bluuebunny/crossref_metadata_2025_split huggingface dataset:
Next Generation Turbine Testing at DLR
Authors: Rehder Hans-Jürgen , Pahs Andreas , Bittner Martin , Kocian Frank 
Published: August 2017

Axial turbines for aircraft engines and power plants have reached a very high level of development. Further improvements, in particular in terms of higher efficiency and reduced number of blades and stages, resulting in higher loads, are possible, but can only be achieved through a better understanding of the flow parameters and a closer connection between experiment and numerical design and simulation. An analysis of future demands from the industry and existing turbine research rigs shows that there appears a need for a powerful turbine test rig for aerodynamic experiments.
This paper deals with the development and built up of a new so called Next Generation Turbine Test Facility (NG-Turb) at the German Aerospace Center (DLR) in Göttingen. The NG-Turb is a closed-circuit, continuously running facility for aerodynamic turbine investigations, allowing independent variation of engine relevant Mach and Reynolds numbers. The flow medium (dry air) is driven by a 4-stage radial gear compressor with a high pressure ratio and a wide inlet volume flow range. In a first stage the NG-Turb test section will allow investigations on single shaft turbines up to 2½ stages. In a further expansion stage the NG-Turb will be equipped with a second independent shaft system, then enabling experiments with configurations of high and low (or intermediate) pressure turbines and in particular offering the possibility for investigations at counter rotating turbines. Secondary air for cooling investigations can be provided by auxiliary screw compressors. Mass flow through the Turbine is determined redundantly with an uncertainty of about ±0.3%, using well calibrated Venturi nozzles upstream and downstream of the test section.
The operation concept and main design features of the NG-Turb will be described and an overview of the applied standard measurement and data acquisition technics capturing efficiency, traverse data etc. will be given. Thermodynamic cycle calculations have been performed in order to simulate the flow circuit of the NG-Turb and to access whether turbine operating points can be driven within the performance map of the compressor system. Finally the calibration procedure for the Venturi nozzles, which has been conducted during the commissioning phase of the NG-Turb by applying a special calibration test section, is explained and some results will be shown.
Experimental Investigation With Optical Diagnostics of a Lean-Premixed Aero-Engine Injection System Under Relevant Operating Conditions
Authors: Malbois P. , Salaun E. , Frindt F. , Cabot G. , Renou B. , Grisch F. , Bouheraoua L. , Verdier H. , Richard S. 
Published: August 2017

A Lean-Premixed (LP) aero-engine injection system was experimentally studied using optically-based measurements. Experiments were conducted under relevant operating conditions up to 1.38 MPa and using commercial kerosene as fuel.
First of all, the structure of the reaction zone and the flame length into the combustion chamber have been studied with CH* chemiluminescence. It is observed from the data measurements that combustion can produce two types of flames, a V-shaped flame in which combustion is stabilized a few mm downstream from the injector and a tulip flame in which combustion is developing inside the injection system. The flame is found to be shorter and more confined when increasing the pressure. To complement this study, experiments were also performed using the OH-PLIF measurement technique. Data processing of the absorption of OH fluorescence signals along the laser propagation allowed the determination of the absolute distribution of OH concentration without any calibration of the OH fluorescence signals. The obtained values are in agreement with estimated premixed adiabatic chemical equilibrium results. Furthermore, the flame front location and its structure were captured from gradient-based filtering operations on OH-PLIF signals. Finally, pollutant emissions were also measured with an exhaust gas sampling probe positioned downstream from the combustor outlet. It has been found that NOx emission increases with Fuel Air Ratio (FAR) and pressure whereas CO exhibits an inverse trend.
An Investigation of Combustion Properties of Butanol and its Potential for Power Generation
Authors: Methling Torsten , Richter Sandra , Kathrotia Trupti , Braun-Unkhoff Marina , Naumann Clemens , Riedel Uwe 
Published: August 2017

