bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurements of Static and Dynamic Load Performance of a 102 mm Carbon-Graphite Porous Surface Tilting-Pad Gas Journal Bearing
Authors: San Andrés Luis , Bolen Rachel , Yang Jing , McGowan Ryan 
Published: September 2021

Abstract
Aerostatic journal bearings with porous tilting pads enable shaft support with minute drag power losses. To date archival information on the static and dynamic load performance of this bearing type is scant. Thus, the paper presents measurements conducted with an air lubricated bearing with diameter d = 102 mm and comprising four tilting pads made of porous carbon-graphite, each with length L = 76 mm. Two nested Belleville washers resting on spherical pivots support each pad. At ambient temperature of ∼ 21°C, as the air supply pressure into the bearing pads increases, so does the bearing aerostatic specific load (F/(L·d)) that reaches 58% of the pressure difference, supply minus ambient. With an air supply pressure of 7.8 bar(a), the test bearing static stiffness KS = 13.1 MN/m, is independent of both shaft speed and static load. KS is just 63% of the washers’ stiffness KP = 20.6 MN/m (during loading). While operating with shaft speeds equal to 6 krpm and 9 krpm (150 Hz) and under specific loads to 115 kPa and 101 kPa respectively, dynamic load experiments with excitation frequencies up to 342 Hz show the test bearing supplied with air at 7.8 bar(a) has frequency independent stiffness (K) and damping (C) coefficients. For rotor speeds equaling 0, 6 and 9 krpm, the bearing direct stiffnesses KXX ∼ KYY range from 13.6 MN/m to 32.7 MN/m as the specific load increases from 0 kPa to 115 kPa. The direct damping coefficients CXX ∼ CYY are as large as 5.8 kN·s/m, though having a large experimental uncertainty. Bearing cross-coupled force coefficients are insignificant. The test porous gas bearing reached its intended load capacity, demonstrated a dynamically stable operation and produced force coefficients mainly affected by the pads’ pivot supports and the magnitude of air supply pressurization.
Aeroderivative Gas Turbine Enclosure Ventilation System
Authors: Yerram Ravinder , Watkins Richard , Ponnuraj Balakrishnan 
Published: September 2021

Abstract
GE Aeroderivative Gas Turbines are derived from GE’s Aircraft engine family and converted to Land and Marine applications. As these Aeroderivative Gas Turbines are relatively smaller in size for similar power capacity in comparison to Heavy Duty Gas Turbines, there is a great need of developing efficient and compact turbine enclosure ventilation system for proper cooling and ventilation. Ineffective ventilation flow distribution inside the gas turbine enclosure causes engine circumferential nonuniform temperature distribution and it allows the formation of explosive fuel gas pockets inside the enclosure in the unlikely event of fuel leaks. Also, the engine nonuniform circumferential temperature gradient has an adverse impact on the operational efficiency and/or the mechanical integrity of the turbine. Proper cooling and ventilation system will also protect the sensitive equipment, like fuel valve actuators or any other instruments inside the turbine enclosure due to excessive radiation heat from engine hot surfaces, mainly near combustor and power turbine region. All the expected but significant engine leakages into the enclosure are estimated and considered for selection of right size, type, placing of ventilation fan at different operating conditions like full load, part load, elevation and ambient conditions. For first step, a 3D Computational Fluid Dynamics (CFD) analyses were done for turbine enclosure with mass/volumetric flow rate, temperature, and pressure boundary conditions to understand the flow/temperature distribution inside the enclosure. Radiation boundary conditions are applied on the engine casing external surfaces, enclosure walls and roof. The convective heat transfer from the hot surfaces are computed by CFD model based on the velocity and temperature predictions. In next step, from CFD analysis, identified the poor ventilation/stagnation zones using low velocity and recirculation areas close to the gas fuel components. After identifying the poor ventilation regions, a gas leak was introduced to see whether gas cloud volume is within the ISO 21789 – 2009 limits. From gas leak analysis results, enclosure outlet IR detector settings were decided and implemented to monitor the gas leak amount and feedback to control system in the form of ALARM/SHUTDOWN so that Gas Turbine operates safely.
Experimental Investigation and Optimal Design on the Film Cooling Performance of Fan-Shaped Hole With Vortex Generator Fed by Crossflow
Authors: Wang Jie , Zhang Chao , Liu Xuebin , Song Liming , Li Jun , Feng Zhenping 
Published: September 2021

