bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design Methodology and Concept Demonstration of Preassembled Additively Manufactured Turbomachinery Systems: Case Study of Turbocharger Based Medical Ventilators
Authors: Çelik Acar , Linsky David , Miezner Ron , Kleiman Alex , Leizeronok Boris , Palman Michael , Acarer Sercan , Cukurel Beni 
Published: October 2022

Abstract
The present research focuses on analyzing the feasibility of manufacturing complex turbomachinery geometries in a pre-assembled manner through an uninterrupted additive manufacturing process, absent of internal support structures or post-processing. In the context of the present COVID-19 pandemic, the concept is illustrated by a 3D-printable turbine-driven blower-type medical ventilator, which solely relies on availability of high-pressure oxygen supply and a conventional plastic-printer. Forming a fully pre-assembled turbomachine in its final form, the architecture consists of two concentric parts, a static casing with an embedded hydrostatic bearing surrounding a rotating monolithic shell structure that includes a radial turbine mechanically driving a centrifugal blower, which in turn supplies the oxygen enriched air to the lungs of the patient. Although the component level turbomachinery design of the described architecture relies on well-established guidelines and computational fluid dynamics methods, this approach has the capability to shift the focus of additive manufacturing methods to design for preassembled turbomachinery systems. Upon finalizing the topology, the geometry is manufactured from PETG plastic using a simple tabletop extrusion-based machine and its performance is evaluated in a test facility. The findings of the experimental campaign are reported in terms of flow and loading coefficients and are compared with simulation results. A good agreement is observed between the two data sets, thereby fully corroborating the applied design approach and the viability of additively manufactured pre-assembled turbomachines. Eliminating long and costly processes due to presence of numerous parts, different manufacturing methods, logistics of various subcontractors and complex assembly procedures, the proposed concept has the potential to reduce the cost of a turbomachine to capital equipment depreciation and raw material.
Design of a 1MW Direct-Fired Oxy Combustor for sCO2 Power Cycles
Authors: White Steve , Berry Grey , Connolly Brian 
Published: October 2022

Abstract
Direct-fired super-critical carbon dioxide (sCO2) power cycles are a potential method for efficiently capturing nearly all of the CO2 emissions from burning fossil fuels. Direct-fired sCO2 cycles require a very high degree of recuperation, which in turn means that the inlet temperature to the combustor is significantly higher than would typically be seen in a similar gas turbine combustor. Previous efforts have shown that combustor inlet temperatures of around 700°C at 200 bar are to be expected for a cycle with around 1200°C combustor exit temperatures.
The project team led by Southwest Research Institute is in the process of building and commissioning a 1MW scale direct-fired sCO2 oxy combustor. The test rig at SwRI uses laser ignition and advanced optical access to monitor combustion and characterize behavior. This paper will detail some of the challenges associated with the design and fabrication of the combustor and sCO2 power loop. These obstacles include thermal management, water generation, and constituent monitoring. The first ever unsteady simulations of this type of combustor were conducted as part of the design process. A presentation of the test rig layout, design considerations, and integration challenges will be covered.
Optimization Under Uncertainties of a Biogas-Fueled SOFC-GT Hybrid System
Authors: Finocchi Paolo , Zaccaria Valentina , Ferrari Mario L. , Tucker David 
Published: October 2022

Abstract
SOFC-GT hybrid systems can be a good solution for small-medium size applications of distributed generation thanks to their high efficiency and their high fuel flexibility. Fueling these systems with raw biogas coming from biomass gasification makes them also completely renewable, but it introduces a high variability of performance due to the syngas composition fluctuations. For this reason, this work pursues the aim of realizing a robust system optimization, necessary to obtain the best design and ensure high efficiency combined with low variability. To do this, a co-flow, planar, anode supported SOFC Simulink model was used. Moreover, a related surrogate model was created to decrease the computational time and increase exponentially the number of simulations. To calculate the robust optimum design, the Monte Carlo method was used, simulating the syngas composition distribution with 2000 points and to the operating envelope with 5000 input combinations. Mean value and standard deviation in system efficiency were used to select a Pareto front. The robust points turned out to be those with low electric load, small-medium pressure, and high temperature, while maximum efficiency points were characterized by higher pressure levels. The smaller standard deviation at lower pressure was shown to be linked to the bottoming cycle operation and in particular to the gas turbine off-design condition. This difference between the two design conditions (robust optimum and efficiency optimum) confirmed the importance of this optimization process and the influence of fuel composition on system performance.
Restitution of Impacting Projectiles in Ceramic Matrix Composites (CMCs) Subject to Foreign Object Damage
Authors: Faucett David C. , Mattison Jacob , Choi Sung 
Published: October 2022

