bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Investigation of Stator-Less and Blade-Less Radial Expander
Authors: Renuke Avinash , Traverso Alberto , Reggio Federico , Pascenti Matteo , Silvestri Paolo 
Published: September 2023

Abstract
Interests in small-scale turbomachinery are gaining momentum, particularly around waste heat recovery using Organic Rankine Cycle (ORC), energy harvesting, pico-hydro, refrigeration and heat pumps and small-scale power generation. These applications demand to have economical, simple construction, and reasonably efficient machines. The performance of bladed turbomachine at a small scale is poor mainly due to viscous losses and relatively large clearances. In some cases, like ORC, it requires a lubrication system, making it complex and costly. Bladeless or Tesla turbomachinery is seen as one of the solutions for these applications due to its simple construction and cost-effectiveness. However, the experimental efficiency of the bladeless turbines/compressors is found in the low region, &lt; 40%. In this article, the performance of a bladeless turbine is investigated using a vaneless volute configuration, making the turbine stator-less (vaneless volute) and bladeless (vaneless rotor). This study presents numerical and experimental performance investigation with a volute as a stator of the bladeless rotor. 3D Numerical results show very promising performance of the turbine with total to static efficiencies calculated above 65%. In the second part of the article, turbine prototype components, assembly and test set-up are discussed. Experimental maximum efficiency of 41.5±0.88% at 3.5 kg/s@5000 rpm and power of 915 W is obtained. This is the highest recorded efficiency for the Tesla turbine in peer-reviewed research. The overall turbine performance from 3D numerical simulation with ventilation and mechanical losses is compared with experimental results. This work demonstrates that the proposed stator-less/volute configuration provides an efficient way for bladeless or Tesla turbines, particularly for low-head applications.
Optimization of Variable Geometry Turbine Electric Turbocharger for a Heavy-Duty, On-Highway Fuel Cell
Authors: Taylor Alexander H. , Naik Pavan , Nibler Simon , Al-Hasan Nisar 
Published: September 2023

Abstract
An air compressor is a necessary component on fuel cell electric generators as fuel cells do not pull in air without an external intervention. There are many fuel cell air compression options, each with their own benefits and drawbacks, such as roots-style screw compressors, radial e-compressors, e-turbos with wastegate, and e-turbos with a variable geometry turbine (VTG). Turbocharger turbine wheels for internal combustion engine applications are optimized to maximize exhaust gas enthalpy extraction while limiting centrifugal forces in the blades. In the presence of high temperature exhaust gas, 950–1050° C for gasoline engines, material strength decreases, elasticity increases, and thus induced stresses must be reduced to prevent turbine failure or contact with the turbine housing. The proton exchange membrane fuel cell (PEMFC) exhaust gas temperature is significantly lower, in the range of 85–90° C, which enables more degrees of freedom in the design and thereby a higher thermodynamic efficiency of the turbine. This work proposes a variable geometry turbine specifically for the fuel cell environment, and compares system performance through 1-D simulations at a lower-power road load and rated power point, to i) baseline electric compressor (e-compressor), ii) electric turbo (e-turbo) with wastegate turbine, & iii) e-turbo with VTG designed for an IC engine environment. The VTG turbine optimized for fuel cell enthalpy harvesting has 13%-points higher efficiency at rated power compared to that of a typical ICE VTG, a relative increase of 23%. This study finds an optimized VTG e-turbo improves PEMFC efficiency at rated power by 3%, or 1.5%-points, compared to the e-compressor without a turbine.
Steam Turbine Casing Analyses to Determine Pressure and Temperature Limits – Crossover Piping and Pipe Flanges
Authors: Smith Paul T. , Schirato Jason , Neil Adam R. , Griffin Daniel J. 
Published: September 2023