Abstract
Aiming at investigating the effects of crossflow and vortex generator on film cooling characteristics of fan-shaped hole, the film cooling performance was measured experimentally by infrared camera. The blowing ratio is fixed at 0.5 and 1.5. The Reynolds number of the mainstream based on the hole diameter remains at 7000 and the inlet Reynolds number of crossflow is 40000. The experimental results show that the film cooling performance becomes better when the blowing ratio increases from 0.5 to 1.5 for each model, and the film cooling performance becomes worse under the influence of crossflow. When the blowing ratio is 1.5, the area-averaged film cooling effectiveness of the fan-shaped hole model with vortex generator decreases by 16.6% because of the influence of crossflow. The combined model always performs better compared with the model without vortex generator under all working conditions. When the blowing ratio becomes 1.5, under the influence of crossflow, the area-averaged film cooling effectiveness of the combined model could increase by 14.8%, compared with the model without vortex generator. To further improve the film cooling performance, the global optimization algorithm based on the Kriging method and the CFD technology are coupled to optimize the combined model under crossflow condition at the high blowing ratio, and the optimized design is verified by experiments. The experimental results show that the area-averaged film cooling effectiveness of the optimized design increases by 17.8% compared with the reference model.
Forced Response Excitation of a Compressor Stator Owing to Shock Wave Induced by Adjacent Rotor Blade
Authors: Miura Toshimasa , Sakai Naoto , Kanazawa Naoki , Nakayama Kentaro 
Published: September 2021

Abstract
The accurate prediction of high cycle fatigue (HCF) is becoming one of the key technologies in the design process of state-of-the-art axial compressors. If they are not properly designed, both rotor blades and stator vanes can be damaged. There are two main factors to cause HCF. One is low engine order (LEO) and the other is high engine order (HEO) excitation by fluid force associated with adjacent rotor-stator interaction. For the front stages of axial compressors for power generations and aero engines, the inlet Mach number of a rotor tip typically exceeds the speed of sound and strong shock waves tend to be induced. This can be the source of HEO excitation fluid force, and adjacent stator vanes are sometimes severely damaged. Thus, the aim of this study is to establish an efficient method for predicting the vibration response in this type of problem with high accuracy. To achieve this, numerical investigations are carried out by one-way fluid structure interaction (FSI) simulation. To validate the accuracy of FSI simulation, experiments are also conducted using a gas turbine engine for power generation. In the experiment, the vibration level is measured with strain gauges mounted on the surface of stator vanes and the data are compared with the predicted results.
In the first part of the study, efficient prediction methods of excitation fluid force on the stator vane are investigated by time transformation (TT) and harmonic balance (HB) methods. Their accuracies are evaluated by comparing the results with those calculated by transient rotor stator (TRS) simulation whose pitch ratio is one between rotor and stator computational domains. It is found that the TT method can accurately predict the excitation fluid force with lower computation load even when there are pitch differences between rotor and stator regions.
In the second part of the study, forced response analyses are carried out using the excitation fluid force obtained in the unsteady flow simulation. To obtain the total damping of the system, both hammering test and flutter simulations are carried out. Computed results are validated with experimental data and it is found that the predicted vibration level is in good agreement with experimental results.
Through this study, the effectiveness of one-way FSI simulation is confirmed for this type of forced response prediction. By utilizing the combination of efficient unsteady computational fluid dynamics (CFD) methods and harmonic response analysis, vibration amplitude can be predicted accurately and efficiently.
Forced Response Excitation due to the Stator Vanes of Two and Three Compressor Stages Away
Authors: Miura Toshimasa , Sakai Naoto , Kanazawa Naoki , Nakayama Kentaro 
Published: September 2021

