bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Tuned Vibration Absorber Concept to Blisk Ring Dampers: A Nonlinear Study
Authors: Lupini Andrea , Mitra Mainak , Epureanu Bogdan I. 
Published: November 2019

Abstract
In this study, a novel design for ring dampers is proposed, where the concept of tuned vibration absorbers is leveraged to substantially increase damper effectiveness while minimizing potential stresses near the blade root. Tuned absorbers have been used in the past to reduce the forced response amplitudes of both mechanical and civil structures. The absorber natural frequency is tuned to the targeted frequency of the host structure where it is attached. The vibration reduction mechanism relies on energy transfer from the host structure to the absorber. The novel design technique proposed here uses a vibration absorber approach to achieve energy transfer from the blisk to the damper, which leads to larger damper motion. This enables energy dissipation due to friction, reducing vibrations even in blade dominated modes. An academic finite element model of a blisk with a ring damper is used to demonstrate the novel tuned damper concept and design technique. The geometric mistuning of the damper due to the presence of a gap in the ring structure is also taken into account. The results demonstrate the validity of the proposed tuned damper concept, showing a substantial vibration amplitude reduction compared to the linear baseline results, in which the damper is not tuned or absent.
Novel and Applicable Method to Determine Equivalent Strain Range and Equivalent Strain Direction Under Multiaxial Non-Proportional Loading
Authors: Krouse Charles R. , Musgrove Grant O. , Kim Taewoan , Lee Seungmin , Lee Muhyoung 
Published: November 2019

Abstract
When considering mechanical components that are subjected to complex loading conditions, it is difficult to achieve accurate predictions of low-cycle fatigue life. For multiaxial and non-proportional loads, the principal strain directions vary in three-dimensional space with time. The commonly accepted methods to determine fatigue life under such loading conditions are based on a critical plane approach, and they rely heavily on accurate strain range estimates. However, there is no singly accepted method to determine the critical plane, equivalent strain magnitude, or equivalent strain direction. Furthermore, current suggestions are computationally intensive and challenging to implement. This paper offers a novel and concise method to accurately determine equivalent strain range and equivalent strain direction under multiaxial, non-proportional loading in three-dimensional space. A practical approach is provided for implementing the method, and an example of an application using a finite element model of a first stage turbine blade is discussed. To demonstrate the approach, ANSYS Mechanical was used to simulate a turbine blade under transient loading conditions and to determine the resulting strains. Equivalent strain range results were applied to a Coffin-Manson relation to determine the low-cycle fatigue life of every node within the finite element model of the first stage turbine blade. The post-processing of the strain predictions, which yielded the equivalent strain range and equivalent strain direction, is discussed in detail.
80 Years Open GT Development in Baden
Authors: Wettstein Hans E. 
Published: November 2019

Abstract
On 07.07.1939 the Neuchatel gas turbine passed its performance test under the supervision of Aurel Stodola [1]. This was the world’s first open gas turbine for electric power generation in commercial operation. It launched the past eighty year period of further development and corresponding market growth. The Baden area played an important role.
The aim of this paper is to complete the already published comprehensive historical information with two additional aspects especially regarding the second 40 years, in which the author was an involved contemporary witness:
The first is how the predominance of something like a local spirit integrated both a considerable share of foreign engineering staff and also the changes of the ownership of the technology from Brown Boveri to ABB and then to Alstom and recently to GE and Ansaldo.
The second aspect is the inside view of the author, who has both shaped and suffered these gas turbine developments in several job positions allowing direct contact to both top management and shop floor workers.
These two aspects will be integrated in the historical sequence. As a rule the roles of the persons acting after the seventies are given but not their names.
The history of the involved companies has caught much attention of media and writers. After the formation of ABB it was used for both celebrating outstanding management performance and despicable management mistake. I will add as an engineer my insider view to this and mention the corresponding book references.
This paper is limited to the mainstream open GT development for space reasons and therefore omits other interesting side developments of BBC such as closed Helium cycles, IGCC applications and compressed air energy storage as well as the other products of BBC, which all played a role in equalizing the business cycles.
On the Frequency Dependency of Tilting-Pad Journal Bearings
Authors: Wagner Laurence F. 
Published: November 2019

