bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Experimental and Numerical Investigation of the Aerodynamic Characteristics of a Flameless Combustor
Authors: Huijts M. P. , A. V. Perpignan A. , G. Rao A. 
Published: November 2019

Abstract
The flameless combustion (FC) regime is a promising technology for gas turbines, as it potentially yields lower NOx emissions while maintaining high combustion efficiencies. However, the application of FC to gas turbines is still challenging as required conditions for its occurrence depend on several factors such as reactants mixing, residence times, heat losses, and chemical time-scales. Since the mixing of the reactants and incoming fresh air-fuel mixture plays an important role in FC, the aerodynamic characteristics of the combustor are instrumental in determining the combustor emission performance. Focusing on the aerodynamic characteristics, this paper is dedicated to the visualization and description of the flow inside a jet-based combustor designed to operate under FC. The cylindrical combustor has a FLOX® burner head with 12 concentrically placed nozzles, while an acrylic cylinder allowed full optical access to the flow field. The investigation was performed for non-reactive flow. Using Particle Image Velocimetry and a Reynolds-averaged Navier-Stokes CFD analysis, the flow was visualized and modelled. The simulations were run with the Standard and Realizable k-ε (SKE and RKE, respectively), as well as a Reynolds Stress turbulence model. The effect of modifying the SKE model C1ε constant was also investigated. In the experimental campaign, the influence of combustion chamber length, nozzle diameter, and jet velocity were investigated with respect to flow structure, recirculation ratios and entrainment behavior.
The results show that the flow structure is mainly dependent on nozzle diameters, while the jet momentum is the correct parameter to assess the recirculation impact of a certain jet flow. The numerical investigation shows that the turbulence intensity at the boundaries is an important parameter to accurately simulate the jet spreading. None of the used turbulence models fully represented the flow field. Nonetheless, the SKE model with model C1ε = 1.44 was the best at representing the jets penetration and vortex core positions, and the recirculation ratio values predicted by it were in good agreement.
Corner Stall Prediction in a Compressor Linear Cascade Using Very Large Eddy Simulation (VLES) Lattice-Boltzmann Method
Authors: Maros Antoine , Bonnal Benoît , Gonzalez-Martino Ignacio , Kopriva James , Polidoro Francesco 
Published: November 2019

Abstract
Compressor corner stall is a phenomenon difficult to predict with numerical tools but essential to the design of axial compressors. Predictive methods are beneficial early in the design process to understand design and off-design limitations. Prior numerical work using Navier-Stokes computational methods have assessed the prediction capability for corner stall. Reynolds Averaged Navier-Stokes (RANS) simulations using several turbulence models [1] have shown to over-predict the region of corner hub stall where Large Eddy Simulations (LES) and Detached Eddy Simulations (DES) approaches improved the airfoil surface and wake pressure loss prediction [2, 3].
A linear compressor cascade designed and tested at Ecole Centrale de Lyon [3,4] provides a good benchmark for the evaluation of the accuracy of numerical methods for corner stall. This paper presents results obtained with Lattice-Boltzmann Method (LBM) coupled with Very Large-Eddy Simulations (VLES) approach of PowerFLOW and compares them with the experimental and numerical work from Ecole Centrale de Lyon. The ability to achieve equivalent accuracy at a lower computational cost compared to LES scale resolving methods can enable multi-stage design and off-design compressor predictions.
A methodical approach is taken by first accurately simulating the upstream flow conditions. Geometric trips are modeled upstream on the endwalls to match both the mean and fluctuating inflow boundary layer conditions. These conditions were then applied to the simulation of the linear compressor cascade. The benchline experimental study includes trips on both the pressure and suction of the airfoil. These trips are also included for the current simulation. The significance of capturing both inflow conditions and including trips on the airfoil are assessed. Detailed comparisons are then made to airfoil loading and downstream losses between experiment and previous RANS and LES simulations. LBM-VLES corner stall results of pitchwise averaged total pressure match LES agreement relative to experimental data at 50 times lower computational cost.
Phase-Opposition Control of the Precessing Vortex Core in Turbulent Swirl Flames for Investigation of Mixing and Flame Stability
Authors: Lückoff Finn , Sieber Moritz , Paschereit Christian Oliver , Oberleithner Kilian 
Published: November 2019

