bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Cost Optimization of Hydrogen-Air Combustion for NOx Prediction
Authors: Buisson Quentin , Leparoux Julien , Puggelli Stefano , Leroy Maxime , Mirat Clément 
Published: August 2024

Abstract
The switch from fossil fuels to hydrogen represents a break-through path towards the decarbonization of the aeronautical sector. However, compared to hydrocarbons, hydrogen has very different characteristics. This challenges the current state of the art of numerical methods that must be re-evaluated in terms of accuracy and computational cost for aeronautical applications. Large Eddy Simulations (LES) applied to hydrogen combustion can easily become too costly with respect to the industrial constraints.
In this work, a study to reduce the time-to-solution in LES is performed. The selected configuration is a two-staged swirled combustor. The reference LES setup includes a detailed chemical description by using a 21-species, 64-reactions chemical scheme (including NOx) and the thickened flame model to handle turbulent combustion. From this, different numerical combinations are investigated for each phase of the simulation (from non-reactive flow to flame stabilisation) as well in terms of chemistry description to minimise the LES return time. Ultimately, the switch towards a lighter 9-species, 12-reactions chemical scheme and the inclusion of NOx with a tabulated formalism is retained as optimized setup. This choice determines all in all a 50% reduction in terms of computational cost with respect to the reference setup, keeping the experimental flame topology fairly well retrieved. The general trend for NOx emissions at the burner outlet is as well correctly captured, even if the chosen methodologies differ on the absolute values.
Surrey Hydrogen Aircraft Performance Evaluator (SHAPE): Viability of Liquid Hydrogen-Fueled Wing/Fuselage/Gas-Turbine Aircraft
Authors: Tiwari Saurav , Pekris Michael J. , Doherty John 
Published: August 2024

Abstract
Liquid hydrogen has become a key focus in aviation as a potential energy vector for advancing towards 2050 Net Zero targets. This paper presents a new tool SHAPE (Surrey Hydrogen Aircraft Performance Evaluator) for system-level assessment of an adapted wing and tube aircraft configuration for liquid hydrogen fuel and the associated enabling technologies. SHAPE, a 0D steady-state solver, uses adapted empirical correlations with hydrogen-related technological assumptions and future projections for system sizing, mass, and performance predictions. The SHAPE predictions of conventional aircraft performance were validated against open-source information of A320neo and B737-800 aircraft along with results of widely used aircraft design tools SUAVE and TASOPT over a short haul mission. SHAPE’s results suggest that a liquid hydrogen-fueled aircraft with a gas turbine propulsion system could be demonstrated for an A320neo equivalent mission with competitive overall mass (+1%) and performance attributes (+2% energy consumption) compared to a kerosene aircraft. Certification for 2035 timescales would be challenging and requires considerable industry effort, collaboration, and early regulatory body engagement. Considering on-board technology uncertainties associated with hydrogen, a sensitivity analysis shows that the energy consumption prediction of the hydrogen aircraft could vary between +7.1% to −2.2% relative to equivalent kerosene aircraft, and overall aircraft mass could vary between +5.5% to −2.1% (with a 95% level of confidence). Fuel cell powered aircraft, even with optimistic assumptions, appear to be unfeasible for short/medium haul missions. The preliminary observations emphasize the opportunity for technology demonstration with tube-and-wing aircraft adapted for hydrogen combustion, given their higher weight and lower energy efficiency compared to kerosene aircraft. The findings of a large number of previous studies are benchmarked against the outputs of this work to provide further context and insight.
Ball Bearing Dynamic Stiffness Prediction Considering an Uncertain Position of Rolling Elements
Authors: Kochurov Roman , Martynenko Volodymyr , Moroz Leonid , Govorushchenko Yuriy 
Published: August 2024

Abstract
This paper considers the challenge of calculating accurate ball bearing stiffness, which is attributed to the uncertainty in the rolling element positions; and it solves that issue based on the simultaneous consideration of these positions and the physical effects of the rotating components. The novelty of the paper consists of the suggested methodology to resolve the uncertainty of the rolling element circumferential position when calculating bearing stiffness. The problem is solved through various formulations of dry and lubricated contact and validated based on the consideration of the finite-element model. The algorithms presented in the paper allow for the calculation of the resulting stiffness based on the stiffness values evaluated through different ball bearing positions. The approach presented in the paper is validated based on the experimental data. For this purpose, the model of the rotor in ball bearings is built, along with further calculation of the rotor dynamics. The comparison of the critical speeds calculated for the rotor in bearings, which have stiffness evaluated by the proposed approach with the measurements for the real machine, indicates a high accuracy of the suggested method in comparison with the methods that consider the single position of the rolling element when estimating their stiffness. In the paper, further recommendations for the use of the presented method are given, which will be useful for engineers in the field of turbomachinery dynamics.
Modeling of Frictional Inter-Bristle Contact in Brush Seals With Shaft Radial Movements
Authors: Phan Harry M. , Pekris Michael J. , Chew John W. , Greenslade Thomas J. 
Published: August 2024

