bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of U.S. Navy Rolls Royce 501-K34 Turbine Engine Removals 2008 to 2018
Authors: Russom Dennis , Patterson Jeffrey , Pineiro Ivan 
Published: November 2019

Abstract
The Rolls Royce 501-K34 gas turbine engine serves as the prime mover in the Ship Service Gas Turbine Generators (SSGTGs) of the U.S Navy’s USS ARLEIGH BURKE (DDG 51) Class Flight I and Flight II ships. At the time of this writing, there are 65 ships and 195 shipboard 501-K34 turbine engines which operate a total of about 400,000 hours per year. Engines periodically require removal from ships for depot repair. This paper discusses the guidelines that govern the removal process then discuss the 156 engine removals that occurred between January 2008 and November 2018.
Analysis of a Combined Cycle Exploiting Inlet Conditioning Technologies for Power Modulation
Authors: Sorce Alessandro , Giugno Andrea , Marino Daniela , Piola Stefano , Guedez Rafael 
Published: November 2019

Abstract
The high share of non-dispatchable renewable energy source generators in the electrical grid has increased the need for flexibility of Gas Turbine Combined Cycles (GTCC) already installed. To maximize not only the maximum power produced, via Power Augmentation Technologies (PATs), but also to reduce the Minimum Environmental Load (MEL), both OEMs and GTCC owners have adopted several technical solutions. This kind of flexibility has become, year-by-year, ever more crucial to guarantee GTCC economical sustainability. Amongst the solutions which can be adapted to guarantee GTCC flexibility, the Inlet Conditioning System is a particularly interesting technical solution, which can be installed without restrictions related to the different GT design.
In this paper, an evaluation of the compressor inlet temperature effect over the Combined Cycle performance is presented, with a focus on the bottoming Cycle impact. Different Inlet Conditioning Strategies are then compared considering the energy, and the environmental impact on GTCC behavior. The performance of a layout including a Thermal Energy Storage (TES) and a Heat Pump (HP) is then evaluated and compared to other technical solutions.
Thermo-Acoustic Analysis of a Realistic Liquid-Fueled GT Combustor
Authors: Graham Owen , Magina Nicholas , Wickersham A. J. , Han Fei , Sorato Sebastiano , Bethke Sven 
Published: November 2019

Abstract
Thermo-acoustic instabilities are an important consideration in the design of modern power generation gas turbine combustors. While the design process must consider many competing requirements, such as temperature profiles, emissions, robustness to auto-ignition and flameholding, thermoacoustics is one of the most challenging to predict, and therefore design for. This is particularly true in the case of liquid-fueled systems, where the phenomenon results from a complex system of coupled multi-physics phenomena: fuel atomization and transport, mixing, reactive kinetics and acoustics. Nevertheless, emissions-compliant liquid fuel capability is becoming increasingly important to GT operators, thus it is critical to be able to predict the thermoacoustic instabilities of these combustors.
In this work we present an approach to model the thermoacoustic feedback loop for a realistic liquid fuel nozzle in a single burner configuration. The approach is based on an analytical liquid-fuel diffusion flame model to provide the fluctuating heat release response to inflow perturbations. This is coupled with a 3D FEM description of the acoustic response of the single burner rig through a time-domain Green’s function model to predict the growth and saturation of pressure oscillations. The necessary flame model parameters are calibrated based on a range of test data obtained from the single burner rig with a tunable combustor length. The results are shown to compare well with test data across a range of operating conditions, and for two different nozzle geometries.
Improving Aerodynamic Performance of a Highly Loaded Compressor Based on Coanda Jet Flap
Authors: Du Juan , Li Yiwen , Li Zhihui , Li Jichao , Wang Zinan , Zhang Hongwu 
Published: November 2019

