bluuebunny/crossref_metadata_2025 huggingface dataset:
Will they be back? A framework to guide rare macrophyte conservation decisions in lakes
Authors: Bennion Helen , Sayer Carl , Baker Ambroise , Bishop Isabel , Glover Azra , Jones Viv , Law Alan , Madgwick Genevieve , Peglar Sylvia , Roberts Carole , Rose Neil , Turner Simon , Willby Nigel , Yang Handong
Published: September 2023

Shallow lake restoration typically focusses on the re‐establishment of macrophytes. The likelihood of a species returning to a site is contingent on dispersal, proximity to propagule sources, and the on‐site propagule‐bank viability. We explore the potential of palaeoecological records in combination with botanical surveys and distribution maps, to ascertain the loss of three submerged macrophytes (Littorella uniflora, Najas flexilis, and Elatine hydropiper) from, respectively, two lakes (Barton Broad, Norfolk and Esthwaite Water, Cumbria) and one lake landscape (Greater Glasgow, Scotland). We discuss re‐establishment likelihood when accounting for species' autoecology and current water‐chemistry conditions. L. uniflora is widespread in the United Kingdom but absent locally in Norfolk without known seed bank, hence is unlikely to naturally recolonise Barton Broad. Furthermore, current conditions are unsuitable for this species suggesting that nutrient reduction is required prior to translocation. N. flexilis is extinct in Cumbria and the long distances involved (>100 km) for recolonisation of Esthwaite Water suggest that spatial dispersal is unlikely, rendering the seed bank the last chance of natural recovery. Alternatively, translocation may be feasible. E. hydropiper is a nationally scarce species in the United Kingdom yet would have only a short dispersal distance (~10 km) to recolonise Loch Libo, hence there being no requirement for translocation. In exploring the recovery possibilities for the three focal plant species, we develop a time–space integrated framework that can be employed to guide conservation decisions for other species, enabling a more rational use of translocations in the future, in line with international guidelines.
Behavioural knowledge for policy design: The connection between time use Behaviours and (or) desires and support for policy alternatives
Authors: Lahat Lihi , Sened Itai
Published: September 2023

The study explored how understanding people's behaviours and desires can inform policy design and contribute to policy feedback theory. We focused on uses of time that are affected by diverse policies. Given the growing interest in promoting well‐being and the connection between the use of time and well‐being, we examined behaviours and desires regarding uses of time. In this exploratory study, we employed a quantitative research method. We surveyed 671 Israeli adults on their time use, desires for time use, and support for policy alternatives in three policy fields: work, education, and welfare. In five out of 11 policy alternatives, we found a connection between behavioural variables and support for policy alternatives. While exploratory, our findings contribute innovative insights into the connection between behavioural variables and support for policy alternatives related to time use. Theoretically, the article highlights the importance of incorporating behavioural ‘signalling knowledge’ as an essential input at the policy design stage and contributes to the policy feedback literature on multidisciplinary policies.
Corporate governance and management accounting to reduce agency conflicts
Authors: Solana-González Pedro , Vanti Adolfo Alberto , De Iudícibus Sérgio
Published: October 2023

This paper aims to discover priority alternatives involved in decisional-making processes to reduce agency problems considering Corporate Governance (CG) and Management Accounting (MA) criteria. Using the Multi-Criteria Decision-Making (MCDM) methodology, it is possible to model the hierarchy structure to determine the ranking of decisional priorities using the Analytic Hierarchy Process (AHP) method. CG and MA are the main criteria for decision-making to reduce problems between ownership and capital control. Thus, engaging agents is the first alternative to reduce agency conflicts considering a general approach. Strategic accountability should be a priority to reduce agency problems focusing on CG and confidence is the main variable to consider from the MA standpoint. The research provides a multiple criteria system to reduce agency problems in decision-making. This work contributes to information asymmetry’s minimization and has implications on value preservation and creation for stakeholders. The decisional structure and the alternatives related to CG and MA have direct practical applications for managers and actors involved in business decisions to reduce agency conflicts. This paper provides evidence on the importance of CG and MA variables to reduce information asymmetry and agency problems and sets out the main priorities in a context of decision making for managers.
Creation and Assessment of a Novel Design Evaluation Tool for Additive Manufacturing
Authors: Cayley Alexander , Mathur Jayant , Meisel Nicholas A.
Published: September 2023

Additive manufacturing (AM) is a rapidly growing technology within the industry and education sectors. Despite this, there lacks a comprehensive tool to guide AM novices in evaluating the suitability of a given design for fabrication by the range of AM processes. Existing design for additive manufacturing (DfAM) evaluation tools tend to focus on only certain key process-dependent DfAM considerations. By contrast, the purpose of this research is to propose a tool that guides a user to comprehensively evaluate their chosen design and educates the user on an appropriate DfAM strategy. The tool incorporates both opportunistic and restrictive elements, integrates the seven major AM processes, outputs an evaluative score, and recommends processes and improvements for the input design. This paper presents a thorough framework for this evaluation tool and details the inclusion of features such as dual-DfAM consideration, process recommendations, and a weighting system for restrictive DfAM. The result is a detailed recommendation output that helps users to determine not only “Can you print your design?” but also “Should you print your design?” by combining several key research studies to build a comprehensive user design tool. This research also demonstrates the potential of the framework through a series of user-based studies, in which the opportunistic side of the tool was found to have significantly improved novice designers’ ability to evaluate designs. The preliminary framework presented in this paper establishes a foundation for future studies to refine the tool’s accuracy using more data and expert analysis.
Heat Transfer in an Injector-Scaled Additively Manufactured Fuel Passage
Authors: Walker Thomas D. , Bonham Clare
Published: September 2023