Abstract
Accurate assessments of rebound velocity of a projectile in impact events for ceramic matrix composites (CMCs) are important since the rebound velocity affects the degree of resultant impact damage in both CMC targets and projectiles. A series of in-depth characterizations of coefficients of restitution (COR), which is defined as rebound velocity divided by impact velocity of a projectile, was made using various types of gas-turbine grade ceramic matrix composites (CMCs) in conjunction with dynamic imaging and data-acquisition systems. Both the impact aspects and the coefficients of restitution were characterized as a function of impact velocities ranging from 150 m/s to Mach 1 and were analyzed with respect to materials’ key properties. An important experimental observation was that regardless of types of CMCs employed, the corresponding CORs at an impact velocity of 350 m/s (i.e., Mach 1) yielded consistently the same value close to 0.1–0.2. The temperature effect in COR was found to be minor to 1100°C as assessed with the specialty SiC/SiCs, also independent of environmental barrier coatings. The coefficients of restitution were also determined in other materials systems such as advanced monolithic ceramics and some metallic materials in an attempt to construct an overall COR map in response to related foreign object damage (FOD) events.
Flametube Evaluation of a Lean-Lean Combustor Concept Developed for Supersonic Cruise Aircraft
Authors: Tacina Kathleen M. , Podboy Derek P. , Guzman Francisco 
Published: October 2022

Abstract
Gaseous emissions were measured in single-cup flametube tests of an advanced low-NOx combustor concept at simulated supersonic cruise conditions. The combustor concept is a low technology readiness level (TRL), lean front-end design developed under the NASA Fundamental Aeronautics/Supersonics project to minimize NOx emissions at supersonic cruise. The flametube conditions matched or approached combustor conditions at supersonic cruise, with combustor inlet temperatures up to 920 K, inlet pressures up to 19 bar, and combusted gas temperatures up to 2,120 K. Whether these conditions met or just approached supersonic cruise conditions depended on the type of engine the combustor would be installed in. Two types of engines were considered here: a “derivative” engine based on a current technology and an “advanced” engine with a higher operating pressure ratio and higher temperature limits. For the “derivative” engine, the combustor is expected to be at least close to meeting the NASA NOx emissions goal of 10 g-NOx/kg-fuel at supersonic cruise. However, with the higher combustor inlet and flame temperatures of the advanced engine, NOx emissions are expected to be well above the goal.
Feasibility of Achieving 62% Combined Cycle Efficiency With a 200 MW Gas Turbine
Authors: Gulen S. Can (John) , Zachary Justin 
Published: October 2022

Abstract
The current thermal performance of advanced gas turbines (J class) leads to combined cycle efficiencies exceeding 62%. Such results were achieved by making the gas turbines bigger, i.e., above 350 MW (larger air flow), and by increasing the firing temperature. However, a very significant part of the power generation market, particularly in support of solar or wind renewable power production, requires smaller gas turbines, producing in a 1 × 1 × 1 combined cycle configuration nominally rated at 300 MW. The paper investigates options to implement improvements realized by current J class gas turbines to a smaller gas turbine producing around 200 MW. It describes the challenges for such an endeavor. Taking each of the gas turbine components from the intake, compressor, combustor, turbine and exhaust, the paper examines the viability of technical solutions implemented in larger gas turbines (increased air flow, larger physical dimensions, more fuel flow etc.) to a lesser output gas turbine. It also discusses the impact of a smaller gas turbine on the bottoming cycle major equipment (HRSG, steam turbine and balance of plant). Finally, the study attempts to predict the feasibility of combined cycle efficiencies exceeding 61% combined cycles based on a gas turbine with a 200 MW output.
The Influence of Shrouded Stator Cavity Boundary Conditions on Performance of a 1.5-Stage Low-Speed Research Compressor
Authors: Shao Runzhu , Zhu Mingmin , Teng Jinfang , Qiang Xiaoqing 
Published: October 2022

