bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibration Based Condition Monitoring of Helicopter Gearboxes Based on Cyclostationary Analysis
Authors: Mauricio Alexandre , Zhou Linghao , Mba David , Gryllias Konstantinos 
Published: November 2019

Abstract
The core of a helicopter drivetrain is a complex planetary main gearbox (MGB) which reduces the high input speed generated by the engines in order to provide the appropriate torque to the main rotors and to other auxiliary systems. The gearbox consists of various shafts, planetary gears and bearings and operates under varying conditions under excessive friction, heat and high mechanical forces. The components are vulnerable to fatigue defects and therefore Health and Usage Monitoring Systems (HUMS) have been developed in order to monitor the health condition of the gearbox, focusing towards early, accurate and on time fault detection with limited false alarms and missed detections. The main aim of a HUM System is by health monitoring to enhance the helicopters’ operational reliability, to support the maintenance decision making, and to reduce the overall maintenance costs. The importance and the need for more advanced and accurate HUMS have been emphasized recently by the post-accident analysis of the helicopter LN-OJF, which crashed in Norway in 2016. During the last few decades various methodologies and diagnostic indicators/features have been proposed for the monitoring of rotating machinery operating under steady conditions but still there is no global solution for complex structures. A new tool called IESFOgram has been recently proposed by the authors, based on Cyclostationary Analysis, focusing on the accurate selection of a filtering band, under steady and varying speed conditions. Moreover the Cyclic Spectral Coherence is integrated along the selected frequency band leading to an Improved Envelope Spectrum. In this paper the performance of the tool is tested on a complex planetary gearbox, with several vibration sources. The method is tested, evaluated and compared to state of the art methods on a dataset captured during experimental tests under various operating conditions on a Category A Super Puma SA330 main planetary gearbox, presenting seeded bearing defects of different sizes.
Investigation on Unsteady and Steady Swirling Inflow Effect on Turbocharger Turbine Performance
Authors: Ding Zhanming , Zhuge Weilin , Zhang Yangjun , Chen Yingjie , Liu Chang 
Published: November 2019

Abstract
Turbocharger has experienced a prompt expansion in vehicle industry in recent years, because it enables downsizing of internal combustion engines (ICEs) so as to cutting down CO2 emissions. Turbocharger turbine efficiency is vital for the performance and emission of ICEs. Conventionally, turbines are designed and optimized under steady and uniform inflow conditions, but they are always fed with pulsating and swirling inflow on ICEs. Understanding turbine behaviors under enginelike unsteady swirling inflow conditions is significant to improve turbine on-engine performance.
The purpose of the present study is to examine and compare the unsteady and steady swirling inflow effect on turbocharger turbine performance. The investigation reveals that the turbine suffers substantial efficiency reductions under swirling inflow conditions, no matter under unsteady or steady state, and the efficiency reductions are related with the intensity of inlet swirls. The unsteady and steady swirling inflow leads to reductions in both the absolute and relative flow angles. The swirling inflow results in different effect on turbine performance under unsteady state from steady state. Time lags exist between the unsteady swirling inflow affect the turbine performance. Besides, unsteady swirling inflow effect lead to fluctuations of turbine performance parameters, which discloses a coupled effect of the unsteady and swirling inflow. The unsteady effect and the swirling inflow effect do not simply superpose with each other, but have complicated interactions with each other. Both pulsating and swirling inflow can lead to circumferential flow distortions at rotor inlet by themselves, and when turbine is fed with both pulsatile and swirling inflow together the circumferential flow distortion would be result of their synergetic effect.
Application of Design-for-LCA Methodology to Compare Architectural Alternatives for the Compressor Rotor of an Industrial Gas Turbine
Authors: Musacchio Alessandro , Vicarelli Mattia , Colantoni Simone , Bartocci Pietro , Fantozzi Francesco 
Published: November 2019