Abstract
Controversy regarding the dynamic modeling of tilting-pad journal bearings (TPJB) has existed for years, with the question of the effective stiffness and damping properties, and the requirement for consideration of frequency dependency, being of great concern. There is a partial disconnect between the results of theoretical and many experimental investigations. This paper attempts to examine this issue in more of a macro sense; broadening the scope of the geometric and operating domains, and in turn expanding an understanding of related frequency effects. The investigation hinges on a single-pad, single degree-of-freedom (DOF) model that represents various geometries and operating conditions for a full bearing. The results clearly show that the dynamic coefficients must be dependent upon the “exciting” frequency, and that the dependency is primarily associated with the pad rotational damping.
Offshore Experience With Thermal Turbomachinery in Norwegian Petroleum Industry Through Fifty Years: A Review of Major Milestones, Lessons Learned and Impacts
Authors: Lynghjem Arne , Bakken Lars E. , Naess Tore 
Published: November 2019

Abstract
From the beginning of the offshore oil & gas industry in Norway in 1969, the applications of thermal turbomachinery did often involve new and innovative conceptual solutions. In some cases they had to be followed by extensive modifications on the offshore platforms afterwards, which have resulted in valuable lessons learned.
The list of offshore challenges for thermal turbomachinery has gradually increased over time. The initial challenges involved very high pressure gas compression, low weight machinery, small footprints, low offshore maintenance needs, reliable and safe operation. Later, it also involved strict environmental regulations, reduced emissions, remote control, subsea and multiphase operations.
This paper reviews major technological milestones for offshore application of thermal turbomachinery over five decades. Further, it presents a collation of the experiences that have been made and discussions of their impact on other applications.
The intension of the paper is to transfer experience, and the target group is young engineers and other engineers working with thermal turbomachinery in oil & gas industry.
Initially, the technological milestones were achieved on improvement of centrifugal compressor instabilities in high pressure application, the shift from large heavy duty gas turbines to aeroderivatives and pioneering work on Norwegian small gas turbines. It was followed by a clear trend from gas turbine to electric motor drive, preferably variable speed drive, and a central gas turbine power plant. In the 1990es and beyond, ambitious efforts were made on reduced emissions of CO2 and NOx from gas turbines. Further, achievements were made on dry running gas seals, active magnetic bearings and currently hermetically enclosed compressors without shaft seals. After 2010, the ultimate solution was achieved with combined compressor and electric motor casing, entailing subsea compression and wet gas compression.
Unsteady Passing Wake Effects on Turbine Blade Tip Aerodynamic and Aerothermal Performance With Film Cooling
Authors: Zhang Bo , Qiang Xiaoqing , Teng Jinfang , Lu Shaopeng 
Published: November 2019

Abstract
In this paper, upstream unsteady passing wake effects on the rotor blade tip with film cooling have been numerically examined. The geometry and flow conditions of the first stage of GE-E3 high-pressure turbine have been used to obtain the unsteady three-dimensional blade tip flow and heat transfer characteristics. The first stage of GE-E3 high-pressure turbine has 46 guide vanes and 76 rotor blades. In the process of calculation, compromise the computational resources and accuracy to simplify the number of the guide vane and rotor blade to 38:76. Namely, each computational domain comprises of one guide vane and two rotor blades. The computational boundary conditions are consistent with the GE-E3 annular cascade test conditions. In the case of 1% blade span tip clearance, through comparing the steady results, time-averaged and time-resolved unsteady results, the investigation of the unsteady passing wake effects on flat tip aerodynamic and aerothermal performance without film cooling holes (NC) and three cases with film cooling holes are conducted. To be specific, near the leading edge (C123), at the central area (C456) and near the trailing edge (C789). This paper emphasizes the variation of leakage flow and heat transfer coefficient at different unsteady instants. The results show that the time-averaged leakage flow is pretty similar to the steady results, but the increment of the leakage flow can rise to more than 8% at the maximum envelope. Moreover, the heat transfer coefficient discrepancy between steady results and time-averaged results is almost below 4%, but the dramatic growth of the instantaneous heat transfer coefficient along the pressure side is in excess of 20% due to the shift of the pressure spot.
Successive Aeroacoustic Transfer of Leading Edge Serrations From Single Airfoil to Low-Pressure Fan Application
Authors: Biedermann Till M. , Kameier F. , Paschereit C. O. 
Published: November 2019

