bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Geometrical and Operational Parameters on the Leakage Flow of a Radial Labyrinth Seal for Application in Inward Flow Radial Supercritical CO2 Turbine
Authors: Lanjewar Saurabh Deorao , Fenil Arockia , Kumar Pramod , Gopi Pramod Chandra 
Published: September 2023

Abstract
Inward flow radial (IFR) turbines are preferred for small-scale power generation due to their compact and efficient design. The parasitic loss due to leakage of working fluid and disk friction at the back face of the turbine is a concern issue at smaller power scales. In the presented work, a radial labyrinth seal at the backface of the inflow radial turbine is used and analyzed to control the leakage rate. CFD studies are carried out to understand the influence of the geometric and operating parameters of the radial labyrinth seal on the leakage rate through the seal. CFD predictions reveal that for a particular pressure ratio of 1.26, the variation in axial clearance (c/s) varied from 0.025 to 0.0625, results in a ∼57.2 % increase in the leakage rate. However, the variation in height (h/s) from 0.25 to 0.75 results in a marginal 4.24 % leakage reduction. It is also observed that there exists an optimum number of teeth for a given effective seal length to improve seal performance. Furthermore, the increase in rotational speed from 10,000 rpm to 1,00,000 rpm results in a ∼67.16 % reduction in leakage rate with the temperature rise of s-CO2 through the seal by ∼62°C for the case with clearance (c/s) 0.05. The ratio Taylor to Reynolds number (Ta/Re) is found to be an essential parameter in deciding the evolution of tangential velocity. A critical value of 0.15 for the ratio is identified, beyond which the tangential velocity evolution is seen to be profound.
Gas Leak Ignition Study for 100% H2 Gas Turbine Package
Authors: Minotti Stefano , Nenciolini Andrea , Quartieri Eugenio , Rossin Stefano , Sorgonà Federico , Brekke Olaf , Holen Jens Kristian , Johannessen Bente 
Published: September 2023

Abstract
In the frame of CO2 footprint reduction towards energy transition, it is paramount developing solutions to safely convert existing gas turbine (GT) units to burn Hydrogen fuel blend potentially up to 100% H2. Equinor and Baker Hughes have collaborated to identify possible solutions for hydrogen fuel conversion of existing aeroderivative gas turbines. A feasibility study on an existing offshore package was carried out to understand the impact of the conversion of the GT and its auxiliary systems from a dual fuel (NG/Liquid Fuel) into a dual gas configuration (NG/100%H2) with water injection.
In-situ three-dimensional geometry scanning for the entire package, 3D model piping layout reconstruction and detailed CFD evaluation was needed for a better understanding of dispersion phenomena and ignition consequence due to H2 leakages. A sudden rupture of a fuel gas system tubing connection was considered the most severe failure that could occur inside the turbine enclosure during the gas turbine operation.
To shed additional light on the potential consequences of such events, several simulations of hydrogen leak dispersion were carried out using advanced computational methods like CFX and FLACS for ignition. Leakages were considered with different location, orientation and rate, and simulations results for dispersions and ignition on flammable clouds were compared including potential transition from deflagration to detonation. Potential development areas were identified to reduce the probability of such scenarios, including innovative technical solution both for installed fleet and for the next generation GT.
Impact of Engine Degradation on Contrail Formation of Long Range Aircraft Trajectories
Authors: Navaratne Rukshan , Laskaridis Panagiotis 
Published: September 2023

Abstract
Aircraft contrails are considered as one of the emissions towards climate change. Trajectory optimization is one of the methods that can be used to reduce contrail formation and a strategy that can readily be implemented. However, most of the trajectory optimization studies were performed only with clean engines, and engine degradation was not considered. This work provides a novel approach to aircraft trajectory optimization problem by including engine degradation and real aircraft trajectories within the optimization framework. Impact of engine degradation on long range optimum aircraft trajectories were assessed by quantifying the difference in fuel burn and contrail formation, when an aircraft is flying on a trajectory which has been optimized for clean engines and degraded engines. For this study, Contrail prediction model was developed with one clean and two degraded engines, integrated with aircraft performance model in an optimization framework to generate optimum aircraft trajectories. The optimum trajectories generated with degraded engines were compared with the trajectories generated with clean engines. The results have shown, for long range aircraft the persistent contrails can be reduced by 2.1% with low level degraded engines having 50°C EGT increase and 3.84% with highly degraded engines having 100°C EGT increase. However, to achieve zero persistent contrail for the same route there is a significant penalty of 2.3% and 4.2% increase of fuel with low level degraded engines and highly degraded engines. Therefore, impact of engine degradation on contrail optimum aircraft trajectories are significant and in order to reduce contrails aircraft need to fly on an optimized trajectory specifically customized for the degraded engine performance.
Assessment of Part-Load Operation Strategies of Supercritical Power Cycles Using Carbon Dioxide Mixtures in CSP Plants, Including Air-Cooled Condenser Optimisation
Authors: Rodríguez-de Arriba Pablo , Crespi Francesco , Sánchez Martínez David , García Rodríguez Lourdes 
Published: September 2023

