bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advanced Exergy Analysis of the Supercritical Carbon Dioxide Power Cycle for Waste Heat Recovery of Gas Turbine
Authors: Li Bo , Wang Shun-sen , Song Liming 
Published: September 2021

Abstract
In this paper, the supercritical carbon dioxide power cycle used to recover the waste heat of gas turbine is investigated by means of conventional exergy analysis and advanced exergy analysis. Firstly, the thermodynamic parameters of carbon dioxide cycle in design stage are determined by single-objective optimization with net power output as objective function. Then, conventional exergy analysis is carried out on the partial heating cycle under real, unavoidable and ideal conditions. After that, advanced exergy analysis, in which the exergy destruction is divided into endogenous / exogenous part and avoidable / unavoidable part is adopted to reveal the improvement potential of the system and illustrate the interaction among the components. According to the calculation results, a total amount of 3.55MW (47.33%) exergy destruction could be reduced by the improvement of component efficiency. Endogenous exergy destruction is higher than exogenous exergy destruction in all components. Based on the results of conventional exergy analysis, the high-temperature heater should be paid attention in order to reduce exergy destruction. However, according to the results of advanced exergy analysis, the technical improvement of turbine should be emphasized due to its high endogenous-avoidable exergy destruction. Meanwhile, for the components with high unavoidable exergy destruction, external systems should be employed to exploit the underutilized energy and enhance the system performance.
Analysis of Swirl Number Effects on Effusion Flow Behaviour Using Time Resolved PIV
Authors: Lenzi T. , Picchi A. , Andreini A. , Facchini B. 
Published: September 2021

Abstract
The analysis of the interaction between the swirling and cooling flows, promoted by the liner film cooling system, is a fundamental task for the design of turbine combustion chambers since it influences different aspects such as emissions and cooling capability. In particular high turbulence values, flow instabilities, and tangential velocity components induced by the swirling flow deeply affect the behavior of effusion cooling jets, demanding for dedicated time-resolved near-wall experimental analysis. The experimental set up of this work consists of a non-reactive single-sector linear combustor test rig scaled up with respect to engine dimensions; the test section was equipped with an effusion plate with standard inclined cylindrical holes to simulate the liner cooling system. The rig was instrumented with a 2D Time-Resolved Particle Image Velocimetry system, focused on different field of views. The degree of swirl for a swirling flow is usually characterized by the swirl number, Sn, defined as the ratio of the tangential momentum flux to axial momentum flux. To assess the impact of such parameter on the near-wall effusion behavior, a set of three different axial swirlers with swirl number equal to Sn = 0.6 - 0.8 - 1.0 were designed and tested in the experimental apparatus. An analysis of the main flow field by varying the Sn was first performed in terms of average velocity, RMS, and Tu values, providing kinetic energy spectra and turbulence length scale information. In a second step, the analysis was focused on the near-wall regions: the strong effects of Sn on the coolant jets was quantified in terms of vorticity analysis and jet oscillation.
Design and Testing of a Multi-Stage IP Turbine for Future Geared Turbofans
Authors: Torre D. , García-Valdecasas G. , Puente A. , Hernández D. , Luque S. 
Published: September 2021

Abstract
The multi-stage intermediate pressure turbine (IPT) is a key enabler of the thermodynamic cycle in geared turbofan engine architectures, where fan and turbine rotational speeds become decoupled by employing a power gearbox between them. This allows for the separate aerodynamic optimization of both components, an increase in engine bypass ratios, higher propulsive efficiency, and lower specific fuel consumption. Due to significant aerodynamic differences with conventional low pressure turbines (LPTs), multi-stage IPT designs present new aerodynamic, mechanical and acoustic trade-offs. This work describes the aerodynamic design and experimental validation of a fully featured three-stage IP turbine, including a final row of outlet guide vanes.
Experiments have been conducted in a highly engine-representative transonic rotating wind tunnel at the CTA (Centro de Tecnologías Aeronáuticas, Spain), in which Mach and Reynolds numbers were matched to engine conditions. The design intent is shown to be fully validated. Efficiency levels are discussed in the context of a previous state-of-the-art LPT, tested in the same facility. It is argued that the efficiency gains of IPTs are due to higher pitch-to-chord ratios, which lead to a reduction in overall profile losses, and higher velocity ratios and lower turning angles, which reduce airfoil secondary flows and three-dimensional losses.
A Novel Airfoil Design Method and its Application to the Optimization Design of a 3-Stage Transonic Compressor
Authors: Wang Xiaochen , Ren Xiaodong , Li Xuesong , Wu Hong , Gu Chunwei 
Published: September 2021

