bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Evaluation of Integrated Thermal Energy Storage Concept for the Recuperated Gas Turbine Application
Authors: Flores Garcia Juan Diego , Harun Nor Farida , Traverso Luis M. , Zhou Nana , Tucker David 
Published: September 2023

Abstract
Increasing thermal energy storage (TES) installation across countries is anticipated to enable greater adoption of distributed energy systems to meet the Net Zero Emission goals by 2050. Emerging TES technologies have been widely considered as a key component to support transition towards carbon neutrality as well as to secure grid stability for more flexible, reliable, and efficient energy systems. Integrating a sensible thermal energy storage in an existing energy cycle can be a feasible solution to enhance system flexibility for following fluctuations in power demand and supply. This research investigates the ability of a recuperated gas turbine cycle to reduce carbon emissions and optimize the system efficiency during load following with a thermal energy storage. This cycle was selected due to its reconfigurability for integration of renewable energy resources for thermal sources and sinks. To first demonstrate the concept and identify the key performance requirements, dynamic performance tests were conducted using hardware-based facility at the U.S Department of Energy, National Energy Technology Laboratory. A new control strategy using a hot air bypass valve to control the discharging and charging states was proposed. The sensible heat medium (i.e., air mass flow) entering the thermal energy storage was modulated through opening and closing hot air bypass simulating the cycle has excess energy or requires energy. It was observed that the thermal energy storage has a maximum heat dissipation of 103 kW. This latent heat represents 57% of the electric load capacity of the turbomachinery, assuming a 33% efficiency heat to electricity. The thermal energy storage was able to maintain heat dissipation for 4 minutes. Load following is possible since the change in dissipation rates over one second are double of what is achievable with a fuel valve. Some optimizations to the surface area to mass ratio are needed to maximize the integrated cycle.
Design of an Innovative Experimental Rig for the Study of Deposition Phenomena in Axial Compressors
Authors: Suman Alessio , Zanini Nicola , Pinelli Michele 
Published: September 2023

Abstract
Compressor fouling is one of the main causes of gas turbine performance degradation. Fouling is promoted by micrometric particles of industrial pollutants in the air and unfavorable environmental conditions (fog, rain, humidity). Airborne particles ingested in heavy-duty gas turbines deposit on the compressor blades and sidewalls, increasing the surface roughness and changing the shape of the profile. This work aims to design a subsonic wind tunnel to study the gas turbine fouling phenomenon. Lump-parameter analysis and two- and three-dimensional fluid dynamics simulations support the design. Simulations were needed to optimize the blade cascade and identify particular fluid dynamic phenomena, such as separation, stagnation point, and vortex. In addition, great attention was devoted to the thermo-hygrometric conditions responsible for the capillarity forces. All these factors strongly influence the compressor cascade performance and the contamination rate. Particle concentration, number, and size are specified to perform a quantitative analysis of the particle impact on the blade surface and a qualitative analysis of the impact zones. As a result, realistic impact conditions of industrial relevance are reproduced in the wind tunnel in order to forecast the adhesion rate, the areas of the compressor airfoils impacted by particles, and thus the performance losses over the operation.
Numerical Analysis of a Shrouded Centrifugal Compressor for Use in Supercritical Carbon Dioxide (s-CO2) Brayton Cycle
Authors: Fenil Arockia , Seshadri Lakshminarayanan , Kumar Pramod , Nassar Abdul , Giri Gaurav 
Published: September 2023

Abstract
This paper presents the work that entails the design and analysis of a sub megawatt s-CO2 centrifugal compressor. The compressor is intended to be part of a 20 kWe sCO2 Brayton cycle test facility at Indian Institute of Science (IISc) which presently uses a reciprocating compressor. The cycle operates at a maximum temperature of 773K with a flow rate of 45 kg/min and the compressor that feeds the loop must operate between pressures of 21 MPa and 9 MPa whilst rotating at 40000 RPM. The compressor comprising of rotor, vaned diffuser and volute is designed using the AxSTREAM® software suite and is verified numerically using the commercial CFD software ANSYS CFX. Since, initial testing of the compressor will be performed with air, simulations are performed with air as well. A comparison of the flow field revealed that the flow structure in the rotor remains similar at design condition while significant deviation is observed with the vaned diffuser.
Analytical and Numerical Study for the Reduction of Shock Waves in Supersonic Stators Through Trailing Edge Modifications
Authors: Martínez-Alvarado Luis Enrique 
Published: September 2023

