bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Evaluation of Additively Manufactured Sensors for Combustor Surface Temperature, Heat Flux and Strain Measurements
Authors: Chandh Aravind , Adhikari Subodh , Wu David , Lieuwen Tim , Emerson Benjamin 
Published: August 2024

Abstract
System components with embedded sensors help obtain real-time system performance feedback and in situ monitoring during operation. This paper describes the development and assessment of embedded sensors fabricated employing a Direct Wire (DW) deposition process, which enables their integration directly onto the components being tested. Three separate combustor panels were additively manufactured using the Direct Metal Laser Sintering (DMLS) technique with 1) thermocouples, 2) heat flux gages, and 3) strain gages embedded on the cold side of combustor panels. These surface contact sensors are a few millimeters wide and are within 50 μm thick and thus, have minimal effect on the reacting flow field of a combustor. They were first characterized in a controlled environment (oven and strain beam tests) and then tested in a single nozzle liquid spray reacting combustor simulating realistic aircraft conditions operated at elevated pressures of up to 4 bar and inlet temperatures starting at 410 K. These sensors survived the harsh operating environment involving high-temperature settings for an extended period and cyclic thermal loading and exhibited repeatable and reliable readings. This paper serves as a demonstration of these additively embedded sensors and provides data from the combustion test rig to show repeatability and transient response characteristics. This development is useful for R&D purposes of current-gen energy, automotive, and aerospace systems and in the development of more efficient and smarter next-gen combustion systems.
GPU-Accelerated Actuator-Disk Large-Eddy Simulation for Wind Farm Flows
Authors: Dabas Jérôme , Staffelbach Gabriel , Odier Nicolas , Duchaine Florent , Gicquel Laurent 
Published: August 2024

Abstract
The power production of a wind farm depends on complex interactions between the atmospheric boundary layer (ABL), the wind turbines and their wakes. These interactions can be captured with accuracy and at a reasonable cost using an Actuator-Disk Large-Eddy Simulation (AD-LES) approach [1] where the most energetic scales of the ABL are resolved while wind turbines are modelled by volume forces. The present study shows that this approach can be used with GPU-acceleration to simulate an entire wind farm at a reasonable turnaround time.
To do so, the AD model has been implemented for GPU architectures in the CERFACS’ LES solver AVBP [2], the approach being then validated on the Horns Rev wind farm configuration in neutral atmospheric boundary layer [3]. Good agreement is found between field measurements and numerical predictions. In addition, the LES flow field is used to assess wake models and investigate various wake superposition laws to better understand their effect on the power prediction.
Loss Breakdown in Axial Turbines: A New Method for Vortex Loss and Wake Detection From 3D RANS Simulations
Authors: Raina Greta , Bousquet Yannick , Luquet David , Lippinois Eric , Binder Nicolas 
Published: August 2024

Abstract
To enhance turbine efficiency, it is essential to mitigate the loss generated by irreversible phenomena taking place in turbine flows, including boundary layers, shock waves, vortices and trailing edge wakes. A fast and accurate detection of losses is therefore crucial from the earliest stages of turbine design, in which low-fidelity models based on oversimplified correlations are employed. Achieving this objective requires a deep comprehension of the physics behind each loss-generating mechanism, a goal attainable through the examination of the 3D flow. While existing criteria allow the identification of various phenomena, accurately quantifying losses generated by vortices remains a challenge: these losses frequently extend beyond the vortical structure. The aim of this paper is to provide a straightforward and effective approach to localize and assess vortex-related losses. This method is grounded in Zlatinov’s decomposition of the entropy generation rate equation into a stream-wise and a secondary flow component. A criterion based on the vortex kinematics is used to evaluate the strength of the vortex, thereby enabling the determination of its spatial influence and its contribution to the overall losses. To validate the method, a post-processing code is developed which allows to perform loss breakdown. This tool makes use of existing identification criteria and some new techniques introduced within this work, especially for wake detection. 3D RANS simulations are carried out on several configurations, ranging from simple curved ducts to more realistic nozzle guide vanes (NGV), to gradually test and validate the computational tool. Results confirm that the highest rates of entropy generation occur outside of the vortical structure, and show good ability to identify both the vortex shape and its area of influence in terms of losses. A drastic improvement in the prediction of vortex losses is especially observed in the case of turbine blades with tip or hub leakage vortices.
Micro Gas Turbine Fed With Ammonia As Fuel: Performance Analysis and NOx Emissions Reduction
Authors: Fatehi Mohsen , Campaldini Graziano , Renzi Massimiliano 
Published: August 2024