Over the last years, global concerns about energy security and climate change have resulted in many efforts focusing on the potential utilization of non-petroleum-based, i.e. bio-derived, fuels. In this context, n-butanol has recently received high attention because it can be produced sustainably. A comprehensive knowledge about its combustion properties is inevitable to ensure an efficient and smart use of n-butanol if selected as a future energy carrier.
In the present work, two major combustion characteristics, here laminar flame speeds applying the cone-angle method and ignition delay times applying the shock tube technique, have been studied, experimentally and by modeling exploiting detailed chemical kinetic reaction models, at ambient and elevated pressures. The in-house reaction model was constructed applying the RMG-method. A linear transformation method recently developed, linTM, was exploited to generate a reduced reaction model needed for an efficient, comprehensive parametric study of the combustion behavior of n-butanol/hydrocarbon mixtures.
All experimental data were found to agree with the model predictions of the in-house reaction model, for all temperatures, pressures, and fuel-air ratios. On the other hand, calculations using reaction models from the open literature mostly overpredict the measured ignition delay times by about a factor of two. The results are compared to those of ethanol, with ignition delay times very similar and laminar flame speeds of n-butanol slightly lower, at atmospheric pressure.
The Effect of Turning Angle on the Loss Generation of LP Turbines
Authors: Torre Diego , Garcia-Valdecasas Guillermo , Cadrecha David 
Published: August 2017

The effect of turning angle on the loss generation of Low Pressure (LP) Turbines has been investigated experimentally in a couple of turbine high-speed rigs. Both rigs consisted of a rotor-stator configuration. All the airfoils are high lift and high aspect ratio blades that are characteristic of state of the art LP Turbines.
Both rigs are identical with exception of the stator. Therefore, two sets of stators have been manufactured and tested. The aerodynamic shape of both stators has been designed in order to achieve the same spanwise distribution of Cp (Pressure coefficient) over the airfoil surface, each one to its corresponding turning angles. Exit angle in both stators is the same. Therefore the change in turning is obtained by a different inlet angle.
The aim of this experiment is to obtain the sensitivity of profile and endwall losses to turning angle by means of a back-to-back comparison between both sets of airfoils. Because the two sets of stators maintain the same pressure coefficient distribution, Reynolds number and Mach number, each one to its corresponding velocity triangles, one can state that the results are only affected by the turning angle.
Experimental results are presented and compared in terms of area average, radial pitchwise average distributions and exit plane contours of total pressure losses. CFD simulations for the two sets of stators are also presented and compared with the experimental results.
Analysis of a Turbine Bladed Disk With Structural and Aerodynamic Mistuning
Authors: Franz Dimitri , Salles Loic , Stapelfeldt Sina 
Published: August 2017

In this paper the effects of mistuning on the flutter stability of a turbine blade are analysed. Two types of mistuning are considered, frequency mistuning and aerodynamic mistuning. The study concentrates on the the first family of modes (1F, first flap) as the blade fluttered in this mode during test. For the frequency mistuning analysis, the 1F frequency is varied around the annulus but the 1F mode shapes remain the same for all the blades. The mistuning analyses are performed by using a reduced order model (ROM) based on an eigenvalue analysis of the linearized modal aeroelastic system with the aerodynamic matrix calculated from the aerodynamic influence coefficients. The influence coefficients required for this algorithm are obtained from a three-dimensional, non-linear aeroelastic solver (AU3D) by shaking one blade in the datum (tuned) frequency and mode and recording aerodynamic forces on the other blades in the assembly. After the ROM is validated against the non-linear method for the tuned case, it is used for the mistuning and mis-staggering study as time-domain computations of such cases are very time consuming.
The results of this paper indicate that, frequency mistuning is always stabilizing but aerodynamic mistuning can be destabilizing under certain conditions. Moreover, it is shown that the effect of frequency mistuning is much higher than the one of aerodynamic asymmetries and that structural coupling limits the effects of mistuning.
Fluid-Structure Interaction Study of Large and Light Axial Fan Blade
Authors: Castorrini A. , Corsini A. , Sheard A. G. , Rispoli F. , Lamperini M. 
Published: August 2017

