bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of the Effect of Reynolds Number on the Efficiency of Single-Stage Axial Fans
Authors: Masi Massimo , Castegnaro Stefano , Lazzaretto Andrea
Published: August 2018

Uncertainties surrounding the influence of Reynolds number on the performance of air handling turbomachines are as old as the study of turbomachinery fluid dynamics. In particular, all low-speed turbomachines and most axial-flow fans feature Reynolds numbers that are often lower than the critical value, above which the literature states a limited dependency of blades cascade aerodynamics on Reynolds number. Testing standards already account for this well-known issue, which arises mainly in the case of geometrically similar fans of different size and/or operating conditions.

On the other hand, one of the main practical issues in the design of low-speed machines is the disagreement among the most authoritative sources on the value of the critical Reynolds number for axial fans. The many definitions of Reynolds number, which are suited to either fan design purposes or fan performance assessment, introduce additional problems, as the corresponding values may differ by orders of magnitude depending on the chosen definition.

A less debated issue deals with the effect of Reynolds number on global performance and efficiency parameters for different axial-flow fan configurations.

This paper reports pressure and efficiency data measured at several rotational speeds of four axial fans that feature different configurations, hub-to-tip ratios, sizes and surface finishes. In particular, the tests consider two 315mm and one 630mm tube-axial fans, and one 800mm vane-axial fan with preswirler blading. Data on two vane-axial fans with straightener, and one preswirler-rotor-stator stage, available in the literature, widen the discussion on the Reynolds number effect on the entire category of single-stage axial fans.
Evaluation of Wire Electrochemical Machining With Rotating Electrode for the Manufacture of Fir Tree Slots
Authors: Klocke F. , Herrig T. , Klink A.
Published: August 2018

Components with best surface integrities — without any white layer or mechanically damaged rim zones — and regardless of mechanical properties of the material can be produced with electrochemical machining (ECM). Wire ECM combines the outstanding advantages of the ECM working principle with the kinematic of wire electrical discharge machining (wire EDM). A task-specific tool design — such as for classical sinking ECM — is not required for cutting 2.5-dimensional geometries like fir tree slots in turbine discs. Established manufacturing technologies for fir trees are broaching and recently wire EDM. However, high requirements on surface integrity of these turbine parts afford cost intensive finishing processes. Thus, wire ECM could be an attractive cost efficient alternative manufacturing process.

Due to an insufficient flushing concept, a process development of wire ECM for fir tree slots with relevant disc heights failed in the past. A combination of an axial flushing with rotating structured electrode provides a promising approach to meet these challenges.

Therefore, this paper presents investigations of cutting Inconel 718 direct-aged using the new flushing principle. Workpieces with heights up to 40 mm are machined, which is comparable to a low pressure turbine disc height. Reachable feed rates respectively cutting rates are presented. Due to the process specific edge rounding, the formation of the leading edges is examined. Finally, the evolving surface integrities with the help of surface roughness, cross sections and residual stresses are investigated and discussed.
Effect of Chemical Composition of Syngas on Combustion Dynamics Inside Bluff-Body Type Turbulent Syngas Combustor
Authors: Baraiya Nikhil Ashokbhai , Chakravarthy Satynarayanan R.
Published: August 2018

In the present work, the chemical composition of syngas is changed by varying the H2/CO ratio, to map the change in the acoustic behavior of a bluff-body combustor. It was observed that with increase in hydrogen concentration in the syngas mixture, the frequency shifts to higher modes and the flame structures changes. The flame oscillations are mapped by means of simultaneous high-speed OH* and CO2* chemiluminescence imaging along with dynamic pressure measurement. The plots of spatial distribution of OH* and CO2* intensity are used to understand change in flame structure with change in chemical composition and also to help in understanding the kinetics affecting acoustic behavior of the flame. The change in flow structures with change in chemical composition of fuel is studied by simultaneous high-speed PIV, OH* chemiluminescence and dynamic pressure measurements.
LCF Initiated - HCF Propagated Crack Life Estimation of Gas Turbine Bolts
Authors: Paspulati Amit K. , Veluru Krishna , Akki Kashinath , Khattar Rohit , Bosu Sudeep , Narasimhachary Santosh
Published: August 2018

This paper discusses the methodology to calculate high cycle fatigue (HCF) crack propagation life of gas turbine bolts and compares two dimensional (2D) HCF crack propagation life to three dimensional (3D) HCF crack propagation life. Gas turbine bolts when exposed to fatigue loading are prone to crack initiation and propagation (structural failure) during operation. In such cases cracks mostly are initiated by low cycle fatigue (LCF) and propagated by HCF. Therefore in current illustration the authors have evaluated crack propagation primarily initiated by low cycle fatigue and propagated by high cycle fatigue. 2D and 3D fracture methodology approaches had been used for analytical evaluation. The authors conclude on the efficacy of both the methods based on the data from the field. The coupling joint bolts located in the engine mid-section, which are used to join compressor rotor with turbine rotor are being considered for crack evaluation studies. The coupling bolts located in mid-section are primarily loaded by high axial bolt pre-loads needed to keep the joint intact, as well as loaded in bending due to rotor gravity sag. The crack propagation life is evaluated and validated with field data using cracked bolt specimen from the field.
Exergoeconomic Analysis of a Triple-Level Pressure Combined Cycle With Supplementary Firing
Authors: Torres González Edgar Vicente , Lugo Leyte Raúl , Lugo Méndez Helen Denise , Salazar Pereyra Martín , Ambriz García Juan José
Published: August 2018