Knowledge of heat transfer in fuel wetted passages is important for informing injector design and life estimates due to the effects of temperature on fuel degradation. Future injectors will be manufactured using additive methods in an effort to reduce production costs and time, while also facilitating more agile design practices. Additive manufacturing (AM) is known to result in increased surface roughness compared to conventional manufacturing techniques, however limited data exists on how this roughness impacts heat transfer, particularly in liquid flows. This paper solves the inverse heat conduction problem for heat transfer coefficient in liquid flows through rough 90° channel bends typical of the pilot gallery in a lean direct-injection fuel spray nozzle. Heat transfer distributions across two rough surfaces are compared to an equivalent smooth surface. The two rough surfaces have different morphologies but have the same relative effective sand grain roughness which is matched to a prototype AM fuel injector. The sand grain roughness is predicted from a correlation that has been adapted for the high relative roughness scales characteristic of additively manufactured fuel passages. The effective sand grain roughness estimated from surface measurements of a prototype AM fuel gallery was ∼13 % of the passage hydraulic diameter. For the two rough surfaces, the heat transfer enhancement is up to three times the smooth surface value for the straight section preceding the bend and up to four times around the bend. Heat transfer distributions across the two rough surfaces are similar, but the magnitudes differ by ∼17 % depending on the surface morphology. This highlights the importance of the heat transfer effectiveness of surface features, which unlike the sand grain roughness is not matched for the two surfaces considered. Adjusting the data for differences in heat transfer effectiveness corrects the average heat transfer for the rough surfaces to within 7 %.
Updating Turbomachinery Aerodynamics Teaching on an Undergraduate Course Using 3D Design Tools
Authors: Ingram Grant
Published: September 2023

This paper outlines the update of a turbomachinery course to cover 3D aerodynamics using a Reynolds Averaged-Navier Stokes solver. Prior to the activities outlined in this paper the course was taught in a conventional way with a series of lectures and a timed, written, open book examination in a formal exam setting. Students were equipped with a calculator and set of notes including correlations from Howell and Soderberg. The students had around one hour to answer the turbomachinery question which was revealed to them only when they opened the paper at the start of the exam. This limited the depth of any aerodynamic problem they could get through and so they were restricted to simple design or analysis exercises.

The genesis of the course update was the release in 2017 of “MULTALL OPEN” [1] a freely available turbomachinery design system and this was adopted as the course software — although other software choices were considered.

Students now produce two turbomachinery designs during the course. These are both based on the J85 turbojet — largely to keep cycle calculations to a minimum but it was also important to ensure that students recognise that they were completing a real engineering task. The first task was a 3D aerodynamic design of multi-stage turbine which includes compressible flow, tip clearance and stacking techniques such as lean or sweep. The second task was a midspan (2D) compressor design. The exact cycle conditions were varied each year to explore design scenarios such as an increase in firing temperature. Assessment was by means of a short report where the best students report on their design choices, provide critical analysis of the design using appropriate post-processing techniques and compare their designs to the state of the art in the wider literature.

As well as describing the successes and challenges of the update to 3D design methods the paper provides some guidance for educators thinking about adopting a similar approach.
Heat Transfer and Film Cooling in an Aggressive Turbine Center Frame
Authors: Jagerhofer Patrick R. , Glasenapp Tobias , Patzer Bastian , Göttlich Emil
Published: September 2023

This paper investigates the heat transfer coefficient and the film cooling effectiveness in a turbine center frame (TCF). The TCF is a duct connecting the high-pressure turbine (HPT) to the low-pressure turbine (LPT) and is equipped with non-turning airfoils (struts). The TCF is operated in a product-representative 1.5-stage test turbine setup working under Mach-number-similarity. Upstream of the TCF, an unshrouded HPT is operated with four individually adjustable purge flow injections through the forward and aft cavities on the hub and tip of the rotor.

The heat transfer coefficient and the purge film cooling effectiveness are measured on the hub and the non-turning struts of the aerodynamically aggressive TCF using infrared thermography and tailor-made heating foils. To further extend the film cooling investigation, the seed gas concentration technique, in conjunction with the heat-mass transfer analogy, is used as a second film cooling measurement technique. Seeding the HPT cavities with different foreign gases reveals every individual purge flow’s contribution to the global film cooling effectiveness in the TCF. Additionally, the seed gas technique extends the investigated area for film cooling to the optically inaccessible shroud of the TCF.

