bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automated Component Preliminary Design and Evaluation in the Overall Engine Using Fully Coupled Approaches
Authors: Schmeink Jens , Schnoes Markus 
Published: October 2022

Abstract
Engine development is a long and complex process. Errors or unfavorable decisions made in the preliminary design phase have a lasting negative impact on the entire development process. The later a bad design decision has to be corrected, the more costs, time and effort are required for the correction. It would therefore be better to make forward-looking decisions right from the start.
Thanks to today’s simulation methods, this is possible to the greatest possible extent. The use of suitable methods supports and significantly shortens the development time. With an additional process automation through the coupling of design programs from different disciplines, promising solutions can be separated from less good ones early on in the development process using a broad multi-disciplinary approach.
This paper presents a numerical approach to evaluate overall engine performance while designing the high-pressure compressor (HPC). A parametric component design process is used to generate a model for a 2-D through flow analysis. This is coupled with a performance program via the data model and process management of a gas turbine design framework. Design as well as the off-design information of thermodynamic engine and aerodynamic component simulation are shared with each other. This way, more information can be gained than it would be the case for both disciplines individually. Therefore, different approaches of this form of multi-disciplinary coupling, often referred to as zooming, are compared regarding their usability and their numerical effort for the design of an HPC in an overall engine. The approach that shows the best results in this comparison is used for an example optimization process of a military engine HPC.
Effect of Mixing on the Anchoring and Combustion Regimes of Pure Hydrogen Flames in Sequential Combustors
Authors: Solana-Pérez R. , Shcherbanev S. A. , Ciani A. , Noiray N. 
Published: October 2022

Abstract
In this work we perform an experimental study of the combustion of pure hydrogen in the sequential stage of a generic combustor. This academic test rig is a simplified model of an industrial sequential combustor. The sequential fuel is injected using different injector geometries. The composition and temperature of the hot stream at the inlet of the sequential burner are defined by the mass flows of the hot combustion products from the first stage (30 kW natural gas-air flame with equivalence ratio of 0.7) and of the dilution air. This temperature is varied between 1100 K and 850 K by modifying the dilution air mass flow in order to study the different combustion regimes of the sequential hydrogen flame. High-speed imaging of OH radicals chemiluminescence is performed with optical emission spectroscopy to measure vitiated gas temperatures. In particular, we investigate the transition from a flame anchored in the sequential combustion chamber, to the situation where it stabilizes upstream into the mixing section, when the inlet flow temperature is increased. Of particular interest is the increasing rate of formation of autoignition kernels in this transition process. The underlying combustion regime change is analyzed with 0D reactor simulations, and the limitations of such a simplified low-order model of the flame location are discussed. The effects and importance of the mixing process between fresh fuel and the hot vitiated co-flow is examined. Two different injectors are compared under the same operating conditions that create different flow structures along the mixing section. As a result of that, they provide different degrees of mixing between the hydrogen and the hot vitiated flow and allow to demonstrate the impact of mixing quality on the flame morphology.
Design and Operability Challenges for Supercritical CO2 Plants: The sCO2-Flex Centrifugal Compressor Test Experience
Authors: Manuele Bigi , Valentina Bisio , Silvia Evangelisti , Marco Giancotti , Alberto Milani , Tiziano Pellegrini 
Published: October 2022

Abstract
Interest in supercritical carbon dioxide (sCO2) cycles has grown significantly in recent years. The peculiar properties of the fluid open unique opportunities but also poses several challenges. Here we aim at narrowing the knowledge gap in operating such plants, leveraging the test experience of a full-scale 5 MW Centrifugal Compressor prototype designed for the sCO2-flex project (H2020 funded program, grant agreement #764690). The test rig replicated a complete recycle loop for the compressor. In addition to validating the compressor’s performances in its design condition, a larger envelope of operation and transients was explored. The paper describes engineering groundwork and design choices regarding: i) transient operation such as pressurized startups and emergency shutdowns; ii) safety relief valves and discharge lines, with possible CO2 solidification; and iii) vibrations due to extremely high density. For all these topics, specific challenges brought by the sCO2 are described. We show the most meaningful results, in excellent agreement with predictions, and discuss key learnings from the test experience. We highlight how important it was to anticipate risks during the design phase and we give recommendations for future installations. We conclude with hints on testing severe off-design conditions, with two-phase flow at compressor suction.
Accelerating the Development of a New Turbomachinery Concept in an Environment With Limited Resources and Experimental Data: Challenges
Authors: Rubini Dylan , Karefyllidis Nikolas , Xu Liping , Rosic Budimir , Johannesdahl Harri 
Published: October 2022

