Heat transfer coefficient of wheel rim of large capacity steam turbines

A way of calculating the overall equivalent heat transfer coefficient of wheel rims of large capacity steam turbines is presented. The method and formula to calculate the mean forced convection heat-transfer coefficient of the surface of the blade and for the bottom wall of the blade passage, are introduced. The heat transmission from the blade to the rim was simplified by analogy to heat transmission in the fins. A fin heat transfer model was then used to calculate the equivalent heat transfer coefficient of the blade passage. The overall equivalent heat transfer coefficient of the wheel rim was then calculated using a cylindrical surface model. A practical calculation example was presented. The proposed method helps determine the heat transfer boundary conditions in finite element analyses of temperature and thermal stress fields of steam turbine rotors.     

大功率汽轮机叶轮轮缘传热系数的研究

提出了大功率汽轮机叶轮轮缘总传热系数的计算方法.介绍了汽轮机动叶片叶身平均对流换热表面传热系数和叶片流道下壁面对流换热表面传热系数的计算方法和计算公式.把汽轮机叶片对叶轮的传热简化为肋片传热,使用肋片传热模型计算汽轮机叶片流道的等效传热系数,采用圆筒壁模型计算汽轮机叶轮轮缘的总传热系数,并给出了应用实例.在汽轮机转子的温度场与热应力场有限元分析中,该计算方法为确定叶轮轮缘的传热边界条件提供了依据.     

汽轮机转子枞树型轮缘的强度评估

文章以一种新型的枞树型轮缘为研究对象,讨论了它的强度评估方法。文章利用解析法表征枞树型轮缘拉应力、弯应力和剪应力,确定各应力的校核截面位置和特征。同时还讨论了在强度校核中的关键技术,复杂结构的离心力计算问题,上述问题的解决为枞树型轮缘强度计算的程序化奠定了基础。理论分析和数值计算结果显示,文章给出的方法能快速准确地进行枞树型轮缘强度分析,适用于汽轮机概念设计阶段轮缘的选择和设计。     

超临界和超超临界汽轮机汽缸传热系数的研究

提出了汽轮机汽缸传热系数的计算方法。介绍了超，临界和超超临界压力汽轮机汽缸光滑内表面和安装镶片式汽封表面的对流换热表面传热系数的计算公式，安装整体车制式汽封的汽缸内表面、安装静叶的汽缸内表面和安装隔板的汽缸内表面的传热过程总传热系数的计算方法。采用圆筒壁与肋片传热等简化模型来计算汽封块、静叶和隔板的传热过程总传热系数。给出了某型号超，临界600MW汽轮机高压内缸内表面传热系数的计算结果。该方法考虑了不同运行工况下汽缸不同部位的传热过程，在超临界和超超临界压力汽轮机汽缸的温度场与热应力场的有限元法数值计算和寿命评定中，为确定传热边界条件提供了依据。     

Assessment of linear and non-linear two-equation turbulence models for aerothermal turbomachinery flows

Three linear two-equation turbulence models k -ε, k -ωand k -1 and a non-linear k -1 model are used for aerodynamic and thermal turbine flow prediction. The pressure profile in the wake and the heat transfer coefficient on the blade are compared with experimental data. Good agreement is obtained with the linear k -1 model. No significant modifications are observed with the non-linear model. The balance of transport equation terms in the blade wake is also presented. Linear and non-linear k -1 models are evaluated to predict the three-dimensional vortices characterising the turbine flows. The simulations show that the passage vortex is the main origin of the losses.     

