bluuebunny/crossref_metadata_2025_split huggingface dataset:
Axial Compressor Map Generation Leveraging Autonomous Self-Training AI
Authors: Burlaka Maksym , Moroz Leonid 
Published: October 2022

Abstract
The paper describes the study performed by SoftInWay in the scope of the Phase I SBIR project funded by NASA.
The project was dedicated to a study of optimization of the variable geometry reset angle schedules with the use of innovative autonomous AI technology. In the scope of the project, an automated compressor performance data generation workflow was developed. Three highly loaded multistage axial compressors were designed. The developed workflow was used to generate the training, validation, and test data sets for all three compressors. Multiple different architectures of artificial neural networks were studied, and parametric models for the representation of performance speedlines were developed.
Utilizing the developed approaches, the artificial neural networks were trained for all three compressors to predict their performance with a relative error below 3 %. The trained neural networks were successfully used in the optimization of the variable inlet guide vanes and variable stator vanes reset angle schedules with a relative error of total-to-total pressure ratio prediction below 2 % for most of the points and relative error of total-to-total efficiency prediction below 1 % for all the points of the operational line.
The capability of the developed AI models to accurately predict the optimal combination of reset angles and efficiency of the axial compressor with multiple vanes controlled independently allowed doing quick evaluations of efficiency and stability margins. The availability of such information enables the opportunity to make technical-economical decisions about the reasonability of implementation of independent variable vanes and their number during engine system analysis.
Particle Image Velocimetry in a High-Speed Short-Duration Turbine Rig
Authors: Okada Mizuki , Pinho Jorge , Cernat Bogdan , Lavagnoli Sergio 
Published: October 2022

Abstract
This article presents the implementation of a Particle Image Velocimetry (PIV) into the high-speed short-duration rotating turbine facility of the von Karman Institute. The advantage of PIV as a whole field measurement is emphasized in such circumstances for which the use of optical technique can drastically reduce the number of tests and the need for multiple intrusive expensive probes, ultimately lowering the testing cost.
Practical solutions were demonstrated that address various challenges for the effective application of PIV. An endoscope delivered the laser sheet to the region of interest and a planoconcave window provided optical access for the measurement in the annular test section. Sub-micron scale oil droplets were seeded into main flow through custom-made probes located upstream the nozzle guide vane and into a pipe line supplying rim seal purge flow. A high-speed laser system and a high-speed camera were synchronized at 1 kHz sampling rate. Complementary measurements and dedicated image processing were performed to ensure the synchronization of the PIV images with the rotor position that was monitored through an encoder.
The region of interest was the blade-to-blade plane at the 58% span turbine exit on a rectangular field of view covering approximately one rotor pitch and 0.15 rotor axial chord from the rotor trailing edge. Phase-locked-average velocity fields are obtained from PIV and compared against steady-state Reynolds Averaged Navier Stokes (RANS) simulations along with four-hole probe measurement results. Together with an uncertainty analysis, the results demonstrate the promising robustness and accuracy of PIV. A practical guideline for PIV application in such kind of turbine test rigs is provided as a conclusion of the paper.
The Effect of Diffuser Shape for Film Cooling Holes With Constant Expansion Angles and Area Ratio
Authors: Lundburg Evan , Lynch Stephen , Liu Kevin , Xu Hongzhou , Fox Michael 
Published: October 2022