Abstract
Leading edge serrations are identified as an effective passive treatment for reducing fan broadband noise due to high turbulent inflow conditions. This paper aim to investigate the isolated effect of serrated applications in a rotating frame, covering the aerodynamic and aeroacoustic performance. With this purpose, a serration design, previously analyzed in the rigid domain, is transferred to the rotating frame, following a successive approach in form of a continuous increase of the fan blade number. This is considered as a feasible way to isolate the serration effects and to provide information on fan blade interaction and possible masking effects. Comparing blades with straight and serrated leading edges by analyzing the spectral noise reduction and the overall level results in deep insights in the underlying noise reduction mechanisms. Furthermore, analysis of phase differences by means of the wall pressure fluctuations leads to the identification of rotating flow phenomena, non-synchronized with the rotor speed. The results obtained indicate an efficient noise reduction by the serrations in the vicinity of the design point. By use of the presented successive approach, noise reduction phenomena observed with the full rotor could be identified to be of either aeroacoustic or aerodynamic nature. A reduced noise is observed for the full rotor case, showing a reduction of blade interaction effects. At reducing flow coefficients, an improved stall margin of the serrated rotor is identified that also affects the aeroacoustic signature.
Experimental Investigation of the Discharge Behavior of Cavitating and Non-Cavitating Flow Through Rotating Radial Orifices
Authors: Cordes Laura , Schwitzke Corina , Bauer Hans-Jörg 
Published: November 2019

Abstract
The transport of a flow from a static system into a rotating system can be realized by means of orifices in the rotating wall. In this paper the experimental study of a liquid flowing through a radial, sharp-edged orifice with a l/d-ratio of 1.56 in a rotating shaft is presented. The discharge coefficient cd for (circumferential) orifice speeds of up to 24 m s−1 and Reynolds numbers ranging from Red = 1.2 × 104 to 3.4 × 104 is evaluated for an oil with a density of 920 kg m−3 and a kinematic viscosity of 5.3 × 10−6 m s−2.
A modular test rig was designed, consisting of two concentric rotating shafts forming an annular duct. The outer shaft is fitted with the orifices through which the liquid passes from the static into the rotating system. The modularity allows the exchange of the shaft element containing the orifices. For this study two shaft elements with 5 or 12 radial, cylindrical, sharp-edged orifices were used. Thus, a wider range of flow velocities through a single orifice was achieved.
This study is the first to illustrate the effect of cavitation in a rotating orifice. Outside the cavitation regime a change of the approaching flow represented by the velocity ratio causes a change of the discharge coefficient while within the cavitation regime cd additionally depends on the cavitation parameter. A relationship for the flow contraction in the cavitation regime depending on the orifice velocity and the pressures upstream and downstream of the orifice is derived.
For a second set of orifices, where the liquid exits the rotor into the surrounding air, a significant regime change depending on the ratio of orifice rotational speed and flow velocity occurs. For higher flow velocities through the orifice this change occurs for lower orifice speeds. A likely cause is the onset of cavitation.
Erosion Testing of Environmental-Barrier-Coated CMC and its Behavior on an Aero-Engine Turbine Vane Under Particle-Laden Hot Gas Stream
Authors: Okita Yoji , Mizokami Yousuke , Hasegawa Jun 
Published: November 2019

Abstract
Ceramic matrix composite (CMC) has better durability at high temperature and lower material density, as compared to nickel-based super-alloys which have been the standard material for hot section components of aero-engines. Among the CMC materials, SiC-SiC CMC is especially promising with its superior mechanical property at higher temperature. It, however, inevitably needs environmental barrier coating (EBC) to protect the substrate against oxidation. The EBC also needs to have other functions and to meet various requirements. One such very critical requirement is the resistance to sand erosion, although the issue hasn’t been investigated well so far.
The primary contribution of this work is to reveal the erosion resistance of the CMC+EBC material with wind tunnel test data of good quality and to demonstrate what erosion behavior the material exhibits in turbine cascade under particle-laden hot gas stream.
In the present work, erosion tests were first carried out in a testing facility with erosion media of 50 microns silica sand. The tests were conducted under flow velocity of 225 m/s and temperature of 1311 K to simulate typical aero-engine conditions and impact angles of 30, 60, and 80deg were investigated. The obtained data showed a typical brittle erosion mode, where the erosion rate had a positive dependence on the impact angles. A typical erosion model, Neilson-Gilchrist model, was applied to correlate the data and the model was shown to have a good agreement with the experimental data once it was properly calibrated.
Then, the numerical computation solving particle-laden flow was carried out to predict three dimensional flow field and particle trajectories across the target turbine cascade. The erosion profile along the airfoil was calculated based on the obtained trajectories and the calibrated erosion model. The trajectories showed that the particles mostly impinged the airfoil pressure surface first and then the rebounded particles attacked the opposite suction surface as well. Accordingly, the predicted erosion profile showed a broad erosion band across the pressure surface and also some slight erosion peak at around the mid-chord of the suction surface.
Surrogate Model Based Optimization for Chevron Foil Thrust Bearing
Authors: Untaroiu Alexandrina , Fu Gen 
Published: November 2019

