bluuebunny/crossref_metadata_2025_split huggingface dataset:
Techno-Economic Performance of the Allam-Fetvedt Cycle With Oxygen Storage
Authors: Pryor Owen , Moore J. Jeffrey , Cormier Ian , Fetvedt Jeremy , Burlaka Maksym , Goldenberg Vlad 
Published: September 2023

Abstract
A model was developed to predict the operation and performance for liquid oxygen storage coupled with the Allam-Fetvedt Cycle (AFC), a direct-fired supercritical carbon dioxide cycle. The cycle uses liquid oxygen to time-shift the major parasitic of the cycle, the air separation unit (ASU), to minimize the economic costs of air separation. This paper presents significant improvements to the model and the techno-economic analysis in the forms of improvements to the assumptions, an exploration of different ASU architectures, potential improvements to the AFC for coupling with liquid oxygen and a sensitivity study on the impact of variables on performance. Several assumptions were updated or added to improve the accuracy of the system. These include adding utilities such as water requirements or fuel usage during ASU operation. In addition, an aerodynamic analysis on three different architectures for the main air compressor (MAC) were compared focusing on the performance at both full load and part load. It was determined that the best architecture for the MAC depended on the underlying economic market. An integrally-geared compressor performed the best in markets with high renewable penetration and frequent short-term cycling due to the improved part load performance. For markets with more seasonal trends, the more efficient axial-radial architectures performed better. In addition to improvements to the charge system, several different modifications were explored to improve the AFC. The first was to use the CO2 stream to vaporize the liquid oxygen, reducing the inlet temperature of the CO2 entering the compressor. Another was to pump the oxygen and CO2 separately to full pressure before mixing the oxidant streams. The potential technology improvements resulted in additional power output of the system that improved the net present value overall. All of the results were compared to each other in a sensitivity analysis that compared how 8 different parameters affected the results for different markets.
Advanced Turbine Efficiency Package (ATEP) Upgrade for The SGT5-4000F Service Fleet
Authors: Vogel Tobias , Kunte Robert , Tertilt Marc , Timmermann Julian , Mihalyovics Jan , Beiler Jan-Dirk 
Published: September 2023

Abstract
Affordability, reliability, and sustainability are the core properties for power generation towards a new energy system. Therefore, our Siemens Energy gas turbine technologies and our large operating service fleet are the backbone of our business. Siemens Energy, as Original Equipment Manufacturer (OEM), has developed the Advanced Turbine Efficiency Package (ATEP) to support the competitiveness of our SGT5-4000F gas turbines. The improvement of the combined cycle power output and efficiency helps to optimize fuel costs at constant power output to decarbonize existing assets and offers additional peak power in case of high electricity demand in fluctuating grids.
The ATEP turbine blades and vanes were developed based on a multi-point and multi-discipline optimization of the turbine section using the latest HL-class design tools and features from the Siemens Energy design chain. Since the ATEP upgrade is focusing on the existing fleet, the entire design process chain considered the constraints and limitations of the related SGT5-4000F customer assets. Thus, the ability to retrofit into service customer assets was ensured, while enabling remarkable performance benefits.
This paper describes the technical details of the ATEP upgrade, the underlying design approach, and summarizes the First Time Application (FTA) that was conducted in 2022 at the Enecogen 10 power plant in the Netherlands. Along with the related product verification and applied testing methods. In the results section, the testing results from the FTA are compared with the predicted Computational Fluid Dynamics (CFD) and Conjugated Heat Transfer (CHT) design values. Furthermore, the key performance parameters, power output and efficiency, are presented and classified via a comparison to appropriate baselines. Hereby, the ATEP upgrade’s capability for increasing gas turbine power output and efficiency was demonstrated within the FTA. Resulting in combined cycle application benefits of up to 40 MW additional power output and 1.5 %-pts efficiency increase. Through efficiency improvement ATEP upgrade is supporting asset decarbonization, while providing notable supplementary commercial benefits.
Axial Compressor Transonic Rotor Shock Interaction With Upstream Stator Row
Authors: Koyyalamudi V. V. N. K. Satish , Burberi Corrado , Lorusso Salvatore , Michelassi Vittorio , Scotti Del Greco Alberto 
Published: September 2023

