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Liu B.,Shanghai JiaoTong University | Yang J.,Shanghai Turbine Works Co. | Zhou D.,Shanghai Turbine Works Co. | Zhu X.,Shanghai JiaoTong University | Du Z.,Shanghai JiaoTong University
Proceedings of the ASME Turbo Expo | Year: 2015

In steam turbine plants, the last stages of the low pressure (LP) turbines can deliver up to 20% of the overall power of the plant. It poses lots of challenges to designers especially when the last stages are operated under low volume flow conditions. In the current paper, numerical simulations are conducted to investigate the flow features in a LP steam turbine. In steady calculations, flows under six different mass flow rates are simulated. Performances and flow patterns in last stage rotor (LSR) in low mass flow rates are highlighted. Since the last stage is modeled as a full blade annulus, flow patterns and blade force in circumferential distribution are examined. Results show that under low mass flow rate conditions, vortices occur in the last stage and the diffuser. The LSR acts like a compressor. The periodical distributions of pressure in LSR passages are broken. High amplitude aerodynamic force fluctuations are found on LSR blades in low mass flow cases. By conducting unsteady simulations, the time series of aerodynamic force are demonstrated to have the similar trend and magnitude of that in steady spatial sequence. The mechanism for aerodynamic force excitation is discussed in the current paper. Unsteady pressure fluctuation in tip section of LSR at low mass flow rates seems to have a significant correlation with the aerodynamic force fluctuation level rise. Copyright © 2015 by ASME.

Liu L.,Shanghai JiaoTong University | Zhou D.,Shanghai Turbine Works Co. | Liu H.,Shanghai JiaoTong University | Zhu X.,Shanghai JiaoTong University | Du Z.,Shanghai JiaoTong University
Proceedings of the ASME Turbo Expo | Year: 2015

The cooling protection of the hot end is the key technique for ultra-supercritical steam turbine to cool the hot components. In this paper, the internal flow mechanism and cooling characteristics in the tangential direction cooling channel in the intermediate pressure cylinder (IPC) are investigated using the method of computational fluid dynamics. Various turbulence models and mesh sizes are evaluated (the k-ε model, the k-ω model, the SST model). Also, calculated results of the nonrotating bottom wall are compared with the experimental results in a previous research to show the reliability of the CFD program used. Detailed predictions of the contours of velocity, pressure and temperature are carried out. The focus of this study is to investigate the effects of inlet Mach number, turbulent Prandtl number, rotational wall speed, and inlet turbulence intensity on the cooling effectiveness of the vortex channel. The inlet Mach number, the turbulent Prandtl number, the rotational wall speed and the inlet turbulence intensity varied from 0.315 to 0.512, from 0.71 to 1.0, from 0 to 3000rpm, and from 1% to 10%, respectively. Results show that the parameters have different effects on the cooling effectiveness of the vortex cooling chamber. The cooling effect of the vortex channel increases with increasing inlet Mach number and rotational wall speed, while decreases with the increasing turbulent Prandtl number. As the inlet turbulence intensity increases, the cooling effect increases firstly, and then decreases. Copyright © 2015 by ASME.

Chi Z.,Shanghai JiaoTong University | Liu H.,CAS Shanghai Advanced Research Institute | Zang S.,Shanghai JiaoTong University | Jiao G.,Shanghai Turbine Works Co.
Proceedings of the ASME Turbo Expo | Year: 2015

This paper discusses the methodology of impingement cooling optimization of a gas turbine 2nd stage vane with 3D conjugate heat transfer (CHT) CFD analysis applied. The vane is installed with a novel impingement cooling structure in the leading cavity and a pin-fin array in the trailing edge. This study involves the optimization of the impingement cooling structure, including the location of the jet holes and the diameter of each hole. The generation of 3D model and CHT mesh was realized using an in-house code developed specifically for turbine cooling optimization. A constant pressure drop was assumed within the cooling system during optimization. To make the optimization computationally faster, a metamodel which can predict the detailed distribution of metal temperature on the vane surface was used in the second-level search together with a genetic algorithm. An optimal nonuniform impingement cooling structure in the leading cavity was automatically designed by the optimization process costing only dozens of CFD runs, which provided a more uniform temperature distribution on the vane surface and required no more coolant amount compared with the initial impingement cooling structure. © Copyright 2015 by ASME.

