bluuebunny/crossref_metadata_2025 huggingface dataset:
A Frequency-Time Partitioned Approach for Computing Fan Blade Flutter Induced Limit Cycle Oscillations With Nonlinear Friction on Contact Interfaces
Authors: Ombret Nicolas , Daon Renaud , Dugeai Alain , Thouverez Fabrice , Blanc Laurent
Published: September 2023

This paper aims at introducing a new methodology to analyse aeroelastic stability of transonic fans while nonlinear friction on contact interfaces is taken into account. This methodology consists in an iterative procedure where the nonlinear dynamics of the structure and aerodynamic forces are respectively computed while imposing each one to the other in a fixed point loop. Hence, both physics are resolved while taking into account the nonlinearities of the other one, leading to a description of the fully coupled fluid structure system nonlinear dynamics. To do so, a harmonic description of the structure dynamics is performed using nonlinear complex modes, while the fluid is evaluated in temporal domain solving Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. Aeroelastic simulations are performed on the whole annulus, in Arbitrary Lagrangian Eulerian (ALE) formulation. An application of this methodology is performed on an industrial state of the art transonic fan to demonstrate its capability of predicting flutter induced Limit Cycle of Oscillations (LCO).
Low-Noise Design of Axial Fans Through Optimized Spanwise Application of Leading Edge Serrations
Authors: Felker Alexander , Biedermann Till M. , Kameier Frank
Published: September 2023

Recent studies have shown that leading edge serrations can effectively reduce broadband noise in axial fans and expand their operational range. However, additional aerodynamic losses have to be considered alongside the benefits of improved acoustic performance. The majority of studies focused on applying leading edge serrations along the entire span of the rotor blades regardless of local differences in radial inflow angles, deflection effects, and blade loading. In this regard, local and spanwise varying applications of leading edge serrations are considered crucial to reconciling maximum aeroacoustic and aerodynamic performance. In making these applications, a fan blade span is divided into five sub-segments. Each segment can then be equipped with either an acoustic or aerodynamic optimum as well as a baseline straight leading edge. Through testing at three different inflow turbulence levels along the full characteristic curve, an extensive statistical experimental design is executed. Ultimately, a simplified statistical model is derived. The model provides information on the optimum spanwise shape of a serration design. The results indicate significant effects of the local spanwise selection of varying serration designs. Discrepancies between aerodynamic and aeroacoustic optimum solutions can be satisfactorily resolved where, primarily, a significant extension of the working area is observed. Moreover, an extended potential in the delay of stall entry and the associated improvement of total pressure as well as a significant reduction of aeroacoustic signature is found. The underlying mechanisms are attributed to the compartmentalization effects of the serrations which restrict separation phenomena to local cells of finite spanwise extension. Furthermore, the spanwise geometrical parametrization of the serration segments correlates well with radial blade loading as well as respective flow conditions. By taking the radial distribution of aerodynamic quantities into account, an individual design of locally applied leading edge serrations can be integrated into the fan design process, enabling improved balancing between aeroacoustic benefits while maximizing aerodynamic performance.
Simulating Stall Inception in a High-Performance Fan
Authors: Bedke Andrew M. , Gorrell Steven E.
Published: September 2023

Aircraft engine performance and stability is limited by the onset of flow instabilities, such as rotating stall or surge. Although much research has been conducted on the subject, the mechanisms by which spike-type stall inception occurs in highspeed machines are still not well understood. This paper investigates the mechanisms of stall inception in a highly-loaded transonic fan rotor using full-annulus Unsteady Reynold’s-Averaged Navier-Stokes (URANS) simulations. Comparisons are made between the flow phenomena at the near-stall operating point and as stall inception occurs. The mechanisms of stall inception are shown to be interactions between the detached bow shock and the tip leakage vortex. These interactions result in two vortices within the blade passage near the rotor tips. The location and strength of these vortices affect leading edge spillage in the adjacent blade row. At the near-stall operating point, the vortices impact the pressure surface of the adjacent blade and then convect downstream. Stall inception occurs when the bow shock has moved far enough upstream to allow the resultant passage vortices from the shock/tip leakage vortex interaction to pass in front of the leading edge of the adjacent blade. After this, radial vortical structures are seen at the blade tips, much like what is observed in low-speed compressors. Understanding the mechanisms of stall inception in high-speed fans will allow for appropriate steps to be taken to delay stall inception and extend the stable operating range of the fan.
Hydrogen Co-Firing Demonstration at Georgia Power’s Plant McDonough: M501G Gas Turbine
Authors: Harper James , Cloyd Scott , Pigon Travis , Thomas Benjamin , Wilson Jeff , Johnson Eric , Noble David R.
Published: September 2023