Abstract
Nowadays a preliminary assessment on environmental impact of a new product is becoming more and more important. It is useful for a designer to access to a comprehensive methodology that supports configuration assessments taking into account the whole product lifecycle from the beginning of conceptual phase. To develop a competitive product, and particularly a gas turbine, each design trade-off needs to be performed considering not only the typical parameters such as performances, life and costs but also the cradle-to-grave environmental impact.
Scope of the following paper is the application of design-for-Environment methodology to different architectures of GT compressor rotor module. Three design alternatives are analyzed and compared in terms of ELCA considering their design, material selection, manufacturing process and operating life. Specific considerations are proposed as a result of the combination of traditional design practices with environmental assessment.
This study highlighted that number of parts, weight and amount of material removed or scraped that is, in other words, the level of production process optimization, are the key factors to control the environmental impact of a product.
The Role of Turbomachinery Performance in the Optimization of Supercritical Carbon Dioxide Power Systems
Authors: Romei Alessandro , Gaetani Paolo , Giostri Andrea , Persico Giacomo 
Published: November 2019

Abstract
The successful penetration of supercritical carbon dioxide (sCO2) power systems in the energy market largely depends on the achievable turbomachinery performance. The present study illustrates a systematic framework where both the compressor and the turbine are designed via validated (within ±2% pts against experiments) mean-line tools and the related impact on cycle performance estimates is quantitatively and qualitatively assessed. A significant effort is devoted to the analysis of centrifugal compressor performance operating close to the critical point, where sharp thermodynamic property variations may make critical the compression process. The analysis is performed for different compressor sizes and pressure ratios, showing a comparatively small contribution of compressor-intake fluid conditions to the machine efficiency, which may achieve technological competitive values (82 ÷ 85%) for representative full-scale sizes. Two polynomial correlations for both turbomachinery efficiencies are devised as a function of proper similarity parameters accounting for machine sizes and loadings. Such correlations can be easily embedded in power cycle optimizations, which are usually carried out assuming constant-turbomachinery efficiency, thus ignoring the effects of plant size and cycle operating parameters. Efficiency correlations are finally exploited to perform several optimizations of a recompressed sCO2 cycle, by varying multiple cycle parameters (i.e. maximum and minimum temperature, pressure ratio and net power output). The results highlight that the replacement of constant-efficiency assumption with the proposed correlations leads to more accurate performance predictions (i.e. cycle efficiency can differ by more than 4% pts), showing in particular that an optimal pressure ratio exists in the range 2 ÷ 5 for all the investigated configurations.
The Effect of Rated Climb Performance on Low Cycle Fatigue of a Civil Turbojet Engine
Authors: König Jonas , Weißschuh Matthias , von Ende Sven , Staudacher Stephan 
Published: November 2019

Abstract
Low cycle fatigue (LCF) of jet engine disks is a major contributor to the maintenance costs of an engine. The current industry standard for the analysis of LCF is to use representative flight missions to reflect the in-service usage of engines. Based on the engine performance during those missions, the internal stresses and temperatures of life-critical components are calculated. These stresses and temperatures define the cyclic life consumption of a mission and determine the certifiable LCF life of the engine. The engine performance is defined by the power setting schedules of the engine, so-called engine ratings. The effect of the rated climb performance on high pressure turbine disk life is investigated for a generic two-shaft engine operated in a small twin-jet civil aircraft. LCF life is analyzed using a finite element-based cycle counting model. The aircraft climb performance resulting from the changed climb ratings is assessed with an aircraft performance model. It is shown that there are climb ratings which result in reduced LCF life consumption and climb time compared to the reference rating. Employing these ratings on in-service engines increases the certifiable life count and reduces maintenance costs.
Experimental Investigation of a RQL Burner With Jet in Cross Flow Fuel Injection: Characterization of the Reacting Flow Field at Realistic Operating Conditions
Authors: Soworka T. , Behrendt T. , Hassa C. , Heinze J. , Magens E. , Schroll M. , di Mare F. , Ballantyne S. , Gregory J. 
Published: November 2019