Abstract
In axial compressor, the leakage flow from labyrinth cavity has a non-negligible influence on the aerodynamic performance and flow fields of shrouded stators due to its interaction with the main stream. A number of numerical researches have been carried out to predict and understand the cavity flow. However, details about the boundary conditions between cavity and mainstream are scarce in opening literature. Comparisons between numerical and experimental results are seldom reported to verify the rationality of the connecting method. Therefore, a four-stage low-speed research compressor (LSRC) with shrouded stators in Shanghai Jiao Tong University was investigated numerically in this paper, aiming at studying the influence of different cavity boundary conditions. A steady numerical research on the front 1.5-stage (IGV-rotor-stator) of LSRC was performed using NUMECA with four connecting methods for the interface between the cavity and mainstream. The investigation reveals that different boundary conditions make great impact on the aerodynamic performance and flow fields of the compressor. Validated by the experimental data, when using the full non-matching connections between cavity and mainstream while cavity domain rotating at the nominal speed, the steady three-dimensional RANS simulation of the 1.5-stage compressor can well predict the distributions of total pressure loss and flow angle near the hub at the stator outlet. The flow mechanisms of different connecting methods are elucidated by investigating the detailed flow fields inside the cavity and near the stator hub. The full-non matching cases with different rotational speeds of cavity domain from 0 to 900 RPM are also compared to demonstrate the influence of rotational speeds on performance and flow fields.
Effect of Surface Corrugations on Laminar and Transitional Flows
Authors: Jain Ishita , Sarkar S. 
Published: October 2022

Abstract
The effect of surface roughness on spatially developing transitional flow field is discussed in the present study by carrying out highly resolved Large Eddy Simulations (LES). The surface modification considered here is the two-dimensional rectangular ribs embedded in the flat plate, resulting into the formation of transverse spanwise cavities with pitch as λ = 3k, where k is the roughness height. The results are simulated for the three imposed inlet conditions, while the Reynolds number based on momentum thickness is 150, 300, and 500. The instantaneous and time-averaged flow features have been resolved. The mean flow characteristics revealed the appearance of the primary vortex within the cavity, which led the primary flow to slip over the cavities, attributing to reduction in the drag. The distributions of skin friction coefficient (Cf) are compared with the flat plate correlations, which illustrate significant percentage reduction within the cavities in the transitional regime. Further, the existence of elongated streaks with significant influence on laminar-to-turbulent transition and their interaction with the roughness is explained.
Performance and Economic Assessment of Mechanically Integrated Parallel Hybrid Aircraft
Authors: Carpentier Thibault , Zhang Jinning , van Heerden Albert S. J. , Roumeliotis Ioannis 
Published: October 2022

Abstract
In this study, a selection of environmental and economic considerations of mechanically integrated parallel hybrid (MIPH) electric propulsion systems for single-aisle civil transport aircraft are assessed. The environmental assessment focuses on the carbon dioxide and nitrogen oxide emissions with different power management strategies and levels of battery technology. In the economic study, the potential subsidies and tax incentives required to make these aircraft financially viable are determined. To capture the performance results, models of the propulsion systems and airframe were constructed using the Siemens Simcenter Amesim systems modelling software. The operating cost was then computed using adapted direct operating cost estimation methods. Battery replacement was incorporated by using a battery cycle aging model. The results showed that using a battery energy density of 300 Wh/kg will not provide any meaningful benefits. For 600 Wh/kg, fuel savings of up to 3% for missions below 650 nm could be obtained for a PMS where the electrical powertrain operates during takeoff, climb, and cruise. However, the NOx emissions were lowest for the takeoff and climb only PMS, implying a trade-off when selecting a PMS. Based on the cost results, it is determined that taxation on carbon emissions would have to increase at least 50-fold from its current levels for the most optimistic scenarios. Alternatively, considerable subsidies, representing large percentages of the purchase price of the aircraft, will be needed.
Model Setup for the Investigation of Flow Phenomena in a 1.5-Stage Gas Turbine Regarding Hot Gas Ingestion
Authors: Pehle Lukas , Schwertner Sven , Wirsum Manfred 
Published: October 2022