Effects of rim location, rim height, and tip clearance on the tip and near tip region heat transfer of a gas turbine blade

Effects of the rim height and the tip gap clearance on the heat transfer coefficients on the blade tip and near tip regions were measured with two different rim geometries. The heat transfer coefficient distributions were measured using the transient single color capturing liquid crystals technique. Rims were located along (a) the pressure and the suction side (full-rim case) and (b) the suction side of the blade tip (suction side rim case). The rim heights were (a) 2.1%, (b) 4.2%, and (c) 6.3% and the blade tip gap clearances were (a) 1.0%, (b) 1.5%, and (c) 2.5% of the blade span. Tests were performed on a five-bladed linear cascade placed in a blowdown facility. The overall pressure ratio, inlet total pressure to exit static pressure, was 1.2, and the Reynolds number based on the exit velocity and the axial cord length was 1.1 × 10⁶. The turbulence intensity level at the cascade inlet was 9.7%, and the inlet and exit Mach number were 0.25 and 0.59, respectively. It was found that higher rims reduce the heat transfer coefficients on the tip and shroud, but the reduction on the pressure and suction sides was not significant. The suction side rim case provided lower heat transfer coefficients on the blade tip and near tip regions than the full-rim case.     

用间隙元求解枞树形叶根轮缘的接触问题

就汽轮机枞树形叶根齿面与轮缘的接触状态进行了研究.通过在接触面上施加间隙元来解决叶根轮缘的接触问题,计算结果表明每一对叶根齿面的承载比直接取决于叶根齿与轮缘的初始接触情况,而每一对齿的内弧齿面的承载比与背弧齿面的承载比的变化则还与叶型相对叶根的位置有关.     

Heat transfer in a large-scale circulating fluidized bed boiler

Heat transfer of a furnace in a large-scale circulating fluidized bed (CFB) boiler was studied based on the analysis of available heat transfer coefficient data from typical industrial CFB boilers and measured data from a 12 MW_e, a 50 MW_e and a 135 MW_e CFB boiler. The heat transfer of heat exchanger surfaces in a furnace, in a steam/water cooled cyclone, in an external heat exchanger and in the backpass was also reviewed. Empirical correlation of heat transfer coefficient was suggested after calculating the two key parameters, solids suspension density and furnace temperature. The correlation approach agrees well with the data from the large-scale CFB boilers. __________ Translated from Journal of Power Engineering, 2006, 26(3): 305–310 (in Chinese) [译自: 动力工程]     

考虑空气量影响时蒸汽凝结放热系数的计算方法分析

空气量对蒸汽凝结放热系数影响的计算，目前还没有一个人们普遍公认的计算方法。文中首先对空气对轻微流动蒸汽、受迫流动蒸汽以及抽气器运行时蒸汽凝结放热系数影响进行了综述分析，然后对目前常用的几种计算空气量对蒸汽凝结放热系数影响的计算方法进行了计算分析，指出各种计算方法的特点及其存在的问题，为进一步研究空气对蒸汽凝结放热系数的影响奠定了一定的基础。     

凹槽式叶顶流动换热的数值研究

针对叶尖间隙高度对凹槽式叶顶流动与换热的影响展开数值研究,评估4种湍流模型在叶顶换热方面的预测能力.结果表明：凹槽肩壁顶部、凹槽腔底部近前缘区域和叶顶尾缘为高换热区,凹槽腔底的中部和尾部区域为低换热区;不同湍流模型对叶尖间隙泄漏量预测差别很小,但泄漏流流动状态差异很大,这是造成不同湍流模型对叶顶换热预测存在重大差别的原因;在研究的间隙范围内,叶尖间隙泄漏量和叶顶换热强度随间隙高度的增大而增加;在所选的4种湍流模型中,k-ω模型是叶顶换热数值模拟较好的湍流模型选择.     