One of the ways to make an efficient use of energy resources is to generate power from combined cycle power plants. Besides, the implementation of supplementary firing in a combined cycle plant helps to increase its generated power. In addition, the exergoeconomic analysis is pursued by 1) carrying out a systematic approach, based on the Fuel-Product methodology, in each component of the system; and 2) generating a set of equations, which allows compute the exergetic and exergoeconomic costs of each flow. For this analysis, the environmental conditions correspond 25 °C, 1.013 bar and 45 % relative humidity. Therefore, in this work an exergoeconomic analysis of a triple-level pressure combined cycle with a 2 × 2 × 1 arrangement with and without supplementary firing is performed, so the combined cycle with supplementary firing generates 484.62 MW and has a power relation between the gas turbine cycle and steam turbine cycle of 1.35:1. Meanwhile, the combined cycle without supplementary firing generates 427.25 MW with a power ratio of the gas turbine cycle and steam turbine cycle of 1.87:1.
Assessment of Flow Control Strategies for Improving Centrifugal Compressor Efficiency
Authors: Ashrafi Farzad , Vo Huu Duc
Published: August 2018

This paper describes a preliminary assessment of two flow control strategies for improving the adiabatic efficiency of centrifugal compressors for aero-engine applications. Given that the diffuser loss and pressure recovery play and important role in centrifugal stage efficiency, a centrifugal compressor with “fishtail” pipe diffusers is chosen for the study. This type of diffuser, which is among the most efficient diffusers, turns the flow directly from a high-swirl radial flow toward an axial flow, thus providing a smaller outer compressor diameter. As such, they are ideal for aero-propulsion applications. Past researches indicate that the diffuser performance is very much dependent on the impeller exit flow (diffuser inlet flow) uniformity. Two passive candidate flow control strategies that could improve impeller exit flow uniformity are proposed, namely slots casing treatment near the impeller radial bend and flow recirculation with injection in this area. They are aimed at attenuating the significant low-momentum region near the shroud that grows from the radial bend to the impeller exit. Iterations of the two proposed flow control strategies were evaluated through unsteady RANS CFD simulations on a low-speed centrifugal compressor stage with fishtail pipe diffusers. A comparison in terms of component and stage performance as well as an analysis of the flow field was carried out from the simulation results of the early iterations of the two flow control strategies. They show that both strategies have good potential for improving impeller exit flow uniformity and reducing losses in the fishtail pipe diffusers. However, the casing treatment strategy is more promising for improving stage efficiency due to lower penalty in impeller efficiency.
Optimal Placement and Sizing of Piezoelectric Material for Multiple-Mode Vibration Reduction
Authors: Kelley Christopher R. , Kauffman Jeffrey L.
Published: August 2018

Modern turbomachinery blades have extremely low inherent damping, which can lead to high transient vibrations and failure through high-cycle fatigue. Recent research seeks methods to reduce vibration with minimal effect on the weight and aerodynamic efficiency of the blade. Smart materials present an interesting means to augment the mechanical characteristics of the blade while meeting the strict requirements of the turboma-chinery environment. In particular, piezoelectric-based vibration reduction offers the potential to semi-actively reduce vibration while simultaneously harvesting enough energy to power the implementation. The placement and size of the piezoelectric material is critical to the vibration reduction capabilities of the system. Furthermore, the implementation should target multiple vibration modes. This work develops a procedure to optimize electromechanical coupling across multiple vibration modes for a representative turbine blade with a surface-mounted piezoelectric patch.
Continuous-Scan Phased Array Measurement Methods for Turbofan Engine Acoustic Testing
Authors: Shah Parthiv N. , White Andrew , Hensley Dan , Papamoschou Dimitri , Vold Håvard
Published: August 2018

Imaging of aeroacoustic noise sources is routinely accomplished with geometrically fixed phased arrays of microphones. Several decades of research have gone into improvement and optimization of sensor layouts, selection of basis models, and deconvolution algorithms to produce sharper and more localized images of sound-producing regions in space. This paper explores an extension to conventional phased array measurements that uses slowly, continuously moving microphone arrays with and without coupling to rigid fixed arrays to improve image quality and better describe noise mechanisms on turbofan engine sources such as jet exhausts and turbomachinery components.

Three approaches are compared in the paper: fixed receiver beamforming (FRBF), continuous-scan beamforming (CSBF), and multireference CSBF (MRCSBF). The third takes advantage of transfer function matrices formed between fixed and moving sensors to achieve effective virtual arrays with spatial density one to two orders of magnitude higher, with practical sensor budgets and scan speeds.

