Behavior of a Variable Geometry Turbine Wheel to High Cycle Fatigue

2020 ◽  
Author(s):  
Calogero Avola ◽  
Alberto Racca ◽  
Angelo Montanino ◽  
Carnell E. Williams ◽  
Alfonso Renella ◽  
...  
Keyword(s):  
High Cycle Fatigue ◽  
Combustion Engine ◽  
Turbine Blades ◽  
Variable Geometry ◽  
Cycle Fatigue ◽  
Turbine Stage ◽  
Turbine Wheel ◽  
Variable Geometry Turbine ◽  
Turbine Design ◽  
Mechanical Optimization

Abstract Maximization of the turbocharger efficiency is fundamental to the reduction of the internal combustion engine back-pressure. Specifically, in turbochargers with a variable geometry turbine (VGT), energy losses can be induced by the aerodynamic profile of both the nozzle vanes and the turbine blades. Although appropriate considerations on material limits and structural performance of the turbine wheel are monitored in the design and aero-mechanical optimization phases, in these stages, fatigue phenomena might be ignored. Fatigue occurrence in VGT wheels can be categorized into low and high cycle behaviors. The former would be induced by the change in turbine rotational speed in time, while the latter would be caused by the interaction between the aerodynamic excitation and blades resonating modes. In this paper, an optimized turbine stage, including unique nozzle vanes design and turbine blades profile, has been assessed for high cycle fatigue (HCF) behavior. To estimate the robustness of the turbine wheel under several powertrain operations, a procedure to evaluate HCF behavior has been developed. Specifically, the HCF procedure tries to identify the possible resonances between the turbine blades frequency of vibrations and the excitation order induced by the number of variable vanes. Moreover, the method evaluates the turbine design robustness by checking the stress levels in the component against the limits imposed by the Goodman law of the material selected for the turbine wheel. In conclusion, both the VGT design and the HCF approach are experimentally assessed.

A Numerical Study and Design of Turbine Blade under High Temperature and Rotational Speed Using FEM

2006 ◽  
Vol 324-325 ◽  
pp. 1063-1066
Author(s):  
Jang Hyun Lee ◽  
Kyung Ho Lee ◽  
Kyung Su Kim
Keyword(s):  
High Temperature ◽  
High Cycle Fatigue ◽  
Numerical Study ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Stress And Strain ◽  
Cycle Fatigue ◽  
Fatigue Load ◽  
Turbine Wheel ◽  
Revolution Speed

The turbine wheels of a turbocharger are operated at high revolution speed in high temperature inlet gas. Alloy 713LC blades of the turbine wheel broke in an hour the during a model test. Two failures and several cracks were found in the turbine blades. Failures in blades are suspected to occur as a result of thermal mechanical stresses or fatigue load and other cause such as creep-rupture and resonant vibration. The present study investigates the possible causes of the failure of these blades. FEM (Finite Element Method) was used to calculate the thermal centrifugal stresses and natural frequency to find the cause of failures. LCF (Low Cycle Fatigue) life of blades was roughly estimated by using the stress and strain level calculated by FEM. The investigation indicates that the failures were associated with resonant forces and HCF (High Cycle Fatigue).

Numerical Investigation of a Novel Approach for Mitigation of Forced Response of a Variable Geometry Turbine During Exhaust Braking Mode

2016 ◽  
Author(s):  
Ben Zhao ◽  
Leon Hu ◽  
Harold Sun ◽  
Ce Yang ◽  
Xin Shi ◽  
...  
Keyword(s):  
Shock Wave ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Forced Response ◽  
Aerodynamic Load ◽  
Variable Geometry ◽  
Original Design ◽  
Turbine Wheel ◽  
Nozzle Vane ◽  
Variable Geometry Turbine

One of critical concerns in a variable geometry turbine (VGT) design program is shock wave generated from nozzle exit at small open conditions with high inlet pressure condition, which may potentially lead to forced response of turbine wheel, even high-cycle fatigue issues and damage of inducer or exducer. Though modern turbine design programs have been well developed, it is difficult to eliminate the shock wave and all the resonant crossings that may occur within the wide operating range of a VGT turbine for automotive applications. This paper presents an option to mitigate intensity of the shock wave induced excitation using grooves on nozzle vane surface before the shock wave. Two kinds of turbines in which nozzle vanes with and without grooves were numerically simulated to obtain a three-dimensional flow field inside the turbine. The predicted performances from steady simulations were compared with test data to validate computational mesh and the unsteady simulation results were analyzed in detail to predict the responses of both shock wave and aerodynamic load acting on turbine blade surface. Compared with the original design, an introduction of grooves on nozzle vane surface mitigates the shock wave while also obviously reduces the amplitudes of alternating aerodynamic load on the turbine blades.