Abstract
Brush seals are utilized in turbines to minimize leakage flows and enhance thermal efficiency. Their widespread use faces challenges like pressure-stiffening and hysteresis, leading to unpredictable performance. This work introduces an advanced numerical model to simulate inter-bristle frictional contact, shaft and backing ring interaction, and three-dimensional bristle bending. The model is adopted to investigate multi-bristle brush seal’s behavior under shaft radial movements and pressure loading. Backing ring friction emerges as a vital factor in hysteresis modeling, lessening the impact of shaft friction. When the shaft retracts, modeling the bristle tip clearance becomes important. The clearance greatly increases leakage flow rate and changes bristles’ aerodynamic loading distribution. With clearance, the normal force on upstream bristles rises markedly, opposing bristle hang-up, while the axial force decreases in downstream bristles, alleviating the bristle pack compression. Considering these factors, an improved model for pressurized seals in the shaft retraction phase is developed and compared to experimental data in the literature. Frictional inter-bristle contact significantly modifies the distribution of local tip force through the pack. These effects would influence localized wear and heat generation across the brush seal pack, shedding light on the uneven wear patterns often observed in experiments. The present high-fidelity model can capture these complex interactions, offering a means to deepen our understanding of the physical mechanisms underpinning novel brush seal designs.
Numerical Study on the Propagation Characteristics of Circumferential Temperature Distortion in a Combined Compressor
Authors: Wang Zhenfei , Wang Zhiheng , Li Tongxi , Xi Guang 
Published: August 2024

Abstract
It is normal practice to design aero compressors under the assumption of uniform inlet flow. However, the distortion of temperature or/and other parameters at compressor inlet frequently occurs during actual operation due to surrounding environment. The aerodynamic stability and efficiency of compressor are often decreased by the inlet distortion. The researches on total temperature distortion are currently primarily concerned with the impact on overall performance, and the related flow mechanisms are not fully understood yet. Therefore, in this paper, the unsteady three-dimensional numerical simulations are conducted to study the influence of total temperature distortion on the compressor flow and its propagation characteristics in an axial-centrifugal combined compressor. The inlet distortions considered in the paper are the total-temperature distortions covering a 60-deg sector (60deg distortion). The results indicate that the circumferential distortion lowers the efficiency and pressure ratio of compressor. By analyzing the variation trend of the distortion index along the flow direction and the influence of distortion on the flow structure of the end-wall zone, the propagation law of total temperature distortion in the axial centrifugal combination compressor was explained. The results show that the total temperature distortion index decreases along the flow direction, and shows the characteristics of decreasing in the rotor blade row and changing slightly in the stator blade row. The distortion causes the rolling position of the axial rotor leakage vortex to migrate downstream, and the direction of the leakage vortex trajectory changes. In addition, the distortion leads to an increase in turbulence kinetic energy and loss in the blade tip region of the centrifugal impeller.
Emission and Operational Characteristics Analysis of Axially Staged Combustors Based on Overall Parameters
Authors: Liang Enguang , Yu Zhijian , Zhang Chenjie , Zhu Min 
Published: August 2024

Abstract
Due to increasing requirements for gas turbine efficiency, it is necessary to effectively control thermal NOx emissions while elevating the combustor outlet temperature, in order to meet increasingly stringent environmental regulations. At the same time, the prospective demand for carbon reduction and capture requires gas turbines to improve fuel flexibility, capable of burning syngas or fuels enriched by higher proportions of hydrogen. Gas turbine manufacturers have been testing the axially staged combustion technology on H-class gas turbines, which helps to reduce NO emissions, improve fuel flexibility, and reduce the risk of combustion instability. Considering that the majority of previous literature separately studies the impact of individual parameters on emissions or stability, this paper will discuss the determination and optimization of axially staged combustors overall design parameters, namely the air, fuel, and residence time distribution ratios between the first and second stage burners, under the condition of specified thermal power and emission levels. The main work includes: 1) developing a mathematical model for predicting pollutants in axially staged combustors, while studying the impact of staged parameters on NO, and analyzing the parameter range for low emission operation of axially staged combustors; 2) verifying the model by conducting chemical reaction network calculations using detailed chemical reaction mechanisms; 3) by using NO emissions as the objective function to optimize the staged parameters, two ranges of parameters that meet the emission requirements were obtained, respectively characterizing the lean and rich burn conditions of the first staged burner; 4) discussing the impact of the hydro-carbon fuel components on the operating range. The results will provide guidance for expanding the operating range, improving fuel flexibility, and reducing emissions of axially staged combustors.
Centrifugal Compressor Casing Treatment Design for a Turbocharged Hydrogen Combustion Engine
Authors: Gibson Lee , Leonard Thomas , Iosifidis Georgios , Di Modica Dario-Vincenzo , Ratz Johannes , Ueno Takahiro 
Published: August 2024