As carbon reduction goals are being established worldwide with various target dates ranging from reductions by typical timeframes around 2030 to net-zero by 2050, the power industry is anticipated to lead the charge in reduction while having great demand placed from other industries. Many pathways to carbon-free power must be considered, as a portfolio will be necessary to keep energy costs low while keeping high reliability and widespread availability. As a subset, the gas turbine power industry is extremely interested in hydrogen as an alternative fuel to natural gas as a means of reducing, and eventually eliminating, CO2 emissions. Tests, up to full-scale demonstrations, are now being executed to further industry knowledge on co-firing natural gas with increasing levels of hydrogen. Challenges with blending high enough levels of hydrogen to make significant reductions of CO2 emissions will be numerous. This paper serves to provide information around the gas turbine performance, emissions, and emissions compliant load range effects of hydrogen on a Mitsubishi Power Advanced Class M501G gas turbine. The results of the testing are reviewed in the context of near-term needs such as operational flexibility with renewable penetration and the future energy transition considerations, particularly energy storage. The energy transition and the role of hydrogen in that transition has been mostly based on projections and small-scale testing. This paper provides additional practical information of the influence hydrogen has on gas turbine combustion and specifically the impact of hydrogen blending with natural gas on a large, modern high efficiency combined cycle power plant. Results of the testing provide needed and positive information on near-term and future energy transition needs. The results provide information valuable to the industry around operability and emissions expectations with hydrogen fuel usage.
Burst Speed Prediction of Impellers With Critical Strain Criteria
Authors: Sarıten Alper , Tabakçı Burak , Çopur Furkan , Kutmaral Alican , Akpınar İlkan Hasan
Published: September 2023

Accurate prediction of burst speed and critical location of a rotating disk is a great concern for turbomachinery designers and enables the reduction of test numbers required to show rotor integrity during turbo engine certification. Existing burst methodologies mainly focused on axial disks with well-defined bore, web, and rim regions and mostly depended on correction factors that require previous test data of rotors with similar sizes and features. Furthermore, variation of radial and hoop stresses in a radial disk is less predictable than in axial disks due to the asymmetric nature of impellers, which results in uneven distribution of centrifugal and bending loads. This paper aims to explain the experimental and numerical effort dedicated to building an accurate burst methodology for impellers. Elastoplastic finite element analyses are performed by incorporating geometric and material nonlinearities. Analysis results allowed the prediction of failure locations and observation of redistribution of stresses due to material plasticity as rotor speed increases. An extensive test campaign is carried out to validate the numerical analysis. Critical strain criteria, which corresponds to the plastic strain of true ultimate tensile strength (UTS), is used to determine burst speeds before tests. Experimental results are compared with Robinson’s Average Hoop Stress Criteria, Hallinan’s Criteria, and Critical Strain Criteria to show the strong and weak sides of these methodologies for an impeller application. The numerical burst speeds and crack initiation locations associated with critical strain criteria are found to be in good agreement with the spin test results.
Experimental Study on the Difference of Direct Damping Coefficients for Piston Ring End-Sealed Squeeze Film Damper With an Offset Groove
Authors: Zhang Guanghui , Huang Yanzhong , Sun Wenlong , Guo Yang , Gong Wenjie
Published: September 2023

The damping performance of squeeze film dampers (SFDs) is affected by feed hole distribution, feed pressure, and the number of feed holes. Common uncertainty differences exist between the direct force coefficients KXX and KYY, or CXX and CYY identified by the test. In this paper, the force coefficients identification test was carried out for a new piston ring end-sealed squeeze film damper with an offset groove. An original form of piston ring end seal, the double piston rings (DPRs), is tested and proven effective. The dimensionless direct damping coefficients CXX and CYY were identified using the instrument variable filter method (IVFM), and the absolute difference ΔC = abs (CXX – CYY) was calculated. Besides, the SFD damping performance was evaluated using the mean damping coefficient Cave = (CXX+CYY)/2. Last, the effects of feed hole distribution, feed pressure PH and the number of feed holes NH on the Cave and ΔC were investigated. The results show that the Cave and ΔC are affected by these factors. The Cave is larger (Cave > 3.0 at NH = 1), and ΔC is smaller (ΔC < 0.10 at NH = 1) when the feed holes are located upper than those located lower, and the more feed holes are located upper, the larger the Cave. In the low-pressure zone (PH < ∼1.5 bar), the Cave decreases as the feed pressure increases and increases as the feed pressure in the medium and high-pressure zones (PH > ∼1.5 bar). The Cave and ΔC can be slightly decreased by increasing the number of feed holes when the feed pressure is low, and yet the ΔC increases as the number of feed holes when the feed pressure is high. It is more effective to improve the damping coefficient by increasing the feed pressure than the number of feed holes, but the Cave will not increase significantly if the number of feed holes or feed pressure is increased continuously. The Cave and ΔC are related to the leakage and the evenly distributed form of internal oil, respectively. There may be a virtual threshold PNt that cannot be defined precisely for the feed pressure and the number of feed holes; the variation in feed pressure and the number of feed holes in the same direction results in a diametrically opposed pattern before and after this virtual threshold PNt, and the influence of the number of feed holes dominates the decrease of ΔC before the PNt. In contrast, the influence of the feed pressure dominates after the PNt. A sensitivity analysis reveals that the number of feed holes in the medium and high-pressure zones significantly influences the fluctuation of ΔC (ΔC fluctuates in the range of 0.17 to 1.45). Moreover, the factor of feed pressure at NH = 6 may lead to abnormal fluctuations of the ΔC.
Development of a Custom Mesh Generation Tool for Low Solidity Axial Flow Fans
Authors: Stephan Gideon A. , Van der Spuy Sybrand J. , Meyer Chris
Published: September 2023

