bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mistuning Analysis of a Detuned Bladed-Disk With Geometrical Nonlinearities
Authors: Picou Anthony , Capiez-Lernout Evangéline , Soize Christian , Mbaye Moustapha 
Published: November 2019

Abstract
This work concerns the nonlinear numerical analysis of mistuned blades for a rotating detuned bladed-disk structure with geometrical nonlinearities. The detuning phenomenon is taken into account through a deterministic approach by modifying material properties of some blades. A nonlinear reduced-order model is obtained by setting up a basis using a double projection method. The mistuning uncertainties are implemented through a nonparametric probabilistic approach for which the level of uncertainties is controlled by a hyperparameter. A numerical application is carried out on a bladed-disk structure made up of 24 blades whose finite element model has about 800,000 dofs exhibiting complex dynamic behaviors.
Unsteady Flow Interactions Between a High- and Low-Pressure Turbine: Part 2 — Rotor-Synchronic Averaging and Proper Orthogonal Decomposition of the Unsteady Flow Fields
Authors: Dellacasagrande M. , Sterzinger P. Z. , Zerobin S. , Merli F. , Wiesinger L. , Peters A. , Maini G. , Heitmeir F. , Göttlich E. 
Published: November 2019

Abstract
This paper, the second of two parts, presents an experimental investigation of the unsteady flow field evolving in a two-stage two-spool test turbine facility. The experimental setup, which was designed to reproduce the operating condition of modern commercial aero-engines, consists of a high-pressure turbine (HPT) stage followed by a turbine center frame (TCF) with non-turning struts, and a co-rotating low-pressure turbine (LPT) stage.
Measurements carried out with a fast-response aerodynamic pressure probe (FRAPP) were post-processed to describe the unsteady evolution of the flow downstream of the HPT rotor, through the TCF duct, and at the exit of the LPT stage. The time-resolved results presented in the first part of this paper show that deterministic fluctuations due to both rotors characterize the flow field downstream of the LPT. In order to characterize the deterministic unsteadiness induced by all the components constituting the turbine facility (HPT, TCF and LPT) and their interactions, measurements were carried out in three different planes located downstream of the HPT, at the exit of the TCF and downstream of the LPT stage. The unsteady results obtained in the plane located at the exit of the LPT are discussed in more details in this second part of this paper, providing information about the interactions between the two rotors.
A proper phase-average procedure, known as rotor synchronic averaging (RSA), which takes into account the rotorrotor interaction, was adopted to capture the unsteadiness due to both rotors. Proper Orthogonal Decomposition (POD) was also applied to provide a characterization of the major contributors in terms of energy to the deterministic unsteadiness occurring in the test turbine facility. At the exit of the LPT rotor, the perturbations induced by the HPT stage and the interactions between the two rotors were found to dominate over the unsteadiness due to the LPT only.
Effect of Squealer Rim Slot Structure on Turbine Blade Aerothermal Performance
Authors: Qian Mengcheng , Lu Shaopeng , Zhang Bo , Wang Weijie , Teng Jinfang 
Published: November 2019

Abstract
Recent studies have demonstrated that the turbine blade with a squealer tip has less aerodynamic loss than that with a flat tip. However, there exists an area of high heat transfer coefficient (HTC) in the frontal region of the cavity floor. The present study focuses on the effect of squealer rim slot structure on turbine blade aerothermal performance. An experiment of transient thermal measurement is carried out for a non-slot squealer tip to validate the numerical setup and the choice of turbulence model. ANSYS CFX is utilized to conduct the numerical simulations of cases with and without slot structure and they are both validated by the experimental data. Through the experimental and CFD results, it can be found that the case with a slot on the pressure side of the squealer rim has smaller area of high HTC region and the aerodynamic efficiency is raised. Moreover, the effect of different sizes of the slot is investigated numerically and it also has a great impact on the heat transfer and aerodynamics. The quantity of the flow passing through the slot can largely influence the flow field of the tip gap and the cavity. Thus, the heat transfer of these areas and the aerodynamic efficiency of the blade vary from the slot size.
CFD-Based Throughflow Analysis of Transonic Flows in Steam Turbines
Authors: Ricci Martina , Pacciani Roberto , Marconcini Michele , Macelloni Paolo , Cecchi Stefano , Bettini Claudio 
Published: November 2019