Abstract
A novel blowing flow control technique, called Coanda jet flap, to improve the performance of the highly loaded axial compressor is numerically and experimentally investigated in this study. A theoretical model is initially built to guide the preliminary design of the jet velocity. The design and effectiveness of the Coanda jet flap are then studied for two different blade designs: a highly-loaded double-arc blade cascade and a highly-loaded axial compressor stator. The optimal aerodynamic shape of the Coanda jet flap is achieved based on the genetic algorithm in conjunction with the artificial neural networks. A comparison of the flow details between the optimization result and the prototype is then conducted to understand the flow mechanisms responsible for the performance enhancement. The numerical and experimental results show that the Coanda jet effectively improves the aerodynamic performance of the highly loaded cascade. The total pressure loss is reduced by a maximum of 22.4% when the normalized mass flow rate of Coanda jet is equal to 1%. Meanwhile, the static pressure rise coefficient is increased by up to 14% with a 1.5% jet mass flow rate. The cantilevered stator vanes with Coanda jet flap is well-designed and embedded in a 1.5-stage highly loaded axial compressor stage. The numerical data shows that the total number of stator blades can be successfully reduced by 35% with the uncompromised overall performance when the Coanda jet flap is applied.
The Effect of Heat Transfer on Turbine Performance
Authors: Jardine Lachlan J. , Miller Robert J. 
Published: November 2019

Abstract
For over 50 years, high-pressure gas turbine blades have been cooled using air bled from the compressor. This cooling results in very high rates of heat transfer, both within the fluid and within the blade. The heat transfer often occurs across large differences in temperature and thus is highly irreversible. It is therefore surprising that little is understood about the effect of this heat transfer on turbine performance. This paper solves this problem by applying a new method known as mechanical work potential, or euergy, analysis. The key consequence of the analysis is that the value placed on all heat, relative to work, becomes set by the Joule (Brayton) cycle efficiency. This means that when heat is transferred locally within a flow, or when viscous reheat occurs, the value of this heat should be set by the Joule cycle efficiency. This paper demonstrates how the new method can be implemented both in the preliminary design systems and in the analysis of conjugate CFD solutions of complex engine representative components. The new method provides the cooling designer with a new way of raising turbine efficiency, a form of recuperation locally in the flow. This method offers the exciting potential to design cooling systems that, when added to a blade profile, actually reduces profile loss by up to 7.3%.
Steady Conjugate Heat Transfer Method for High Temperature Gradient in Turbomachinery Applications
Authors: Salem Rami , Marty Julien , Errera Marc 
Published: November 2019

Abstract
The high-pressure (HP) turbine and compressor blades are subjected to severe aero-thermal loads either caused by high inlet temperature resulting from the combustion chamber or by the shock wave at the blade surface. In this paper, a partitioned conjugate heat transfer (CHT) approach is used to assess 3D cases with high temperature gradient. On one hand, the high temperature resulting from the combustion chamber generates high azimuthal and radial non uniformities on the nozzle guide vane (NGV), known as hot streak. Since the engine efficiency is directly related to the turbine inlet temperature, manufacturers are seeking to improve thermal barrier coatings (TBC) to allow higher temperature. On the other hand, compressor rotor blades are also subjected to high thermal loads caused by the shock waves. Since the shock wave substantially contributes to the heat transfer, an accurate prediction of the wall temperature is thus required in order to properly estimate the rotor efficiency. However, the thermal load gradient caused by the hot streak, the use of thermal barrier coating or the shock wave have an impact on the overall computation stability. This paper assess the stability for a Dirichlet-Robin interface condition. Indeed an optimal relaxation parameter value is given for the Robin condition to provide a stable CHT computation. The impact on stability of the transient coupling time-step, the coupling frequency and the thermal conductivity is also assessed and the new transient coupling time-step defined allows to correctly stabilize the coupled simulation.
Impact of Different Volume Sizes on Dynamic Stability of a Gas Turbine Fuel Cell Hybrid System
Authors: Abrassi Alessio , Traverso Alberto , Tucker David , Liese Eric 
Published: November 2019