Abstract
This manuscript, developed in the framework of SCARABEUS project, presents an assessment of the part-load performance of a transcritical Recompression cycle running on a 80%CO2-20%SO2 mixture under different load-control schemes.
The first part of the paper describes the computational platform of the integrated system, implemented in Thermoflex but with profuse use of in-house scripts, in order to accurately describe the off-design performance of key components when operating on CO2 mixtures with non-ideal gas behaviour. These off-design models make use of performance maps for turbomachinery — provided by the SCARABEUS partners — whereas the Conductance Ratio Method employed to model the counter-current heat exchangers is calibrated with in-house tools. The paper is specifically focused on the Heat Rejection Unit, for which a specific design tool accounting for accurate heat transfer between working fluid and cooling medium (air) and for auxiliary power consumption — both in off-design — has been developed by the authors.
In the second part of the paper, different operating strategies of the power cycle are considered, based on keeping one of the following three parameters constant: turbine inlet temperature, turbine outlet temperature or return temperature of molten salts. Globally, plant operation is constrained by the need to keep the temperature of cold HTF returning to the storage system as close as possible to its rated (design) value and by the need to keep turbine outlet temperature below 450°C to avoid the installation of an external cooling system in the low pressure section of this equipment. Therefore, the trade-off between these two parameters and system net efficiency are assessed in the paper. Regarding the Air-Cooled Condenser, the optimal operation strategy of this component found to be based on a combination of Single-speed and Variable Frequency Driver fans.
The results show that the operation at constant turbine inlet temperature leads to the highest net efficiency of the power block, closely followed by the control scheme based on constant return temperature of the heat transfer fluid. Nevertheless, this latter option enables a perfect control on the other two figures of merit. As a consequence, the identification of the best operation strategy must be addressed in future works by means of a thorough techno-economic assessment considering the annual yield of the plant.
Computationally Efficient Workflow for Conjugate Heat Transfer With LES for Gas Turbine Combustors
Authors: Verma Ishan , Prasad Sudhanshu , Zore Krishna , Shrivastava Sourabh 
Published: September 2023

Abstract
Typical Gas Turbine Combustor (GTC) and High-Pressure Turbine (HPT) stage generally employs 10,000 to 100,000 small passages of cooling holes. Such an arrangement protects the solid walls through impingement and effusion cooling. The former provides solid wall internal cooling, and the latter helps to reduce the metal temperature by developing a thin film around it. High-fidelity simulations are primarily utilized in the industry such that accurate prediction from numerical tools can aid advancement in the performance of such machines. In this paper, a numerical study using Ansys Fluent has been conducted with Large Eddy Simulation (LES), Conjugate Heat Transfer (CHT), and radiation to explore the relative benefits of implicit and explicit fluid-solid thermal coupling.
The simulations of LES with CHT are performed for well-documented experiments of heated nozzle exhaust passing over a film-cooled plate [12]. The accuracy of the modeling approach is assessed by comparing CHT predictions of fluid velocity and solid-plate temperatures with experiments. Acceleration techniques for LES-CHT simulations are explored in this paper with an emphasis on thermal coupling, radiation, etc. The effects of mesh sensitivity and flow solution approach are presented in detail. LES-CHT results generally match the experiments at various blowing ratios both qualitatively and quantitatively. The comparisons in the paper allow the selection of best practices for CHT modeling in GTC. A generic combustor model with effusion cooling hole arrays is used in the paper to establish the workflow for modeling LES with CHT in the industrial-type combustor. Various acceleration techniques are utilized to show an overall improvement in solution performance with the same level of accuracy.
HERMES Out of Balance Excitation System
Authors: Schwingshackl C. W. , Xu Y. , Szydlowski M. , Muscutt L. , Rix A. , Patsias S. , Ondra V. 
Published: September 2023

Abstract
Blade off events in an aero engine are one of the most critical failures, since they can lead to significant damage to the engine, and if not managed correctly, lead to uncontained failure. During development programs detailed simulations are conducted to understand the dynamic response of bladed discs and blisks in operation, to prevent blade off events. However, blade off events do still occur on rare occasions and it is critical to be able to detect and manage them. Modelling and validation of such events is very time consuming and expensive since a blade off test is a destructive test.
To provide a more effective way of investigating a sudden addition of out of balance excitation to a complex rotor system, the Holistic Engine Rotor MEasurement System (HERMES) at Imperial College London was fitted with a purpose built Out of Balance excitation system, that was embedded in the shaft of a helicopter engine. The Out of Balance excitation system design, functionality, and commissioning test results are discussed in detail in this paper to demonstrate the feasibility of the design and highlight the level of excitation that can be achieved with such a system.
Experimental Investigation of the Combined Effects of a Split-Ring Damper and an Intentional Mistuning Pattern on a Blisk Forced Response
Authors: Rodríguez-Blanco Salvador , Pagès Valdo , Guérin Nicolas , Blanc Laurent , Dumartineix Cécile , Gibert Claude , Thouverez Fabrice 
Published: September 2023

