bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Modeling of Liquid Jet in Non-Uniform Crossflow Using Enhanced Madabhushi Model
Authors: Feiz Homayoon , Zhao Wei , Kubicki Dominik , Frackowiak Marcin , Kumar Vivek , Jadeja Harshrajsinh , Nakod Pravin , Shrivastava Sourabh , Nallamothu Sravan K. , Lambert Markus , Lee Jong Guen , Song Jinkwan 
Published: October 2022

Abstract
One of the most used spray configurations for gas turbines and power combustors is liquid jet in crossflow. The process of breakup of liquid jet is very complex and understanding this mechanism is of paramount importance in engine design. This has led to the commencement of several studies from leading research groups [1–6]. Several new modeling methods such as the Madabhushi breakup model or more detailed VOF and Level set methods have been used successfully to understand and describe these complex breakup processes. However, most of these studies have been restricted to liquid jet in uniform single stream crossflow. In reality, these jets could be subjected to several gaseous streams and the breakup mechanism may vary significantly. Recently there have been some studies to understand the effect of non-uniformities on the crossflow velocity distribution and the droplet diameter. In the current work, we attempt to extend the scope of the Madabhushi breakup model to jets subjected to non-uniform crossflow. Non-uniform crossflow is created by co-directional and parallel gas flow using several hollow tubes. Locally, the momentum flux ratio changes by a factor of 4 and uniformity ratio (the ratio of the velocities of the two gas streams) of 2. A modified version of the Madabhushi model as proposed by Lambert et. al is used here to simulate the jet breakup. Model tuning has been conducted using University of Cincinnati Research data specifically designed for this configuration in partnership with General Electric Company. For turbulence, realizable k-ε with scalable wall function is used. The droplets are tracked using Ansys Fluent Discrete Particle Model (DPM). A second modeling approach VOF-to-DPM is also used which uses VOF equation along with LES with Dynamic Kinetic Energy Subgrid-Scale Model. This model requires no fine tuning of parameters and is more accurate but comes with more computational expense.
Various simulations are performed with pure water, pure diesel and emulsified diesel and water with uniform and non-uniform cross flows inside a chamber at a pressure of 50psi. Overall, the trends due to difference in material properties of the two liquids especially on penetration and Sauter mean diameter are well captured. The droplet characteristics such as axial velocity, Sauter mean diameter and volumetric flux are compared with experimental measurements and shows reasonable agreement. Overall, the liquid penetration is within reasonable accuracy. Discrepancies were seen in the spatial variation of the spray quantities such as Sauter mean diameter, droplet axial velocity etc. The simulation revealed a more averaged field whereas in experiments some layering was observed with bigger droplets at the edge of the spray, away from the wall.
Powering Telecommunication Towers Using Vertical Axis Wind Turbines: A Feasibility Study in Saudi Arabia
Authors: Toor Zakria , Bahaidarah Haitham M. , Rehman Shafiqur 
Published: October 2022

Abstract
This paper presents a road map to select and integrate an existing off-the-shelf Vertical Axis Wind Turbine (VAWT) for telecommunication towers. A comprehensive feasibility analysis is performed based on technical, economic, and greenhouse gas (GHG) emission reduction factors. More than 80% of these towers have a maximum power requirement of less than 3.5 kW. Hence, the study is conducted for wind turbines with 10 kW rated power. Four commercially available VAWTs are selected and analyzed at two locations within Dhahran using hourly wind data recorded between 2019 and 2020. The study found that the best wind turbine has a capacity factor of 18.7% and 19.1% for these sites at 10 m hub height, and the capacity factor increases to 21.6% and 22.3% at 50 m hub height. Similarly, the specific yield of the turbine also increases from 137 to 263 kWh/m2 as the hub height is increased from 10 m to 50 m. Economic analysis revealed that the best wind turbine results in 15,043 kWh of energy exported to the tower leading to 7.2 years’ payback period. Emissions analysis for the best case reduces the GHG emissions by 83%, which amounts to 23.3 tons of CO2.
Heat Transfer Enhancement of Swirl Cooling by Different Crossflow Diverters
Authors: Xiao Kun , He Juan , Feng Zhenping 
Published: October 2022

