bluuebunny/crossref_metadata_2025_split huggingface dataset:
Squeeze Film Dampers Design and Application in High-Speed Radial Outflow Turbines for Small Size Organic Rankine Cycles
Authors: Gheller Edoardo , Chatterton Steven , Bassi Federico , Scala Michele , Dassi Ludovico , Pennacchi Paolo 
Published: September 2023

Abstract
The design of high-performance small-scale Organic Rankine Cycle (ORC) systems is heavily dependent on optimizing major power plant components. In Radial Outflow Turbines (ROT) greater efficiency is achieved by increasing the rotation speed and decreasing sealing losses by reducing the clearance of labyrinth seals. These solutions, together with the use of high molecular weight organic fluids, might lead to potential rotor dynamics issues related to super-critical rotor design and seal induced instability. To overcome this problem, a Squeeze Film Damper (SFD) is introduced to an overhung rotor configuration with angular contact ball bearings. Its effectiveness in reducing the amplification factor due to unbalance and seal instability is discussed and demonstrated by finite element (FE) simulations. A sensitivity analysis is performed on key SFD parameters of clearance, length, and groove size and an optimal design is selected.
Experimental Validation of a Seal Flutter Model
Authors: Corral Roque , Greco Michele 
Published: September 2023

Abstract
In this paper, the predictions of an analytical model for seal flutter have been compared with the experimental data of a rotating multi-cavity labyrinth seal test rig. The experiments were conducted to assess the flutter inception in a large set of operating conditions by varying the rotational speed and the total pressure ratio across the seal. The analytical model derived by Corral et al. (2022, “ Effective Clearance and Differential Gapping Impact on Seal Flutter Modelling and Validation,” ASME J. Turbomach, 144 (7), pp. 071010) has been previously validated by using a frequency domain linearized Navier-Stokes solver retaining the effect of the effective gaps and the kinetic energy carried over to the downstream fin. A set of 3D steady RANS simulations has been carried out to reduce the uncertainty in the steady characteristics of the seal that are used to inform the flutter model. The simulations consider the static deformation due to the pressure and the centrifugal force through a set of numerical models with geometrical gap differences. The stability has been investigated in a large range of operating conditions. It is concluded that the analytical model can be used to quickly predict the modes susceptible to flutter, provided that the steady flow field and the effective running clearances of the seal are well predicted.
A Methodology to Quantify Product Competitiveness and Innovation Requirements for Micro Gas Turbine Systems in Hydrogen Backup Applications
Authors: Tilocca Giuseppe , Sánchez David , Torres-García Miguel , Escamilla-Perejón Antonio , Minett Simon 
Published: September 2023

Abstract
Micro gas turbines are an on-site power and heat generation technology with a small footprint, low gaseous (NOx) and acoustic emissions, low maintenance and high-grade heat. They entered the market at the dawn of the twentieth century; nevertheless, they achieved minimal success and a marginal role in the microgeneration market. Reciprocating internal combustion engines raised considerable barriers hindering their market deployment, and Fuel Cells are also set to compete in this segment.
In this scenario, this work presents an analysis of competitiveness grounded in the Theory of Constraints. To this end, a specific Key Performance Indicator has been produced, which combines technical, economic, and operational factors according to the end-user requirement. This indicator is a function of several penalty factors representing technology and market barriers, which aims to yield a unique insight into the most competitive technology for a given application, accounting for the uncertainty deriving from technical and economic elements.
This novel methodology is applied to a new potential niche market: Power-to-Hydrogen-to-Power for remote applications. The methodology is applied to an independent rural community in South Wales, for which a backup power system is assessed. Four technologies are considered in the analysis: reciprocating engines, fuel cells and two different microturbines layouts.
Finally, this work provides an overview of the possible R&D&I paths necessary to increase the competitiveness of micro gas turbines in certain markets.
Emissions and Flame Structure Assessment of Aeroengine Micromixing Injectors for Lean Direct Injection of Hydrogen and Hydrogen/Natural Gas Blends
Authors: Tran Britney , Gomez Escudero Iker , McDonell Vincent 
Published: September 2023

