Influence of Tip Shroud Modeling on the Flutter Stability of a Low Pressure Turbine Rotor

2019 ◽  
Author(s):  
Lorenzo Pinelli ◽  
Federico Vanti ◽  
Andrea Arnone ◽  
Benjamin Beßling ◽  
Damian M. Vogt
Keyword(s):  
Modal Analysis ◽  
Open Source ◽  
Linear Method ◽  
Turbine Blades ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Contact Interface ◽  
Aerodynamic Damping ◽  
Low Pressure Turbine ◽  
Tip Shroud

Abstract Since the modern design trend of low pressure turbine blades for aeronautical propulsion leads to lighter and more loaded blades, thus prone to flutter induced vibrations; flutter assessment is now a standard verification within the design loop of these components. Flutter stability assessment requires FEM and CFD tools able to predict the pressure response of fluid flow due to blade oscillation in order to compute the aerodynamic damping. Such tools are mature and validated, yet some geometrical aspects of the blade-row as contact interfaces at the blade tip shroud have to be carefully simulated to obtain accurate flutter results. The aim of this paper is to demonstrate the capability of the Open Source FEM tool (CalculiX) to deal with complex interlocked rotor geometries when performing modal analysis and to show the influence of different contact interface modeling on flutter stability. The solid mesh of a single-pitch row sector has been generated by using the Open Source suite Salome and the modal analysis has been carried out with CalculiX with cyclic symmetry conditions. The following uncoupled flutter simulations have been performed with the CFD TRAF code, an in-house solver developed at the University of Florence, which implements a non-linear method for flutter evaluation. An in-depth comparison among the FEM models with different boundary conditions in terms of mode shape frequency and aerodynamic damping curves are reported. These results show the effect of different contact interface models, especially on the first bending mode family, and confirm the overall row stability detected during a dedicated experimental flutter campaign.

Analysis of Low-Pressure Turbine Flutter for Different Shroud Interfaces

2007 ◽  
Author(s):  
X. Wu ◽  
M. Vahdati ◽  
C. Schipani ◽  
M. Imregun
Keyword(s):  
Contact Surface ◽  
Low Pressure ◽  
Tangential Direction ◽  
Turbine Rotor ◽  
Mode Shapes ◽  
Element Analysis ◽  
Nodal Diameter ◽  
Severe Wear ◽  
Low Pressure Turbine ◽  
Tip Shroud

This paper reports the findings of a flutter investigation on a low-pressure turbine rotor having an integrally machined tip shroud with different type of constraints. Two types of tip shroud constraints, namely fully constrained and tangentially free, were used, representing two extreme conditions: (a) a typical integrated shroud design with a tight interlocking and no wear on contact surface; and (b) an extremely smooth contact surface design or the most severe wear of a fully constrained interface, or changes in the manufacturing process that result in almost no friction across the shroud surface. The tangentially free constraint is unusual in that it seeks to explore how sensitively the contact constraint could cause blades to response. The mode shapes and corresponding frequency characteristic are presented for both shroud constraints using a standard finite element analysis. The flutter analysis was firstly undertaken by considering all vibration modes of interest in a single calculation using a whole-annulus model of the rotor. It was found that the removal of the tip constraints in the tangential direction was responsible for introducing the unstable first flap family under condition of zero mechanical damping. Of considerable interest was the fact that instability in the first flap mode occurred in forward-travelling nodal diameter modes, which is considered as somewhat different from classical low-pressure turbine flutter where instability exists in backward-travelling nodal diameter modes. The flutter mechanism was verified by undertaking a detailed investigation on the forward-travelling nodal diameter modes of the first flap family using a single-passage analysis. It was concluded that tip shroud constraints are highly sensitive for turbine blade interlock designs and unusual response could be excited under extremely severe wear condition.

Cracks on the Roots of Turbine Blades of the Low-Pressure Turbine in a Steam Power Plant

2015 ◽  
Vol 52 (4) ◽  
pp. 214-225 ◽  
Author(s):  
E. Plesiutschnig ◽  
R. Vallant ◽  
G. Stöfan ◽  
C. Sommitsch ◽  
M. Mayr ◽  
...  
Keyword(s):  
Power Plant ◽  
Turbine Blades ◽  
Low Pressure ◽  
Steam Power ◽  
Steam Power Plant ◽  
Low Pressure Turbine

Influence of Hot Streak Temperature Ratio on Low Pressure Stage of a Vaneless Counter-Rotating Turbine