Abstract
A dynamic model is developed for a Micro Gas Turbine (MGT), characterized by an intrinsic free-spool configuration, coupled to large volumes. This is inspired by an experimental facility at the National Energy Technology Laboratory (NETL) called Hyper, which emulates a hybrid MGT and Fuel Cell system. The experiment and model can simulate stable and unstable operating conditions. The model is used to investigate the effects of different volumes on surge events, and to test possible strategies to safely avoid or recover from unstable compressor working conditions. The modelling approach started from the Greitzer lumped parameter approach, and it has been improved with integration of empirical methods and simulated components to better match the real Hyper plant layout and performance. Pressure, flow rate, and frequency plots are shown for the surge behavior comparing two different volume sizes, for cases where gas turbine shaft speed is uncontrolled (open loop) and controlled (closed loop). The ability to recover from a surge event is also demonstrated.
Physics-Based Part Orientation and Sentencing: A Solution to Manufacturing Variability
Authors: Lee Wen Yao , Dawes William N. , Coull John D. 
Published: November 2019

Abstract
Casting deviations introduce geometric variability that impacts the aerodynamic performance of turbomachinery. These effects are studied for a High Pressure Turbine (HPT) rotor blade from a modern aero-engine. 197 blades were measured using three-dimensional structured-light scanning (GOM scanning), and the performance of each blade is quantified using Reynolds-Averaged Navier-Stokes (RANS) simulations.
Casting variation is typically managed by applying geometric tolerances to determine the suitability of a component for service. The analysis demonstrates that this approach may not be optimal since it does not necessarily align with performance, in particular the capacity and efficiency. Alternatively, functional acceptance based on the predicted performance of each blade removes the uncertainty associated with geometric tolerancing and gives better performance control.
Building on these findings, the paper proposes a method to set the orientation of the fir-tree, which is machined after casting. By customizing the alignment of each blade, performance variability and scrap rates can be significantly reduced. The method uses predictions of performance to reorient the castings to compensate for the manufacturing-induced errors, without changing the design-intent blade geometry and with minimal changes to the manufacturing facility.
Time Domain Bloch Boundary Conditions for Efficient Simulation of Thermoacoustic Limit-Cycles in (Can-)Annular Combustors
Authors: Haeringer Matthias , Polifke Wolfgang 
Published: November 2019

Abstract
Thermo-acoustic eigenmodes of annular or can-annular combustion chambers, which typically feature a discrete rotational symmetry, may be computed in an efficient manner by utilizing the Bloch-wave theory. Unfortunately, the application of the Bloch-wave theory to combustion dynamics has hitherto been limited to the frequency domain.
In this study we present a time domain formulation of Bloch boundary conditions (BBC), which allows to employ them in time domain simulations, e.g. CFD simulations. The BBCs are expressed as acoustic scattering matrices and translated to complex-valued state-space systems. In a hybrid approach an unsteady, compressible CFD simulation of the burner-flame zone is coupled via characteristic-based state-space boundary-conditions to a reduced order model of the combustor acoustics that includes BBCs. The acoustic model with BBC accounts for cross-can acoustic coupling and the discrete rotational symmetry of the configuration, while the CFD simulation accounts for the nonlinear flow-flame-acoustic interactions. This approach makes it possible to model limit cycle oscillations of (can-)annular combustors at drastically reduced computational cost compared to CFD simulations of the full configuration, and without the limitations of weakly nonlinear approaches that utilize a flame describing function.
In the current study the suggested approach is applied to a generic multi-can combustor. Results agree well with a fully compressible CFD simulation of the complete configuration.
Reducing Compressor Shroud Leakage Flows by Raising the Stator Hub Line: Low Speed Tests
Authors: Schrapp Henner , Dodegge Arne , Gümmer Volker , Harvey Neil W. , Städing Jörn , Friedrichs Jens 
Published: November 2019