Abstract
Modern high-performance multistage axial compressors are designed for high aerodynamic loading and efficiency, wide range and operate front stages with rotor inlet relative Mach number above one over a large portion of span. Understanding unsteady flow phenomena and rotor-stator interactions is paramount in the design of front stages. With increased aerodynamic loading, rotor shock waves may propagate upstream and interact with stator vanes. Such interaction may affect both performance and aeromechanics as shock propagation and reflection may destabilize boundary layers leading to higher aerodynamic losses and unsteady pressure pulsations. Unsteady numerical simulations prove to be necessary to predict and minimize the impact of rotor to upstream stator shock interactions. This paper discusses rotor-stator shock interactions using unsteady numerical simulations. The computations are performed on three stage designs, under the constraint of same capacity and total pressure ratio but differ in axial gap and load distribution in stator and rotor. Speedlines from steady and unsteady computations compare the different designs, and the detailed flow fields are analyzed at design and close to stall conditions. The analysis reveals the importance of relative orientation of shocks generated in the rotor row with the upstream stator camber line, while steady simulations predict a different stator-rotor loss split. This orientation affects the intensity of the shock boundary layer interactions and the shock reflections as well as compressor performance. The comparison of the designs suggests possible ways to mitigate the growth of shock-driven losses.
Influence of Casing Roughness on the Tip-Leakage Loss in a Linear Turbine Cascade
Authors: Huser Lukas , aus der Wiesche Stefan , Schatz Markus 
Published: September 2023

Abstract
The present experimental study was intended to investigate the impact of casing roughness on the tip leakage flow and the loss in a linear turbine cascade. Detailed flow measurements utilizing a five-hole probe, namely the so-called Oxford probe, and a miniaturized Pitot probe were made upstream and downstream of a row of steam turbine blades with variable tip gaps and different levels of casing roughness. It was found that casing roughness affects the position of the tip-leakage vortex in the linear cascade, but it does not reduce its loss contribution. An increase in the total loss was observed, which could be attributed to a rise in the secondary loss due to roughness. This result indicates that potential loss-reduction mechanism might be caused by the relative motion of the blade tip surface and the rough casing wall or by vortex interactions.
Preliminary Investigation of a Combined Heat and Power Reversible-Brayton System Integrated With a Renewable Power Source
Authors: Ancona Maria Alessandra , Bianchi Michele , Branchini Lisa , De Pascale Andrea , Melino Francesco , Ottaviano Saverio , Peretto Antonio , Poletto Chiara 
Published: September 2023

Abstract
Pumped Thermal Electricity Storage (PTES) technology is drawing increasing attention as a promising solution to limit the mismatch between the electric demand and the renewable production.
In this context, a preliminary model of a reversible Brayton PTES is developed on a commercial software to finalize a comprehensive performance investigation. In the proposed arrangement, the system allows to store the surplus of electric renewable production, by converting it into heat, through an inverse cycle, and then to convert it back into electric energy when needed, through a direct cycle. A systematic analysis comparing two configurations (base and recuperated) of the reversible Brayton system is carried out to assess the performance of the system.
Since thermal and electric energy flows are involved, PTES is particularly interesting when adopted to satisfy both thermal and electric demands, in a combined heat and power (CHP) system. To this aim, the system has been simulated when delivering both thermal and electric energy, in different partitioning. Results show that if 25 % of the stored heat is addressed to a thermal user the integrated system can be convenient in terms of saved primary energy, compared to conventional separate production. In case 70 % of the stored heat is delivered to a thermal user and 30 % reconverted into electricity, the maximum investment cost to have a return of the investment in 10 years is assessed to be between 2000 and 5000 €/kW, depending on the configuration.
A Novel Optimisation of a Transonic Centrifugal Impeller Based on 3D Inverse Design Approach
Authors: Wang Peng , Zhang Mingding , Zangeneh Mehrdad 
Published: September 2023