The heat transfer in the TCF was found to be dominated by secondary flow features of the upstream HPT. Longitudinal streaks of alternating high and low heat transfer were found on the hub connected to the number and position of the upstream HPT vanes. A similar pattern was found in the film cooling effectiveness, where the film cooling streaks were situated between the high heat transfer streaks. The film cooling coverage on the shroud was found to be even, symmetric and superior to the hub cooling performance, with around 10% less usage of purge mass flow.
Dynamic Forced Performance of an O-Rings Sealed Squeeze Film Damper Lubricated With a Low Supply Pressure and a Simple Method to Quantify Air Ingestion
Authors: Rodríguez Bryan , San Andrés Luis
Published: September 2023

Contemporary squeeze film dampers (SFDs) in air breathing engines are short in length to limit weight and part count, and lubricated with a low feed pressure to reduce oil storage and pumping power. In SFDs, O-rings (ORs) restrict side leakage and increase the viscous damping while a adding a modest centering stiffness. Continuing a long-term project characterizing SFDs for aircraft engines and extending the original work in Ref [1], the paper details measurements of the forced performance of an OR sealed damper (OR-SFD) with diameter D = 127 mm, land length L = 0.2 D, and radial clearance c = 0.0022 D. Lubricant ISO VG 2 supplied at 0.69 bar(g) fills an upstream oil plenum and flows into the middle of the land through a single orifice configured with a check valve. Measurements of applied single-frequency dynamic loads, along with the ensuing damper displacements and accelerations serve to identify the parameters of the test structure, ORs, and SFD. The tests encompass centered whirl motions with amplitude r = 0.05c to 0.45c, and a range of whirl frequencies, ω = 10 Hz to 130 Hz. Note the squeeze velocity vs = rω reaches 102 mm/s. The ORs force coefficients are nearly invariant with frequency but do depend on the orbit amplitude. The ORs’ stiffness (KOR) decreases by 75% as the motion amplitude increases, r → 0.45c, likely due to the large elastic deformations and slow recovery of the ORs material. For small amplitude motions (r/c = 0.05 and 0.10), the ORs damping coefficient (COR) is ∼10% of the overall coefficient for the lubricated system (CL), while for r/c > 0.25, COR ∼ 0.03 CL. For small amplitudes of whirl (r ≤ 0.25c), the SFD experimental viscous damping (CSFD) and added mass (MSFD) coefficients, identified over a shorter frequency range (vs < 30 mm/s) equal theoretical magnitudes for a fully sealed damper. As the orbit size grows to r = 0.45c MSFD drops nearly 75% and CSFD decreases by ∼40% due to the onset of both lubricant cavitation and air ingestion occurring for squeeze velocities vs ≥ 24.5 mm/s, as also seen in the recorded dynamic pressures and video recordings of a bubbly mixture leaving the damper. A comprehensive flow model predicts CSFD and MSFD about 8% and 12% larger than the experimentally identified coefficients. A novel approach enables the estimation of the gas volume fraction (GVF) generated in the damper and which rapidly increases as vs grows. The simple procedure draws into a deflated balloon the material contents in the squeeze film, weighs the sample, and identifies its volume to produce an estimate of the GVF. The procedure to quantify the GFV will assist in the validation of predictive tools.
Test Campaign and Application Study for a High Pressure Compressor With Modular Rotor
Authors: Kurz Rainer , Srinivasan Anand , Goucher Sara , David Tim
Published: September 2023

Barrel style centrifugal compressors are widely used for high pressure gas compression applications in the oil and gas industry. Using a modular rotor in a high pressure centrifugal compressor for Oil and Gas Service is a method that is distinctly different from ubiquitous solid shaft machine designs. It is accepted in the governing standards, for example API 617, and allows for significant flexibility under changing operating requirements. Using a modular rotor allows to avoid splitting diaphragms, but it also requires different assembly, balancing and test methods. The machine described in this study is a single compartment compressor capable of 340 bar discharge pressure. The study provides aerodynamic test data for a series of closed loop tests at discharge pressures of over 220 bar, using Nitrogen, CO2 and natural gas as test gases, to validate compressor performance, rotordynamic stability and mechanical integrity. An important feature of the test campaign is the detailed evaluation of the transient behavior during tests to verify the machine integrity at rapid shutdowns at high discharge pressures. The paper also discusses the applications for such centrifugal compressors in the oil and gas industry, considerations on standardized designs, and its integration in a modular design system.
Performance Analysis of an Engine-Mounted Compression System for Aircraft Environmental Control
Authors: van Heerden Albert S. J. , Ippedico Salvatore , Rajendran David John , Anselmi-Palma Eduardo , Roumeliotis Ioannis , Pachidis Vassilios , Sharpe Richard , Howarth Nicholas
Published: September 2023