Abstract
The increasing global demand for energy and the need to reduce polluting emissions necessitate the use of alternative fuels, especially in the hard-to-abate sectors, that are more critical from an environmental standpoint. Ammonia is considered as a promising carrier of green hydrogen and as a renewable carbon-free fuel, therefore, it is anticipated to play a fundamental role in the decarbonization of the energy supply chain. In this study, a simulation algorithm has been used to evaluate the performance of a 3.2 kWe Micro Gas Turbine (MGT) fed by ammonia. The algorithm comprises a set of equations describing the behavior of the MGT’s components, and the consumption of the auxiliary devices. To examine the combustion kinetics and evaluate the MGT emissions with ammonia feed, a further algorithm utilizing Cantera library has been developed. This model is a one-dimensional tool that allows to assess the mixing flows in the combustion chamber, the temperature trends, and the formation of the combustion products. Results indicate that, if a suitable fuel injection and an air supply strategies are used, the electric power output obtained using Ammonia (NH3) turns out to be comparable to that obtained with Methane (CH4), while the electric efficiency is marginally lower (5.16%). In this work, due to the high amount of NOx emission when using ammonia, the Rich-Lean non-premixed combustion strategy is investigated in a three-stage combustion chamber. By adopting this strategy, the amount of NOx concentration has been reduced to 744 ppm (15% O2 dilution), about 92% less than original strategy.
Robust Optimization of a Compressor Blade Through Combination of an Adjoint-Based Multistart Approach and Global Gaussian Process Regression
Authors: Karimian Aryan , Schmidt Robin , Janke Christian 
Published: August 2024

Abstract
The real geometry of compressor blades naturally deviates from the intended design due to the finite accuracy of manufacturing processes as well as abrasion and deformation in operation. Consequently, a deterministic design approach causes an inevitable performance degradation. Robust design optimization captures this effect by defining a probabilistic objective that is subject to uncertain geometrical features. However, the required process complexity inherently entails an increase in computational cost, which narrows the pool of available methods in the industrial context due to the extensive usage of costly three-dimensional computational fluid dynamics in aerodynamic investigation. The adjoint method provides a means for the cheap acquisition of gradient information and thus lays the foundation for efficient gradient-based local search procedures. Furthermore, a global approximation of the search space can be achieved by surrogate modeling techniques enabling a better understanding of the system behavior and guidance towards the global optimum.
This paper presents the development and application of a hybrid robust optimization algorithm to compressor aerodynamics through the combination of the respective advantages of an efficient gradient-based search methodology incorporating the adjoint method and the Gaussian process regression. As such, the proposed algorithm aims for the balance of local and global optimization. For this purpose, a favorable interaction between the involved methods was targeted while accounting for geometrical uncertainty determined from optical measured blades. The performance of the employed methods as well as their ensemble within the complete algorithm was validated and analyzed on a low- and high-dimensional test function. In addition, the algorithm was compared to the efficient global optimization algorithm (EGO) where the behavior and overall results were evaluated by suitable criteria regarding the compressor application case. Following the established strategy, robust design optimization of a rotor blade from a state-of-the-art high-pressure compressor was conducted. The algorithm’s decisions and especially the surrogate model were monitored and analyzed. Validation by means of a design of experiments resolving the uncertainty space revealed the nonlinear character of the compressor performance with respect to geometrical uncertainty. The applied algorithm yielded a robust optimum, which is superior to those acquired by previous local searches under equal conditions. Ultimately, the optimal blade aerodynamics were analyzed and compared to the nominal design, disclosing a systematic reduction of loss caused by secondary flow and supersonic effects. A definite adaptation to the operating point under investigation was observed, leading to a shortened characteristic, albeit with improvement in a wide operating range.
Prediction and Analysis of Turbulence Anisotropy in a Low-Pressure Turbine Cascade at Two Reynolds Numbers Based on Transitional DDES
Authors: Fard Afshar Nima , Möller Felix M. , Deutsch Johannes , Henninger Stefan , Morsbach Christian , Kožulović Dragan , Bechlars Patrick , Jeschke Peter 
Published: August 2024