Abstract
Friction damping is one of the main mechanisms for dissipating vibration energy in turbomachinery. For assembled bladed disks, friction typically arises in the blade root — in the disk interface or, for shrouded blade configurations, in the interface between two consecutive shrouds. For integrally bladed disks, where no such interface naturally occurs, additional damping devices must be designed if energy is to be dissipated through friction. Split-ring dampers are such devices: they are located in a circumferential groove under the blisk platform, and pressed onto it by centrifugal loads. At low vibration levels and/or high rotating speeds, the split ring remains stuck to the disk, while at high levels, relative motion starts and dissipates vibrational energy.
Such devices are often designed to mainly target a given nodal diameter mode of vibration. Nevertheless, designing these dampers is a challenging task. Indeed, their behavior depends on the design of the ring (dimensions, material and interface properties, etc.) and on the location of implementation; many different phenomena are involved such as centrifugal and thermal loading, mistuning, etc. Realistic contact modeling and simulation are also difficult because the dynamical behavior is non-linear due to the friction interfaces.
In this work, the effect of a split ring damper is investigated experimentally on an industrial compressor blisk in a vacuum chamber. A traveling wave excitation with a prescribed nodal diameter index is produced using piezoelectric actuators. Blade vibrations are monitored through strain gauges. Forced responses are measured, first on a tuned configuration activating the split ring damping effect on the targeted specific nodal diameter. Then an intentional mistuning pattern is implemented, so that the split ring target nodal diameter appears in different modes of the new configuration. The experiments show that resonance peaks are damped for different modes from that targeted at the tuned design stage.
Liquid Rocket Engine Inducer Pump Design and Performance Evaluation
Authors: de Oliveira Igor , Bringhenti Cleverson , Takachi Jesuino T. , Adalgiza Garcia Maia Ana , Kapat Jayanta S. , Fernandez Erik 
Published: September 2023

Abstract
The inducer is an axial pump that is part of the propellant injection system of Liquid Propellant Rocket Engines (LPRE). It is located at the inlet of the turbopump assembly and is critical for designing high performance LPREs. Its geometric and operational characteristics allow it to operate at low inlet pressures, delaying the appearance of cavitation and allowing the propellant tanks to operate at lower pressures. This allows the tanks to be lighter due to a reduced wall thickness requirement. The inducer also needs to operate harmoniously with the other components of the turbopump, especially with the main impeller which is located just downstream in the system. Therefore, it is important that the flow conditions at the inducer inlet and outlet are known and integrated with the turbopump and tank design. The present work aims to develop a methodology for inducer design based on literature established methods in order to obtain geometry and evaluate the flow conditions in liquid-propelled rocket engine inducer pumps. This work will assess outlet flow and pressure conditions in a way that it is possible to match them with the main impeller inlet. Performance criteria are evaluated in terms of the outlet pressure coefficient, flow coefficient and efficiency focusing exclusively on non-cavitating conditions. Two established analytical methods were implemented, one to provide inducer geometry in terms of system operational requirements and another, from National Aeronautics and Space Administration (NASA), for performance prediction based on geometrical and operational parameters. Further analysis is complemented by simulating the generated geometry in a CFD software. The methods were validated using published experimental data and the performances of the analytical, numerical and experimental results were compared. Results showed that the 3D turbulent CFD simulations provided very good agreement of efficiency. Satisfactory results were obtained for the general trends of characteristic curves over a range of flow rates and the spanwise distribution of key performance parameters near design point. The pressure coefficient was significantly overestimated. The results of the analytical models showed good agreement with simulated CFD results, indicating appropriate calibration of loss coefficients.
Experimental Characterization of Two Low Aspect Ratio Stages With Scaling Effect for Small Core High Speed Axial Compressor
Authors: Babin Cedric , Fontaneto Fabrizio 
Published: September 2023