This paper outlines a method used to generate a three dimensional, periodic, annular mesh for a large diameter, low solidity, axial flow fan. The meshing methodology generates a 2-D airfoil mesh at specified radial stations along the blade span. The 2-D airfoil meshes are stacked and wrapped to create the mesh of the axial flow fan. The 2-D airfoil meshing methodology inserts a blunt trailing edge to more closely match a physical fan blade where the trailing edge is not infinitely thin. The airfoil meshing algorithm uses airfoil characterisation, using Bezier spline regions, and extrusion to create a highly orthogonal near-wall mesh. A versatile spline relaxation method is developed to relax the mesh from the near-wall region to the far field geometry. The meshing tool is used to conduct an incompressible, steady state, Computational Fluid Dynamics (CFD) study of the B2a-fan using OpenFOAM. Correction factors are used to correct for the absence of the tip gap in the domain modelling. The corrected pressure characteristic was most accurate at the design point volume flow rate, attaining a deviation of 2.5% with a Grid Convergence Index (GCI) of 3.6%. The static efficiency was predicted with a deviation of 5% at the design point flow rate. The deviation in efficiency is caused by an increased static pressure rise due to domain simplifications leading to a lower blade torque. The blade swirl velocity showed good correlation with reference data with small deviations toward the blade tip.
Development of Nickel-Based Superalloys for Hot Gas Path Components via Additive Manufacturing
Authors: Callisti Mauro , Dimatteo Antonella
Published: September 2023

High performance Nickel-based superalloys are known to be difficult-to-weld materials due to their complex chemical compositions. Consequently, these alloys become challenging when processed via additive manufacturing (AM) technologies. In this study, new AM Nickel-based superalloys were developed for applications in gas turbines, with particular regard to hot gas path components like turbine vanes for Baker Hughes products. The alloy development was driven by the performance required for the specific components, with emphasis on creep and oxidation resistance.

This paper describes all the steps that led to design and manufacture of an AM alloy free of defects and with required performance. In particular, the alloy design approach based on thermodynamics calculations and fast experimentation is described. AM process parameters development along with post-printing treatments (hot isostatic pressing and heat treatments) are discussed in conjunction with the emerging mechanical properties. An assessment on the oxidation behaviour of a selected alloy is presented.
Improving Performance of a Centrifugal Pump Through a CFD DOE Study of Radial Diffuser Design
Authors: Parmar Basu , Sacks Michael , Jammalamadaka Avinash , Laskowski Gregory
Published: September 2023

Diffuser design significantly affects the performance of a centrifugal pump. To improve the performance of a single stage centrifugal pump, we use RANS CFD simulations to conduct a Latin hypercube DOE study with the diffuser design parameters. The inlet angle, outlet angle, outlet diameter and number of vanes are selected to be key parameters influencing the pump performance. The ERCOFTAC pump is selected as the research model. The CFD simulations and DOE study are conducted using 3DEXPERIENCE® CFD simulations by Dassault Systemes. The results indicate multiple optimal designs for different zones of operation and the choice of response variables to optimize. Pump efficiency is chosen to be the key performance indicator in this paper. The first optimal design for nominal flow rates showed better performance due to an improvement in diffuser static pressure rise coefficient. The second improved design for high flow rates, removes flow separation at high flow rates by reducing the vane inlet and outlet angles. It is found that low values of inlet angle and outlet angle give better pump efficiency at high flow rates and vice versa. We also demonstrate the benefits of RANS CFD over simple 1D analysis.
Compressor Tip Leakage Mechanisms
Authors: Taylor James V. , Dickens Anthony M. J. , Simpson Harry
Published: September 2023

The over tip leakage flow in an unshrouded compressor blade row is highly three-dimensional, yet in order for aerodynamicists to analyse and improve designs they must be able to simplify the problem down to a limited number of mechanisms. In this paper the behaviours of the dominant loss mechanisms are investigated using a multi-order methodology which combines: rapid experimental tests of different geometries, detailed measurements in a large rotating rig, large numbers of industry-standard 3D RANS simulations and a single DNS simulation of the datum geometry.