The MRCSBF technique produces array sidelobe rejection that approaches the theoretical array pattern of a continuous 2-D aperture. The implications of this finding are that better source localization may be achieved with conventional delay and sum (DAS) beamforming (BF) with practical sensor budgets, and that an improved starting image of the sound source can be provided to deconvolution algorithms. These findings are demonstrated on analytical and experimental examples from a low-cost rotating phased array using point sound sources, as well as linear scanning array experiments of an impinging jets point source and a near-sonic jet nozzle exhaust.
Testing of a New Turbocompressor for Supercritical Carbon Dioxide Closed Brayton Cycles
Authors: Pasch Jim , Stapp David
Published: August 2018

Sandia National Laboratories (SNL) has recently purchased a supercritical carbon dioxide (sCO2) turbocompressor that operates at 118,000 rpm, 750 °C turbine inlet temperature, and 42.9 MPa compressor discharge pressure, and is sized to pressurize the flow for a 1 MWe closed Brayton cycle. The turbocompressor is a line replaceable unit designed by Peregrine Turbine Technologies (PTT) located in Wiscasset, Maine, as part of their closed Brayton electric power genset rated at 1 MWe. Both this machine and a 6MW variant are intended for commercial applications burning a variety of aircombustible fuels including biomass materials.

Sandia purchased this turbocompressor as the first phase of a program to construct a 1 MWe commercially viable sCO2 recompression closed Brayton-cycle system. During this phase, the development platform resident at the SNL Brayton Lab was reconfigured to support testing of the PTT turbocompressor to moderate, or idle, conditions. The testing infrastructure at the Brayton Lab limited maximum pressure to 13.8 MPa. This pressure limitation consequently limited turbocompressor operations to a speed of 52,000 rpm and a turbine inlet temperature of 150 °C. While these conditions are far removed from the machine design point, they are sufficient to demonstrate a range of important features. Numerous testing objectives were identified and researched, most notably: the development of a reliable cycle bootstrapping process for a motorless turbocompressor; the demonstration of consistent start, steady state, and shutdown performance and operations; performance demonstration of the numerous internal seals and bearings designs that are new to this environment; demonstration of controllability via turbine back pressuring and turbine inlet temperature; and turbomachinery performance map validation.

This paper presents the design and development of the testing platform, the PTT turbocompressor and progress achieved on each of the objectives.
Effects of Reacting Conditions on Flow Fields in a Swirl Stabilized Lean Premixed Can Combustor
Authors: Park Suhyeon , Gadiraju Siddhartha , Pandit Jaideep , Ekkad Srinath , Liberatore Federico , Ho Yin-Hsiang , Srinivasan Ram
Published: August 2018

PIV measurements to understand the flow differences between reacting and non-reacting conditions were conducted in an optically accessible single can combustor. An industrial fuel nozzle was installed at the inlet of the test section to generate the swirl flow for flame stabilization and simulate realistic conditions of a gas turbine combustor. Five different equivalence ratios between 0.50 and 0.75 were tested with propane as fuel. Main air flow was also varied from Reynolds number from 50000 to 110000 with respect to the fuel nozzle diameter. Effect of preheating was tested by changing inlet air temperature from 23 to 200°C. The pressure at the test section was close to atmospheric condition throughout the tests.

The measurements were performed with a 2-D PIV system. Time-averaged flow velocity, vorticity and turbulent kinetic energy (TKE) were obtained from PIV data and flow structures under different conditions were compared. Swirl jet impingement location on the liner wall was determined as well to understand the impact on the liner wall. Proper orthogonal decomposition (POD) further analyzed the data to compare coherent structures in the reacting and non-reacting flows.
An Approach to Approximate the Full Strain Field of Turbofan Blades During Operation
Authors: Fu Gen , Untaroiu Alexandrina , O’Brien Walter
Published: August 2018

The measurement of the aeromechanical response of the fan blades is important to quantifying their integrity. The accurate knowledge of the response at critical locations of the structure is crucial when assessing the structural condition. A reliable and low cost measuring technique is necessary. Currently, sensors can only provide the measured data at several discrete points. A significant number of sensors may be required to fully characterize the aeromechanical response of the blades. However, the amount of instrumentation that can be placed on the structure is limited due to data acquisition system limitations, instrumentation accessibility, and the effect of the instrumentation on the measured response. From a practical stand point, it is not possible to place sensors at all the critical locations for different excitations. Therefore, development of an approach that derives the full strain field response based on a limited set of measured data is required.

In this study, the traditional model reduction method is used to expand the full strain field response of the structure by using a set of discrete measured data. Two computational models are developed and used to verify the expansion approach. The solution of the numerical model is chosen as the reference solution. In addition, the numerical model also provides the mode shapes of the structure. In the expansion approach, this information is used to develop the algorithm. First, a cantilever beam model is created. The influences of the sensor location, number of sensors and the number of modes included are analyzed using this cantilever beam model. The expanded full field response data is compared with the reference solution to evaluate the expansion procedure. The rotor 67 blade model is then used to test the expansion method. The results show that the expanded full field data is in good agreement with the calculated data. The expansion algorithm can be used for the full field strain by using the limited sets of strain data.
Influences of Non-Destructive Inspection Simulation on Fracture Risk Assessment of Additively Manufactured Turbine Engine Components
Authors: Enright Michael P. , McClung R. Craig , Sobotka James C. , Moody Jonathan P. , McFarland John , Lee Yi-Der , Gray Irving , Gray Joe
Published: August 2018