Abstract
Rapid decarbonisation of energy-intensive industries such as heavy-duty transport and stationary power generation is essential to meet the emissions targets set by legislative authorities around the globe. Emission-free battery technologies are promising but they do not yet achieve the energy density needed for larger machines and the suitability of fuel cells to operate in harsh environments remains uncertain. Hence, Hydrogen internal combustion engines (ICEs) emerge as an attractive solution. Existing Diesel and Gasoline ICEs can be readily adapted to Port Fuel Injection (PFI) Hydrogen ICEs using lean-burn combustion or Exhaust Gas Recirculation (EGR) to achieve high efficiency and low emissions. Such engine configurations typically demand turbocharger compressors with high pressure ratio and efficiency. However, compressor map width tends to decrease with increasing pressure ratio and this can sometimes limit the engine operating range. The literature review identified the ported shroud (or bleed slot) casing treatment as an effective add-on technology to improve compressor map width, particularly at high pressure ratios. This paper details the design of a ported shroud casing treatment for a highly loaded centrifugal compressor equipped with a vaneless diffuser. A parametric study was conducted using a validated Computational Fluid Dynamics (CFD) model to determine the sensitivity of compressor pressure ratio, efficiency, and recirculation ratio to the downstream slit position, width and meridional angle. The angle of the struts necessary for structural support of the ported shroud inside the compressor housing was also considered. The findings of the parametric study were subsequently used to inform a design optimisation with the goal of maximising the potential stability enhancement offered by a ported shroud casing treatment.
Unsteady Investigation of Side Loading Effect on Single-Stage Centrifugal Compressors
Authors: Bicchi Marco , Lottini Fabrizio , Biliotti Davide , Ortiz Neri Massimiliano , Querini Lorenzo , Bianchini Cosimo 
Published: August 2024

Abstract
Single-stage centrifugal compressors have historically found usage in several industrial and civil applications thanks to their high efficiency, robustness, and wide operating range. However, despite the simplicity in the architecture, the overhung configuration represents a challenging arrangement for the design of these types of machines. In particular, the presence of a discharge volute with variable cross-sectional area around circumference further exacerbates such task due to its intrinsic asymmetric shape. Indeed, focusing on the volute-impeller interaction, static pressure distortions could introduce non-negligible forces that act on journal bearings. Against this backdrop, a good prediction of static pressure fields is pivotal. In this perspective, a methodological framework leveraging unsteady and steady CFD analyses is proposed and validated using on-site measurements of a real working machine by exploiting the built-in instrumentation of the active magnetic bearing system. The main goal of the present work is to provide and validate a numerical methodology useful for the prediction of the magnitude and the angular position of the induced side force on single-stage centrifugal compressors. Specifically, the theoretical contribution of the research is to investigate the limits of steady computations against unsteady modelling for the evaluation of volute-impeller interactions in single-stage centrifugal compressors with vaneless diffuser. On a practical level, a criticality analysis on the importance of several modelling aspects on the calculations of side load prediction is provided. The proposed approach is verified on a centrifugal compressor stage for expander-compressor applications. Results show good agreement between CFD results and field data. The present research lays the foundations for future studies aiming to predict volute-impeller interaction in single-stage centrifugal compressors.
Design-Point Techno-Economics of Brayton Cycle PTES for Combined Heat and Power
Authors: Neises Ty , McTigue Joshua 
Published: August 2024

