bluuebunny/crossref_metadata_2025 huggingface dataset:
Film Cooling and Cold Streaks Tracking on a Fully Cooled Nozzle Guide Vane Under Representative Combustor Outflow Conditions
Authors: Babazzi Giulia , Bacci Tommaso , Picchi Alessio , Facchini Bruno , Cubeda Simone
Published: October 2022

The pronounced non uniform temperature distribution in the core engine flow path is a recurring problem of gas turbine engine design process. Specifically, turbine entry conditions are usually characterised by severe temperature distortions, often referred to as hot and cold streaks, ascribed to combustor burners and combustor liners cooling systems. Temperature distortions remain an issue even at the exit section of the nozzle guide vane (NGV), where additional cold streaks coming from the vane film cooling system are injected into the flow. A precise knowledge of thermal field and its evolution is thus essential to mitigate their impact on turbine performance and lifetime. Various studies focus on the description of streaks migration through a direct investigation of the thermal field, providing an effective evaluation of the global phenomenon. As a deeper understanding is often required, experimental techniques based on the detection of tracer gases can be successfully adopted.

In this study, a realistic combustor outlet swirl profile was imposed on a fully cooled NGV cascade to analyse both film-cooling behaviour and cold streaks migration and redirection. A concentration probe based on the fluorescence behaviour of an oxygen sensor, fully characterised in a previous work, was here employed to track the position of the film cooling flows at the NGV cascade exit plane, while the adiabatic film-cooling effectiveness was evaluated on the NGV surfaces employing the Pressure Sensitive Paint (PSP) technique. Overall, the swirling structure strongly affect both the film-cooling behaviour and cold streaks migration through and downstream the vane. The importance of examining the unsteady aspect is also highlighted to better estimate actual components operating temperatures. A global understanding of the occurring phenomena is therefore provided, as well as significant pieces of information that can be extremely useful for the design phases of both the NGV and the following rotor cascade.
Full Rejuvenation Heat Treatment of GTD 111DS
Authors: van Esch Hans , Pietersen Stijn , Greaves Wayne , Bridges Alex , Scheibel John
Published: October 2022

Previous studies performed by TEServices, Sulzer and EPRI showed that GTD111 DS metallurgical and mechanical [stress rupture (SR) and low cycle fatigue (LCF)] properties can be restored close to new with and without hot isostatic pressing (HIP) followed by full solution heat treatment (FSHT). Based on this success, a full rejuvenation heat treatment (FRHT) was developed that can obtain GTD 111DS metallurgical condition and mechanical properties which are better than new.

This paper will show the metallurgical condition differences between new material, partial solution heat treatment (PSHT), FRHT and the related mechanical (SR and LCF) properties. A mechanical test was developed that varied exposure of FSHT and FRHT specimens between stress (SR) and fatigue (LCF) which is especially important for high starts and relatively low hour gas turbine operation.

This study proved that the FRHT provides superior metallurgical and mechanical properties when compared to FSHT and new GTD 111DS.
Numerical Study of Flow Characteristics of a Central-Staged Swirl Combustor
Authors: Feng Xiangzhou , Suo Jianqin , Zhu Pengfei , Li Yue , Li Qiandong
Published: October 2022

The two-combustion-zone design approach is adopted in order to achieve good idle LBO in a central-staged swirl combustor. The flow characteristics of the combustor are investigated through large eddy simulation (LES). The numerical method is validated by comparing the numerical results of time-average velocity profiles with PIV results at various axial locations. The grid scale is analyzed through Pope’s criterion to guarantee that most turbulent kinetic energy can be resolved by the present mesh. The coherent structures are isolated from turbulence flow by proper orthogonal decomposition (POD) method. Multiple monitor probs are set up in swirling flow and shear layers. The fast Fourier transform (FFT) is used to obtain frequency characteristic of time-domain signal. The difference between time-average velocity field and instantaneous velocity field is first explained. The recirculation zones are sorted by the locations and formation mechanism. The precessing vortex core (PVC) is found to be the crucial coherent structure of central-staged combustor. The spatial structure and temporal evolution of PVC are captured. Both single-helix and double-helix modes are discovered through POD method. By using phase-averaged method, the interaction between PVC and axial velocity field is investigated.
An Experimental Test Case for Transonic Low-Pressure Turbines – Part I: Rig Design, Instrumentation and Experimental Methodology
Authors: Simonassi Loris , Lopes Gustavo , Gendebien Samuel , Torre Antonino Federico Maria , Patinios Marios , Lavagnoli Sergio , Zeller Nicolas , Pintat Ludovic
Published: October 2022

The ultra-high bypass ratio geared turbofan is a key concept to reduce the environmental impact of the next generation aircrafts. The increase in rotational speed of the low-pressure turbine (LPT) enabled by the geared architecture offers potential benefits in efficiency and considerable savings in engine weight, overall dimension, and cost. High-speed LPTs operate at transonic exit Mach numbers and low Reynolds numbers. For this combination of operating conditions, where compressibility influences the blade aerodynamics and loss mechanisms, there is a critical lack of openly available detailed experimental data concerning the combined effects of unsteady wakes, purge streams, leakages, and secondary flows for CFD models validation.