Abstract
The precessing vortex core is a helically-shaped coherent flow structure that occurs in reacting and non-reacting swirling flows undergoing vortex breakdown. In swirl-stabilized combustors, this flow structure affects important phenomena, such as turbulent mixing and thermoacoustic oscillations. In this work, a flow control system is developed to achieve appropriate conditions to systematically investigate the influence of the PVC on turbulent flames. The control consists of a zero-net-mass-flux actuator placed in the mixing section of the combustor, where the PVC is most receptive to periodic forcing. The actuator is driven in a closed loop to achieve phase-opposition control of the PVC. The flow control system is characterized from pressure measurements and particle image velocimetry and the impact on flame dynamics is extracted from OH*-chemiluminescence measurements. The data reveal that the PVC amplitude is considerably suppressed by the phase-opposition control without changing the overall characteristics of flow and flame. This is a very important requirement to study the exclusive effect of the PVC on combustion processes. Moreover, the control allows the PVC amplitude to be adjusted gradually to investigate the PVC impact on turbulent mixing and flame dynamics. It is revealed that the PVC-induced flow fluctuations mainly affect the large-scale mixing, while the small scale mixing remains unchanged. This is because the suppression of the PVC allows other modes to become more dominant and the overall turbulent kinetic energy budget remains unchanged. The destabilization of other modes, such as the axisymmetric mode, may have some implications on thermoacoustic instability.
Solar Desalination Based on Micro Gas Turbines Driven by Parabolic Dish Collectors
Authors: Sánchez David , Rollán Miguel , García-Rodríguez Lourdes , Martínez G. S. 
Published: November 2019

Abstract
This paper presents the preliminary design and techno-economic assessment of an innovative solar system for the simultaneous production of water and electricity at small scale, based on the combination of a solar micro gas turbine and a bottoming desalination unit. The proposed layout is such that the former system converts solar energy into electricity and rejects heat that can be used to drive a thermal desalination plant.
A design model is developed in order to select the main design parameters for two different desalination technologies, phase change and membrane desalination, in order to better exploit the available electricity and waste heat from the turbine. In addition to the usual design parameters of the mGT, the impact of the size of the collector is also assessed and, for the desalination technologies, a tailored multi-effect distillation unit is analysed through the selection of the corresponding design parameters. A reverse osmosis desalination system is also designed in parallel, based on commercial software currently used by the water industry.
The results show that the electricity produced by the solar micro gas turbine can be used to drive a Reverse Osmosis system effectively whereas the exhaust gases could drive a distillation unit. This would decrease the stack temperature of the plant, increasing the overall energy efficiency of the system. Nevertheless, the better thermodynamic performance of this fully integrated system does not translate into a more economical production of water. Indeed, the cost of water turns out lower when coupling the solar microturbine and Reverse Osmosis units only (between 3 and 3.5 €/m3), whilst making further use the available waste heat in a Multi Effect Distillation system rises the cost of water by 15%.
Transient Loading on Turbomachinery Packages due to Pressure Waves Caused by Accidental Deflagration Events
Authors: Gauch Hannes L. , Bisio Valentina , Rossin Stefano , Montomoli Francesco , Tagarielli Vito L. 
Published: November 2019

Abstract
In this study we present the application of numerical and analytical models to predict the transient loading of structures by impinging pressure and shock waves in air, which have been recently developed by the authors. Non-dimensional design maps are provided which yield predictions of the maximum loads on structures as a function of the problem parameters. Practical example applications, with reference to typical structures used in turbomachinery packages, are presented. These examples demonstrate the superiority of the new modelling techniques to current industrial design guidelines which are mostly extrapolated from simplified methods developed for shock waves. Finally, conclusions are drawn regarding the nature of the loading exerted on the structure in different regimes of problem parameters.
Evaluation of the Optimum Hybrid Power to Heat Configuration for a Gas Turbine Based Industrial Combined Heat and Power Plant
Authors: Klein Sikke , van Deursen Femke 
Published: November 2019

Abstract
Combined heat and power (CHP) is a very efficient way to generate both power and heat. However due to the increase in renewable power, the position of CHP in the energy system shifts: 1) the benefits of low effective CO2 emissions and low primary fuel consumption decrease and 2) the income from the generated power will show stronger fluctuations and will generally decrease.
Most CHP plants have shifted from base load operation to flexible operation on the power market to cope with these challenges. But due to the requirement for stable heat supply, flexible operation is more challenging than for a CCGT plant.
Significant flexibilization of CHP plants can be achieved by the integration with power to heat (P2H): the heat supply requirement enables the opportunity to create value out of low electricity prices during periods of excess renewable power generation using hybrid CHP-P2H-operation while during hours with high electricity prices and relatively low renewable power generation the CHP plant can run economically in its original configuration.
In this paper a study is executed on the implementation of P2H in an industrial CHP plant for four different configurations, varying from a ‘simple’ external electrical boiler to a full integration using air preheating and flue gas heating. The added flexibility and reduction of fuel consumption of these configurations have been calculated.
The economic analysis identified the imbalance market as the most attractive option for a hybrid CHP-P2H installation. The maximum income is generated by the CHP-P2H configuration that combines an inlet air preheater with electrical duct firing.
P2H appears to be a technical feasible option to make existing CHP installations fit for operation on a power market with an increasing share of renewable power.
Impact of Flame Lifting on Nitrogen Oxide Emissions From Premixed Reacting Jets in a Vitiated Crossflow
Authors: Sirignano M. D. , Nair V. , Sunkara D. , Emerson B. L. , Seitzman J. , Lieuwen T. C. 
Published: November 2019

