bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Data Driven Method for the Derivation of Explicit Algebraic Reynolds Stress Models Applied to the Wake Losses of Low-Pressure Turbine Cascades
Authors: Deutsch Johannes , Fard Afshar Nima , Henninger Stefan , Jeschke Peter 
Published: August 2024

Abstract
This paper introduces and validates a data-driven approach to improve the prediction of linear eddy viscosity models (LEVMs). The general approach is adopted in order to improve the wake mixing of low-pressure turbine (LPT) cascades. The approach is based on the modification of the Boussinesq assumption. It follows the rationale applied in the derivation of explicit algebraic Reynolds stress models (EARSMs) by including additional second-order tensors, as suggested by Pope [1]. The unknown scalar functions that determine the contributions of each second-order tensor to the Reynolds stresses are approximated as polynomials. A metamodel-assisted multi-objective optimization determines the value of each of the polynomial coefficients. The optimization minimizes the difference between the result of the EARSM simulation and reference data provided by a high fidelity large eddy simulation (LES).
In this study, tailor made EARSMs are calibrated in order to improve the prediction of the kinetic energy loss distribution in the wake of the T106C LPT cascade with an isentropic Reynolds number of 80 000. We showed that the wake losses predicted by state of the art Reynolds-averaged Navier-Stokes (RANS) turbulence models cannot reproduce the reference LES data. In the following, we investigated the influence of each polynomial coefficient of the EARSM on the flow solutions within a sensitivity study. The models generated by the approach reduced the deviations in turbulent kinetic energy loss between the LES reference solution and the baseline model by approximately 70 %. The turbulent quantities are analyzed to identify the physical correlations between the model inputs and the improvement. The transferability of the models to unseen test cases was assessed using the MTU-T161 LPT cascade with an isentropic Reynolds number of 90 000. A decrease of up to 80% is achieved regarding the deviations between the LES reference and the baseline RANS model.
In summary, the suggested approach was able to generate tailor made EARSM models that reduce the deviations between RANS and LES for the mixing of turbulent wake flows.
A Review of Secondary Combustion on Turbine Blade Cooling
Authors: Ngwenya Tinashe , Nava Antonino , Ireland Peter T. 
Published: August 2024

Abstract
The gas turbine engine is the powerhouse of most large modern military and civil aircraft. These engines operate at temperatures above the melting point of the materials that the combustor and turbine components are made from. Film cooling is used extensively to cool the hot surfaces and extend the life of the gas turbine’s hot end components. In some modern and future engines, the average turbine inlet temperature is increased to about 2,400K and the length of the combustor is reduced. The turbine inlet temperature is increased to improve the thermal efficiency while the combustor is shortened to increase the thrust-to-weight ratio. Both developments are meant to reduce the amount of fuel burnt and the operational cost of the power plant. Increasing the turbine inlet temperature to above 1,850 K CO2 dissociation starts to compete with CO oxidation. Reducing the combustor length reduces the residence time of fuel and increases the likelihood of unburnt hydrocarbons entering the turbine. When carbon monoxide and/or unburnt hydrocarbons enter the turbine, they could react with oxygen in the cooling air and potentially increase the blade metal temperature. An increase of about 30 K can reduce the blade life by half: secondary combustion of reactive species entering the turbine section could therefore lead to serious durability concerns. In a review of the literature, it was found that an estimated 10% of fuel energy is available for combustion in the turbine section and a maximum heat flux augmentation of 18% due to secondary combustion occurs. Secondary combustion in the turbine components is reviewed through a discussion of the analysis of reactive film cooling, developments driving the need to develop an in-depth understanding of reactive film cooling, scaling of reaction kinetics and heat release potential, performance of cooling hole geometries and configurations and mitigation strategies.
A Review of Numerical Methodologies for Predicting Rotating Stall and Surge in High-Speed Centrifugal Compressors
Authors: Neri Francesco , Hickel Stefan , Pini Matteo 
Published: August 2024