Abstract
This paper introduces a method to reduce total pressure losses due to shock wave generation across a supersonic stator by modifying its trailing edge shape. Indeed, it aims at controlling the shape and strength of the generated shock waves to reduce their impact on a full stage supersonic turbine performance. Several approaches were proposed and evaluated using 2D CFD periodic inviscid computations with SU2 solver focusing on the shape, thickness, and deflection of the stator’s trailing edge. The chosen approach is based on a horizontal plate that represents the trailing edge of the stator blade. Shock wave generation was then analyzed following different cases of trailing edge geometries. This analysis has led to the identification of the best-case trailing edge geometry which reduces the number of shock waves generated, their intensity and their interaction between each other. An analytical analysis of the shock wave generation exiting the blade trailing edge was also performed. This analysis introduces the limitations of the maximum blade deflection angle from where reflected shock waves interaction from adjacent blades start to develop. These limitations are presented as a function of Mach number and cutting angle at the trailing edge. The analysis has contributed to the understanding of the shock wave generation in a supersonic stator cascade. Additionally, a simplified method for the predesign of supersonic blades with reduction shock wave generation was completed.
Exploring Physics of Acoustic Flow Control Over Airfoils Towards Potential Application to High Work and Lift Turbines
Authors: Celik Acar , Mitra Abhijit , Agarwal Tapish , Clark John , Jacobi Ian , Cukurel Beni 
Published: September 2023

Abstract
In this study, acoustic actuation was applied experimentally to massively separated flows on simplified hump geometries which mimic the pressure distribution over high-work-and-lift low Reynolds airfoils. The acoustic excitation demonstrated significant control over flow separation, resulting in higher relative lift enhancement than standard, localized actuation techniques with similar momentum coefficients. Full field velocity measurements were used to examine the transient behavior of the actuated flow in order to explain the physical mechanism of separation control. The velocity measurements revealed the presence of a viscous wall-mode that organized the vorticity upstream of the separation point. A spatio-temporal correlation analysis found that the generation of these wall modes in the attached flow was the dominant cause of the subsequent reorganization of the separating shear layer and the change in separation dynamics. The importance of wall-modes to acoustic flow control mechanism has important implications for the design of new acoustic control strategies for high-speed turbomachinery. Along these lines, the ramifications of this phenomena are explored over geometries which are designed to approximate flow fields in high-speed turbomachinery. At the conducive Strouhal number, which scale linearly with the square root of Reynolds numbers, up to 22% lift enhancement is observed for excitation amplitudes in the range of ∼128dB, typical to the engine environment. Of the many diverse flow-control techniques, acoustics can be effectively employed in low Reynolds turbine blades, which are prone to flow separation in the off-design conditions with the ever-increasing demand for higher flow turning.
Pump-Turbine Development for Geomechanical Pumped Storage Facility
Authors: Patil Abhay , Wilkes Jason , Nielson Jordan , Hill Bunker 
Published: September 2023