Abstract
Swirl cooling is a promising cooling technology in gas turbine blade leading-edge. However, the swirl strength of coolant decreases rapidly along the swirl chamber, and there exists a low heat transfer zone between two adjacent nozzles. Moreover, the downstream heat transfer is always reduced by the crossflow. To solve this problem, the concept of swirl cooling with crossflow diverter was proposed, and the velocity fields and heat transfer performance were investigated in this paper. Numerical simulations were performed by using 3D steady flow solver of Reynolds-averaged Navier-Stokes equations (RANS). The turbulence model validations were performed against both smooth swirl chamber and circular tube with circumferential ribs, and the validation results pointed out that the SST k-ω turbulence model had the highest accuracy in predicting the heat transfer in swirl chamber with diverters. To reveal the mechanism of crossflow suppression and heat transfer enhancement, the simulation results were compared with smooth swirl chamber under different Reynolds numbers. On this basis, the effects of crossflow diverter heights and locations were studied further. The results showed that for smooth swirl chamber, the swirl strength decayed linearly, and the heat transfer coefficients decreased rapidly, thus the high heat transfer zone cannot cover the whole region between these two adjacent nozzles. The circumferential velocity of the jet gradually decreased while the axial velocity increased, and the crossflow formed. Crossflow and downstream nozzle efflux produced interference effect. Because of friction effect, crossflow reduced the circumferential velocity of the downstream jets and made the jet deflect downstream. Thus, the high heat transfer area of the downstream target plane decreased sharply. For swirl chamber with crossflow diverters, the crossflow and downstream jets separated from each other. The ability of the downstream jet to penetrate the mainstream and scour the target surface was strengthened. Therefore, the heat transfer of the target surface near the downstream nozzle was enhanced. Higher Reynolds number contributed to a more obvious crossflow suppression and heat transfer enhancement effect.
Influence of the Contact Interfaces on the Dynamics and Power Flow Behavior of the Bolted Structure
Authors: Wang Yongfeng , Ma Yanhong , Hong Jie , Battiato Giuseppe , Firrone Christian Maria 
Published: October 2022

Abstract
Bolted joints are widely used for the assembly of mechanical components to provide continuity of the structure and transfer internal actions (i.e. forces and moments) from one member to another. Contact and dry friction at the jointed interface have a great influence on the dynamical performance of the assembly, especially for light-weight and heavy-loaded structures, such as the aero-engine.
In this paper, the nonlinear dynamic response of a turbo-engine casing in the presence of bolted flanges is studied, using one reduced order model of an elementary casing sector with means of node-to-node contact elements. while the vibration power flow method for the structural system with frictional interfaces is proposed, to reveal effects of energy dissipation at contact interfaces. It concluded that, the resonance frequencies and vibration responses of the bolted structures are influenced by the interfacial contact state, and the damping induced at the slipping contact area surrounding the bolt decreased the vibration response. Power flow through the bolted structure are visualized, which clarified the energy dissipation at the bolted interfaces.
Analysis of Melting and Solidification Behavior in DED Laser Welding of Inconel 901
Authors: Ali Ehtesham , Kwon Hwabhin , Lee Je-Hyun , Park Heesung 
Published: October 2022

Abstract
In this study, a transient simulation of laser welding is carried out using Directed energy deposition (DED) method for the 4mm thick Inconel 901 plate. Experimental and numerical simulation method are used to investigate the thermal behavior and solidification characteristics. Five different cases are investigated using COMSOL Multiphysics® software. The parameters used in this study are the laser power ranging from 550 W to 750 W and the laser scanning speed ranging from 6.67 to 10.0 mm/s. The cooling time between the melting and solidification process is evaluated in the region under the top surface of substrate for different laser power and laser scanning speed. Among the cases studied, D5 shows the highest temperature variation under top the surface of the substrate, followed by D2, D3, D4, and D1 has the lowest temperature due to lower laser power. The temperature variation under the top surface of substrate is also calculated for different conditions of laser assisted DED processes. The numerical simulation results are compared with the experimental results which are in good agreement and well validated. The obtained conclusions in this paper demonstrated that this numerical study of thermal behavior could provide a better understanding of the melting and solidification process inside the molten pool using laser assisted DED processes.
A Mechanistic Model for the Predictive Maintenance of Heavy-Duty Centrifugal Fans Operating With Dust-Laden Flows
Authors: Vulpio Alessandro , Oliani Stefano , Suman Alessio , Zanini Nicola , Saccenti Paolo 
Published: October 2022

Abstract
Heavy-duty centrifugal fans are employed for the transport of dust-laden flows in industrial plants, for cement or steel production, or in energy production plants and mine ventilation systems. These applications require the disposal of huge amounts of suspended particles which can lead to a gradual erosion of the machine parts where impacts take place. The wear of the fan components can lead to premature failure of the machine, threatening human safety and reliability of the whole plant. The assessment of the wear severity of the machine, according to the process parameters, can aid the plant owner in scheduling overhaul operations along with the operative life of the machine. Moreover, through a reliable estimation of the wear severity, fan manufacturers can optimize the whole machine design process, from the material selection to the warranty time assessment. The present work aims to develop a semi-empirical method capable of estimating the erosion severity of centrifugal fans employed for heavy-duty operations. A mechanistic model which accounts for the erosion on the blade leading edge is proposed. The model is derived by means of an analytical approach and accounts for a number of operating parameters (i.e., fan geometry, fan operating point, particle concentration in the flow, fluid properties, and material erosion resistance). A comparison of the theoretical model to the CFD results obtained through the use of multi-phase particle tracking is also provided to assess the reliability of the present method.
Effects of Ribbed Surfaces on Profile Losses of Low-Pressure-Turbine Blades
Authors: Dellacasagrande M. , Lengani D. , Simoni D. , Ubaldi M. , Bertini F. 
Published: October 2022