Environmental Control Systems (ECS) on civil transport aircraft constitute large portions of the secondary power demand. In this paper, an alternative compression system to the conventional two-port bleed design is presented, which can substantially lower the level of secondary power required for meeting the ECS demand. The concept presented is a novel engine-mounted cabin compression system (EMC2S). The potential benefits of the novel EMC2S over conventional systems are quantified and a multi-disciplinary approach, involving combined engine and aircraft performance analysis, is used to quantify the mission fuel burn of both conventional and novel EMC2S configurations for a reference mission. It is shown that, compared with a conventional system, an EMC2S can achieve up to a 0.72% reduction in fuel burn for a single-aisle short-to-medium-range aircraft with a year 2000 entry-into-service turbofan. Larger savings are expected for higher bypass ratio engines.
High Throughflow Design and Analysis for Streamvane Swirl Distortion Generators
Authors: Hayden Andrew P. , Gillespie John , Hefner Cole , Untaroiu Alexandrina , Lowe Todd
Published: September 2023

In recent years, the StreamVane technology has developed into a mature and streamlined process that can reproduce swirl distortion for ground-test evaluation of fan and compressor performance and durability. A StreamVane device consists of complex turning vanes that accurately output a distorted secondary velocity field at a defined distance downstream. To further advance the applications and conditions in which these devices operate, a research effort was developed and completed to investigate methods to increase critical Mach numbers. The effort was split into three separate stages: 1) Perform high fidelity computational fluid dynamics (CFD) to identify peak Mach number locations within twin and quad swirl vane pack designs; 2) Conduct thorough literature reviews on relevant high throughflow techniques; 3) Design and implement selected techniques to evaluate improvements using the same high-fidelity CFD methods. It was predicted that employing blade lean within high-speed vane junctions increased critical Mach numbers by 6.6%, while blade sweep resulted in a 3.5% increase. The results and conclusions from this effort are presented throughout this paper with a primary focus on comparing Mach numbers and swirl profiles between vane packs with and without high throughflow designs.
Aerodynamic and Rotordynamic Performance of a Multi-Stage Centrifugal Compressor With High Hub Impellers
Authors: Srinivasan Anand , David Tim , Silva Daniel , Rajagopalan Vinayaka , Kurz Rainer
Published: September 2023

Multi-stage centrifugal compressors with single shaft modular rotor designs are used extensively in the oil and gas industry. These compressors are designed to handle a wide range of speeds, flows and discharge pressures, in addition to handling a wide range of gas specific gravities. In this paper, low pressure test results are presented for a multi-stage centrifugal compressor with high hub impellers. Scaled results from a test rig are presented to validate the aerodynamic performance characteristics of a single stage of compression. The results of the scaled test rig are used to generate the performance characteristics of a family of impellers intended for use on the high-pressure compressor product line. A multi-stage compressor was built to validate the full-scale performance and the stage stack-up characteristics. Rotordynamic performance results of the free-free natural frequencies and unbalance response characteristics are presented for the full-scale compressor rotor. These results are used to validate the rotor-bearing models for the compressor rotor. Aerodynamic test results with discharge pressures up to 1,100 psia [76 bara] are presented. Test results obtained on nitrogen and carbon dioxide at multiple machine Mach numbers are also presented. The test results serve as a benchmark for the performance validation prior to intended usage at discharge pressures up to 4,900 psia [337 bara].
Interference of Unbalance on the Dynamic Characteristics of Cracked Rotor: An Experimental Research
Authors: Han Bing , Yan Peigang , Liu Zhansheng , He Peng
Published: September 2023

When the rotor of an aeroengine or gas turbine contains cracks, it produces abnormal vibrations. The abnormal vibration behavior of the cracked rotor can be used as the basis for crack fault diagnosis. However, in practice, the rotor itself cannot achieve absolute dynamic balance. Also, the operating environment in which the rotor is placed may contain unbalanced excitation. During the rotation of the cracked rotor, the existence of unbalance interferes with these abnormal vibration characteristics. Therefore, studying this process is of great significance for solving the issue of rotor crack fault diagnosis under unbalanced disturbance in engineering.

This study aimed to monitor the dynamic characteristics of a multi-disk rotor system with transverse cracks. An unbalanced mass was imposed at the disk. Precision wire cutting was used to prefabricate cracks on the rotor to maximize the simulation of fatigue cracks in the real industrial environment. During the test, the crack depth was from shallow to deep and the direction of the crack opening remained unchanged, while the direction of unbalanced force changed 360° along the circumferential direction of the disk. The experimental results showed that when the angle between the unbalanced force direction and the crack opening direction changed, the crack fault characteristics changed to different degrees. The effect of unbalance on crack fault characteristics was more obvious with the increase in crack depth.
The Effect of Unsteady Inlet Boundary Conditions on the Aero-Thermal Behavior of High-Pressure Turbine Vanes: A Numerical Study Using Scale-Resolving Simulations
Authors: Gründler Jonathan , Lehmann Knut , Schiffer Heinz-Peter
Published: September 2023