The current research project focuses on the full characterization of an experimental test case concerning the impact of unsteady wakes and purge flows on the blade aerodynamics and loss mechanisms in a high-speed LPT cascade tested at engine-scaled conditions. The extensive experimental dataset is collected in an open-access database, providing novel validation material for comparison with numerical computations.

In this two-part paper, a comprehensive study on the design, commissioning and testing of a transonic low-pressure turbine blade at on and off-design is presented. Part I describes the design of components and accurate instrumentation required to investigate steady quasi-3D flows in a linear cascade environment at low-Reynolds and transonic exit Mach numbers. A novel concept to perform blade radial traverses to obtain spanwise distributions of high-resolution blade measurements is presented. The repeatability and periodicity of the rig flow conditions are demonstrated. This work critically evaluates the methodology used for the design and adaptation of the existing rig for testing of unsteady three-dimensional flows in linear cascade experiments.
Gas Turbine Transition Duct Gap Assessment for Unsymmetrical Thermal Boundary Conditions
Authors: Sambandam Manoharan , Colantoni Simone
Published: October 2022

The transition duct (TD) in a gas turbine (GT) twin shaft variant provides an aerodynamic coupling between its high-pressure gas generator module and low-pressure power module. Since the TD defines the flow passage, it interfaces with the high-pressure rotor and shroud at the forward end and the low-pressure rotor and stator at the aft end. Normally, the GT twin shaft variant is equipped with part-load capability. To fulfill this need and to comply with the emission norms, only desired number of burners, adjacent to each other, are used to burn fuel. Using some of the burners during the GT operation is referred to as staging. The GT operation under staging conditions result in non-uniform temperature distribution in the angular locations at any axial position and thus non-uniform thermal growth in the radial and axial directions. This non-uniform thermal growth in radial and axial direction leads to the interface definition very challenging. During the staging operation, the rotor parts experiences uniform radial and axial growth at all the angular locations. Whereas the interfacing stator parts experience temperature distribution like that of the TD and results in non-uniform thermal growth in the radial and axial directions. Appropriate interface definition is vital for efficient operation of the GT. Any interference condition of the TD with rotating parts result in rubbing and with stationary parts result in thermal binding, impacting the GT normal operation. Any generous gap adversely impacts the GT performance due to consumption of more cooling medium. Thus, an assembly gap which results in no interference and consumption of less cooling medium throughout the staging operation is considered as optimum assembly gap. Thorough gapping assessment is performed considering all the transient time points to ensure that the gap values are set optimally. This paper is intended to describe the steps followed in assessing the anticipated interference and gap situations at various interfaces.
Particle Deposition on HPT Nozzle: Full 3D Investigation and Secondary Flows Effect
Authors: Casari Nicola , Oliani Stefano , Pinelli Michele , Suman Alessio , Carnevale Mauro
Published: October 2022

Gas turbines can operate in an environment dispersed with particles that, if ingested by the machine, may have a detrimental effect on the aerodynamic performances. Therefore, the aim of this work is to gather information about how particles adhesion is influenced by geometrical features of gradually growing complexity. At this scope, the particle deposition problem is investigated from the numerical standpoint. Specifically, the LS-89 transonic high pressure turbine (HPT) vane is simulated and an encounter with a volcanic ash cloud is modelled. Three simulations are carried out: a 2D simulation has been compared with the set of 3D simulations. Different levels of complexity of the geometry have been considered for the 3D case: the endwall effect has been assessed considering the presence of a variable radius fillet and comparing it with the prediction obtained by a cylindrical extrusion. The proposed analysis provides indications on the 2D and 3D prediction with regards to particle deposition problems. The sticking pattern of the particle has been investigated in relation to the different nature of secondary flows.
Design and CFD Study of an ORC Radial Turbine for Multiple Working Fluids
Authors: Djaname Tchable-Nan , Deligant Michael , Bakir Farid , Marinelli Marzia , Capurso Tommaso , Torresi Marco
Published: October 2022

Organic Rankine cycle is an available solution for the conversion of low-grade thermal energy into electricity. In this way, it contributes to enhance the global plant efficiency hence to the reduction of the power plant carbon footprint (CO2 production). However, contrary to water Rankine cycle or Brayton cycle, in ORC the working fluid may change depending on the characteristics of hot and cold sources. Expander cost is estimated to be around half of the total cost of an organic Rankine cycle installation. Hence, developing a given turbine for multiple applications will help reducing the cost of ORC systems. In this work a radial turbine will be numerically investigated. The design and performance analysis of such a turbine will be analyzed for three working fluids taking into account real gas effect under expansion. An iterative process using preliminary design combined with meanline analysis allows the selection of the final geometry. Finally, 3D CFD simulations are computed on the obtained geometry with the selected working fluids for different operating conditions. Small deviations can be observed between the 3D CFD results and the prediction code. The different fluids have been selected based on safety (ASHRAE A1 and A2), environmental (GWP less than 150, ODP near to 0) and thermodynamic properties criteria (dry or isentropic fluid). The operating conditions have been selected to start the expansion in the low compressibility zone and featuring high rotational speed (up to 60000 rpm), low power (up to 9kW) and high maximum efficiency.
The Effect of an Entirely Eroded Airfoil on the Aerodynamic Performance of a Supersonic Compressor Cascade
Authors: Hartmann Jan , Lorenz Max , Klein Markus , Staudacher Stephan
Published: October 2022