Abstract
The paper describes experimental investigations of an alternative shrouded stator concept in a 2.5 stage low speed compressor. The idea of this new concept is to raise the stator hub line by a small amount, thus decelerating the flow upstream of the shroud cavity due to the into wind step and raising the static pressure. Downstream of the cavity the out of wind step changes the streamline curvature thus lowering the static pressure locally. As a result, the static pressure difference across the shroud is lower and the shroud flow is reduced. Tests were done at three seal gap heights under stator 1, both with a “neutral” (in–line) hub and a six percent “bump shroud”, i.e. the hub is raised by six percent annulus height.
Performance measurements show the impact of the “bump shroud” geometry on the overall behavior of the compressor, i.e. efficiency and pressure ratio and the variation of these quantities with varying seal gap height. While the efficiency and pressure ratio of the compressor inevitably reduce with increasing seal gap height, the sensitivity of both is reduced by using “bump shrouds”. At small seal gap heights the “bump shroud” design behaves similarly to the neutral one, while at the design seal gap height it is superior. Thus, both the efficiency and the pressure ratio are less sensitive against seal gap height variations if the compressor is equipped with a raised hub line — leading to a more robust product. A similar behavior is seen at near stall conditions.
The analysis of five hole probe measurements reveals the reason for the improved efficiency. The stator 1 losses were significantly reduced by the introduction of the “bump shroud”. This is mostly due to the reduced amount of shroud flow and the subsequent reduction of hub cross–flow in the stator. A comparison of losses with and without the raised hub line show not only a reduction of the losses near the hub, but also adjacent to the suction side of the stator due to reduced migration of hub boundary layer fluid onto the vane.
Impact of Fluid Substitution on the Performance of an Axial Compressor Blade Cascade Working With Supercritical Carbon Dioxide
Authors: Muñoz Alejandro , Sánchez David , Savill Mark , Kipouros Timoleon , Tello-Castillo Carlos 
Published: November 2019

Abstract
Recent research on turbomachinery design and analysis for supercritical Carbon Dioxide (sCO2) power cycles has relied on Computational Fluid Dynamics. This has produced a large number of works whose approach is mostly case-specific, rather than of general application to sCO2 turbomachinery design.
As opposed to such approach, this work explores the aerodynamic performance of compressor blade cascades operating on air and supercritical CO2 with the main objective to evaluate the usual aerodynamic parameters of the cascade for variable boundary conditions and geometries, enabling ‘full’ or ‘partial’ similarity. The results present both the global performance of the cascades and certain features of the local flow (trailing edge and wake). The discussion also highlights the mechanical limitations of the analysis (forces exerted on the blades), which is the main restriction to applying similarity laws to extrapolate the experience gained through decades of work on air turbomachinery to the new working fluid.
This approach is a step towards the understanding and appropriate formulation of a multi-objective optimisation problem for the design of such turbomachinery components where sCO2 is used as the operating fluid. With this objective, the paper aims to identify and analyse what would be expected if a common description of such computational design problems similar to those where air is the working fluid were used.
Conceptual Flutter Analysis of Stepped Labyrinth Seals
Authors: Corral Roque , Vega Almudena , Greco Michele 
Published: November 2019

Abstract
A simple non-dimensional model to describe the flutter onset of two-fin straight labyrinth seals [1] is extended to stepped seals. The effect of the axial displacement of the seal is analyzed first in isolation. It is shown that this fundamental mode is always stable. In a second step, the combination of axial and torsion displacements is used to determine the damping of modes with arbitrary torsion centers. It is concluded that the classical Abbot’s criterion stating that seals supported in the low-pressure side of the seal are stable provided that natural frequency of the mode is greater than the acoustic frequency breaks down under certain conditions. An analytical expression for the non-dimensional work-per-cycle is derived and new non-dimensional parameters controlling the seal stability identified. It is finally concluded the stability of stepped seals can be assimilated to that of a straight through seal if the appropriate distance of the torsion center to the seal is chosen.
Non-Dimensional Parameters for Comparing Conventional and Counter-Rotating Turbomachines
Authors: Waldren J. J. , Clark C. J. , Grimshaw S. D. , Pullan G. 
Published: November 2019