This paper presents the application of a novel method to prescribe unsteady boundary conditions to transient, scale-resolving Computational Fluid Dynamics simulations of the high-pressure turbine in modern jet engines. The methodology is based on the compression of the interface data at the Combustor Turbine Interface, using Proper Orthogonal Decomposition and Fourier Series (PODFS). Doing so can reduce the stored data at the interface drastically. The capability of the PODFS method to produce realistic inlet boundary conditions was demonstrated in previous work. Here, the method is applied to a turbine case. The outlet data of a combustor simulation is used to create the PODFS boundary conditions for a scale-resolving simulation of a simplified first Nozzle Guide Vane of the high-pressure turbine. This simulation is compared with simulations with steady-state boundary conditions to show the effect of unsteadiness in the inlet boundary condition on the aerodynamic and thermal behavior of the turbine. While the aerodynamics show minor sensitivity against the way of applying the inlet boundary conditions, the thermal behavior of the vanes is strongly affected by the modeling of combustor unsteadiness.
Shape Optimization of a Cooling Hole Using Improved Metamodeling Techniques and Workflow
Authors: Norman Adam , Arguinzoni Carlo , Sharma Kalyan , Cunningham Pat , Joshi Dibesh
Published: September 2023

In modern day gas turbine hot sections, active cooling of liner walls is critical due to extremely high temperatures and long continuous operation. A secondary flow can be introduced that shields the metal surfaces by forming a film increasing the durability and life of the liner. Typically, this cooling flow is mixed with the mainstream by a series of holes or slots along the length of the liner wall. In the past, typically, these effusion holes were cylindrical. However, as the hot section temperature increases, more advanced hole designs are necessary for increased cooling effects.

Determining an optimal hole design is costly and time-consuming if approached with standard experimental trial-and-error techniques. Numerical tools can aide in optimization studies, but for complex transient flows requiring scale-resolving methods, simple optimization methodologies require thousands of design points and can take extended periods of time to complete.

In this study, a metamodel-based optimization of a shaped cooling hole is demonstrated in an automated workflow. The automated workflow consists of six geometrical hole parameters being investigated at flow conditions akin to the hot section at a constant blowing ratio. These six parameters completely define the shape of the hole leading to a complete optimized design for maximum cooling effectiveness. The metamodel is based on data from a stress-blended eddy simulation (SBES). To construct the meta-model, an adaptive technique is used that employs machine learning (ML) algorithms to minimize the number of required design points by dynamically modifying the design space sampling based on the gradients in the response. As part of the metamodel generation, a sensitivity analysis is performed to eliminate geometry parameters which do not influence the cooling effectiveness.

The optimization study is done in two parts: the first part involves an evolutionary algorithm-based optimizer which runs the fast-running metamodel through multiple design points to identify potential optimal solution candidates; the second part involves validating the candidate designs using actual solver calls. This two-pronged approach drastically reduces the time to achieve optimal effusion hole design while ensuring that the design space is explored thoroughly. Overall, this work demonstrates the enhanced optimization capabilities and timeline compression of a shaped cooling hole.
Performance Evaluation of Additively Manufactured and Hybrid Indexable Milling Tools in Machining of AISI4140+QT and Ti-6Al-4V
Authors: Kelliger Tobias , Meurer Markus , Bergs Thomas
Published: September 2023

Additively manufactured (AM) cutting tools enable new design concepts in tool development concerning lightweight construction, damping behavior and internal cutting fluid supply. So far, the impact of the layer-by-layer manufacturing technique onto the tool performance during machining of aerospace materials is widely unknown. In this study, the performance characteristics of AM indexable milling tools were investigated and compared to a conventionally manufactured tool of the same geometry. The AM tools were manufactured by Laser Powder Bed Fusion (LPBF) from a newly developed bainitic steel alloy. All tools were analyzed with two main focuses. Outside the machine tool, geometrical characteristics and mechanical properties were taken into account. Inside the machine tool, during roughing of AISI4140+QT (42CrMo4+QT) and Ti-6Al-4V (ASTM Ti-Grade 5), tool wear, cutting forces, surface roughness and vibration behavior were evaluated. Three tool concepts were compared, a conventional tool, an AM tool and a hybrid tool with a conventionally manufactured preform and an AM head. Differences in the performance behavior could be traced back mainly to geometrical inaccuracies caused during post-processing of the tools. Thus, LPBF manufactured basic bodies seem to meet the requirements as application for indexable milling tools. Based on this work, future investigations using AM cutting tools can be carried out assuming a negligible influence of the manufacturing technique onto the tool performance during machining.
Supercritical Carbon Dioxide Shock Behaviour Near the Critical Point
Authors: Wang Jinhong , Cao Teng , Martinez-Botas Ricardo
Published: September 2023

This paper aims to provide an understanding of sCO2 inviscid adiabatic normal shock behaviour near the critical point and to develop an explicit tool for faster prediction of the shock relations that can aid the supercritical turbomachinery design process. An iterative algorithm was developed to compute shockwave behaviours for non-ideal fluids. Three important shock behaviour parameters were investigated: post-shock Mach number, shock strength, and polytropic efficiency. A comparative study was carried out between air (ideal gas assumption), ideal gas CO2 (ideal gas assumption), and non-ideal fluid CO2 (Span-Wagner equation of state). The distinct differences show the inadequacy of the perfect gas shock relations when predicting sCO2 shock behaviour near the critical point. The results of non-ideal fluid calculations show a general trend of stronger shock strengths and higher polytropic efficiencies towards lower pre-shock entropy conditions. This is also distinctive near the critical point due to the reduced speed of sound. Finally, explicit expressions for these parameters were retrieved using symbolic regression. The fitted models have significant improvements compared to the prediction from perfect gas shock relations with a 5–20% point reduction in relative errors. This study also shows the potential for machine learning to be applied in non-ideal fluids effects modelling and the methodology developed in this paper can be easily introduced to other working fluids in their ranges of interest.
Challenges in the Application of Hot-Wire Anemometry for the Investigation of Transient Temperature Fluctuations in a High-Speed Research Compressor
Authors: Schäffer Christian , Rabl Alexander , Speck Konstantin , Boetzel Kiyan , Helcig Christian , Gümmer Volker
Published: September 2023

