Investigation on the forced response of a radial turbine under aerodynamic excitations

Rotor blades in a radial turbine with nozzle guide vanes typically experience harmonic aerodynamic excitations due to the rotor stator interaction. Dynamic stresses induced by the harmonic excitations can result in high cycle fatigue (HCF) of the blades. A reliable prediction method for forced response issue is essential to avoid the HCF problem. In this work, the forced response mechanisms were investigated based on a fluid structure interaction (FSI) method. Aerodynamic excitations were obtained by three-dimensional unsteady computational fluid dynamics (CFD) simulation with phase shifted periodic boundary conditions. The first two harmonic pressures were determined as the primary components of the excitation and applied to finite element (FE) model to conduct the computational structural dynamics (CSD) simulation. The computed results from the harmonic forced response analysis show good agreement with the predictions of Singh's advanced frequency evaluation (SAFE) diagram. Moreover, the mode superposition method used in FE simulation offers an efficient way to provide quantitative assessments of mode response levels and resonant strength.     

A comparison of experimental and numerical studies performed on a low-pressure turbine blade cascade at high-speed conditions, low reynolds numbers and various turbulence intensities

This paper focuses on a comparison of experimental and numerical investigations performed on a low-pressure mid-loaded turbine blade at operating conditions comprised of a wide range of Mach numbers(from 0.5-1.1),Reynolds numbers(from 0.4e+5-3.0e+5),flow incidence(-15-15 degrees) and three levels of free-stream turbulence intensities(2,5 and 10%).The experimental part of the work was performed in a high-speed linear cascade wind tunnel.The increased levels of turbulence were achieved by a passive grid placed at the cascade inlet.A two-dimensional flow field at the center of the blade was traversed pitch-wise upstream and downstream the cascade by means of a five-hole probe and a needle pressure probe,respectively.The blade loading was measured using the surface pressure taps evenly deployed at the blade mid-span along the suction and the pressure side.The inlet turbulence was investigated using the constant temperature anemometer technique with a dual sensor probe.Experimentally evaluated values of turbulent kinetic energy and its dissipation rate were then used as inputs for the numerical simulations.An in-house code based on a system of the Favre-averaged Navier-Stokes equation closed by a two-equation k-turbulence model was adopted for the predictions.The code utilizes an algebraic model of bypass transition valid both for attached as for separated flows taking in account the effect of free-stream turbulence and pressure gradient.The resulting comparison was carried out in terms of the kinetic energy loss coefficient,distributions of downstream wakes and blade velocity.Additionally a flow visualization was performed by means of the Schlieren technique in order to provide a further understanding of the studied phenomena.A few selected cases with a particular interest in the attached and separated flow transition are compared and discussed.     

切出风速下风力机变桨故障叶片气动特性及准静态结构响应分析

为探究大型水平轴风力机达到切出风速停机后变桨故障叶片的气动特性及准静态结构响应,基于计算流体力学方法对NREL 5 MW风力机变桨故障/成功叶片气动侧状态进行分析,并利用双向弱流固耦合及曲屈分析对典型方位角下变桨故障叶片展开研究。结果显示：切出风速下变桨故障叶片挥舞力矩平均值为变桨成功叶片的13.8倍,且前者的流场尾迹更为明显。此外,180°方位角变桨故障叶片较之0°方位角变桨故障叶片应力及叶尖位移分别减小29.8%和32.7%,一阶屈曲因子增加20.2%。     

减小燃气轮机油气切换时的燃气压力波动

介绍了整体煤气化联合循环发电系统中燃气轮机在开车过程中燃气压力大幅度波动原因及解决方法。     

高背压汽轮机在中小型热电厂的应用

分析选用背压机排气叠置对中小型热电厂进行技术改造。以哈尔滨发电有限公司前置背压机扩建进行分析为案例。提出技术改造的可行性,以供参考。     

300 MW湿冷汽轮机双转子互换高背压供热改造应用

随着用户需求增加及国家节能减排政策要求,对亚临界300 MW湿冷汽轮机组进行高背压供热改造成为火力发电厂满足对外供热需求和提高机组效率的重要措施之一,而汽轮机在供热期和非供热期双低压转子互换是实现高背压供热改造一个行之有效的手段.以某电厂2号机300 MW机组采用双低压转子互换技术进行高背压循环水供热改造为例,简述了汽轮机在改造过程中需要考虑的主要问题及相应的改造方案.     

进口压力对燃气轮机气体燃料阀调节性能的影响及其修正补偿方法研究

燃料调节阀是精确控制燃气轮机燃料流量和机组负荷的基本组件。本文基于调节阀的位移-流量特性及其液压伺服机构组成,建立了燃料阀位置伺服系统的数学模型,分析了燃料阀组及其控制系统的动态响应特性,研究了进口压力对调节阀性能的影响,并提出了一种燃料进口压力修正补偿控制方法。仿真结果表明：经过压力修正后,系统响应频宽提高0.5 Hz,幅值裕量增大20°。     

凝汽机组背压变化对汽轮机功率影响的简化修正计算

提出了一种简化的变工况计算方法,该方法应用了汽轮机变工况理论并同时考虑了热力系统的工况变化,可较为准确的计算出在不同工况下背压对汽轮机功率的影响.并针对实际运行中背压常处于常压变化范围,采用了简化的线性化公式,对不同的工况采用不同的系数进行修正计算,以方便指导机组经济运行.     