2007 ◽  
Author(s):  
Qingjun Zhao ◽  
Fei Tang ◽  
Huishe Wang ◽  
Jianyi Du ◽  
Xiaolu Zhao ◽  
...  
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Temperature Ratio ◽  
High Pressure Turbine ◽  
Pressure Stage ◽  
Low Pressure Turbine ◽  
Hot Streak

In order to explore the influence of hot streak temperature ratio on low pressure stage of a Vaneless Counter-Rotating Turbine, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed. The predicted results show that hot streaks are not mixed out by the time they reach the exit of the high pressure turbine rotor. The separation of colder and hotter fluids is observed at the inlet of the low pressure turbine rotor. After making interactions with the inner-extending shock wave and outer-extending shock wave in the high pressure turbine rotor, the hotter fluid migrates towards the pressure surface of the low pressure turbine rotor, and the most of colder fluid migrates to the suction surface of the low pressure turbine rotor. The migrating characteristics of the hot streaks are predominated by the secondary flow in the low pressure turbine rotor. The effect of buoyancy on the hotter fluid is very weak in the low pressure turbine rotor. The results also indicate that the secondary flow intensifies in the low pressure turbine rotor when the hot streak temperature ratio is increased. The effects of the hot streak temperature ratio on the relative Mach number and the relative flow angle at the inlet of the low pressure turbine rotor are very remarkable. The isentropic efficiency of the Vaneless Counter-Rotating Turbine decreases as the hot streak temperature ratio is increased.

The Application of Ceramic Matrix Composite to Low Pressure Turbine Blade

2016 ◽  
Author(s):  
Fumiaki Watanabe ◽  
Takeshi Nakamura ◽  
Ken-ichi Shinohara
Keyword(s):  
Centrifugal Force ◽  
Failure Modes ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix ◽  
Low Pressure ◽  
Screening Tests ◽  
Low Pressure Turbine ◽  
Load Tests ◽  
Tip Shroud ◽  
Block Approach

The structural reliability of composite parts for aircraft is established through the “building block” approach, which is a series of tests that are conducted using specimens of various levels of complexity. In this approach, the failure modes and criteria are validated step by step with tests and analysis at coupon, element, sub-component, and component levels. IHI is developing ceramic matrix composite (CMC) components for aircraft engines to realize performance improvement and weight reduction. We conducted the concept design of CMC low pressure turbine (LPT) blade with the building block approach. In this paper, we present the processes and results of the design, which was supported by a series of tests. Typical low pressure turbine blade has dovetail, airfoil and tip shroud. Each element has different function and characteristic shape. In order to select the configuration of CMC LPT blade, we conducted screening tests for each element. The function of dovetail is to sustain the connection with blade and disk against centrifugal force. The failure modes and strength of dovetail elements were examined by static load tests and cyclic load tests. The configuration of airfoil was selected by modal tests. The function of tip shroud is forming gas passage and reducing the leakage flow, therefore this portion needs to sustain the shape against the centrifugal force and the rubbing force. The feasibility of tip shroud was verified by spin tests and rubbing tests. The initial CMC LPT blades were designed as combination of the selected elements by these screening tests. Prototype parts were made and tested to check the manufacturability and the structural feasibility. The static strength to the centrifugal force was examined by spin test. The durability to vibration was examined by HCF test.

Premature Fatigue Failures in the Hot Zone of Low Pressure Turbine Rotor (LPTR) Blades of Aero-Engine

2017 ◽  
pp. 65-76
Author(s):  
M. Madan ◽  
R. Bharathanatha Reddy ◽  
K. Raghavendra ◽  
M. Sujata ◽  
S. K. Bhaumik
Keyword(s):  
Low Pressure ◽  
Turbine Rotor ◽  
Low Pressure Turbine ◽  
Aero Engine ◽  
Fatigue Failures ◽  
Hot Zone

scholarly journals Aerodynamics and Modal Analysis for the Combined Vane type Vertical Axis Wind Turbine

2018 ◽  
Vol 7 (4.38) ◽  
pp. 1395 ◽  
Author(s):  
Kadhim H. Suffer ◽  
Yassr Y. Kahtan ◽  
Zuradzman M. Razlan
Keyword(s):  
Wind Turbine ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Mode Shapes ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Starting Torque