Abstract
To ensure safe and reliable operation, steam turbine casings and piping must have acceptable stresses and maintain sealing when subjected to internal pressures and temperatures. Analysts conduct structural evaluations using finite element analysis (FEA) techniques to show acceptance. This paper outlines the analytical methods used to perform these types of analyses, provides analysis examples, and summarizes the process to create pressure and temperature limit maps.
Finite element models determine pipe loads and stresses from static structural analyses for normal operation and hydro test conditions, and transient analyses for heat-up and cool-down conditions. As part of the turbine model, the piping is evaluated for stress acceptability when subjected to internal steam pressure and temperature. The pipe flanges are reviewed for sealing capabilities and consider the effects of bolt stress relaxation at elevated temperatures, joint contact surface separation, and penetration of the internal pressure into the sealing surface.
A series of analyses on the pipe and pipe flange models we re used to create pressure and temperature limit maps. These maps allow an engineer to determine the acceptability of the piping for a particular application.
Investigating the Mixture Quality in Multi-Injector Burner Systems, Part II: Model Application
Authors: Marquez Macias Fabian , Hirsch Christoph , Sattelmayer Thomas , Huth Michael , Meisl Jürgen 
Published: September 2023

Abstract
Multi-injector burner systems offer a high spatial-temporal mixture homogeneity due to their small size and thus have a high NOx emission reduction potential at increasing flame temperatures. This potential is reduced due to the sensitivity of the mixing quality to inflow distortions caused by the flow path in the burner head. A deep understanding of the link between the inflow conditions and the mixture quality helps to optimize the flow field upstream of the injectors within the spatial and pressure loss constraints of gas turbine combustors to obtain minimal NOx emissions. This paper presents a new model approach for determining the mixture quality in multi-injector burners with output-based Proper Orthogonal Decomposition (O-POD). The sensitivity to the inflow distortion is considered with the so-called observable vector, which describes the injector inflow conditions and is given as model input. The target quantity is the Probability Mass Function (PMF) of the equivalence ratio at the injector outlet. This model allows a fast estimation of the mixing PMF for arbitrary inflow conditions, which is otherwise only accessible with complex time-resolved experimental or numerical approaches. The performance of the model was demonstrated with 21 reference datasets, for which a good agreement between the experimental results and the model output was obtained.
Numerical Investigation of the Flow Structure of Cryogenic Hydrogen in Corrugated Metal Flexhoses Due to Fluid Structure Interactions
Authors: Tran Patrick K. , Congiardo Jared F. , Fortier Craig R. , Fernandez Erik , Kapat Jayanta S. 
Published: September 2023

Abstract
In this paper, details of flow field characteristics and pressure drop of cryogenic hydrogen in corrugated metal flexhoses will be numerically evaluated using multiphase flow physics coupled with fluid structure interactions. Multiphase flow regime is often influenced by concentration ratio, shape factor, and orientation of the piping. Corrugated metal flexhoses are commonly used as part of cryogenic commodity transportation for their ability to operate in a large range of temperatures and pressures with a high degree of geometric flexibility. These sharp changes in the geometry of the flexhose convolutions are one of the leading factors of liquid and gas phase entrainment which can significantly reduce the efficiency of piping systems and fuel delivery systems to the engine components. The entrained gas phase hydrogen can eventually propagate in successive convolutes leading into the permanent entrapment of the gas phase hydrogen in the corrugations. The volume fraction up to 5% gas phase with various convolute heights and pitch will be evaluated, with a hose length to diameter ratio (L/D) range between 20 to 60 and a Reynolds number range between 5,000 to 350,000 based on the hose hydraulic diameter. The findings of the study contribute to a better understanding of multiphase flow physics of hydrogen in corrugated metal flexhoses.
A Comparison of Flow Path Designs for Axial Turbines Operating with Pure CO2 and CO2 Mixtures
Authors: Salah Salma I. , White Martin T. , Sayma Abdulnaser I. 
Published: September 2023