Numerical Investigation of the Interaction between Mainstream and Tip Shroud Leakage Flow in a 2-Stage Low Pressure Turbine

The pressing demand for future advanced gas turbine requires to identify the losses in a turbine and to understand the physical mechanisms producing them. In low pressure turbines with shrouded blades, a large portion of these losses is generated by tip shroud leakage flow and associated interaction. For this reason, shroud leakage losses are generally grouped into the losses of leakage flow itself and the losses caused by the interaction between leak- age flow and mainstream. In order to evaluate the influence of shroud leakage flow and related losses on turbine performance, computational investigations for a 2-stage low pressure turbine is presented and discussed in this paper. Three dimensional steady multistage calculations using mixing plane approach were performed including detailed tip shroud geometry. Results showed that turbines with shrouded blades have an obvious advantage over unshrouded ones in terms of aerodynamic performance. A loss mechanism breakdown analysis demonstrated that the leakage loss is the main contributor in the first stage while mixing loss dominates in the second stage. Due to the blade-to-blade pressure gradient, both inlet and exit cavity present non-uniform leakage injection and extrac- tion. The flow in the exit cavity is filled with cavity vortex, leakage jet attached to the cavity wall and recircula- tion zone induced by main flow ingestion. Furthermore, radial gap and exit cavity size of tip shroud have a major effect on the yaw angle near the tip region in the main flow. Therefore, a full calculation of shroud leakage flow is necessary in turbine performance analysis and the shroud geometric features need to be considered during turbine design process.     

A Tomo‐PIV study of the effects of freestream turbulence on stall delay of the blade of a horizontal‐axis wind turbine

Volumetric velocity fields were measured using tomographic particle image velocimetry on a model of the blade of a 5 kW horizontal‐axis wind turbine to study the effects of freestream turbulence levels (FTLs) at 0.4%, 4% and 13% on stall delay phenomenon at two different global tip speed ratios of 3 and 5 with Reynolds number (Re) ? 5000. Static pressures were measured, and results illustrated that FTL has stronger effect on the surface pressures of the static airfoil. Magnitudes of the absolute velocities within the separated flows above the static airfoil's suction surface increase significantly with higher FTL, while the changes of these velocities above the rotating blade's surface are less obvious. Radial flows from rotating blade's root to tip were also observed with strong spanwise velocity component located in the vicinities of the vortices. At the root and middle sections of the rotating blade, the flows with strong radial velocity component, w, become wider with higher FTL near to the rotating blade's leading edge when the angles of attack (AOAs) are large. At large AOAs, the strength and size of the vortices shed from the rotating blade's leading and trailing edges decrease significantly with higher FTL. However, at small AOAs, the size and coherence of the vortices near the rotating blade's trailing edge increase significantly with higher FTL. Surface streamlines of the rotating blade illustrated that at the rotating blade's root region and at large AOAs, the streamlines tend to lean toward the rotating blade's trailing edge at higher FTL. Copyright © 2014 John Wiley & Sons, Ltd.     

A new method of predicting the saturation pressure of oil reservoir and its application

Saturation pressure is a vital parameter of oil reservoir which can reflect the oilfield characteristics and determine the oilfield development process, and it is determined by experiments in the laboratory in general. However, there was only one well with saturation pressure test in this target reservoir, and it is necessary to determine whether this parameter is right or not.In this work, we present a new method for quickly determining saturation pressure using machine learning algorithms, including random forest regressor (RF), support vector machine (SVM), decision trees (DT), and artificial neural network (ANN or NN). Using these approaches, saturation pressure was obtained by using the initial solution gas-oil ratio (GOR), temperature, API gravity and other reservoir-fluid data available in the oilfields. Compared with the empirical formula for saturation pressure calculation, the calculated result shows that the accuracy given from machine learning is higher than that from other formulas at home and abroad, and has a good match with the lab test. On the basis of the calculated saturation pressure, it can determine whether the reservoir enters into the stage of dissolved gas drive or not, which also provides the basis for maintaining the reservoir pressure by water injection in advance, rational development decision-making and work over measures.This approach above can provide technical guidance for predicting the saturation pressure in the development of different kinds of reservoirs, including the sandstone reservoirs and carbonate reservoirs.     

Numerical study of combining steady Vortex Generator Jets and Deflected Trailing edge to reduce the blade numbers of low pressure turbine stage

A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge (VGJs-DT) to decrease the low pressure turbine (LPT) blade numbers was presented. The effects of VGJs-DT on energy loss and flow of low solidity low pressure turbine (LSLPT) cascades were studied. VGJs-DT was found to decrease the energy loss of LSLPT cascade and increase the flow turning angle. VGJs-DT decreased the solidity by 12.5% without a significant increase in energy loss. VGJs-DT was more effective than steady VGJs. VGJs-DT decreased the energy loss and increased the flow angle of the LSLPT cascade with steady VGJs. VGJs-DT can use 50% less mass flow than steady VGJs to inhibit the flow separation in the LSLPT cascade. The deflected trailing edge enhanced the ability of steady VGJs to resist flow separation. Overall, VGJs-DT can be used to control flow separation in LPT cascade and reduce the blade numbers of low pressure turbine stage.     

