Accepted Manuscripts

Evgeny Petrov
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037708
For the analysis of essentially nonlinear vibrations it is very important not only to determine whether the considered vibration regime is stable or unstable but also which design parameters need to be changed to make the desired stability regime and how sensitive is the stability of a chosen design of a gas-turbine structure to variation of the design parameters. In the proposed paper, an efficient method is proposed for a first time for sensitivity analysis of stability for nonlinear periodic forced response vibrations using large-scale models structures with friction, gaps and other types of nonlinear contact interfaces. The method allows using large-scale finite element models for structural components together with detailed description of nonlinear interactions at contact interfaces. The highly accurate reduced models are applied in the assessment of the sensitivity of stability of periodic regimes. The stability sensitivity analysis is performed in frequency domain with the multiharmonic representation of the nonlinear forced response amplitudes. Efficiency of the developed approach is demonstrated on a set of test cases including simple models and large-scale realistic blade model with different types of nonlinearities, including: friction, gaps, and cubic elastic nonlinearity.
TOPICS: Stability, Vibration, Sensitivity analysis, Design, Friction, Structural elements (Construction), Gas turbines, Blades, Finite element model
Eric Liese and Stephen E. Zitney
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037709
A generic training simulator of a natural gas combined cycle was modified to match operations at a real plant. The objective was to use the simulator to analyze cycling operations of the plant. Initial operation of the simulator revealed the potential for saturation conditions in the final high pressure superheater as the attemperator tried to control temperature at the superheater outlet during gas turbine loading and unloading. Subsequent plant operational data confirmed simulation results. Multiple simulations were performed during loading and unloading of the gas turbine to determine operational strategies that prevented saturation and increased the approach to saturation temperature. The solutions included changes to the attemperator temperature control setpoints and strategic control of the steam turbine inlet pressure control valve.
Mohamed Fadl, Li He, Peter Stein and Gabriel Marinescu
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037721
Turbine flexible operations with faster startup/shutdowns are required to accommodate emerging renewable power generations. A major challenge in transient thermal design and analysis is the time scale disparity. For natural cooling, the physical process is typically in hours, but on the other hand, the time step sizes typically usable tend to be very small (in seconds or sub-seconds) due to the numerical stability requirement for natural convection as often observed. An issue of interest is what time step sizes can and should be used in terms of stability as well as accuracy? In this work, the impact of flow temporal gradient and its modelling is examined in relation to numerical stability and modelling accuracy for natural convection. A source term based dual-timing formulation is adopted, which is shown to be numerically stable for very large time steps. Furthermore, a loosely coupled procedure is developed to combine this enhanced flow solver with a solid conduction solver for solving unsteady conjugate heat transfer problems for transient natural convection. This allows very large computational time steps to be used without any stability issues, and thus enables to assess the impact of using different time step sizes entirely in terms of a temporal accuracy requirement. Computational case studies demonstrate that the present method can be run stably with a markedly shortened computational time compared to the baseline solver. The method is also shown to be more accurate than the commonly adopted quasi-steady flow model when unsteady effects are non-negligible.
TOPICS: Transients (Dynamics), Modeling, Natural convection, Flow (Dynamics), Numerical stability, Stability, Renewable energy, Heat transfer, Cooling, Heat conduction, Turbines, Design
Manoj Settipalli, Venkatarao Ganji and Theodore Brockett
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037722
It is often desirable to identify the critical components that are active in a particular mode shape or an operational deflected shape (ODS) in a complex rotordynamic system with multiple rotating groups and bearings. The energy distributions can help identify the critical components of a rotor bearing system that may be modified to match the design requirements. Although the energy expressions have been studied by researchers in the past under specific limited conditions, these expressions require computing the displacements and velocities of all degrees of freedom over one full cycle. They do not address the overall time-dependency of the energies and energy distributions, and their effect on the interpretation of a mode shape or an ODS. Moreover, a detailed finite element formulation of these energy expressions including the effects of anisotropy, skew-symmetric stiffness, viscous and structural damping have not been identified by the authors in the open literature. In this article, a detailed account of orbit characteristics and planarity for isotropic and anisotropic systems is presented. An elegant approach to obtaining time-dependent kinetic and strain energies of a mode shape or an ODS directly from the structural matrices and complex eigenvectors/displacement vectors is presented. The expressions for energy contributed per cycle by various types of damping and the destabilizing skew-symmetric stiffness is also shown. The conditions under which the energies and energy distributions are time-invariant are discussed. An alternative set of energy expressions for an isotropic system is also presented.