Abstract
A key step in optimising a centrifugal impeller is the parametrisation of the blade profile, which could easily call for many control parameters to define the profile with high-enough resolution and smoothness. As the number of parameters increases, the complexity of optimisation is amplified drastically, resulting in skyrocketing demand for computational resources and time. For the industry, rather than the design methods and guidelines, which are available in a number of good textbooks, it is the accurate yet fast and affordable optimisation for product development aiming to achieve multiple operating points that still remain an onerous task. In this paper, a novel design and optimisation strategy coupling the 3D inverse approach and DoE (design of experiment) study is developed, and it has been used for the redesign and optimisation of a well-known transonic centrifugal compressor. CFD analysis confirmed that the redesigned compressor wheel has increased the efficiency over the entire performance map significantly, and the detailed internal flow visualisation shows that the reduction of leaking loss is the main contributor to this improvement. The cost of CFD times is only within several days on a 32-core computer rather than weeks. The approach used in this work can be extended to different machine types.
A New RANS Based Reynolds Stress and Turbulent Heat Flux Treatment and Challenges in Predictions of Mixed Convection Type of Flows
Authors: Murat Oguzhan , Rosic Budimir 
Published: September 2023

Abstract
RANS based turbulence models are still gold standard in industry despite their limitations. Traditionally, the development of turbulence models for heat transfer problems is driven by applications with either natural or forced convection dominated flows. Surprisingly, far too little attention has been paid to mixed convection problems with various buoyancy domination in the literature despite its importance for variety of engineering problems. Mixed type of flows exhibit complex flow interactions between buoyancy induced flows and inertial forces. The commonly used linear eddy viscosity and diffusivity models fail to reconstruct the Reynolds stress and turbulent flux profiles, which are mainly responsible for inaccurate heat transfer predictions, and suffer from severe convergence difficulties. Turbine casing cavity flows during different shut-down regimes, which are characterised by a wide range of mixed convection flows, are used as a platform for the development of a novel physics-based universal model to be used within RANS concept for mixed type of flows, which is presented in this paper. The model incorporates and blends a constitutive relation for Reynolds stress and a new generalised gradient diffusion hypothesis for turbulent heat fluxes. The new model, New Nonlinear RANS (NNR), has been developed to overcome the convergence difficulties with conventional RANS and to improve heat transfer predictions without having to solve any additional transport equation.
Roughness Related to Cooling Performance of Channels Made Through Additive Manufacturing
Authors: Wildgoose Alexander J. , Thole Karen A. , Tuneskog Erika , Wang Lieke 
Published: September 2023

Abstract
The complex surface morphology and multiscale surface features inherent with additively manufactured (AM) components contributes to the overall flow characteristics and heat transfer of cooling passages. As the AM process and cooling data in literature continues to evolve, so does the need for more accurate heat transfer and pressure loss correlations for AM cooling schemes. This study improves the predictability of pressure loss and heat transfer for AM cooling passages by fabricating a range of coupons and investigating samples in literature. Twenty-seven test coupons were manufactured using direct metal laser sintering in an assortment of build directions and build locations that produced a variety of surface morphologies. Nondestructive evaluation, computed tomography scanning, was used to quantify the surface morphology as well as capture the as-built geometric dimensions of the cooling schemes. Friction factor and bulk Nusselt number of the coupons were measured using an experimental rig. Pressure loss and heat transfer correlations in literature were compared with the experimental results from the current coupons and datasets from literature. Arithmetic mean roughness correlations in literature struggled to predict the cooling performance of AM channels since the bulk roughness statistic did not capture the overall form of the surface morphology. A combination of root mean square roughness and skewness of the roughness was able to best predict pressure loss and heat transfer for the present samples and those in literature while being independent of build location, build direction, material, machine, and laser parameters. The maximum absolute error was 25% and average absolute error was 12% for the friction factor correlation. The maximum absolute error was 39% and average absolute error was 8% for the Nusselt Number correlation.
Measurement of Temperature and Load vs. Bearing Displacement in a Thrust Foil Bearing: Differences Between Light Load and High Load Operation
Authors: San Andrés Luis , Duran-Castillo Azael , de Santiago Oscar , Jauregui Juan , Lubell Daniel 
Published: September 2023