Abstract
Shaped film cooling holes are used in gas turbine components to deliver coolant to the high temperature surfaces of turbine blades and vanes to improve their durability. In general, shaped holes are created by expanding the outlet of the hole, resulting in a large area at the outlet of the hole that diffuses the flow. It has been shown in past studies that increasing the diffuser outlet to meter inlet area ratio causes a lower average momentum of the coolant jet at the hole exit, thereby producing better cooling performance. Instead of increasing the size of the diffuser section by increasing the area ratio, the present study focuses on changing the cross-section shape of the diffuser. This is done to mimic changes observed in the diffuser shape of conventionally manufactured film cooling holes. The present study utilizes 10-10-10 diffuser expansion angles and maintains a constant diffuser to meter area ratio. However, the diffuser shape is varied by changing the diffuser edge angle, κ, located between the diffuser sidewall and the diffuser downstream wall. Three film cooling hole shapes were tested using three different diffuser edge angles, resulting in a narrow outlet, a wide outlet, and a standard outlet film cooling hole. Each hole shape was tested in a large wind tunnel with coolant supplied to the film cooling holes at three different blowing ratios by a co-flow and counterflow delivery channel, similar to the delivery method in a turbine vane with an internal baffle. In addition, the film cooling holes were tested with simulated diffuser roughness. Adiabatic effectiveness measurements indicate that film cooling hole performance is most impacted by diffuser roughness. The film cooling hole shape arising from the diffuser edge angle directly impacts the sensitivity to blowing ratio and coolant feed direction. Therefore, it is recommended that manufacturing of film cooling holes focus on reducing roughness in the diffuser for the highest performance. It is also recommended that the tolerance of the film cooling hole shape be biased towards wider film cooling holes to minimize sensitivity to the blowing ratio and coolant feed direction.
Novel UAS Propeller Design Part 1: Using an Unloaded Tip to Reduce Power Requirements and Lower Generated Sound Levels for Propellers Designed for Minimum Induced Drag
Authors: Wisniewski Charles , Van Treuren Kenneth 
Published: October 2022

Abstract
Today, over 500 eVTOL vehicles are being developed for everything from Urban Air Mobility to package delivery. In addition, Unmanned Aircraft Systems (UASs) are used in a variety of applications to include intelligence, surveillance, and reconnaissance (ISR) as well as resupply for the military. Most of these vehicles utilize electric propulsion systems with propellers. Efficient propellers with reduced noise generation are necessary for these vehicles to coexist in urban environments or be used for ISR missions. Traditional propeller design uses Blade Element Momentum Theory (BEMT) to minimize induced losses. The current investigation describes a novel propeller design approach that minimizes induced drag by reducing the thrust loading near tip. This reduces the tip vortex strength lowering the Sound Pressure Level (SPL) and power required. A parametric study of 18 propellers examined performance using traditional BEMT design near the hub and progressing to zero thrust loading at the tip. A microphone on a traverse mounted behind the propeller was used to measure the peak SPL and its location in a wind tunnel. The best performing unloaded tip propeller showed 5.2% reduction in power required and 12 dB SPL reduction compared to a commercial propeller at the same test conditions.
Combined Heat and Power Supply Demonstration of Micro-Mix Hydrogen Combustion Applied to M1A-17 Gas Turbine
Authors: Horikawa Atsushi , Ashikaga Mitsugu , Yamaguchi Masato , Ogino Tomoyuki , Aoki Shigeki , Wirsum Manfred , Funke Harald H.-W. , Kusterer Karsten 
Published: October 2022

Abstract
Kawasaki Heavy Industries, Ltd. (KHI), Aachen University of Applied Sciences, and B&B-AGEMA GmbH have investigated the potential of low NOx micro-mix (MMX) hydrogen combustion and its application to an industrial gas turbine combustor. Engine demonstration tests of a MMX combustor for the M1A-17 gas turbine with a co-generation system were conducted in the hydrogen-fueled power generation plant in Kobe City, Japan.
This paper presents the results of the commissioning test and the combined heat and power (CHP) supply demonstration. In the commissioning test, grid interconnection, loading tests and load cut-off tests were successfully conducted. All measurement results satisfied the Japanese environmental regulation values. Dust and soot as well as SOx were not detected. The NOx emissions were below 84 ppmv at 15 % O2. The noise level at the site boundary was below 60 dB. The vibration at the site boundary was below 45 dB.
During the combined heat and power supply demonstration, heat and power were supplied to neighboring public facilities with the MMX combustion technology and 100 % hydrogen fuel. The electric power output reached 1800 kW at which the NOx emissions were 72 ppmv at 15 % O2, and 60 %RH. Combustion instabilities were not observed. The gas turbine efficiency was improved by about 1 % compared to a non-premixed type combustor with water injection as NOx reduction method. During a total equivalent operation time of 1040 hours, all combustor parts, the M1A-17 gas turbine as such, and the co-generation system were without any issues.
Evaluation of the Performance of a 200kW Recuperated Gas Turbine Engine Operated on Up to 30% Hydrogen Added to Natural Gas
Authors: Villatoro Walther , McDonell Vincent , Hu Ray , Ayers Don 
Published: October 2022