Abstract
In this paper, a novel airfoil design method is proposed by introducing multiple physical characteristics to the process of parameterization. The new design method is to operate the camber and thickness distributions in a way that the chordwise mapping information is adjusted without using local geometrical parameters. A proper design space is expected to be constructed, in which the laws of optimization can be simply transmitted from a single airfoil to the whole blade and even stages. The capability of the method is firstly validated in the Pareto optimization of a 2D compressor airfoil, and then specialized for the optimization of a rotor in a 3-stage transonic compressor. The 3-stage transonic compressor studied in this paper is representative of the inlet stages of an industrial gas turbine, and the shock structure of the third rotor (R3) presents the peak strength near the mid span. The optimized design reduces the peak Mach number on the suction surface, and increases the efficiency of the third stage and the whole compressor by nearly 1% and 0.3% respectively. The mechanism of the loss optimization is analyzed in detail.
Development and Atmospheric Testing of a High Hydrogen FlameSheet™ Combustor for the OP16 Gas Turbine
Authors: Bouten Thijs , Withag Jan , Axelsson Lars-Uno , Koomen Joris , Jansen Diethard , Stuttaford Peter 
Published: September 2021

Abstract
Gas turbines with a combustion system for hydrogen operation offer a low carbon solution to support the stability of the energy grid. This provides a solution capturing the needs for energy storage, in the form of hydrogen, and flexible power generation. Fuel flexibility is a key requirement to reduce the operational risks in case hydrogen is not available, whereby hydrogen can be combined with other conventional or alternative fuels. A key issue to achieve 100% hydrogen combustion with low emissions is to prevent flashback. To address the challenges, a project consortium was set-up consisting of gas turbine equipment manufacturers, academia and end-users. The major objective is to develop a cost-effective, ultra-low emissions (sub 9 ppm NOx and CO) combustion system for gas turbines in the 1–300 MW output range, including the 1.85 MWe OPRA OP16 gas turbine.
At the center of this innovative high-technology project is the patented and novel aerodynamic trapped vortex FlameSheet™ combustion technology platform. Burner concepts based on an aerodynamically trapped vortex flame stabilization have a higher resistance towards flame blowout than conventional swirl stabilized burners. This paper will present the results of the first phase of the project, whereby atmospheric testing of the upgraded FlameSheet™ combustor has been performed operating on natural gas, hydrogen and mixtures thereof. The optimized combustor configurations demonstrated a wide load range on 100% hydrogen, and these results will be presented.
Mathematical Model to Describe Double Circular Arc and Multiple Circular Arc Compressor Blading Profiles
Authors: Kidikian John , Badrieh Chelesty , Reggio Marcelo 
Published: September 2021