Abstract
High-speed supersonic radial compressors are a critical enabling technology for meeting the requirements of future aviation-propulsion and thermal-management systems. These turbomachines must be designed to be both efficient and robust on the widest possible operating range. Flow instabilities in the form of rotating stall and surge are therefore phenomena that must be accurately predicted early in the design process. Unsteady full-annulus computational fluid dynamics can be used to get accurate information about the onset of instabilities, but at the expense of costly simulations. As a result, the design of new compressors continues to rely on existing correlations for the prediction of the critical mass flow rate. This approach, however, leads to sub-optimal compressor designs.
This article provides a review of the numerical methodologies that can be used for the accurate prediction of the critical mass flow rate in high-speed centrifugal compressors. Methods of different fidelity level and computational cost are described. Two particularly promising models, namely those proposed by Spakovszky and Sun, are subsequently examined in more detail. Exemplary applications of these two models are finally discussed.
Combustor Design From a Turbine Perspective to Minimize the Effect of Turbulence
Authors: Miklaszewski Jennifer A. , Folk Masha B. , Hamlington Peter E. 
Published: August 2024

Abstract
During the gas turbine design process, control and optimization of turbulence characteristics at the combustor-turbine interface can lead to improved specific fuel consumption. Here, we use computational large-eddy simulations to explore the turbulent flow characteristics at the exit plane of two combustor designs: a baseline design corresponding to an idealized non-reacting combustor simulator and a design that has been optimized to minimize turbulence intensity at the combustor exit while maintaining good mixing uniformity and low pressure drop. By comparing the two designs, we demonstrate that the size, orientation, and positioning of the primary zone and dilution jets are the primary drivers determining turbulence characteristics at the combustor exit. We show that by modifying the combustor geometry we can shift the energy-containing eddies to larger scales, affecting both the turbulence decay rate and the interaction of turbulence with the turbine boundary layer. In the optimized design, turbulence decays at a faster rate towards isotropic flow and we observe that Reynolds stresses are substantially decreased. We introduce a flat plate with a tapered leading edge downstream of the combustor exit to quantify the subsequent boundary layer profile, skin friction, and boundary layer dissipation for each design. This work illustrates how understanding the mechanisms responsible for decreased turbulence at the combustor exit can aid designers in maximizing performance of gas turbines, as well as demonstrating the potential of computational optimization for combustor design.
Innovative Synergies in Aircraft Propulsion: the Concept of Hybrid Power Systems With Contra-Rotating Propellers
Authors: Hazeri Majid , Moradkhani Mohsen , Rashid Jafari Javad , Asadi Davood 
Published: August 2024

Abstract
In an era characterized by escalating emphasis on fuel economy and the mitigation of greenhouse gas emissions within the aerospace industry, this paper presents an innovative paradigm including the hybrid electric engine with contra-rotating propellers. This article unveils a pioneering technological achievement, exemplified by our patented invention registered under the identifier IB/2021/060538, which received a gold medal at the ICAN 2022 International Invention competition in Toronto, Canada, represents a noteworthy advancement in the domain of hybrid engine technology. It is imperative to acknowledge that the concept is currently in the conceptual design phase, necessitating further refinement to attain its maximum potential. The engine, characterized as a contra-rotating propeller system, engenders an efficiency gain ranging from 6% to 16% relative to single-fuel engines, with one internal combustion engine providing half of the required power and the electric motor complementing the remaining share. This innovative system comprises two distinct configurations: a system with two electric motors and one fuel engine in which one of the electric engines is used as a backup engine. In case of user preference or fuel engine failure, the backup electric is engaged in place of the fuel engine. This paradigm-shifting innovation effectively changes the conventional internal combustion engine into a multi-engine anti-torque system, facilitating augmented thrust generation while simultaneously reducing fuel consumption by an impressive margin of 40% to 60% when compared with conventional engine models. Beyond its commendable fuel efficiency, the hybrid engine is characterized by a satisfactory level of reliability. This is related to the inclusion of a backup electric motor. In addition to the internal combustion engine, supporting the system with the ability to manage system failures and maintain power output even under emergency circumstances. Notably, the fundamental concept of the contra-rotating propeller system is not entirely novel, however, our innovative approach harmoniously synchronizes two electric motors, thereby containing the advantages inherent in the contra-rotating system with the reliability attributed to electric propulsion.
Effects of Localized Non-Gaussian Roughness on High Pressure Turbine Aero-Thermal Performance: Convective Heat Transfer, Skin-Friction and the Reynolds’ Analogy
Authors: Jelly Thomas O. , Nardini Massimiliano , Sandberg Richard D. , Vitt Paul , Sluyter Greg 
Published: August 2024