In-service performance of modern axial compressors of aircraft engines is strongly dependent on deterioration processes such as solid particle erosion. So far the resulting aerodynamic losses have been studied by analyzing pre-set shape changes of locally eroded airfoil regions with a focus on the leading edge contours. However, the aerodynamic losses caused by solid particle erosion are the result of the entire shape change of the deteriorated airfoils. These shapes are assignable to the particular erosive conditions and the amount of particles ingested. The midspan airfoil shapes of the NASA Rotor 37 experimentally deteriorated in a linear cascade form the basis of the presented numerical study. The shapes of the eroded airfoils are used to perform supersonic numerical simulations at near stall conditions. The losses and flow patterns caused by different degrees of erosion are discussed. Cascade performance is deteriorated up to 25% due to solid particle erosion. The shock systems for different erosion shapes are evaluated and their influence on the overall losses is demonstrated. It is concluded that the analysis of isolated erosion phenomena such as leading edge changes in shape provide an incomplete understanding of the aerodynamic losses caused by solid particle erosion. The interaction of the entire shape change of the airfoils is needed to fully understand the losses in turbomachines caused by erosion.
Processing Multi Component Blade Tip Timing Experimental Data by Independent Component Analysis
Authors: Rizzetto Elena , Carassale Luigi
Published: October 2022

Blade Tip Timing (BTT) is a simple, robust and non-intrusive method for measuring the rotor blade vibrations in turbomachinery. The analysis of vibrations characterized by multiple spectral components typical for example of flutter is challenging. This paper proposes a probabilistic method based on the Independent Component Analysis able to separate and identify multiple harmonic components sampled according to a BTT-like schema. The data are divided into batches of fixed length called snapshots, which are interpreted as realization of random vectors. The statistical property of the subspace spanned by such random vectors is used to identify the number of components present in the signal (i.e. number of active modes), to separate the components and estimate their frequency and amplitude. These results are obtained by applying sequentially the Principal Component Analysis (PCA) and the Independent Component Analysis (ICA) and the Harmonic Matching (HM). The proposed technique is applied to experimental data obtained from a test rig with fixed disk and traveling load. The time-resolved measurements are resampled according to the sampling pattern induced by a specified sensor spacing.
Modeling of Inviscid Flow Shock Formation in a Wedge-Shaped Domain Using a Physics-Informed Neural Network-Based Partial Differential Equation Solver
Authors: Laubscher Ryno , Rousseau Pieter , Meyer Chris
Published: October 2022

Physics-informed neural networks (PINN) can potentially be applied to develop computationally efficient surrogate models, perform anomaly detection, and develop time-series forecasting models. However, predicting small-scale features such as the exact location of shocks and the associated rapid changes in fluid properties across it, have proven to be challenging when using standard PINN architectures, due to spatial biasing during network training. This paper investigates the ability of PINNs to capture these features of an oblique shock by applying Fourier feature network architectures. Four PINN architectures are applied namely a standard PINN architecture with the direct and indirect implementation of the ideal gas equation of state, as well as the direct implementation combined with a standard and modified Fourier feature transformation function. The case study is 2D steady-state compressible Euler flow over a 15° wedge at a Mach number of 5. The PINN predictions are compared to results generated using proven numerical CFD techniques. The results show that the indirect implementation of the equation of state is unable to enforce the prescribed boundary conditions. The application of the Fourier feature up-sampling to the low-dimensional spatial coordinates improves the ability of the PINN model to capture the small-scale features, with the standard implementation performing better than the modified version.
Low Order Heat & Mass Flow Network Modelling for Quasi-Transpiration Cooling Systems
Authors: van de Noort Michael , Murray Alexander V. , Ireland Peter T.
Published: October 2022

Quasi-transpiration cooling schemes such as Double-Wall Effusion Cooling allow the Nozzle Guide Vanes of High Pressure Turbines in modern aeroengines to experience high heat loads whilst maintaining acceptable temperatures. The combination of impingement, pin-fin and effusion cooling in such schemes produces a high convective cooling efficiency, but this is accompanied by large pressure losses that increase vulnerability to coolant migration toward low pressure regions. This can have severely detrimental effects on cooling performance as effusion holes around the Leading Edge can be starved of coolant, producing no local film cooling protection.