Abstract
This paper presents a revamped test rig for the evaluation of gas thrust foil bearings (GTFB) and details measurements of load capacity conducted with a commercial GTFB having inner and outer diameters equal to 35.6 mm and 71 mm, respectively. The test GTFB comprises a single 360°, 0.127 mm thick top foil divided into six continuous arc segments with a formed taper of 0.102 mm. The top foil rests on a stack of shims that contact on the outer ring, and position the top foil above the underspring an optimized amount. Six anvils in one of the shims engage the top foil axially. Underneath the shims there are six underspring structures, each comprising three strips of bump foils. The number of bumps differs along the radial direction. Made of an application-appropriate stainless steel, the spring is 0.102 mm thick. All the foil components making the GTFB have a combined thickness of 0.737 mm. The top foil is coated with a Teflon® layer. Measurements include the applied static load and ensuing break-away torque, rotor speed, GTFB axial displacements at three locations 120° apart, the flow of a cooling stream of supplied air, and bearing temperatures in and out of the bearing. Static load tests produce the underspring structure deformation and a dry-sliding friction coefficient f∼0.12. The underspring is rather flexible though quickly hardening for specific load (P*) &gt; 25 kN/m2 to reach an ultimate structure deformation of ∼ 0.320 mm. Measurements at 30 krpm (OD surface speed = 111 m/s) obtained for increasing static loads produce GTFB displacements that parallel the displacements recorded without shaft rotation. Most importantly, the difference between displacements approaches ∼0.060 mm for P* &gt; 45 kN/m2. The test GTFB operated safely to a unit load (P*) = 90 kN/m2 and failed at P* = 120 kN/m2. When heavily loaded, the GTFB is significantly stiffer than when lightly loaded. Designed for easiness of installation and operation, the test GTFB demonstrated a stable and repeatable performance with likely a uniform gap or film thickness even for the largest loads applied.
Development of Multiphase Computational Fluid Dynamics Simulation for Predicting Last Stage Low Pressure Steam Turbine Blade Water Droplet Erosion
Authors: Landrum Evan , Wu Zhilei , Kulkarni Anand , Musch Christian 
Published: September 2023

Abstract
Water droplet erosion has emerged as a reliability concern in steam turbines, resulting from exhaust flow recirculation in combination with the presence of down-stream moisture. Last-stage blades in Low-Pressure (LP) steam turbines interact with water spray systems in the condenser housing, which leads to blade trailing edge erosion. Such erosion can result in unplanned service outages, costly repairs or even blade liberation. It is for this reason that a computational fluid dynamics (CFD) model was developed to predict water droplet erosion for the last stage low pressure turbine blade in certain axial flow turbine configurations. In this study, Lagrangian multiphase physics were employed in a control volume representing an LP turbine configuration with an axial exhaust diffuser and short-coupled water-cooled condensers. Four critical, part load operating points were investigated which enable the conditions required for turbine water droplet erosion including active water spray systems and diffuser recirculation. First, a gaseous steam flow field is established, and then discrete particles representing water droplets are injected into the continuum. Particles are tracked as they redistribute throughout the domain, collide and breakup with boundary walls. An erosion wear model was implemented on blade surfaces of interest which included the influences of wall material, impact speed and incidence angle.
Blade surface erosion rate distribution and surface integrated erosion rates were calculated for each case. Qualitative comparisons have been made between blade impact erosion observed in the field and CFD simulations. Mitigation solutions to reduce blade erosion were also studied for relative change.
Performance Improvement of Savonius-Type Hydrokinetic Turbine With Bucket Airfoil Profile
Authors: Osama Shehab , Emam Mohamed , Ookawara Shinichi , Ahmed Mahmoud 
Published: September 2023

