate of the first stage stator and rotor test blades were clarified. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(3): 237–252, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10088     

Overall Thermal Performances of Double-Wall Effusion Cooling Covered by Simulated Thermal Barrier Coatings

A coupling configuration of double-wall cooling and exterior surface thermal barrier coating(TBC)is one of the most promising thermal protection methods of hot components of modem gas turbine.The combined influences of coating thickness,impingement layout,and cooling air flowrate on the overall thermal performances of such configuration were discussed deeply,to provide the valuable guidance of design.Overall effectiveness measurements were implemented under engine-matched Biot numbers and mainstream-to-coolant temperature ratio.Conjugate heat transfer simulations provided the additional information difficult to be acquired by the measurements.The results indicated that the contribution of TBC is much larger than that of increasing the cooling air amount.The thicker TBC can produce the stronger insulation,while the higher risk of thermal damage of itself.The larger coolant flowrate enlarges the benefit of TBC,while the trend is suppressed by the thick TBC.The constant coating thickness cannot bring to the uniform metal temperature,which can be solved through properly adjusting the backside impingement.The trends in overall effectiveness with TBC’s thickness are independent on the change of internal impingement.     

Numerical predictions of augmented heat transfer of an internal blade tip-wall by hemispherical dimples

The heat transferred to the turbine blade is substantially increased as the turbine inlet temperature is increased. Improved cooling methods are therefore needed for the turbine blades to ensure a long durability and safe operation. The blade tip region is exposed to very hot gas flow, and suffers high local thermal loads due to the external tip leakage flow. A common way to cool the tip is to design serpentine passages with 180° turn under the blade tip-cap taking advantage of the three-dimensional turning effect and impingement. Increased internal convective cooling is therefore required to increase the blade tip lifetime. In this paper, augmented heat transfer of a blade tip with internal hemispherical dimples has been investigated numerically. The computational models consist of two-pass channels with 180° turn and arrays of dimples depressed on the internal tip-cap. Turbulent convective heat transfer between the fluid and dimples, and heat conduction within dimples and tip are simultaneously computed. The inlet Reynolds number is ranging from 100,000 to 600,000. Details of the 3D fluid flow and heat transfer over the tip-walls are presented. Comparisons of the overall performance of the models are presented. It is found that due to the combination of turning impingement and dimple-induced advection flow, the heat transfer coefficient of the dimpled tip is up to two times higher than that of a smooth tip with less than 5% pressure drop penalty. It is suggested that the use of dimples is suitable for augmenting blade tip cooling to achieve an optimal balance between thermal and mechanical design requirements.     

Conjugate heat transfer investigation on the cooling performance of air cooled turbine blade with thermal barrier coating

A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera. Besides, conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison. The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant, and spatial difference is also discussed. Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest. The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path. Thermal barrier effects of the coating vary at different regions of the blade surface, where higher internal cooling performance exists, more effective the thermal barrier will be, which means the thermal protection effect of coatings is remarkable in these regions. At the designed mass flow ratio condition, the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface, while this value is 0.09 on the suction side.     

大功率汽轮机高温叶片蠕变特性数值研究

近年来汽轮机朝着大功率、高参数方向快速发展,汽轮机进口蒸汽温度不断提高,导致叶片的工作环境进一步恶化.叶片作为汽轮机的核心部件,其安全性直接影响汽轮机机组的运行状况,因此研究高温条件下叶片的强度和蠕变特性非常重要.以某大功率汽轮机高温叶片为例,构造了叶片和叶轮三维有限元模型,采用商用有限元软件ANSYS分析了离心力和温度场共同作用下的叶片热弹性应力及变形;然后,应用诺顿模型分析了该叶片经历100 000 h蠕变历程的应力和应变.建立了完整的汽轮机叶片蠕变特性分析数值模型,研究工作为汽轮机叶片的静强度和蠕变特性研究提供了具体的方法,所得结论对于高温叶片设计具有指导意义.     

