Film cooling is a typical cooling technology in gas turbines that can lower heat load by spreading coolant on the blade's surface. However, it faces the problem of stress concentration. The present work focuses on optimizing the film cooling hole for minimizing the stress concentration factor based on the surrogate model. The stress concentration factor is the ratio of the maximum stress in a plate with a film hole subjected to frictionless support constraints in the sidewalls at a homogeneous temperature to the average sidewall stress. An optimization platform is built to implement the optimization, which contains a finite element parallel computation module, a support vector regression surrogate model, and a two-layer optimization module for adding sample points around the candidate optimal point. After 50 rounds of optimization process, the optimization results converge. The lowest stress concentration factor obtained is about 1.79, 71.5 % lower than that of the traditional cylinder film hole. Considering that the reduction of the stress concentration factor should not be accompanied by the reduction of the film cooling effectiveness, this work tests the film effectiveness of four candidate holes by means of pressure-sensitive paint experiments. Geo4 has the lowest stress concentration factor and the maximum film effectiveness when both factors are considered.

Film cooling is a commonly used cooling technology in gas turbines. However, it faces the problem of stress concentration. The present work proposes a low -stress film cooling hole with good cooling performance, namely the backward -diffusion elliptical hole. The Pressure Sensitive Paint experiments compare the film effectiveness of the backward -diffusion elliptical hole and the 7-7-7 fan -shaped hole. The film effectiveness of the backwarddiffusion elliptical hole is higher than that of the 7-7-7 fan -shaped hole, especially at high blowing ratios. The structure of the jet vortex system of the backward -diffusion elliptical hole is analyzed by large eddy simulation. The results show that the backward -diffusion elliptical hole induces a stronger anti -counter -rotating vortex pair than the elliptical hole. The anti -counter -rotating vortex pair weakens the harmful effects of the counter -rotating vortex pair on the film effectiveness. The stress concentration factor of the backward -diffusion elliptical hole is obtained by finite element analysis. The backward -diffusion elliptical hole's stress concentration factor is about 2.85, similar to the elliptical hole (2.84). However, the stress concentration factor of the 7-7-7 fan -shaped hole is 6.58. Therefore, the stress concentration factor for the backward -diffusion elliptical hole is only 43.3% of that for the 7-7-7 fan -shaped hole. The backward -diffusion elliptical hole is a more promising lowstress, high -cooling -efficiency film hole.

Film cooling is a commonly used cooling technology in gas turbines, which could reduce heat load by spreading cooling air. However, it faces the problem of stress concentration in structures with holes. The present work focuses on conjugate heat transfer and thermal stress characteristics for a flat film cooling plate through an experimentally validated numerical approach. It discusses the effect of three geometry factors: inclination angle, compound angle, and ellipticity. An engine case simulation and a laboratory case simulation are compared to validate the analogy principle of conjugate heat transfer and thermal stress analysis derived from theoretical analysis. According to the analogy principle, the laboratory flat plate film cooling cases are set to conduct numerical studies. The maximum Mises stress of the film hole is equal to the product of the reference stress and the stress concentration factor. The reference Mises stress is proportional to the overall cooling effectiveness. The stress concentration factor is mainly related to the geometry of the film hole. Reducing the inclination angle of the film hole from 90 degrees to 30 degrees increases the overall cooling effectiveness and drastically increases the stress concentration factor from 2.7 to 5.5. Based on a cylinder hole with a 30 degrees inclination angle, increasing the compound angle enhances the overall cooling effectiveness and slightly increases the stress concentration factor. Based on a cylinder hole with a 30 degrees inclination angle, increasing the ellipticity increases the overall cooling effectiveness and reduces the stress concentration factor. With the increase of ellipticity from 0 to 4, the stress concentration factor decreases from 5.5 to 2. Elliptical film holes are ideal for future low-stress, high-coolingefficiency turbine blades to extend the life of cooling vanes.

The design of film cooling holes facing the higher thermal load in next-generation gas turbine vane should consider the overall performance of film cooling effectiveness and thermal stress properties. The previous study has shown that the elliptical hole is better than the cylinder hole in film cooling effectiveness, and it has a lower stress concentration factor. According to the traditional method for improving the film cooling performance further, the elliptical hole is modified into the backward-diffusion elliptical hole. This study investigates the overall performance of the backward-diffusion elliptical hole using the response surface method. Three independent variables parametrically represent the backward-diffusion elliptical hole: the ellipticity of the inlet ellipse x1 (x1 is an element of [1,4]), the ratio of the short axis between the exit ellipse and the entrance ellipse x2 (x2 is an element of[1,2]), the ratio of the long axis x3 (x3 is an element of [1,2]). The experimental design is carried out using a standard experimental design called a central composite design. Numerical tests are carried out by an experiment validated numerical method. The sensitivity of the film cooling effectiveness, and stress concentration factor to the three geometric parameters (x1, x2, x3) at different blowing ratios (M = 0.5, 1.0) is analyzed. The film effectiveness is positively correlated with x1 and x3 and negatively correlated with x2. The stress concentration factor is negatively correlated with x1 and x3 and positively correlated with x2. This suggests that increasing the ellipticity and lateral expansion is favorable to the film cooling effectiveness and the stress concentration factor.