Numerical simulation tools are acquiring a crucial role in the virtual prototyping of new fan rotor blades. This, considering also the possibility in using new advanced materials, is opening the design capability to blades of longer, lighter and more slender structure.
On this perspective, the numerical tools must be improved in order to catch also the non-linear and coupling phenomena which were been treated until now using a weak coupling approach.
Here we present a fluid-structure interaction solver based on the finite element method, through its application to an existing fan blade. The study will show how, even in case of metal structure with little deformation, the coupling between fluid dynamics and structure dynamics can produce effects on both the fluid and the solid involved in the machine main process. The possibility to simulate directly both the aerodynamic and the effective structure response opens the way to improved design capabilities, avoiding time waste and costs due to long experimental testing campaign and over-dimensioned structures.
A Numerical Investigation of the Effect of Inlet Preswirl Ratio on Rotordynamic Characteristics of Labyrinth Seal
Authors: Tsukuda Tomohiko , Hirano Toshio , Watson Cori , Morgan Neal R. , Weaver Brian K. , Wood Houston G. 
Published: August 2017

Full three-dimensional CFD simulations are carried out using ANSYS CFX to obtain the detailed flow field and to estimate the rotordynamic coefficients of a labyrinth seal for various inlet swirl ratios.
Flow fields in the labyrinth seal with the eccentricity of the rotor are observed in detail and the detailed mechanisms that increase the destabilizing forces at high inlet swirl ratios are discussed based on the fluid governing equations associated with the flow fields. By evaluating the contributions from each term of the governing equation to cross coupled force, it is found that circumferential velocity and circumferential distribution of axial mass flow rate play key roles in generating cross coupled forces. In the case that circumferential velocity is high and decreases along the axial direction, all contributions from each term are positive cross coupled force. On the other hand, in the case that circumferential velocity is low and increases along the axial direction, one contribution is positive but the other is negative. Therefore, cross coupled force can be negative in the local chamber depending on the balance even if circumferential velocity is positive.
CFD predictions of cross coupled stiffness coefficients and direct damping coefficients show better agreement with experimental results than a bulk flow model does by considering the force on the rotor in the inlet region. Cross coupled stiffness coefficients derived from the force on the rotor in the seal section agree well with those of the bulk flow model.
Numerical Investigation of Optimized Arrangements for Effusion Cooling in Gas Turbine Combustor Applications
Authors: Mazzei L. , Puggelli S. , Andreini A. , Facchini B. 
Published: August 2017

The high cooling performance and the capability of providing thermo-acoustic damping are increasing the application of effusion cooling in lean burn aero-engine combustors. The numerical characterization through Computational Fluid Dynamics (CFD) has gained strong interest, however standard Reynolds Average Navier-Stokes (RANS) techniques are not capable of providing high fidelity predictions in the presence of swirling flows interacting with the cooling system. The exploitation of Large Eddy Simulation (LES) would represent the ideal solution, but the high spatial resolution required in the near-wall region, together with the well-known issues related to an accurate specification of turbulent boundary conditions at the inlets, still represent a critical challenge for its extensive use with realistic conditions in terms of Reynolds number and geometrical complexity. Therefore different scale-resolving models such as Scale Adaptive Simulation (SAS) and Detached Eddy Simulation (DES) are gaining popularity due to the promising results highlighted.
At this purpose, a SAS approach was employed in this work to quantify the film coverage offered by different effusion cooling schemes in the presence of a swirler, highly unsteady flow field. The main goal is determine if well-known design practices derived from investigations carried out on flat plates with uniform mainstream conditions may be confirmed also under realistic flow conditions. In particular, the geometrical parameters evaluated in the work are the inclination angle, the compound angle and the pattern of the perforation. The results clearly highlight how a reduction of the inclination angle is able to keep coolant more attached to the wall, whereas the application of a compound angle increases the turbulent diffusion in the lateral direction, ultimately increasing coolant protection.
Small Aircraft Turbine Noise From Combustion of Synthetic Kerosene Fuels
Authors: Soloiu Valentin , Knowles Aliyah , Moncada Jose , Simons Emerald , Muinos Martin , Ngo Huong Kim 
Published: August 2017

