Investigations Into Aerodynamic Performance of Turbine Stages With Flexible Shroud Seals

2020 ◽  
Author(s):  
Xin Yan ◽  
Yabo Wang ◽  
Kang Zhang ◽  
Xinbo Dai ◽  
Kun He
Keyword(s):  
Steam Turbine ◽  
Flow Patterns ◽  
Aerodynamic Performance ◽  
Original Design ◽  
Flow Angle ◽  
Large Power ◽  
Aerodynamic Efficiency ◽  
Forward Bending ◽  
Outlet Flow ◽  
Reaction Degree

Abstract The present paper utilizes a numerical method to investigate the effect of flexible shroud seals, including the forward bending flexible seals and backward bending flexible seals, on aerodynamic performance of high pressure steam turbine stages. At first, the wear performance of flexible seal is analyzed with the Finite Element Analysis method. It shows that wear in flexible strip is so small that only the installation clearance needs to be considered in operation process. Then, by replacing the labyrinth shroud seals with flexible shroud seals, the aerodynamic efficiency, outlet flow angle distributions, and reaction degree distributions in two-stages are obtained. At three installation clearances, interactions between leakage flow and main flow, as well as the flow patterns in flexible shroud seals, are visualized and also compared with the original design case. The numerical results indicate that turbine stages configured with forward bending flexible shroud seals have a very close aerodynamic performance to those configured with conventional labyrinth shroud seals at the same clearance, whereas the turbine stages configured with backward bending flexible seals have lower total-total isentropic efficiency than those with conventional labyrinth shroud seals. By replacing the conventional labyrinth shroud seals with forward bending flexible shroud seals (at the same clearance), the aerodynamic efficiency, outlet flow angles, limiting streamlines, secondary flow patterns in shroud region and reaction degree distributions in stages are almost not affected. Since the forward bending flexible seal allows relatively smaller installation clearance than the conventional labyrinth seal, application of this kind of seal in rotor blade tip gap is much beneficial to achieve lower leakage rate and higher aerodynamic performance in large power steam turbine stages.

Effects of Labyrinth Fin Wear on Aerodynamic Performance of Turbine Stages: Part I — Bending Damages

2019 ◽  
Author(s):  
Xin Yan ◽  
Xinbo Dai
Keyword(s):  
Labyrinth Seal ◽  
Flow Fields ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Original Design ◽  
Labyrinth Seals ◽  
Sealing Performance ◽  
Forward Bending ◽  
Design Case ◽  
Isentropic Efficiency

Abstract Labyrinth seals are widely applied in turbo machines because of their geometrical simplicity, convenient installation, reliable operation and excellent sealing performance. However, in realistic operation process, they usually encounter transient conditions (starting-up, shutting down, etc.) and unavoidable vibrations, which may cause wear in the labyrinth fins. After rubbing, the sealing performance of labyrinth seal will be varied in contrast to the original design. Correspondingly, the aerodynamic efficiency of the turbine stage will be affected by the variation of leakage flow in rubbing process. However, in published literature with respect to the labyrinth seal wear, most of the attention has been paid on revealing sealing performance degradation of labyrinth seal itself. Few studies have been concentrated on the influence of labyrinth seal wear on aerodynamic performance of turbine stages. In such background, the present paper utilizes the numerical methods to investigate the effects of labyrinth seal bending damages on aerodynamic performance of turbine stages. Firstly, under several assumptions, the bending geometrical model was established to describe different degrees of bending damages. Secondly, using three-dimensional RANS simulations, the effects of effective clearance variation due to bending on leakage flow and flow fields in turbine stages were investigated. The overall performance of the turbine stages with teeth-bending damages was also compared with the original design case. The influence of the forward bending and backward bending of labyrinth seals were analyzed and compared with each other. The total-total isentropic efficiency of turbine stages, leakage rates, outlet flow angles, reaction degrees and profile static pressure distributions, entropic distributions and flow fields in seals were obtained and compared to the original design case. The results indicate that the leakage rates in the worn labyrinth seal are quite relevant to the effective clearance, especially for the backward bending damages. As the effective clearances in backward bending cases are increased by 0.2–0.6mm, the isentropic efficiency of turbine stages is decreased by about 1–2%. However, for the forward bending damages, the aerodynamic performance and leakage rates in turbine stages are not sensitive to the effective clearance.