The three loss mechanisms identified are ultimately caused by mismatches in flow velocity. Separation of the flow as it enters the gap, mixing of the leakage jet with the mainstream close to the suction surface, and endwall shear acting on the jet itself at mid passage. The paper is presented in three sections: First, the loss mechanisms are visualised and examined in detail using experiment, simulation and models. Second, the uncertainty in industry-standard predictions is analysed and improvements to turbulence modelling are presented. Finally, amatrix of blades with different 3D designs is used to investigate the balance of loss mechanisms and a reduction in total loss generation.
Reynolds Number Impact on High Pressure Turbine Flows
Authors: Osusky Michal , Ledezma Gustavo , Sluyter Greg , Shankaran Sriram
Published: September 2023

During operation, turbine blades in aircraft engines can experience flows over a wide range of Reynolds numbers. This range is impacted by engines of different sizes, as well as different operating altitudes, all of which add to the overall range of Reynolds numbers that are relevant for aircraft engine design. Unfortunately, increasing flow Reynolds number has a significant impact on the mesh resolution required for accurately simulating wall-resolved LES models due to the mesh resolution required to capture the near-wall flow physics. During the design process, providing engineers a detailed understanding of the flow physics phenomena, and how they change with Reynolds number, could lead to more efficient and durable turbine designs.

In this paper we present the study of flows around an uncooled high-pressure turbine blade. The simulations are completed with the high-order GENESIS code, which has been successfully applied to thread-parallel compute architectures, such as large computational systems with GPU capability. The simulations cover a range of Reynolds numbers in order to study the impact of Reynolds number increase over a fixed geometry. This allows for examining the impact on flow physics of interest, such as boundary layer evolution, laminar-to-turbulent transition, and wake shedding. The numerical results show that as Reynolds number is increased, a critical value is reached where the shedding behavior of trailing edge vortices changes, resulting in a jump in wake loss. Examination of the local flowfield quantities demonstrates that this change is due to a shift from laminar to turbulent flow on both sides of the airfoil, contributing to destabilization of the shear layer, resulting in larger vortices being shed.
Cross Boundary Design Optimization Using Simulation Process and Data Management
Authors: Malton Ken , Paiva Ricardo , Keskin Akin , Riaz Atif , Mourouzidis Christos
Published: September 2023

Even at the preliminary level, Multidisciplinary Design Optimization (MDO) of a novel aircraft concept is a challenging prospect. There, the interaction between airframe design and propulsion design tasks is particularly strong and can simultaneously be a weak link if not dealt with adequately. In the case of civil aviation, the constraints around sharing of data and tools (i.e., Intellectual Property) across organizational boundaries usually preclude an effective communication between the airframer and propulsor supplier. As such, the design of the airframe and propulsion system are usually done in isolation with occasional transfers of limited amounts of data, often leading to suboptimal results due to sequential subsystem optimization having effectively taken place rather than an overall and fully integrated system optimization.

In the present work, the Simulation Process and Data Management (SPDM) paradigm is employed to explore the benefits of automated encapsulation, transfer and ultimately storage of data during the design exploration process of an aircraft concept while ensuring compatibility of attributes between airframe design and engine design disciplines at each iteration, i.e. fully converged airframe-propulsor iterates, where the propulsion system provides exactly the thrust the airframe requires and the design of the latter is fully aware of the performance of the engine in the flight envelope it is being required to operate within.
Acoustic and Optical Investigations of the Flame Dynamics of Rich and Lean Kerosene Flames in the Primary Zone of an Air-Staged Combustion Test-Rig
Authors: March Martin , Renner Julian , Sattelmayer Thomas
Published: September 2023

In this study the thermoacoustic behavior of non-premixed kerosene flames from rich to lean combustion conditions is investigated. Flame-transfer-functions measured purely acoustically are compared with results based on flame chemiluminescence. OH*, CH*, C2* and CO2* were selected as potential measures for representing steady and fluctuating heat release when burning non-premixed kerosene. In addition, their ability for the quantification of equivalence ratio fluctuations will be highlighted. The measurements were performed in the primary zone of an atmospheric rich-quench-lean (RQL) combustion test-rig. The new experimental approach allows a characterization of the primary zone independent of the secondary zone. Rich and lean operating points were analyzed by fueling an aero-engine prototype injector with and without acoustic excitation. To improve the quality of the acoustic wavefield reconstruction a thermocouple correction method was implemented. The flame dynamics determined with the multimicrophone method exhibit a frequency and equivalence ratio depending effect for rich combustion conditions. The results for the steady behavior of the chosen radicals by altering equivalence ratio and thermal power indicate proportionality of the chemiluminescence to thermal power. Furthermore, the CH*/C2* ratio is found to be a promising indicator for the global equivalence ratio in the combustion chamber. The flame-transfer-functions based on chemiluminescence show a good qualitative agreement with the multimicrophone method. Based on the experimental findings a calibration curve for the different radicals to obtain quantitatively correct flame-transfer-functions from chemiluminescence is presented.
Effect of the Position of the Centerbody on Thermoacoustic Instabilities in a Central-Staged Model Combustor
Authors: Han Meng , Han Xiao , Gan Zhichao
Published: September 2023