This paper presents a Low Order Model (LOM) which rapidly produces pressure, temperature, mass and heat flow distributions throughout Double-Wall Effusion Cooling Schemes, developed from a previously presented Mass Flow Network LOM. These can be found for a variety of flow and geometric conditions, allowing fast analysis of cooling designs. Experiments were conducted using a steady-state facility, from which results were used to validate the new LOM to a satisfactory standard. Using specifically derived dimensionless groups for coolant migration, results from the LOM demonstrate the effect of heat transfer on it as well as the effects of coolant migration on the cooling performance, highlighting design guidelines to reduce such effects and to optimise the component life.
Accurate and Efficient Computation of Heat Transfer Coefficient From CFD Simulations
Authors: Chaquet Jose M. , Perez Carlos , Quintanal Jaime
Published: October 2022

Prediction of thermal loads plays an important role in turbomachinery applications. Accurate results require solving multiphysics phenomena using techniques such as conjugate thermal methods. In this context, CFD solvers allow us to obtain heat fluxes at the wall interfaces with solid domains. An important quantity to properly understand the thermal problem is the heat transfer coefficient (HTC, also called film coefficient) which basically is the proportionality constant between the heat flux and the temperature difference between fluid and solid domains. Methods for computing HTCs have been reported in the literature relying on information at the domain interfaces level. In the present paper a new approach taking advantage of the whole fluid domain is described. This proposed method is efficient since only one CFD solution is required for each instant. Several numerical simulations are presented in order to prove that the computed HTC field is able to mimic the CFD solver while maintaining the same operation conditions. Also it is shown how these surrogate models have partial predictive capabilities to perform cheap simulations at different operation conditions. Comparison of experimental data with numerical results confirms the aforementioned performance of the proposed approach, obtaining similar results as methods incorporating only information at boundary walls.
Effect of Jet-to-Plate Temperature Ratio on Flow and Heat Transfer Features of Active Clearance Control Systems
Authors: Da Soghe Riccardo , Mazzei Lorenzo , Tarchi Lorenzo , Casini Niccolò , Castelli Niccolò , Cocchi Lorenzo , Picchi Alessio , Facchini Bruno , Rotenberg Maxime
Published: October 2022

The goal of the present work is to investigate the effects of target plate temperature on heat transfer features of representative active clearance control (ACC) geometries presenting 0.8 mm circular impingement holes arranged in a single row pattern. The jets generated by such holes cool a flat target surface, which is replicated by a metal plate in the experimental setup. A steady-state technique with controlled wall heat flux is used to measure averaged heat transfer values along the target plate. The target plate is composed by a series of insulated blocks to limit lateral conduction effects and also to assure a fine control of the supplied power. A full characterization of pipe, target plate and flow temperature is obtained using thermocouples and IR camera. Target plate temperature level ranges from 330 K to 570 K, while the manifold inlet temperature is kept at ambient level. The jet-to-target plate temperature ratio (TR) thus ranges from 1 to 2 circa. The investigated jet Reynolds numbers range from 4000 to 10000. The obtained results reveal that heat transfer features are affected by the target plate temperature level, as it plays a role on the interaction between the impingement jets, the spent flow and the manifold surfaces. An in-depth analysis of the obtained results provides valuable information about the extrapolation of ambient test results to engine conditions.
Unsteady Analysis of Aeroengine Intake Distortion Mechanisms: Vortex Dynamics in Crosswind Conditions
Authors: Rao Anirudh Narayan , Sureshkumar Prathiban , Stapelfeldt Sina , Lad Bharat , Lee Kuen-Bae , Puente Rico Ricardo
Published: October 2022

The formation of a ground vortex and its ingestion into an aero-engine intake under crosswind conditions play a significant role in the aerodynamic excitation of the fan. Using steady and unsteady numerical simulations, an analysis of the dynamics of several distortion features is presented. For a simplified intake at high crosswind velocities, there is a substantial movement of the ingested ground vortex at the aerodynamic interface plane (AIP). The ingested ground vortex follows a specific trajectory while varying both in size and strength. The transition from a periodic to an aperiodic regime of the intake distortion at the AIP occurs as the crosswind velocity is increased. Circumferential mode decomposition shows that the largest amplitude of the distortion occurs at the first circumferential mode, and the amplitudes of the higher modes decrease monotonically. Furthermore, the amplitude of the spatial harmonics is time-dependent, which may be an influential feature at the time of assessing fan forced response.
A Resistive Model to Characterize Overall Effectiveness Influenced by Multiple Coolant Temperatures
Authors: Rutledge James L. , Fuqua Matthew N. , Polanka Marc D. , Baker William P.
Published: October 2022

The surface temperature of a film cooled turbine hot gas path component is typically nondimensionalized according to the overall effectiveness. This nondimensionalization scheme takes advantage of the fact that the surface temperature must be bounded by the coolant temperature and the freestream recovery temperature. Additional complexity arises when the surface temperature is influenced by the addition of a second coolant stream. While the surface temperature remains bounded by the cooler of the two coolant streams, the presence of the warmer stream means that the resulting overall effectiveness is now a function not only of the appropriately nondimensionalized coolant and freestream flow rates, but an additional nondimensional parameter that describes the relative difference in the two coolant temperatures. Previously, it was thought that experiments or computational fluid dynamics simulations would be required to discern this effect. In the present work, however, we introduce a linear resistive model that is based upon the exact solution to the energy equation and which accounts for the effect of any number of independent sources that influence the surface temperature. The model’s efficacy was demonstrated using experimental data acquired on conducting models in which two rows of holes ejected coolant from two independent plenums at two different temperatures.
Effect of a Reduced Oil Flow Rate on the Static and Dynamic Performance of a Tilting Pad Journal Bearing Running in Both the Flooded and Evacuated Conditions
Authors: San Andrés Luis , Alcantar Andy
Published: October 2022