Abstract
This paper describes measurements of nitrogen oxide (NOx) emissions from reacting jets in crossflow (RJICF). Primary factors that influence RJICF NOx emissions are: jet stoichiometry, mixing between jet and crossflow before combustion, and mixing of the remainder of the crossflow with the combustion products of the secondary combustion region. The aforementioned mixing is controlled by shear layer vortices and the counter-rotating vortex pair, as well as flame lifting. The coupled effects of bulk averaged temperature rise as a result of the RJICF (ΔT), jet stoichiometry (ϕJet), and momentum flux ratio (J) present a challenge in understanding critical factors controlling NOx production as it is difficult to vary them independently. Therefore, significant attention was paid to designing a test matrix that differentiated these effects. The data reported herein were obtained from the injection of premixed ethane/air or ethane/methane/air mixtures into a vitiated crossflow at one of two temperatures (1350K and 1410K). Varying the ethane/methane ratio allowed for systematic variation of flame lifting independent of ϕjet and J. The jets contained sufficient fuel to create an adiabatic bulk temperature rises from 75K–350K, with J values from 8–40, and ϕJet values from 0.8–8.0. The reported measurements confirm that NOx emissions increase monotonically with ΔT, as discussed in literature, but also indicates that the lifting of the flame significantly impacts NOx production. Lifting itself is a function of the variables described above and was quantified with chemiluminescence imaging. In fact, flame lifting is the dominant factor influencing NOx emissions, including ΔT.
Effect of Surface Roughness Induced by Laser Powder Bed Fusion Additive Manufacturing in a Mini-Channel Heat Exchanger
Authors: Parent-Simard T. , Landry-Blais A. , Dubois P. K. , Picard M. , Brailovski V. 
Published: November 2019

Abstract
The Inside-Out Ceramic Turbine (ICT) is a promising microturbine for aeronautics applications. To increase the cycle efficiency and reduce fuel consumption, microturbines must operate under the recuperated Brayton cycle. The addition of a heat exchanger (HEx) increases the weight of the engine and cancels out any fuel savings as compared to a non-recuperated turbine. For this reason, the requirements applied to HEx for aeronautic gas turbines are: low weight and volume, high effectiveness with a low pressure drop, capabilities to endure high pressure and temperature, and low cost. The Laser powder bed fusion (LPBF) opens a new design space for geometries that cannot be realized by conventional methods, but induces high surface roughness. This paper presents experimental and analytical studies of the influence of surface roughness on the performances of a 3D-printed, counterflow, mini-channel HEx, with 1% of the total mass flow rate of the ICT. Results showed that the friction and heat transfer are both increased in the the regime typically defined as laminar compared to the analytical results. The experimental results are in agreement with a 1D heat transfer model when using correlations for high-roughness values from the literature. LPBF is a promising method to manufacture gas turbine parts, but it is crucial to model and incorporate its manufacturing capacities in terms of precision and surface finish to enhance HEx heat transfer and potentially reduce mass.
Untwist Creep Analysis of Gas Turbine First Stage Blade
Authors: Jarrett Anthony , Erukulla Veda V. , Koul Ashok K. 
Published: November 2019

Abstract
During operation, turbine blades subjected to high temperatures will experience permanent geometric distortion due to creep. The principal form of this distortion is blade elongation due to the centrifugal load, but the blade can also straighten or ‘untwist’. The magnitude of the untwist can be used to track the accumulated creep strain damage in a blade, and so measurements of blade untwist over time are often recorded. If the relationship between untwist and creep strain damage can be expressed, then it will be possible to make more informed maintenance decisions.
This study describes a finite element creep analysis of a first stage turbine blade using a calibrated creep material model, and compares the calculated untwist to records kept by the operator.
The creep model used in this study is a physics based model using the microstructural properties of the blade alloy, and is calibrated using a single creep test at representative stress and temperature. An important objective of this study is to demonstrate that application of the creep model in a component with non-uniform stress and temperature will lead to representative results.
The analysis was repeated with two materials that correspond to different blade versions. The material with superior high temperature properties exhibited less untwist, and the analysis of both variants were comparable to the recorded blade measurements.
Impact of Dust Feed on Capture Efficiency and Deposition Patterns in a Double-Walled Liner
Authors: Cory Trevor M. , Thole Karen A. , Kirsch Kathryn L. , Lundgreen Ryan , Prenter Robin , Kramer Stephen 
Published: November 2019