Abstract
This paper presents the requirements for a tailored design ecosystem to accelerate the development of a new turbo-reactor for hydrocarbon cracking. The objective of this novel turbo-reactor concept is to eliminate carbon emissions from the radiant section of the plant. However, the time constraint for this energy- and carbon-intensive cracking industry to fully decarbonize is severely restricted. Therefore, the development of this new concept must be accelerated to a market-ready product within a limited time frame. However, the novelty of the design requirements and the unique level of complexity of the flow physics result in inadequate experimental data, with insufficient time and resources to develop a new measurement database. This shifts the design system towards computer-aided engineering platforms; however for the turbo-reactor, the uncertainty level of these low-order numerical tools (e.g., RANS and throughflow solvers) is elevated for three reasons. First, blockage, deviation and loss correlations integrated within throughflow solvers are unsuitable to capture the flow physics in the turbo-reactor. Second, RANS turbulence closure models need to be re-calibrated for this machine. Finally, due to the chemical reactions, the working fluid properties vary significantly along the gas path and strongly influence the aerodynamics. A new tailored design ecosystem is proposed to address these challenges. The relatively low Reynolds number regime throughout the turbo-reactor enables upfront and routine eddy-resolving simulations to be performed. This allows the new design system to feature a feedback mechanism in which high-fidelity CFD data is used to calibrate lower-fidelity — but less CPU intensive — design tools and empirical correlations. Crucially, the new toolchain is customized in order to capture the influence of the reactions on the thermodynamic properties, as well as to provide the aerodynamic designer with immediate insight into how stage-design modifications influence the reaction product yield distribution. This paper demonstrates the capabilities of an efficient aerodynamic-chemistry coupling methodology that has been implemented within an in-house CFD solver.
Study on Titanium Aluminide Turbine Wheel Blade Machining for Turbochargers by Electrochemical Machining (ECM)
Authors: Aono Masahiro , Shimizu Tatsuya , Obi Nobuaki , Goto Akihiro 
Published: October 2022

Abstract
A turbocharger is the device of a car that is used to add extra air into the combustion chambers of an engine. Recently, researches have been conducted on the use of TiAl materials in turbine wheels to replace traditional Ni-based alloys. Since TiAl material has good heat resistance and is lightweight, it is effective in reducing the moment of inertia of the turbine wheel.
However, the TiAl material has a problem that it has high viscosity when it is melted and that it is not suitable for precision casting. Even when the thickness of the turbine wheel blades is increased to about 1 mm, the molten TiAl does not always flow to the tip of the mold, and the problem of chipped tip often occurs.
In this study, authors investigated the method of manufacturing blades with thickness of more than 1 mm by precision casting in a yield of almost 100%, and then machining them into thin shape of about half thickness by electrochemical machining (ECM).
In ECM, it is well known that the flow of the electrolyte affects the machined shape. It was difficult to finish the blade in the desired shape at first and unmachined area remained. Then authors examined the flow of electrolyte using computational fluid dynamics (CFD) analysis and tried to make it appropriate. As a result, a technology was established to machine turbine wheel blades that meet the requirements for shape accuracy and surface roughness in a short time of about 100 seconds.
The Design and Optimisation of a 100% Hydrogen Micro Gas Turbine Micromix Combustor: Preliminary Hydrogen Injection Depth Characterisation Using Cold Flow Steady RANS
Authors: Devriese Cedric , Snijders Simon , De Paepe Ward , Bastiaans Rob 
Published: October 2022