Abstract
This study analyzes the influence of Reynolds number on the turbulence anisotropy behavior for the transitional flow over the MTU-T161 linear low-pressure turbine (LPT) cascade. Two operating points at Reynolds number Re = 90,000 and Re = 200,000, both at an isentropic exit Mach number of 0.6, are calculated using a transitional Delayed Detached Eddy Simulation (DDES) model. We focus our investigation on the separation-induced transition occurring on the suction side, its sensitivity to the Reynolds number and the capabilities of the transitional DDES approach for capturing the turbulent state. The computational model of the MTU-T161 cascade consists of a single blade passage, including the diverging viscous sidewalls. Synthetic turbulence is generated at the inlet of the domain to mimic realistic turbomachinery flow conditions.
We show that the transitional DDES model is able to capture the separation and transition mechanism correctly for both Reynolds numbers, when compared to experimental data. The main part of this paper consists of a detailed analysis of the turbulence anisotropy behavior with particular attention to the separation bubble when changing the Reynolds number. By increasing the Reynolds number from 90,000 to 200,000, the turbulence anisotropy state of the suction side flow changes only slightly. At the higher Reynolds number, the passage flow is mostly governed by two-component turbulence state, while the separation bubble and its influence on the passage flow become weaker. The turbulence anisotropy analysis reveals an almost two-component state very close to the wall region and a one-component turbulence state in the separated shear layer for both Reynolds numbers. Our results show the capability of the transitional DDES model to capture the correct trend of the Reynolds stresses and the anisotropy behavior by comparing the results to a previously published Large eddy simulation (LES). The DDES method is not successful in capturing the Klebanoff modes (streamwise fluctuations) in the pre-transitional region, when compared to LES. These results enhance our overall comprehension of the turbulence state within different separation bubble sizes. Furthermore, the results indicate that the transitional DDES model resolves the essential characteristics of turbulence while keeping the computational cost up to seven times lower than LES.
Optimised Pilot Burner With Intelligent Control to Achieve Sub 9 PPM Emissions for Siemens Energy SGT-300-1S 7.9 MWe Engine
Authors: Liu Kexin , Sadasivuni Suresh 
Published: August 2024

Abstract
In support of reduction in emissions, Siemens Energy Industrial Turbomachinery Ltd (SEITL) developed the optimised pilot burner for its SGT-300 engine to produce ultra-low emissions for a wider range of engine load. The optimised pilot burner has been developed based on the standard pilot burner, with the size of the pilot gaseous fuel injection holes optimised, resulting in a significant reduction in its effective area. To validate the design change, a single-shaft SGT-300 engine (SGT-300-1S) configured with the optimised pilot burners and the rest of the combustion hardware as standard was tested at various operating conditions including natural turndown as well as with turndown control temperature at part load by Variable Guide Vane (VGV) modulation. An intelligent control algorithm for combustion was used, and its settings for the optimised pilot burners were refined by pilot split mapping during engine testing. The same engine configured with standard pilot burners was also tested to provide reference data. Extensive instrumentation and measurement equipment were used in the engine test to measure NOx, CO, and Unburnt Hydrocarbon (UHC) emissions and combustion system performance, such as fuel supply pressures and temperatures, combustion hardware metal temperatures, and combustor and casing dynamic pressure. Engine test results show that the optimised pilot burner, when operated with the refined intelligent control method for combustion system, can achieve a wide load range of sub 9 ppmvd emissions for the SGT-300-1S engine.
Suppression of Combustion Oscillations in Hydrogen-Enriched Can-Type Combustors Through Fuel Staging
Authors: Jung Junwoo , Kim Daesik , Wang Yuangang , Park Soonbeen , Sohn Chae Hoon , Kim Minkuk , Hwang Jeongjae , Kang Dowon , Lee Wonjune , Kim Hanseok 
Published: August 2024