In this paper the use of alternative fuels — synthetic kerosene based — were investigated in a small aircraft gas turbine engine to determine their sound and vibrations signature at Georgia Southern University’s Aerospace Engine Laboratory. Three types of fuels were used: a natural gas, a coal derived synthetic kerosene and Jet-A as a reference fuel. The alternative fuels are Fischer-Tropsch process fuels. Synthetic fuels are attractive in the aviation industry because of their potential for reducing energy dependence and the growing need for higher efficiencies, while reducing emissions.
The research SR-30 gas turbine was used to evaluate combustion noise from the selected fuels. The turbine can operate at a maximum speed of 80,000 rpm, produce a maximum thrust of 40 lbf, has a pressure ratio of 3.4 to 1, and a specific fuel consumption of 1.22 lbfuel/thrust per hour. The measurement transducers were state of the art Brüel & Kjaer ¼ inch microphone and a triaxial accelerometer which were interfaced with the analysis software, Brüel & Kjaer Pulse 21. Data was taken at 70,000 rpm for a time span of five minutes at stabilized conditions. One-third octave analysis indicated highest sound difference between the fuels at 400 Hz, and a more pure sound level was obtained. The difference for Jet A was as much as 6 dBA higher for exhaust measurement at 400 Hz, and for FT-NG the exhaust had a higher decibel reading from the exhaust side by as much as 4.4 dBA at the 400 Hz frequency, and FT-CG had as much as 7.3 dBA difference at 315 Hz. The sound from the combustion of these fuels produced the differences of sound when the positions of the microphones changed. However, with this new introduction of sound measurement locations and angles, the combustion differences are still distinct and show a more in depth view of the sound quality that is being received by the microphone.
Novel Centrifugal Compressor Architecture for Wide-Range Operation: A Feasibility Assessment
Authors: Krivitzky Eric M. , Larosiliere Louis M. 
Published: August 2017

Turbocharger compressor performance plays a critical role in the ability of advanced Internal Combustion Engines (ICE) to meet the required fuel economy and drivability targets. Increased use of exhaust gas recirculation (EGR) combined with engine downsizing has pushed compressor operation towards — and often beyond — the stability boundary. However, certain applications and market trends require that no compromise be made to the rated power conditions. This has led to a highly disparate set of requirements for a single turbocharger system resulting in much of the compressor map, including the highest-efficiency area, unused or underutilized. A large percentage of the drive cycle is spent operating the compressor at low flow rates and low pressure ratios, near the compressor surge line, in an area of low efficiency. Compromises in efficiency in critical regions of engine operation result from balancing the disparate requirements.
A current approach to meeting these disparate flow targets is the use of two turbochargers in series that are sized such that the operating compressor efficiency is markedly improved. This paper introduces a novel, hybrid single-stage compressor architecture which aerodynamically matches the functions of a series sequential dual turbocharger compression system. The use of a variable flow rate inducer bypass can provide a throttleable work-adding alternate flowpath for high-flow conditions, essentially emulating an efficient large compressor when the bypass is open and a small compressor when the bypass is closed. Using the variable bypass, the low-flow performance improves through an aerodynamically regulated inducer that is tailored to this flow regime. An engineering feasibility assessment supported by CFD, vector diagram analysis, and structural FEA suggest a substantial potential for improved performance across a wide flow range with this novel architecture.
Testing of a Novel Post Combustion Acid Removal Process for the Direct-Fired, Oxy-Combustion Allam Cycle Power Generation System
Authors: Lu Xijia , Martin Scott , McGroddy Mike , Swanson Mike , Stanislowski Josh , Laumb Jason D. 
Published: August 2017