Abstract
In a modern electricity grid, with fluctuating renewable energy input and problems linked to construction of large power plants in densely populated areas, local, flexible, and zero-emission electricity and heat production becomes evermore important. Consequently, we research 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, based on the Micromix principle. Based on previous work, we observed that the hydrogen injection depth was critical in minimising thermal NOx formation. To characterise the hydrogen Jet in Cross Flow (JICF) mechanism more deeply, we first designed a simplified single nozzle variant of the micromix geometry. Using this test geometry, we analysed the relation between the hydrogen injection pressure and the hydrogen injection depth, perpendicularly into the air flow, using both an analytical model and cold flow steady RANS simulations. From these simulation results we obtained a preliminary optimal range for the injection pressure, so that the hydrogen does not protrude too far into the air stream (thereby increasing the residence time and increasing the possibility of higher thermal NOx formation), nor too little (thereby reducing the mixing of both fuel and air and increasing the chance of combustion too near to the wall). Based on these results, we can, using hot flow steady RANS simulations, validate the optimal hydrogen injection pressure range from the single-nozzle, cold flow results, for minimal thermal NOx formation, in a follow-up research.
Experimental Hydraulic Performance Study of a Primary Surface Recuperator With Cross-Wavy Microchannels for Portable Microturbines
Authors: Li Hui , Zou Zhengping , Chen Yiming , Li Huan , Fu Chao 
Published: October 2022

Abstract
Portable microturbines with high power and energy densities are attractive candidates for mobile power sources. Due to the limitations of compressor pressure ratio and turbine inlet temperature, a compact and lightweight recuperator is the mandatory component of this type of microturbines to achieve high thermal efficiency. Typically, microchannels with thin wall thickness are used for heat transfer enhancement. However, the reduction in channel size may significantly increase the pressure drop of both fluids. Owing to the lack of existing experimental data for ultra-compact microchannel recuperators of portable microturbines, the hydraulic performance of a newly-designed primary surface recuperator with cross-wavy microchannels (CW-PSR) was experimentally studied. The 50 μm-thick heat transfer plates were used for the CW-PSR core, in which the hydraulic diameters of gas and air channels are 848.8 μm and 598.6 μm, respectively. Hence, the surface compactness of the CW-PSR prototype is about 2428 m2/m3. We tested the hydraulic performance of the CW-PSR both under hot and cold conditions with Reynolds numbers ranging from 320 to 980. The experimental results show that the pressure drops on both sides increase with increasing mass flow rate, while the hot conditions with high inlet temperature result in larger pressure drops. Besides, it was confirmed that the friction pressure drop in the heat transfer region accounts for more than 60% of the total pressure drop. Finally, a new correlation of friction factors for cross-wavy microchannels was obtained based on experimental results.
Conjugate Heat Transfer of Cylindrical and Trenched Film Cooling Designs With Array Jet Impingement
Authors: Fischer Lukas , Sanchez Andrés , Schleich Fabian , Feller Fabian , Raffelt Richard , Pfitzner Michael 
Published: October 2022

Abstract
A numerical film cooling study involving different external cooling designs, thermal barrier coating (TBC) and internal cooling methods is performed. The steady Reynolds Averaged Navier Stokes (RANS) equations are solved including conjugate heat transfer (CHT). The heat transfer coefficient and material properties of the TBC and vane material lead to a proper scaling of the Biot number with respect to real engines. The cooling efficiency of the external surface and of the wall interface between TBC and vane are evaluated. Three film cooling designs, namely standard effusion hole film cooling as well as transverse and optimized trenches are investigated. Moreover, the effect of array jet impingement and convective channel cooling is investigated onto the external and interface cooling efficiency. The jet Reynolds number of the impingement and effusion cooling is varied between 3100–12300 at blowing ratios between 0.3 and 1.2. The main-stream Reynolds number varied between 4500 and 11000 depending on the tested density ratio. The external cooling efficiency of both trench designs showed to be superior to the standard effusion case. With respect to the interface cooling efficiency, there was an improvement in efficiency of 0.1 visible for the trenched designs compared to the standard effusion hole design. Moreover, flow ingestion into the trenches and the external heat flux and heat transfer coefficient are investigated.
LNG Regasification Plants Integrated With Low- and High-Temperature Organic Rankine Cycles
Authors: Tola Vittorio , Delogu Eliana , Finkenrath Matthias 
Published: October 2022