Rainer Kurz and Klaus Brun
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037723
The paper discusses the interaction between a centrifugal compressor and the process, and as a result, the control requirements for centrifugal compressor packages. The focus is on variable speed, upstream and midstream applications. The impact of the interaction between system characteristics and compressor characteristics, both under steady state and transient conditions is explained. Also considered are concepts to optimize and control the units. Special attention is given to the issue of surge avoidance. Additionally, the impact of the process and how the process dynamics interact with the compressor is analyzed, categorized, and explained.
TOPICS: Dynamics (Mechanics), Process control, Compressors, Transients (Dynamics), Compression, Steady state, Surges
Michael Stöhr, Kilian Oberleithner, Moritz Sieber, Zhiyao Yin and Wolfgang Meier
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037724
Sudden changes of flame shape are an undesired, yet poorly understood feature of swirl combustors used in gas turbines. The present work studies flame shape transition mechanisms of a bistable turbulent swirl flame in a gas turbine model combustor, which alternates intermittently between an attached V-form and a lifted M-form. Time-resolved velocity fields and 2D flame structures were measured simultaneously using high-speed stereo-PIV and OH-PLIF at 10 kHz. The data analysis is performed using two novel methods that are well adapted to the study of transient flame shape transitions: Firstly, the linear stability analysis (LSA) of a time-varying mean flow and secondly the recently proposed spectral proper orthogonal decomposition (SPOD). The results show that the transitions are governed by two types of instability, namely a hydrodynamic instability in the form of a precessing vortex core (PVC) and a thermoacoustic (TA) instability. The LSA shows that the V-M transition implies the transient formation of a PVC as the result of a self-amplification process. The V-M transition, on the other hand, is induced by the appearance of a TA instability that suppresses the PVC and thereby modifies the flow field such that the flame re-attaches at the nozzle. In summary these results provide novel insights into the complex interactions of TA and hydrodynamic instabilities that govern the shape of turbulent swirl-stabilized flames.
Max Hufnagel, Christian Koch, Stephan Staudacher and Christian Werner-Spatz
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037689
Erosive damage done to jet engine compressor blading by solid particles has a negative influence on the compressor aerodynamic properties and hence decreases performance. The erosive change of shape has been investigated in a multitude of experiments ranging from eroding flat plates to eroding full engines. The basic challenge to transfer the results from very simple tests to real life erosion remains. Up to date measurement techniques today allow closing this gap. The necessary experimental and analytical steps are shown. The erosion resistance of Ti-6Al-4V at realistic flow conditions with fluid velocities ranging from 200 to 400 m/s is used. The erodent used was quartz sand with a size distribution corresponding to standardized Arizona Test Dust A3 (1 to 120 mm). Flat plates out of Ti-6Al-4V were eroded at different impingement angles. The particle velocities and sizes were investigated using a high speed laser shadowgraphy technique. A dimensional analysis was carried out to obtain nondimensional parameters suitable for describing erosion. Different averaging methods of the particle velocity were examined in order to identify a representative particle velocity. Compared to the fluid velocity and the mean particle velocity, the energy averaged particle velocity is found to be the best representation of the erosiveness of a particle stream. The correlations derived from the dimensional analysis are capable of precisely predicting erosion rates for different rig operating points. The results can be applied to the methodology published in [1].
Klaus Brun, Sarah Simons, Rainer Kurz, Enrico Munari, Mirko Morini and Michele Pinelli
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037662
Centrifugal compressor impellers and shafts are subject to severe fluctuating axial and radial forces when operating in surge. These forces can cause severe damage to the close clearance components of a centrifugal compressor such as the thrust and radial bearings, inter-stage and dry gas seals, and balance piston. Being able to accurately quantify the cyclic surge forces on the close clearance components of the compressor allows the user to determine whether an accidental surge event, or emergency shutdown (ESD) transient, has caused damage requiring inspection, repair, or part replacement. For the test, a 700 Hp (~520 kW) industrial air centrifugal compressor was operated in surge at speeds ranging from 7,000 to 13,000 rpm and pressure ratios from 1.2 to 1.8. The axial surge forces were directly measured using axial load cells on the thrust bearings. Suction and discharge pressures, proximity probe axial shaft position, flows, and temperatures were also measured. Time domain and frequency plots of axial vibration and dynamic pulsations showed the impact of the operating conditions on surge force amplitudes and frequencies. A surge severity coefficient was also derived as a simple screening tool to evaluate the magnitude of potential damage to a compressor during surge.