Abstract
Gas foil thrust bearings have been utilized in high speed lightweight machines for many decades. These bearings are environment-friendly and capable of withstanding extreme conditions. However, there are also some challenges for foil thrust bearings at high speed conditions, such as insufficient heat dissipation and thermal management. The heat generated by viscous shearing continues to raise the temperature inside the gas film and may cause failures. Among all the methods to enhance heat dissipation, a promising passive thermal management method is modifying the top foil’s trailing edge shape. This modification will enhance the air mixing in between the bearing pads.
The aim of this study is to identify the optimal design of the top foil trailing edge shape and provide a guideline for future bearing design. A 3-D computational fluid dynamics (CFD) model for a thrust foil bearing was created using ANSYS-CFX software. The trailing edge of the top foil was modified to a chevron shape. A sensitivity study was conducted to investigate the connection between the top foil trailing edge shape and the thermal conditions in the gas film. The maximum temperature inside the air gas film is selected as the output. The design of experiments (DOE) technique was used to generate the sampling points. A surrogate model was generated based on the output data by using the neural network method. The surrogate model was used together with a genetic multi-objective algorithm to minimize the maximal temperature inside the gas film and maximize the load carrying capacity. The optimal design was then compared with the baseline model. Results suggest the optimized trailing edge shape is capable of reducing the temperature inside the gas film. This optimal design approach can be used for improvements of chevron foil thrust bearing design.
The Effect of Isentropic Exponent on Transonic Turbine Performance
Authors: Baumgärtner David , Otter John J. , Wheeler Andrew P. S. 
Published: November 2019

Abstract
The isentropic exponent is one of the most important properties affecting gas dynamics. Nonetheless, its effect on turbine performance is not well known. The paper discusses a series of experimental and computational studies to determine the effect of isentropic exponent on the flow field within a turbine vane. Experiments are performed using a newly modified transient wind tunnel which enables annular cascade testing with a wide range of working fluids and operating conditions. For the present study tests are undertaken using air, CO2, R134a and argon, giving a range of isentropic exponent from 1.08–1.67. Measurements include detailed wall static pressures which are compared with computational simulations. Our results show that over the range of isentropic exponents tested here, the loss can vary by between 20%–35%, depending on vane exit Mach number. The results are important for future turbines operating with real-gas effects and/or those where high gas temperatures can lead to variations in isentropic exponent.
A Multiphase Computational Framework for Deposit Formation and Growth
Authors: Paul Steven , Tafti Danesh , Yu Kuahai 
Published: November 2019

Abstract
Particle deposits that form in gas turbine engines can change flow dynamics and heat transfer, leading to performance degradation. A computational framework that models the coupled behavior of sand deposits with flow and heat transfer is developed. The coupling is done by using a multiphase framework in which a physics based collision model is used to predict the post-collision state-of-the sand particle. The collision model is sensitized to temperature dependent material properties of sand. Particle deposition is determined by the particle’s softening temperature and the calculated coefficient of restitution of the collision. The multiphase treatment facilitates conduction through the porous deposit and the coupling between the deposit and the fluid field.
The coupled framework is used to model the behavior of sand particles in a laminar impinging jet flow field. The temperature of the jet and the impact surface are varied between 1000 to 1600 K, to observe particle behavior under different temperature conditions. The Reynolds number of the jet is varied between 20 to 100 to vary particle Stokes number between 0.5 to 3.2. The coupled framework was found to increase or decrease capture efficiency, when compared to an uncoupled simulation, by as much as 10% depending on the temperature field. Deposits that formed on the impact surface, using the coupled framework, altered the velocity field by as much as 130% but had a limited effect on the temperature field for the short duration of the simulations.
Assessment of the Theta Projection Model for Interpolating Creep Deformation
Authors: Perez Jimmy , Stewart Calvin M. 
Published: November 2019

Abstract
The objective of this study is to assess the ability of the theta projection constitutive model to fit and predict creep deformation curves of P91 alloy. To accomplish this objective; a systematic method of fitting and prediction is applied. A numerical optimization algorithm is written in the MATLAB programming language. Using the algorithm, the theta projection model is calibrated to creep deformation curves collected from the GENIV nuclear materials database managed by Oak Ridge National Laboratory. The data consists of deformation curves recorded from tests conducted at increasing stresses at 3 different temperatures; 1100, 1157 and 1200°F. The calibrated theta material constants are then fit to simplified interpolation functions of temperature and stress. Predictions are made using the calibrated and interpolated theta constants and the results compared.
It is determined that the theta projection model excels at fitting individual creep deformation curves. The trends of calibrated theta constants when examined across multiple creep deformation curves (at varied stress per isotherm) do not maintain consistent behavior when compared to one another. This inconsistency limits the accuracy of the interpolation functions, resulting in poor predictions of creep deformation using said functions.