bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and Control System Development of a Turbocharged Proton-Exchange Membrane Fuel Cell System
Authors: Cavo Matteo , Mantelli Luca , Crosa Silvia , Bozzolo Michele , Magistri Loredana 
Published: September 2023

Abstract
Pressurized Polymeric Electrolyte Membrane Fuel Cell (PEMFC) systems are growing among electrical power generation systems, as a zero-emissions technology. In this framework, the University of Genoa have been modelling an innovative concept for the application of low-temperature fuel cells. A turbocharged proton exchange membrane fuel cell (TC-PEMFC) plant layout with design output power higher than 200 kW is investigated. Pressurizing air before entering the stack can increase the stack efficiency and recovering the exhaust air within a turbocharger leads to better system performance. A crossflow flat pack membrane humidifier has been introduced between the air turbocharger and the PEMFC to guarantee proper operating condition into the stack. Finally, a Gas-to-Gas (GtG) heat exchanger enables cooling of the charging air while recovering the thermal energy through the turbine. In this paper, the authors present a dynamic model of an innovative turbocharged PEMFC system developed in Matlab/Simulink environment. The “RealTime” library, built by the University of Genoa, has been adopted: most of the models have been previously validated and a few new models have been customized for this application. The Matlab/Simulink model shown in this paper is used to aid the design process of the future plant, to evaluate the performance of the plant in many operating conditions and to design and test its control system. At the current stage, the model is ready to be used for on-design, off-design and transient analyses. It can be used to investigate the effect of different design choices, as well as to determine the specifications of the plant components. Some preliminary steady-state simulations are presented: the performance of the system in a wide operative range (cell currents between 150 A and 500A), with net power higher than 300 kW and system efficiency up to 58%.
Impact of Non-Axisymmetric Inlet Guide Vane Stagger Angle on the Performance and Stability of a Low-Speed Research Compressor
Authors: Xia Kailong , Deng Hefang , Zhu Mingmin , Qiang Xiaoqing , Teng Jinfang , Lu Shaopeng 
Published: September 2023

Abstract
The paper examines the impact of non-axisymmetric inlet guide vanes (IGV) stagger angle on the performance and flow behaviors of a 4-stage low-speed research compressor at Shanghai Jiao Tong University. The One-ninth entire annulus of the IGV row and the first stage are modeled as the computational domain. The stagger angle of one in nine IGV blades is varied by 1.5 and 3 degrees in the anticlockwise direction from the datum case. The sensitivities of these non-axisymmetric configurations to two different total pressure inlet profiles (the datum and defective ones) are analyzed using RANS and URANS numerical methods.
Results indicate that the impact of IGV stagger angle deviations on overall performance is negligible under the datum inlet. However, the performance and internal flow behaviors are significantly influenced by the defective inflow, especially in the 3-degree configuration. When stagger angle varies by 3 degrees, an approximately 2.39% efficiency penalty at the near stall condition and a 1.58% reduction in stall margin occur. The analysis on the internal flow behaviors shows that, with the datum inlet, only neutral trailing edge separations are observed in both design and near stall conditions. While under the defective inflow, a large corner separation exists near the rotor suction surface, resulting in a distinct performance degradation. The dynamic pressure signals at the rotor tip are examined to investigate the unsteadiness inside the rotor passage under both inlet conditions. It is demonstrated that for both inlet, the 3-degree deviation of IGV blade magnifies the intensity of the prominent frequency around the period of 2/3 blade-passing-frequency, which represents the generation, oscillation, and shedding of leakage vortices. Furthermore, a characteristic frequency 2044 Hz is newly observed in the 3-degree configuration under defective inflow. It might be brought by the radial migration and fluctuation of low-energy fluid separated from the rotor suction surface. Further investigations are required to study the effects of varied IGV staggers on rotor-stator matching and stall inception mode.
Influence of Air/Hydrogen Momentum Ratio, Equivalence Ratio and Dilution Hole Geometry on the Performance of a Micromix Combustor for a 100 kWe mGT
Authors: Devriese Cedric , Derks Sander , Kole Jasper , Schlösser Yarne , De Paepe Ward , Bastiaans Rob 
Published: September 2023