Abstract
Future rich-burn/quick-quench/lean-burn (RQL) burners for aero engines face the challenge to further reduce the emission of soot. Alternative ways of fuel injection are therefore in the focus of modern RQL combustion systems. This contribution aims to investigate experimentally the influence of fuel injection on the reacting flow field, with the emphasis on soot production in the primary zone. For the test, a Rolls-Royce prototype burner was used in two different configurations which differ only in the axial location of jet in cross flow fuel injection and thereby provoke different ways of fuel atomization. In the upstream configuration the burner features characteristics of a pre-filming airblast atomizer. Whereas with the fuel tip in downstream position solely Jet-in-Cross-Flow fuel atomisation is expected. The burner was tested at realistic aero engine combustor conditions (p30 = 9.28 bar, T30 = 603 K, AFR = 7.6). Several optical measurement techniques were used to characterise the reacting flow field. Their difficult application in a rich burn environment is described briefly. The structure of the reacting flow field is illustrated by Particle-Image-Velocimetry (PIV). Planar Mie scattering and Planar Laser-Induced Fluorescence (PLIF) are used to characterise the placement of liquid and gaseous fuel respectively. The location and structure of heat release zones are captured in terms of OH* and CO2* chemiluminescence. Finally Laser-Induced-Incandescence (LII) is used to obtain three dimensional soot distributions in the primary zone. On this basis 20% less soot was measured for the upstream configuration at the axial location of maximal soot concentration. This remarkable difference could be attributed to the different placement of liquid fuel and the resulting better mixing.
Computational and Experimental Study of Hot Streak Transport Within the First Stage of a Gas Turbine
Authors: Gaetani Paolo , Persico Giacomo , Pinelli Lorenzo , Marconcini Michele , Pacciani Roberto 
Published: November 2019

Abstract
The paper discusses the migration, the interaction with the blades, and the attenuation of hot streaks generated by combustor burners, during their propagation within the first turbine stage of aero-engines. Experiments and Computational Fluid Dynamic (CFD) simulations were carried out in the framework of the European Project RECORD and on its follow-up. Measurements considering burner-representative temperature perturbations injected upstream of an un-cooled high-pressure gas turbine stage were performed in the high-speed closed-loop test-rig of the Politecnico di Milano (Italy). The hot streaks were injected in streamwise direction at the stage inlet in four different circumferential positions with respect to the stator blade. They feature a 20% over-temperature with respect to the main flow. Detailed temperature measurements as well as unsteady aerodynamic measurements upstream and downstream of the blade rows were performed. Time-accurate CFD simulations of the flow upstream and within the turbine stage were performed with the TRAF code, developed by the University of Florence. Measurements show a relevant attenuation of hot streaks throughout their transport within the stator and the rotor blade rows, highly depending on the injection azimuthal position. The perturbations were observed to lose their spatial coherence, especially in the transport within the rotor, and to undergo severe spanwise migration. Simulations exhibit a good agreement with the experiments on the measurement planes and allow tracking the complex flow phenomena occurring within the blade rows. Finally the aerodynamic and thermal implications of the inlet temperature perturbations are properly highlighted and discussed.
Reducing Secondary Flow Losses in Low-Pressure Turbines With Blade Fences: Part I — Design in an Engine-Like Environment
Authors: Rubechini Filippo , Giovannini Matteo , Arnone Andrea , Simoni Daniele , Bertini Francesco 
Published: November 2019

Abstract
This paper deals with the design of passive control devices for reducing the impact of secondary flows on the aerodynamics of low-pressure turbine (LPT) stages. A novel kind of device is introduced which consists of shelf-like fences to be added to the blade surface. Such a device is intended to hinder the development of secondary flows, thus reducing losses and flow turning deviation with respect to the straight blade.
The first part of this work is devoted to the design of the blade fences, whereas the second part addresses the experimental validation of the device. The blade fences are designed on a LPT stator vane, in an engine-like environment. As secondary flows generated by one blade row produce their major effects on the downstream one, and hence on the stage performance, the assessment is performed on a stator-rotor configuration. Steady calculations are considered for the design, then the optimal geometry is verified via unsteady calculations to include the effects of the actual interaction. The geometry and layout of the blade fences are effectively handled by means of a parametric approach, which enables the fast generation of several configurations. An optimization procedure, based on Artificial Neural Networks (ANNs) is exploited to drive the fences design. The analysis of the relative merit of each solution is carried out using a state-of-the-art CFD approach. Finally, a detailed comparison between the original blade and the one equipped with fences is presented, and the physical mechanisms responsible for the mitigation of secondary flow losses are discussed in detail.
Nonsynchronous Vibration Associated With Transonic Fan Blade Untwist
Authors: Lu Yaozhi , Lad Bharat , Vahdati Mehdi , Stapelfeldt Sina C. 
Published: November 2019

