Unsteady Forces of Rotor Blades in Full and Partial Admission Turbines

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Narmin Baagherzadeh Hushmandi ◽  
Jens E. Fridh ◽  
Torsten H. Fransson
Keyword(s):  
Pressure Field ◽  
Dynamic Pressure ◽  
Turbine Blades ◽  
Leading Edge ◽  
Rotational Frequency ◽  
Rotor Blades ◽  
Computational Domain ◽  
Unsteady Forces ◽  
Partial Admission ◽  
Unsteady Force

A numerical and experimental study of partial admission in a low reaction two-stage axial air test turbine is performed in this paper. In order to model one part load configuration, corresponding to zero flow in one of the admission arcs, the inlet was blocked at one segmental arc, at the leading edge of the first stage guide vanes. Due to the unsymmetrical geometry, the full annulus of the turbine was modeled numerically. The computational domain contained the shroud and disk cavities. The full admission turbine configuration was also modeled for reference comparisons. Computed unsteady forces of the first stage rotor blades showed cyclic change both in magnitude and direction while moving around the circumference. Unsteady forces of first stage rotor blades were plotted in the frequency domain using Fourier analysis. The largest amplitudes caused by partial admission were at first and second multiples of rotational frequency due to the existence of single blockage and change in the force direction. Unsteady forces of rotating blades in a partial admission turbine could cause unexpected failures in operation; therefore, knowledge about the frequency content of the unsteady force vector and the related amplitudes is vital to the design process of partial admission turbine blades. The pressure plots showed that the nonuniformity in the static pressure field decreases considerably downstream of the second stage’s stator row, while the nonuniformity in the dynamic pressure field is still large. The numerical results between the first stage’s stator and rotor rows showed that the leakage flow leaves the blade path down into the disk cavity in the admitted sector and re-enters downstream of the blocked channel. This process compensates for the sudden pressure drop downstream of the blockage but reduces the momentum of the main flow.

Unsteady Forces of Rotor Blades in Full and Partial Admission Turbines

2010 ◽  
Author(s):  
Narmin Baagherzadeh Hushmandi ◽  
Jens E. Fridh ◽  
Torsten H. Fransson
Keyword(s):  
Pressure Field ◽  
Dynamic Pressure ◽  
Turbine Blades ◽  
Leading Edge ◽  
Rotational Frequency ◽  
Main Flow ◽  
Rotor Blades ◽  
Computational Domain ◽  
Unsteady Forces ◽  
Partial Admission

A Numerical and experimental study of partial admission in a low reaction two-stage axial air test turbine is performed in this paper. In order to model one part load configuration, corresponding to zero flow in one of the admission arcs, the inlet was blocked at one segmental arc, at the leading edge of the first stage guide vanes. Because of the unsymmetrical geometry, the full annulus of the turbine was modeled numerically. The computational domain contained the shroud and disc cavities. The full admission turbine configuration was also modeled for reference comparisons. Computed unsteady forces of the first stage rotor blades showed cyclic change both in magnitude and direction while moving around the circumference. Unsteady forces of first stage rotor blades were plotted in frequency domain using Fourier analysis. The largest amplitudes caused by partial admission were at first and second multiples of rotational frequency due to the existence of single blockage and change in the force direction. Unsteady forces of rotating blades in a partial admission turbine could cause unexpected failures in operation; therefore knowledge about the frequency content of the unsteady force vector and the related amplitudes is vital in the design process of partial admission turbine blades. Pressure plots showed that the non-uniformity in the static pressure field decrease considerably downstream the second stage stator row, while the non-uniformity in the dynamic pressure field is still large. Numerical results between the first stage stator and rotor rows showed that the leakage flow leave the blade path down to the disc cavity in the admitted channel and re-enter into the main flow in the blocked channel. This process compensate the sudden pressure drop downstream the blockage but reduce the momentum of the main flow.

On the Prediction of Unsteady Forces on Gas Turbine Blades: Part 2—Analysis of the Results

1992 ◽  
Vol 114 (1) ◽  
pp. 123-131 ◽  
Author(s):  
T. Korakianitis
Keyword(s):  
Potential Flow ◽  
Turbine Blades ◽  
Interaction Mechanism ◽  
Rotor Blades ◽  
Unsteady Forces ◽  
Flow Angle ◽  
Gas Turbine Blades ◽  
Flow Interaction ◽  
Unsteady Force ◽  
Outlet Flow