The mechanical efficiency of rotating machinery improves as drag power losses in bearings reduce; hence, an operation mode that reduces the supplied flow brings immediate benefits. The paper presents measurements of the static and dynamic load performance conducted with a tilting pad journal bearing configured as flooded and evacuated, and supplied with flow rates from 150% to ∼25% (or lesser) of a nominal magnitude, proportional to shaft speed. The lubricant is ISO VG 46 oil supplied at 60 °C. The four pads bearing has center pivots with single orifice feeds for the flooded condition and spray bar injection for the evacuated condition. The shaft, 102 mm in diameter, operates at two speeds, 6 and 12 krpm (= 64 m/s surface speed), while a static load is applied between pads (LBP). The specific loads equal 345, 1,034 and 2,068 kPa. A reduction in flow rate makes both bearings operate more eccentrically. The evacuated bearing operates at a larger eccentricity, which for the lowest flow rate does not align with the direction of the applied load, hence displaying a sizable attitude angle. Pad subsurface temperatures are similar for both bearing configurations, although the evacuated bearing is colder by a few degrees Celsius. Drag power losses derived from the oil exit temperatures show the evacuated bearing produces up to ∼40% lesser power loss than the flooded bearing for a nominal oil flow rate. The bearings direct stiffnesses, Kxx and Kyy, increase with applied load and show little dependency on shaft speed. The evacuated bearing has lower magnitude stiffnesses, 20% or so lesser, than the flooded bearing. Damping coefficients, Cxx ∼ Cyy, reduce in magnitude as the flowrate decreases. In particular for low flow rates, 35% or lower, the evacuated bearing shows rather small (though highly uncertain) damping coefficients. For sufficiently small flow rates, operation at 6 krpm shaft speed and under the smallest applied unit load (345 kPa) produced subsynchronous shaft vibrations with a broad band spectrum (SSV hash). The evacuated bearing produced SSV hash at flow rates equal to 30% or so of nominal, while the flooded bearing demanded very low flow rates (∼15% and lesser of nominal) to produce SSV hash. For both bearings, the SSV amplitude motions were rather small in amplitude. The experimental campaign demonstrates that tilting pad bearings (flooded and evacuated) can safely operate with a reduced flow rate (50% or so of nominal) to produce significant savings in drag power losses and without significant effect on the pads’ metal temperatures that could affect the bearing long-term operation.
Numerical Investigation of Unsteady Inlet Guide Vane-Rotor Interactions in a Transonic Fan Due to Boundary Layer Ingestion
Authors: Giri Ritangshu , Turner Mark G.
Published: October 2022

The effects of boundary layer ingested inlet distortion on the unsteady flowfield between an inlet guide vane (IGV) and rotor of a single stage transonic fan are important, as they result in significant changes in the massflow rate, stagnation pressure rise and stage efficiency. The three dimensional time accurate commercial URANS code EURANUS (Cadence Inc.) was used to generate and analyze periodic quarter annulus simulations of the IGV-Rotor fan stage. A comparison of mixing plane and time averaged solutions showed the unsteadiness of the blade row interactions especially along the interface between the IGV and the rotor. The mixing plane solution predicted a decrease in efficiency of 1.11 % in the fan stage compared to that of a rotor, while a time averaged solution predicted a 1.36 % efficiency decrease in the fan stage compared to that of the rotor. At design speed, significant non-linear interaction was observed with very high levels of unsteady loading occurring at the vane trailing edge region because of it’s interaction with the rotor generated oblique shock waves. These shock waves move upstream and get reflected through the vane passages creating additional fan stage loss. It can also be observed that the strong vortices of the inlet guide vane wake break up the detached rotor bow shock. These shed vortices are chopped by the rotor leading edge and ingested by the rotor. Both the time averaged and the time accurate results show that the wake vortices strongly interact with the rotor blade boundary layer. These cause a decrease in the rotor efficiency and stagnation pressure rise, while the high frequencies of the inlet guide vane wakes can be a potential cause of rotor high cycle fatigue (HCF). Additionally, small flow separations due to shock boundary layer interactions can be observed at the IGV suction surface near the tip and contribute to the IGV flow losses.
Experimental Study on the Combustion Performance of Concentric Staged Lean Direct Injection Combustor With Two Different Swirler Angles of the Pilot Stage
Authors: Zhu Pengfei , Suo Jianqin
Published: October 2022