Abstract
To achieve decarbonization in power-generating gas turbines, the technology of mixing hydrogen with natural gas is garnering significant attention. However, when blending natural gas with hydrogen, the altered combustion characteristics can lead to combustion instability in gas turbine combustors. Although fuel staging can effectively suppress combustion instability for can-type combustors, further research on mitigation strategies for hydrogen co-firing and their predictive methods is required. This study involves hydrogen co-firing experiments using a full-scale can-type combustor. Moreover, the resulting suppression of combustion instability is analyzed through fuel staging by utilizing three-dimensional (3D) computational fluid dynamics (CFD) and one-dimensional (1D) thermo-acoustic analysis. The experiments used a full-scale industrial can-type combustor with a five-around-one nozzle configuration. Hydrogen was blended with natural gas up to a volume fraction of 30%, maintaining a constant thermal power. Fuel staging was applied by controlling two out of five outer nozzles along with the remaining three. Before the 1D thermo-acoustic analysis, the internal flame structure of the combustor was examined through 3D CFD analysis. Based on the results, a multi-input multi-output (MIMO) system was constructed for 1D thermo-acoustic analysis of the can-type combustor. The application of time delays derived from 3D CFD analysis to the 1D model revealed that differences in flame time delays across the nozzles cause combustion instability suppression observed in fuel staging.
NASA HECC Geometry and Performance Review Part 3: A Numerical and Experimental Investigation of Tip Clearance Effects on the Vaneless Diffuser Configuration
Authors: Harrison Herbert M. , Nguyen-Huynh Tammy , Mathison Randall M. 
Published: August 2024

Abstract
Tip clearance effects in centrifugal compressors have been extensively investigated to understand the losses associated with the flow in the impeller tip clearance gap between the rotating blades and the stationary shroud. In Part 3 of this multipart investigation, experimental data and validated numerical simulations from Parts 1 and 2 were used to analyze the effects of the size of the tip clearance gap on the High Efficiency Centrifugal Compressor performance and aerodynamics. Four tip clearance gaps ranging from 0.012-in to 0.030-in (2.0% to 4.9% of the impeller exit blade height) were considered at both design and off-design operating conditions. The total pressure ratio and efficiency of the stage are found to decay linearly with increasing tip gaps. The sensitivity of the impeller performance to the tip gap was found to vary with the rotational speed of the compressor. Spanwise surveys of flow angle, total pressure, and total temperature collected at the impeller exit at design speed are used to validate numerical simulations at each experimental tip gap condition. Numerical simulations show that increased turbulence kinetic energy near the shroud at larger tip gaps leads to spanwise mixing of high entropy fluid near the impeller trailing edge which decreases the useful work input by the impeller. The data presented have been made available to the public in the HECC Data Archive located at https://storage.googleapis.com/hecc-data/NASA-HECC-Data-Archive.zip.
Performance Evaluation of a Direct Air-Cooled Supercritical Recompression Brayton Cycle Using CO2/n-Butane As the Working Fluid Operating Under Off-Design Conditions
Authors: Wang Xurong , Zhang Longwei , Qi Jianhui , Fan Xiaowei , Dai Yiping 
Published: August 2024

Abstract
In order to improve the air-cooled supercritical carbon dioxide (CO2) Brayton cycle for solar power systems, the use of mixed working fluid is a potential direction. The thermal stability of the CO2-based mixture at the operating temperatures, however, has not received as much attention as the thermodynamic performance. In this study, the degradation of CO2/n-Butane mixture is investigated using ReaxFF simulation method. Based on design results and off-design model of a direct air-cooled supercritical CO2/n-Butane Brayton cycle, the influence of thermal decomposition of the working fluid is evaluated on the cycle thermodynamic behavior. The results show that the fluid degradation greatly reduces the ability of the power cycle to absorb heat input from the solar field. When the totally decomposition of CO2/n-Butane mixture occurs, the net electricity is decreased by 32% at the design ambient temperature, while the cycle thermal efficiency is near the design-point efficiency. In addition, the impact of fluid degradation is much greater than above-design ambient temperature on the off-design performance of the supercritical Brayton cycle. This study indicates that the design of novel CO2-based mixture Brayton cycles should simultaneously take into account the cycle performance and thermal stability of the potential CO2 mixture.
Assessment of a BLI-Tolerant Aft-Fan at Design and Near Stall Conditions - From Preliminary to Detailed Aerodynamic Design
Authors: Mennicken Maximilian , Schnell Rainer , Kožulović Dragan 
Published: August 2024