Abstract
The present study focuses on whether adapting low emissions liquid fuel injection concepts can be applied to gaseous mixtures. The goal is to develop an injector with specific geometric characteristics that will achieve the lowest emissions. This is conducted by evaluating emissions and flame diagnostics on a set of test hardware that has been developed for combustion of pure hydrogen and hydrogen/methane mixtures. The current test hardware adapts lean direct injection concepts from aeroengine injectors to a ground-based engine based on target flows associated with a Solar Turbines Industrial Engine gas turbine. A statistical test plan was developed to assess these geometric characteristics using a three level Box Behnken design. The test plan investigates the effect of injector flow splits, air swirl, fuel swirl, pressure drop, preheat temperature, fuel composition, and the adiabatic flame temperature on the flame structure and emissions performance. A total of 16 injectors were considered for a total of 688 test points for emission and imaging data. Emissions data were reported on a mass basis in ng/J and chemical reactor network analysis were conducted to further interpret emissions behavior. Images were also captured to analyze the flame structure features of interest including reaction volume, flame length, flame spread, and flame width. With these results, a predictive model for emissions was made to conclude the most optimal injector configuration is to have the highest level of air split (more volume of air through the injector plate versus the injector) and air swirl angle for both methane and hydrogen gas mixtures. The predictive emissions level for all of these cases were below 10 ng/J.
Comparison of Dirt Deposition on Double-Walled Combustor Liner Geometries
Authors: Fallon Brandon , McFerran Kyle , Fox Sarah , Thole Karen A. , Lynch Stephen P. , Lundgreen Ryan , Kramer Stephen P. 
Published: September 2023

Abstract
Gas turbine engines are frequently subjected to particle laden flows in which dirt and sand are ingested into the hot section. The particles enter internal cooling channels where they deposit and block cooling features, creating increased heat transfer, reduced flows, and diminished cooling performance. This study investigates geometries with the intention of mitigating dirt effects on cooling for double-walled combustor liners that use impingement and effusion cooling. Dirt particulate was injected into several double-walled coupons at room temperature using two feed modes: slug and continuous. Slug feed tests used controlled bursts of dirt whereas continuous feed provided a steady stream of dirt. Computational studies were also conducted to investigate internal flow fields between the impingement and effusion plates. The best performing geometry that was tested in terms of the lowest measured dirt capture had pins and cones extruded from the cold-side of the effusion plate. The flow parameter was found to scale the dirt capture with higher capture efficiency at higher flow parameters.
Sand Ingress in Gas Turbines Operating in Desert Environments: Observations and CFD Simulations
Authors: Tayebi Kamel-Abdelkader , Nair Sumith , Jupudi Maruthi Manohar , Dawood Alaaeldin , Khalidi Abdurrahman 
Published: September 2023

Abstract
Gas Turbines operating in desert and dusty environments inherently pull air that is contaminated with particles of sand/dust. In certain conditions of filter bypass, these particles find their way to the cold and hot sections of the gas turbine affecting performance and parts fitness for use, sometimes leading to forced outages and expensive parts repair and replacement.
In the first part of this paper, we describe some observations from cases in the Middle East. In the second part of the paper, we present the results of CFD simulations of sand ingress through the air filtration house and into the compressor of a gas turbine operating in a desert environment. Simulations are performed at increasing levels of contamination. We discuss the influence of ingested particles size and distribution as they relate to the level of contamination observed in desert environments including the case of severe sandstorms.
Effect of Inflow Swirl on the Sealing Effectiveness of Turbine Rim Seal
Authors: Cong Qingfeng , Lei Long , Zhang Kaiyuan , Li Zhigang , Li Jun 
Published: September 2023