Numerical and Experimental Investigation of Axial Gap Variation in High-Pressure Steam Turbine Stages

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
Nicola Maceli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Flow Angle ◽  
High Pressure Steam ◽  
Aspect Ratios ◽  
Pressure Steam ◽  
The Impact

This work aims at investigating the impact of axial gap variation on aerodynamic performance of a high-pressure steam turbine stage. Numerical and experimental campaigns were conducted on a 1.5-stage of a reaction steam turbine. This low speed test rig was designed and operated in different operating conditions. Two different configurations were studied in which blades axial gap was varied in a range from 40% to 95% of the blade axial chord. Numerical analyses were carried out by means of three-dimensional, viscous, unsteady simulations, adopting measured inlet/outlet boundary conditions. Two sets of measurements were performed: steady measurements, from one hand, for global performance estimation of the whole turbine, such as efficiency, mass flow, and stage work; steady and unsteady measurements, on the other hand, were performed downstream of rotor row, in order to characterize the flow structures in this region. The fidelity of computational setup was proven by comparing numerical results to measurements. Main performance curves and spanwise distributions have shown a good agreement in terms of both shape of curves/distributions and absolute values. Moreover, the comparison of two-dimensional maps downstream of rotor row has shown similar structures of the flow field. Finally, a comprehensive study of the axial gap effect on stage aerodynamic performance was carried out for four blade spacings (10%, 25%, 40%, and 95% of S1 axial chord) and five aspect ratios (1.0, 1.6, 3, 4, and 5). The results pointed out how unsteady interaction between blade rows affects stage operation, in terms of pressure and flow angle distributions, as well as of secondary flows development. The combined effect of these aspects in determining the stage efficiency is investigated and discussed in detail.

Direct Constrained Computational Fluid Dynamics Based Optimization of Three-Dimensional Blading for the Exit Stage of a Large Power Steam Turbine

2002 ◽  
Vol 125 (1) ◽  
pp. 385-390 ◽  
Author(s):  
P. Lampart ◽  
S. Yershov
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Steam Turbines ◽  
Original Design ◽  
Large Power ◽  
Wide Range

The paper describes results of direct constrained optimization using Nelder-Mead’s method of deformed polyhedron and a Reynolds-averaged Navier-Stokes (RANS) solver to optimize the shape of three-dimensional blading for the exit stage of a large power steam turbine. The computations of the flowfield in the stator and rotor are compressible, viscous, and three-dimensional. Turbulence effects are taken into account using the modified model of Baldwin-Lomax. The objective function is the stage efficiency, with the exit energy considered a loss, and with constraints imposed on the mass flow rate in the form of a penalty function if the mass flow rate falls beyond the required range. The blade sections (profiles) are assumed not to change during the optimization. Two optimization tasks are reported in this paper, first—optimizing the stator straight and compound circumferential lean, and also stator and rotor stagger angles to keep the flow rate unchanged, giving a total number of optimized parameters equal to 5; second—optimizing the stator straight and compound axial sweep, also with stator and rotor stagger angles, also giving five optimized parameters. The process of optimization is carried out for a nominal load; however, due to the fact that exit stages of steam turbines operate over a wide range of flow rates away from the nominal conditions, the original and final geometries are also checked for low and high loads. The process of optimization gives new designs with new three-dimensional stacking lines of stator blades, and with significantly increased efficiencies, compared to the original design, at least for a larger part of the assumed range of load.

The Effect of Reynolds Number and Turbulence Intensity on the Performance of a Compressor Cascade with Prescribed Velocity Distribution

1977 ◽  
Vol 19 (3) ◽  
pp. 93-100 ◽  
Author(s):  
J. Citavy ◽  
J. F. Norbury
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Axial Velocity ◽  
Separation Bubble ◽  
Velocity Ratio ◽  
Aerodynamic Performance ◽  
Substantial Effect ◽  
Compressor Cascade ◽  
Flow Angle ◽  
Outlet Flow

Experimental results are presented on the effect of Reynolds number ( Re) and turbulence intensity ( Tu) on the aerodynamic performance of a PVD compressor cascade at design incidence. The pressure distribution, outlet flow angle and losses were measured within the ranges Re = 0.6 times 105 to 2 times 105 and Tu = 0.35 to 4.4 per cent. In some experiments, the effect of axial velocity ratio ( AVR) was investigated. A substantial effect of the Reynolds number and turbulence intensity on the growth and bursting of the separation bubble was observed, with consequent effects on the aerodynamic performance of the cascade. The bursting of the bubble also gave rise to a hysteresis effect with Reynolds number.