Abstract
Against the background of a growing deployment of renewable electricity production, like wind and solar, the demand for energy storage will only increase. One of the most promising ways to cover the medium to long-term storage is to use the excess electricity to produce hydrogen via electrolysis. In a modern energy grid, filled with intermittent power sources and ever-increasing problems to construct large power plants in densely populated areas, a network of Decentralised Energy Systems (DES) seems more logical. Consequently, building a previous work, there is a need for the design and optimisation of a hydrogen fuelled micro Gas Turbine (mGT). This paper focusses on our continued development and optimisation of the low-NOx hydrogen combustion chamber, using steady-state RANS CFD simulations. To further optimise the primary zone of the combustor, this work concentrates on the specific impact of the air/fuel momentum ratio, the primary zone equivalence ratio and dilution zone geometry on the combustor performance. First, the air mass flow rate and the hydrogen inlet pressure are varied within a specified control range. This results in a range for the momentum ratio and the equivalence ratio for which we can analyse the resultant NOx concentration at the combustor outlet. This allows the momentum ratio and the equivalence ratio to be optimally chosen for a new primary zone combustor geometry with lower NOx formation. In a second step, this primary zone design is completed with an initial and separately optimised design of the secondary air zone or dilution zone. An analysis was made on the variation of several key dilution zone design parameters such as; the diameter of a dilution hole, the number of dilution holes in a single row, the variation in size between the holes in the same row and the distance from the centre of the single row of dilution holes to the combustor head. This parameter variation study affected the secondary air mass flow rate, the average outlet temperature, the outlet temperature homogeneity and the NOx emissions at the combustor outlet, on the basis of which a first simple, single dilution hole row is proposed and optimised. Both the final optimisation of the primary zone and the optimisation of the secondary zone will come together a new micromix combustor geometry that will be part of the future work and will be included in the presentation at GT2023.
Cloud Based Predictive Monitoring System for Steam Industrial Turbogenerator
Authors: Sanguineti Antonio , Venuti Roberto , Violante Antonio , Busi Adriano , Malavasi Francesco 
Published: September 2023

Abstract
Steam turbogenerators have a wide application in the exploitation of thermal from the combustion of biomass, general waste to energy and natural gas.
In the current social and economic worldwide situation, ensuring the continuity of the industrial process, is a competitive advantage for biomass industries and waste incinerators.
In this context, Fincantieri has developed a cloud-based monitoring system, based on instrumentation installed together with virtual sensors with the aim of detecting deviations from the design, foreseeing the intervention of alarms and trips of the conventional control system. The outcome is the increasing machine availability.
The control system signals are published (via OPC server), processed to generate additional sensors (called ‘virtual sensors’) and distributed to a cloud, overcoming the limited memory capacity.
Thermo-fluodynamic quantities are evaluated to track the machinery aging. Rotor dynamics and bearing are monitored with an operational database to create dedicated monitoring algorithms.
Installation of additional instrumentation is forecasted to allow the updating and the monitoring of all the relevant parameters.
Once the development phase was completed, the system was installed and tested in a first prototype plant. Two powerplants are nowadays already monitored by remote.
Rework and Repair Options for Steam Turbine Components Subject to Flexible Operation
Authors: Biesinger Frank , Lorini Huascar , Shah Ritesh 
Published: September 2023