Dropwise Condensation Heat Transfer on Plasma-Ion-Implanted Small Horizontal Tube Bundles

Stable dropwise condensation of saturated steam was achieved on stainless-steel tube bundles implanted with nitrogen ions by plasma ion implantation. For the investigation of the condensation heat transfer enhancement by plasma ion implantation, a condenser was constructed in order to measure the heat flow and the overall heat transfer coefficient for the condensation of steam on the outside surface of tube bundles. For a horizontal tube bundle of nine tubes implanted with a nitrogen ion dose of 10¹⁶ cm^{? 2}, the enhancement ratio, which represents the ratio of the overall heat transfer coefficient of the implanted tube bundle to that of the unimplanted one, was found to be 1.12 for a cooling-water Reynolds number of about 21,000. The heat flow and the overall heat transfer coefficient were increased by increasing the steam pressure. The maximum overall heat transfer coefficient of 2.22 kW · m^?2· K^?1 was measured at a steam pressure of 2 bar and a cooling-water Reynolds number of about 2,000. At these conditions, more dropwise condensation was formed on the upper tube rows, while the lowest row received more condensate, which converted the condensation form to filmwise condensation.     

斜齿枞树型叶根倾斜角度对叶根接触影响分析

文章针对不同倾斜角度，对斜齿枞树型叶根透平叶片的叶根和轮槽的接触状态进行了分析。通过三维建模和有限元分析，发现斜齿枞树型叶根各齿栽荷分布随角度变化不大，且各齿栽荷分布没有直齿枞树型各齿载荷分布均匀。叶根最大应力随叶根倾斜角增大而增大，对低温区叶片来说，由倾斜角度增大引起的叶片应力增大可忽略不计。但对于高温区叶片，减小倾斜角度以使叶片应力降低是很有积极意义的。本研究可为枞树型叶根的设计提供理论支持。     

功能表面降膜蒸发传热特性的实验研究

研究了处理表面镀铬铝管、PTFE铜管和纯铝氧化管水平管降膜蒸发传热，研究了喷淋密度、热流密度、管内蒸汽速度和管表面处理对降膜蒸发传热特性的影响。实验结果表明：在表面蒸发区，水平管降膜蒸发传热系数随热流密度的增加而提高，随喷淋密度增大先降低后升高，冷凝例传热系数基本保持不变。总传热系数对操作条件变化很不明显，表面阳极氧化膜使传热系数略有下降，但由于其优良的抗垢时蚀性能，非常有必要再进行深入地研究。     

New response surface model and its applications in aerodynamic optimization of axial compressor blade profile

A parametric method for the axial compressor 2D blade profiles is proposed in which the blade geometries are defined with the parameters commonly used for blade definition, which ensures that the geometric significance is clear and an unreasonable blade profile is not generated. Several illustrations are presented to show the fitting precision of the method. A novel response surface model is proposed which regards the objective distribution function in the vicinity of a sample as normal school, and then generates the response surface function in the whole design space by a linear combination of distribution functions of all the samples. Based on this model, a numerical aerodynamic optimization platform for the axial compressor 2D blade profiles is developed, by which aerodynamic optimization of two compressor blade profiles are presented. __________ Translated from Acta Aeronautica et Astronautica Sinica, 2007, 28(4): 813–820 [译自: 航空学报]     

Experimental Investigation of Transient Heat Transferin the Once-Through Boiler Water Separator

INTRODUCTI0NWaterseparat0risanimportantthickwallc0mpo-nentof600MWsupercriticalpressureboiler.Itsmainfunctionist0ensurethattheevap0rator,superheater,reheaterandeconomizert0becooledfullyandoper-atesafelyduringstart-up.Itisfittedatthe0utletofevaPorator.Whentheb0ilerloadislessthan35%MCR(boilermaJximumc0ntinuousevaporation),sub-cooledwaterorwatersteammixturefromtheevap-orator0fupperc0mbustioncharnberenterstangen-tiallyinthewaterseparator.Thesteam,separatedbycentrifugalforceandgravity,flowsi…     

Probability strength design of steam turbine blade and sensitivity analysis with respect to random parameters based on response surface method