Abstract
This paper presents different modeling approaches on rim seal flow in a 1.5-stage test turbine resulting in the analysis of numerical data in comparison to existing test data. The analysis focuses on a very simple axial sealing gap and a reference operation point which shows significant hot gas ingestion in the experiments. The presented model will be used to gather more information on flow phenomena and their effect on the ingestion and hence contributes to a deeper understanding. In combination with broader research this understanding will help manufacturers to reduce their secondary air mass flow rate and increase gas turbine’s efficiency.
Experiments on the hot gas ingestion phenomenon have already been carried out at many international test facilities. As part of a recommissioning of a test rig for investigating hot gas ingestion into the wheel side cavities of axial-flow gas turbines at the RWTH Aachen University, this publication presents the numerical model set up in parallel. In particular, the aim is to investigate the sensitivity of the modeled flow field in the wheel side cavity for changes in the modeling and boundary conditions. In addition to the investigation of the sensitivity, the results are compared with existing measurements in order to be able to classify and evaluate the sensitivities in a specific manner.
The investigation starts with a mesh study followed by the analysis of different turbulence models including different inlet turbulence intensities. After analyzing different time steps in transient and steady state simulations, calculations are shown concerning different operation points. For all chosen combinations of settings and boundary conditions the main flow is modeled reasonably well compared to experimental data. Also the operation point dependency of the pressure field is modeled well with simple approaches.
For low purge air mass flow rates the flow field in the wheel side chamber, consisting of pressure and sealing gas concentration, is only represented with strong deviations in the one-segment model. These deviations are due to large structures forming in the cavity, which can not be reproduced using one or two pitches of the turbine. Above a certain dimensionless purge air mass flow rate, a transition in the flow field can be observed analyzing the experimental data. Above this flow rate the large structures break down and the sealing effectiveness increases. At these operation points the selected numerical model shows good agreement with experimental data regarding pressure and hot gas concentration. To improve predictions at low purge air flow rate multiple segment models will be used in the future.
Direct Numerical Simulations of Aerodynamic Performance of Wind Turbine Airfoil by Considering Flap-Wise Blade Oscillations
Authors: Erfanian Nakhchi Toosi Mahdi , Rahmati Mohammad 
Published: October 2022

Abstract
Aeroelasticity of modern wind turbines is a critical issue which can significantly affect the structural integrity and lifetime of the wind turbine blades. However, previous aeroelastic or aerodynamic studies were mostly concentrated on low-fidelity numerical methods, and the details of flow separation and vortex generation over wind turbine airfoils cannot be detected with these methods. In this study, a high-fidelity direct numerical model is used to investigate the details of flow separations and laminar separation bubbles (LSB) over a NACA-0012 wind turbine airfoil under oscillation. The simulations are conducted at Reynolds number of Re = 1.3 × 105 and the blade has harmonic pitch-wise oscillations at Mach number of Ma∞ = 0.4. Strong fluctuations are observed in the wake region of the vibrating wind turbine blade. The results show that the blade vibrations have a significant influence on vortex generation and separation point over wind turbine blades. details of flow structure over wind turbine blades compared to previously proposed models.
Fan Stability Enhancement With Partial Casing Treatments
Authors: Oldfield Matthew K. , Castillo Pardo Alejandro , Hall Cesare A. 
Published: October 2022