Abstract
State-of-the-art axial compressors of gas turbines employed in power generation plants and aero engines should have both high efficiency and small footprint. Thus, in many cases, axial compressors are designed to have thin rotor blades and stator vanes with short axial distances, and are driven at high rotational speed. Recently, problems of high cycle fatigue (HCF) associated with forced response excitation have gradually increased as a result of these trends. Rotor blade fatigue can be caused not only by the wake and potential effect of the adjacent stator vane, but also by the stator vanes of two, three or four compressor stages away. Thus, accurate prediction and suppression method of them under the resonance condition are necessary in the design process. Concerning the forced response excitation associated with the adjacent stator vanes, there are many previous studies on simulating the vibration by fluid structure interaction (FSI) simulation. In these studies, the aerodynamic force acting on the blade is simulated by an efficient unsteady computational fluid dynamics (CFD) method such as the nonlinear harmonic (NLH) method. These methods can be available in commercial CFD solvers and can significantly reduce computational cost. However, there are few examples of the problems associated with the stator vanes from two and three compressor stages away and no efficient simulation method is available. In this study, the problem of rotor blade vibration caused by the stator vanes of two and three compressor stages away is studied. Ways to accurately predict and effectively control the vibration are also investigated.
In the first part of the study, one-way FSI simulation is carried out using a full annulus CFD model. To validate the accuracy of the simulation, experiments are also conducted using a gas turbine test facility. The vibration level of the blade is measured using a blade tip timing (BTT) measurement system and the obtained results are compared with the simulated data. It is found that one-way FSI simulation can accurately predict the order of the vibration level.
In the second part of the study, a method of controlling the forced response excitation is investigated by optimizing the clocking of the stator vanes. It is confirmed that by controlling the clocking of the stator vanes, the vibration amplitude can be effectively suppressed without reducing the compressor performance.
Through this study, ways to evaluate and control the unsteady pressure force and vibration response of the rotor blade are validated. By optimizing the clocking of stator vanes, the blade vibration level can be effectively reduced.
Rotor-Blade Interaction During Blade Resonance Drive-Through
Authors: Grein Roland , Ehehalt Ulrich , Siewert Christian , Kill Norbert 
Published: September 2021

Abstract
In the future energy landscape, combined cycle power plants will increasingly take the role of providing balancing power for fluctuating renewable energy sources due to their high availability and fast start-up times. This implies more frequent cycling, a larger number of speed cycles and thus new challenges for plant design and operation. One of these challenges is a potential increase of cyclic fatigue incurred by last-stage blades during start-up and coast-down. Blade vibrations might be induced by synchronous shaft vibrations when the blade resonance is excited by lateral shaft vibrations. In this paper, we report measurement results of shaft and blade vibrations observed at some Siemens Energy steam turbines. Apart from the expected increase of blade vibrations when the double rotating speed crosses the blade resonance, a distinctive dip of shaft vibrations at the low-pressure turbine bearings is observed. We argue that this phenomenon is likely related to the aforementioned interaction between blade and shaft vibrations and present a theoretical framework to describe this interaction and the observed effect.
Development and Integration of the Dual Fuel Combustion System for the MGT Gas Turbine Family
Authors: Ćosić Bernhard , Reiß Frank , Blümer Marc , Frekers Christian , Genin Franklin , Pähr Judith , Waßmer Dominik 
Published: September 2021