Abstract
Turbine inlet swirl condition is inherently present at the combustion chamber outlet and has an important influence on mainstream flow and gas ingestion. The sealing effectiveness and ingestion mechanism were numerically investigated using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations coupled with a fully developed shear stress transport (SST) turbulent model. Mass transfer analogy is utilized to simulate the hot gas ingestion and sealant egress by seeding CO2 into the air as a tracer gas. Simulations with mainstream inflow swirls of 0°, ±10°, ±20° were conducted and compared. Computational results indicate that at the same sealant flow rate, the sealing effectiveness increases significantly with the increase in the incidence angle at the leading edge of stationary vanes. When the non-dimensional sealant rate is 0.02415 and the incidence angle is increased from 0° to +10° and +20°, the sealing effectiveness at r/b = 0.958 on stationary disk is increased by 3.39% and 13.26%, respectively. The area-averaged sealing effectiveness of +20° incidence angles at the stationary and rotating disk can be increased by 12.02% and 5.19%, compared with the 0° incidence angle. The incidence angle near the vane leading edge affects the formation position of the horseshoe vortex, and ultimately affects the passage vortex. Therefore, the flow field in the rim seal clearance changes greatly. From axial and radial perspectives, the vortex due to Kelvin Helmholtz instability increases the blockage of axial rim seal clearance with the increase in incidence angle. From a circumferential perspective, as the incidence angle increases, a vortex structure is induced at the entrance of the rim seal, and the radial scale of the vortex decreases and the axial scale increases. All variations can gradually weaken the gas ingestion and improve the sealing effectiveness in the disk cavity. Based on fast Fourier transform (FFT) and analyzing the unsteady mass flow rate of ingress through the rim seal, the influence of the vortex due to Kelvin Helmholtz instability with a period of about 20 time-steps plays a major role in influencing sealing performance. The sealing effectiveness and flow pattern in the rim seal clearance have strong unsteady characteristics with this period.
Experimental Study of a Low NOx and Soot Injection System for Spinning Combustion Technology: Characterization of Soot and NO Formation Under Realistic Operating Conditions by Laser Diagnostics
Authors: Milea Andrei-Silviu , Perrier Aurélien , Caceres Marcos , Vandel Alexis , Godard Gilles , Renard Fabien , Duchaine Patrick , Richard Stephane , Cabot Gilles , Grisch Frédéric 
Published: September 2023

Abstract
In the context of air pollution, Safran Helicopter Engines patented an innovative design for helicopter combustors based on Spinning Combustion Technology. The development focuses on novel concepts of kerosene fuel injectors aiming to further reduce NOx and soot particle emissions. Experimental studies are performed on the fuel injectors in a high-pressure/high-temperature combustion facility designed by the CORIA laboratory. This test bench is able to reproduce the same conditions encountered in a helicopter combustor over the entire range of nominal operating conditions and has large optical accesses for the implementation of optical diagnostics. NOx and soot particles are assessed during three experimental studies, two of which focus on each pollutant individually and a third one specially dedicated for high-speed velocity measurements by PIV. Soot particles distribution, flame structure and fuel distribution were obtained by coupling the PLIF-OH, PLIF-kerosene and PLII diagnostics. On the other hand, the PLIF-NO combined with PLIF-OH and PLIF-kerosene allows to study the formation of NO with the combustion process and the fuel distribution.
Generation of Entropy Waves by Fully Premixed Flames in a Non-Adiabatic Combustor With Hydrogen Enrichment
Authors: Eder Alexander J. , Dharmaputra Bayu , Désor Marcel , Silva Camilo F. , Garcia Alex M. , Schuermans Bruno , Noiray Nicolas , Polifke Wolfgang 
Published: September 2023