Additive manufacturing processes produce components that may introduce material anomalies at any location within a component. NDE inspection can be used to find and remove anomalies that could grow to failure during the service life, but two key inputs are required for an effective inspection: (1) the critical locations to search for anomalies, and (2) the minimum sizes of the anomalies that must be found. A new methodology is presented for probabilistic damage tolerance assessment of additively manufactured components. It consists of a new link between the DARWIN® probabilistic damage tolerance software and the XRSim X-ray NDE simulation software. DARWIN computes fracture risk and critical initial crack sizes throughout a component, providing the two key inputs that are necessary for effective NDE inspections. XRSim computes location-specific POD curves everywhere in a component, providing the key information needed to assess the influence of inspection on fracture risk reduction. The methodology is illustrated for a representative gas turbine engine component manufactured via the direct metal laser sintering process. The results can be used to optimize the effectiveness of NDE inspection of additively manufactured components.
Efficient Adjoint-Based Mesh Adaptation Applied to Turbo-Machinery Flows
Authors: Vivarelli Guglielmo , Qin Ning , Shahpar Shahrokh , Radford David
Published: August 2018

Within an industrial setting, mesh adaptation has so far found very limited use. This is, in part, due to the complexity of the geometries and flow features that are to be dealt with. However, the successful utilisation of grid modification techniques, could help engineers achieve more accurate estimates of quantities of interest quickly and efficiently. For this reason, in this paper, adjoint error mesh adaptation technology is developed and applied to steady-3D turbo-machinery solutions.

The grid modification strategy proposed comprises of a combined mesh movement and mesh refinement procedure, entirely based on errors related to the functional of interest. The node addition scheme makes use of the output to the flow adjoint solver and an interpolation to an embedded grid. The determined error is used in an edge-refinement approach developed in the in-house MeshPost software. The mesh relocation technique, instead, employs the sensitivity of the functional of interest with respect to the nodes’ coordinates to compute a Riemmannian metric. This parameter is then equi-distributed over the mesh by applying a spring-stiffness approach.
Aeromechanical Response of a Distortion Tolerant Boundary Layer Ingesting Fan
Authors: Provenza Andrew J. , Duffy Kirsten P. , Bakhle Milind A.
Published: August 2018

Boundary Layer Ingestion (BLI) is a propulsion technology being investigated at NASA by the Advanced Aircraft Transportation Technology (AATT) Program to facilitate a substantial reduction in aircraft fuel burn. In an attempt to experimentally demonstrate an increase in propulsive efficiency of a BLI engine, a first-of-its-kind sub-scale high-bypass ratio 22” titanium fan, designed to structurally withstand significant unsteady pressure loading caused by a heavily distorted axial air inflow, was built and then tested in the transonic section of the GRC 8′ × 6′ Supersonic Wind Tunnel. The vibratory responses of a subset of fan blades were measured using strain gages placed in four different blade pressure side surface locations. Response highlights include a significant response of the blade’s first resonance to engine order excitation below idle as the fan was spooled up and down. The fan fluttered at the design speed under off operating line, low flow conditions. This paper presents the blade vibration response characteristics over the operating range of the fan and compares them to predicted behaviors. It also provides an assessment of this distortion tolerant fan’s (DTF) ability to withstand the harsh dynamic BLI environment over an entire design life of billions of load cycles at design speed.
Machine Learning Enabled Adaptive Optimization of a Transonic Compressor Rotor With Pre-Compression
Authors: Joly Michael , Sarkar Soumalya , Mehta Dhagash
Published: August 2018

In aerodynamic design, accurate and robust surrogate models are important to accelerate computationally expensive CFD-based optimization. In this paper, a machine learning framework is presented to speed-up the design optimization of a highly-loaded transonic compressor rotor. The approach is three-fold: (1) dynamic selection and self-tuning among several surrogate models; (2) classification to anticipate failure of the performance evaluation; and (3) adaptive selection of new candidates to perform CFD evaluation for updating the surrogate, which facilitates design space exploration and reduces surrogate uncertainty. The framework is demonstrated with a multi-point optimization of the transonic NASA rotor 37, yielding increased compressor efficiency in less than 48 hours on 100 CPU cores. The optimized rotor geometry features pre-compression that relocates and attenuates the shock, without the stability penalty or undesired reacceleration usually observed in the literature.
Damping of Combustion Instabilities Through Pseudo-Active Control
Authors: Oliva Jesús , Luciano Ennio , Ballester Javier
Published: August 2018

Active instability control techniques have demonstrated very good capabilities to correct combustion oscillations but, due to high costs and other practical reasons, have not achieved the success expected in gas turbines engines. A different approach, named here as ‘pseudo-active instability control’, has been explored and the first results are presented in this work. In this case, the flow of non-premixed pilot fuel is modulated by passive methods: the pressure oscillation in the combustion chamber induces a velocity fluctuation at the secondary fuel injector. In principle, damping of the instability may be achieved if the heat release oscillations due to the secondary fuel are out of phase with those of the main flame.