透平冷却空气量计算方法综述

燃气轮机效率提高的主要途径是提高透平进口温度。随着透平进口温度的不断提高,对冷却空气量的需求也逐渐增多,为保证透平安全可靠运行,透平冷却空气量的计算就显得尤为重要。本文对比了国内几篇文献中针对V94.3燃气轮机透平冷却空气量的估算方法,同时介绍了国内外其他研究人员利用流体网络法的研究成果。通过对比分析可知,采用叶片冷却模型以及从燃气轮机功率角度估测冷却空气量的方法适用于工程应用。流体网络法有严谨的理论支持,可针对空气系统具体部件进行计算分析。     

带有冷气掺混的三级透平气动性能数值研究

借助NUMECA数值仿真软件,以某型燃气轮机的三级透平作为计算模型,对其在冷却气体掺混前后的流场进行了数值模拟。考虑到工质物性的影响,采用了变比热高温燃气作为计算工质。同时,针对燃气轮机透平进口的变工况问题,选取不同的透平进口总压值进行数值计算。结果表明,冷却气体的加入使得级损失增大,每列叶片流道出口速度或相对速度减小,下游叶片进口气流角减小;在三级透平冷气掺混时改变进口总压值,每列叶片流道的进口气流角几乎不变,除第三级动叶的激波损失与尾迹损失增大外,其余叶片流道的能量损失变化不明显。     

Film cooling on a gas turbine blade pressure side or suction side with axial shaped holes

The film cooling effectiveness on the surface of a high pressure turbine blade is measured using the pressure sensitive paint (PSP) technique. Four rows of axial laid-back, fan-shaped cooling holes are distributed on the pressure side while two such rows are provided on the suction side. The coolant is only injected to either the pressure side or suction side of the blade at five average blowing ratios ranging from 0.4 to 1.5. The presence of wakes due to upstream vanes is simulated by placing a periodic set of rods upstream of the test blade. Effect of the upstream wakes is recorded at four different phase locations with equal intervals along the pitch-wise direction. The freestream Mach numbers at cascade inlet and exit are 0.27 and 0.44, respectively. Results reveal that the tip leakage vortices and endwall vortices sweep the coolant film on the suction side to the midspan region. The film cooling effectiveness on the suction side is usually higher than that on the pressure side except the regions affected by the secondary vortices. The presence of upstream wakes results in lower film cooling effectiveness on the blade surface. The moderate blowing ratios (M = 0.6 or M = 0.9) give higher film cooling effectiveness immediately downstream of the film cooling holes. Further downstream of the holes, higher blowing ratios cover wider surface area.     

Numerical investigation of the effectiveness of effusion cooling for plane multi-layer systems with different base-materials

Within Collaborative Research Center (SFB) 561 “Thermally Highly Loaded, Porous and Cooled Multi-Layer Systems for Combined Cycle Power Plants” at RWTH Aachen University, an effusion-cooled multi-layer plate configuration is investigated numerically by the application of a three-dimensional in-house fluid flow and heat transfer solver, CHTflow. CHTflow is a conjugate code, which yields information on the temperature distribution in the solid body. This enables a detailed discussion of the effects of a change in materials. The geometrical set-up and the fluid flow conditions derive from modern gas turbine combustion chambers and bladings. Within the SFB, two different multi-layer systems, one consisting of substrate made of CMSX-4 (a singlecrystal super-alloy), anMCrAlY-bondoat and a ZrO₂ thermal barrier coating (TBC), and the other consisting of a NiAlalloy and a graded bondcoat/TBC, have been investigated. The grading will increase the life-span of the TBC as it can better compensate the different thermal expansion coefficients of different materials. The main focus in this study is on the different substrate materials, because the thermal conductivity of the NiAl is considerably higher than that of CMSX-4, which leads to different temperature profiles in the components.     

Unsteady Numerical Simulation of Hot Streak/Blades Interaction and Film Cooling

Deeply research on management and application of hot streak is an important way to breakthrough technique obstacle of aero engine hot components. Numerical method is a useful instrument to investigate the correlative problems. Firstly the paper developed independently three dimensional unsteady parallel computational code-MpiTurbo based on Fortran 90 and MPI at Linux operating system. Then unsteady numerical simulation was carried out to investigate impacts of the factors, which included circumferential locations of hot streak and clocking positions of blade rows, on the thermal environment of a 1＋1 counter-rotating turbine. The results clear- ly indicated that clocking positions of hot streak/blade row and blade row/blade row had great influence on the time-averaged temperature distribution of the third blade row. Therefore, it can be effective for improving thermal environment of turbine to optimize blade parameters and clocking positions. Lastly film cooling layout was de- signed by the repetitious steady simulation based on source term method. And the flow structure detail was given by the unsteady simulation.     