Many stochastic parameters have an effect on the reliability of a steam turbine blade during practical operation. To improve the reliability of blade design, it is necessary to take these stochastic parameters into account. An equal cross-section blade is investigated and a finite element model is built parametrically. Geometrical parameters, material parameters and load parameters of the blade are considered as input random variables while the maximum deflection and maximum equivalent stress are output random variables. Analysis file of the blade is compiled by deterministic finite element method and applied to be loop file to create sample points. A quadratic polynomial with cross terms is chosen to regress these samples by step-forward regression method and employed as a surrogate of numerical solver to drastically reduce the number of solvers call. Then, Monte Carlo method is used to obtain the statistical characteristics and cumulative distribution function of the maximum deflection and maximum equivalent stress of the blade. Probability sensitivity analysis, which combines the slope of the gradient and the width of the scatter range of the random input variables, is applied to evaluate how much the output parameters are influenced by the random input parameters. The scatter plots of structural responses with respect to the random input variables are illustrated to analyze how to change the input random variables to improve the reliability of the blade. The results show that combination of the finite element method, the response surface method and Monte Carlo method is an ideal way for the reliability analysis and probability strength design of the blade. __________ Translated from Proceedings of the CSEE, 2007, 27(20): 12–17 [译自: 中国电机工程学报]     

Experimental study of dropwise condensation on plasma-ion implanted stainless steel tubes

Plasma-ion implantation was used to achieve stable dropwise condensation of saturated steam on stainless steel tubes. For the investigation of the efficiency of plasma-ion implantation regarding the condensation process a condenser was constructed in order to measure the heat flux density and the heat transfer coefficient h_c for the condensation of steam on the outside surface of a single horizontal tube. For tubes implanted with a nitrogen ion dose of 10¹⁶ cm⁻², the heat transfer coefficient h_c was found to be larger, by a factor of 3.2, in comparison to values theoretically calculated by the corrected Nusselt film theory. The heat flux density and the heat transfer coefficient h_c were found to increase with increasing ion dose and steam pressure. The heat transfer coefficient decreases with increasing surface subcooling as it has been found in former work for dropwise condensation on ion implanted vertical plates.     

Three－Dimensional Numerical Simulation of Natural Convection Heat Transfer in an Inclined Cylindrical Annulus

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Sensitivity analysis and numerical experiments on transient test of compact heat exchanger surfaces

A single-blow transient testing technique considering the effect of longitudinal heat conduction is suggested for determining the average convection heat transfer coefficient of compact heat exchanger surface. By matching the measured outlet fluid temperature variation with similar theoretical curves, the dimensionless longitudinal conduction parameter λ₁, the time constant of the inlet fluid temperature τ⁺, and the number of heat transfer units N _tu can be determined simultaneously using the Levenberg-Marquardt nonlinear parameter estimation method. Both sensitivity analysis and numerical experiments with simulated measurements containing random errors show that the method in the present investigation provides satisfactory accuracy of the estimated parameter N _tu, which characterizes the heat transfer performance of compact heat exchanger surfaces. __________ Translated from Journal of Power Engineering, 2007, 27(2): 227-232 [译自:动力工程]     

Convection Condensation Heat Transfer of Steam-Air Mixture With Heat Pipe Heat Exchanger

A heat pipe heat exchanger (HPHE) was used to investigate the heat transfer performance of steam-air mixture condensation, analogous to the dew condensation of flue gas, when the steam volume fraction ranged from 0 to 20%, and the inlet temperature of steam-air mixture varied from 70 to 120°C. Self-assembled monolayers (SAMs) treatment with n-octadecyl mercaptan was adopted to modify the condensation surface of the heat pipe. The comparisons were conducted to examine the influence of SAMs on condensation heat transfer of steam-air mixture vapor. The results indicate that the convection condensation heat transfer coefficient increases with the increase of steam volume fraction and Re number of the steam-air mixture. As the inlet temperature increases, the heat transfer coefficient decreases accordingly. The heat transfer performance can be improved by the SAMs surface, with a heat transfer enhancement ratio up to 1.6 at a condition of 20% of the steam volume fraction and 1500 Re number.