Abstract
Pumped thermal energy storage (PTES) systems are grid batteries that use heat pumps to create both hot and cold thermal energy stores when there is excess electricity and then use a power cycle to convert the thermal energy into electricity when there is demand for electricity. In normal operation, Joule-Brayton PTES discharges low-grade heat at temperatures useful for thermal energy consumers like district and industrial heating. Furthermore, PTES designs, like conventional combined heat and power (CHP) technology, can be modified to sacrifice some round-trip efficiency RTE to increase the temperature of heat rejection.
This paper uses design-point performance and cost models that provide a detailed understanding of the efficiency and cost trade-offs of rejecting heat at various temperatures in ideal-gas Brayton PTES configurations. First, we keep the heat rejection in its nominal location in the PTES system: in the discharge cycle after the low-pressure exit of the recuperator before the cold-storage heat exchanger. Next, we move the heat rejection to the discharge turbine exit. We define design-point metrics that isolate both the cost and performance penalty associated with the hotter heat rejection and attribute it exclusively to the heat economic metrics. Finally, we estimate the performance of electric heater technology to generate heat at equivalent temperatures. We find that the levelized cost of heat, including the cost of thermal energy storage (TES) buffering the PTES and heat off-taker, compares favorable versus electric technologies and is less than the cost of natural gas for low temperature scenarios and competitive with the cost of natural gas in some regions of the contiguous United States in high temperature scenarios.
Multistage Turbomachinery Optimization for High Temperature Heat Pumps With the Reverse Rankine Cycle
Authors: Schaffrath Robert , Stathopoulos Panagiotis , Schmitz Andreas , Nicke Eberhard 
Published: August 2024

Abstract
The electrification of process heat generation will be a key to achieving carbon neutrality in the coming decades. One of the most promising approaches is to replace conventional heat supply systems with high-temperature heat pumps (HTHPs). A promising heat pump concept is based on the reverse Rankine cycle that uses water as its working fluid. By using turbomachinery for the compression process in this cycle, the performance of the HTHP can be increased compared to volumetric displacement systems, like screw or piston compressors. Although the design of the compressor geometry can be done sequentially in relation to the HTHP cycle design, better results can be obtained by an approach that integrates turbomachinery and the thermodynamic cycle design. Against this background, an automated optimisation method for a reverse Rankine HTHP with two radial turbocompressors in series is presented. In contrast to the current state of the art, the presented novel optimization approach uses 3D CFD data to calculate compressor performance. Furthermore, the integration of low fidelity compressor specific reduced order models are used to accelerate the gradient-free optimization process by a CO-Kriging surrogate model. The advantages of the novel approach are justified by comparing the numerical effort and the final values of the optimization objectives.
A Study of Loss Model Parameter Sensitivity in Compressor Unsteady Flow Simulations
Authors: Jing Zhenhao , Neumeier Yedidia , Prasad J. V. R. , James Darrell K. 
Published: August 2024

Abstract
This paper presents results from a comprehensive sensitivity analysis focused on loss models used in a recently developed compressor unsteady mean line flow model for a transonic axial-centrifugal compressor. The mean line flow model treats flow through rotors and stators in their respective reference frames (rotating or stationary), and the compressor performance is determined by the kinetic energy addition and various physics-based loss models in relative frames. In this paper, we describe the modeling approach of the compressor flow model, as well as the loss models that are used to obtain a relatively good match against test data. Sensitivity studies of selected loss model parameters are presented to show the effect of individual loss model parameters on the overall compressor characteristics in the entire speed range. The effects of losses on unsteady flow transients are assessed by comparing the transient responses when a step reduction of throttle area is applied. The comparisons show that the change in loss magnitude has weak effects on transient response if the change of loss does not significantly change the system stability.
Investigating the Performance of Multi Element Wind Lens
Authors: Elsafty Kareem , Elbaz Ahmed 
Published: August 2024

Abstract
A major limitation for the full utilization of wind turbines as the main power source is the large variation of wind availability from one area to another, especially at locations with low average wind speeds. Harnessing energy from the wind using diffuser augmented wind turbines or wind concentrators (commonly called wind lens) is one of the trending topics in the field of wind energy where low wind speed is encountered. The main objective of the present work is to investigate the performance of a new type of wind concentrator composed of multi element airfoil sections. Comparison of the new design is made with common design of wind lens to find the optimum configuration that outperforms a conventional wind lens. The proposed design also allows for extra air flow to pass into the lens between the two elements. This allows the application of dual rotor wind turbine with the wind lens where a second rotor is placed at the exit section of the lens. The performance of the new design was examined using CFD technique via the commercial software ANSYS FLUENT. The study investigated the tilt angle of the front piece, the tilt angle of the back piece as well as the gap between the two sections on the mass flow rate through the lens throat and exit sections. The results of the mass flow rate and wind velocities as well as the drag coefficient are compared with conventional wind lens results. The results show that it is possible to increase the mass flow rate through the throat section by 48.3% in comparison with freestream mass flow rate. The results indicated the possibility of enhancing the mass flow rate through the exit section by 14% higher than that at lens throat. The drag coefficient of the multi element wind lens is 17% lower than that of the conventional wind lens with brim.