This article investigates the generation of unsteady forces on turbine blades due to potential-flow interaction and viscous-wake interaction from upstream blade rows. A computer program is used to calculate the unsteady forces on the rotor blades. Results for typical stator-to-rotor-pitch ratios and stator outlet-flow angles show that the first spatial harmonic of the unsteady force may decrease for higher stator-to-rotor-pitch ratios, while the higher spatial harmonics increase. This (apparently counterintuitive) trend for the first harmonic, and other blade row interaction issues, are explained by considering the mechanisms by which the viscous wakes and the potential-flow interaction affect the flow field. The interaction mechanism is shown to vary with the stator-to-rotor-pitch ratio and with the outlet flow angle of the stator. It is also shown that varying the axial gap between rotor and stator can minimize the magnitude of the unsteady part of the forces generated by the combined effects of the two interactions.

scholarly journals Flutter Behavior of Highly Flexible Two- and Three-bladed Wind Turbine Rotors

2021 ◽  
Author(s):  
Mayank Chetan ◽  
Shulong Yao ◽  
D. Todd Griffith
Keyword(s):  
Wind Turbine ◽  
Structural Design ◽  
Comprehensive Evaluation ◽  
Turbine Blades ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Flutter Speed ◽  
Cost Of Energy ◽  
Manufacturing Technologies

Abstract. With the progression of novel design, material, and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the Levelized Cost of Energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to aero-elastic instabilities due to their long, slender, highly flexible nature, and this effect is accentuated as rotors further grow in size. In addition to the trend of larger rotors, new rotor concepts are emerging including two-bladed rotors and downwind configurations. In this work, we introduce a comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two-bladed, downwind rotors. Flutter speed trends and characteristics for a series of both two- and three-bladed rotors are analyzed and compared in order to illustrate the flutter behavior of two-bladed rotors relative to more well-known flutter characteristics of three-bladed rotors. In addition, we examine the important problem of blade design to mitigate flutter and present a solution to mitigate flutter in the structural design process. A study is carried out evaluating the effect of leading edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass.

Subsonic Stall Flutter of a Linear Turbine Blade Cascade Using Experimental and CFD Analysis

2020 ◽  
Author(s):  
Vaclav Slama ◽  
Bartolomej Rudas ◽  
Jiri Ira ◽  
Ales Macalka ◽  
Petr Eret ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Leading Edge ◽  
Travelling Wave ◽  
Computational Domain ◽  
Steam Turbines ◽  
Suction Surface ◽  
Blade Cascade ◽  
Stall Flutter

Abstract Stall flutter of long blades influences the operation safety of the large steam turbines in off-design conditions. As angles of attack are typically high, a partial or complete separation of the flow from the blade surface occurs. The prediction of stall flutter of turbine blades is a crucial task in the design and development of modern turbomachinery units and reliable design tools are necessary. In this work, aerodynamic stability of a linear turbine blade cascade is tested experimentally at high angle of attack +15°, Ma = 0.2 and the reduced frequency of 0.38. Controlled flutter testing has been performed in a travelling wave mode approach for the torsion with the motion amplitude of 0.5°. In addition, ANSYS CFX with SST k-ω turbulent model is used for URANS simulations of a full-scale computational domain. A separation bubble formed on suction surface near the leading edge has been found in CFD results for each blade. Excellent agreement between the experimental and numerical results in stability maps has been achieved for this case under investigation. This is encouraging and both experimental and numerical techniques will be tested further.

Unsteady Force Measurement for a Beam Using Small Piezoelectric End Sensors

2014 ◽  
Author(s):  
Margalit Z. Goldschmidt ◽  
Michael L. Jonson ◽  
George A. Lesieutre
Keyword(s):  
Lift Force ◽  
Experimental Validation ◽  
Pressure Field ◽  
Force Measurement ◽  
Propeller Blade ◽  
Unsteady Forces ◽  
Unsteady Force ◽  
Beam Surface ◽  
Propeller Blades ◽  
Unsteady Lift

A new method to measure the total unsteady lift force across a propeller blade is presented in this paper. Unsteady forces across propeller blades are generated from the interaction of the blade boundary with a rotating pressure field associated with the propeller. The oscillating nature of the unsteady forces, particularly at higher harmonics, suggests that the unsteady lift fluctuations nearly cancel out over the blade span, and that it is possible to find the total unsteady force across the propeller from parameters at the root and tip. These parameters were determined from an approximation provided by the Method of the Stationary Phase. A newly designed apparatus for the measurement of total unsteady force across a propeller blade based on this theory is described in detail. For future experimental validation of the newly designed sensors, a propeller blade is modeled as a uniform beam, and a known unsteady force is generated across the beam surface.