The present global energy economy suggests the use of renewable sources such as solar, wind, and biomass to produce the required power. The vertical axis wind turbine is one of wind power applications. Usually, when the vertical axis wind turbine blades are designed from the airfoil, the starting torque problem begins. The main objective of this research is to numerically simulate the combination of movable vanes of a flat plate with the airfoil in a single blade configuration to solve the starting torque problem. CFD analysis in ANSYS-FLUENT and structural analysis in ANSYS of combined blade vertical axis wind turbine rotor has been undertaken. The first simulation is carried out to investigations the aerodynamic characteristic of the turbine by using the finite volume method. While the second simulation is carried out with finite element method for the modal analysis to find the natural frequencies and the mode shape in order to avoid extreme vibration and turbine failure, the natural frequencies, and their corresponding mode shapes are studied and the results were presented with damping and without damping for four selected cases. The predicted results show that the static pressure drop across the blade increase in the active blade side because of the vanes are fully closed and decrease in the negative side because of the all the vanes are fully open. The combined blade helps to increase turbine rotation and so, thus, the power of the turbine increases. While the modal results show that until the 5th natural frequency the effect of damping can be neglected. The predicted results show agreement with those reported in the literature for VAWT with different blade designs.   

Analysis on High Rates of Scaling and Salt Accumulation of 600MW Supercritical once-through Boiler

2012 ◽  
Vol 166-169 ◽  
pp. 620-626
Author(s):  
Xiao Ni Zhang ◽  
Xian Min Li ◽  
Chang Ming Li
Keyword(s):  
Turbine Blades ◽  
Low Pressure ◽  
Fossil Plants ◽  
Salt Accumulation ◽  
Accelerated Corrosion ◽  
Low Pressure Turbine ◽  
Salt Deposition ◽  
Boiler Units ◽  
Salt Deposits ◽  
Flow Accelerated Corrosion

The chemistry check-ups were reviewed in the first maintenance of 600 MW supercritical once-through boiler units in Henan. Several problems were found: (1) high rates of scaling on the waterwall and economizer; (2) high rates of salt deposition on the turbine blades; (3) the formation of salt deposits on blades were complicated; (4) corrosion of low pressure turbine blades in period of maintenance was a universal phenomenon; (5) FAC (flow-accelerated corrosion) were most frequent in HP heaters and HP drain lines in most fossil plants. The reasons have been analyzed and the suggestions have been provided.

Investigation of the Impact of Unsteady Turbulence Effects on the Aeroelastic Analysis of a Low-Pressure Turbine Rotor Blade

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Jan Philipp Heners ◽  
Damian M. Vogt ◽  
Christian Frey ◽  
Graham Ashcroft
Keyword(s):  
Rotor Blade ◽  
Numerical Study ◽  
Turbulence Models ◽  
Gibbs Phenomenon ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Filter Method ◽  
Turbine Rotor Blade ◽  
Low Pressure Turbine ◽  
The Impact

Abstract The impact of the unsteadiness in the considered turbulence quantities on the numerical prediction of the aeroelastic behavior of a low-pressure turbine (LPT) rotor blade is evaluated by means of a numerical study. In this context, one of the main objectives of this work is to compare different nonlinear harmonic balance (HB) approaches—one neglecting and one considering the unsteadiness in the employed turbulence models—with a conventional nonlinear solver of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in the time domain. In order to avoid unphysical oscillations in the turbulence quantities caused by the Gibbs phenomenon in the chosen HB approach, a filter method based on the Lanczos filter is developed. The developed filter method is applied in the course of the HB simulations considering the unsteadiness in the underlying turbulence model. Furthermore, the impact of its application on the solution of the flow field and on the unsteady surface pressure of the rotor blade, in particular, is discussed in the context of this work.

scholarly journals Investigation of parts assembly error, taking into account the deviation of the shape of their surfaces

2018 ◽  
Vol 224 ◽  
pp. 01098 ◽  
Author(s):  
Mikhail Bolotov ◽  
Iliya Grachev ◽  
Evgeny Kudashov
Keyword(s):  
Computer Model ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Low Pressure Turbine ◽  
Geometrical Errors ◽  
Study Results ◽  
Assembly Unit ◽  
Assembly Error

In this article, we study the errors in the assembly of parts, taking into account the deviation of the shape of their surfaces. The developed computer model of the assembly of the engine low-pressure turbine rotor is designed to predict the values of the assembly parameters, such as radial and face run-out. The forecasting of the above assembly parameters is carried out based on the data of actual dimensions and shape of the surfaces of parts assembled as an assembly unit. The analysis of study results made it possible to obtain a conclusion about the qualitative influence of geometrical errors of the assembled parts on the error of the assembly parameters.

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