The present study investigates the effect of the position of the centerbody on thermoacoustic instabilities in a central-staged model combustor with a dual-swirl layout. The position of the centerbody significantly influences the combustor’s vortex breakdown and combustion performance, such as combustion instability. In this paper, three different axial positions of the center body are studied experimentally under atmospheric pressure and temperature with premixed methane-air mixtures. The result shows that the position of the center body alters the pilot flame shape, and then the overall flame shape changes, no lifted flames have been discovered in the case of the center body in the Down-5mm. The degradation of the centerbody also could increase the amplitudes of pressure oscillation in the combustor. Moreover, the dominant frequency of oscillation is different with different positions of the center body. The beating oscillations are also found in three positions of the center body. Flame dynamics are further analyzed using the Dynamic Mode Decomposition method. It is concluded that the cases of the center body downstream have the best thermoacoustic stability within the tested range of three cases. The flow mechanisms of three different center body positions have been revealed using the numerical simulation of RANS. It is found that the degradation of the center body could decrease its ability of stabilized the pilot flame and then decrease the thermoacoustic stability.
Numerical Investigation of NH3 Doped Fuels From Biomass Gasification on Fuel-Bound NOx Formation at Gas Turbine Conditions
Authors: Yang Silin , Raslan Ahmed , Durocher Antoine , Güthe Felix , Bergthorson Jeffrey
Published: September 2023

As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions, renewable energy sources are needed to meet the increasing energy demand in the near future. Biomass, consisting mostly of plant-based organic materials, is a promising alternative to fossil fuels for carbon-neutral energy production. Unfortunately, during the gasification process, the nitrogen content in biomass is converted to NH3, which is then oxidized in the combustion process, leading to high NOx emissions through the fuel-NO pathway. The high NOx emissions from NH3 and NH3-containing fuels have prevented their implementation at scale. Depending on the gasification process, source of biomass, and combustion technology, the NH3 and water content can vary greatly. This works focuses on blends of 2% (mol) NH3 in CH4, diluted by up to 55% (mass) water. The combustion process is modelled by freeflame connected to a plug flow reactor (PFR), achieving a total residence time of 100 ms. Major chemistry involved in the fuel NO pathway were identified from reaction pathway analysis. NOx emissions were investigated under different equivalence ratios (Φ = 0.45–2.2) and inlet pressures (1 atm, 40 atm). NO concentration increases rapidly as NH3 is added to the fuel mixture, as expected. Under fuel rich conditions, NO decreases after the initial increase, and this reduction becomes more pronounced at elevated pressure and long residence times. At the same time, unburned NH3 and other reactive N species increase as NO decreases. The optimal conditions that minimize the total NOx and NH3 emissions were found to be slightly fuel rich, high pressure, and long residence time. Under these conditions, additional pathways involving NNH and N2O promotes the conversion of NH3 to N2. Large discrepancies among different thermochemical mechanisms highlight areas that still need to be researched. Results from the current study can assist in the modelling and design of low-emissions engines fuelled by biomass and NH3, thereby contributing to a carbon-neutral economy.
Towards Scales Resolving Direct Simulation of a Hydrogen/Air Lean Premixed Flame With Swirler-Induced Turbulence
Authors: Xiao Gan , Palies Paul
Published: September 2023

This article introduces a computational tool for scales resolving simulations of chemically reacting flows applicable to moderately complex geometries and relevant operating conditions. The advantage of the presented methodology is to retain finite rate chemistry with single step chemical kinetic mechanism coupled with detailed transport to solve for turbulence flow scales, both integral and Kolmogorov scales, as well as flame scales. This enables to limit the cost associated with complex chemical mechanisms. The approach is applied here to an atmospheric laboratory-scale configuration to study high-swirled 100% H2/Air fully premixed flame ignition, a key knowledge gap in the literature. This configuration includes the geometry effects from the swirler that have an essential role in turbulence scale generation driving the flame wrinkling. The computational tool is based on open-source codes, the finite volume OpenFOAM9 solver where detailed transport data from Cantera are integrated. The paper presents the transport model validation, the single-step kinetic mechanism development, the high-performance computing scaling study, the premixed turbulent combustion regime assessment, the geometry, the mesh, and the numerical settings. The non-reacting flowfield and ignition transient sequence numerical results obtained are discussed. Key non-reacting establishing swirling flow features, inner recirculation zone and swirling jet, are captured. The ignition method strategy is devised from 1D premixed flame ignitions tests. It is next applied to the 3D configuration to ignite the premixture. This provides a computational capability to assess multiple ignition scenarios to initiate flame propagation.
Methods and Apparatus for Real-Time Seal Clearances Assessment Using a Pressure Measurement
Authors: Kim Taehong
Published: September 2023