This work reports a first exploration of this strategy, aimed mainly at performing a proof of the concept. An experimental study has been carried out in a laboratory premixed combustor with pilot fuel injection. The relationship between the fluctuations of pressure in the combustion chamber and those of velocity at the injector was studied both experimentally (hot wire anemometry) and theoretically (1-D acoustic model of the injection line). Combustion tests in limit cycle conditions demonstrated that modifications in the geometry of the secondary injection affected the pressure fluctuations inside the combustion chamber. Depending on the geometry (and, hence, acoustic impedance), the instability was enhanced or damped. This demonstrates that the proposed ‘pseudo-active control’ can produce similar effects (at least, qualitatively) to those of active control, but only using passive means, as initially postulated.
Scaling Sealing Effectiveness in a Stator-Rotor Cavity for Differing Blade Spans
Authors: Berdanier Reid A. , Monge-Concepción Iván , Knisely Brian F. , Barringer Michael D. , Thole Karen A. , Grover Eric A.
Published: August 2018

As engine development continues to advance toward increased efficiency and reduced fuel consumption, efficient use of compressor bypass flow, commonly used as cooling flow, becomes increasingly important. In particular, optimal use of compressor bypass flow yields an overall reduction of harmful emissions. The cooling flows used for cavity sealing between stages are critical to the engine and must be sufficiently maintained to prevent damaging ingestion from the hot gas path. To assess these cavity seals, the present study utilizes a one-stage turbine with true-scale engine hardware operated at engine-representative rotational Reynolds number and Mach number. Past experimental studies have made use of part-span rather than full-span blades to reduce flow rate requirements for the turbine test rig; however, such decisions raise questions about potential influences of the blade span on sealing effectiveness measurements in the rim cavity. For this study, a tracer gas facilitates measurements of sealing effectiveness in the rim cavity to compare measurements collected with full-span engine airfoils and simplified, part-span airfoils. The results from this study show sealing effectiveness does not scale as a function of relative purge flow with respect to main gas path flow rate when airfoil span is changed. However, scaling the sealing effectiveness for differing spans can be achieved if the fully-purged flow rate is known. Results also suggest reductions of purge flow may have a relatively small loss of seal performance if the design is already near a fully-purged condition. Rotor tip clearance is shown to have no effect on measured sealing effectiveness.
Development and Validation of Test Rig for Measurements of Leakage and Rotordynamic Performance of Interlocking Labyrinth Seals
Authors: Ramirez Mauricio , Childs Dara , Gary Keith
Published: August 2018

Understanding the rotordynamic and leakage characteristics of gas annular seals is important for the design of efficient and reliable turbomachinery. This work sets the foundation to advance the understanding of gas interlocking labyrinth seals. Data for such seals are vague and scarce. A test rig for interlocking seals is developed and validated via tests for a see-through tooth-on-stator labyrinth seal. Test procedures by Millsaps in 1994 and Wagner et al. in 2009 are adapted. Dynamic forces are integrated from the perturbed pressure fields created inside the seal cavities while precessing the rotor using magnetic bearings. Measurements are made by adapting a test rig at the Turbomachinery Lab at Texas A&M University. The see-through seal has eight stator teeth and a smooth rotor. The seal has a 75 mm radius, 3.5 mm tooth height, and 0.2 mm radial clearance. Tests at a rotor speed of 10 kRPM are performed for a range of inlet pressures, pressure ratios, and precession frequencies between 15 and 50 Hz. Forward and backward precessions are imposed. Measured leakage values and rotordynamic coefficients validate the performance of the test rig, making way for interlocking seal tests in the future.

Experience showed that differential pressure transducers, a well-machined stator, and precise alignment are required for accurate measurements. Two sensors 180° apart from each other in a representative cavity demonstrate the development of a correct pressure wave inside the seal. All results are repeatable. Static pressure measurements in the seal cavities show pressure drops linearly across the seal’s cavities. Results show frequency-independent rotordynamic coefficients.

As remarked above, only one of the seal’s cavities was provided with dynamic pressure measurements, and the following rotordynamic coefficients apply for that cavity, not the entire seal. Negative values of direct stiffness K and cross-coupled damping c confirm the lagging dynamic pressure wave is behind the rotor, pushing it radially into the stator. Positive values of cross-coupled stiffness k (where Kxy = −Kyx = k) and direct damping C counteract each other in the circumferential direction, the former being destabilizing. Effective damping Ceff combines the stabilizing impact of direct damping C and cross-coupled stiffness k. Measured cavity Ceff values are negative, and thus destabilizing in the circumferential direction. Future work involves testing interlocking labyrinth seals and using the test results to benchmark CFD codes.
On the Efficacy of Integrating Structural Struts With Lobed Mixers in Turbofan Engine Exhaust Systems
Authors: Wright Alexander , Mahallati Ali , Conlon Martin J. , Militzer Julio
Published: August 2018