Abstract
For the past seven decades, a compressor aerodynamicist has developed various methodologies to design, analyze, and simulate compressor stages. In compressor design, three major subsequent steps can be identified: the one-dimensional mean-line methodology, the two-dimensional through-flow analysis, and the three dimensional computational fluid dynamics.
One of the interconnecting threads, between these various x-dimensional analysis, is the compressor blade profile shape. This shape, of known and controllable geometric parameters, is usually accompanied by, or related to, loss models and known flow physics, either defined by theory or through experimental test.
In this paper, a novel mathematical approach is described to define axial compressor airfoil profile shapes. These shapes, developed in a Cartesian coordinate system, can be used to create Double Circular Arc, Multiple Circular Arc, and a hybrid combination of the two types.
The proposed methodology, based on the mathematics of circles, can be easily applied using generalized software such as Python or MATLAB, or be embedded in specialized engineering design software. In doing so, researchers and engineers can create compressor airfoil shapes which are consistent and flexible with respect to geometric parameter manipulation. Full details of the formulas, with respect to the camber line definition and the calculation of the profile intrados and extrados, are presented. A URL link to an equivalent MATLAB code, and a specialized engineering software, has been provided for those researchers that wish to apply the formulations and review its use.
Thrust Force Measurements in an Axial Steam Turbine Test Rig: Effect of Disk Balance Holes
Authors: Narzary Diganta , Stasenko David , Rao Nikhil 
Published: September 2021

Abstract
A full-size, full-speed, axial flow steam turbine test rig capable of measuring turbine thrust, and static pressures in the rotor-stator disk cavity was built and commissioned. The test rig was operated in a single-stage configuration for the test results first reported in Stasenko et al. [1], and now in this paper. The stage has stationary axial face seals radially inward of the airfoils, near the rotor disk rim. The face seals divide the rotor-stator cavity into inner and outer circumferential cavities, both of which were instrumented with static pressure probes on the stator radial wall. Axial thrust was measured with load cells in every thrust bearing pad.
The test rig was operated over a range of three nominal stage pressure ratios (designated as LPR, MPR, and HPR), five nominal stage velocity ratios (0.25–0.6), and five admission fractions (0.38–0.88). This latest group of tests was conducted without rotor disk balance holes, which were mechanically plugged, and will be compared to the original block of tests with disk balance holes opened.
In the upstream disk cavity, the two disk balance hole configurations shared many similar pressure characteristics: nearly uniform pressures in the inner cavity, circumferential pressure distributions in the outer cavity that corresponded with the direction of axial thrust, and radial pressure distributions in the outer cavity that were a direct function of rotor speed.
General trends of thrust coefficients with the disk holes plugged were correlated to stage pressure ratio, stage velocity ratio, admission fraction, and leakage mass flow rate. Those trends were consistent with the first block of tests with open disk balance holes, although there was an offset toward more operating conditions with negative aggregate thrust coefficients. This suggests that the rotating disk induces a low-pressure gradient in the inner (upstream) cavity, and the opened disk balance holes tend to equalize the inner cavity static pressure toward the higher static pressure on the exit side of the disk.
Additionally, thrust coefficients tended to become less negative (or more positive) with stage pressure ratio and with velocity ratio, but tended to become more negative with admission fraction. Significant thrust coefficient reductions were realized with the open disk balance hole configuration, and were determined to be consistently speed-dependent.
Unit Health Assessment- Oil & Gas Equipment Probabilistic Case Study
Authors: Mohamat Nor Noor Azman , Findlay Andrew 
Published: September 2021