The Allam Cycle is a high performance oxy-fuel, supercritical CO2 power cycle that offers significant benefits over traditional fossil and hydrocarbon fuel-based power generation systems. A major benefit arises in the elimination of costly pre-combustion acid gas removal (AGR) for sulfur-(SOx) and nitrogen-based (NOx) impurities by utilizing a novel downstream cleanup process that utilizes NOx first as a gas phase catalyst to effect SOx oxidation, followed by NOx removal. The basic reactions required for this process, which have been well-demonstrated in several facilities for the cleanup of exhaust gasses, ultimately convert SOx and NOx species to sulfuric, nitric and nitrous acids for removal from the supercritical CO2 stream. The process results in simplified and significantly lower cost removal of these species and utilizes conditions inherent to the Allam Cycle that are ideally suited to facilitate this process.
8 Rivers Capital and the Energy & Environmental Research Center (EERC), supported by the state of North Dakota, the US Department of Energy (DOE) and an Industrial consortium from the State of North Dakota, are currently working together to test and optimize this novel impurity removal process for pressurized, semi-closed supercritical CO2 cycles, such as the Allam Cycle. Both reaction kinetic modeling and on-site testing have been completed. Initial results show that both SOx and NOx can be substantially removed from CO2-rich exhaust gas containing excess oxygen under 20 bar operating pressure utilizing a simple packed spray column. Sensitivity of the removal rate to the concentration of oxygen and NOx was investigated. Follow-on work will focus on system optimization to improve removal efficiency and removal control, to minimize metallurgy and corrosion risks from handling concentrated acids, and to reduce overall CAPX/OPEX of the system.
Characterization of
cis
-Acting RNA Elements of Zika Virus by Using a Self-Splicing Ribozyme-Dependent Infectious Clone
Authors: Liu Zhong-Yu , Yu Jiu-Yang , Huang Xing-Yao , Fan Hang , Li Xiao-Feng , Deng Yong-Qiang , Ji Xue , Cheng Meng-Li , Ye Qing , Zhao Hui , Han Jian-Feng , An Xiao-Ping , Jiang Tao , Zhang Bo , Tong Yi-Gang , Qin Cheng-Feng 
Published: August 2017

ABSTRACT

Zika virus (ZIKV) has caused significant outbreaks and epidemics in the Americas recently, raising global concern due to its ability to cause microcephaly and other neurological complications. A stable and efficient infectious clone of ZIKV is urgently needed. However, the instability and toxicity of flavivirus cDNA clones in
Escherichia coli
hosts has hindered the development of ZIKV infectious clones. Here, using a novel self-splicing ribozyme-based strategy, we generated a stable infectious cDNA clone of a contemporary ZIKV strain imported from Venezuela to China in 2016. The constructed clone contained a modified version of the group II self-splicing intron
P.li.LSUI2
near the junction between the E and NS1 genes, which were removed from the RNA transcripts by an easy-to-establish
in vitro
splicing reaction. Transfection of the spliced RNAs into BHK-21 cells led to the production of infectious progeny virus that resembled the parental virus. Finally, potential
cis
-acting RNA elements in ZIKV genomic RNA were identified based on this novel reverse genetics system, and the critical role of 5′-SLA promoter and 5′-3′ cyclization sequences were characterized by a combination of different assays. Our results provide another stable and reliable reverse genetics system for ZIKV that will help study ZIKV infection and pathogenesis, and the novel self-splicing intron-based strategy could be further expanded for the construction of infectious clones from other emerging and reemerging flaviviruses.

IMPORTANCE
The ongoing Zika virus (ZIKV) outbreaks have drawn global concern due to the unexpected causal link to fetus microcephaly and other severe neurological complications. The infectious cDNA clones of ZIKV are critical for the research community to study the virus, understand the disease, and inform vaccine design and antiviral screening. A panel of existing technologies have been utilized to develop ZIKV infectious clones. Here, we successfully generated a stable infectious clone of a 2016 ZIKV strain using a novel self-splicing ribozyme-based technology that abolished the potential toxicity of ZIKV cDNA clones to the
E. coli
host. Moreover, two crucial
cis
-acting replication elements (5′-SLA and 5′-CS) of ZIKV were first identified using this novel reverse genetics system. This novel self-splicing ribozyme-based reverse genetics platform will be widely utilized in future ZIKV studies and provide insight for the development of infectious clones of other emerging viruses.