Aeroelastic Analysis of NREL Wind Turbine

2017 ◽  
Author(s):  
Yaozhi Lu ◽  
Fanzhou Zhao ◽  
Loic Salles ◽  
Mehdi Vahdati
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Gas Turbines ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Measured Data ◽  
Forced Response ◽  
Cycle Fatigue ◽  
Aeroelastic Analysis

The current development of wind turbines is moving toward larger and more flexible units, which can make them prone to fatigue damage induced by aeroelastic vibrations. The estimation of the total life of the composite components in a wind turbine requires the knowledge of both low and high cycle fatigue (LCF and HCF) data. The first aim of this study is to produce a validated numerical model, which can be used for aeroelastic analysis of wind turbines and is capable of estimating the LCF and HCF loads on the blade. The second aim of this work is to use the validated numerical model to assess the effects of extreme environmental conditions (such as high wind speeds) and rotor over-speed on low and high cycle fatigue. Numerical modelling of this project is carried out using the Computational Fluid Dynamics (CFD) & aeroelasticity code AU3D, which is written at Imperial College and developed over many years with the support from Rolls-Royce. This code has been validated extensively for unsteady aerodynamic and aeroelastic analysis of high-speed flows in gas turbines, yet, has not been used for low-speed flows around wind turbine blades. Therefore, in the first place the capability of this code for predicting steady and unsteady flows over wind turbines is studied. The test case used for this purpose is the Phase VI wind turbine from the National Renewable Energy Laboratory (NREL), which has extensive steady, unsteady and mechanical measured data. From the aerodynamic viewpoint of this study, AU3D results correlated well with the measured data for both steady and unsteady flow variables, which indicated that the code is capable of calculating the correct flow at low speeds for wind turbines. The aeroelastic results showed that increase in crosswind and shaft speed would result in an increase of unsteady loading on the blade which could decrease the lifespan of a wind turbine due to HCF. Shaft overspeed leads to significant increase in steady loading which affects the LCF behaviour. Moreover, the introduction of crosswind could result in significant dynamic vibration due to forced response at resonance.

Plastic Effects on High Cycle Fatigue at the Edge of Contact of Turbine Blade Fixtures

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
C. H. Richter ◽  
U. Krupp ◽  
M. Zeißig ◽  
G. Telljohann
Keyword(s):  
Finite Element Analysis ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Notched Specimens ◽  
The Finite Element Analysis ◽  
Slip Region ◽  
Good Agreement

Slender turbine blades are susceptible to excitation. Resulting vibrations stress the blade's fixture to the rotor or stator. In this paper, high cycle fatigue at the edge of contact (EOC) between blade and rotor/stator of such fixtures is investigated both experimentally and numerically. Plasticity in the contact zone and its effects on, e.g., contact tractions, fatigue determinative quantities, and fatigue itself are shown to be of considerable relevance. The accuracy of the finite element analysis (FEA) is demonstrated by comparing the predicted utilizations and slip region widths with data gained from tests. For the evaluation of EOC fatigue, tests on simple notched specimens provide the limit data. Predictions on the utilization are made for the EOC of a dovetail setup. Tests with this setup provide the experimental fatigue limit to be compared to. The comparisons carried out show a good agreement between the experimental results and the plasticity-based calculations of the demonstrated approach.

Nanotechnology Coatings for Erosion Protection of Turbine Components

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
V. P.“Swami” Swaminathan ◽  
Ronghua Wei ◽  
David W. Gandy
Keyword(s):  
Solid Particle ◽  
Gas Turbines ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Silicon Carbonitride ◽  
Screening Tests ◽  
Solid Particle Erosion ◽  
Cycle Fatigue ◽  
Particle Erosion ◽  
Research Institute