Abstract
Thermoacoustic combustion instability is a major concern in gas turbine combustors with hydrogen-enriched fuels. Unsteady combustion not only generates acoustic waves, but it may also result in fluctuations of burnt gas temperature, referred to as entropy waves. They are convected by the mean flow through the combustor and can cause indirect combustion noise when they are accelerated at the exit. In this work, we demonstrate that entropy waves occur in a fully premixed burner due to unsteady heat transfer at the combustion chamber wall. This mechanism of entropy generation is often neglected in the literature. This work shows an additional mechanism in CH4-H2-air flames, through which entropy may be created even in the fully premixed case. This is due to differential diffusion which generates local fluctuations in equivalence and carbon-to-hydrogen ratios. An adiabatic flame temperature is defined based on these two quantities to examine the influence of differential diffusion on the generation of entropy fluctuations. The generation of entropy waves is investigated by applying system identification (SI) to time series data obtained from a broadband forced large eddy simulation (LES) coupled with a heat conduction solver. The entropy transfer function (ETF) and flame transfer function (FTF) identified are then compared to experimental data obtained with tunable diode laser absorption spectroscopy with wavelength modulation spectroscopy (TDLAS-WMS) for measuring temperature fluctuations, and the multi-microphone method (MMM), respectively. After validating the computational setup, the entropy frequency response is identified at various positions within the combustion chamber, and the effects of generation and convective dispersion of entropy waves are qualitatively investigated. We show that a fully premixed turbulent system may exhibit significant entropy waves caused by wall heat losses and differential diffusion of hydrogen.
A Novel Prediction Model for the Aerodynamic Losses Increase Due to Film Cooling Injections From Gas Turbine Vane Surface
Authors: Wang Yulin , Guo Can , Chen Xinnan , Sun Tianyi , Chen Dawei , Li Zhigang , Li Jun 
Published: September 2023

Abstract
In this paper, experimental and numerical investigations were conducted on the aerodynamic performance of a turbine vane cascade with film cooling injections. The impact of coolant injection on aerodynamic losses was investigated, and thus a novel prediction model was proposed to estimate the aerodynamic penalty associated with film cooling injections. Three-dimensional numerical simulations performed in this paper were based on the commercial CFD solver ANSYS CFX. To analyze the effects of hole position on the aerodynamic performance, a validated computational model was proposed for the turbine vane cascade with single row film holes either on the suction surface, the leading edge, or the pressure surface. Total pressure loss coefficients were further evaluated and analyzed for typical ranges of blowing ratio (0.5 to 1.5) and coolant injection angle. It is found that, total pressure loss coefficients increase with increasing blowing ratio to different extent depending on the hole position, and the loss associated with coolant injection from the suction surface are highest. Using co-relation mathematical models to predict the penalty is challenging due to the complicated three-dimensional flow structure. The applicability and accuracy of a published loss model, Hartsel model, were evaluated in this study. The prediction of Hartsel model showed largely dependent on the local Mach number of mainstream and the velocity of coolant injection. This suggests that the Hartsel model can’t predict total pressure losses for various locations of turbine airfoil cascade well. For these reason, this present work further develop the applicability and accuracy of the Hartsel model to a satisfactory level. Results indicate that the present model can accurately predict total pressure loss coefficients of film holes at different positions when the blowing ratio is in the range of 0.5 to 1.5 and the incidence angle of cooling air varies in a specified extend.
Methods for the Preliminary Design of Heat Exchangers in Aircraft Engines
Authors: Schmelcher Marc , Häßy Jannik , Görtz Alexander , El-Soueidan Mahmoud 
Published: September 2023

Abstract
The Water-Enhanced Turbofan (WET) is a promising approach to increase engine efficiency and to reduce emissions. For this concept, a Heat Recovery Steam Generator (HRSG) is required to evaporate and superheat liquid water before injecting it into the combustor. However, the integration of a HRSG into an aero engine has not been investigated in detail yet and the design specifications as well as metrics differ from state of the art, ground-based HRSG applications. Therefore, this paper presents methods and correlations that are combined to build a preliminary design tool for heat exchangers with evaporation. The resulting model is verified by a comparison to experimental heat exchanger studies. Finally, the model is used to assess a HRSG located downstream of the turbine section of a generic aero engine evaporating different water mass flows. The large differences in exhaust temperature and mass flow between cruise and take-off conditions outline the difficulty in finding a well balanced HRSG design.
Impact of High-Pressure-Turbine Purge Flow on the Evolution of Turbulence in a Turbine Vane Frame
Authors: Hafizovic Asim , Merli Filippo , Krajnc Nicolas , Schien Malte , Peters Andreas , Heitmeir Franz , Göttlich Emil 
Published: September 2023