This paper presents an investigation into the principles of unsteady total temperature measurement with a parallel hot-wire while also examining potential challenges that might occur when using a custom-made hot-wire in a High-Speed Research Compressor.

After modifying the institute’s open free-stream calibration tunnel with a pressure chamber to enable the calibration of hot-wires at compressor-representative conditions, different approaches for extracting the total temperature from the hot-wire raw data were evaluated. The comparison of the ‘optimized King’s law’, ‘Lienhard & Helland method’ and a new polynomial approach revealed reasonable results with similar accuracy, whereas the polynomial concept requires less calibration effort. When measuring with the hot-wire in the research compressor, significant disturbances were caused due to vibrations. After several mechanical modifications at the prongs, probe holder and probe guidance, followed by a visual inspection with a high-speed camera, it was concluded, that wire strain gauging occurred due to prong vibrations. This difficulty could be avoided by welding the wires with less tension and a noticeable slack.

Finally, the effect of wire contamination was investigated. After two hours of testing, particle accumulation shows potential of having a significant effect on the measurement results in open-loop test rigs.
Numerical Investigation of the Influence of the Degree of Reaction in an Axial Compressor Stage With Tandem Vanes
Authors: Giannini Samuele , Luz Guilherme M. , von Jeinsen Philipp , Straccia Mattia , Gümmer Volker
Published: September 2023

Many investigations have defined Smith-type diagrams to guide the preliminary designs of conventional axial compressor stages on the choice of loading, flow coefficient, and degree of reaction. The recent development of unconventional axial compressor stages with tandem vanes has not been accompanied by similar works aimed at tailoring existing correlations to the new type of vanes. While it is clear that axial compressor stages with tandem vanes operate in higher working ranges than conventional stages, it is less clear how the choice of reaction affects the aerodynamic behavior of such setups. Recent works have shown that higher work coefficients would require higher degrees of reaction thanks to the centrifugal effects’ beneficial influence on the rotor’s boundary layer. However, the interaction of tandem vanes with such phenomena is still not fully understood. For this purpose, this paper numerically investigates a low-speed axial compressor stage developed at the Technical University of Munich with different degrees of reaction for increasing loading levels. The metal angles of the unshrouded rotor and the shrouded stator are modified to ensure that the other design parameters of the stage, namely the work and flow coefficients, are kept constant and that the influence of the degree of reaction is isolated. The investigation starts with Q2D simulations of the reference midspan aerofoils, and it is then extended to a 3D configuration by maintaining the radial distribution of the aerofoil parameters together with the lean and bow distributions of the reference 3D vanes. New correlations are presented, aiming to show how the performance of the stage in terms of efficiency, total pressure losses, and loading coefficients of the vanes are influenced by the different degrees of reaction investigated. This paper therefore provides insight into the preliminary choices of parameters for the design of axial compressor stages with tandem vanes.
Flame Speed Measurements of Ammonia-Hydrogen Mixtures for Gas-Turbines
Authors: Yovino Louis , Kim Gihun , Rahman Ramees K. , Pierro Michael , Vasu Subith S. , Winquist Mark , Subbaraman Ganesan , Steele Robert
Published: September 2023

Recent findings from the US Energy Information Administration (EIA) project an increase in domestic fossil fuel consumption (e.g., petroleum, natural gas) and global greenhouse gas (GHG) emissions through 2050 [1]. Consequently, advanced combustion research aims to identify fuels to mitigate fossil fuel consumption while minimizing exhaust emissions. Ammonia (NH3) is one of these candidates, as it has historically been shown to provide high energy potential and zero carbon emission (CO and CO2) [2]. As a hydrogen (H2) carrier, NH3 serves as a possible solution to the U.S. Department of Energy’s (DOE) Hydrogen Program Plan by providing efficient H2 storage and conservation capabilities [3]. As a result, applied turbine-combustion research of NH3 and H2 fuel has been conducted to identify combustion performance parameters that aid in the design of sustainable turbomachinery [4]. One of these key combustion parameters is the laminar burning speed (LBS). While abundant literature exists on the combustion of NH3 and H2 fuels, there is not sufficient evidence in high-pressure environments to provide a comprehensive understanding of NH3 and H2 combustion phenomena in turbine-combustor settings. To advance the state of the knowledge, NH3, and H2 mixtures were ignited in a spherical chamber across a range of equivalence ratios at 296 K and 5.07 Bar (5 atm) to understand their flame characteristics and LBS which was determined using a multizone constant-volume method. The experimental conditions were selected according to primary turbine-combustor conditions, as much research is needed to support NH3-H2 applicability in turbomachinery for power generation. The effect of H2 addition to NH3 fuel was observed by comparing the LBS for various NH3-H2 mixture compositions. Experimental results revealed increased LBS values for H2 enriched NH3, with the maximum LBS occurring at stoichiometry. The experimental data were accurately predicted by the UCF NH3-H2 mechanism developed for this investigation, while NUI 1.1 simulations overestimated recorded LBS data by a significant margin. This study demonstrates and quantifies the enhancing effect of H2 addition to NH3 fuels via LBS and strengthens the literature surrounding NH3-H2 combustion reactions for future work.
Novel Additively-Manufactured and Internally-Cooled Airfoils for Increasing Small Industrial Gas Turbine Efficiency
Authors: Searle Matthew , Roy Arnab , Ramesh Sridharan , Floyd Timothy , Ames Forrest E. , Straub Douglas
Published: September 2023