Abstract
The increase in renewable energy penetration on the grid has accelerated the need to transition conventional fossil-based energy sources from their traditional base load operation to more flexible operational regimes. The mode of operation changed dramatically in terms of number of starts, operating hours per annum and variation in load level. This results in greater thermal transients on operational equipment leading to an increase in Low Cycle Fatigue damage. To ensure the continued integrity of the steam turbine components, it is essential to assess the lifetime status by applying Residual Lifetime Analysis methods.
Depending on the amount of lifetime consumption and the extend of potential crack findings, different component repair options are possible. The rework or repair options can be divided into two main groups, namely cold- and hot-rework. These two options can also be carried out consecutively. All rework or repair options provide the opportunity to improve the application of a component by applying profiling with improved stress fields and even superior materials, in the case of hot rework.
The aim of the rework / re-conditioning is to ensure that the steam turbine component is suitable for future operation. This ensures that plants are well placed to deliver more flexible operation in the energy industry through carefully tailored refurbishments and reworks.
Enhancing the Damping Capability of Rib-Stiffened Structures With Additive Manufacturing
Authors: Scott-Emuakpor Onome , Johnson Philip , Celli Dino , George Tommy 
Published: September 2023

Abstract
The focus of this study is to determine the effectiveness of inherent vibration suppression via additive manufacturing (AM) of laser powder bed fusion (LPBF) Nickel Alloy 718 plates with stiffening structures. The prevalence of stiffening structures in many industries is a testament to their ability to improve part stiffness, shift natural frequencies of critical parts from operational ranges, and reduced system noises. Motivation for understanding stiffening structures in aerospace industries (specifically in turbine engines) comes from the potential to improve the designs of low-pressure compressor blades, rotor flange connections, and engine frames for next generation flight. The damping technology applied to the stiffening structures in this study is the Inherent Damping via AM Processes (i-DAMP™). Assessing the effectiveness of i-DAMP™ uses vibration experimentation results of plate components with low and high aspect ratio stiffening structures. The results from this assessment show significant vibration suppression with similitude to previous i-DAMPTM demonstrations, and the vibration suppression is realized while maintaining negligible changes in stiffening capabilities.
Best-Practice Guidelines for High-Fidelity Simulations Based on Detailed Analysis of a Highly-Loaded Low-Pressure Turbine Cascade
Authors: Rosenzweig Marco , Giaccherini Simone , Pinelli Lorenzo , Kozul Melissa , Sandberg Richard , Marconcini Michele , Pacciani Roberto 
Published: September 2023

Abstract
The highly-loaded, linear low-pressure turbine cascade T106C is a popular validation test case for direct numerical and large-eddy simulation solvers. In most previous high-fidelity simulations, the cascade’s geometry has been simplified by considering only a fraction of the spanwise extent. A periodic boundary condition in the spanwise direction is then typically used to analyze the flow in the mid-span region. However, it has proved challenging to numerically reproduce experimental data of the blade loading at engine-relevant conditions of isentropic exit Reynolds number of 80,000 and isentropic exit Mach number of 0.65 in the absence of a turbulent inflow. The discrepancies between high-fidelity simulations and experiments have mostly been attributed to an insufficient spanwise domain extent in the numerical setup. The present paper resolves these differences by including spanwise end-walls in the numerical setup using a dedicated high-fidelity computational fluid dynamics solver. Both the blade loading and the wake loss are thus adequately predicted by the present numerical study, which had not previously been achieved in the literature. Furthermore, a series of highly-resolved large-eddy simulations have been performed proving that spanwise periodicity cannot capture the underlying flow physics determining the blade’s mid-span performance at the considered operating point. For these cases, grid resolution and spanwise domain extent were systematically varied to highlight their combined effect on the blade loading along the suction side and wake loss prediction. Finally, a rigorous comparison between different flow solvers and numerical setups summarizes best-practice guidelines for conducting high-quality, scale-resolving simulations of highly-loaded low-pressure turbine blades.
Centrifugal Compressor Surge in Innovative Heat Pump – Part 1: Fluid Dynamic and Vibrational Analysis
Authors: Ferrando Marco , Reboli Tommaso , Reggio Federico , Niccolini Carlo Alberto , Silvestri Paolo , Traverso Alberto , Sishtla Vishnu 
Published: September 2023