Solid particle erosion (SPE) and liquid droplet erosion (LDE) cause severe damage to turbine components and lead to premature failures, business loss, and repair costs to power plant owners and operators. Under a program funded by the Electric Power Research Institute, TurboMet International and Southwest Research Institute (SRI) have developed hard erosion resistant nanocoatings and have conducted evaluation tests. These coatings are targeted for application in steam and gas turbines to mitigate the adverse effects of SPE and LDE on rotating blades and stationary vanes. Based on a thorough study of the available information, the most promising coatings, such as nanostructured titanium silicon carbonitride (TiSiCN), titanium nitride (TiN), and multilayered nanocoatings, were selected. State-of-the-art nanotechnology coating facilities at SwRI were used to develop the coatings. The plasma enhanced magnetron sputtering method was used to apply these coatings on various substrates. Ti–6Al–4V, 12Cr, 17-4PH, and custom 450 stainless steel substrates were selected based on the current alloys used in gas turbine compressors and steam turbine blades and vanes. Coatings with up to 30μm thickness have been deposited on small test coupons. Initial screening tests on coated coupons by solid particle erosion testing indicate that these coatings have excellent erosion resistance by a factor of 20 over the bare substrate. Properties of the coating, such as modulus, hardness, microstructural conditions including the interface, and bond strength, were determined. Tensile and high-cycle fatigue tests on coated and uncoated specimens indicate that the presence of the coatings has no negative effects but has a positive influence on the high-cycle fatigue strength at zero and high mean stresses.

HCF Optimization of a High Speed Variable Geometry Turbine

2021 ◽  
Author(s):  
Alister Simpson ◽  
Sung in Kim ◽  
Jongyoon Park ◽  
Seong Kwon ◽  
Sejong Yoo
Keyword(s):  
High Speed ◽  
Forced Response ◽  
Variable Geometry ◽  
Blade Vibration ◽  
Operating Cycle ◽  
Turbine Wheel ◽  
Aerodynamic Loads ◽  
Radial Turbine ◽  
Wide Range ◽  
Variable Geometry Turbine

Abstract This paper describes the structural optimization of a high speed, 35mm tip diameter radial turbine wheel in a Variable Geometry Turbine (VGT) system, subjected to the wide range of aerodynamic loads experienced during the full operating cycle. VGTs exhibit a wide range of unsteady flow features, which vary as the nozzle vanes rotate through different positions during operation, as do the magnitudes and frequencies of the resulting pressure fluctuations experienced by the downstream turbine blades. The turbine wheel typically passes through a number of blade natural frequencies over their operating cycle, and there are a number of potential conditions where these unsteady aerodynamic loads can lead to resonant blade vibration. The focus of this work is on the development of a pragmatic design approach to improve the structural characteristics of a radial turbine blade with respect to High Cycle Fatigue (HCF), informed by detailed time-accurate Computational Fluid Dynamics (CFD) prediction of the unsteady pressure loads, coupled with FE vibration analysis to quantify the resulting blade vibration magnitudes. Unsteady CFD simulations are performed to determine the time-accurate pressure loads on the blades, and the results are used as input to forced response analysis to determine the peak alternating stress amplitudes. The detailed analysis results are then used to guide a subsequent parametric study in order to investigate the influence of key geometric parameters on the structural performance of the blade, with the optimum design identified through the use of a Goodman Diagram. The results quantify the influence of both blade thickness distribution and hub fillet details on the vibration characteristics of radial turbines.

Influence of Geometric Design Parameters Onto Vibratory Response and HCF Safety for Turbine Blades With Friction Damper

2018 ◽  
Author(s):  
Matthias Hüls ◽  
Lars Panning-von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Aspect Ratio ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Design Parameters ◽  
System Response ◽  
Blade Design ◽  
Cycle Fatigue ◽  
Resonance Amplitude ◽  
Damped System ◽  
Vibratory Response

Among the major concerns for high aspect-ratio turbine blades are forced and self-excited (flutter) vibrations which can cause failure by high-cycle fatigue. The introduction of friction damping in turbine blades, such as by coupling of adjacent blades via under platform dampers, can lead to a significant reduction of resonance amplitudes at critical operational conditions. In this paper, the influence of basic geometric blade design parameters onto the damped system response will be investigated to link design parameters with functional parameters like damper normal load, frequently used in nonlinear dynamic analysis. The shape of a simplified large aspect-ratio turbine blade is parameterized along with the under platform damper configuration. The airfoil is explicitly included into the parameterization in order to account for changes in blade mode shapes. For evaluation of the damped system response under a typical excitation, a reduced order model for non-linear friction damping is included into an automated 3D FEA tool-chain. Based on a design of experiments approach, the design space will be sampled and a surrogate model is trained on the received dataset. Subsequently, the mean and interaction effects of the true geometric blade design parameters onto the resonance amplitude and safety against high-cycle fatigue will be outlined for a critical first bending type vibrational motion. Design parameters were mainly found to influence the resonance amplitude by their effect onto the tip-to-platform deflection ratio. The HCF safety was affected by those design parameters with large sensitivity onto static and resonant vibratory stress levels. Applying an evolutionary optimization algorithm, it is shown that the optimum blade design with respect to minimum vibratory response at a particular node can differ significantly from a blade designed toward maximum HCF safety.