Abstract
A CFD-based throughflow solver is applied to the meridional analysis of low-pressure steam turbine modules. The throughflow code inherits its numerical scheme from a state-of-the-art CFD solver (TRAF code) and incorporates real gas capabilities, three-dimensional flow features and spanwise mixing models. Secondary flow effects are introduced via a concentrated vortex model. Tip gap and shroud leakage effects are modelled in terms of source vectors in the system of governing equations. The impact of part-span shrouds and snubbers are accounted for, on a local basis, through suitable body force fields.
The AUSM+-up upwind strategy has been adopted as a basis to construct a numerical flux scheme explicitly suited for throughflow applications. The original formulation has been adapted to handle real gas flows and to embed the treatment of body force fields in a fully consistent framework. The capability of the procedure is assessed by analysing the low-pressure modules of two large steam turbines designed and manufactured by Ansaldo Energia. These 3-stage modules include rotor tip shrouds and part-span snubbers, and feature supersonic flow and large blade twist. Throughflow predictions in terms of main performance figures and radial distributions of flow quantities are compared to experimental data and 3D steady viscous analyses. It will be shown how the proposed CFD-based throughflow model can be fruitfully used in the early stages of the design as it delivers predictions of comparable accuracy with 3D CFD analyses at a fraction of the computational time.
A Model-Based Solution for Gas Turbine Diagnostics: Simulations and Experimental Verification
Authors: Zaccaria Valentina , Stenfelt Mikael , Sjunnesson Anna , Hansson Andreas , Kyprianidis Konstantinos G. 
Published: November 2019

Abstract
Prompt detection of incipient faults and accurate monitoring of engine deterioration are key aspects for ensuring safe operations and planning a timely maintenance. Modern computing capabilities allow for more and more complex tools for engine monitoring and diagnostics. Nevertheless, an underlying physics-based approach is often preferable, because not only the “what” but also the “why” can be identified, providing an effective decision support tool to the service engineer.
In this work, a physics-based adaptive model is used to evaluate performance deltas and correct the data to reference conditions (gas turbine load and ambient conditions), while a data-driven correlation algorithm identifies the most likely matches within a fault signatures database. Possible faults are ordered from the highest correlation in the decision support system and the most likely fault can be selected based on the number of occurrences and the associated correlation. Gradual engine degradation can also be monitored by displaying performance deltas trends during time.
The diagnostics tool was tested on a validated performance model of a single-shaft industrial gas turbine and subsequently on experimental data. This paper presents the diagnostics system structure, the model adaptation scheme, and the results obtained from simulated and real fault data. Accurate fault isolation and severity identification were achieved in all cases, demonstrating the tool capability for decision support system.
Advanced Last Stage Blade for Nuclear Power Plant Upgrades
Authors: Siewert Christian , McCracken James R. , Thiemann Thomas 
Published: November 2019

Abstract
Utility steam turbines for electrical power generation are used at many places worldwide with different ambient conditions and different power plant configurations resulting in a variety of environmental and operational conditions. In some environments and operational conditions excitation mechanisms exist which may result in elevated Last Stage Blade vibrations. A particular example occurs in some steam turbine modernization projects, in which modern Last Stage Blade designs are applied in configurations with retained outer casing and diffusor designs from the original turbine design.
In this paper, operational experience with an advanced Last Stage Blade coupled by damping elements is presented. In addition, the background leading to the development of this Last Stage Blade is outlined in this paper. Vibration measurement data obtained from field measurements in certain modernized units with retained outer casings from original installation is summarized and compared to the corresponding data for a freestanding Last Stage Blade previously used in these units showing the vibrational behavior of the newly developed Last Stage Blade. Results from field inspections are also presented. The data and inspections show the Last Stage Blade with damping elements do not exhibit elevated vibrations previously indicated.
Influence of the Laminar Burning Velocity on the Transfer Functions of Premixed Methane and Propane Swirl Flames
Authors: Di Sabatino F. , Guiberti T. F. , Moeck J. P. , Roberts W. L. , Lacoste D. A. 
Published: November 2019