On the Prediction of Unsteady Forces on Gas-Turbine Blades: Part 1 — Typical Results and Potential-Flow-Interaction Effects

1988 ◽  
Author(s):  
Theodosios P. Korakianitis
Keyword(s):  
Computer Program ◽  
Potential Flow ◽  
Turbine Blades ◽  
Unsteady Forces ◽  
Flow Angle ◽  
Flow Calculation ◽  
Gas Turbine Blades ◽  
Flow Interaction ◽  
Unsteady Force ◽  
Outlet Flow

This paper is a contribution to the study of the generation of unsteady forces on turbine blades due to potential-flow interaction and viscous-wake interaction from upstream blade rows. A computer program is used to compute the unsteady forces on a rotor. The accuracy of the computer program is tested by comparing the results of a steady-flow calculation case and of an unsteady-flow calculation case with theory and experiment respectively. Results are shown for typical stator-to-rotor-pitch ratios and stator outlet-flow angles. These results show that the first spatial harmonic of the unsteady force may decrease for higher stator-to-rotor-pitch ratios. This trend is explained by considering the mechanisms by which the unsteady forces are generated. In this paper the mechanism by which the potential-flow interaction affects the flow field to generate these unsteady forces is shown to vary with the stator-to-rotor-pitch ratio and with the outlet flow angle of the stator.

scholarly journals On the Prediction of Unsteady Forces on Gas-Turbine Blades: Part 2 — Viscous-Wake-Interaction and Axial-Gap Effects

1988 ◽  
Author(s):  
Theodosios P. Korakianitis
Keyword(s):  
Potential Flow ◽  
Turbine Blades ◽  
Unsteady Forces ◽  
Flow Angle ◽  
Gas Turbine Blades ◽  
Flow Interaction ◽  
Wake Interaction ◽  
Unsteady Force ◽  
Outlet Flow ◽  
Pitch Ratio

This paper is a contribution to the study of the generation of unsteady forces on turbine blades due to viscous wake interaction and potential-flow interaction from upstream blade rows. A computer program is used to compute the unsteady forces on a rotor. Typical results for isolated viscous-wake interaction (no potential-flow interaction) are shown. These results indicate that the first spatial harmonic of the unsteady force may decrease for higher stator-to-rotor-pitch ratios. This trend is explained by considering the mechanisms by which the unsteady forces are generated. The mechanism by which the viscous wakes affect the flow field to generate these unsteady forces is shown to vary with the stator-to-rotor-pitch ratio and with the outlet flow angle of the stator. It is also shown that by varying the axial gap between rotor and stator one can attempt to minimize the magnitude of the unsteady part of the forces generated by the combined effects of viscous-wake interaction and potential-flow interaction.

Unsteady Load of Partial Admission Control Stage Rotor of a Large Power Steam Turbine

2004 ◽  
Author(s):  
Piotr Lampart ◽  
Mariusz Szymaniak ◽  
Romuald Rza˛dkowski
Keyword(s):  
Steam Turbine ◽  
Rotor Blades ◽  
Pressure Pulsations ◽  
Unsteady Forces ◽  
Large Power ◽  
Control Stage ◽  
Partial Admission ◽  
Geometrical Imperfections ◽  
Sst Turbulence Model ◽  
2D Model

Partial admission flow in the control stage of a 200MW steam turbine is investigated with the help of a RANS solver with k-ω SST turbulence model in the code Fluent. A 2D model of flow at the mid-span section of the full annulus is assumed. The results exhibit interesting details of the process of expansion in the control stage. Unsteady forces acting on the single rotor blades of the control stage are calculated, and are subject to Fourier analysis. Single blade forces are summed up to obtain the unsteady load at the rotor (forces acting at the rotor disc are neglected due to the assumed 2D model). The calculations take into account pressure pulsations at the entry to the nozzle boxes and rotor blade mistuning / geometrical imperfections.

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.

On the Prediction of Unsteady Forces on Gas Turbine Blades: Part 1—Description of the Approach

1992 ◽  
Vol 114 (1) ◽  
pp. 114-122 ◽  
Author(s):  
T. Korakianitis
Keyword(s):  
Flow Field ◽  
Potential Flow ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Flow Disturbance ◽  
Unsteady Forces ◽  
Gas Turbine Blades ◽  
Wake Interaction ◽  
Flow Case

This article investigates the generation of unsteady forces on turbine blades due to potential-flow interaction and viscous-wake interaction from upstream blade rows. A computer program is used to calculate the unsteady forces on the rotor blades. Results are obtained by modeling the effects of the stator viscous wake and the stator potential-flow field on the rotor flow field. The results for one steady and one unsteady flow case are compared with known analytical and experimental data. The amplitudes for the two types of interaction are based on an analysis of available viscous wake data, on measurements of the potential-flow disturbance downstream of typical turbine stators, and on a parametric study of the effects of the amplitudes on the results of the unsteady forces generated on a typical turbine rotor cascade.

Sign in / Sign up

Export Citation Format

Share Document