Abstract
A significant effort is focused on developing cost-effective long-duration energy storage for integrating and expanding the use of renewable energy resources. Geo-mechanical pumped Storage (GPS) leverages the natural energy storage capability of subsurface formations to store water under pressure. The approach is in a way similar to oil and gas production with the potential to leverage an already established supply chain for drilling, reservoir formation, and production. However, with the proposed approach, the head and flow requirement to charge and discharge the subsurface reservoir changes, needing the pumps and turbines with high head flow conditions. The current study explores the design space for the development of turbines and pumps for GPS systems with a focus on expanding the pump as a Turbine option in line with the overall vision of achieving the lowest possible Levelized Cost of Storage Energy (LCOSE). Initial installations focus on two 1 MW systems (522.4 m3/hr and 1044 m3/hr). Design space includes single and multi-stage options at different rotational speeds to optimize the roundtrip efficiency and Net Positive Suction Head-requirements (NPSHr) for surface-installed equipment. Design iterations investigate the rotor-stator interactions, flow slip in reversible direction, and means to optimize the outlet performance to minimize the cavitation occurrence. The analysis lays out different configurations and concludes with the discussion about proposed design that outputs a round trip efficiency of 74% with a path to minimize manufacturing and assembly cost for different installations using modular configurations.
Reducing the Energy Penalty of Retrofit Decarbonization in Combined Cycle Power Plants
Authors: Ravelli Silvia 
Published: September 2023

Abstract
This study is a continuation of previous work aimed at elucidating the effect of hydrogen-cofiring and exhaust gas recirculation (EGR) on combined cycle (CC) performance. The thermodynamic analysis was expanded to include post-combustion capture (PCC) by means of mono-ethanolamine (MEA). Attention was paid to net power output and thermal efficiency.
Part-load operation of the CC without carbon capture was taken as reference. Decarbonization solutions, in ascending order of complexity, included the following: 1) adding a PCC unit; 2) combining EGR with PCC, so as to exploit the increase in the flue gas CO2 concentration while reducing the exhaust gas flow delivered to the absorber; 3) including hydrogen co-firing at the largest capability dictated by the gas turbine (GT) combustion system, with the opportunity to explore a wider range of EGR rates, while still relying on PCC of the residual CO2 in flue gas, before discharge into the environment.
Scenarios were firstly discussed under the same GT load for consistency with the published literature, thus enabling the validation of the modelling procedure. Then, CC net power production was assumed as the basis of comparison. The third solution was found to be the most promising thus minimizing both the energy penalty due to carbon capture and CO2 emission intensity (EI).
Performance Assessment of an Innovative Turbocharged Proton-Exchange Membrane Fuel Cell System
Authors: Iester Federico , Mantelli Luca , Bozzolo Michele , Magistri Loredana , Massardo Aristide Fausto 
Published: September 2023

Abstract
This paper presents an innovative turbocharged proton-exchange membrane fuel cell system (TC-PEMFC) fuelled by hydrogen. Their high efficiency and absence of pollutant emissions allowed interest in hydrogen-powered PEMFCs to grow constantly over the past few decades. Nowadays, both industry and academia consider PEMFCs as one of the most promising solutions to replace conventional fossil fuel plants and achieve decarbonization of the energy and transportation sectors.
The system proposed in this study further improves the performance of standalone PEMFCs (generally within the 60–40% range), using the pressurization of the fuel cells. Two separate stacks are operated in parallel and integrated with a turbocharger, which pressurizes the cathode air flows. Before being discharged into the ambient, the PEMFC outlet flow expands in the turbine, providing part of the mechanical power absorbed by the compressor and increasing the net power output of the plant. The remaining part is supplied by an electrical motor connected to the shaft of the turbocharger.
To guarantee the proper operation of the PEMFCs in terms of mass flows, pressures, temperatures, chemical compositions and humidity, the layout incorporates many auxiliary components. They include a polymeric membrane cross-flow humidifier on the cathode side, a gas-to-gas heat exchanger on the air loop, a side channel blower on the anode recirculation and a liquid cooling system for the stacks.
A dedicated control system was designed to keep all the operative parameters of the plant on the proper values. A proportional-integral-derivative controller and a set of look-up tables regulate the opening of fuel and bypass valves, as well as the rotational speed of turbocharger, cooling fluid pump and blower.
To fully understand the potential of this innovative solution, Rolls-Royce Solutions and Thermochemical Power Group (University of Genoa) developed a simulation model using GT-Power, a commercial software by Gamma Technologies Inc. The complete layout of the system was recreated within GT-Power relying on its extensive library of components. This is the first time a turbocharged PEMFC system was modelized including all the main balance of plant components and implementing the full control logics.
The model was used to simulate the TC-PEMFC system under different conditions, to monitor its operative parameters, and to compare its performance with a standalone PEMFC. The promising results obtained during this analysis confirm the potential of the turbocharged layout and open the way for even more sophisticated simulation studies and experimental activities.
Systematic Approach for Modelling Modern Turbofan Engines
Authors: Ramdin Shivan , Visser Wilfried , Regueiro Juan , Rootliep Tim 
Published: September 2023