Abstract
Achieving carbon neutrality and sustainability has prompted research efforts into reducing carbon dioxide and carbon monoxide emissions in combustion systems without significantly increasing nitrogen oxides (NOx). Because of its high specific energy density, hydrogen is a prime candidate to eventually replace natural gas. Presently, using renewable hydrogen mixtures in natural gas turbines can reduce carbon dioxide and carbon monoxide emission as a step towards carbon neutrality. In the present effort, a commercial natural gas 200kW microturbine generator produced by Capstone Green Energy Corporation is used to study the impact of hydrogen addition to natural gas. Exhaust emissions, injector temperatures, and power output are evaluated for increasing levels of hydrogen in the fuel mixture. Relative to emissions on 100% natural gas, the experimental results show that, for full load, carbon monoxide and carbon dioxide emissions decrease as the amount of hydrogen in the fuel mixture increases while the NOx emissions increase. This is attributed to the increased reactivity of hydrogen resulting in a jet flame stabilized closer to the injector exit as the amount of hydrogen is increased. While the injector tip temperatures increased modestly with additional hydrogen, visual inspection of the injectors following hydrogen addition tests indicate that flashback or combustion inside the injectors was not occurring. This is consistent with the modest changes in NOx with hydrogen addition. If flashback were occurring, the emissions levels would be expected to be significantly higher. The results also demonstrate that added hydrogen to the fuel does not have a statistically significant impact on overall system efficiency. In general, the results show that the injectors can withstand the temperature increase from hydrogen addition while maintaining low emissions at full load, indicating that addition of hydrogen is possible without any modification to this gas turbine engine which has been optimized for performance on natural gas. Parametric studies were carried out to demonstrate how modest changes in engine operating points and fuel injectors can be incorporated to attain single digit NOx levels with up to 30% hydrogen.
Two Stage Radial Compressor for a Kilowatt Scale Supercritical Carbon Dioxide Power Block: Design Considerations
Authors: Seshadri Lakshminarayanan , Patel Ashutosh , Biradar Vijay , Kumar Pramod , Gopi Pramod Chandra 
Published: October 2022

Abstract
Potential applications of kilowatt (kW) scale supercritical Carbon dioxide (sCO2) Brayton power systems include exhaust waste heat recovery in diesel engines and bottoming cycles for biomass gasifier-driven gas turbines. However, the practical realization of the kW scale single-stage sCO2 turbomachinery is associated with several challenges. While a hermetically sealed arrangement is most beneficial, it is fraught with large windage losses in the motor rotor cavity. The high windage losses in the single-stage setup are primarily due to high shaft speeds. These issues limit the commercial utility of kW scale sCO2 Brayton power cycles. In order to mitigate these issues, the design of a two-stage unshrouded radial compressor unit for a kW scale sCO2 Brayton cycle is described in this study. The working pressures are 103 bar/ 170 bar, and the compressor mass flow rate is 2 kg/s. These optimal operating pressures are obtained taking into consideration both thermodynamic power and motor/disc windage losses. The two rotors are mounted on a single shaft in a double-ended configuration where the axial thrusts act in opposite direction. The compressor blade profiling is carried using a standard design tool. The performance of the compressor is assessed using a 1D mean-line calculation to estimate the overall efficiency. Using this approach, an overall compressor efficiency of ∼ 71.8 % (including motor and disc windage losses) is attained. A 3D CFD simulation is carried out at the design point to validate 1D data. Rotodynamic analysis is carried out to determine the first and second shaft critical speeds of the rotor-shaft configuration. Structural analysis is carried out to ensure that the maximum Von-Mises stresses are well below the material limits.
The Role of Turbine Operating Conditions on Combustor-Turbine Interaction – Part 1: Change in Expansion Ratio
Authors: Notaristefano Andrea , Gaetani Paolo 
Published: October 2022