Abstract
Compressible direct numerical simulations are conducted to investigate how surface roughness affects the aero-thermal performance of a high pressure turbine vane operating at an exit Reynolds number of 0.59 × 106 and exit Mach number of 0.92. The roughness under investigation here was synthesized with non-Gaussian statistical properties and an amplitude that varies over its chord length — representative of what truly occurs on an in-service vane. Particular attention is directed towards how systematically changing the axial extent of leading edge roughness affects convective heat transfer (Nusselt and Stanton numbers) and aerodynamic drag (skin-friction coefficient) on the pressure and suction surfaces. The results of this investigation demonstrate that moving the larger amplitude roughness further along the suction surface can alter the blade boundary-layer state. In fact, towards the trailing-edge of one of the rough vanes investigated here, the local skin-friction coefficient increases by a factor of twenty-two compared to smooth-vane levels, whereas the local Nusselt number increases by a factor six. The disproportionate rise of drag compared to heat transfer is explored in further detail by quantifying the Reynolds’ analogy and by calculating the fractional contributions of pressure drag and viscous drag to the total drag force. The effect of varying the inlet turbulence intensity and integral length-scale for a fixed roughness topography is also investigated, and the Reynolds-number scaling of heat transfer and drag is examined in the context of the Chilton-Colburn analogy.
Effect of Blockages on Film Effectiveness on the Pressure Surface of a Turbine Blade
Authors: von Mueller Tassilo , Bacci David , Wambersie Augustin , Wong Tsun Holt , Ireland Peter , Jackson Dougal 
Published: August 2024

Abstract
An experimental and numerical study was conducted on fan-shaped holes on the pressure surface of a high-pressure turbine blade. Blockages in these film holes can arise through dirt accumulation as well as erosion of the thermal barrier coatings. The objective was to study the effects of partial blockages on film cooling effectiveness. Similar studies have been conducted on flat surfaces. This study includes the effect of curvature, which has been shown to be influential on film cooling performance. A blade with a single row of nominal fan-shaped holes at a lateral inclination of 30° was tested and used as the baseline performance. Blockage cases were then tested at various blowing ratios, with partial blockages in the throat as well as partial lidding in the fan exit of the film hole. The experiments were carried out using Pressure Sensitive Paint (PSP) in the high velocity 2D linear cascade experimental facility at the Oxford Thermofluids Institute, using engine representative Mach and Reynolds numbers. The results show that lidding with up to 0.5 blocking ratio (defined as the ratio of lidded length to the length of the film hole exit, in the film hole plane) only has a minor impact on film effectiveness, while lidding with 0.75 blocking ratio as well as throat blockage both result in significant deterioration of film cooling effectiveness. The effect of blockages on discharge coefficient was also studied and only blockages in the throat were found to reduce discharge coefficient.
Robust Design Optimization of a Compressor Rotor Using Recursive Cokriging Based Multi-Fidelity Uncertainty Quantification and Multi-Fidelity Optimization
Authors: Wiegand Marcus , Prots Andriy , Meyer Marcus , Schmidt Robin , Voigt Matthias , Mailach Ronald 
Published: August 2024