Enrico Munari, Mirko Morini, Michele Pinelli, Klaus Brun, Sarah Simons and Rainer Kurz
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037663
The force acting on centrifugal compressors is an important parameter to be considered throughout the operating life of these turbomachines. During compressor surge these forces can become dangerous for the mechanical and aerodynamic structures. During these rapid transients, surge can develop, generating unsteady forces which can harm the close clearance components of the compressor. Therefore, the capability to predict the characteristics and the dynamics of these surge forces would allow the estimation of the off-design fatigue cycles produced on these components by surge. Currently, no validated method exists to predict the frequency and amplitude of the surge forces and determine the potential damage of these components. A lumped parameter model, developed by using the bond graph approach to predict the dynamic surge fluid-dynamic oscillations, is presented. The model requires the geometry and the steady-state performance maps of the compressor as inputs, together with the piping system configuration characteristics. The simulator, is provided with a supplementary tool to estimate the axial force frequency and amplitude, taking into consideration all the contributions to the axial fluid-dynamic thrust, the stiffness-damping of the thrust bearing and the mass of the rotor. The model was tuned and validated using the test case axial force data. The model has shown good agreement with the experimental results which implies that it can offer significant information about the severity of a surge event and the quantification of the machine performance losses and possible damage to the close clearance components.
TOPICS: Compressors, Surges, Clearances (Engineering), Fluids, Damage, Damping, Design, Lumped parameter models, Rotors, Cycles, Geometry, Piping systems, Steady state, Stiffness, Thrust bearings, Turbomachinery, Oscillations, Dynamics (Mechanics), Fatigue, Thrust, Service life (Equipment), Transients (Dynamics), Equipment performance
Monika Topel, Åsa Nilsson, Markus Jöcker and Björn Laumert
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037664
Electricity market conditions and concentrating solar power technologies call for increased power plant operational flexibility. Concerning the steam turbine component, one key aspect of its flexibility is the capability for fast starts. In current practice, turbine start-up limitations are set by consideration of thermal stress and low cycle fatigue. However, the pursuit of faster starts raises the question whether other thermal phenomena can become a limiting factor to the start-up process. Differential expansion is one of such thermal properties, especially since the design of axial clearances is not included as part of start-up schedule design and because its measurement during operation is often limited or not a possibility at all. The aim of this work is to understand differential expansion behavior during transient operation and to quantify the effect that such operation would have in the design and operation of axial clearances. This was accomplished through the use of a validated thermo-mechanical model that was used to compare differential expansion behavior for different operating conditions of the machine. These comparisons showed that faster starts do not necessarily imply that wider axial clearances are needed, which means that the thermal flexibility of the studied turbine is not limited by differential expansion. However, for particular locations it was also obtained that axial rubbing can indeed become a limiting factor in direct relation to start-up operation. The resulting approach presented in this work serves to avoid over-conservative limitations in both design and operation concerning axial clearances.