Abstract
Supercritical CO2 (sCO2) mixtures have been found to be promising for enhancing the performance of power cycles for concentrated solar power (CSP) applications, with up to a 6% enhancement in cycle efficiency compared to a simple recuperated CO2 cycle depending upon the mixture and cycle configuration chosen. Given that turbine efficiency significantly affects the overall plant performance, it is important to confirm whether turbines operating with CO2 mixtures can achieve the same efficiencies compared to pure CO2, whilst exploring whether the use of mixtures introduces any differences in the turbine design. This study aims to investigate the differences in turbine flow path designs produced for pure CO2 compared to CO2 mixtures, whilst taking into account aerodynamic, rotordynamic and mechanical design aspects, as assessed during the mean-line design process. The aim of this study extends to evaluating the effect of key turbine design variables, such as the loading coefficient, flow coefficient and degree of reaction, on the flow path design and overall aerodynamic performance. Multiple flow path designs have been produced for axial turbines operating with pure CO2 and mixtures of CO2 with titanium tetrachloride (TiCL4), hexafluorobenzene (C6F6) and sulphur dioxide (SO2) for installation in a 100 MWe CSP plant. It is found that turbines operating with either pure CO2 or CO2 mixtures result in overall total-to-total efficiencies in excess of 92.5%; where the highest turbine efficiency is achieved for the turbine operating with pure CO2, whilst this reduces by a maximum of 1.1 percentage points for the CO2/TiCL4 mixture. This reduction in efficiency is because the CO2/TiCL4 turbine is limited to a maximum of six design stages in order to meet the imposed mechanical design criteria, whilst the pure CO2 turbine can accommodate thirteen stages leading to higher aerodynamic efficiency. The difference between the two cases is the result of a higher mass-flow rate for the CO2/TiCL4 mixture (66% greater than for pure CO2), which results in high rotor bending stresses and limits the number of stages to comply with the design criteria. It is also found that designing the turbine at loading and flow coefficients of 0.8 and 0.6 respectively, whilst fixing the degree of reaction and pitch-to-chord ratio to values of 0.5 and 0.85 respectively, resulted in an efficiency enhancement of 0.2% with respect to a baseline design produced at loading and flow coefficients of 1.0 and 0.5. This increase is due to being able to increase the number of stages from eleven to fifteen. This indicates that there is not much benefit in modifying key design parameters to improve the turbine efficiency as the 0.2% efficiency enhancement is considered within the margin of accuracy of mean-line flow path design.
Effect of Heat Treatment on the Morphology of γ′ Precipitates in LW 4275 and LW 4280
Authors: Jena Ashutosh , Gontcharov Alexandre , Lowden Paul , Brochu Mathieu 
Published: September 2023

Abstract
This study investigates the microstructural evolution of the γ′ precipitates in precipitation hardened Ni-based superalloys LW 4275 and LW 4280 comprising 5.2–5.5 wt. % Al, fabricated by laser powder bed fusion. The as-built microstructure established the presence of discrete carbides, while no signs of γ′ precipitates were present in either LW 4275 or LW 4280 specimens due to a high cooling rate of ∼1e+6 °C/sec. Both specimens were heat treated under a sub-solvus temperature of 1080 °C and super-solvus temperature of 1150 °C, which was established by Thermo-Calc modeling, followed by aging at 705 °C for 24h. Scanning electron microscope (SEM) examinations of samples subjected to sub-solvus heat treatment revealed that the size and volume fraction of the primary γ′ increased while the size and volume fraction of the secondary γ′ decreased as the solutionization period increased from 4 to 24h. Studies of the samples subjected to the super-solvus heat treatment revealed that the volume fraction and size of the γ′ precipitates increased with the increasing solutionization time from 4 h to 24h for both alloys. Finally, a detailed investigation of the morphological evolution of γ′ precipitate after both types of heat treatments was addressed.
Oxidation Performance of Fe-Ni-Co-Cr-Mn High Entropy Alloy and its Al-Containing Variants in Supercritical CO2
Authors: Ilinich Margarita , Huang Xiao , Zanganeh Kourosh 
Published: September 2023