Abstract
In this work, streamwise oriented riblets were installed on a flat plate exposed to an adverse pressure gradient simulating the diffusing part of a low-pressure turbine (LPT) blade and, successively, on the suction side of an LPT cascade operating under unsteady inflow condition. Different riblets heights, spacings and positions have been tested, and complementary measuring techniques have been used to quantify their effects on the boundary layer evolution, and on losses. Experiments carried out on the flat plate allowed the detailed description of the riblet effects on the coherent structures developing within the boundary layer affecting transition, thus providing a rationale for the identification of the optimal riblet geometry once scaled in wall units. For riblet heights equal to about 20 wall-units, a maximum loss reduction of 8% was observed with respect to the smooth case. Otherwise, for larger riblet dimensions, earlier transition occurs due to enhanced boundary layer instability and losses significantly increase. Interestingly, the streamwise extension of the ribbed surfaces with respect to the transition region was found to play a minor role compared with the riblet dimension. The riblet configurations providing the highest reductions of viscous losses on the flat plate were then tested in the LPT blade cascade for different Reynolds numbers. In this case tests have been carried out with impinging upstream wakes. An overall reduction of the profile losses comparable to that observed in the flat plate case has been confirmed also in the unsteady operation of the turbine cascade. Low sensitivity of the profile losses to the riblet streamwise extension was also observed in the cascade application. This confirms that positive effects in terms of loss reduction can be obtained even when the exact transition position is not known a priori.
Analysis of Combustion Performance of Non-Conventional Syngas in mGT Combustor: Assessment of the Impact of the Quality of Synthesis Gas Towards Flame Stability and Emissions
Authors: Bompas Jérémy , Pappa Alessio , De Paepe Ward 
Published: October 2022

Abstract
The current limited availability of conventional fossil fuels, e.g., natural gas, as a result of the active demand in the industrial revival, leading to increasing prices as well as uncertainty and tension on the international market, strengthens the interest on energy source diversification to ensure sufficient sustainable resources for both heat and electricity demand. Non-conventional renewable resources like biogas, syngas, and biofuels are good candidates to achieve these energy mix goals, especially in a decentralized power production context, e.g., when used in micro Gas Turbines (mGTs) in small-scale cogeneration applications. Moreover, they also present the benefit of reducing CO2 emission and, while doing so, helping to move towards global zero emission by 2050. However, given their specific properties, i.e., a lower energy content, a lower overall conversion efficiency, different and altering composition, as well as an important steam fraction when not properly post-treated, a better characterize of these non-conventional energy sources in their combustion behavior is needed.
The aim of our work is thus to identify the combustion behaviour of several characteristic syngases in a typical industrial combustor, the Turbec T100 combustion chamber, designed for operation using natural gas. The performance of the combustor has been analysed using CFD calculations, under different syngas composition with increasing remaining steam fraction, aiming to determine the maximal allowable rest steam fraction, in an attempt to limit syngas post-treatment after production towards enhanced global cycle performance. In particular, the ignition and stability of the flame has been studied under a syngas pilot flame. To study this, velocity and temperature fields are analysed, as well as the specific flue gas composition. While the simulation results using dry syngas show temperature distributions and emission prediction in line with previous observation, the steam dilution effect leads to a clear shift in both temperature and emissions. More specifically, it is found that especially NOx emissions are sensible towards changes in pilot and main flame fuel distribution alterations. These obtained results will serve as benchmark for future characterization for a specific range of diluted inlet conditions of raw syngases, as well as specific studies on the impact of pilot/main flame fuel distribution towards flame stability and emissions control, which will allow to fully exploit their potential in small-scale cogeneration application.
Statistical Rule Extraction for Gas Turbine Trip Prediction
Authors: Bechini Giovanni , Losi Enzo , Manservigi Lucrezia , Pagliarini Giovanni , Sciavicco Guido , Stan Ionel Eduard , Venturini Mauro 
Published: October 2022