Abstract
The focus of this case study is the analysis of offshore Oil & Gas facilities recorded downtime data which are classified into gas turbine downtime categories and causes. Each event is then correlated with the maintenance repair records to determine the respective root cause. The key objective of this study is to establish the Critical Success Factors (CSF) for unit health after a gas turbine has been in operation for more than 10 years. The outcome is used to enhance the unit performance, efficiency, maintainability, and operability. As a first step, Content Analysis technique was employed to systematically decipher and organize the downtime causes from collected data. Over 500 data samples collected over a period of 3 years were sorted into relevant categories and causes: comprising a total downtime of 11,410 hours. The downtime data, which is interval scale in nature that is in ‘hours’, is meticulously tabulated against respective downtime categories and causes location by location for the 11 gas turbines sites and correlating this to the repair work. Within scope is downtime related to: Forced Outage Automatic Trip; Failure to Start; Forced Outage Manual Shutdown; and Maintenance Unscheduled while those out of scope are Non-Curtailing and Reserve Shutdown as these are external to gas turbine operational influence. In the second step, descriptive statistics analysis was carried out to understand the key downtime drivers by categories. Pattern recognition is used to identify whether the cause is a “One Time Event”, “Random Event” or “Recurring Event” to confirm data integrity and establish the problem statement. This approach assists in the discovery of erroneous data that could mislead the outcome of statistical analysis. Pattern recognition through data stratification and clustering classifies issue impact as reliability or availability. Simplistic analyses can miss major customer impact issues such as: frequent small shutdowns that do not accumulate a lot of hours per event but cause operational disruption; or infrequent time consuming events resulting from a lack of trained personnel, spares shortages, and difficulty in troubleshooting. In the third step, statistical correlation analysis was applied to establish the relationship between gas turbine downtime and repair works in determining the root causes. Benchmarking these analyses outcome with the actual equipment landscape provides for high probability root cause, thus facilitating solutions for improved site reliability and availability. The study identified CSF in the following areas: personnel training and competency; correct maintenance philosophy and its execution in practice; and life cycle management including obsolescence and spares management. Near term recommendations on changes to site operations or equipment based on OEM guidelines and current available best practices are summarized for each site analyzed.
Parametric Optimization of Film Cooling Hole Geometry
Authors: Jones Fraser B. , Fox Dale W. , Oliver Todd , Bogard David G. 
Published: September 2021

Abstract
In this study, a combination of computational simulation and experimental testing was used to evaluate a broad range of forward and lateral expansion angles for a turbine film cooling shaped holes. The study demonstrates the utilizing of RANS based CFD to quickly screen potential optimized geometries, followed by experimental determination of true performance characteristics. As a baseline, the performance of all film cooling holes was evaluated using an internal coolant channel cross-flow. Also, all hole geometries incorporated a filleted inlet-plenum interface, which presumes use of additive manufacturing to construct the turbine components. Experimental validation confirmed that the computational simulations predicted the correct relative performance of various hole geometries, even though actual performance levels were not predicted well. This investigation showed that the performance of laidback, fan shaped holes was much more sensitive to the lateral expansion angle than the forward expansion angle. The optimum shaped hole configuration was found to be a hole with a 15° lateral expansion angle and a 1° forward expansion angle (15-15-1 configuration), which had a maximum average adiabatic effectiveness 40% greater than the baseline 7-7-7 open literature hole. This study also showed that the shaped hole diffuser performance is primarily a function only three parameters: the coolant jet velocity ratio, VR, the shaped hole area ratio, AR, and the hole exit width relative to the pitch between holes, t/P.
Numerical Investigation of Unsteady Combustor Turbine Interaction For Flexible Power Generation
Authors: Lo Presti Federico , Sembritzky Marwick , Winhart Benjamin , Post Pascal , di Mare Francesca , Wiedermann Alexander , Greving Johannes , Krewinkel Robert 
Published: September 2021