scholarly journals Dynamic Response in Transient Operation of a Variable Geometry Turbine Stage: Influence of the Aerodynamic Performance

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Nicolas Binder ◽  
Jaime Garcia Benitez ◽  
Xavier Carbonneau
Keyword(s):  
Response Time ◽  
Transient Response ◽  
Aerodynamic Performance ◽  
Variable Geometry ◽  
Transient Phase ◽  
Theoretical Expectation ◽  
Turbine Stage ◽  
Experimental Campaign ◽  
Variable Geometry Turbine ◽  
Operating Points

The transient response of a radial turbine stage with a variable geometry system is evaluated. Mainly, the consequences of the variations of the aerodynamic performance of the stage on the response time are checked. A simple quasi-steady model is derived in order to formalize the expected dependences. Then an experimental campaign is conducted: a brutal step in the feeding conditions of the stage is imposed, and the response time in terms of rotational speed is measured. This has been reproduced on different declinations of the same stage, through the variation of the stator geometry, and correlated to the steady-state performance of the initial and final operating points of the transient phase. The matching between theoretical expectation and results is surprisingly good for some configurations, less for others. The most important factor identified is the mass-flow level during the transient phase. It increases the reactivity, even far above the theoretical expectation for some configurations. For those cases, it is demonstrated that the quasi-steady approach may not be sufficient to explain how the transient response is set.

Investigations Into the Performance of a Turbogenerated Biogas Engine During Speed Transients

2011 ◽  
Author(s):  
Ian Thompson ◽  
Stephen Spence ◽  
Charles McCartan ◽  
David Thornhill ◽  
Jonathan Talbot-Weiss
Keyword(s):  
Engine Speed ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
System Efficiency ◽  
Variable Geometry Turbine ◽  
Exhaust Stream ◽  
Full Power ◽  
System Operating

Turbogenerating is a form of turbocompounding whereby a Turbogenerator is placed in the exhaust stream of an internal combustion engine. The Turbogenerator converts a portion of the expelled energy in the exhaust gas into electricity which can then be used to supplement the crankshaft power. Previous investigations have shown how the addition of a Turbogenerator can increase the system efficiency by up to 9%. However, these investigations pertain to the engine system operating at one fixed engine speed. The purpose of this paper is to investigate how the system and in particular the Turbogenerator operate during engine speed transients. On turbocharged engines, turbocharger lag is an issue. With the addition of a Turbogenerator, these issues can be somewhat alleviated. This is done by altering the speed at which the Turbogenerator operates during the engine’s speed transient. During the transients, the Turbogenerator can be thought to act in a similar manner to a variable geometry turbine where its speed can cause a change in the turbocharger turbine’s pressure ratio. This paper shows that by adding a Turbogenerator to a turbocharged engine the transient performance can be enhanced. This enhancement is shown by comparing the turbogenerated engine to a similar turbocharged engine. When comparing the two engines, it can be seen that the addition of a Turbogenerator can reduce the time taken to reach full power by up to 7% whilst at the same time, improve overall efficiency by 7.1% during the engine speed transient.

A Physics-Based Control-Oriented Model for the Turbine Power of a Variable-Geometry Turbo-Charger

2016 ◽  
Author(s):  
Kang Song ◽  
Devesh Upadhyay ◽  
Tao Zeng ◽  
Harold Sun
Keyword(s):  
Dimensionless Parameter ◽  
Transmission Loss ◽  
Empirical Relationship ◽  
Variable Geometry ◽  
Turbine Stage ◽  
Turbo Charger ◽  
Variable Geometry Turbine ◽  
Polytropic Process ◽  
Nozzle Orientation ◽  
Bearing Friction

In this paper, we discuss the development of a control-oriented model for the power developed by a Variable Geometry Turbine (VGT). The turbine exit flow velocity, Cex, is obtained based on a polytropic process assumption for the full turbine stage. The rotor inlet velocity, Cin, is estimated, through an empirical relationship between Cex and Cin as a function of a dimensionless parameter ψ. The turbine power is developed based on Euler’s equations of Turbomachinery under the assumptions of zero exit swirl and alignment between the nozzle orientation and the Cin velocity vector. A power loss sub-model is also designed to account for the transmission loss associated with the power transfer between the turbine and compressor. The loss model is an empirical model and accounts for bearing friction and windage losses. Model validation results, for both steady state and transient operation, are shown.

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