Abstract
Industrial gas turbines like the MGT6000 are often operated as power supply or as mechanical drives for pumps and compressors at remote locations on islands and in deserts. Moreover, small gas turbines are used in CHP applications with a high need for availability. In these applications, liquid fuels like ‘Diesel Fuel No. 2’ can be used either as main fuel or as backup fuel if natural gas is not reliably available. The MAN Gas Turbines (MGT) operate with the Advanced Can Combustion (ACC) system, which is already capable of ultra-low NOx emissions for a variety of gaseous fuels. This system has been further developed to provide dry dual fuel capability to the MGT family. In the present paper, we describe the design and detailed experimental validation process of the liquid fuel injection, and its integration into the gas turbine package.
A central lance with an integrated two-stage nozzle is employed as a liquid pilot stage, enabling ignition and start-up of the engine on liquid fuel only, without the need for any additional atomizing air. The pilot stage is continuously operated to support further the flame stabilization across the load range, whereas the bulk of the liquid fuel is injected through the premixed combustor stage. The premixed stage comprises a set of four decentralized nozzles placed at the exit of the main air swirler. These premixed nozzles are based on fluidic oscillator atomizers, wherein a rapid and effective atomization of the liquid fuel is achieved through self-induced oscillations of the liquid fuel stream.
We present results of numerical and experimental investigations performed in the course of the development process illustrating the spray, hydrodynamic, and thermal performance of the pilot injectors. Extensive testing of the burner at atmospheric and full load high-pressure conditions has been performed, before verification of the whole combustion system within full engine tests. The burner shows excellent emission performance (NOx, CO, UHC, soot) without additional water injection, while maintaining the overall natural gas performance. Soot and particle emissions, quantified via several methods, are well below legal restrictions. Furthermore, when not in liquid fuel operation, a continuous purge of the injectors based on compressor outlet (p2) air has been laid out. Generic atmospheric coking tests were conducted before verifying the purge system in full engine tests. Thereby we completely avoid the need for an additional high-pressure auxiliary compressor or demineralized water. We show the design of the fuel supply and distribution system. We designed it to allow for rapid fuel switchovers from gaseous fuel to liquid fuel, and for sharp load jumps. Finally, we discuss the integration of the dual fuel system into the standard gas turbine package of the MGT6000 in detail.
Intercooler Parametric Analysis for the IRA Engine Cycle Performance Augmentation
Authors: Alexiou Emmanouil , Vlahostergios Zinon , Salpingidou Christina , Donus Fabian , Misirlis Dimitrios , Yakinthos Kyros 
Published: September 2021

Abstract
Aiming in the direction of designing high efficiency aircraft engines, various concepts have been developed in recent years, among which is the concept of the intercooled and recuperative aero engine (IRA engine). This concept is based on the use of a system of heat exchangers (recuperator) mounted inside the hot-gas exhaust nozzle, as well as a system of heat exchangers (intercooler) mounted between the intermittent-pressure compressor (IPC) and the high-pressure compressor (HPC) compressor modules. Through the operation of the system of recuperator module, the heat from the exhaust gas, downstream the LP turbine of the aero engine is driven back to the combustion chamber. Thus, the preheated air enters the engine combustion chamber with increased enthalpy, providing higher combustion efficiency and consequently reduced thrust specific fuel consumption (TSFC) and low-level emissions. Additionally, by integrating the intercooler module between the compressor stages of the aero engine, the compressed air is cooled, leading to less required compression work to reach the compressor target pressure and significant improvements can be achieved in the overall engine efficiency and the specific fuel consumption hence, contributing to the reduction of CO2 and NOx emissions.
The present work is focused on the optimization of the performance characteristics of an intercooler specifically designed for aero engine applications, working cooperatively with a novel design recuperator module targeting the reduction of specific fuel consumption and taking into consideration aero engine geometrical constraints and limitations for two separate operating scenarios. The intercooler design was based on the elliptically profiled tubular heat exchanger which was developed and invented by MTU Aero Engines AG. For the specific fuel consumption investigations, the Intercooled Recuperated Aero engine cycle that combines both intercooling and recuperation was considered. The optimization was performed with the development of an intercooler surrogate model, capable to incorporate major geometrical features. A large number of intercooler design scenarios was assessed, in which additional design criteria and constraints were applied. Thus, a significantly large intercooler design space was covered resulting to the identification of feasible designs providing beneficial effect on the Intercooled Recuperated Aero engine performance leading to reduced specific fuel consumption, reduced weight and extended aircraft range.
An Approach to Measure Total-Head in Wakes and Near End Walls at High Fogging Conditions
Authors: Harbeck Janneck , Geist Silvio , Schatz Markus 
Published: September 2021