Abstract
In this study, a new material type, known as high entropy alloy (HEA), is being evaluated for use in supercritical CO2 (sCO2) Brayton power cycle. This cycle is a promising power generation technology that offers an increased efficiency and smaller footprint compared to the conventional Rankine steam cycle. However, the construction of components that operate in the high temperature and pressure regions of the cycle requires the use of expensive high-performance alloys such as Inconel 740H and Incoloy 800HT. As an alternative to these alloys, three compositions of HEAs are evaluated, namely, FeNiCoCrMn (HEA-1), FeNi1.5CoCrMnAl0.5 (HEA-2), FeNi1.5CoCrAl0.5 (HEA-3). The alloy samples were exposed to sCO2 at 700 °C, 20 MPa for 600 hours. They were then evaluated through weight measurements and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The results showed that HEA-3 outperformed the two other compositions. It experienced an impressively low mass gain of 0.04 mg/cm2, compared to 0.65mg/cm2 and 0.25 mg/cm2 for HEA-1 and HEA-2, respectively. The lack of Mn enabled HEA-3 to form protective Cr2O3 oxides, whereas the other two compositions formed porous oxides containing MnO and Mn3O4. Furthermore, the results showed that HEA-3 has the potential to outperform many conventional superalloys being evaluated for sCO2 applications. Additional test campaign has been planned to study the effects of prolonged exposure of HEA-3 to high temperature and pressure sCO2 environment to further assess its performance and to do initial benchmarking with respect to other Ni-based alloys.
Design of Aerodynamically Balanced Transonic Compressor Rotors
Authors: Lefas Demetrios , Miller Robert J. 
Published: September 2023

Abstract
This paper describes a simple and efficient physics-based method for designing optimal transonic multistage compressor rotors. The key to this novel method is that the spanwise variation of the parameter which controls the three-dimensional shock structure, the area ratio between the throat and the inlet, ‘Athroat /Ainlet’, is extracted directly from the 3D CFD. The spanwise distribution of the area ratio is then adjusted iteratively to balance the shock structure across the blade span. Because of this, the blade design will be called ‘aerodynamically balanced’. The new design method converges in a few iterations and is physically intuitive because it accounts for the real changes in the 3D area ratio that directly controls the shock structure. Specifically, changes in both the spanwise 3D flow and in the rotor’s operating condition; thus aiding designer understanding. To demonstrate this, two example design cases are shown in the paper. A transonic rotor within a multistage civil compressor with variable upstream stator vanes, and an embedded rotor within a multistage military fan. The method is shown to: (1) improve both the operating range and the design efficiency while retaining the compressor’s overall matching, and (2) allow a balanced design to be simultaneously achieved at multiple shaft speeds. The result is a method which simplifies the multistage transonic compressor rotor design process and therefore has great practical utility.
Influence of Rotor Blades on Convergent-Divergent Nozzle Aerodynamics and Overall Supersonic Turbine
Authors: Moroz Leonid , Burlaka Maksym , Yudin Aleksandr 
Published: September 2023

Abstract
Single-stage axial pressure compound and two-row velocity compound supersonic turbines have a very high specific work, which allows for high power levels at high-pressure ratios and small flow rates in a very compact dimensional envelope. However, despite their mechanical simplicity, the supersonic aerodynamic effects in these turbines are very complex. There are many design and analysis methodologies for these turbines, which are currently used in the industry. Nevertheless, several important parameters are still insufficiently investigated. In an earlier paper (GT2022-83387), the authors considered the influence of convergent-divergent nozzle arrangement parameters on aerodynamic losses and overall supersonic turbine performance, which partially closed the knowledge gap. However, the flow at the nozzle ring’s exit is influenced by the rotor blades, especially by the geometry of the blades leading edge; axial clearance between the nozzle and rotor cascades; and a combination of other nozzle arrangement parameters at different Mach numbers. This is not well studied and needs to be further investigated, which will be the focus of this paper.
This paper examines the qualitative and quantitative influence on aerodynamic losses of the rotor blade, such as the leading edge geometry; axial clearance; and meridional flow angle at the exit of convergent-divergent conical nozzles. The methods utilized to determine the influence of these parameters are provided and the results are discussed. An approach to incorporate the quantitative corrections of the nozzle loss models is presented and a comparison with experimental data is performed. The incorporated models allow for designing and analyzing the supersonic turbines considering more parameters enabling the opportunity to fine-tune the design to specific requirements with higher confidence and accuracy.
Choking Handling in a 1D Compressor Modelling Fully Integrated in Engine Performance Simulations
Authors: Ruiz Domingo Javier 
Published: September 2023