Abstract
Casing treatments are used to extend the stability margin of fans or compressors. These typically have an axisymmetric arrangement, but for a fan exposed to non-axisymmetric distortion, a casing treatment applied to a fraction of the annulus is of interest to target a particular distortion feature. In this paper, a partial casing treatment has been designed with axial-skewed slots and an experimental investigation has been carried out to determine the effects of the treatment extent and position.
Three inlet conditions were tested for each extent of casing treatment; clean, radial tip-low distortion and half-annulus tip-low distortion. For axisymmetric inlet conditions, the stall margin and efficiency penalty increased approximately linearly with casing treatment extent. However, for half-annulus tip-low distortion, there was a strong dependence between the position of the casing treatment relative to the distorted sector and the stall margin improvement. If the casing treatment is positioned where the rotor enters the distorted sector, unsteady disturbances in the rotor tip flow are minimized. However, if the rotor meets the casing treatment later in the distorted sector, the disturbances are able to grow, leading to earlier stall inception. Overall, this shows that partial casing treatments can target a distorted flow to give a disproportionately positive impact compared a full annulus casing treatment. For example, it was found that a 72° casing treatment extent could be positioned to achieve over 50% of the full annulus casing treatment stall margin improvement with only 20% of the efficiency penalty.
Low Wind Speed Characteristics of an Optimized Diffuser Augmented Wind Turbine
Authors: Abdelrahman Hazem H. , Elbaz Ahmed M. R. , Elkholy Ahmed M. 
Published: October 2022

Abstract
Towards a final aim of enhancing the feasibility of low-speed sites for wind energy generation, the current study introduces the diffuser augmentation as a method of enhancing the performance of wind turbines designed for poor wind conditions. The study uses a methodology that combines the MOGAII Genetic Algorithm (GA) and Computational Fluid Dynamics (CFD) to generate a novel optimized diffuser profile out of nearly 200 geometric shapes. A case for each of the bare turbine and the diffuser-augmented turbine were modeled using 3-dimensional Reynolds Averaged Navier Stokes equations (RANS) using k-ω SST model and FLUENT solver. The performance comparison indicated an overall average rise of 28.83% in power coefficient in favor of the diffuser-augmented case. The most significant performance rise of 47.19% was found at the low-speed region corresponding to Tip Speed Ratios between 8 and 12. Through investigating the starting torque at extremely low speeds above 1 m/s, it was evaluated that the starting torque increases significantly with an average rise of 60.64% in favor of the diffuser-augmented case, the enhanced starting torque widened the operational range of the wind turbine in the low wind speed region, and reduced the lowest required speed to induce a positive moment coefficient. This significant rise in performance particularly for low wind speeds which are dominantly more frequent in the annual wind conditions, combined with the enhanced starting capabilities, resulted in an annual generated energy increase of 23.18% compared to the bare turbine.
Specific Speed Considerations for Inward Flow Radial Supercritical CO2 Turbines
Authors: Hoque Syed J. , Kumar Pramod , Gopi Pramod Chandra 
Published: October 2022

Abstract
Inward flow radial supercritical CO2 turbines require higher operating speeds than steam or gas turbines making only low specific speed designs practically realizable. A theoretical model is presented to estimate the low specific speed design regime. The model incorporates boundary conditions across the turbine and engineering limitations such as blade height, Mach number, and flow angle at the rotor inlet to predict the minimum allowable rotational speed. A CFD study is subsequently performed to review the applicability of gas turbine design principles on sCO2 turbines for low specific speed designs. The effect of specific speed and velocity ratio on turbine efficiency and flow physics is studied for power output ranging from 100 kW to 5 MW. The results show a significant deviation in the optimal specific speed, velocity ratio, and incidence angle values than traditional gas turbine designs. It is found that viscous losses dominate low specific speeds, while Coriolis effects dominate the high specific speed designs. High specific speed designs require higher negative incidence angles ∼ −50° to −55° to overcome the flow stagnation at blade pressure surface arising from the Coriolis effect. Maximum turbine efficiencies (∼ 83%) are achieved at lower specific speeds of ∼ 0.4 than gas turbines’ optimal specific speed of ∼ 0.55 to 0.65. Variations of stator, rotor, and exit kinetic energy losses with specific speeds are also presented. Finally, the results are superposed on Balje’s Ns-Ds diagram and compared with gas turbine designs.