Rising temperature of gas turbine inlet brings great challenge for blade temperature tolerance, thus high effective cooling structure for turbine blade is vital. In this paper, aerothermodynamic features including heat transfer and pressure drop of a Coriolis-applied rotating smooth U channel are studied in detail. Both experiment and numerical methods are utilized in the study. A rotating cooling structure experiment rig system has been established and validated. The experiments were conducted in the rotating cooling structure experiment rig. Besides, RANS was chosen in the simulation. In the experiment and numerical studies, Reynolds number is constant at 16000 and Rotation number ranges from 0 to 0.024. The results indicate that Coriolis force plays a dominant and positive role on heat transfer ability on trailing wall, and that bend outlet impingement effect is the primary factor compared to Coriolis force for the Nusselt number of smooth leading surface. Besides, Coriolis force at bend region probably suppresses the formation of K-H vortices, thus boosts the flow stability, reduce pressure loss of channel and weakens second heat transfer peak of impingement at the bend outlet. What's more, the total performance of the Coriolis-applied smooth U channel at Ro of 0.006 and 0.024 are 2.18 % and 8.51 % higher than the channel at Ro of 0, which means that rotation is good for the Coriolis-applied smooth U channel and that the channel has superior performance and is encouraging in future rotating blade cooling application.

Film cooling is a commonly used cooling technology in gas turbines, which could reduce heat load by spreading cooling air. However, it faces the problem of stress concentration in structures with holes. The present work focuses on conjugate heat transfer and thermal stress characteristics for a flat film cooling plate through an experimentally validated numerical approach. An engine case simulation and a laboratory case simulation are compared to validate the analogy principle of conjugate heat transfer and thermal stress analysis, which is derived from theoretical analysis. According to the analogy principle, a laboratory flat plate film cooling cases are set in order to study the effect of incline angle on overall cooling effectiveness and thermal stress. The heat transfer on the film hole's inner surface significantly impacts the overall cooling effectiveness. It is shown that the max Mises stress and the stress concentration factor decrease with the increased overall cooling effectiveness and increase with the decreasing inclined angle. It implies that the smaller inclined angle of the cylinder hole hinders the stress trajectory more seriously. A low-stress film hole with an elliptical cross-flow section, whose major axis is parallel to the force, is developed to achieve higher overall cooling effectiveness and a lower stress concentration factor. The stress concentration factor of the cylinder hole is about 5.5, while that of the elliptical hole is only about 1.9. Such a low-stress film cooling hole is promising to improve the fluid-thermal-structure performance of the future cooled turbine vane.

Impingement cooling is widely used in gas turbines because of its excellent local heat transfer capability, and it plays an important role in the next generation of double-wall cooling technology. However, it induces inhomogeneous temperature fields as well as thermal stress fields. In this paper, the conjugate heat transfer and thermal stress characteristics are investigated for an impingement unit including a single round nozzle and solid plate with uniform heat flux on the heated surface through an experimentally validated numerical approach. The studied operating parameter are Reynolds number (from 10000 to 30000), nozzle-to-plate distance ratio (from 2 to 10), and thickness of solid plate (108 mm and 50 mm). The results show that the Nusselt number distribution along radius may have two maxima at a small impingement distance which is driven by the mismatch of maximum wall shear stress location and maximum near-wall turbulence kinetic energy location. Considering the uneven heat transfer distribution as a boundary condition of solid thermal conduction, thermal conduction would reform the heat flux which makes the uniform heat flux boundary condition on the heated surface into uneven heat flux distribution on the impinged surface. The temperature can be lowered and distributed more evenly by increasing the thermal conductivity of the plate. In contrast, the temperature can be lowered but distributed more unevenly by reducing the thickness of the plate. The flat plate expands into a shape with a thin center and thick edges due to the uneven temperature field. This research illuminates the coupling mechanism between convective heat transfer, solid heat conduction, and thermal stress, which has significance for the prediction of gas turbine vane metal fatigue life.

燃气轮机和航空发动机被誉为是工业皇冠上的明珠，其研制水平是一个国家科技水平和综合国力的重要标志。随着燃气轮机和航空发动机工作效率和性能的不断提高，涡轮入口温度逐年上升，涡轮叶片暴露在更高的来流温度下。为使金属叶片在远超其熔点的温度中仍能安全运转，亟需发展高效的冷却技术。该文概述了燃气涡轮高效冷却技术及设计方法的发展趋势，提出了按照3个维度开展燃气涡轮冷却技术研究的思路，总结了本团队在冷却单元-气冷叶栅-整机多部件交互等方面的基础研究成果，搭建了基于实验数据驱动的高效高精度冷却结构设计平台，探索了以双层壁为代表的下一代冷却技术的特性和发展趋势。

Double wall cooling system for the vane is the most promising approach to meet the cooling demand of next generation turbine. The complex structure and heat and mass transfer process make many problems in double wall cooling unclear, which limits the development of double wall cooling in application. In this paper, the effect of impingement-effusion cooling structure on adiabatic film effectiveness is investigated numerically with two models, effusion film cooling-only and impingement-effusion cooling. Results show that the film effectiveness is not sensitive to the mass flow distribution of different rows of film hole and the effect of impingement structure on film effectiveness is very limited. It is therefore indicated that the film effectiveness of double wall cooling could be decoupled with complex heat transfer. It means the effect of impingement structure on adiabatic film effectiveness could be ignored when developing overall cooling models.