Today’s aircraft turbine engines are exposed to higher temperatures, higher pressure with the need of increased rotor life to meet customer demand with higher thrust and better fuel efficiency. The case structure and rotating parts have different thermal and mechanical expansion and contraction which drive clearances to be excessive. In most of commercial engines, interstage seals (ISS) and mid-seals connected to tip clearance control system are designed to schedule seal clearances to maintain cavity pressures and balance purge flow. The system is designed to manage the gap for efficiency but prevent hot gas ingestion from overheating during engine operation.

Measurement of seal clearances would be a crucial way to understand seal clearance changes and to design purge flow for secondary flow and thermal design. For example, real time measurement would provide a way to adjust seal gaps to maintain turbine efficiency in new and deteriorated conditions. However, there is no promising method or an apparatus to sense and measure seal clearances in actual engine test or operation because ISS and mid-seals are located at inner flow path, such as buffer cavities through vane or nozzle, which are not favorable to directly install clearance probes and sensors.

This study is to review flight test data of turbine mid-seal clearance and radial tip clearances measurement and demonstrate its linear correlation between pressure and temperature against clearance changes during test of different operating conditions such as power calibration test at low and high altitudes and Active Clearance Control (ACC) valve swing test at high power. As a result, the study proposes new methods to assess seal clearances using conventional pressure sensors at forward and aft cavities with the linear conversion curves. The conversion method was developed for new engines tests, but it can be applicable for deteriorated conditions of production engines to improve efficiency and operability if independent seal clearance control system is developed and adapted.
A Method for Preliminary Design of Variable Geometry Vaned Diffuser for Centrifugal Compressor
Authors: Tamaki Hideaki , Yamaguchi Satoshi
Published: September 2023

Centrifugal compressors require a wide operating range as well as high efficiency. Typical active control forms to enhance the operating range are suction throttling with a valve in a suction line, discharge throttling with a ring installed in a vaneless diffuser, variable inlet guide vanes, and variable geometry vaned diffuser. This study focuses on the design of a variable geometry vaned diffuser (VVD) whose vane rotates around a pivot to adjust its opening and proposes a method to estimate the main parameters of a VVD at the preliminary design stage. The design method here is based on matching the diffuser vane inlet angles with the flow angles at the diffuser inlet. If the designed VVD can maintain low incidence at the diffuser vane leading edge over the whole movable range of the vane is evaluated. A graph, which indicates the relation between the diffuser vane inlet angles and the flow angles at the diffuser inlet at diffuser choking and diffuser stalling, makes the evaluation easy. The proposed procedures were applied to select the number of vanes of a VVD for a turbocharger compressor. Tests for the validation of the design procedures were conducted by using fixed vaned diffusers that simulated the VVDs installed on the turbocharger with an 85mm-diameter impeller. The results showed the effectiveness of the proposed design procedures. This paper first presents examples of applications of the typical active methods extending centrifugal compressors’ operating range for real machines and then discusses the design of VVD.
Rotor-Rotor Cavity Flowfield in the Presence of Radially Inward Flow With Different Co-Rotational Speeds
Authors: Erdem Erinc , Karasu Zeki Tugberk , Yilmaz Sefa , Yazan Alican , Sal Sinan
Published: September 2023

This article aims at the investigation of rotor-rotor cavity flowfield using CFD and one-dimensional flow solver for a representative engine configuration. The numerical approach is validated against the test data of Firuzian et. al. for a simpler rotor-rotor cavity geometry, in terms of the location of zero radial velocity signifying the extent of entraining source region and the swirl ratio distributions in radial direction, for three different λT values. Afterwards the flowfield in the current configuration is numerically predicted using the same numerical approach at various engine thrust settings corresponding to a wide range of dissimilar rotational speed ratios (0.34–0.67). Zero radial velocity location is observed on the high-pressure structure and it moves from low radii at low thrust levels to medium radii at high thrust levels. On the low-pressure disk side, the flow is radially inward for all the cases. At low thrust settings the flowfield resembles a forced vortex-like flow, where torques generated on both disks prevent tangential acceleration of the flow.
Extension and Validation of the Turbomachinery Capabilities of SU2 Open Source CFD Code
Authors: Yan Chuanxiang , Wang Baotong , He Xiao , Zhao Fanzhou , Zheng Xuedong , Vahdati Mehdi , Zheng Xinqian
Published: September 2023