The efficacy of integrating the lobed mixer with the core flow deswirling struts to create a single component for reducing the exhaust system length, beyond that attainable through mixer optimization alone, has been investigated. This investigation has been conducted via CFD simulations of a medium-bypass turbofan exhaust system at engine cruise representative conditions. Comparative analysis shows that integration augmented thrust output by about 0.02% while total pressure loss was increased by 3.6%. The aim of the study, to show that this new integrated design would have either minimal impact on or improve exhaust system performance, was confirmed. Comparisons of the flow fields and characteristic quantities downstream of the mixer also showed minimal impact on flow through the nozzle. The deswirling strut was offset by 0.65 Dh axially when integrated with the mixer, therefore it can be concluded that the exhaust system ducting could be reduced in length by this same measure — saving engine weight in the process.
Mathematical Simulation of the Gas Turbine Packages Thermal State
Authors: Kyrylash Olena , Kostiuk Volodymyr , Smirnov Andrii , Tkachenko Dmytro , Loboda Igor
Published: August 2018

The paper is devoted to the use of mathematical simulation to investigate the possibilities of ensuring the admissible thermal mode of gas turbine packages equipped with aircraft and marine derivative gas turbine engines. The method proposed for complex heat transfer simulation in the gas turbine packages includes some models. A generalized mathematical model is formed to describe the thermophysical processes taking place in the gas turbine packages. A particular mathematical model of gas turbine engine casing heat transfer and a method to correct the boundary conditions are also developed. These models have been validated with the data collected from the heat transfer measurements in simple objects and from full-scale tests of turbo-compressor units. The proposed method of complex heat transfer simulation has been used to evaluate a temperature state of the gas turbine packages, in particular to ensure the effectiveness of covering the engine casing by thermal insulation.
Operational Flexibility of GE’s F-Class Gas Turbines With the DLN2.6+ Combustion System
Authors: York William D. , Simons Derrick W. , Fu Yongqiang
Published: August 2018

F-class gas turbines comprise a major part of the heavy-duty gas turbine power generation fleet worldwide, despite increasing penetration of H/J class turbines. F-class gas turbines see a wide range of applications, including simple cycle peaking operation, base load combined cycle, demand following in simple or combined cycle, and cogeneration. Because of the different applications, local power market dynamics, and varied emissions regulations by region or jurisdiction, there is a need for operational flexibility of the gas turbine and the combustion system.

In 2015, GE introduced a DLN2.6+ combustion system for new and existing 7F gas turbines. Approximately 50 are now in operation on 7F.04 and 7F.05 turbines, combining for nearly 150,000 fired hours. The system has been demonstrated to deliver 5 ppm NOx emissions @ 15% O2, and it exhibits a wide window of operation without significant thermoacoustic instabilities, owing the capability to premixed pilot flames on the main swirl fuel-air premixers, low system residence time, and air path improvements. Based on the success on the 7F, this combustion system is being applied to the 6F.03 in 2018.

This paper highlights the flexibility of the 7F and 6F.03 DLN2.6+ combustion system and the enabling technology features. The advanced OpFlex* AutoTune control system tightly controls NOx emissions, adjusts fuel splits to stay clear of instabilities, and gives operators the ability to prioritize emissions or peak load output. Because of the low-NOx capability of the system, it is often being pushed to higher combustor exit temperatures, 35°C or more above the original target. The gas turbine is still meeting 9 or 15 ppm NOx emissions while delivering nearly 12% additional output in some cases. Single-can rig test and engine field test results show a relatively gentle NOx increase over the large range of combustor exit temperature because of the careful control of the premixed pilot fuel split. The four fuel legs are staged in several modes during startup and shutdown to provide robust operation with fast loading capability and low starting emissions, which are shown with engine data. The performance of a turndown-only fueling mode is highlighted with engine measurements of CO at low load. In this mode, the center premixer is not fueled, trading the NOx headroom for a CO emissions benefit that improves turndown. The combustion system has also demonstrated wide-Wobbe capability in emissions compliance. 7F.04 engine NOx and dynamics data are presented with the target heated gas fuel and also with cold fuel, producing a 24% increase in Modified Wobbe Index. The ability to run unheated fuel at base load may reduce the start-up time for a combined cycle plant. Lastly, there is a discussion of a new OpFlex* Variable Load Path digital solution in development that will allow operators to customize the start-up of a combined cycle plant.
Technology Application to MHPS Large Flame F Series Gas Turbine
Authors: Fujimoto Kiyoshi , Fukunaga Yuya , Hada Satoshi , Ai Toshishige , Yuri Masanori , Masada Junichiro
Published: August 2018

The development of gas turbines, Mitsubishi Hitachi Power Systems, Ltd. (MHPS) has continued to pursue and contribute to society in terms of global environmental conservation and stable energy supply. MHPS leverages its abundant gas turbine operation experience and takes advantage of its extensive advanced technologies research on the Japanese National Project.

MHPS has been participating in this project since 2004. Recent years’ achievements include the demonstration of a gas turbine combined cycle (GTCC) efficiency in excess of 62% created by increasing the turbine inlet temperature to the 1,600°C class in the M501J in 2011.

The Latest M701F incorporates “J” gas turbine technologies, already applied to actual equipment, for efficiency improvement. It also applies air-cooled combustor technologies successfully validated in the G class, for increased flexibility. The 1st unit started commercial operation in 2015 and currently 4 units has accumulated more than 46,000 actual operating hours collectively.

MHPS is making the upgrading program for existing F-series gas turbines. The proven technology verified in the M501J and developed in the National project increases efficiency and reliability.