TOPICS: Steam turbines, Design, Turbines, Concentrating solar power, Low cycle fatigue, Power stations, Machinery, Thermal stresses, Transients (Dynamics), Thermal properties, Thermomechanics
Charles W. White and Nathan Weiland
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037665
Direct supercritical CO2 (sCO2) power cycles are an efficient and potentially cost-effective method of capturing CO2 from fossil-fueled power plants. These cycles combust natural gas or syngas with oxygen in a high pressure (200-300 bar), heavily-diluted sCO2 environment. The cycle thermal efficiency is significantly impacted by the proximity of the operating conditions to the CO2 critical point (31 °C, 73.7 bar), as well as to the level of working fluid dilution by minor components, thus it is crucial to correctly model the appropriate thermo-physical properties of these sCO2 mixtures. These properties are also important to determining how water is removed from the cycle, and for accurate modeling of the heat exchange within the recuperator. This paper presents a quantitative evaluation of ten different property methods that can be used for modeling direct sCO2 cycles in Aspen Plus®. REFPROP is used as the de facto standard for analyzing high purity indirect sCO2 systems, however, the addition of impurities due to the open nature of the direct-sCO2 cycle introduces uncertainty to the REFPROP predictions, as well as species that REFPROP cannot model. Consequently, a series of comparative analyses were performed to identify the best physical property method for use in Aspen Plus® for direct-fired sCO2 cycles. These property methods are assessed against several mixture property measurements, and offer a relative comparison to the accuracy obtained with REFPROP. The Lee-Kessler-Plocker Equation of State is recommended if REFPROP cannot be used.
TOPICS: Modeling, Carbon dioxide, Thermodynamic power cycles, Cycles, Equations of state, Oxygen, Water, Uncertainty, Supercritical carbon dioxide, Natural gas, Power stations, Syngas, Thermal efficiency, Heat, Fluids, High pressure (Physics)
Xiao Kang and Alan Palazzolo
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037666
The catcher bearing (CB) is a crucial part of the magnetic bearing system. It can support the rotor when the magnetic bearing is shut down or malfunctioning and limit the rotor's position when large vibration occurs. The sleeve bearing has the advantages of a relatively large contact surface area, simple structure and an easily replaced surface. There are already many applications of the sleeve type catcher bearings in the industrial machinery supported by the magnetic bearings. Few papers though provide thorough investigations into the dynamic and thermal responses of the sleeve bearing in the role of a CB. This paper develops a coupled elastic deformation - heat transfer finite element model of the sleeve bearing acting as a CB. A coulomb friction model is used to model the friction force between the rotor and the sleeve bearing. The contact force and 2-D temperature distribution of the sleeve bearing are obtained by numerical integration. To validate the FEM code developed by the author, firstly, the mechanical and thermal static analysis results of the sleeve bearing model are compared with the results calculated by the commercial software, "SolidWorks Simulation". Secondly, the transient analysis numerical results are compared with the rotor drop test results in reference. Additionally, this paper explores the influences of different surface lubrication conditions, different materials on rotor-sleeve bearing's dynamic and thermal behavior. This paper lays the foundation of the fatigue life calculation of the sleeve bearing and provides the guideline for the sleeve type CB design.
TOPICS: Bearings, Rotors, Magnetic bearings, Thermal analysis, Plain bearings, Friction, Finite element model, Lubrication, Heat transfer, Machinery, Coulombs, Simulation, Deformation, Design, Transient analysis, Temperature distribution, Vibration, Computer software, Fatigue life
Behzad Zamanian Yazdi and Daejong Kim
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037667
Air foil bearing (AFB) technology has made substantial advancement during the past decades and found its applications in various small turbomachinery. However, rotordynamic instability, friction and drag during the start/stop, and thermal management are still challenges for further application of the technology. Hybrid air foil bearing (HAFB), utilizing hydrostatic injection of externally pressurized air into the bearing clearance, is one of the technology advancements to the conventional AFB. Previous studies on HAFBs demonstrate the enhancement in the load capacity at low speeds, reduction or elimination of friction and wear during starts/stops, and enhanced heat dissipation capability. In this paper, the benefit of the HAFB is further explored to enhance the rotordynamic stability by employing a controlled hydrostatic injection. This paper presents the analytical and experimental evaluation of the rotordynamic performance of a rotor supported by two three pads HAFBs with the controlled hydrostatic injection, which utilizes the injections at particular locations to control eccentricity and attitude angle. The simulations in both time domain orbit simulations and frequency-domain modal analyses indicate a substantial improvement of the rotor-bearing performance. The simulation results were verified in a high speed test rig (maximum speed of 70,000 rpm). Experimental results agree with simulations in suppressing the subsynchronous vibrations but with a large discrepancy in the magnitude of the subsynchronous vibrations, which is a result of the limitation of the current modelling approach. However, both simulations and experiments demonstrate the effectiveness of the controlled hydrostatic injection on improving the rotordynamic performance.