Abstract
The introduction of particulates into gas turbine engines poses a serious threat to component durability. Particles drawn from the environment, such as ash or sand, can be introduced into the air system used to cool hot section components and drastically diminish cooling performance. In the current study, a dirt-laden coolant stream impinged on a double-walled cooling configuration, which was comprised of an impingement plate followed by an effusion-cooled plate. Experiments were conducted at both room temperature and at temperatures in excess of 750°C; flow conditions were varied to achieve different pressure ratios across the cooling configuration. Dirt particles were introduced into the coolant using two different methods: in discrete bursts, called slugs; or in a continuous feed ensuring a constant stream of particles. This continuous feed mechanism is at the crux of a new test facility created to introduce flexibility and precision in the control of dirt feed rates, particularly for very small (< 50 mg) amounts of dirt.
The difference in capture efficiency and in dirt patterns between the two feed methods showed measurably different dirt accumulation levels on the cold side of the effusion plate at the same test conditions. Results show that the slug feed method caused higher capture efficiency and thicker dirt deposition on the effusion plate compared to the continuous feed.
CMC Mode II Crack Growth Resistance Prediction of ASTM Specimen and Test Validation
Authors: Abdi Frank , Godines Cody , Presby Michael J. , Eftekharian Amir , Ahmad Jalees , Choi Sung , Morscher Gregory N. , Gonczy Steve , Shi Jun 
Published: November 2019

Abstract
The objective of this effort is to predict ceramic matrix composites (CMC) interlaminar Mode II Crack Growth Resistance (CGR), and the design of ASTM test specimen. Currently, there are a number of test standards and American Society for Testing and Materials (ASTM) for CMC’s at both ambient and elevated temperatures; however, there are no standardized test methods for determination of interlaminar shear (Mode II) fracture toughness in CMC’s. Although research work exists on interlaminar Mode II fracture toughness of CMC’s, the test methods applied showed definite drawbacks and limitations. Delamination Crack Growth (CGR) tests of CMC Mode II may exhibit zig-zag pattern, wavy cracks, fiber bridging, and premature specimen failure under bending load. The experimental parameters that may contribute to the difficulty can be summarized as specimen width and thickness, interface coating thickness, mixed mode failure evolution, and interlaminar defects. Modes II crack growth resistances, GII, were analytically and numerically determined at ambient temperature using end notched flexure (ENF) and the end-loaded split (ELS). Finite Element (FE) based. Multi-scale progressive failure analysis (MS-PFA) a combined Micro-mechanical damage and fracture mechanics Virtual Crack Closure Technique (VCCT) algorithms. Modeling of melt-infiltrated SiC/SiC CMC of ENF specimen (Laminate: with initial crack length was accomplished using a MS-PFA and VCCT approach. Test data were compared with MS-PFA prediction: a) Force vs. Crack Opening Displacement; and b) Mode II crack tip energy release rate vs. crack extension length for both edge and center line due to formation of Micro Crack Density Contribution, Crack Tip Stiffness Reduction; and c) zig-zag crack growth behavior (adhesive/cohesive). Next the ASTM Standard Proposed linear SGR equation was developed based on interpretation compliance technique from both MS-PFA Analysis and Test.
Influence of Blade Flexibility on the Dynamic Response Simulation of a Turbomolecular Pump on Magnetic Bearings
Authors: Barbosa Moreira Alysson Bruno , Thouverez Fabrice 
Published: November 2019

Abstract
This paper proposes the simulation of a complete mechanical model of a turbomolecular pump rotor, including rotor and blades flexibility, suspended by controlled active magnetic bearings. The mechanical model is composed of an eight stage blisk, attached to a shaft. Magnetic forces are linearized by first order Taylor expansion around a given point. Including blades and rotor flexibility makes the mechanical system asymmetric, so the equations of motion for the coupled system have periodic terms. A modal controller was designed to control rigid body modes, since the number of sensors is limited and no state observer is implemented. PID controllers are used for low frequency modes combined with second order filters to damp high frequency modes. First of all, stability analysis was carried out for the axisymmetric case. Secondly, blades flexibility was included. Forced response of the whole system to an impulsive force was studied. Divergent responses for the system in rotation were obtained as a second order filter pole possibly interacts with blades modes. Taking second order filters off the control loop allowed the system to be stable. These results show that the analysis method developed here is efficient to evaluate the performance of a controller in closed loop with the complete flexible system. This method may be used in industrial design processes as computation times for the complete system are very short.