With the civil aviation engine now developing towards lower pollutant, and the lean direct injection (LDI) combustion proves excellent potential in reducing NOx emission, a concentric staged LDI combustor, both the main and pilot stages are based on LDI combustion concept, is proposed in this paper. It has great potential for an aero engine for a more straightforward structure and smaller size than the Multi-Point Lean Direct Injection (MPLDI) low emission combustor. Experimental research on the combustion and emission characteristics of the concentric staged LDI single-tube combustor with two swirl angles of the pilot stage (Case A: 35°, Case B: 45°) was carried out. The ignition performance was carried out at atmospheric pressure while the total pressure drop was 0.01–0.06, and the combustion and emission characteristics were carried out at different inlet conditions, fuel-air ratios (FAR), and fuel ratios of the main stage. The results indicate that the lowest ignition FAR of both two cases presents the trend of first decreasing and then increasing with the pressure drop, and Case B is lower than Case A at all conditions. The lean blowout FAR of Case B is 0.008, which is reduced by 11.11% than Case A. At the low condition, the inlet temperature is 540K, the NOx emission of the exit presents the trend of increasing with the increase of the FAR while the pilot stage works only. At the condition of the inlet temperature with 653K, both the main and pilot stages work together, and the fuel ratio has a distinct effect on the NOx emission of the combustor. However, when the inlet temperature is 737K, the EINOx of the combustor is almost the same at different fuel ratios. It is identical for both Case A and B. At all conditions, the EINOx of case B is lower than case A, and it is the same for the combustion efficiency. Overall consideration, though the combustion efficiency of Case B is lower than Case A, it is still not less than 99.9% when the main and pilot stages work simultaneously, 90% when the pilot stage works only. All the ignition, lean blowout, and NOx emission performances of Case B are better than A. Case B is better than Case A for a civil aviation engine.
Serviced HGP Parts Assessment Using Microstructure-Based Models for New NovaLT™16 Gas Turbine Validation
Authors: Mastromatteo F. , Romanelli M. , Giovannetti I. , Cinelli C.
Published: October 2022

NovaLT™16 is a new high-efficiency gas turbine developed by Baker Hughes for mechanical drive and power generation applications in the 16MW market range.

The Fleet Leader engine of this GT class underwent a planned stop which has been used to check the status of the most critical components and validate the engine design.

Hot Gas Path (HGP) components specifically have been object of a detailed assessment of their post-service conditions which included NDT inspections, dimensional measurements, air and water flow checks of cooling circuits. Selected components have been also destructively examined to check their microstructure condition and assess the level of service-induced base material and coating alteration.

The set of assessments carried out did not highlight any criticality in the engine overall condition or unexpected behavior with respect to design intent.

For High Pressure (HP) buckets a quantitative assessment of the service temperature has been also obtained leveraging a microstructure-based model specifically developed by Baker Hughes for bucket base material René N4, a first-generation single crystal superalloy. This model takes into account the time-temperature dependent alterations of the γ/γ’ material structure and namely the growth of the periodicity width lambda (λ), measured along the [001] lattice direction of the single crystal structure.
A Review of High-Speed Rotating HP Turbine Heat Transfer and Cooling Studies Over the Last Decade in the Oxford Turbine Research Facility
Authors: Falsetti Chiara , Beard Paul F. , Cardwell David N. , Chana Kam S.
Published: October 2022

Over the last years, advanced experiments under engine-representative conditions have been performed in the Oxford Turbine Research Facility (OTRF) to obtain high-quality aero-thermal data that are essential for developing novel cooling designs and for validating computational models.

Thanks to its unique experimental capabilities, the OTRF plays a crucial role in the advancement of HP turbines, which are life limiting components of modern gas turbines due to the harsh high temperature environment.

The OTRF continues to be developed for additional capability to achieve more engine-representative conditions. Major upgrades include: (i) a combustor simulator able to produce engine radial and circumferential temperature profiles and inlet swirl simultaneously to study combustor-turbine interaction, (ii) fully film-cooled HP turbine designs and 1.5 stage configurations with a low-turning strut, (iii) novel rotor casing effusion cooling concepts, (iv) an advanced in-shaft data acquisition electronics system.

More recently, the enhanced capabilities of additive manufacturing have been used in the facility to investigate the performance of novel blade tips and full annular effusion cooling concepts. This allowed complex cooling features and geometries to be implemented and assessed in the facility. The aero-thermal performance of cooled and uncooled blades for three variants of squealer tip design and a next-generation effusion cooling designs have been recently evaluated.
Assessing the Structural Integrity of Plasma-Sprayed Multilayer Thermal Barrier Coatings
Authors: Adam Marcel , Kontermann Christian , Oechsner Matthias
Published: October 2022

The majority of lifetime models associates the failure of thermal barrier coatings to an oxidation of the bond coat. A thickening of the thermally grown oxide leads to a conversion of stresses at the undulated ceramic-metal interface, supporting the propagation of existing micro cracks. However, in plasma-sprayed multilayer thermal barrier coatings consisting of gadolinium zir-conate (GZO) and yttria-stabilized zirconia (YSZ) a shift of the failure site from the ceramic-metal interface to the GZO-YSZ interface has been observed. Thus, an exclusively oxide-based formulation is not sufficient to describe the damage transition phenomena. Therefore, this paper outlines a mechanism-based approach for assessing the structural integrity, considering all relevant thermally activated processes as well as the interaction between thermal and elastic misfits. Oxidation of bond coat, creep of composite materials and sintering of ceramics are modeled in terms of temperature and exposure time. Finite element analysis of GZO-YSZ pairings with different microstructures reveal a strong influence of the initial porosities on the sintering behavior and thus on the resulting mechanical stresses and potential crack driving forces at the bi-material interfaces.
A Novel Wake Control Approach for Power Generation Improvement of Three Wind Turbines in a Wind Farm
Authors: Erfanian Nakhchi Toosi Mahdi , Rahmati Mohammad
Published: October 2022