Abstract
Gas turbine trip is an operational event that arises when undesirable operating conditions are approached or exceeded, and predicting its onset is a largely unexplored area. The application of novel artificial intelligence methods to this problem is interesting both from the computer science and the engineering point of view, and the results may be relevant in both the academia and the industry. In this paper we consider data gathered from a fleet of Siemens industrial gas turbines in operation that include several thermodynamic variables observed during a long period of operation. To assess the possibility of predicting trip events, we first apply a new, systematic statistical analysis to identify the most important variables, then we use a novel machine learning technique known as temporal decision tree, which differ from canonical decision tree because it allows a native treatment of the temporal component, and has an elegant logical interpretation that eases the post-hoc validation of the results. Finally, we use the learned models to extract statistical rules. As a result, we are able to select the 5 most informative variables, build a predictive model with an average accuracy of 73%, and extract several rules. To our knowledge, this is the first attempt to use such an approach not only in the gas turbine field, but also in the whole industry domain.
Investigating the Nature and Invariance of Field Inversion Based on Transition in a Turbine Cascade
Authors: Bleh Alexander , Backhaus Jan , Morsbach Christian 
Published: October 2022

Abstract
The generation of data-driven turbulence models inherently requires the use of a sufficiently large database of high-fidelity reference data from DNS or LES. For technically relevant flows, such data is usually not readily available. However, in many cases there is a significant amount of experimental data available, though data points are mostly few and sparse. An approach which aims at deriving modelling errors by evaluating deviations from a given reference data set is the field inversion method proposed in [1]. Our aim is to verify this method as a tool which gives insight in the cause and nature of a given model’s inconsistencies. We therefore apply field inversion on the turbine cascade T106C for different reference data setups. We find, that for the investigated case, field inversion proved to qualitatively give the right hints towards the expected model correction, when only few data points were used as reference.
Windage Loss and Flow Characteristics in Impeller Back Clearance of sCO2 Centrifugal Compressor
Authors: Hu Lehao , Deng Qinghua , Li Zhigang , Li Jun , Feng Zhenping 
Published: October 2022

Abstract
In this paper, the windage loss and the flow characteristics in impeller back clearance divided into disk-type and shaft-type clearance for sCO2 compressor are investigated by numerical method. The effects of rotation speed, inlet pressure and disk-type clearance width on the windage loss and flow characteristics are analyzed in detailed. Through detailed numerical verification, realized k-ε turbulence model is finally selected, and all simulations are performed under the condition of the rotation speed of 20 ∼ 60 kr/min and inlet pressure of the 9 ∼ 12 MPa, respectively. The study results show that windage loss in disk-type clearance increases with rotation speed and inlet pressure increasing, and the influences of rotation speed on windage loss are more obvious than that of inlet pressure. Both the flow instability and more vortexes at inlet become main reasons why windage loss increases. The relative deviations of 105% ∼ 217% between Daily’s loss model results and simulated results indicate that loss model is not applicable to predict the windage loss. What more, the windage loss in shaft-type clearance is basically increases linearly with the rotation speed and inlet pressure increasing. The proportion of windage loss in shaft clearance to total loss ranges from 9% to 16%, which indicates the windage loss in shaft-type clearance can be neglected for the preliminary design on sCO2 compressor. In addition, the maximum relative deviation of 2 % for the leakage model can be completely applicable to the design of sCO2 compressor. Disk-type clearance width has significant influence on both loss and flow characteristics. The windage loss in disk-type clearance decreases with the clearance width increasing, and the variation rate of windage loss increases as the clearance width increases. Larger width makes number of vorticities decrease at turning angle and changes flow direction easily, which is favorable to decrease windage loss. Finally, Daily’s loss model is modified and the modified loss model is validated. The maximum relative deviation of 17% for modified loss model is completely accepted, which indicates the modified loss mode can substantially improve accuracy of calculating windage loss in the impeller back clearance of sCO2 centrifugal compressor.
Quantification of Autoignition Risk in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor and Surrogate Modelling
Authors: Iavarone Salvatore , Gkantonas Savvas , Jella Sandeep , Versailles Philippe , Yousefian Sajjad , Monaghan Rory F. D. , Mastorakos Epaminondas , Bourque Gilles 
Published: October 2022

Abstract
The design and operation of premixers for gas turbines must deal with the possibility of relatively rare events causing dangerous autoignition. Rare autoignition events may occur in the presence of fluctuations of operational parameters, such as temperature and fuel composition, and must be understood and predicted. This work presents a methodology based on Incompletely Stirred Reactor (ISR) and surrogate modelling to increase efficiency and feasibility in premixer design optimisation for rare events. For a representative premixer, a space-filling design is used to sample the variability of three influential operational parameters. An ISR is then reconstructed and solved in a post-processing fashion for each sample, leveraging a well-resolved CFD solution of the non-reacting flow inside the premixer. Via detailed chemistry and reduced computational costs, the evolution of autoignition precursors and temperature, conditioned on a mixture fraction, is tracked, and accurate surrogate models are trained on all samples. The final quantification of the autoignition probability is achieved by querying the surrogate models via Monte Carlo sampling of the random parameters. The approach is fast and reliable so that user-controllable, independent variables can be optimised to maximise system performance while observing a constraint on the allowable probability of autoignition.