Abstract
This paper describes the measurement and postprocessing of turbulence data. The experiments were carried out in a two-stage two spool transonic turbine test rig at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology, which includes relevant purge and turbine rotor tip leakage flows. The test setup consists of a high-pressure turbine (HPT) stage, a turbine vane frame (TVF) with turning struts and splitters and a counter-rotating low-pressure turbine (LPT) to allow engine realistic measurements. Time-resolved area traverse measurements have been performed for three different operating conditions in three measurement planes downstream of the HPT rotor, which enable the measurement of the turbulence quantities at the TVF inlet and outlet as well as LPT outlet. The turbulence quantities are evaluated using triaxial- and single hot-film probes by means of Constant-Temperature-Anemometry, and their results were validated with Five-Hole Probe (FHP) measurements. Ensemble- and time-averaging as well as Fourier transforms, were applied for data reduction.
It is shown how the turbulence intensity and integral length scale vary over different purge flow rates (PFR). The acquired measurement data illustrates that the interaction of the ejected purge flow with mean flow enhances the turbulent mixing in the secondary flow structures at the TVF inlet and TVF outlet, respectively. Furthermore, the flow downstream of the LPT rotor is affected by TVF and LPT rotor secondary flow structures, which are identified as high turbulence regions. These regions strongly depend on the purge flow rate. These results acquired under engine realistic rigs flow conditions enable a deeper understanding of the relationship between loss and turbulence quantities and will help improve the application of CFD turbulence models to turbomachinery modeling.
A Probabilistic Model of Icing Induced Fan Unbalance
Authors: Liao Shengfang 
Published: September 2023

Abstract
A probabilistic model has been developed to simulate the fan unbalance caused by the ice accretion and shedding. The non-uniform ice shedding around the fan circumference was modeled by applying variations of ice adhesion strength to the fan blades. A simple ice accretion/shedding process was simulated with simplified fan blade geometries. Monte Carlo simulations were conducted for large samples of fan blades with randomly assigned ice adhesion strength. The mean and the standard deviation of the maximum fan unbalance were derived from the Monte Carlo simulations. The model is able to capture the major trends of the fan unbalance against various parameters. The mean fan unbalance was found to increase with decreasing fan speed, increasing ice adhesion strength. The unbalance sensitivity to the ice adhesion variations depends on the water impingement profiles. There exists a water impingement radial profile, 1/r-profile, that causes the worst fan unbalances. Finally, non-dimensional fan unbalance and centrifugal force are proposed to scale the fan unbalance from one engine to another engine of different size.
Brush Seal Wear Measurements for High-Speed, High-Temperature, Low-Pressure-Turbine Applications
Authors: Versluis Joris , Mosbacher Mike , Göttler Johann , Mandard Romain 
Published: September 2023

Abstract
This paper presents results of measurements with brush seals in a test-rig mainly operating at high speed and high temperature conditions. The measurements were carried out to investigate wear mechanisms, seal wear rates a nd the effect on seal clearance. A new optical measurement system for the purpose of the experiments with brush seals was developed allowing an accurate setting of the eccentric interference during the rub tests. Various types of tests were carried out to cover the different types of rub experienced within the operating range of a low pressure turbine. Known wear mechanisms reported in earlier publications and also from in-house experience were confirmed during the test campaign and recent experiences with rotor wear due to brush seal contact could be reproduced on the rig and are now much better understood. Cyclic tests also showed the behavior of the seal over time and provided new insights into the dependencies of bristle wear and operating conditions. Additionally some comparisons of the results with field data were made to draw first conclusions regarding the relevance of the tests for the real life applications.