Abstract
Due to manufacturing tolerance and deterioration during operation, fan blades in the aero-engine exhibit geometric variability. This leads to asymmetry in the assembly which will be amplified in the running geometry by centrifugal and aerodynamic loads. This study investigates a phenomenon known as Alternative Passage Divergence (APD), where the blade untwist creates an alternating pattern in passage geometry and stagger angle around the circumference, resulting in two groups of blades. This phenomenon occurs close to, or at, peak efficiency conditions and can significantly reduce overall efficiency. This study focuses on a type of non-integral vibration which occurs during APD. After the formation of alternating tip stagger pattern, APDs unsteady effect can cause the blades from one group to switch to the other, creating a travelling wave pattern around the circumference.It was found from numerical assessment on a randomly mis-staggered assembly that real engines can potentially experience such travelling disturbance and suffer fatigue damage. An idealised case is used to capture the bulk behaviour from the more complex cases in real engines and to decipher the underlying mechanism of this travelling disturbance. The results indicate that the driving force originates from the interaction between passage shock displacement and the passage geometry.
Prediction of Film Thickness of an Aero-Engine Bearing Chamber Using Coupled VOF and Thin Film Model
Authors: Singh Kuldeep , Sharabi Medhat , Ambrose Stephen , Eastwick Carol , Jefferson-Loveday Richard 
Published: November 2019

Abstract
In the present work, a coupled volume-of-fluid (VOF) model with Eulerian thin-film model (ETFM) approach is used to predict the film thickness in an aero-engine bearing chamber. Numerical studies are conducted for a wide range of shaft speeds with lubricant and air flow rates of 100 1/hr and 10 g/s respectively, at a scavenge ratio of 4 on a simplified bearing chamber test rig. Air-flow analysis inside the bearing chamber is also assessed. Primary and secondary airflow predictions are found to be in good agreement with the experimental results. The coupled ETFM+VOF approach is found to be sensitive enough to capture the qualitative trend of oil film formation and distribution over the chamber wall. Oil collection near the sump at a low shaft speed and a rotating oil film at a higher shaft speed are well captured.
Analysis of Composite Blade/Casing Rub Stability Through Delayed Differential Equations
Authors: Xiao Jiaguangyi , Chen Yong , Tian Jie , Ouyang Hua , Wang Anjenq 
Published: November 2019

Abstract
To improve aerodynamic efficiencies, the clearances between blades and casings are becoming smaller and smaller in the aero-engine industry, which might lead to the interactions between these components. These unexpected interactions are known as the so called blade/casing rubs. Abradable materials are implemented on the inner surface of the casings to reduce the potential damages caused by it. However, failures may still arise from blade/casing rubs according to experimental investigations and actual accidents.
In this paper, a reduced-order delayed differential equations are used to simplify the rubbing process between composite blade and casing. It is assumed that the removal of the abradable material in blade/casing rubbing process shares a resemblance with machine tool chatters encountered in machining. The delayed differential equations are established with centrifugal stiffness and the impacts of stacking sequences on the blade damping taking into consideration. Semi-Discretization Method (SDM) is used to study the stabilities of the simplified system, which is verified by Cluster Treatment of Characteristic Roots (CTCR) and direct integrations. The results show that the stacking sequences, rub positions, blade damping and stiffness could have much impact on the relatively dangerous interaction regimes. With the help of this method, one can assist the design processes of the composite blade-casing interface in initial aero-engine structural designs.
Numerical Investigations of Pollutant Emissions From Novel Heavy Duty Gas Turbine Burners Operated With Natural Gas
Authors: Pampaloni Daniele , Nassini Pier Carlo , Andreini Antonio , Facchini Bruno , Cerutti Matteo 
Published: November 2019