Numerical and Experimental Investigation of Axial Gap Variation in High Pressure Steam Turbine Stages

2016 ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
Nicola Maceli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Flow Angle ◽  
High Pressure Steam ◽  
Aspect Ratios ◽  
Pressure Steam ◽  
The Impact

This work aims at investigating the impact of axial gap variation on aerodynamic performance of a high-pressure steam turbine stage. Numerical and experimental campaigns were conducted on a 1.5-stage of a reaction steam turbine. This low speed test rig was designed and operated in different operating conditions. Two different configurations were studied, in which blades axial gap was varied in a range from 40% to 95% of the blade axial chord. Numerical analyses were carried out by means of three-dimensional, viscous, unsteady simulations, adopting measured inlet/outlet boundary conditions. Two set of measurements were performed. Steady measurements, from one hand, for global performance estimation of the whole turbine, such as efficiency, mass flow, stage work. Steady and unsteady measurements, on the other hand, were performed downstream of rotor row, in order to characterize the flow structures in this region. The fidelity of computational setup was proven by comparing numerical results to measurements. Main performance curves and span-wise distributions shown a good agreement in terms of both shape of curves/distributions and absolute values. Moreover, the comparison of two dimensional maps downstream of rotor row shown similar structures of the flow field. Finally, a comprehensive study of the axial gap effect on stage aerodynamic performance was carried out for four blade spacings (10%, 25%, 40% and 95% of S1 axial chord), and five aspect ratios (1.0, 1.6, 3, 4 and 5). The results pointed out how unsteady interaction between blade rows affects stage operation, in terms of pressure and flow angle distributions, as well as of secondary flows development. The combined effect of these aspects in determining the stage efficiency is investigated and discussed in detail.

Multi Disciplinary Design Optimization and Performance Evaluation of a Single-Stage Transonic Axial Compressor

2012 ◽  
Author(s):  
Young-Seok Kang ◽  
Tae-Choon Park ◽  
Soo-Seok Yang ◽  
Sae-Il Lee ◽  
Dong-Ho Lee
Keyword(s):  
Safety Factor ◽  
Incidence Angle ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Design Constraints ◽  
Flow Angle ◽  
Blade Loading ◽  
Final Design ◽  
Outlet Flow ◽  
Transonic Axial Compressor

The multi-disciplinary optimization (MDO) method, which integrates aerodynamic performance and structural stability, was utilized in the development of a single-stage transonic axial compressor. Numerical simulations and compressor tests were also carried out to evaluate the aerodynamic performance and safety factor of the optimized compressor. The rotor has 60 design parameters with twelve most sensitive design variables selected for design optimization. The stator was redesigned according to the rotor outlet flow angle variation to match the stator incidence angle by −1∼0 degrees, while maintaining the stage outlet flow angle. The design goal is to maximize both the stage efficiency and the safety factor from the baseline scratch compressor design. The object function is composed of the normalized efficiency and safety factor with weight factors. Initially, an approximation model was created to search for the global optimization within given ranges of variables and considering several design constraints. The genetic algorithm was used to explore the Pareto front of the optimization to find the maximum objective function values. The final design was chosen after a second stage gradient-based optimization process to improve the accuracy of the optimization. The CFD results showed that more blade loading is burden to the hub region by increasing the incidence angle. The fore part blade loading gradually decreases along the span-wise direction. In addition, normal shock, which spreads along the hub to the blade tip, is confined in the rotor flow passage and pressure surface shock coincidence point moves to be closer to the blade leading edge, indicating an increase in the amount of blade loading. FEA analyses showed that the blade root stress has been drastically relieved, because the optimized blade has trapezoid-shaped hub design relative to the baseline design. The final design achieved efficiency gain of 3.69% and showed a higher safety factor by 2.3 times relative to the baseline model, while maintaining its stage mass flow rate and total-to-total pressure within the design constraints. The compressor performance test data showed good agreement with the optimized design and CFD results. However, there is room for improvement in the optimization process to reflect off-design performance so as to secure more stable compressor operation ranges.

Numerical Investigations on Aerodynamic Performance of Nozzle Control Stage of a 600MW Steam Turbine Under Different Backing Pressure Conditions

2011 ◽  
Author(s):  
Gangyun Zhong ◽  
Jun Li ◽  
Zhigang Li ◽  
Xin Yan ◽  
Qilin Wu
Keyword(s):  
Steam Turbine ◽  
Control Valve ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Computational Domain ◽  
Aerodynamic Efficiency ◽  
Control Stage ◽  
Backing Pressure ◽  
Partial Admission

Partial admission aerodynamic performance of a nozzle control stage for a 600MW steam turbine was numerically investigated using the Reynolds-Averaged Navier-Stokes (RANS) solutions. Two inlet main steam pipe, four control valves, four nozzle groups including strengthening ribs and full stator blades, and full rotor blades were considered in the present computational domain. The partial admission with three control vales opening and the fourth control valve closed under five different backing pressures were calculated to analyze the aerodynamic efficiency and total pressure losses distributions. The maximum aerodynamic efficiency of the nozzle control stage was obtained at five different backing pressure operating conditions. The flow fields in the nozzle control stage at specified backing pressure with consideration of the partial admissions effects were also illustrated.