Konstantinos Gryllias, Simona Moschini and Jerome Antoni
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037638
Condition monitoring assesses the operational health of rotating machinery, in order to provide early and accurate warning of potential failures such that preventative maintenance actions may be taken. To achieve this target, manufacturers start taking on the responsibilities of engine condition monitoring, by embedding health monitoring systems within each engine unit and prompting maintenance actions when necessary. Several types of condition monitoring are used including oil debris monitoring, temperature monitoring and vibration monitoring. Among them, vibration monitoring is the most widely used technique. Machine vibro-acoustic signatures contain pivotal information about its state of health. The current work focuses on one part of the diagnosis stage of condition monitoring for engine bearing health monitoring as bearings are critical components in rotating machinery. A plethora of signal processing tools and methods applied at the time domain, the frequency domain, the time-frequency domain and the time-scale domain have been presented in order to extract valuable information by proposing different diagnostic features. Among others, an emerging interest has been reported on modeling rotating machinery signals as cyclostationary, which is a particular class of non-stationary stochastic processes. The goal of this paper is to propose a novel approach for the analysis of cyclo-nonstationary signals based on the generalization of indicators of cyclostationarity in order to cover the speed varying conditions. The effectiveness of the approach is evaluated on an acceleration signal captured on the casing of an aircraft engine gearbox, provided by SAFRAN.
Luca Mastropasqua, Stefano Campanari and Jack Brouwer
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037639
The modularity and high efficiency at small-scale make high temperature fuel cells an interesting solution for Carbon Capture and Utilisation at the distributed generation scale when coupled to appropriate use of CO2 (i.e., for industrial uses, local production of chemicals etc.). The present work explores fully electrochemical power systems capable of producing a highly pure CO2 stream and hydrogen. In particular, the proposed system is based upon integrating a Solid Oxide Fuel Cell (SOFC) with a Molten Carbonate Fuel Cell (MCFC). The use of these high temperature fuel cells has already been separately applied in the past for CCS applications. However, their combined use is yet unexplored. The reference configuration proposed envisions the direct supply of the SOFC anode outlet to a burner which, using the cathode depleted air outlet, completes the oxidation of the unconverted species. The outlet of the burner is then fed to the MCFC cathode inlet which separates the CO2 from the stream. This layout has the significant advantage of achieving the required CO2 purity for liquefaction and long-range transportation without requiring the need of cryogenic or distillation plants. Furthermore, different configurations are considered with the final aim of increasing the Carbon Capture Ratio (CCR) and maximising the electrical efficiency. Moreover, the optimal power ratio between SOFC and MCFC stacks is also explored. Complete simulation results are presented, discussing the proposed plant mass and energy balances and showing the most attractive configurations from the point of view of total efficiency and CCR.
TOPICS: Separation (Technology), Carbon, Solid oxide fuel cells, Molten carbonate fuel cells, Emissions, Carbon dioxide, Carbon capture and storage, High temperature, Fuel cells, Power systems (Machinery), Anodes, Distributed power generation, Hydrogen, Transportation systems, Electrical efficiency, Liquefaction, oxidation, Simulation results
Zhe Liu and Guillermo Paniagua
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037640
Aerodynamic probes are prevalent in turbomachinery research and gas turbine monitoring. Regrettably, this measurement technique experiences limitations in not only the transonic range, but also in the high frequency range. Calibrated numerical tools offer an alternative procedure in the design of suitable instrumentation for turbine applications. First, two different probe geometries, oval and trapezoidal shapes, were characterized at different incidence angles. In particular, the pressure recovery, angle sensitivity, induced vortex shedding unsteadiness at several yaw angles were evaluated. The studies were performed over a wide range of Mach numbers from subsonic to the transonic regime. The vortex shedding of the probe was also carefully analyzed. In a second evaluation, we selected the oval probe geometry including the line-cavity effects into the pressure tappings. The resonance frequency of line-cavity system was evaluated and compared with analytical calculations, as well as with the detailed analysis of Bergh and Tijdeman. The comparison of the pressure tapping readings with the actual input signal allowed the identification of the transfer functions, as well as the physical mechanisms that should be corrected during the measurements. Finally, 3D unsteady evaluations were implemented to compute the blockage effects, as well as the final frequency attenuation experienced by the piezo-resistive sensors. All numerical analyses were performed using unsteady Reynolds Averaged Navier Stokes (URANS) models.