Abstract
For engine performance modeling, industry standard is using turbomachinery 0D maps. With this approach, compressors are modeled as a “black box” providing the output parameters as a function of the input parameters regardless of the number of stages.
These 0D maps are only valid at the reference conditions used to obtain the maps, which include : the variable geometry settings (IGV/VSV), clearances, blade untwist, Reynolds number, specific heat ratio, intermediate bleeds, etc. When the 0D map is used at off reference conditions, it has to be used with correction factors that take into account the change between the reference conditions of the map and the actual ones.
These correction factors are applied as a development of the compressor 0D map in Taylor series, where only the first perturbation term is kept. Therefore, there is no cross terms between effects, even if a compressor with several stages is likely to have cross terms of higher orders.
An alternative approach is to implement 1D compressor models in the engine performance cycle. However, the handling of choking conditions has precluded using this type of modeling. This paper provides an innovative approach for choking handling for multi row compressors without hampering the convergence of the engine performance cycle.
A mathematical set-up was developed; it allows dealing with choked rows while keeping the number of unknown variables to a minimum.
This mathematical scheme was tested with a research two stage compressor. Although more than one row could be choked at the same time, there was no convergence issues, and the 1D model was able to replicate the overall map.
On the Flow Physics During the Transition of a Variable Pitch Fan From Nominal Operation to Reverse Thrust Mode
Authors: Vitlaris Dimitrios , Rajendran David John , Pachidis Vassilios , Tunstall Richard , Whurr John 
Published: September 2023

Abstract
The flow field during the transition of a VPF from nominal operation to reverse thrust mode at typical ‘Approach Idle’ engine power setting and aircraft touchdown speed of 140 knots is described in this work. An integrated airframe-engine-VPF research model that features a future 40000lbf geared high bypass ratio engine installed on a twin-engine airframe in landing configuration is used to explore the flow field in a fully transient URANS simulation with imposed wall motion. A novel methodology that implements an adaptation of a mesh displacement equation to mimic the fan blade aerofoil rotation is developed. The implementation of this method with gradual, small step deformation along with an automated mesh update routine enables a high quality, near ‘real-time’ simulation of the complete transition.
The flow field during transition is characterised by the evolution from full typical forward flow through the engine to the development of massive recirculation regions at the feather pitch setting and finally to development of a reverse flow from the bypass nozzle to the fan passages. In the paper, the transient development of the various flow features through different stations of the engine flow path apropos the fan blade aerofoil rotation to reverse thrust mode are discussed in detail in the paper. Also, the temporal development of the mass flow ingested through the engine, airframe decelerating force and distorted flow at the core engine inlet are described. A hitherto unresolved fan power peaking during the middle of the transition and higher power requirement at reverse thrust mode is captured. The effect of fan rotational speed in terms of engine power setting and the aircraft touch down velocity on the transition flow physics is explored. A comparison of this fully transient approach with discrete steady state runs for different stagger angle settings is presented. The flow physics during transition to reverse thrust mode as described in this study is critical in understanding the feasibility of using VPF for reverse thrust in future aircraft. The new capability to study the transition in a fully transient simulation can be used as a design development aid to define design and control characteristics of the reverse thrust VPF.