Ren W.,Shanghai JiaoTong University | Lu F.,Shanghai JiaoTong University | Yang R.,Shanghai Turbine Works Company | Liu X.,Shanghai Turbine Plant of Shanghai Electrical Power Generation Equipment Co. | Li Z.,Shanghai JiaoTong University
Journal of Materials Processing Technology | Year: 2015

Abstract Liquation cracking in the fiber laser welding Inconel 617 joint under different heat input and preheating conditions was systemically investigated. Liquation cracking is prevalent in the necking region of the welded fusion zone. The liquation of the grain boundaries (GBs) is mainly caused by the constitutional liquation of M23(C,B)6 carbides. The continuous (Cr, Mo)-rich phase is re-solidified due to the continuous liquid film along GBs during the solidification. The continuous (Cr, Mo)-rich phase decreases as the heat input and preheating temperature increases. The presence of the GB resolidified phase around liquation cracking is one of the features in the formation of liquation cracking. As well as, liquation cracking in heat affected zone (HAZ) would also decrease with increasing heat input and preheating temperature in the fiber laser welding of Inconel 617. © 2015 Elsevier B.V.

Liu W.,Shanghai JiaoTong University | Lu F.,Shanghai JiaoTong University | Yang R.,Shanghai Turbine Works Company | Tang X.,Shanghai JiaoTong University | Cui H.,Shanghai JiaoTong University
Journal of Materials Processing Technology | Year: 2015

Five kinds of thermal cycle, with different peak temperatures ranging between 1150 °C and 1350 °C were taken to simulate HAZs with same heating and cooling rate. The microstructure of different simulated HAZs was characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The micro-hardness, grain size and tensile test at 750 °C of simulated HAZs were conducted. Coarsened carbides along the grain boundaries are observed in the HAZs simulated at 1200 °C and 1250 °C. For the HAZs simulated at 1300 °C and 1350 °C, the carbides inside grains vanish, and continuous lamellar structure occurs at the grain boundaries. The microstructure of HAZ simulated at 1150 °C is similar to that of base metal (BM). The micro-hardness and average grain size of simulated HAZs have no obvious variation compared to the BM. Tensile test results show that the yield stress (YS) and ultimate tensile stress (UTS) decrease as simulation peak temperature increases, which attributes to the coarsened carbides and continuous lamellar structure occurring at the grain boundaries at higher temperature. © 2015 Elsevier B.V. All rights reserved.

Guo Q.,Shanghai JiaoTong University | Lu F.,Shanghai JiaoTong University | Cui H.,Shanghai JiaoTong University | Yang R.,Shanghai Turbine Works Company | And 2 more authors.
Journal of Materials Processing Technology | Year: 2015

Crack propagation behavior in different zones of advanced 9Cr/CrMoV dissimilar steel welded joint was simulated by ABAQUS software. The Gurson-Tvergaard-Needleman (GTN) damage model and brittle cracking model were introduced to analyze the crack propagation behavior for ductile and brittle region on the dissimilar steel welded joint, respectively. It is found that the numerically calculated J-Δa resistance curves for the ductile regions i.e., the CrMoV base metal (CrMoV-BM), the heat affected zone of CrMoV (CrMoV-HAZ) and weld metal (WM) matched the experimental results, implying the reliability of the model developed in the present study. Three cases with different initial crack length (a0) were simulated to probe into the effect of a0 on the crack propagation resistance. The simulated results revealed that higher equivalent plastic strain and stress triaxiality occurred on the right ahead of the crack tip for longer initial crack length, which induces the lower crack propagation resistance. The brittle crack propagation behavior in 9Cr base metal (9Cr-BM) and heat affected zone of 9Cr (9Cr-HAZ) was well simulated by the brittle cracking model. The local stress distribution around the crack tip before crack destabilization could be obtained from the established model for BM and HAZ of 9Cr steel. © 2015 Elsevier B.V. All rights reserved.

Ren W.,Shanghai JiaoTong University | Lu F.,Shanghai JiaoTong University | Yang R.,Shanghai Turbine Works Company | Liu X.,Shanghai Turbine Plant of Shanghai Electrical Power Generation Equipment Co. | And 2 more authors.
Materials and Design | Year: 2015

A comparative study on the influence of fiber laser welding (FLW) and CO2 laser welding (CLW) on the weld bead geometry and the microstructure of fusion zone (FZ) of Inconel 617 was investigated. In CLW joints, the weld bead geometry is Y-type shape. In FLW joints, the weld bead geometry transforms from Y-type to I-type with the decrease of the heat input. The minimum heat input required to achieve the full penetration of the weldment in FLW is lower than the CLW. The melting efficiency in FLW is higher than that in CLW. From the top to the root regions, the secondary dendrite arm spacing (SDAS) in fiber laser welded FZ undergoes a smaller change than that in CO2 laser welded FZ. The elements of Ti, Mo, Cr and Co segregate into the interdendritic regions both in FLW and CLW process. The second phases in CLW with the highest input of 360J/mm are much larger and more than ones in FLW with the highest heat input of 210.5J/mm. © 2015 Elsevier Ltd.