Abstract
In the current energy scenario, it is necessary to reduce fossil fuel consumption to achieve the far-sighted and stringent decarbonization goals. To date, heat is mainly produced through fossil fuels. Alternatively, electrically driven heat pumps can exploit renewable power to recover environmental and waste heat, offering energy efficient and environmentally friendly heating and cooling for applications ranging from domestic and commercial buildings to process industries. For this reason, they are expected to play a primary role in complementing or displacing natural gas boilers in the residential and industrial sectors in the near future.
Centrifugal compressors are already used as prime movers of the working fluid in heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low noise. However, they are subject to instabilities such as surge and stall like any other dynamic compressor and these phenomena develop quite differently than in classic open-loop systems such as gas turbines. In fact, such peculiarity is mainly due to the closed-loop configuration with real gases in two-phase conditions, occurring in typical heat pump cycles. In addition, heat exchangers also contribute to make these phenomena different from what is commonly studied. Compressor surge in closed loop heat pump systems has received lower attention than other applications by the engineering community, lacking dedicated experimental characterization and clear exposition of the phenomenon.
The aim of this paper is to experimentally investigate the behavior of a centrifugal compressor installed into an innovative close loop heat pump system under stable and unstable conditions from both vibrational and fluid-dynamic points of view. The impact of the main process parameters on the evolution of the instability is shown, highlighting how surge cycles change by varying system operating conditions. The energy contents of surge cycles and pressure fluctuations are highlighted, using data post-processing techniques such as Fast Fourier Transform and Phase Locked Average.
The vibroacoustic analysis enrich the comprehension of the phenomena. The experimental results shown in this paper can be a basis for the future development of validated mathematical models of closed loop heat pumps systems equipped with dynamic compressors operating under stable and unstable operating conditions.
Quantification of Geometric Variability Effects Through a Viscous Through-Flow Model: Sensitivity Analysis of the Manufacturing Tolerance Effects on Performance of Modern Axial-Flow Compressor Blades
Authors: Budo Arnaud , Hillewaert Koen , Le Men Thibault , Arnst Maarten , Terrapon Vincent E. 
Published: September 2023

Abstract
An important question for turbomachine designers is how to deal with blade and flowpath geometric variabilities stemming from the manufacturing process. The challenge consists in identifying where stringent manufacturing tolerances are absolutely necessary and where looser tolerances can be used, as some geometric variations have little or no effects on performance, while others do have a significant impact. Because numerical simulations based on Reynolds Averaged Navier-Stokes (RANS) equations are computationally expensive for a stochastic analysis, an alternative approach is proposed, in which these simulations are complemented by cheaper through-flow simulations to provide a finer exploration of the range of variations, in particular in a context of robust design. The overall goal of the present work is to assess through a sensitivity analysis the ability of through-flow modeling to predict geometric variability effects on compressor performance and, in particular, to capture the main trends. To do so, through-flow simulations are compared to RANS simulations applied to a modern low-pressure compressor designed by Safran Aero Boosters. Within the scope of this preliminary study, perturbations of the three-dimensional position of undeformed stator blades and deformations of the hub and shroud contours are introduced one-factor-at-a-time per simulation. Their range is defined based on the tolerance limits typically imposed in the industry and on observed manufacturing variability. It is found that the through-flow model broadly provides realistic predictions of performance variations resulting from the imposed geometric variations. These results are a promising first step towards the use of the through-flow modeling approach for geometric uncertainty quantification.
Characterising the Unsteady Flow-Field in Low-Flow Turbine Operation
Authors: Kim Hye Rim , Stania Lennart , Maroldt Niklas , Oettinger Marcel , Seume Joerg R. 
Published: September 2023