Abstract
With the growing importance of regenerative power generation and especially of a hydrogen-based economy, the full potential of gas turbines of the smaller output class (&lt; 10 MW) can be ideally exploited to provide peak coverage of the energy need whilst stabilising the electric grids in the mid- and low-voltage range. Such machines can be typically started in a relatively short time (similarly to aero engines) and are capable, at the same time, of delivering dispatchable power-on-demand.
A safe, stable and profitable operation under highly unsteady conditions poses renewed challenges for an optimal thermal management (especially in the HP stages) as well as control and surveillance of the machines. The understanding and hence predictability of the propagation of the temperature inhomogeneities originating at the combustor outlet remains hence a primary objective of current research, as persistent distortion patterns could be adopted at the turbine exhaust as diagnostic indications of a malfunction of the combustor, for example.
In the present study low-frequency disturbances introduced by a periodic load variation have been simulated and superimposed to the inhomogeneous, unsteady flow entering a 3-stage, high-pressure industrial gas turbine fed by a can-type combustion chamber comprising 6 silo-burners. The effects of the unsteadiness realized at the combustor exit have been investigated by means of Detached Eddy Simulations, whereby a density-based solution approach with detailed thermodynamics has been employed. The periodic disturbances at the turbine inlet have been obtained by means of an artificially generated, unsteady field, resulting from a two-dimensional snapshot of the flow field at the combustor exit. Also, a combustor failure has been mimicked by reducing (respectively increasing) the mean temperature in some of the turbine inlet regions corresponding to the outlet of two burners. The propagation and amplitude changes of temperature fluctuations have been analyzed in the frequency domain. Tracking of the temperature fluctuations’ maxima at the lowest frequencies revealed characteristic migration patterns indicating that the corresponding fluctuations persist with a non-negligible amplitude up to the last rows. A distinct footprint could also be observed at the same locations when a combustor failure was simulated, showing that, in principle, the early detection of combustor failures is indeed possible.
Jet Impingement Heat Transfer in a Rectangular Channel With Smooth and Pinned Target Walls
Authors: Alzahrani Yasser S. , Wright Lesley M. , Chen Andrew , Han Je-Chin 
Published: September 2021

Abstract
An experimental study was completed to quantify heat transfer enhancement, pressure loss, and crossflow effect within a channel of inline impinging jets. The jet diameter is 5.08 mm and the jet-to-jet spacing in the streamwise and spanwise directions is fixed at x/d = 11.1 and y/d = 5.9, respectively. The effect of jet-to-target surface spacing was considered with z/d = 3 and 6. For both of the jet-to-target surface spacings, a smooth surface, the reference case, and a surface roughened with partial height pins were investigated. The roughened surface has a staggered array of 120 partial height copper pin fins. The pin to jet diameter and the pin height to diameter ratios are D/d = 0.94 and H/D = 1.6, respectively. Regionally averaged heat transfer coefficient distributions were measured on the target surface, and these distributions were coupled with pressure measurements through the array. The heat transfer augmentation and pressure penalty were investigated over a range of jet Reynolds numbers (10K–70K). The results show high discharge coefficients for all the cases. The channels with the tight jet-to-target surface spacing experience double the cross-flow effect of its increased spacing counterpart. The addition of surface roughness showed a negligible effect on the crossflow. The best heat transfer performance was observed in the impingement channel with the pinned target surface at z/d = 3.
Operation and Control of a Supercritical CO2 Compressor
Authors: Neveu Joshua D. , Cich Stefan D. , Moore J. Jeffrey , Mortzheim Jason 
Published: September 2021

Abstract
Among the list of advanced technologies required to support the energy industry’s novel Supercritical Carbon Dioxide (sCO2) power cycle is the need for a robust and responsive control system. Recent testing has been performed on a 2.5 MWe sCO2 compressor operating near the critical temperature (31C) and critical pressure (73.8 bar), developed with funding from the US DOE Apollo program and industry partners. While sCO2 compression has been performed before, operating near the critical point has many key benefits for power generation with its low head requirements and smaller physical footprint. However, with these benefits come unique challenges, namely controlling this system to steady-state operating conditions. Operating just above the critical point (35°C [95°F] and 8.5 MPa [1,233 psi]) there can be large and rapid swings in density produced by subtle changes in temperature, leading to increased difficulty in maintaining adequate control of the compressor system. This means that proper functionality of the entire compressor system, and its usefulness to a closed loop recompression Brayton power cycle, is largely dependent on variables such as thermal sources, precision and response time of the instrumentation, proper heat soaking, and strategic filling and venting sequences. While other papers have discussed the science behind and performance of sCO2 compressors, this paper will discuss the challenges associated with steady-state control of the compressor at or near operating conditions, how the fill process was executed for optimal startup, and changes that occurred while idling during trip events.