bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Additively Manufactured Two-Fluid Heat Exchanger Designed With Topology Optimization Tools
Authors: Caruso Claudio , Morante Francesco , Pampaloni Giacomo , Rossin Stefano , Canova Alessandro , Casari Nicola , Rees Thomas 
Published: August 2024

Abstract
Heat exchangers are widely used in gas turbine plants for several purposes, with traditional designs including shell and tube or plate-fin coolers. Recent developments in additive manufacturing techniques such as laser powder bed fusion have led to interest in the use of alternative heat exchanger designs, such as those generated with topology optimization techniques. These design techniques can result in more efficient heat exchangers with complex internal structures which can only be manufactured using additive techniques. Nevertheless, manufacturing heat exchangers for gas turbine applications with additive techniques is not straightforward. Two of the primary difficulties in the use of laser powder bed fusion are the printing of materials with high thermal conductivity such as copper alloys as well as powder cleaning from any complex internal channels such as those which may be generated by topology optimization tools.
To investigate the feasibility of combining topology optimization techniques with additive manufacturing to design novel heat exchangers a proprietary topology optimization software is used to design an oil/air cooler with significantly reduced size and pressure drop compared to an equivalent one based on a conventional design. In a potential future application on oil circuits, this could consequently result in an optimization of the lubricant oil circuit components, for example pumps, piping, console dimensions and weight. The design was also optimized to consider manufacturability constraints such as overhang angles and minimum thickness as well as to correct in line with feedback from initial trial prints. The cooler was manufactured using additive manufacturing techniques.
Numerical Investigation of the Effect of Diffusion Factor Variation on the Performance of Single-Row and Tandem Bladings in Low-Speed Axial Compressor Stages
Authors: von Jeinsen Philipp , Giannini Samuele , Gümmer Volker 
Published: August 2024

Abstract
The use of tandem blade configurations in axial compressor stages offers designers the opportunity to achieve higher work coefficients, which in turn allows for the creation of smaller compressors. However, tandem airfoils introduce a more complex flow field compared to their single airfoil counterparts, often resulting in a decrease in stage efficiency.
This paper aims to investigate the aerodynamic performance of single and tandem airfoils across a wide design space represented by the “Smith Chart” (work coefficient vs. flow coefficient). A prior study indicated that tandem stages exhibit superior efficiency when DeHaller numbers are low. However, this comparison was conducted under strict design conditions, leading to suboptimal diffusion factors for various designs and impairing the comparison of their off-design performance. The current study seeks to address this limitation by examining the effects of varying the diffusion factor and ensuring comparability in off-design behavior.
The 3.5-stage low-speed axial research compressor at the Institute of Turbomachinery and Flight Propulsion at the TUM sets this study’s geometrical and aerodynamic baseline. The first 1.5 stages of this compressor will be redesigned, either considering a set-up of IGV, single rotor, and single stator or a set-up of IGV, tandem rotor, and tandem stator. The numerical analyses are based on the throughflow – B2B coupled quasi-3D design process.
The first part of the paper presents a brief overview of the methodological approach and highlights the necessary changes to the design procedure compared to the prior investigation. The second part explores the effect of diffusion number variation on the midspan airfoils across the entire design space. These findings lead to the final part of the paper, where the efficiency maps of single and tandem stage configurations are compared.
The present paper confirms that the potential efficiency gain of tandem airfoil geometries over single ones largely depends on the DeHaller number of each row. Single airfoil configurations demonstrate superior performance at high DeHaller values, while tandem airfoils excel at low DeHaller numbers, potentially unlocking a design space with increased work coefficients.
Water-Based Yttrium Additive for Hot Corrosion Inhibition in a Gas Turbine
Authors: Selim Hatem , Suleiman Baha , Dawood Alaaeldin , Montagne Pierre , Amancherla Sundar , Khalidi Abdurrahman 
Published: August 2024