Computational Fluid Dynamic (CFD) tools have revolutionized the way to design engineering systems, but most established codes are proprietary and closed-source, making it difficult, if not impossible, to modify, debug or add new features to the code. To provide a freely available open-source CFD code for turbomachinery aerodynamics and aeroelasticity, this paper enhances the turbomachinery capabilities of the open-source SU2 code and demonstrates its capabilities of single-passage steady simulation, full-annulus unsteady simulation and aeroelasticity analysis in two high-speed compressors, namely NASA Stage 35 and TUDa-GLR-OpenStage, and a linear cascade SC1. For the single-passage steady simulation of NASA Stage 35, the SU2 results are validated against the measured data and verified against the commercial solver Ansys CFX, and the performance characteristics results are in reasonably good agreement with each other. For the single-passage steady simulation of TUDa-GLR-OpenStage, grid and turbulence model sensitivity studies are performed and results are validated against the measured data, and SU2 can predict both the performance characteristics and the radial profiles with sufficient accuracy. For the full-annulus unsteady simulation of NASA Stage 35, it is demonstrated that SU2 can predict the propagation of inlet distortion equally well as Ansys CFX. For the linear cascade, SU2 can predict the unsteady pressure and aerodynamic damping coefficient accurately. The presented results demonstrate the turbomachinery aerodynamics and aeroelasticity capabilities of SU2. The major modifications of SU2 made in this work will be shared with the code maintainer and the community in the future.
Configuration of Organic Rankine Cycles for Geothermal Applications: An Industrial Perspective
Authors: Pettinari Matteo , Dago Gnandjuet Gaston Brice , Frate Guido Francesco , Baccioli Andrea , Ferrari Lorenzo , Desideri Umberto , Amidei Simone , Cosi Lorenzo
Published: September 2023

Geothermal resources represent a valuable option to reduce fossil fuel-based power production because they feature an unmatched capacity factor among other Renewable Energy Sources (RES). Geothermal resource availability reduces with the temperature. Therefore, developing cost-effective solutions to exploit low-temperature geothermal energy is mandatory to expand technology utilisation. The standard solution for converting low-temperature thermal sources into power is Organic Rankine Cycles (ORC). ORC basic layout (subcritical) is well-known, but the more advanced alternatives, such as transcritical and two-pressure level cycles, are much less widespread, and it is unclear whether the higher efficiency justifies the higher capital cost. The paper focuses on the exploitation with ORC of geothermal resources (hot water) with a temperature lower than 200°C and mass flow rates between 200 and 1400 m3/h for a target power production ranging from 3 to 30 MW. The paper compares three ORC layouts, subcritical, transcritical and two pressure-level, from thermodynamic and economic points of view to map the most cost-effective solutions in the investigated size ranges. The techno-economic comparison considers the impact of the operating conditions and fluid on the machine’s expected performance and the heat exchangers’ size. As expected, more complicated layouts yield higher conversion efficiencies, with the two pressure-level cycles achieving the highest power output for the same geothermal source conditions. However, the economic analysis showed that the most efficient solutions are not always preferable when considering the cost-efficiency trade-off.
Case Study of Compressor Blade Tip Clearance and Implications to Operational Flexibility of an Industrial Gas Turbine
Authors: Bullard Timothy , Paskin Marc , Vogel Greg , Smith Nathaniel
Published: September 2023

The flexibility of a gas turbine power plant is characterized by the ability to quickly start the machine (fast start) and respond to changes in grid demand (fast ramp). A quicker load response is more economically viable and highly desired by plant operators amid growing use of renewable energy sources.

For a gas turbine, a fast start or fast ramp procedure involves many concerns, not the least of which is compressor blade clearances. Blade rubs occur when compressor blade tips contact the engine casing and are a significant driver of wear and potential catastrophic damage to a rotor.

New units are being designed with fast start in mind, building in the necessary blade tip clearance from the factory. For installed fleets of commercially operating industrial gas turbines, blade tip clearance data is not widely available, making it difficult to fully understand feasibility of fast start/ramp. Additionally, only OEMs or those with detailed dimensional data, modelling capabilities and resources would have insight to blade clearance; however, without hard data there is still significant uncertainty.

The present effort is an attempt to measure blade tip clearances of a commercially operating gas turbine with the intention of facilitating fast start and fast ramp. An instrumented test was conducted involving installation of a sensor system to several stages of an industrial gas turbine compressor. The system was integrated to a controller with data link, and operator screen with alarm indications. A test cycle was carried out which varied the rate of starting and ramping. The results indicate a characteristic behaviour of the rotor and thus provide insight to operational flexibility. Finally, a model was developed which serves to provide further prediction for very high ramp rates. Limitations of the study and methodology are also discussed.
Stability of the Co- and Counter-Rotating Swirlers in a Liquid-Fueled Can Combustor
Authors: Kıyıcı Fırat , Topal Ahmet , Hepkaya Ender , Ozogul Hamdullah , Zayim Ahmet Kaan , Kaplan Mustafa , Percin Mustafa
Published: September 2023