Abstract
The use of natural gas has continuously increased and reached 24.7% of the worldwide primary energy supply in 2020. The same trend applies to Liquefied Natural Gas (LNG), which contributed to 52% of overall natural gas trades in the same year. In this context, the recovery of the cold energy available at LNG receiving terminals during the process of regasification is of a critical importance.
This paper addresses the integration of the regasification process with an Organic Rankine Cycle (ORC) in order to exploit the available LNG cold energy, by condensing the organic fluid. In addition, a gas turbine exploits differences between regasification and distribution pressures. The analysis covers different organic fluids and two ORC heating source configurations: a) a low-temperature one, using seawater, and b) a high-temperature one, using exhaust gas. In addition, the integration of a natural gas-fired topping gas turbine, which uses the LNG cold energy by compressor inlet air cooling, was simulated. The performance of a medium size regasification terminal (50 kg/s) was evaluated as a function of both the regasification and the natural gas distribution pressures.
Dedicated models have been developed using Aspen Plus software to simulate the regasification process and the integrated topping cycles (Organic Rankine and Brayton), and their mutual energy integrations.
The analysis shows that ORC power outputs from 2 MW up to 4.5 MW in case a) and from 6 MW up to 9 MW in case b) can be reached. The topping gas turbine benefits from the inlet air cooling and can add a power output of 35 MW to 40 MW. R125 was the best working fluid for a low-temperature ORC, while R600a showed the best performance for a high-temperature application.
Machine Learning-Based Multi-Disciplinary Optimization of Transonic Axial Compressor Blade Considering Aeroelasticity
Authors: Kang Hyun-Su , Kim Youn-Jea 
Published: October 2022

Abstract
The optimal design of the turbomachinery field can produce the best results when considering multiple fields (e.g., structural vibration, aerodynamic, and aeroelasticity). Since multi-disciplinary phenomena are very complex and nonlinear, a higher level of optimization is needed. In this study, the transonic axial compressor blade was optimized using machine learning-based multi-disciplinary optimization techniques. The entire simulation includes important three factors to consider when designing the axial compressor blade: vibration, aerodynamic performance, and aeroelasticity. In the first step of the optimization, six variables that make up the blade design were used in a design of experiments to explore the design space.
Frequency, efficiency, pressure ratio, and aerodynamic damping ratio were used as the output parameter used in the optimal design. The first to third blade modes frequency from the modal analysis were used for parameters of vibration fields. The efficiency and pressure ratio are values that can be obtained from steady CFD calculations for evaluating aerodynamic performance. The aerodynamic damping coefficient was obtained from transient CFD, which is widely used to determine the presence or absence of fluid-induced vibration and flutter.
As a result of machine learning-based optimization, the optimized blade shape has a lower risk of blade resonance. Also, the aerodynamic performance of the axial compressor has been improved compared to the reference model. In addition, the aerodynamic damping coefficient, an important indicator in terms of aeroelasticity, rose by up to 15%, completing optimization considering the aeroelastic effect.
Inlet Flow Distortion Dependencies for Tail Mounted Ducted Fans on Hybrid-Electric Commuter Aircraft
Authors: Engelbrecht E. Geoffrey , Gkoutzamanis Vasilis G. , Nasoulis Christos P. , Kalfas Anestis I. 
Published: October 2022