Integrated Optimization Design for a Radial Turbine Wheel of a 100kW-Class Microturbine

2011 ◽  
Author(s):  
Lei Fu ◽  
Yan Shi ◽  
Qinghua Deng ◽  
Huaizhi Li ◽  
Zhenping Feng
Keyword(s):  
Optimization Design ◽  
Design Method ◽  
Aerodynamic Performance ◽  
Original Design ◽  
Element Analysis ◽  
Turbine Wheel ◽  
Strength Performance ◽  
Integrated Optimization ◽  
Radial Turbine ◽  
Integrated Optimization Design

The aerodynamic performance, structural strength and wheel weight are three important factors in the design process of the radial turbine. This paper presents an investigation on these aspects and develops an optimization design approach for radial turbine with consideration of the three factors. The aerodynamic design for the turbine wheel with inlet diameter of 230mm for 100kW-class microturbine unit is carried out firstly as the original design. Then, the cylinder parabolic geometrical design method is applied to the wheel modeling and structural design, but the maximum stress predicted by Finite Element Analysis greatly exceeds the yield limit of material. Furthermore, the wheel weight is above 7.2kg thus bringing some critical difficulties for bearing design and turbine operation. Therefore, an integrated optimization design method for radial turbine is studied and developed in this paper with focus on the wheel design. Meridional profiles and shape lines of turbine wheel are optimized with consideration of the whole wheel weight. Main structural modeling parameters are reselected to reduce the wheel weight. Trade-off between aerodynamic performance and strength performance is highly emphasized during the optimization design. The results show that the optimized turbine wheel gets high aerodynamic performance and acceptable stress distribution with the weight less than 3.8kg.

Degradation of Aerodynamic Performance of an Intermediate-Pressure Steam Turbine Due to Erosion of Nozzle Guide Vanes and Rotor Blades

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Koichi Yonezawa ◽  
Tomoki Kagayama ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Steam Turbine ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Flow Angle ◽  
Guide Vanes ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Deteriorations of nozzle guide vanes (NGVs) and rotor blades of a steam turbine through a long-time operation usually decrease a thermal efficiency and a power output of the turbine. In this study, influences of blade deformations due to erosion are discussed. Experiments were carried out in order to validate numerical simulations using a commercial software ANSYS-cfx. The numerical results showed acceptable agreements with experimental results. Variation of flow characteristics in the first stage of the intermediate pressure steam turbine is examined using numerical simulations. Geometries of the NGVs and the rotor blades are measured using a 3D scanner during an overhaul. The old NGVs and the rotor blades, which were used in operation, were eroded through the operation. The erosion of the NGVs leaded to increase of the throat area of the nozzle. The numerical results showed that rotor inlet velocity through the old NGVs became smaller and the flow angle of attack to the rotor blade leading edge became smaller. Consequently, the rotor power decreased significantly. Influences of the flow angle of at the rotor inlet were examined by parametric calculations and results showed that the angle of attack was an important parameter to determine the rotor performance. In addition, the influence of the deformation of the rotor blade was examined. The results showed that the degradation of the rotor performance decreased in accordance with the decrease of blade surface area.

scholarly journals Biomechanics of the unique pterosaur pteroid

2009 ◽  
Vol 277 (1684) ◽  
pp. 1121-1127 ◽  
Author(s):  
Colin Palmer ◽  
Gareth J. Dyke
Keyword(s):  
Leading Edge ◽  
Aerodynamic Performance ◽  
Biomechanical Analysis ◽  
Aerodynamic Efficiency ◽  
Fourth Finger ◽  
Forward Part ◽  
The Way

Pterosaurs, flying reptiles from the Mesozoic, had wing membranes that were supported by their arm bones and a super-elongate fourth finger. Associated with the wing, pterosaurs also possessed a unique wrist bone—the pteroid—that functioned to support the forward part of the membrane in front of the leading edge, the propatagium. Pteroid shape varies across pterosaurs and reconstructions of its orientation vary (projecting anteriorly to the wing leading edge or medially, lying alongside it) and imply differences in the way that pterosaurs controlled their wings. Here we show, using biomechanical analysis and considerations of aerodynamic efficiency of a representative ornithocheirid pterosaur, that an anteriorly orientated pteroid is highly unlikely. Unless these pterosaurs only flew steadily and had very low body masses, their pteroids would have been likely to break if orientated anteriorly; the degree of movement required for a forward orientation would have introduced extreme membrane strains and required impractical tensioning in the propatagium membrane. This result can be generalized for other pterodactyloid pterosaurs because the resultant geometry of an anteriorly orientated pteroid would have reduced the aerodynamic performance of all wings and required the same impractical properties in the propatagium membrane. We demonstrate quantitatively that the more traditional reconstruction of a medially orientated pteroid was much more stable both structurally and aerodynamically, reflecting likely life position.

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