Abstract
This work focuses on the application of multi-fidelity methods for the robust design optimization of engine components. The robust design optimization approach yields geometric designs that have high efficiencies and are less sensitive to uncertainties from manufacturing and wear. However, the uncertainty quantification techniques required to evaluate the robustness are computationally expensive, which limits their use in robust optimization. Multi-fidelity methods offer a promising solution to reduce the computational cost while maintaining the accuracy in both uncertainty quantification and optimization.
A Kriging and a multi-fidelity recursive Cokriging framework are developed, implemented, and applied to a test function. In addition, a multi-fidelity super efficient global optimization algorithm is developed. The optimizer is surrogate model-based and can handle constraints. The developed methods are then applied to a compressor test case of a high pressure compressor blade row with 9 uncertainty and 24 design parameters of the geometry. The 2.5 % quantile of the stage efficiency is used as a robustness measure and it is therefore optimized. Design bounds and performance constraints are applied. In addition, various uncertainty quantification techniques are analyzed. A multi-fidelity uncertainty quantification approach is developed that combines simplified coarse-grid low-fidelity results with high-fidelity results to reduce the computational cost while maintaining a high accuracy. Uncertainty quantification techniques of three fidelity levels are then developed and used for the multi-fidelity approach in the design space. The robust design optimization of the compressor is performed and the optimal designs obtained from the multi-fidelity approach show superior performance compared to existing robust design optima in the literature.
Analysis of Pumped Hydro Storage Using Mines As Hydro Reservoirs
Authors: Castorino Giulia Anna Maria , Dahlquist Erik , Kyprianidis Konstantinos , Losi Enzo , Manservigi Lucrezia , Pinelli Michele , Renuke Avinash , Spina Pier Ruggero , Venturini Mauro 
Published: August 2024

Abstract
Pumped hydro storage (PHS) is the most mature and widely used technology for large-scale energy storage. Hydropower plants are in fact also employed for this aim. However, most hydraulic sites suitable for this purpose have been already exploited. Therefore, the use of abandoned mines represents an alternative solution to take advantage of the availability of underground volumes as hydro storages.
This paper investigates the potential of PHS plants integrated within a power generation system that comprises both programmable (e.g., hydropower and nuclear power plants) and non-programmable (e.g., wind and solar power plants) energy systems. All systems are connected with the power grid.
To this purpose, this paper develops a methodology aimed at identifying the optimal sizing of the PHS plant as well as the optimal operation of the whole power generation system at Country level, with the goal of minimizing the imported energy.
The methodology is validated by using Sweden as the case study, to assess the energy and economic feasibility of PHS plants in 2050. Different future scenarios of electricity production, demand, and cost are analyzed.
The analyses carried out in this paper demonstrate that PHS plants are highly recommended if the cost of imported energy is expected to increase. In such a scenario, PHS is mainly employed to meet domestic electricity demand.
GPU Accelerated LES-FGM Modelling for Industrial Combustion Applications
Authors: McManus Liam , Goldin Graham , Zhang Yongzhe , Veljkovic Ivana , Sadasivuni Suresh , Liu Kexin 
Published: August 2024

Abstract
Due to the ever-increasing use of Large Eddy Simulation (LES) for assessing gas turbine combustor flow and mixing fields, flame position and flame dynamics, methods to reduce the computational costs of such simulations are desirable. One such method to achieve this is to utilize advanced High Performance Computing (HPC) architectures such as General Purpose Graphical Processing Units (GPGPUs).
In this paper, the Simcenter STAR-CCM+® solver, with the ability to run LES and flamelet based combustion models using GPUs, is used to assess the benefits of using GPU architecture compared to traditional Central Processing Units (CPUs). LES simulations using the Flamelet Generated Manifold (FGM) combustion model are assessed across a series of test cases: A diffusion jet flame, a pressurized annular combustor and a swirl stabilized industrial gas turbine Dry Low Emission (DLE) combustor provided by Siemens Energy Industrial Turbomachinery Ltd, Lincoln, UK.
Numerical simulations using GPUs and CPUs are compared in terms of solution similarity, accuracy in relation to experimental data, computational cost and power consumption. The computational performance of the FGM model with GPU is quantified through comparison to a non-reacting simulation on the same computational grid.
It is demonstrated that the use of GPU architectures can result in high-fidelity combustion modelling within the required turn-around times of engineering design cycles whilst maintaining a similar solution and level of accuracy as a traditional CPU based simulation.
Supercritical Carbon Dioxide Mixing Loss Characteristics Near the Critical Point
Authors: Wang Jinhong , Cao Teng , Martinez-Botas Ricardo 
Published: August 2024