TOPICS: Design, Probes, Turbines, Pressure, Cavities, Vortex shedding, Resonance, Geometry, Shapes, Signals, Turbomachinery, Yaw, Mach number, Sensors, Transfer functions, Gas turbines, Instrumentation, Numerical analysis
Anindya Ghoshal, Muthuvel Murugan, Michael Walock, Andy Nieto, Blake Barnett, Marc Pepi, Jeffrey/J Swab, Dongming Zhu, Kevin Kerner, Christopher Rowe, Chi-Yu (Michael) Shiao, David Hopkins and George A. Gazonas
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037599
Commercial/Military fixed-wing aircraft and rotorcraft engines often have to operate in significantly degraded environments consisting of sand, salt, dust, ash and other particulates. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, and plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. This research represents the complex thermo-chemo-mechanical fluid structure interaction problem of semi-molten particulate impingement and infiltration onto ceramic thermal barrier coatings into its canonical forms. This is to understand the underpinning interface science of interspersed graded ceramic/metal and ceramic/ceramic composites at the grain structure level for robust coatings and bulk material components for vehicle propulsion systems. This project creates a framework to enable the engineered design of solid-solid and liquid-solid interfaces in dissimilar functionalized materials to establish a paradigm shift toward science from the traditional empiricism in engineering thermal barrier coatings and high temperature highly loaded bulk materials. An integrated approach of modeling and simulation, characterization, fabrication, and validation to solve the fundamental questions of interface mechanisms which affect the properties of novel materials will be validated to guide component material solutions to visionary 2040+ military vehicle propulsion systems.
TOPICS: Particulate matter, Gas turbines, Thermal barrier coatings, Ceramics, Propulsion systems, Aircraft, Sands, Coatings, Bulk solids, Engines, Manufacturing, Dust, Ceramic composites, Simulation, Turbine blades, Wear, Cooling, Fluids, Metals, Underpinning, Design, Durability, Modeling, Blades, Military systems, Military vehicles, oxidation, Wings, Fluid structure interaction, High temperature, Damage, Vehicles
Olivier E. Mathieu, Clayton Mulvihill, Eric Petersen, Yingjia Zhang and Henry Curran
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037602
Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH4 /10% C2H6 diluted in 99% Ar was studied at fuel lean (equiv. ratio = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H2O were recorded between 1400 and 1800 K. Water is a final product from combustion, and its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules were compared to a state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H2O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the CO profiles typically increase rapidly after an induction time, reach a maximum and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated for pressures above 1 atm.
TOPICS: Chemical kinetics, Shock (Mechanics), Methane, Water, Combustion, Lasers, Fuels, Absorption, Carbon, Gas turbines, Natural gas, Flames, Pollution, Ignition delay, Electromagnetic induction
Min Zhang, Jimmy McLean and Dara Childs
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037607
The abstract has more than 250 words. Please see it in the attachment.
Eli Yakirevich, Ron Miezner, Boris Leizeronok and Beni Cukurel
J. Eng. Gas Turbines Power   doi: 10.1115/1.4037611
The present work summarizes the design process of a new continuous closed-loop hot transonic linear cascade. The facility features fully modular design which is intended to serve as a test bench for axial micro-turbomachinery components in independently varying Mach and Reynolds numbers ranges of 0 - 1.3 and 2·10E4 - 6·10E5 respectively. Moreover, for preserving heat transfer characteristics of the hot gas section, the gas to solid temperature ratio (up to 2) is retained. This operational environment has not been sufficiently addressed in prior art, although it is critical for the future development of ultra-efficient high power or thrust devices. In order to alleviate the dimension specific challenges associated with micro-turbomachinery, the facility is designed in a highly versatile manner, and can easily accommodate different geometric configurations (pitch, ±20° stagger angle, ±20° incidence angle), absent of any alterations to the test section. Owing to the quick swap design, the vane geometry can be easily replaced without manufacturing or re-assembly of other components. Flow periodicity is achieved by the inlet boundary layer suction and independently adjustable tailboard mechanisms. Enabling test-aided design capability for micro gas turbine manufacturers, aero-thermal performance of various advanced geometries can be assessed in engine relevant environments.

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