This study experimentally investigates the effects of swirler channel orientation on combustion instability. For this purpose, the performance of the co- and counter-rotating radial-radial swirlers is assessed in terms of pressure fluctuations in a liquid-fueled can combustor operated with kerosene fuel. High-frequency pressure transducers are used to obtain pressure fluctuations in the combustor in non-reacting and reacting flow conditions. First, non-reacting experiments are conducted to observe the performance of the swirlers at mass flow rates of 10.5, 12, 14, and 15 g/s. Non-reacting experiments show that Precessing Vortex Core occurs at a Strouhal number of 1.9 and dominates the flow field for both swirlers. In the reacting conditions, the effect of the mass flow rate (10.5, 12, 14, and 15 g/s) at a constant fuel flow rate (0.7 g/s) and the impact of the fuel flow rate (0.7, 0.8, 0.9, and 1.0 g/s) at a constant mass flow rate (15 g/s) are investigated. The peak frequency decreases in the reacting conditions compared to non-reacting cases. In the constant fuel flow rate case, the Precessing Vortex Core is observed in the co-rotating swirler for all air flow rates, but it disappears in the counter-rotating swirler at higher mass flow rates. At the constant mass flow rate cases, combustion instability occurs in the co-rotating swirler, while the counter-rotating swirler operates without any sign of instability. In all reacting cases, the peak frequency amplitude is remarkably higher in the co-rotating swirler.
Development and Validation Under Engine Operation Environment of Addtively Manufactured Hot Turbine Parts
Authors: Lindbäck Martin , Frankolin Karin , Tuneskog Erika , Karlsson Björn , Wang Lieke
Published: September 2023

Additive Manufacturing (AM) has emerged as an innovative manufacturing method in comparison to traditionally subtractive method. Its unparalleled design freedom opened up the applications in gas turbine business where the efficiency improvement is consistently needed. While the AM application in combustion section has gained a lot of experience, the AM application in turbine hot gas path is still limited, e.g., most of the applications like vane 1 and vane 2 are limited to the gas turbines with relatively low operation temperatures. This paper presents the project where vane 1, heat shield 1 (HS1) and vane 2 in SGT-800 were redesigned with only AM enabled in-wall cooling schemes and these parts were tested and validated under the real engine operation environment. Through Design for Additive Manufacturing (DfAM), these parts were redesigned with lower cooling air consumption, reduced average metal temperature and more even temperature distribution. After that, these parts were additively manufactured in EOS M400-4 and post print quality checks were conducted to ensure the part quality. The quality check includes cut-up metallurgical investigation, hot air thermography test and water test, etc. All three AM parts were instrumented with thermo-couples and thermo-crystals, and tested under the full load engine operation condition. The crystal measurement results confirmed the reliability of the design tool as well as the design targets. For AM vane 1, a cooling air saving of more than 20% was achieved and the average metal temperature was reduced by 56 °C from the baseline of the cast vane 1. For AM HS1 and AM vane 2, the cooling air saving is not significant, but the average temperature was reduced by approximately 80 °C. This will result in significant increase in part life time, either to increase the part service interval or use it as basis for cooling air saving. With this validation under the engine environment, the implementation of these three AM parts is planned in the customer engines.
Turbulence Model Influence on Turbopump Inducer Performance
Authors: de Oliveira Igor , Bringhenti Cleverson , Takachi Jesuino , Adalgiza Garcia Maia Ana , Kapat Jayanta , Fernandez Erik
Published: September 2023

The use of inducers in turbopumps for liquid propellant rocket engines allowed operation at high rotational speeds, contributing to global vehicle performance improvement. Methods for designing inducers have been explored using analytical methods, experimental data and numerical solutions. The use of CFD for simulating and designing rocket turbopump inducers is a relevant practice because it can rapidly explore scenarios untested in the experimental endeavors for determining empirical functions. This technique also captures more problem details than reduced order analytical solutions. Turbomachines have a different accuracy in terms of solution prediction for different turbulence models and application. The flow specificity of the turbomachinery changes the adequate turbulence model to obtain a more accurate solution. For this reason, it is of interest to investigate how different turbulence modeling predicts the fluid flow behavior and their accuracy to calculate the inducers’ performance. The present work aims to investigate the capability of different turbulence models on the performance and flowfield obtained via CFD simulations of an inducer pump. The CFD simulations were performed using a commercial software for k-ϵ, RNG k-ϵ and Shear Stress Transport turbulence models. The simulations were performed on a known inducer geometry for which published experimental performance data as a function of operational conditions is available in literature. The present paper discusses the differences in the performance prediction and the flow field calculated for the turbulence models simulated. For the cases studied, the k-ϵ standard model shows better predictions for the efficiency and head coefficient compared with the experimental data demonstrating their accuracy in solving rotational flows.