Effects of flow direction and thermal short-circuiting on the performance of small coaxial ground heat exchangers

The effects of flow direction and thermal short-circuiting on the performance of small-size coaxial ground heat exchangers, currently used in Northern Italy, are studied by finite-element simulations, performed through the software package COMSOL Multiphysics 3.4 (©Comsol, Inc.). The real 2-D axisymmetric unsteady heat conduction and convection problem is considered, both for winter and for summer working conditions. The flow in the outer annular passage is laminar in winter and turbulent in summer. The distribution of the fluid bulk temperature in the inner circular tube is determined by means of the weak form boundary condition available in COMSOL Multiphysics; the forced-convection heat transfer in the outer annular passage is simulated directly. Two Small Coaxial Ground Heat Exchangers (SCGHEs) with the same length (20 m) but different cross-sections are examined; moreover, two values of the ground thermal conductivity, as well as two materials for the inner tube wall are considered. The results point out that the annulus-in flow direction (fluid inlet in the outer annular passage) is more efficient than the center-in flow direction (fluid inlet in the inner circular tube) and that, on account of the small length, the effect of thermal short-circuiting is not important for SCGHEs, especially if the annulus-in flow direction is employed.     

舰船燃气轮机高压涡轮动叶多维热耦合设计方法

针对舰船燃气轮机复杂高效冷却叶片设计,基于压力修正算法建立冷却叶片一维管网设计方法;通过快速求解可压缩边界层微分方程获得叶片外换热边界,基于参数化的叶片网格生成方法,采用全隐式有限体积的固体导热求解方法,构建了冷却叶片的耦合传热模型,开发了耦合传热计算程序。对某高压涡轮动叶进行多维热耦合设计,确定冷却流路及冷气分布,通过三维气热耦合计算验证了设计方案的可行性,通过对比分析验证了多维热耦合设计方法对主要流通单元的流量、压力误差小于5%,具备较高的工程应用价值。     

喷雾降温对燃气轮机涡轮叶片损伤的影响

建立了燃气轮机高温涡轮叶片损伤评估模型,包括热力学性能计算模型、应力评估模型、热评估模型和交互损伤分析模型,无法测量参数由热力学性能计算模型计算,作为应力评估模型和热评估模型的输入。根据蠕变与疲劳损伤模型分析结果,对进气道内使用喷雾冷却降温的燃气轮机高温涡轮叶片进行损伤评估,比较了燃气轮机在不同转速以及负荷下,使用喷雾冷却系统前后,高温涡轮叶片损伤的变化,定量评估喷水量对高温叶片寿命的改善。结果表明:启用喷雾冷却系统可以大幅减小因蠕变造成的叶片损伤,在低负荷(30%)时损伤减小的幅度尤为明显,其预期寿命从40 000 h延长到50 000 h以上,可以大幅延长叶片的使用寿命;在夏季运行时(53%负荷),如果以减少蠕变损伤为目标,可以考虑增加喷水量,从40%～100%,叶片各级蠕变损伤最高可减小13.5%。     

不同冷气/燃气温比下高温涡轮叶片旋流冷却流固耦合特性研究

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。     

Transonic turbine blade loading calculations using different turbulence models – effects of reflecting and non-reflecting boundary conditions

The objective of this study is to simulate the transonic gas turbine blade-to-blade compressible fluid flow. We are interested mainly in the determination of the pressure distribution around the blade. The particular blade architecture makes these simulations more complex due to the variety of phenomena induced by this flow.Our study is based on the experiment performed by Giel and colleagues. Tests were conducted in a linear cascade at the NASA Glenn Research Center. The test article was a turbine rotor with design flow turning of 136° and an axial chord of 12.7 cm.Simulations were performed on an irregular quadratic structured grid with the FLUENT software package which solves the Navier–Stokes equations by using finite volume methods. Two-dimensional stationary numerical simulations were made under turbulent conditions allowing us to compare the characteristic flow effects of Reflecting Boundary Conditions (RBC) and Non-Reflecting Boundary Conditions (NRBC) newly implemented in FLUENT 6.0. Many simulations were made to compare different turbulence models: a one equation model (Spalart–Allmaras), several two-equation models (k–ε, RNG k–ε, Realizable k–ε, SST k–ω), and a Reynolds-stress model (RSM). Also examined were the effects of the inlet turbulence intensities (0.25% and 7%), the exit Mach numbers (1.0 and 1.3) and the inlet Reynolds numbers (0.5 × 10⁶ and 1 × 10⁶). The results obtained show a good correlation with the experiment.     