The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) has tested the cooling performance of baseline and advanced additively manufactured (AM) airfoils for small industrial gas turbines. This study is a first step to increase market penetration of gas turbine-based combined heat and power (CHP) systems by increasing gas turbine efficiency through a 100 °C increase in turbine inlet temperature, where the turbine inlet temperature gain is enabled by AM cooling architectures. The baseline designs consisted of state-of-the-art blade and vane designs, while advanced concepts included the NETL Double Wall, incremental impingement, and lattice designs.

Tests were performed at NETL in the conjugate aerothermal test (CAT) facility, which is a visually-accessible, heated, wind tunnel with an independent coolant plenum. Spatially resolved overall cooling effectiveness was measured using infrared (IR) imaging, and the results accounted for reflection and IR window transmission losses.

To evaluate the design performance, baseline (0.28) and advanced overall cooling effectiveness (0.37), targets were established from system models. Results for overall cooling effectiveness (both average and 99th-percentile) for the baseline and advanced designs (five total) were plotted versus a non-dimensional heat load parameter (HLP) varying from 0.5 to 3.5. The minimum HLP to keep 99% of the blade surface temperature of the baseline blade, incremental impingement, and NETL Double Wall at or below the maximum metal temperature for the advanced target was 3.22, 2.83, and 1.36, respectively.

The success of the NETL Double Wall was attributed to the staged coolant addition along the airfoil chord. Poor cooling performance on the leading edge of the incremental impingement design due to inadequate leading edge plenum sizing prompted a redesign, which will be reported in future work.
A CFD-Based Small-Scale Combustor Design Optimization Utilizing a Many-Objective Evolutionary Algorithm
Authors: Briones Alejandro M. , Paxton Brendan T. , Rankin Brent A.
Published: September 2023

This work demonstrates the capability of an open-source autonomous computational fluid dynamics (CFD) meta-modeling environment (OpenACME) for optimizing small-scale combustor designs. OpenACME couples several object-oriented programming open-source codes for CFD-assisted design using a decomposition-based many-objective evolutionary algorithm (MaOEA). The CFD is based on steady, incompressible, three-dimensional simulations with k-ω SST RANS and flamelet/progress variable combustion model. There are five unconstrained design variables based on combustor liner dilution hole diameters. The CFD results are compared with existing experimental data in terms of combustion efficiency as a function of severity. The comparison demonstrates that the CFD methods capture combustion efficiency trends. Next, more than 500 combustor designs are evaluated with OpenACME. A Pareto Frontier is generated in terms of combustion efficiency, pattern factor, and total pressure losses. Pseudo weights are used to select a non-dominated Pareto Frontier design point for future fabrication and experimental testing. OpenACME is demonstrated to be a viable tool for small-scale combustor design optimization.
CFD Simulations of the Unsteady-State Flow Through a 1.5-Stage High-Work Turbine
Authors: Hansen Thorsten , Munktell Erik , Scheuerer Georg , Zhuang Qingyuan , Zwiener Kim
Published: September 2023

Behr et al. [1] have experimentally investigated the unsteady-state flow and clocking effects in a 1.5-stage high-work turbine. Their test rig had a first stator row with 36 blades, a 54-bladed rotor at 2,700 rpm, and a second stator row with 36 blades. They studied four different stator-clocking positions. The present paper computationally investigates the unsteady-state flow through the 1.5-stage turbine by performing CFD simulations with the Simcenter STAR-CCM+ software. The mathematical model of the simulations consisted of the ensemble-averaged unsteady-state mass, momentum and energy equations complemented by the SST turbulence model. The authors applied a quality assessment procedure to the computational results before comparing them to the experimental data and reported the numerical accuracy in the form of the Grid Convergence Index (GCI). The results showed an increase in the calculated efficiencies of the unsteady-state over the steady-state results, bringing data and simulations closer. The total pressure contours at the rotor and second stator exit planes also agreed well with the experiments. Finally, the paper includes simulations of the effects of different stator-clocking positions. The results showed a similar response to the change in stator-clocking position as the experiments.
Measurement of Soot Volume Fraction and Temperature Fields of an Axisymmetric Flame Using an Iterative Image Recreation Method
Authors: Chernov Victor , Cruz Juan Jose , Escudero Felipe , Fuentes Andres
Published: September 2023