Abstract
Turbofan engine technology has evolved over several decades resulting in highly efficient and reliable propulsion systems for commercial airliners. Maintenance costs have decreased, but still represent a major part of the overall aircraft operating costs. To further minimize these, engine maintenance needs to be planned timely and strategically. Advanced diagnostics and health monitoring methods are being developed at KLM Engine Services (ES) to improve engine maintenance. For health monitoring, gas path analysis is used which requires accurate engine performance models. The modelling task is complicated further by the reduced number of measured gas path parameters with modern turbofan engines. This paper presents a systematic approach to overcome these complications. An engine model usually comprises of a cycle reference point, representing a design point such as maximum take-off thrust. As a first step, a genetic algorithm is used to determine the set of unknown cycle reference point parameters and component efficiencies best matching a set of known engine measurement data. Additionally, physical relations were used as constraints to compensate for the missing data. Off-design performance is calculated by solving a set of non-linear algebraic equations which depend on the unknown component performance maps. The customary method of deriving the performance maps by scaling similar maps at the cycle reference point only, often suffers from large deviations at off-design conditions. Consequently, these ‘baseline’ maps require corrections across the entire operating envelope. In the second step of the method, genetic algorithms determine the best off-design performance estimations at multiple measured operating points by finding the optimal coefficients of polynomial scaling functions for map parameters such as efficiency, corrected pressure ratio and mass flow. The modelling method has been verified by developing CF6-80C2 and GEnx-1B turbofan engine models using test cell data. The GEnx-1B engine model has subsequently been validated using on-wing operating data. The largest validation error was attained at cruise flight conditions and was found to be equal to 3.9%. The resulting method provides a systematic way to deal with missing data and can be used for developing accurate engine models for better gas path analysis reliability, resulting in more effective engine maintenance.
Determination of Cetane Numbers via Chemical Kinetic Mechanism
Authors: Schmidt Marleen , Schlichting Samuel , Melder Jens , Methling Torsten , Köhler Markus , Huber Andreas 
Published: September 2023

Abstract
Minimizing global warming is a major task of todays’ society. For air transport, sustainable aviation fuels (SAF) produced from renewable sources are a promising key solution. While electric flight is intriguing for short distances, SAF are required for mid and long distance flights and in addition, enable fuel design strategies to minimise environmental effects. The qualification and approval for SAF is standardised in the ASTM D4054, which include fuel properties as an essential part. Among others, lean blow-out (LBO) limits are a key performance parameter. The experimental determination of LBO is very time and cost consuming. The LBO of a specified engine is highly dependent on the fuel properties affecting evaporation, mixing, and ignitability. Therefore, prediction tools are desired to identify early promising SAF for decreasing the certification cost. Due to the correlation between LBO and derived cetane numbers (DCN), a tool for the prediction of the DCN is presented in this study. The DCN-model uses chemical kinetic ignition delay time, simulated in a constant volume combustion chamber based on the ASTM D6890 standard, and seven representative physical properties of a fuel. A high agreement of the predicted DCN to the literature DCN with root mean square errors of 3.3 and correlation coefficients of 0.974 was found.
SGT5-4000F Hydrogen Capability – High Pressure Combustion Rig Tests
Authors: Blaette Lutz , Schmitz Udo , Streb Holger , Vogtmann Daniel 
Published: September 2023