Abstract
The effects of the laminar burning velocity (SL), on the transfer functions of propane-air and methane-air swirl flames is experimentally investigated. Five equivalence ratios for each fuel are selected, to yield different values of SL. The flame transfer function (FTF), is obtained by comparing the velocity fluctuations of the incoming flow, measured with a hot wire, to the heat release rate oscillations, collecting OH* chemiluminescence with a photomultiplier tube. Phase-locked images of OH* chemiluminescence are also acquired to analyze the flame dynamics during the forcing cycle. The unforced velocity fields are measured by particle image velocimetry to assess the effects of SL on the flow fields. Changing the laminar burning velocity affects mainly the gain around 176 Hz and 336 Hz. This paper focuses on 336 Hz. The flame vortex roll-up is recognized as a key parameter controlling the gain of the FTF around 336 Hz. The analysis highlights that SL influences the gain response around 336 Hz in two competing ways: first, it enhances the flame vortex roll-up and second, it affects the stabilization distance of the flame, which influences the vortex generated by acoustic forcing.
Complex Design Method of Ceramic Blades and Metal Disk Connection
Authors: Sapronov Dmitry , Mezencev Michael , Karimbaev Telman , Reznik Sergey , Prosuntsov Pavel 
Published: November 2019

Abstract
This paper presents a complex approach to designing ceramic blades dovetail joints. Two ceramic materials were considered: diamond reinforced silicon carbide and hot pressed silicon nitride (only in contact testing). The model blades were made from diamond reinforced silicon carbide due to its availability and mature technology.
Part 1 describes the models of mechanical and thermal contact and contains experimental data on contact strength and thermal contact conductance.
Part 2 investigates the effect of stress concentration and scale factor on the fracture of ceramic test pieces.
Part 3 proposes a theoretical-experimental method to estimate friction coefficient in a dovetail joint. We also investigated the character of the ceramic blades fracture during the rotor spin-up.
Part 4 deals with automating the design process of the ceramic blades dovetail joints using experimental data.
Numerical Investigation of Combustion Instabilities in a Single Element Lean Direct Inject (LDI) Combustor Using Flamelet Based Approaches
Authors: Patwardhan Saurabh , Nakod Pravin , Orsino Stefano , Arguinzoni Carlo 
Published: November 2019

Abstract
In this paper, high-fidelity large eddy simulations (LES) along with flamelet based combustion models are assessed to predict combustion dynamics in low-emissions gas turbine combustor. A model configuration of a single element lean-direct-injection (LDI) combustor from Purdue University [1] is used for the validation of simulation results. Two combustion models based on the flamelet concept, i.e., steady diffusion flamelet (SDF) model and flamelet generated manifold (FGM) model are employed to predict combustion instabilities. Simulations are carried out for two equivalence ratios of φ = 0.6, and 0.4 and the results in the form of mode shapes, peak to peak pressure amplitude and power spectrum density (PSD) are compared with the experimental data of Huang et al. [1]. The effect of variation in the time step size for transient simulations is also studied. The time step sizes corresponding to Acoustic Courant numbers of 4, 8 and 16 are tested. Further, two numerical solver options, i.e., pressure based segregated solver and pressure based coupled solver are used in understanding their effect on the solution convergence regarding the number of time steps required to reach the limit cycle of the pressure oscillations. An additional test for reducing the overall simulation time is explored using a truncated (half) calculation domain and applying an appropriate acoustic impedance boundary condition at the truncated location. The simulation results from this test for the equivalence ratio of φ = 0.6 are compared with the simulation results from the corresponding full domain test. Overall, the simulation results compare well with the experimental data and trends are captured accurately. A clear dominant acoustic mode of 4L is observed for the equivalence ratio of 0.6 that compares well with the experimental data. For the equivalence ratio of 0.4, simulation results show that there is no dominant frequency and the energy is distributed among the first five modes. It is consistent with the observations in the experiments. Both combustion models (SDF and FGM) used in this study capture the combustion instabilities accurately. It builds confidence in flamelet based combustion models for the use in combustion instability modeling which is traditionally done using finite rate chemistry models based on reduced kinetics.
Prediction of Geometrically Induced Localization Effects Using a Subset of Nominal System Modes
Authors: Maywald Thomas , Heinrich Christoph R. , Kühhorn Arnold , Schrape Sven , Backhaus Thomas 
Published: November 2019