Abstract
A numerical investigation of pollutant emissions of a novel dry low-emissions burner for heavy-duty gas turbine applications is presented. The objective of the work is to develop and assess a robust and cost-efficient numerical setup for the prediction of NOx and CO emissions in industrial gas turbines and to investigate the pollutant formation mechanisms, thus supporting the design process of a novel low-emission burner. To this end, a comparison against experimental data, from a recent experimental campaign performed by BHGE in cooperation with University of Florence, has been exploited.
In the first part of this work, a RANS approach on both a simplified geometry and the complete domain is adopted to characterize the global flame behavior and validate the numerical setup. Then, unsteady simulations exploiting the Scale Adaptive Simulation (SAS) approach have been performed to assess the prediction improvements that can be obtained with the unsteady modelling of the flame.
For all simulations, the Flamelet Generated Manifold (FGM) model has been used, allowing the reliable and cost-efficient application of detailed chemistry mechanisms in CFD simulation. However, FGM typically faces issues predicting flame emissions, such as NOx and CO, due to the wide range of time scales involved, from turbulent mixing to pollutant species oxidation. Specific models are typically used to predict NOx emissions, starting from the converged flow field and introducing additional transport equations. Also CO prediction, especially at part-load operating conditions could be an issue for flamelet-based model: in fact, as the load decreases and the extinction limit approaches, a super-equilibrium CO concentration, which cannot be accurately predicted by FGM, appears in the exhaust gases. To overcome this issue, a specific CO burn-out model, following the original idea proposed by Klarmann, has been implemented in ANSYS Fluent. The model allows to decouple the effective CO oxidation term from the one computed by FGM, defining a post-flame zone where the source term of CO is treated following the Arrhenius formulation.
In order to support the design process, an in-depth CFD investigation has been carried out, evaluating the impact of an alternative burner geometrical configuration on stability and emissions and providing detailed information about the main regions and mechanisms of pollutants production. The outcomes support the analysis of experimental results, allowing an in-depth investigation of the complex flow-field and the flame-related quantities, which have not been measured during the tests.
Impact of Wall Temperature in Large Eddy Simulation of Light-Round in an Annular Liquid Fueled Combustor and Assessment of Wall Models
Authors: Puggelli S. , Lancien T. , Prieur K. , Durox D. , Candel S. , Vicquelin R. 
Published: November 2019

Abstract
The process of ignition in aero-engines raises many practical issues that need to be faced during the design process. Recent experiments and simulations have provided detailed insights on ignition in single-injector configurations and on the light-round sequence in annular combustors. It was shown that Large Eddy Simulation (LES) was able to reliably reproduce the physical phenomena involved in the ignition of both perfectly premixed and liquid spray flames. The present study aims at further extending the knowledge on flame propagation during the ignition of annular multiple injector combustors by focusing the attention on the effects of heat losses, which have not been accounted for in numerical calculations before. This problem is examined by developing Large Eddy Simulations of the light-round process with a fixed temperature at the solid boundaries. Calculations are carried out for a laboratory-scale annular system. Results are compared in terms of flame shape and light-round duration with available experiments and with an adiabatic LES serving as a reference. Wall heat losses lead to a significant reduction in the flame propagation velocity as observed experimentally. However, the LES underestimates this effect and leads to a globally shorter light-round. To better understand this discrepancy, the study focuses then on the analysis of the near wall region where the velocity and temperature boundary layers must be carefully described. An a-priori analysis underlines the shortcomings associated to the chosen wall law by considering a more advanced wall model that fully accounts for variable thermophysical properties and for the unsteadiness of the boundary layer.