Abstract
Counter-rotating turbomachines have the potential to be high efficiency, high power density devices. Comparisons between conventional and counter-rotating turbomachines in the literature make multiple and often contradicting conclusions about their relative performance. By adopting appropriate non-dimensional parameters, based on relative blade speed, the design space of conventional machines can be extended to include those with counter-rotation. This allows engineers familiar with conventional turbomachinery to transfer their experience to counter-rotating machines. By matching appropriate non-dimensional parameters the loss mechanisms directly affected by counter-rotation can be determined.
A series of computational studies are performed to investigate the relative performance of conventional and counter-rotating turbines with the same non-dimensional design parameters. Each study targets a specific loss source, highlighting which phenomena are directly due to counter-rotation and which are solely due to blade design. The studies range from two-dimensional blade sections to three-dimensional finite radius stages. It is shown that, at hub-to-tip ratios approaching unity, with matched non-dimensional design parameters, the stage efficiency and work output are identical for both types of machine. However, a counter-rotating turbine in the study is shown to have an efficiency advantage over a conventional machine of up to 0.35 percentage points for a hub-to-tip ratio of 0.65. This is due to differences in absolute velocity producing different spanwise blade designs.
A Step Towards an Intelligent Aerodynamic Design Process
Authors: Clark Christopher J. 
Published: November 2019

Abstract
A new type of section inverse design is presented that offers a 200 times speed up over conventional iterative methods. The method parametrises a blade section in terms of its aerodynamic duty and design style. The duty is defined by the inlet and outlet flow angles, and the Mach and Reynolds numbers at which the blade must operate. The aerodynamic style is represented by a normalised Mach number distribution, parametrised by four control variables. This is found to provide a wide range of desirable loading distributions.
For a given style and duty, the method obtains the section geometry and its performance using a radial basis function network. This network is trained, a priori, on a database of designs produced using a conventional inverse design method. The database covers a range of inlet and exit angles for a range of Mach numbers, at each duty aerofoil families are produced varying the four style parameters. During the database production the radial basis function (RBF) network is sequentially refitted and used to accelerate future designs convergence by providing an increasingly better initial guess.
Errors in prediction accuracy, of the fully trained system, are calculated by evaluating the obtained geometry and comparing its aerodynamic performance with the intent. The average exit flow angle error was calculated to be 0.074° from the intent. The root-mean-squared error between intent and achieved Mach fraction distributions averaged below 0.0275. The loss prediction featured average errors of 0.012% and hence provides a very accurate method of performance estimation.
It is highlighted that not all combinations of aerodynamic duty and design style are compatible. “Infeasible” regions within the design space where the aerodynamic intent is not possible exist. A method is applied to avoid these regions, where section errors are above average, ensuring accurate section generation.
Simulation, Test and Mitigation of 1/2X Forward Whirl Following Rotor Drop Onto Auxiliary Bearings
Authors: Kang Xiao , Palazzolo Alan 
Published: November 2019

Abstract
1/2X forward whirl repeatedly occurred after a test rotor spinning at 5,800 rpm was dropped onto ball bearing type auxiliary bearings AB, utilized as a backup for magnetic bearings. The measured contact forces that occurred between the rotor and the auxiliary bearing during the ½X subsynchronous vibration were about thirteen times larger than the static reaction force. The vibration frequency coincided with the rotor-support system natural frequency with the rotor at rest on the auxiliary bearing AB, an occurred at ½ of the rotor spin speed when dropped. The test rig provided measurements of rotor-bearing contact force, rotor orbit (vibrations), and rotational speed during rotor drop events. A simulation model was also developed and demonstrated that parametric excitation in the form of a Mathieu Hill model replicated the measured 1/2X forward whirl vibrations. The simulation model included a nonlinear, elastic-thermal coupled, ball bearing type auxiliary bearing model. The transient model successfully predicted the 1/2X vibration when the rotor was passing 5800RPM as well, and the simulation results quantitatively agreed well with the test results in the frequency domain. Several approaches for mitigating the 1/2X forward whirl were presented such as adding an elastomer O-ring or waviness spring in the AB support system. Measurements confirmed that adding AB dampers effectively mitigated the ½ subsynchronous forward whirl and significantly reduced the contact forces.