Abstract
Hot corrosion is a major problem for operating gas turbines running on vanadium-laden liquid fuels. Upon combustion, vanadium combines with oxygen forming vanadium pentoxide (V2O5) which is highly corrosive and has a melting point below the hot gas path (HGP) operating temperature. This causes V2O5 to melt down and attack the HGP parts in what is known as hot corrosion. To mitigate the potential for hot corrosion of vanadium on gas turbine parts, a corrosion inhibitor is typically injected with the fuel. The role of the corrosion inhibitor is to chemically react with V2O5 to form non-corrosive chemical molecules, which appear as “ash”. Magnesium-based inhibitors are commonly used in gas turbine applications. However, a high volume of ash accumulates on turbine blades causing degradation of the turbine performance. A promising alterative, which is a yttrium-based inhibitor, was tested and compared with magnesium-based inhibitor in this investigation. Laboratory-scale testing of ash formation and corrosion inhibition were conducted for both inhibitors. The results proved that yttrium inhibitor achieved superior performance in comparison to magnesium inhibitor in terms of less ash formation and higher hot corrosion resistance. Furthermore, both inhibitors were tested in an E-class gas turbine pilot test. The acquired performance data confirmed the superiority of yttrium as an inhibitor in comparison to magnesium.
Experimental Evaluation of Combustor Configuration’s Impact on a Swirl-Assisted Jet-Stabilized Combustor Performance
Authors: Izadi Saeed , Zanger Jan , Seliger-Ost Hannah , Kutne Peter , Aigner Manfred 
Published: August 2024

Abstract
A major challenge for gas turbine combustor technology is the emission of NOx and CO. Achieving an optimal premixed, prevaporized, dry low-NOx condition is a critical issue for liquid fuel combustors. To accomplish this, the relationship between combustor configuration and the performance of a newly developed swirl-assisted jet-stabilized combustor is investigated in an atmospheric combustion facility. The combustor consists of a pressure-swirl fuel atomizer, a prefilmer/mixing channel, an axial moderate swirler (swirl number = 0.6), and a jet nozzle. The jet nozzle allowed for bulk velocities of 50–130 m/s. The influence of each combustor component on combustion performance and fuel evaporation behavior is evaluated independently using optical combustion diagnostics. In addition, the effect of air and liquid fuel temperature on fuel evaporation is characterized. Jet A-1 was injected coaxially into the air stream under both spray and superheated conditions. During the experiments, five critical combustor components were varied to understand their individual effect on fuel vaporization and thus combustion performance. Exhaust gas emissions of NOx, CO and UHC as well as OH* chemiluminescence images were used to evaluate combustor performance. Mie scattering technique was used to analyze the degree of liquid fuel evaporation for different test cases. It was found that the combustion performance indicators CO, height above burner and flame length were well controlled by the degree of fuel evaporation, while NOx emissions showed little change with different combustor configurations. While the main factor influencing the level of NOx emissions was the adiabatic flame temperature, the quality of fuel evaporation played a minor role. It was found that the operating range of the combustor and the geometric shape of the flame are significantly influenced by the components of the combustor.
Efficient Quantification of Aerodynamic Performance Uncertainty due to Geometric Variability Using an Adjoint Method
Authors: Zhang Qian , Xu Shenren , Meng Dejun , Wang Dingxi , Huang Xiuquan 
Published: August 2024

Abstract
Manufactured compressor blades deviate from their intended design, leading to a shift in the mean and scattering of aerodynamic performance. To mitigate performance deterioration without escalating manufacturing costs, accurate and efficient evaluation of aerodynamic uncertainty, known as uncertainty quantification (UQ), is crucial. The computational cost of three-dimensional computational fluid dynamics (CFD) simulations has prompted UQ studies to predominantly target two-dimensional cases or extend to three dimensions with a limited number of geometric variables. Since geometric deviations exist at various positions on three-dimensional blades, accurately describing them would necessitate a geometric deviation space with a large number of dimensions. To investigate high-dimensional uncertainty problems, an efficient adjoint-based UQ method is proposed and demonstrated using the three-dimensional transonic fan, NASA Rotor 67. The method proves to be not only hundreds of times faster than full-fidelity CFD but also yields results with satisfactory accuracy. The investigation into the underlying mechanism reveals that geometric uncertainties significantly influence shock waves, tip clearance vortices, corner vortices, and the radial distribution of three-dimensional flows, ultimately resulting in deviations in aerodynamic performance.
Enhancing Diagnostic Capability by Utilization of Twin-Engine Aircraft Configuration Aspects
Authors: Stenfelt Mikael , Desalegn Fentaye Amare , Kyprianidis Konstantinos 
Published: August 2024