Abstract
Due to the increase of the overall pressure ratio, forthcoming aircraft engine designs will exhibit smaller core dimensions, compared to the state of the art. For the high-pressure compressor, this imposes the use of blade rows with aspect ratios well below unity. To assess the validity of current design tools for novel designs, two different stages representative of the last stage of a high-pressure axial compressor have been experimentally characterized at the von Karman Institute for Fluid Dynamics. They both share an identical design methodology, same blade count and rotor tip speed but different aspect ratio, yet well below unity. The current paper proposes a comparison between the stages in terms of overall performance and rotor and stator flow fields, at different Reynolds numbers, and for different operating points. The tip-gap influence has also been assessed by comparing scaled and realistic relative tip gap sizes for the low aspect ratio stage. This study aims at providing an identification of the phenomena driving the performance degradation associated with the reduction of the aspect ratio. This description also paves the way for improvement in existing design tools through a better modelling of the critical physics in this design space.
Cyber Security in Compression Stations, A Major Issue for Pipeline Gas Transport
Authors: Bainier Francis , Latreche Abdelbaset 
Published: September 2023

Abstract
Cyber-attacks on hospitals are regularly in the news. Less spectacular than hospitals, cyber-security is a vital issue to ensure the flow in gas pipelines. This paper presents the methodology applied in compression stations at GRTgaz.
Trusting manufacturers is not enough; cyber-security must be understood by asset managers. Asset managers need to understand the cyber-security protections of their suppliers, and in light of this knowledge, they must organize their strategy to cover all the risks they could be exposed to.
In some cases, manufacturers do not comply with the desired requirements. In this case, solutions must be implemented for short or long periods of time, depending on the solutions implemented to cover or reduce the risk.
Most Transmission System Operators (TSOs) do not require to carry out any shift work at their compressor stations. The stations are controlled remotely from a dispatching center, and maintenance teams have remote access to ensure the effective operation. The manufacturer can also have remote access when the location of the compressor units highly impacts the gas flow.
These conditions of operation designate the level of cyber-security required for each station studied.
This paper presents the cyber-security strategy developed and implemented at GRTgaz to minimize the cyber-risks.
On the Use of PSP to Determine the Rim Sealing Effectiveness
Authors: Orsini Lorenzo , Picchi Alessio , Facchini Bruno , Bonini Alessio , Innocenti Luca 
Published: September 2023

Abstract
The control of cavities sealing has been a challenging problem since early gas turbine development stages and several aspects regarding the flow physics and the modelling of rim seal flows, especially in terms of unsteady phenomena, still represent an open question. Fundamental test cases have been extensively used in the open literature to characterize the level of ingestion by varying the main flow parameters and the geometrical features. In most of them, the seal effectiveness is measured by using taps connected to a gas analyzer used to sample the concentration of a reference foreign gas (generally CO2) on the stator surface used to seed the purge flow. Consequently, the results are usually single point measurements and unsteady effects are inevitably neglected. Moreover, the intrusiveness of the approach must be carefully checked and the application on the rotor side demands for complex slip-rings or telemetry. To overcome these limitations, the current work presents the application of the Pressure Sensitive Paint (PSP) technique to the study of hot gas ingestion phenomena on a single stage rotating cold rig. By using an oxygen-free gas such as N2 as purge flow, the PSP were used to measure the partial pressure of oxygen at the wall through the wide optical accesses present in the rig. Then, the collected 2D distributions of pressure were related to the seal effectiveness inside the wheel-space. The proposed methodology was firstly validated through a comparison with the data obtained from standard gas sampling and then applied as main experimental technique to characterize the seal ingestion. The analysis of the results highlighted the capabilities of the PSP technique to fast collect data on both stator and rotor side, including the tip of the seal tooth where non uniform efficiency distributions in the circumferential direction have been detected.
New Compression Solution to Decarbonize Petrochemical Plants
Authors: Berterame Domenico , Gabriele Serena 
Published: September 2023

Abstract
Decarbonization is unavoidable and urgent, however it still sounds like an undefined foggy vision, with detrimental impact on any project budget and risk profile, due to novelty introduction. The purpose of this paper is turning upside down this concept and show with a real example that proven technology can reduce CO2 footprint and, at the same time, squeeze costs even in well-established petrochemical process, like PDH one. The journey has started more than 10 years ago, based on the idea of increasing machine rpm to get more work from it! Thanks to investment in new materials, improved bearings, enhanced predictability together with an extensive test campaign on a full-scale prototype Baker Hughes introduced in 2015 the High-Pressure Ratio Compressor (HPRC). This consists in a new generation technology able to cover with a single compressor body the duty usually requiring multiple casings in series. Bottom line: no process change, same (or better) efficiency, less hardware/material and therefore reduced CO2 impact and cost. This solution was successfully deployed for natural gas compression and today it plays a key role in the H2 world. The today idea is to introduce it in the fast-growing petrochemical market and specifically as Reactor effluent compressor, one of the key equipment in PDH plants. That proprietary process requires 2 compressor bodies however can be properly handled by a single casing without any performance change when applying HPRC design. This results in a proven technology delivering on decarbonization while reducing CAPEX and OPEX.