Cheng K.,Shanghai Turbine Works Co. | Wang G.,Shanghai Turbine Works Co. | You X.,Tsinghua University
International Conference on Power Engineering 2013, ICOPE 2013 | Year: 2013

In the design/research process for steam turbine blade, especially for the L-0 rotating blade, finite element method has been widely used and formed a relatively mature algorithm and experience. The FEA approach to solve the steady problems has been experienced in a lot of blade-engineering practices and its usability and precision has been validated and accepted. On the other hand, the true story is that the actual working process of a blade is definitely unsteady. Thus for a reliable operation a rotating blade should be designed to endure both high-cycle and low-cycle fatigue considering flow excitation and startupshutdown effect. It is really a complicated and important proposition to access an accurate estimation of the blade lifetime. Based on plenty of successful application of CAE approach for L-0 rotating blade in large capacity turbine unit, an adaptive lifetime prediction method for turbine blade is discussed in this paper. A new developed long blade with the length around 1700 mm is proposed as an analysis sample. The preliminary analysis of blade stress/strain distributions is firstly performed considering centrifugal effect and unsteady/steadyflow load. By comparing the stress field under steady flow effect and the stress field without flow load, it can be indicated that steady flow effect to the additional root stress is comparatively limited. The natural frequencies of the interlocked whole-cycle-blade are calculated under varying turbine speed including the rated speed. Moreover the dynamic vibration stress is calculated by assuming some resonant conditions with corresponding vibrating modes which are already presented in the previous analysis step. On the basis of CAE analysis, the article first conducted a nondestructive lifetime analysis of the blade. S-N and E-N methods were employed during the calculation, where changes of blade rotational speed, flow incited vibrations and different metal surfaces have all been taken into consideration. Based on this nondestructive lifetime analysis, this article chose two types of crack model to simulate the crack in its actual situation, namely using a hole-side crack under strain to simulate a round pit in the actual situation, and using a block center crack under strain to simulate a notch in the actual situation. The results show that the calculation result of the hole-side crack model is not sensitive to the hole's diameter but is very sensitive to the stress load spectrum and the initial crack size, namely, the material's fatigue fracture lifetime becomes correspondingly shorter when the initial crack size gets larger or when the peak value of stress load spectrum gets higher.

Qi M.,Beijing Institute of Technology | Yang J.,Xi'an Jiaotong University | Yang R.,Shanghai Turbine Works Co. | Yang H.,Shanghai Turbine Works Co.
Proceedings of the ASME Turbo Expo | Year: 2013

Sliding grid and dual-time step method-based unsteady flow simulation on the final two stages of a steam turbine is performed without geometry scaling. The behavior and characteristic of unsteady pressure fluctuations on the blade surfaces of stator and rotor blades are investigated in details. FFT is performed on the blade surface pressure fluctuation to estimate the region covered by the unsteady flow perturbation from upstream and downstream. Results show that for long blade turbine stage investigated, pressure loading fluctuation is significant, with the maximum amplitude being equivalent up to level of 61% pressure loading. The loading fluctuation follows the trend of increasing from hub to shroud in stator while contrary trend is followed by the rotor. Among the unsteady perturbation sources causing the significant pressure fluctuations in long blade turbine stage, trailing edge shock is the dominating one, leading significant pressure distortion along circumferential direction, which induces strong interaction on downstream blade row. Copyright © 2013 by Solar Turbines Incorporated.

Yang R.,Shanghai Turbine Works Co. | Yang J.,Shanghai Turbine Works Co.
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2016

Taking the last two-stage blades of a steam turbine low-pressure cylinder as the objects of study, the aerodynamic flow around the blades was analyzed using non-linear harmonic method, after which the distribution of unsteady aerodynamic loads on the blade surfaces was acquired. Results show that the method proposed can well capture the phenomenon of unsteady flow, such as strong unsteady flow in the diffuser of last-stage stator blade, no obvious unsteady flow in the area of blade tip, etc. The calculation results may serve as a reference for dynamic response analysis of last-stage long blades. © 2016, Editorial Department of Chinese Society of Power Engineering. All right reserved.

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