This paper explains the features and development status of Latest M701F gas turbine, and explains upgrade program for existing F-series gas turbines.
Morphological ontogeny of Amblydromalus limonicus (Acari: Phytoseiidae)
Authors: Ma Min , Fan Qing-Hai , Zhang Zhi-Qiang
Published: August 2018

The morphological ontogeny of Amblydromalus limonicus is described in this paper based on laboratory-reared specimens originated from Auckland, New Zealand. Comparisons between A. limonicus and A. lailae from Australia showed that the protonymphs, deutonymphs and adults of these two species are not distinguishable, but unusual differences are present in larvae. The larvae of “A. lailae” by Schicha of Australia were incorrectly associated with other stages of A. lailae and belong to the genus Euseius. The results of this study highlight a neglected area of research in phytoseiid taxonomy: the careful descriptions of immature stages based on reared specimens.
Associations of 25-Hydroxyvitamin D With the Blood Pressure Response to Maximal Exercise Among Healthy Adults
Authors: Zaleski Amanda , Taylor Beth , Armstrong Braden , Puglisi Michael , Clarkson Priscilla , Chipkin Stuart , White Charles Michael , Thompson Paul D. , Pescatello Linda S.
Published: August 2018

Insufficient 25-hydroxyvitamin D [25(OH)D] levels are associated with high resting blood pressure (BP). However, the relationship between 25(OH)D and the peak systolic BP (SBP) response to exercise, a predictor of future hypertension, has yet to be investigated. We sought to examine the relationship among serum 25(OH)D and the peak SBP response to a graded exercise stress test (GEST) among a large sample (n = 417) of healthy men (49%) and women (51%) over a broad age range (20–76 years; mean age: 44.1 ± 0.8 years). We hypothesized that individuals with clinically insufficient 25(OH)D would have a greater peak SBP response to a GEST compared to individuals with sufficient 25(OH)D levels. Fasting serum 25(OH)D, anthropometrics, resting BP, and peak exercise SBP were obtained at the baseline visit of a larger clinical trial (STOMP; NCT01140308). Mean 25(OH)D levels were 36.1 ± 0.7 ng/ml, with ∼35% of individuals classified as insufficient (<30 ng/ml). Average resting BP was 119 ± 13 mmHg/75 ± 10 mmHg, with 52.3% considered to have normal BP, while 25.2% had elevated BP and 22.5% had established hypertension. The peak SBP response to a GEST was similar between individuals with sufficient (48 ± 19 mmHg) versus insufficient (48 ± 18 mmHg) 25(OH)D (p = 1.000). One unexpected finding emerged such that individuals with sufficient 25(OH)D had higher resting SBP (120 ± 14 mmHg vs. 117 ± 13 mmHg; p = .020) than individuals with insufficient 25(OH)D. In contrast to our hypothesis, 25(OH)D levels were not associated with the peak SBP response to a GEST. Baseline 25(OH)D levels were positively correlated with resting SBP; however, the magnitude of this effect is likely not clinically meaningful.
Emerging applications for DNA writers and molecular recorders
Authors: Farzadfard Fahim , Lu Timothy K.
Published: August 2018

Natural life is encoded by evolvable, DNA-based memory. Recent advances in dynamic genome-engineering technologies, which we collectively refer to as in vivo DNA writing, have opened new avenues for investigating and engineering biology. This Review surveys these technological advances, outlines their prospects and emerging applications, and discusses the features and current limitations of these technologies for building various genetic circuits for processing and recording information in living cells.
Comment on “Unexpected reversal of C
3
versus C
4
grass response to elevated CO
2
during a 20-year field experiment”
Authors: Nie Ming , Zou Junyu , Xu Xiao , Liang Chao , Fang Changming , Li Bo
Published: August 2018

Reich
et al
. (Reports, 20 April 2018, p. 317) reported that elevated carbon dioxide (eCO
2
) switched its effect from promoting C
3
grasses to favoring C
4
grasses in a long-term experiment. We argue that the authors did not appropriately elucidate the interannual climate variation as a potential mechanism for the reversal of C
4
-C
3
biomass in response to eCO
2
.
Insect threats to food security
Authors: Riegler Markus
Published: August 2018

Pest damage to crops will increase substantially in many regions as the planet continues to warm
Venoms to the rescue
Authors: Holford Mandë , Daly Marymegan , King Glenn F. , Norton Raymond S.
Published: August 2018

Insights into the evolutionary biology of venoms are leading to therapeutic advances
Comment on “Innovative scattering analysis shows that hydrophobic disordered proteins are expanded in water”
Authors: Fuertes Gustavo , Banterle Niccolo , Ruff Kiersten M. , Chowdhury Aritra , Pappu Rohit V. , Svergun Dmitri I. , Lemke Edward A.
Published: August 2018