Abstract
A new design to enhance the output power of a Savonius hydrokinetic turbine by using buckets with airfoil profile instead of a conventional semi-circular design is developed. Effects of different camber angles of buckets’ airfoil at 105°, 120°, 130°, and 140° are investigated and compared with the conventional profile. In addition, the influence of varying the buckets’ camber position of the airfoil is considered to determine the camber angle at the maximum output power. Accordingly, a two-dimensional, unsteady incompressible turbulent flow model is developed and numerically simulated. The predicted results from the simulations are validated using available measurements. Results show that a significant enhancement of maximum output power is obtained using the airfoil profile at all studied camber angles compared to the traditional Savonius turbine with a semicircular profile. Furthermore, using a camber angle of 140° attains the highest output power compared to other designs. At a water current speed of 0.4 m/s, and the overlap ratio of 0.15, the maximum power coefficient is 0.193. However, for the conventional design with a semi-circular profile, the maximum attainable power coefficient is 0.1 at the same operating conditions. The current findings provide an alternate direction in utilizing Savonius turbines with bucket airfoil profiles.
Ultra High Efficient Power Generation With SOFC-Gas Turbine Systems: Different Options for 80%+ Efficiency Power Cycles
Authors: Alpegiani Francesco , Zelaschi Andrea , Cammarata Alberto , Chiesa Paolo , Campanari Stefano , Martelli Emanuele 
Published: September 2023

Abstract
This work aims to design and simulate an ultra-high-efficient triple combined cycle for large-scale power generation, integrating an intermediate temperature Solid Oxide Fuel Cell (SOFC) with a gas turbine and a bottoming steam cycle. The power plant implements a large cathodic recirculation to preheat the air flow, while the inlet anodic stream is preheated by using steam produced in the heat recovery steam generator and anodic recirculation. System simulations are performed by using GS, a software developed and validated by Politecnico di Milano. State-of-the-art parameters are used for the SOFC, the H-class gas turbine and the steam cycle. Moreover, in order to identify the operating conditions that maximize the efficiency, a sensitivity analysis is performed on the compression ratio, the secondary fuel mass flow rate, the single-pass utilization factor and the cell voltage. The results show that the triple combined cycle may achieve an outstanding net electric efficiency of 84.4% (LHV basis). The sensitivity analysis indicates that adding secondary fuel to a supplementary burner ahead the gas turbine tends to decrease the system efficiency, while also adopting relatively low SOFC voltages (0.775V) or single-pass utilization factors (70%) it is possible to maintain the efficiency above 80%.
Modeling Flame Transfer Functions of an Industrial Premixed Burner
Authors: John Tony , Magina Nicholas , Han Fei , Kaufmann Jan , Vogel Manuel , Sattelmayer Thomas 
Published: September 2023

Abstract
This paper presents an analysis of the unsteady heat release rate response of industrially relevant axisymmetric premixed flames to harmonic velocity perturbations. The heat release rate response, quantified using the Flame Transfer Function (FTF) definition, is measured from an acoustically forced swirl burner under perfectly premixed conditions. To understand the features of the measured FTF, a physics based analytical model is developed in this study. To describe the heat release rate dynamics, a model for the flame spatiotemporal response is derived in the linear limit using the G-equation formulation. Inputs to the flame response model are selected to be consistent with values observed in the corresponding industrial burner, based on experimental and numerical studies. The relative contributions of acoustic and convecting vortical disturbances on specific features of the FTF are explored in this study. The results highlight the importance of capturing the appropriate disturbance velocity field as an input to the flame response model for accurate FTF predictions.