Abstract
Aeroengine lean-burn combustors release vorticity and temperature perturbations that, interacting with the first turbine stage, impact the stage aerodynamics, the blade cooling and noise production. The first of these issues is addressed in this paper that is part 1 of a two-fold contribution. A detailed experimental analysis is carried out to study the impact on the combustor-turbine interaction of the off-design conditions experienced by aero-engines in their duty.
Engine-representative disturbances are generated by a combustor simulator able to produce swirling entropy waves. Two injection positions and four injection cases are studied. Experimental measurements are carried out at three traverses: upstream of the stator, at the interstage, and downstream of the rotor.
This paper analyses the effect of the stage expansion ratio: two values are studied, namely 1.4 and 1.76, representative of subsonic and transonic flow conditions. They are chosen imposing similar velocity triangles at the rotor inlet. Results show that the swirl profile considerably impacts the stage aerodynamics. The aerothermal flow field downstream of the stator is modified significantly by the combustor disturbances. Conversely, downstream of the rotor, the differences in aerodynamics lessen. However, the entropy wave persists at the stage outlet and its transport depends on both the operating point and the injection position.
A Novel Engine Architecture for Low NOx Emissions
Authors: Blondeel Tim , Yin Feijia , Gangoli Rao Arvind 
Published: October 2022

Abstract
The fuel efficiency of turbofan engines has improved significantly, hence reducing aviation’s CO2 emissions. However, the increased operating pressure and temperature for fuel efficiency cause adverse effects on NOx emissions. Therefore, a novel engine concept, which can reduce NOx emissions without affecting the cycle efficiency, is of high interest to the aviation community. This paper investigates the potential of an intercooler and inter-turbine burner (ITB) for the future low NOx aircraft propulsion system.
The study evaluates performance and NOx emissions of four engine architectures: a very high bypass ratio (VHBR) turbofan engine (baseline), a VHBR engine with intercooler, a VHBR engine with ITB, and a VHBR engine with both intercooler and ITB. The cycles are optimized for minimum cruise Thrust Specific Fuel Consumption (TSFC), considering the same design space, thrust requirements, and operational constraints. The ITB is only used during take-off to minimize cruise fuel consumption. The analysis shows that using an ITB solely, with the energy split of 75% (the first burner) / 25% (ITB), reduces the cruise NOx emission by 26%, and the cruise TSFC slightly by 0.5%. The intercooler alone reduces the NOx emissions by 16% and the cruise TSFC by 0.8%. The combination of intercooler and ITB reduces the NOx emissions further by 38%. The analysis confirms that introducing an intercooler and ITB can potentially resolve the contradicting effects of fuel efficiency and NOx emissions for the future advanced turbofan engine.
Improved Design Space Exploration by Machine Learning Estimation for a Parametric Turbofan Model
Authors: Foster Chad , Moore Jack 
Published: October 2022

Abstract
In the preliminary design phase, selecting an architecture requires understanding the influence of noise parameters while exploring the design range. Given that architecture simulations are slow, the normal approach is to generate meta-models or fast running models that are sufficiently accurate. These meta-models are used to efficiently select robust designs by quickly estimating the impact of noise distributions for different design independents.
The creation of these meta-models is efficiently accomplished by designed experiments. Predetermined runs are decided by factorial experiments, Latin hypercube designs, or sequential experimentation. These simulation runs have combinations of independents and noise parameters that are outside of previous experience. Without accurate initial estimates the simulations may not converge or have long simulation times. A method is presented to improve these simulations through more effective initial estimates.
The estimates are created by a data-based, machine learning, model that is created from previous successful runs. This additional model is used to make accurate initial condition guesses.
By using a chained linear regression model, the initial conditions for half the parameters are improved compared with using the previous run. The resulting meta-model can be used for additional design studies. It is also shown that improvement may not translate into significant run time differences as single parameter estimates may drive convergence.
Experimental and Numerical Assessment of Liquid Film Thickness Under High-Speed Gas Flow
Authors: Okui Takayuki , Mizumi Shunsuke , Tabata Soichiro , Mizushima Yuki , Sanada Toshiyuki 
Published: October 2022