Influence of thermal sensitivity of the materials on temperature and thermal stresses of the brake disc with thermal barrier coating

The time-dependent frictional heating of a disc with applied thermal barrier coating (TBC) on its working surface was investigated. To determine the temperature fields in the coating and the disc a one-dimensional friction heat problem during braking was formulated, with taking into account the dependence of thermal properties of materials from temperature. A model was adopted for materials with a simple non-linearity, i.e. materials whose thermal conductivity and specific heat are temperature dependent, and their ratio – thermal diffusivity is constant. The linearization of the corresponding boundary-value heat conduction problem was made by the Kirchhoff transformation and the linearizing multipliers method. A numerical-analytical solution to the obtained problem was found by Laplace transform method. Knowing the temperature distributions, quasi-static thermal stresses in the strip (TBC) with taking into account change in temperature mechanical properties, were determined. The distribution of temperature and thermal stresses in the strip made from ZrO₂ deposited on the UNS G51400 steel disc, was investigated.     

A novel pressurized CHP system with water extraction and refrigeration

A novel Cooling, Heat, and Power (CHP) system has been proposed that features a semi-closed Brayton cycle with pressurized recuperation, integrated with a Vapor Absorption Refrigeration System (VARS). The semi-closed Brayton cycle is called the High Pressure Regenerative Turbine Engine (HPRTE). The VARS interacts with the HPRTE power cycle through heat exchange in the generator and the evaporator. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration unit, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration in an amount which depends on ambient conditions. Water produced as a product of combustion is intentionally condensed in the evaporator of the VARS, which is designed to provide sufficient cooling for the inlet air to the high-pressure compressor, water extraction, and for an external cooling load. The computer model of the combined HPRTE/VARS cycle predicts that with steam blade cooling and a medium-sized engine, the cycle will have a thermal efficiency of 49% for a turbine inlet temperature of 1400 °C. This thermal efficiency is in addition to the large external cooling load generated in the combined cycle which is 13% of the net work output. In addition it also produces up to 1.4 kg of water for each kg of fuel consumed, depending upon the fuel type. When the combined HPRTE/VARS cycle is optimized for maximum thermal efficiency, the optimum occurs for a broad range of operating conditions. Details of the multivariate optimization procedure and results are presented in the paper.Previous studies have demonstrated the following attributes of the combined HPRTE/VARS cycle: attaining high part power efficiency in a compact package, threefold specific power increase over the state of the art, reduced IR signatures due to lower exhaust temperature, significant reduction of exhaust particulates and smoke, constant high-pressure compressor inlet temperature and order-of-magnitude reductions in emissions such as NO_x, CO and unburned hydrocarbons. The integrated nature of this system allows overall reduction in size and weight of approximately 50% relative to conventional equipment. The combination of positive attributes makes the HPRTE combined cycle engine attractive for future mobile power applications in terms of performance as well as life cycle cost.     

燃气轮机叶片内部扰流肋冷却方式研究进展

随着燃气透平转子进口温度的不断提高,燃气轮机叶片冷却日益重要。带有扰流肋的内部通道冷却是叶片冷却的一个重要部分。综述了内部扰流肋冷却的研究历程与研究现状,详细论述了静止状态下带肋内部通道的换热研究、旋转对带肋通道内换热的影响研究以及扰流肋与其他方式相结合的复合冷却研究。结论指出,在国内外静止状态下带肋通道内的换热研究已经很成熟,旋转对通道内流动与换热的影响是最近几年来的研究热点,而关于旋转状态下复合冷却方式的研究相对较少。优化旋转状态下内部肋结构和将内部扰流肋与其他冷却方式相结合的研究是今后的发展方向。