Abstract
It is widely known that the vibration characteristics of blade integrated discs can dramatically change in the presence of manufacturing tolerances and wear. In this context, an increasing number of publications discuss the influence of the geometrical variability of blades on phenomena like frequency splitting and mode localization. This contribution is investigating the validity of a stiffness modified reduced order model for predicting the modal parameters of a geometrically mistuned compressor stage. In detail, the natural frequencies and mode shapes, as well as the corresponding mistuning patterns, are experimentally determined for an exemplary rotor. Furthermore, a blue light fringe projector is used to identify the geometrical differences between the actual rotor and the nominal blisk design. With the help of these digitization results, a realistic finite element model of the whole compressor stage is generated. Beyond that, a reduced order model is implemented based on the nominal design intention. Finally, the numerical predictions of the geometrically updated finite element model and the stiffness modified reduced order model are compared to the vibration measurement results. The investigation is completed by pointing out the benefits and limitations of the SNM-approach in the context of geometrically induced mistuning effects.
Aeroelastic and Aerodynamic Investigation of a Low Pressure Turbine Under the Influence of a Circumferential Inlet Distortion
Authors: Simonassi L. , Zenz M. , Bruckner P. , Heitmeir F. , Marn A. 
Published: November 2019

Abstract
Modern low pressure turbine (LPT) architectures of aero engines are designed in order to optimize weight, decrease the fuel consumption and noise emissions. This can be achieved with the use of lighter materials or by reducing the size of the engine. In particular, decreasing the axial distances between the blade rows and shortening the turbine centre frame. As a consequence, it becomes more and more important to investigate the influence of inflow circumferential distortions of total pressure and temperature that can be originated by struts, flow injections and measurement instrumentation.
This work presents the results of an experimental investigation on the influence of total pressure inflow inhomogeneity on the aerodynamics and on the vibrations of a low pressure turbine stage. The measurements were carried out in a one and a half stage subsonic test turbine facility at nominal engine relevant operating conditions and during speed transient operation, including a resonance crossing. Steady and unsteady aerodynamic measurements were performed with a five-hole-probe (5HP) and a fast response aerodynamic pressure probe (FRAPP) respectively, while the LPT rotor vibration data were acquired using strain gauges applied on different blades, in combination with a telemetry system. Analysis in the frequency domain as well as a curve fitting method were applied to estimate the blades forced response and the critical damping. It will be shown that the distortion creates steady and unsteady aerodynamic alterations, causing direct effects on the rotor vibration characteristics.
Development of a CFD Methodology to Reproduce the Effects of Macro Turbulence on Wind Turbines and its Application to the Particular Case of a VAWT
Authors: Balduzzi Francesco , Zini Marco , Ferrara Giovanni , Bianchini Alessandro 
Published: November 2019