A method to recreate an image of a virtual sooting flame is presented. To do this, a spatial field of soot volume fraction and temperature is needed. It is assumed that the dominant emission mechanism is grey body radiation and that the primary soot particles are below the Rayleigh limit. If the spectral and intensity responses of a camera are known, it is possible to recreate the image of the flame by integration of the radiation along the line of sight. The measurement of the soot volume fraction and the temperature is done iteratively — a first guess is proposed, an image is constructed and compared to the real image. If images are different, the soot volume fraction and temperature fields are adjusted and the process is repeated. The iteration procedure is explained. The method is tested on a co-flowing laminar diffusion flame of ethylene and air. The results are compared to other, more established methods. It appears that the proposed method reproduces well soot volume fractions, while there is a noticeable disparity in the temperature results.
Structural Characterization of a Rapid-Prototyped Inlet Particle Separator Model for Aerodynamic Lab Testing
Authors: Castaldi Marco , Mayo Ignacio , Demolis Jacques , Eulitz Frank
Published: September 2023

Inlet Particle Separators (IPS) are filters installed in helicopter and turboprop engines to prevent the ingestion of dust, sand and other debris when operating in extreme conditions. However, the performance and limitations of those systems have to be investigated before their installation in the aircraft. For this reason, the IPS testing is a primary concern for engine manufacturers: unfortunately, the organization of conventional experimental campaigns might be too lengthy and in conflict with the stringent industrial timescales. Hence, the IPS can be fabricated by means of polymer additive manufacturing to shorten the testing cycle time and reduce costs, but this poses a threat in terms of mechanical rig integrity. This paper proposes a complete approach for the structural characterization of an IPS made of FullCure720 and HP PA 11, analyzed using the same tools and procedures of classical metal structures. This method employs fluid structure interaction to ensure safe operability during testing, and can be applied in early design phases to plan low-risk experimental campaigns. Starting from the structural collapse of the rig at high Reynolds number, its safety under both steady and unsteady loading conditions is assessed. The maximum inlet total pressure allowed in the system is determined and some structural reinforcements are analyzed to prevent failure in future tests. The results confirm the existence of weak regions even with stiffer components, and the impossibility of operating the facility at high Reynolds number with the current design.
Aerodynamic Forcing Analysis of Aerodynamically Mistuned Outlet Guide Vane Assemblies
Authors: Merson Jacob , Stapelfeldt Sina
Published: September 2023

The next generation of aero engines feature a more compact design with a shorter distance between the fan rotor and bypass outlet guide vane (OGV) assembly. As such, potential forced response due to rotor-stator interactions has become a more significant concern with regards to high cycle fatigue and component lifespan. It has been shown that deploying a non-axisymmetric OGV configuration is able to reduce the first engine order (1EO) forcing on the fan’s blades.

This paper explores the effects that a non-axisymmetric OGV configuration has on the aerodynamic forcing on the vanes themselves. A low pressure system representative of a modern low-speed fan with different non-axisymmetric OGV patterns is simulated and forcing amplitudes on the OGV stator vanes recorded. Six different non-axisymmetric patterns are generated: three with sinusoidally distributed varied stagger angles of up to 1, 2, and 4 degrees with a one-lobed (circumferential wavenumber m = 1) pattern and an additional three with the same stagger angle distributions with a two-lobed (m = 2) pattern. The forcing in assembly modes and on individual blades are analyzed, and the forcing amplitudes compared to those of the tuned (i.e. identical) OGV configuration. It is shown that aerodynamically mistuning an OGV assembly typically results in a relative increase in forcing amplitudes on most of the individual OGVs, with a maximum forcing amplitude increase of 50% on specific OGVs when configured in the two-lobed, 4 degree re-staggered sinusoidal pattern.
Flow Interaction Between Cascade and Flow Resistance Medium
Authors: Lin Tong , Sarimurat Mehmet , Dang Thong Quoc
Published: September 2023

This paper investigates the effects of flow-interaction between a rotor and a high-resistance medium (HRM) on both rotor and system performance within the 2D cascade limit using computational fluid dynamics (CFD). Two configurations were studied: the Rotor/HRM configuration, where the HRM is located downstream of the rotor, and the HRM/Rotor configuration, where the HRM is located upstream of the rotor. The results indicate that fan performance increases from the interaction effect, along with an extension of the stall margin. However, the pressure drop across the HRM is increased due to an increase in velocity magnitude and non-uniformity, which can lower system overall performance. In the HRM/Rotor configuration, the presence of an upstream close-coupled HRM induces a high-velocity jet around the blade which is more significant on the suction surface and appears to delay flow separation, resulting in an extension of the stall margin. In the Rotor/HRM configuration, the boundary-layer thickness on the blade surfaces is reduced, resulting in delaying stall. In both cases, flow non-uniformity and the presence of swirl velocity in the HRM increases the pressure loss across it.