Abstract
For improving steam turbines, we need to solve pending issues derived from the gas-liquid two-phase flow phenomena, i.e., turbine blade erosion and wetness loss. These troubles result from the droplets atomized from the liquid-film flow on the blade. Although the most conventional study has successfully analyzed the liquid film that spreads all over bottom floor of the channel, the blade surface’s liquid film is supposed to be a rivulet flow. Therefore, analysis considering the rivulet-like condition has significance for accurate estimation of the liquid-film flow on the blade contributing to the atomization of the droplets.
In this study, we demonstrated thickness measurement for the rivulet-like film flow using an Optical-fiber-based Reflective Probe (ORP). Airflow (jG = 40∼75 m/s) was introduced into the rectangle test section, then a small amount of tap water (Q = 5 ∼ 15 × 10−7 m3/s) was injected on the channel plate. We measured the thickness of the liquid film simultaneously by using ORP and high-speed visualization. Further, we also estimated the thickness of the liquid-film flow by CFD using ANSYS Fluent. We will discuss their qualitative agreement and tendency, which describe some differences from similar previous experiments. At last, whether the ORP measurement applies to the rivulet-like film flow or not is validated, including its uncertainty, experimentally and numerically.
Numerical Analysis of an Axial High Pressure Partial Admission Turbine
Authors: Hu Heng , Askebjer Per , Genrup Magnus , Hushmandi Narmin 
Published: October 2022

Abstract
The transformation of the energy systems will call for new turbomachinery designs for harvesting low-grade heat. The word “low-grade” has many definitions and ranges from levels where steam is the preferred selection to very low grades where specially adopted ORC technology is used. In this work, turbomachinery for cascading the steam cycle with a very low-temperature ORC technology is studied. The steam turbine being investigated here is, in principle, a highly-loaded small backpressure turbine. One indeed important feature is the trade-off between losses related to partial arc admission and losses due to having very short blades. This sets the overall architecture of the turbine and is one of the most prominent selections during the design. Due to the special working/boundary conditions, a supersonic axial turbine model and partial-arc admission were necessary. Previous open literature had shown better performance with one admitted arc. A full three-dimensional analysis of such a turbine model using CFD techniques is rather challenging. Due to the special character of the supersonic flow and the interaction of possible shocks with boundary layer flow, a fine grid is required for this application. On the other hand, due to the unsymmetrical feature of the geometry imposed by the existence of only one blocked arc, modeling of the full annulus of the turbine is unavoidable. Computations are done to assess the characteristics of the flow inside threedimensional supersonic turbine using commercial CFD codes. The unsteady loads of the rotor blades are analyzed both in time and frequency domains.
Analysis of Ultra-High Bypass Ratio Turbofan Nacelle Geometries With Conventional and Short Intakes at Take-Off and Cruise
Authors: Magrini Andrea , Bousi Denis , Benini Ernesto 
Published: October 2022

Abstract
Turbofan engines with ultra-high bypass ratio require more aggressive nacelle designs to limit the drag and weight associated to the increased fan diameter. Reducing the inlet length-to-diameter ratio appears a possibility for further weight saving and mitigation of the total pressure losses. However, these benefits are counteracted by the higher fan exposure to nonuniform in-flow conditions. In this paper, we compare three nacelle geometries for an ultra-high bypass ratio turbofan with a progressively shorter intake having a length-to-diameter ratio of 0.475, 0.35, and 0.22 and two different compact cowl designs. The complete isolated nacelle model, including the exhaust system and a pylon, is simulated numerically with the fan rotor and stator cascades represented through a body force method, allowing to capture the engine/nacelle interaction. The three geometries are examined at take-off and cruise, measuring the variation of integral metrics related to the inlet performance and the propulsive forces. Although with shorter intakes the total pressure losses and the separation onset are positively impacted at high incidence, a careful shaping of the lip is needed to control the diffusion in the limited axial extension available. The effect on the propulsive forces is found to be limited at take-off for a fully attached flow, whereas at cruise the gross thrust improvement of the more compact nacelle is counterbalanced by a larger drag.