A fast non-iterative method for the evaluation of the thermal response of wall elements

This paper describes the theoretical development and numerical solution of a non-iterative scheme for the calculation of the thermal response of all elements. The method considers the effect of the variation in external surface temperature, thermal resistance and heat capacity on the internal temperature of a heat storage zone. The method offers potential saving in computation time, in comparison to finite difference methods, without any loss in the accuracy of the computation.     

A TEST RIG FOR THE REALIZATION OF WATER RECOVERY IN A STEAM-INJECTED GAS TURBINE

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Investigations of Interaction of the Main Flow with Root and Tip Leakage Flows in an Axial Turbine Stage by Means of a Source／Sink Approach for a 3D Navier—Stokes Solver

IntroductionFundamental stUdies of losses in tUrbomachinery in-dicate that, besides giving rise to losses of work, leakageflows contribute to the overall creation of entropy andkinetic encrgy losses. Some entropy is created in thelabyrinth seals and in passages between the fixed androtating pats of turbomachinery. CFD computations inlabyrinth seal geometries enable the evaluation of theentropy ereation PrOCesses there. CFD-based analysis canm1nindze the mass fiow rates of the tip leakage a…     

燃气轮机技术信息传递网站的建立方案及实施

介绍南京汽轮电机集团公司利用Asp.NetI、IS组件及数据库技术开发网站系统,用于报道、接收和传递燃气轮机跨国技术信息,同时实现与企业内部原有IBM Domino平台上的E-Mail邮件系统、OA办公系统的紧密融合。     

Prediction of seismic loadings on wind turbine support structures by response spectrum method considering equivalent modal damping of support structures and reliability level

In this study, a new damping correction factor is proposed to provide an accurate design response spectrum for megawatt (MW) class wind turbines. The predicted response spectra show good agreement with those by time history analysis (THA). An equivalent modal damping of wind turbine support structures is then proposed for response spectrum method (RSM) based on the modal decomposition method for non‐classically damped structures. Seismic loadings on wind turbine towers and footings by RSM with the proposed damping correction factor and equivalent modal damping are also investigated and compared with those by THA. Finally, a quantile value between 0.5 and 0.85 in the damping correction factor is calibrated to ensure the same reliability level as evaluated by THA currently used for estimation of seismic loadings on support structures.     

百千瓦中型变速变桨风电机组叶片设计研究

百千瓦级叶片一般采用定桨方式运行,依靠叶片失速进行功率控制,机组运行过程中无法维持较高的效率。基于100 kW变速变桨机组的运行特征,提出了一种100 kW级中型叶片的设计方法。气动设计采用了BEM方法,利用Harp_opt中的优化算法获得较高的气动性能;结构及载荷设计参考IEC标准进行,采用Focus进行铺层设计及结构特性分析。所设计叶片的长度为10.029 m左右,极限及疲劳载荷特性满足GL IIA类风场的运行要求。     

A fast classification method of retired electric vehicle battery modules and their energy storage application in photovoltaic generation

The fading characteristics of 60 Ah decommissioned electric vehicle battery modules were assessed employing capacity calibration, electrochemical impedance spectroscopy, and voltage measurement of parallel bricks inside modules. The correlation between capacity and internal resistance or voltage was analyzed. Then, 10 consistent retired modules were packed and configured in a photovoltaic (PV) power station to verify the practicability of their photovoltaic energy storage application. The results show that the capacity attenuation of most retired modules is not severe in a pack while minor modules with state of health (SOH) less than 80% bring about the retirement of the whole pack as a result of the buckets effect. There is no obvious correlation between capacities of retired battery modules and their lithium-ion diffusion coefficients or charge transfer resistance or ohmic resistance, whose reliability is low as the consistency indexes of decommissioning battery modules. The maximum off load voltage difference ΔU_max at low state of charge (SOC) values has a good negative linear correlation with the capacity of retired modules, suggesting that the ΔU_max value at low SOC values can be considered as a characteristic index for fast classification of retired battery modules for large-scale second-life application. A PV power station equipped with retired battery energy storage system (RBESS) can maximize the photovoltaic self-utilization rate. It is an important way to reutilization of retired battery that RBESSs are configured with distributed PV power stations.     

涡轮盘-片耦合场及接触问题建模与分析的新方法

针对某燃气轮机盘-片,运用存储与导入的思想提出了一套耦合场及接触问题的建模和分析的新方法。文中采用PRO／E建立了轮盘和叶片的三维实体模型,并结合ANSYS软件建立了其耦合场及接触有限元模型,详细介绍了该问题的有限元分析方法。文章最后给出了算例,其分析结果证明了文中的建模及分析方法是较好的适合工程应用的新方法。