Editors at
Science
requested our input on the above discussion (comment by Best
et al
. and response by Riback
et al
.) because both sets of authors use our data from Fuertes
et al
. (2017) to support their arguments. The topic of discussion pertains to the discrepant inferences drawn from SAXS versus FRET measurements regarding the dimensions of intrinsically disordered proteins (IDPs) in aqueous solvents. Using SAXS measurements on labeled and unlabeled proteins, we ruled out the labels used for FRET measurements as the cause of discrepant inferences between the two methods. Instead, we propose that FRET and SAXS provide complementary readouts because of a decoupling of size and shape fluctuations that is intrinsic to finite-sized, heteropolymeric IDPs. Accounting for this decoupling resolves the discrepant inferences between the two methods, thus making a case for the utility of both methods.
Clinical and multi-omics cross-phenotyping of patients with autoimmune and autoinflammatory diseases: the observational TRANSIMMUNOM protocol
Authors: Lorenzon Roberta , Mariotti-Ferrandiz Encarnita , Aheng Caroline , Ribet Claire , Toumi Ferial , Pitoiset Fabien , Chaara Wahiba , Derian Nicolas , Johanet Catherine , Drakos Iannis , Harris Sophie , Amselem Serge , Berenbaum Francis , Benveniste Olivier , Bodaghi Bahram , Cacoub Patrice , Grateau Gilles , Amouyal Chloe , Hartemann Agnes , Saadoun David , Sellam Jeremie , Seksik Philippe , Sokol Harry , Salem Joe-Elie , Vicaut Eric , Six Adrien , Rosenzwajg Michelle , Bernard Claude , Klatzmann David
Published: August 2018

Introduction

Autoimmune and autoinflammatory diseases (AIDs) represent a socioeconomic burden as the second cause of chronic illness in Western countries. In this context, the TRANSIMMUNOM clinical protocol is designed to revisit the nosology of AIDs by combining basic, clinical and information sciences. Based on classical and systems biology analyses, it aims to uncover important phenotypes that cut across diagnostic groups so as to discover biomarkers and identify novel therapeutic targets.

Methods and analysis

TRANSIMMUNOM is an observational clinical protocol that aims to cross-phenotype a set of 19 AIDs, six related control diseases and healthy volunteers . We assembled a multidisciplinary cohort management team tasked with (1) selecting informative biological (routine and omics type) and clinical parameters to be captured, (2) standardising the sample collection and shipment circuit, (3) selecting omics technologies and benchmarking omics data providers, (4) designing and implementing a multidisease electronic case report form and an omics database and (5) implementing supervised and unsupervised data analyses.

Ethics and dissemination

The study was approved by the institutional review board of Pitié-Salpêtrière Hospital (ethics committee Ile-De-France 48–15) and done in accordance with the Declaration of Helsinki and good clinical practice. Written informed consent is obtained from all participants before enrolment in the study. TRANSIMMUNOM’s project website provides information about the protocol (https://www.transimmunom.fr/en/) including experimental set-up and tool developments. Results will be disseminated during annual scientific committees appraising the project progresses and at national and international scientific conferences.

Discussion

Systems biology approaches are increasingly implemented in human pathophysiology research. The TRANSIMMUNOM study applies such approach to the pathophysiology of AIDs. We believe that this translational systems immunology approach has the potential to provide breakthrough discoveries for better understanding and treatment of AIDs.

Trial registration number

NCT02466217; Pre-results.
To what extent is the elevated risk of psychological distress in people with diabetes accounted for by physical disability? Findings from a large population-based study
Authors: Elmira Elza , Banks Emily , Joshy Grace
Published: August 2018

Objectives

People with diabetes experience an elevated risk of psychological distress compared with people without diabetes. It is unclear how much of this elevated risk is attributable to the greater levels of physical disability in people with diabetes, and how this risk varies according to sociodemographic and health-behavioural characteristics. This study quantified levels of psychological distress in people with and without diabetes, considering these factors.

Design

Cross-sectional analysis of questionnaire data.

Setting

Men and women aged ≥45 years, in the 45 and Up Study, from New South Wales, Australia.

Participants

236 441 people who completed the baseline postal questionnaire (distributed from 1 January 2006–31 December 2008), with valid data for diabetes status and psychological distress.

Primary outcome measures

High psychological distress (Kessler-10 >22). Modified Poisson regression with robust error variance was used to estimate prevalence ratios (PRs), comparing prevalence of high psychological distress among those with and without diabetes and across physical functional limitation (PFL) levels, adjusting for potential confounders.

Results

Overall, 8.4% (19 803/236 441) of participants reported diabetes. 11.8% (2339) of individuals with diabetes and 7.2% (15 664) without diabetes had high psychological distress: age-adjusted and sex-adjusted PR=1.89 (95% CI 1.81 to 1.97), becoming 1.58 (1.52 to 1.65) and 1.22 (1.17 to 1.27) following additional adjustment for sociodemographic factors, health behaviours and additionally for PFL, respectively. Compared with individuals with neither diabetes nor PFL, the adjusted PRs for high psychological distress were: 1.37 (1.17 to 1.60) with diabetes but no PFL, 7.33 (7.00 to 7.67) without diabetes but with severe PFL and 8.89 (8.36 to 9.46) with both diabetes and severe PFL.

Conclusions

People with diabetes have a 60% greater risk of high psychological distress than people without diabetes; a substantial proportion of this elevation is attributable to higher levels of disability with diabetes, especially factoring in measurement error. Psychological distress is strongly related to physical impairment.