Abstract
Depending on the data available, gas turbine diagnostics may be performed in various ways. For model based diagnostics methods, the most common data to use is from steady state operation. Regarding the amount of data, the smallest dataset comprise of a single operating condition for a specific gas turbine. The other end of the scale considers a fleet of engines, where data can be utilized for cross comparisons and identification of deviations in engine operation. In-between these two extremes, twin-engine airplanes can be utilized to obtain additional diagnostic information.
In this paper, a multi-point diagnostic method for a twin-engine airplane is developed and evaluated. It is based on the assumption that one engine can be operated individually for data collection, by varying the bleed flow extraction, while the other engine supply the airplane subsystems with the required bleed flow during the data collection time. The collected data then goes into a multi-point optimization which minimizes the difference between the health parameter estimations. From the health parameters, measurements corresponding to a reference operating condition are obtained and used by a data-driven classifier for fault identification and isolation. The method has proven to be able to detect both single and double component faults with high accuracy for the evaluated dataset.
Metal Fuel Combustion Tests Using NRCan’s 0.3 MWth Vertical Combustor Research Facility
Authors: Ilinich Margarita , Zanganeh Kourosh , Shafeen Ahmed , Staneva Katrin 
Published: August 2024

Abstract
Reactive metals, such as iron (Fe) and aluminum (Al), have high energy density, making them a potentially suitable candidate for partial replacement of hydrocarbon fuels. These materials, herein referred to as metal fuels (MeFs), have the potential to simultaneously produce heat and power, zero-carbon hydrogen (H2), and other value-added products. To this end, the role of MeFs for producing clean hydrogen is becoming increasingly important for achieving 2050 net-zero emission targets and industrial decarbonization.
To date, limited work has been done to demonstrate MeF combustion at pilot scale. In this paper, the preliminary results of MeF combustion using the 0.3 MWth Vertical Combustor Research Facility (VCRF) of Natural Resources Canada (NRCan) are presented. This facility was originally designed for advanced research on combustion of fossil fuels, including air- and oxy-combustion of solid, liquid, and gaseous fuels with CO2 capture, but has been recently retrofitted to be utilized for combustion of MeFs. The VCRF is equipped with a full range of instruments to monitor and record combustion process parameters in real time. These include combustion air flow, combustor pressure and temperature profile, as well as the flame shape and size (with the aid of a camera probe). This paper presents the results of co-firing of natural gas with two Fe powders (90 μm and 40 μm). The feedstock MeF powders were analyzed through particle size distribution (PSD) and scanning electron microscopy (SEM), to study the size, shape, and morphology of the particles. The preliminary tests with low MeFs firing rate showed promising results and further testing is ongoing with increased firing rate up to 0.3 MWth. The gaseous combustion products were measured by continuous emission monitoring (CEMs) analyzers during the tests, and solid particles were collected and characterized using SEM, energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD).
Combustion Instability Detection Based on Multi-Signal Information Fusion for an Industrial Gas Turbine Combustor
Authors: Fu Yanni , Zhang Yuming , Zang Peng , Sui Yongfeng , Zheng Yao , Xia Yifan 
Published: August 2024