The total power generation of a wind farm is significantly affected by the adverse wake generation of upstream wind turbines on the aerodynamic performance of the downstream wind turbines. This paper aims to provide a novel hybrid wake control strategy to improve the power generation of horizontal-axis wind turbines in a wind-farm layout. A numerical simulation based on the actuator line method with large eddy simulation (ALM-LES) is performed to investigate the airflow around three-dimensional NREL 5MW turbines in a three-by-one layout. The yaw angle (θ) and tilt angle (ϕ) of the wind turbines are in the range of (−30° < θ < 30°) and (0 < ϕ < 35°), respectively. Firstly, the combined effects of yaw-control and tilt-control methods on the velocity profile, vorticity generation and turbulent kinetic energy in the wake region of the multiscale wind farm are investigated. Afterwards, the total power generation of the wind farm is compared with previous wake control methods of wind turbines. It was observed that the proposed hybrid wake control method could improve the total power generation by 9.94% compared to the previous wind turbine wake control techniques. The hybrid control strategy can deviate the wake much better than typical single-control methods. An optimization analysis is also provided to find the most appropriate yaw angles and tilt angles of the wind turbines subject to varying wind speeds.
Effect of Outlet Boundary Condition on the Acoustic Mode Shape and Flame Dynamics of a Partially Premixed Swirl Stabilised Combustor
Authors: Sreedeep Sharan , Ramanan Vikram , Chakraborty Aritra , Chakravarthy Satyanarayanan R.
Published: October 2022

Industrial gas turbines commonly use lean premixed swirl stabilised combustors that are prone to thermo-acoustic instabilities. Combustor testing involves several steps ranging from atmospheric to high-pressure conditions. An open outlet boundary condition is maintained for atmospheric tests commonly, whereas high-pressure testing involves complex exit boundary conditions, which changes the reflection coefficient and can affect the nature of instability. Current work aims at studying how the change in outlet boundary affects the nature of instability due to changes in the exit reflection coefficient and acoustic mode shape inside the combustor. A laboratory-scale industrial swirl burner that uses partially premixed methane and air at atmospheric conditions is analysed for this purpose. A constant area contraction ratio of 6.5:1 is maintained at the exit of the combustor while varying the inlet Reynolds number at a constant global equivalence ratio. Flame dynamics based on conditionally phase averaged OH* chemiluminescence images and spatial Rayleigh index maps were used to compare different flowrate and exit boundary cases. The outlet contraction affects both the frequency and amplitude of the dominant thermoacoustic mode. The orifice plate at the exit reduces the outlet reflection coefficient leading to a change in acoustic mode shape inside the combustor. Overall, the instability amplitude is reduced considerably for cases with orifice plate at the exit boundary compared to open exit boundary cases. The results show the importance of defining outlet boundary condition as a parameter in combustion instability studies. Care should be taken while comparing and interpreting results from different facilities where outlet boundary condition is different.
Design of a 2 MW Molten Salt Driven Supercritical CO2 Cycle and Turbomachinery for the SOLARSCO2OL Demonstration Project
Authors: Guédez Rafael , Barberis Stefano , Maccarini Simone , López-Román Anton , Milani Alberto , Pesatori Emanuel , Oyarzábal Unai , Sánchez Alvaro
Published: October 2022

Supercritical CO2 (sCO2) power cycles have been identified as technology enablers for increasing the cost-competitiveness of Concentrating Solar Power (CSP) plants. Compared to steam cycles, sCO2 cycles have the advantage of allowing higher inlet turbine temperatures, while also deploying turbomachinery that can be a ten-fold more compact. Ongoing research in CSP focuses mainly in developing new receiver and storage concepts able to withstand such required higher temperatures, alongside new heat exchangers that enable coupling to a sCO2 cycle. Meanwhile, advancements in sCO2 turbomachinery have taken place in research projects aimed at investigating the technical feasibility of the cycle, including the optimized design of its individual components and new cycle configurations. Among these, only few focus in demonstrating a full-integrated system, including cycle control and dynamics, and only two worldwide have started plans for MW-scale pilots, none of them in Europe. The EU-funded SOLARSCO2OL project aims at demonstrating a first-of-a-kind 2 MW gross simple-recuperated sCO2 Brayton cycle driven by heat provided by molten salts similar to those deployed in commercial CSP plants, which are able to operate at temperatures of up to 580°C. This paper introduces the project objectives and implementation plan, to then focus primarily on the results derived from the first year in specific relation to the conceptual design of each of 2 MW scale power cycle and its key components, including also the proposed integration and operational regimes, expected thermodynamic performance at nominal point, and up-scaling considerations.
Effusion Cooling: Influence of Pressure Drop
Authors: Bonds Michael , Wahls Benjamin H. , Ekkad Srinath V. , Rudrapatna Nagaraja , Dudebout Rudy , Meyer Ryan
Published: October 2022