Abstract
A numerical analysis based on Computational Fluid Dynamics (CFD) is carried out to investigate the influence of the fuselage transition and axial offset, on the inlet distortion and performance of a tail mounted fan, for a short-haul commuter aircraft. For the examined configurations, it is predicted that varying the angle of the fuselage transition does not have a significant impact on the radial distortion, for a typical fan mounted at the centreline of the fuselage. The wake behind the fuselage is predicted to increase in size as the slope of the fuselage is increased, however, the positive suction from the fan is sufficient for the flow to fully recover before the fan duct inlet. Nevertheless, it is predicted that offsetting the fan from the fuselage centreline produces a more significant increase in distortion in the circumferential direction. The propulsive power of the fan is predicted to increase slightly with increasing offset mainly due to the side of the fan which is less obstructed by the fuselage. However, the wake on the opposite side is predicted to increase significantly persisting almost to the inlet of the fan duct. A vortex formed upstream of the fan increases in strength with increasing offset. This vortex helps to offset the increase in circumferential distortion by re-energizing the flow in the wake of the fuselage. This causes the circumferential distortion to remain roughly constant between offsets of 25% and 50% of the fuselage radius. It is likely though that this vortex will deteriorate the performance of the fan.
Optimisation of an ORC Radial Turbine Using a Reduced-Order Model Coupled With CFD
Authors: Alvarez-Regueiro Eva , Yang Bijie , Barrera-Medrano Esperanza , Martinez-Botas Ricardo , Rajoo Srithar 
Published: October 2022

Abstract
This paper presents the geometry optimisation of a single stage radial turbine for an Organic Ranking Cycle system operating over a pressure ratio of 9. The specific fluid used in this investigation is R1233zd (E), but the methodology applies to other organic fluids as well. The ORC system is used to recover excess waste heat from the operation of an offshore oil and gas platform in the gulf of Thailand and its conditions will be replicated at pilot plant level.
The geometry is optimised for the highest total-to-static efficiency using non gradient based algorithms to allow for wide design space. Firstly, a 1D meanline geometry is optimised, which is followed by a Computational Fluid Dynamics (CFD) optimisation in 3D using a parameterised model. CFD validate and calibrate the meanline model as well as to understand the flow and the sensitivity of the design parameters not captured by the low-order model. Moreover, the flow field of the successful designs is analysed by CFD to identify the main flow structures that explain the difference in performance among the designs. The real gas thermophysical properties of R1233zd (E) are calculated using equations of state to account for the non-ideal gas behaviour.
Multi-Objective Development of Machine-Learnt Closures for Fully Integrated Transition and Wake Mixing Predictions in Low Pressure Turbines
Authors: Akolekar Harshal D. , Waschkowski Fabian , Pacciani Roberto , Zhao Yaomin , Sandberg Richard D. 
Published: October 2022

Abstract
In low pressure turbines (LPT), due to the low Reynolds number a large part of the blade boundary layer remains laminar and transition may occur due to flow separation. The boundary layer details at the blade trailing edge can change substantially depending on the transition region topology and can strongly influence the wake mixing occurring downstream. Accurately predicting these flow phenomena still poses a challenge for Reynolds averaged Navier-Stokes (RANS) and unsteady RANS methods. In this work a recently developed computational fluid dynamics (CFD) driven machine learning framework featuring multi-expression, multi-objective optimization is exploited for the first time to simultaneously develop transition models and turbulence closures in a fully coupled way, aimed at improving both transition and wake mixing predictions in LPTs. The T106A blade cascade with an isentropic Reynolds number of 100,000 is adopted as a training case. The baseline transition model is based on a laminar kinetic energy transport approach, and the machine learning approach is used to reformulate the source terms as functions of suitably defined non-dimensional ratios. Additionally, machine learning based explicit algebraic Reynolds stress models are used to improve wake mixing predictions, making use of a specifically and newly developed wake sensing function based strategy that allows an automated zonal application of the developed models. It is shown that both on-blade performance and wake mixing can be predicted accurately with data-driven transition and turbulence models that have benefited from CFD feedback in their development, ensuring that their mutual interactions are captured.