Abstract
Combustion instability is a major challenge for low emission combustors. It is caused by the coupling between the combustor acoustic modes and heat release fluctuations. Early detection of combustion instability is very important for the safety and reliability of gas turbines. In this work, high-pressure and high-temperature experiments were conducted to investigate the thermoacoustic features of an industrial-scale combustor. The combustor contains a pilot burner and a main burner, which adopt diffusion and premixed combustion, respectively. The transition processes of thermoacoustic state from stable to unstable are experimentally studied for different operating pressures. Recurrence quantification analysis (RQA) is used to study the nonlinear dynamics of the dynamic pressure (DP) and acceleration (ACC) signals obtained during the experiments. Based on multi-signal information fusion of DP and ACC, an early detection method of combustion instability is proposed via a machine learning method. The proposed method combines the dynamic behaviors of DP and ACC signals into a two-dimensional map. A support vector machine (SVM) model is used to classify the thermoacoustic states of the combustor. Four cases are used to train the SVM model, while two additional cases are applied to assess the robustness of the SVM-based precursor. Compared to the conventional method based on the root-mean-square (RMS) of the DP signals, the SVM-based precursor achieves an overall accuracy of the early detection of combustion instability in the combustor.
A Method to Develop Radial Inflow Turbine Performance Maps for Off-Design and Dynamic Simulation Studies of sCO2 Cycles
Authors: du Sart Colin , Rousseau Pieter , Laubscher Ryno 
Published: August 2024

Abstract
There is a growing interest in the use of supercritical carbon dioxide (sCO2) Brayton cycles for power generation applications. Consequently, many researchers have developed cycle-only models, or plant models at various levels of detail to study the feasibility of such technologies. In these studies, the turbine model used has a significant effect on the results obtained. Despite this, researchers typically specify a constant isentropic efficiency, or adopt one of the efficiency correlations presented by Dyreby. The former approach is only suitable for steady state design point studies, and the use of Dyreby’s efficiency correlations are limiting. Furthermore, Dyreby’s correlations may be employed without considering the velocities of the fluid, which is critical for the determination of fluid properties throughout the turbomachine. Therefore, neither approach is suitable for off-design or dynamic studies but are applied regardless because of the limited public data available on sCO2 turbomachinery. In this paper, a method is presented that may be used to size a single stage radial inflow turbine for given nominal boundary conditions, and to develop performance maps for the same turbine at off-design conditions. These maps may then be employed to perform off-design and dynamic studies. The method employs a one-dimensional mean-line analysis approach with enthalpy loss correlations and is verified using the performance map of an existing turbine at Sandia National Laboratories. Additionally, case studies are presented where the method is used to produce conceptual designs for turbines for a proposed 50 MWe concentrated solar power plant.
On the Application of Background Oriented Schlieren to a Transonic Low-Reynolds Turbine Cascade
Authors: Halby Alexandre , Cakir Bora Orcun , Da Valle Lorenzo , Lopes Gustavo , Okada Mizuki , Lavagnoli Sergio 
Published: August 2024

Abstract
Qualitative and quantitative visualizations of transonic turbomachinery flows provide essential information on compressibility and Mach number effects on boundary layer development, shock-boundary layer interactions (SBLI) and trailing edge flows. Background Oriented Schlieren (BOS) is a relatively new optical technique that allows capturing unsteady density gradient fields through turbomachinery cascades and thus, quantitative experimental data to validate transonic and supersonic blade designs. However, only very few experimental works in the open literature have successfully applied Background Oriented Schlieren (BOS) to transonic turbine or compressor flows. The current study presents the application of BOS to a transonic low pressure turbine cascade, the VKI SPLEEN C1 cascade for a range of Reynolds numbers (70,000 to 140,000) and transonic Mach numbers (0.90 to 1.00). The linear turbine cascade is tested at the von Karman Institute in the S-1/C high-speed wind tunnel. The test section is instrumented with different BOS optical setups to visualize the time-resolved density gradients through the turbine passage and at the trailing edge plane with dedicated field of views. The BOS images are processed using the classical cross-correlation algorithm, and the optical flow approach, recently introduced in BOS applications to gain spatial resolution and increased sensitivity. Steady-state density gradients of the cascade flow characterize the airfoil boundary layers, wakes and shock waves. The results from the two data reduction methods are assessed and compared against available RANS CFD predictions. Time-resolved measurements reveals the low-frequency motion of weak shock waves generated in the blade passage using POD and spectra analysis.
Optimization of a Novel Design-For-Additive-Manufacturing Film Cooling Hole
Authors: Castelli Niccolò , Picchi Alessio , Facchini Bruno , Winchler Lorenzo , Morante Francesco 
Published: August 2024