Abstract
Gas turbines will play an important role in the future energy mix with a growing but volatile share of renewable energy sources, because of both their unique grid stabilization capabilities and the ability to burn hydrogen or other green fuels. The hydrogen capability of the Siemens Energy heavy duty gas turbine SGT5-4000F is currently investigated and extended. The first engine was introduced in 1997, the fleet consists of more than 360 units in operation today with ∼23Mio accumulated operating hours. The desired reduction of the fleets CO2-footprint cannot be achieved solely by efficiency enhancements, but also requires the ability to operate on fuel gas mixtures of natural gas and hydrogen. Likely scenarios foresee hydrogen contents in the fuel gas of up to 30%vol in the near future and mid-term operation in the range of 30%vol to &gt; 50%vol H2. This appears to be feasible with the existing SGT5-4000F combustion architecture.
Combustion tests with hydrogen mixtures with varying H2 content have been performed at the Siemens Energy Clean Energy center (CEC) under realistic thermodynamic boundary conditions in a single burner high pressure test rig. The relevant burner variants operating in the fleet as well as burner upgrades have been tested on their maximum H2 capability with regards to combustion dynamics, overheating/ flashback and NOx emissions.
This paper provides an overview of the test results, gives an outlook on the resulting anticipated hydrogen capabilities of the SGT5-4000F fleet and outlines the next steps in the SGT5-4000F hydrogen program.
Physics-Driven Priors for Improved Spatial Models and Averages
Authors: Seshadri Pranay , Duncan Andrew B. , Thorne George , Vazquez Raul 
Published: September 2023

Abstract
This paper proposes a new physics-driven prior structure for engine spatial models. It is designed to be used on engine measurements, with the objective of obtaining more accurate spatial models and subsequent averages, even in the absence of extensive measurements. We demonstrate our methods on a fan bypass measurement plane using data from experiments and simulations.
Analysis and Optimisation of Polymer Electrolyte Membrane Fuel Cell (PEMFC)
Authors: Singh Neha , Shahpar Shahrokh , Indi Tristanto 
Published: September 2023

Abstract
Increased focus on net-zero carbon emission in various industries has called for diversification of sustainable energy sources to limit the dependency on fossil fuels. Hydrogen fuel cells have thus become a promising technology offering zero emission and high efficiency. It has a myriad of applications in the power generation, stationary and automotive industries. For short and medium haul flights, fuel cells offer a promising solution to combat climate change. It is light and efficient, utilising hydrogen as a readily available energy source. In this paper, extensive multi-physics CFD modelling is used in the development of fuel cell technology to build more efficient PEMFC with lower cost and weight for aviation application. The purpose of this paper is first to conduct a multi-physics simulation and analyse in detail the distribution of reactant species along the channels, water content, and pressure distribution. A multiphase simulation over a 22-channel serpentine PEMFC is carried out. The simulation results are validated by comparing the resultant polarization curve to the available experimental data. The analysis is then extended to the optimisation of fuel cells by parameterising the PEMFC fuel and air channels, and then conducting a Design of Experiment (DOE) which can be used to produce an optimal combination of parameters influencing the performance of the unit fuel cell.
Experimental and Numerical Investigations of Steam Expansion Rate in Low Pressure Steam Turbine
Authors: Tabata Soichiro , Segawa Kiyoshi , Takahashi Tadashi , Aoyagi Jin 
Published: September 2023

Abstract
This study focused on the expansion rate of steam; the effect on efficiency was investigated experimentally and numerically by varying the expansion rate of steam in the stage where condensation occurs by varying the flow rate and inlet temperature using a five-stage model steam turbine. The steam expansion rate of the stator blades in each stage was evaluated from the measured wall pressure and total pressure. In addition, the turbine efficiency was evaluated from the measured torque and mass flow rate, and the effect of flow rate and condensing stage can be taken into account for losses caused by condensation. In addition, numerical calculations to account for the effects of non-equilibrium condensation were performed using ANSYS CFX. The numerical calculations were able to show the details of the nucleation situation and the resulting changes in flow patterns.
Numerical evaluation of the subcooling loss showed that there was no difference in subcooling loss between different mass flow rates. The steam expansion rate was evaluated from the measurement results, and it was found that there was no difference in the steam expansion rate due to differences in mass flow rate. This corresponds to the numerical result that the subcooling loss does not vary with flow rate.