Molecular dynamics simulation is performed to simulate the wetting behavior of nano water droplets on flat and pillar surfaces. The result shows that the contact angle of the water droplet on the flat surface becomes smaller with the increase of the surface characteristic energy parameter ε. At the same energy parameter ε, the hydrophobicity is enhanced on the pillar surface compared to the flat surface. For nanostructured surfaces with different geometrical features, the sparser the surface pillars, the larger the contact angle. What’s more, we propose an equivalent potential well method, which can effectively reveal the mechanism of nanostructures changing surface wettability. The deeper the equivalent potential well, the smaller the contact angle.

With proton exchange membrane fuel cell (PEMFC) running, Pt particles are re-deposited in proton exchange membrane PEM after the degradation and migration of Pt cathode catalyst. Classic molecular dynamics simulations are conducted to study the effects of Pt particle on the structure and protons transport of Nafion membrane. The structure of membrane around a Pt particle is observed to present a core-shell structure. The Pt particle is the core coated by the shell of Nafion polymers, with the side-chains of polymers wrapping snugly around the particle. In that structure, some hydronium ions locate in inner shell owing to the electrostatic action with sulfonic acid groups, and few water molecules near particle due to few voids in the structure and hydrophobicity of the backbone of polymers. Besides, the diffusion for hydronium ions irregularly changes over the number of Pt atoms thanks to irregular changes of water channels. While the hopping of protons is to decline over Pt atoms due to greater loss of hydrogen bonding acceptable sites caused by larger particle. (C) 2019 Elsevier Ltd. All rights reserved.

Multiple energy system could meet the needs of the user through different energy conversion ways. So if the load level is constant, the operating state of energy system could be different to meet different demand. By the analysis of energy flow of system, it can be known that the degrees of freedom come from the dispatch point of energy flow. Therefore, the dispatch factors and the input energy flows could be considered as the independent variables, and make a comprehensive evaluation criterion which considered the energy efficiency, economy and emission, as the optimization goal. The operation of the multi-energy flow system has been optimized. Through case analysis, the proposed optimal energy flow operation strategy was verified and analysed.

Molecular dynamics simulation was applied to test and evaluate the ability of several models of carbon dioxide on predicting thermodynamics and transport properties. Firstly, we compared the liquid-vapor coexist curves of seven kinds of carbon dioxide models by molecular dynamics simulations. It was found that the Cygan_flex model and EPM2 model were more accurate than the others. Then we investigated the structural properties of carbon dioxide using NPT ensemble molecular dynamics simulation. The fluid became less dense with the increasing temperature. Thirdly, the self-diffusion coefficients were studied at temperature and pressure up to 600 K and 80 MPa, respectively. The results showed that the self-diffusion coefficient decreased with the increasing pressure and increased with increasing temperature. Finally, we calculated the thermal conductivity of carbon dioxide at 250 K using EPM2_flex model, Cygan_flex model and TraPPE_flex model. So, we should pay attention to the selection of appropriate carbon dioxide models to obtain different carbon dioxide properties. (C) 2019 Elsevier Ltd. All rights reserved.

Energy hub has been widely used in modeling of multi-energy system and energy Internet since it is put forward, and the general model of energy hub is developed and improved in this paper. The existing energy hub model used in previous studies is established based on the steady-state operation model of the energy conversion equipment, which only considers the factors of energy distribution and conversion efficiency in energy hub, but does not consider the off-design properties of energy conversion equipment. Therefore, this paper studies the off-design characteristics of gas turbine and heat recovery steam generator in the cogeneration energy hub, and brings the off-design characteristics of equipment into the energy hub model, so as to obtain off-design analysis model of energy hub. This work has important implications for the comprehensive energy efficiency assessment of multi-energy systems and energy Internet.

The desorption behavior of methane in slit was studied in this paper. We build a differential equation which describe dynamic desorption process, and propose a correction method. The mass transfer resistance in free region is considered and the accuracy of the result is improved using this correction method. Based on differential equation, the effects of pressure, temperature and solid material on dynamic desorption speed are analyzed. Desorption becomes faster when pressure increases. When pressure is low, desorption speed increases with increasing temperature; oppositely, desorption speed decreases with increasing temperature. When pressure is low, the desorption speed at different wall material is quartz > kaolinite > graphite; when pressure is high, the desorption speed is quartz > graphite > kaolinite. (C) 2019 Elsevier Ltd. All rights reserved.