Abstract
Based on existing reports and databases, most of the installations in highly turbulent sites in fact fail to reach the expected energy yield, resulting in still or underperforming turbines that also give bad press for the technology. A better understanding of the real performance of wind turbines under highly turbulent conditions is then pivotal to ensure the economic viability of new installations. To this end, the possible use of Computational Fluid Dynamics (CFD) techniques could provide notable benefits, reducing the time-to-market and the cost with respect to experiments. On the other hand, it is intrinsically not easy to reproduce properly intense and large-scale turbulence with the techniques of common use for research and industry (e.g. CFD unsteady RANS), while the only methods that are granted to do so (e.g. DNS or LES) are often not computationally affordable. Moving from this background, this study presents the development a numerical strategy to exploit at their maximum level the capabilities of an unsteady Reynolds-Averaged Navier-Stokes (RANS) approach in order to reproduce fields of macro turbulence of use for wind energy applications. The study is made of two main parts. In the first part, the numerical methodology is discussed and assessed based on real wind tunnel data. The benefits and drawbacks are presented also in comparison to other existing methods. In the second part, it has been used to simulate the behavior under turbulence of a H-Darrieus vertical-axis wind turbine, for which unique wind tunnel data were available. The simulations, even if preliminary, showed good matching with experiments (e.g. confirming the increase of power), showing then the potential of the method.
Adaptive Control of Micro Gas Turbine for Engine Degradation Compensation
Authors: Zaccaria Valentina , Ferrari Mario L. , Kyprianidis Konstantinos 
Published: November 2019

Abstract
Micro gas turbine engines in the range of 1–100 kW are playing a key role in distributed generation applications, due to the high reliability and quick load following that favor their integration with intermittent renewable sources. Micro-CHP systems based on gas turbine technology are obtaining a higher share in the market and are aiming at reducing the costs and increasing energy conversion efficiency. An effective control of system operating parameters during the whole engine lifetime is essential to maintain desired performance and at the same time guarantee safe operations. Because of the necessity to reduce the costs, fewer sensors are usually available than in standard industrial gas turbines, limiting the choice of control parameters. This aspect is aggravated by engine aging and deterioration phenomena that change operating performance from the expected one. In this situation, a control architecture designed for healthy operations may not be adequate anymore, because the relationship between measured parameters and unmeasured variables (e.g. turbine inlet temperature or efficiency) varies depending on the level of engine deterioration. In this work, an adaptive control scheme is proposed to compensate the effects of engine degradation over the lifetime. Component degradation level is monitored by a diagnostic tool that estimates performance variations from available measurements; then, the information on the gas turbine health condition is used by an observer-based model predictive controller to maintain the machine in a safe range of operation and limit the reduction in system efficiency.
Multi-Physics Simulation Based Approach for Life Prediction of a Gas Turbine Combustor Liner
Authors: Shrivastava Sourabh , Andrade Prem , Carpenter Vinay , Masal Ravindra , Nakod Pravin , Orsino Stefano 
Published: November 2019

Abstract
Better life assessment of hot-components of an aero-engine can help improve its reliability and service life, while, reducing associated maintenance cost. Accurate prediction of Thermo-Mechanical Fatigue (TMF) is one of the crucial aspects of life prediction. Therefore, fully resolved simulation methodologies have gained attention as an ingredient for solving TMF problems owing to their potential for providing comprehensive insights into a system having hot components undergoing transient loading during operation.
The present work focuses on a multi-physics simulation-based approach for the life-prediction of a representative gas-turbine combustor liner with an objective of providing a complete framework for TMF analysis of an actual aero-engine combustor liner. The presented methodology consists of a coupling between Computational Fluid Dynamics (CFD) and Finite Element Method (FEM). Thermal loads on the representative aero-engine combustor are predicted using Conjugate Heat Transfer (CHT) modeling in the CFD analyses for different operating conditions suitable for a flight cycle. A load cycle is then constructed using these thermal loads and is transferred to the structural analysis to evaluate the stresses in the liner. Results are obtained regarding spatially varying thermal expansion resulting in inelastic strains as governed by temperature and rate dependent material behavior. Stress and plastic strain history information from the structural analysis are processed to predict the life of different regions of the combustor liner. Different simulation methods for conjugate heat-transfer, load-cycle, material property extraction, thermal-stresses, and fatigue are evaluated, and an overall methodology involving accuracy and reasonable computational cost is proposed. The proposed methodology is numerically verified, and the verification results are presented in this work.