Abstract
Boundary layer ingestion (BLI) is a promising concept to decrease the climate impact of civil aviation. One propulsion unit architecture considers a wake filling propulsor in the rear of the fuselage aiming at a higher fuel-efficiency. The flow entering the propulsion unit features stagnation pressure and swirl distortions. The fuselage boundary layer causes a stagnation pressure variation orthogonal to the fuselage. Moreover, the fuselage upsweep leads to a circumferential non-homogeneous stagnation pressure distribution and causes a swirl distortion. This study focuses mainly on three parts. Firstly, a new and numerically efficient design and assessment methodology for distortion tolerant fans is presented. The new methodology requires approximately 3 CPUh to assess fans in BLI conditions which is four orders of magnitude lower than the assessment by time-resolved calculations. Secondly, a distortion tolerant fan stage is assessed at the aerodynamic design point. The study shows that the new design methodology is able to capture the flow redistribution due to the stagnation pressure distortion and the local operating point variation around the circumference. Compared to the design conditions which feature purely radial distortion, the two-dimensional distortion leads to a fan efficiency decrease of 1.16%. The additional decrease of fan efficiency associated with the swirl distortion is 0.35%. Thirdly, a similar analysis is conducted at near stall conditions. The two-dimensional stagnation pressure distortion leads to a 2.5% lower fan efficiency compared to the purely radial distortion while the swirl distortion leads to a further decrease of 0.44%. Therefore, the fan performance is mainly driven by the stagnation pressure distortion rather than by the swirl distortion. At both operating conditions and both distortions, the fan attenuates the distortion which manifests in a decrease in distortion intensity of minimum 30% up to 40%.
Techno-Economic and Environmental Evaluation of Steam Generators Availability in Enhanced Oil Recovery Applications
Authors: Al Busaidi Waleed 
Published: August 2024

Abstract
Enhanced oil recovery technology become one of the key players in oil and gas applications targeting a high production value with a minimum cost. However, this necessitates the need for high reliable and efficient steam generators to recover the heavy oil. Thus, this paper followed a novel integrated approach to improve the availability of the OTSGs using both regression statistical analysis and failure-modes analysis. This was validated using actual data and the steam system availability has been compared before and after the trial. Furthermore, the second part of this study involved a sensitivity study at design and off-design conditions to identify the dominant factors with the highest impact on the reliability of steam system and its interaction with the hydrocarbons recovery. This can help to obtain the optimum operating point considering efficiency, cost, and CO2 emissions of OTSGs. The data show an average yearly availability of steam generators by about 74% with an average steam loss of about 673 ton/day and a potential of 218 m3/d of oil. This has caused approximately 24.4 MUSD as annual deferment cost. Finally, a new method has been also developed to assess the possibility of scaling formation in the steam generators and it has been also validated using actual pigging data. One of the main features of this approach is that it can be used to identify the optimum required cleaning frequency with less downtime and maintenance cost. Moreover, the upward trend of stack temperature data shows a degradation in the absorbed heat ratio by around 2.0% with an increase of about 6020 sm3/d in the fuel consumption. This also indicates the need for routine washing of the convection section finned and bare tubes. Environmentally, the high fuel rate leads to increase CO2 emission by 8164.8 ton per year. Additionally, the CO2 trend shows a sharp increase in the emission rate between 95% and 100% steam output by roughly 9.1% driven by a dramatic increase in the fuel consumption comparing with estimated additional hydrocarbons recovery revenue rate of around 6.9%.