Combustor liners are exposed to significant thermal gradients with hot combustion gases on one side and compressor directed cooling air on the other side. To maintain effective life of the liners, development of effective methods to cool gas turbine combustor liners are a necessity. Effusion cooling uses uniformly spaced holes distributed throughout the surface of the combustor liner to introduce convective and film cooling to form a protective layer of coolant along the liner wall and hence reduce the impact of the combustion gases. This experimental study investigates the overall cooling effectiveness of effusion cooling under realistic crossflow coolant operating conditions. The primary factors influencing the coolant mass flow that passed through the liner into the hot main flow was hole geometry, coolant and main flow speed, and pressure drop. For this study, 4 different effusion cooling liners with increasing levels of hole density were studied. Each hole had a length to diameter ratio (L/D) of 5.8. Non-dimensionalized hole to hole spacing in the streamwise (x/D) and spanwise (y/D) direction was equal and included spacings 7.9, 11.2, 15.8, and 22.5. These configurations were tested at uniform hot side and cold side flow speeds of 7 m/s and 15 m/s with both co-flow and counter-flow coolant directions. Pressure drop through the plate was set to 2% and 4% for 7 m/s flow speed and 4% for the 15 m/s condition. Infrared Thermography (IRT) was utilized to capture hot side and cold side liner steady state temperatures. Overall, co-flow conditions resulted in higher coolant mass flow passing through the liner while counter-flow conditions increased performance. The highest hole density configuration had a 20.3% average increase in performance over the next best performing liner geometry. In addition, the highest percentage of air passed through the effusion plate liners at the lower flow rate conditions with a 4% pressure drop. Based upon the experiments done, it was clear that while multiple factors influenced the overall cooling performance of combustor liners, a higher pressure drop consistently resulted in increased performance while higher flow speed resulted in reduced overall cooling performance.
High-Fuel Loading Ignition Delay Time Characterization of Hydrogen/Natural Gas/Ammonia at Gas Turbine-Relevant Conditions Inside a High-Pressure Shock Tube
Authors: Pierro Michael , Urso Justin , Kinney Cory , Kesharwani Shubham , McGaunn Jonathan , Dennis Christopher , Vasu Subith S.
Published: October 2022

This study explores the combustion characterization of high-fuel percentage, air-diluted mixtures of H2 mixed with natural gas (NG) as well as mixtures of H2 and NH3 at temperatures and pressures relevant to turbine operating conditions (20–30 bar, 1000–1500 K). Lower temperatures (below 1070 K) exhibit preignition characteristics due to non-homogeneity. An attempt to mitigate these occurrences at high pressures is investigated using the constrained reaction volume (CRV) stage-filling technique. Due to the need to further refine the facility CRV stage-filling uncertainty, only higher temperature data will be interpreted at this time. The test conditions in this study closely replicate the temperatures, pressures, and mixtures that would be seen in hydrogen-powered gas turbines, making it the first to explore such conditions. The experimental IDTs were compared against the current state-of-the-art chemical kinetic models for mechanism validation. The current work will advance H2-powered turbines and aims to determine the optimum molecular ratio of H2 when mixed with natural gas.
Emission Characteristics of Aviation Kerosene Combustion Under Near-Critical and Supercritical Fuel Injections
Authors: Yang Yue , Xue Xin , Hui Xin , Tan Yaxin , Wei Wei , Liu Cheng , Lin Yuzhen
Published: October 2022

The emission characteristics of a model centrally staged lean premixed prevaporized (LPP) combustor was investigated under near-critical and supercritical main fuel injections. The Chinese aviation kerosene, RP-3, with its critical temperature and pressure of 651 K and 2.35 MPa, was preheated from 500 to 740 K and pressurized from 2.0 to 3.5 MPa before being injected into the combustor. The combustor liner consists of ceramic matrix composites (CMC), which are installed on a water-cooling frame. Therefore, the combustor features a high dome air ratio (95% of the total air) by removing both primary and dilution holes and redirecting the liner cooling air to the dome. The overall fuel-to-air ratio was varied from 0.030 to 0.053. The emissions at the combustor outlet were measured at various operating conditions in the range of inlet air temperatures from 600 to 840 K and pressures from 2.0 to 2.8 MPa. The results showed that EINOx decreases about 40% as the injection temperature increase from 500 K to 740 K at 2.0 to 2.4 MPa injection pressure. It indicates that the transition from liquid fuel to supercritical fuel drastically reduces fuel density and surface tension. Increasing injection fuel temperature significantly improves the fuel/air mixing and avoids hot spot formation that favors NOx formation. Both EICO and EIUHC decrease slightly with increasing fuel injection temperature, suggesting a weak relation between the combustion efficiency and fuel thermodynamic state. The finding of the current study suggests that the NOx emissions are affected by the premixing quality of the main injector and may be reduced by injecting supercritical kerosene.