Abstract
This paper aims to study the mixing loss characteristic of sCO2 near the critical point and shed light on the non-ideal fluid effect on the mixing losses. As a simplified model of the mixing process in the trailing edge or tip leakage flow in turbomachines, a case of mixing in a constant area adiabatic duct involving two streams of parallel flows is studied by control volume analysis. Both perfect gas and non-ideal fluid calculations are carried out for comparisons. The isolated and coupled effects of the two mixing streams’ temperature, velocity, and pressure differences on the loss are investigated. The study shows that non-ideal fluid mixing produces significantly higher losses when compared to the equivalent perfect gas estimation. It also reveals that the non-ideal fluid mixing loss is sensitive to the average thermodynamic states of the mixing streams. A general trend is that the closer the temperature is to the critical point, the higher the loss is observed. This is particularly apparent for the temperature and pressure mixings, while the mixing loss due to the velocity difference is less affected. A significant variation of the mixing loss coefficient is reported if the static state of any of the two streams is near the critical point, which is mainly caused by the significant variation of the temperature gradient regarding the entropy along the isobar. In addition, a positive combined effect of the temperature, velocity, and pressure differences was found for mixing loss. The results also show that the change in the mixing loss due to the variation of one property difference between mixing streams is almost independent of the other property difference. This behaviour matches the conclusion drawn in literature for perfect gases [1]. The results from this simple case contribute to understanding the mixing loss behaviour differences between perfect gas and non-ideal fluids in sCO2 turbomachinery and hold significance for the development of mean-line models.
Numerical Modelling Approach for Wet Humid Air Flows in Hydrogen E-Turbos
Authors: Tosun Adem , Fuhrer Christopher , Hughes Stephen , Vogt Damian M. 
Published: August 2024

Abstract
A numerical modeling approach for predicting phase transition in rapid expansions of humid air is derived. For this purpose, the well-established classical theory of condensation in wet steam flows is extended to the multicomponent flow environment. The proposed model equations for nucleation and droplet growth in humid air account for the presence of a non-condensable flow component. An Euler-Euler framework is used alongside the commercial flow solver ANSYS CFX to calculate the two phase flow. The model is validated against supersonic nozzle test cases with pressure measurements available in open literature. The onset and thermodynamic impact of phase transition is predicted with reasonable accuracy regarding the pressure distributions. Finally, the phase transition model is applied to the radial turbine stage of a fuel cell e-turbo. Droplet formation inside the turbine and the impact of phase transition on the turbine performance are discussed.
Smoke Point Is Adequate for Engineering Soot Prediction: A Demonstration
Authors: Krishnasamy Bharathi Arvind , S. Varunkumar 
Published: August 2024

Abstract
A semi-empirical Laminar Smoke-Point (LSP) model is used to compare soot predictions against the experimental Laser-Induced Incandescence (LII) based measurements in a lab-scale CFM-56 aircraft combustor with liquid jetA1 as fuel and dilution jets. The soot model, which has so far been used in the fire dynamics domain for laminar flames, has now been extended to an industrial burner using LES. Comparison of the averaged Discrete Phase Model (DPM) droplet distribution against the backlight spray imaging shows a good comparison. The simulation displays some degree of spray asymmetry similar to the data due to the wall confinement effect. A comparison of the thermal field with the instantaneous flame image shows a good match in terms of the radial and axial extent of the flame front. Finally, a comparison of the soot volume fraction predicted by the model with the LII data shows an acceptable qualitative and good quantitative match. The soot field immediately downstream of the swirler shows a near-uniform soot field at an angle of about 98° which is close to the measured spray angle. The radial extent of the soot at the widest section matches closely with the data. However, the model predicts an axial extension of the soot further downstream and up to the dilution jets which is not observed in LII. This could be due to the presence of Poly-Aromatic Hydrocarbons (PAH) in these regions which are not picked up in LII due to the spectral filter or could be due to the laser sheet attenuation by the liquid fuel on the quartz window.