Abstract
Evaporation cooling increases gas turbine power output. Experimental results suggest an 8% increase of power when 1% of the overall mass flow is added via water droplets injected upstream of the compressor. However, water injection has an impact on the flow field, which requires experimental research involving probe measurements in the droplet-laden flow as well as reliable monitoring during operation, as the volumetric flow rate throughout the stages changes notably and deviates from (dry) design parameters. Measuring with a conventional pressure probe in two-phase flows is challenging because the droplet-laden flow can clog the pressure taps, thus effectively separating the sensor from the measurement location. This paper presents a consistent approach to measure stagnation pressure in a droplet-laden flow field. The probe was purged constantly to prevent droplets from clogging the tubing. The recorded pressure is then corrected using a transfer function to account for the purging pressure offset. A detailed description of how to obtain this function is given within the paper. With this setup, the flow field downstream of a blade cascade was measured at several water mass fractions and spray characteristics. The pressure measurements are compared with the usual LDA/PDA measurements in the wake of the cascade. Based on the test results, an evaluation of the change of total-head loss due to water injection and evaporation compared to dry operation can be performed.
A Novel LES-Based Process for NOx Emission Assessment in a Premixed Swirl Stabilized Combustion System
Authors: Meloni R. , Andreini A. , Nassini P. C. 
Published: September 2021

Abstract
This paper presents a new CFD approach for the assessment of the NOx emission. The methodology is validated against the experimental data of a heavy-duty gas turbine annular combustor. Since the NOx formation involves time scales that are different from the fuel oxidation time, the present work defines the transport equation source terms for NOx on the basis of a dedicate NOx-Damköhler number. The latter parameter allows to properly distinguish the “in-flame” contribution from the “post-flame” one. While the former is a mix of several mechanisms (prompt, N2O-pathway thermal), the latter is dominated by the thermal contribution.
The validation phase is developed in a Large-Eddy Simulation (LES) framework where the Extended Turbulent Flame Speed model is implemented to consider the influence of both heat loss and strain rate on the progress variable source term. The accuracy of the model against the most important operability parameters of the combustor is verified. A strong focus on the fuel composition effect onto NOx is presented as well.
For any simulated operating condition, the present methodology is able to provide a limited percentage error if compared with the data, considering also different combustion regimes. Leveraging this alignment, the last portion of the paper is dedicated to a detailed post processing highlighting the role of some key factors on to NOx formation. In particular, the focus will be dedicated to the impact of the fuel gas composition and the pilot split.
Investigation on the Robustness of Rotor/Stator Contact Interactions With Respect to Small Mistuning
Authors: Nyssen Florence , Batailly Alain 
Published: September 2021

Abstract
In this work, the impact of small mistuning on rotor/stator contact interactions is investigated. First, a detailed study of a rotor/stator interaction between the first bending modes and the second engine order is presented in the tuned case. Then, a numerical investigation on the effect of mistuning on the studied rotor/stator contact interaction is carried out. In particular, a stochastic analysis is performed to evaluate the robustness of the interaction with respect to the mistuning level. Simulations are conducted using a reduced order model (ROM) of an industrial bladed disk that combines both physical degrees of freedom (along blades tip for contact treatment) and modal coordinates. Mistuning is introduced in the tuned ROM by means of a modified version of the component mode mistuning method that allows to keep physical degrees of freedom within the reduced basis. Nonlinear amplification factors, i.e. the amplification factors in the context of contact nonlinearities, are compared with their linear counterparts, the latter are computed using a linear forcing on each blade using a two nodal diameters traveling wave excitation on the mistuned and the tuned bladed disk. The comparison between the linear and nonlinear amplification factor for each sample highlights that no correlation exists between a mistuning pattern leading to high amplifications in a linear context or when contact nonlinearities are taken into account. Therefore, dedicated analyses on the effect of mistuning should be undertaken with contact nonlinearities considerations at the design stage especially if intentional mistuning is considered.