Abstract
Current operational considerations require steam turbines to operate in a more flexible way, with more frequent and faster start-up and an increasing part-load operation. For very low mass-flow rates, the interaction of highly separated flow with the high speed rotor blades causes windage flow. This type of flow is characterized by increased temperature and highly unsteady flow, which forms vortex structures that rotate at a fraction of the rotor speed. If their magnitude is sufficiently high and the frequency is close to the blade eigenfrequency, non-synchronous vibration (NSV) can be induced. In this paper, low-flow turbine operation is investigated using a three-stage turbine rig that features an instrumentation concept focused on capturing aerodynamic and aeroelastic phenomena. Extensive steady probe, unsteady pressure, and tip-timing measurements are utilized. The experimental scope covers a wide range of operating points in terms of rotational speed and mass flow rates. Low-flow regimes are detected by a reversal in torque and increase in temperature. Unsteady measurements during transient operation identified large-scale vortical flow structures rotating along the circumference, so called rotating instabilities (RI). The onset, growth, and breakdown regimes of RI are characterized for different low-flow conditions. The quantitative characteristics of RI with regards to nodal diameter and rotational speed are derived by a cross-correlation of multiple unsteady sensors. The blade vibration measurements show a moderate structural response from unsteady aerodynamic excitation, indicating no significant NSV occurring in the present experimental setup. Later in the study, an acoustic excitation system has been applied to trigger a locked-in NSV without interrupting the coherent flow structures. From that, significant blade response has been observed, revealing a high degree of mistuning and damping of the rotor blading.
An Experimental Study of the Stability and Nearfield Structure of Oxyfuel Jet Flames at Elevated Pressures
Authors: Bukar Muhammad , Basnet Suman , Wu Bin , Magnotti Gaetano 
Published: September 2023

Abstract
This study presents experimental results of the stability limit and the nearfield structure of oxy-methane jet flames at pressures ranging from 2–5 bar. The oxidizer used in this campaign consists of 40% O2 and 60% CO2. Two sets of cases were studied: one where pressure increase was achieved by keeping the fuel Reynolds number constant and the other where the velocity was kept constant while increasing pressure. Stability limits (lift-off velocity) are reported for various coflow velocities at different operating pressures. Natural flame luminosity imaging with a DSLR camera and combined CH* chemiluminescence using an ICCD (PIMAX 4) are used to characterize the nearfield structure of the flame. The CH* results were then processed to extract the attachment location, defined in terms of attachment height and radius. The study mainly investigates the effect of pressure on the flame attachment height and radius. The DSLR images complement the study with qualitative information on the flame appearance and sooting propensity. Results show that at constant Reynolds number, the attachment height decreases with pressure for all cases considered while the attachment radius increased with pressure increase. At constant velocity, however, both the attachment height and radius were observed to decrease with increased pressure.
Numerical Investigation on Combustion Characteristics and Emissions of Hydrogen/Methane Blends in Flamesheet Combustor
Authors: Vo Duy-Tan , Jung Jine-Sung , Ryu Jaiyoung 
Published: September 2023

Abstract
Flamesheet is a novel head-end combustor component design that can accommodate up to 40% H2 in volume fraction while maintaining a low NOx emission at 9 ppm. It is compatible with many popular combustors, including 501F DLN, 7F DLN 2.6, and 7F DLN 2.6+. This study used a numerical investigation to examine the combustion characteristics of methane blended with hydrogen at various compositions in a lean premixed swirling flame in a W501F Flamesheet combustor. The volume of hydrogen enrichment ranged from 0 to 40%. A numerical approach using the partially premixed flamelet model and turbulent SST k-omega model was adopted to simulate the Flamesheet combustor. The flamelet-generated manifold was used to analyze the effect of hydrogen enrichment and equivalent ratio on flame operation, temperature distribution, CO and CO2 emissions, and species concentrations. The operating principle of this Flamesheet model was described, and details of flow characteristics and heat transfer were discussed. The results show that the Flamesheet combustor can operate stably with up to 40% hydrogen. The outlet temperature can be maintained at a constant by controlling the equivalent ratio as the hydrogen concentration increases. The effect of adding hydrogen on species concentrations was also discussed in detail.