Abstract
Additive Manufacturing has been proving a very interesting potential to produce objects having both tiny dimensions and complex and twisted shapes. For this reason, in the last years, many efforts have been done to employ AM techniques to film cooling technique in the turbine blade cooling field. The aim of the present work is to present a methodology aimed to develop a novel diffusive film cooling hole within the framework of Design-for-Additive-Manufacturing. First, starting from a set of fundamental parameters, the hole has been designed as a result of a numerical optimization in order to find out the best trade-off between different needs. Both the discharge coefficient and the adiabatic effectiveness have been evaluated and compared with the well-established 7-7-7 fan-shaped hole in order to quantify the potential of the novel geometry.
Once the numerical procedure ended, one candidate point was selected as the output to be printed by means of a Laser Powder Bed Fusion (LPBF) technique. Flow checks tests were performed on a row of 11 holes per shape and the measured discharge coefficient was found to be far lower than expected. A Computed Tomography analysis showed that the hole internal surfaces and entry/exit section collapsed in some areas. Hence, on the one hand, the numerical procedure and the outcoming shape were validated over an up-scaled flat plate housing the novel holes. Pressure Sensitive Paints measurements were performed in an open-loop wind tunnel for a blowing ratio ranging between 0.25 and 2.00. The adiabatic effectiveness showed a good agreement with CFD data, with the novel hole outperforming the 7-7-7 one. On the other hand, a compensation strategy was developed for the optimized geometries in order to overcome the difficulties encountered by the AM process due to the very tiny dimensions of the hole. After the critical features were identified and fixed by a re-design of the optimized shape, a CFD validation showed a very similar performance compared to first optimization geometry. In the end, the re-designed hole was printed. Flow check tests confirmed a higher discharge coefficient than the original one, while PSP measurements showed an improved effectiveness than the fan-shaped hole.
Techno-Economic Assessment of Hydrogen-Natural Gas Blends for Open Cycle Gas Turbines
Authors: Mogorosi Thuso Booth , Monaghan Rory F. D. 
Published: August 2024

Abstract
Hydrogen’s use at large scale for electricity generation in the current fleet of gas turbines (GTs) could present several technical, economic and environmental challenges, including high flame temperature and flame propagation velocity, potential to produce high levels of nitrogen oxides (NOx), the change in volumetric and mass flow rate, which could affect the overall power output, and the high cost of H2, which will affect the price of generated electricity. The objective of this study was to carry out a techno-economic assessment (TEA) of the use of hydrogen/natural gas (H2/NG) blends in open cycle gas turbines (OCGTs). Two NG-fuelled aero-derivative OCGTs are used as case studies, a 41-MW GE LM6000PA and a 50-MW Mitsubishi FT8 SWIFTPAC, both of which were selected based on survey of the power generation industry in Ireland. The presented method entails two steps: (1) thermodynamic modelling and (2) economic assessment. Thermodynamic modelling is performed using Thermoflex 30.0, with the purpose of evaluating the effects of H2/NG blending on the GT’s electrical efficiency, power output, and CO2 emission intensity. Variables considered for the two OCGTs in this stage are H2 blend volume fractions and GT loads. Economic assessment is then performed in an Excel-based cash flow model, with the purpose of determining the levelized cost of electricity (LCOE) of the GTs operating under different commercial conditions, including H2 and NG prices, CO2 tax, and annual OCGT capacity factor. The results shows that H2 improve the efficiency and power output of the gas turbines. Moreover, H2 blending reduces electricity generation CO2 emissions intensity. However, high LCOE are observed as the H2 blending percentage volume increases because of the current price H2, the LOCE are even higher at lower capacity factor.