bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow Field and Hot Streak Migration Through High Pressure Cooled Vanes With Representative Lean Burn Combustor Outflow
Authors: Bacci T. , Lenzi T. , Picchi A. , Mazzei L. , Facchini B.
Published: August 2018

Modern lean burn aero-engine combustors make use of relevant swirl degrees for flame stabilization. Moreover important temperature distortions are generated, in tangential and radial directions, due to discrete fuel injection and liner cooling flows respectively. At the same time, more efficient devices are employed for liner cooling and a less intense mixing with the mainstream occurs. As a result, aggressive swirl fields, high turbulence intensities and strong hot streaks are achieved at the turbine inlet. In order to understand combustor-turbine flow field interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together.

In this perspective, an annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at the THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central NGV aligned with the central swirler.

In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50°, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the final aim of investigating the hot streaks evolution through the cooled high pressure vane, the mean aerothermal field (temperature, pressure and velocity fields) has been evaluated by means of a five hole probe equipped with a thermocouple and traversed upstream and downstream of the NGV cascade.
An Extension of the Classical Subset of Nominal Modes Method for the Model Order Reduction of Gyroscopic Systems
Authors: Waldherr Christian U. , Vogt Damian M.
Published: August 2018

In the structural dynamics design process of turbomachines, Coriolis effects are usually neglected. This assumption holds true if no pronounced interaction between the shaft and disk occurs or if the radial blade displacements are negligible. For classical rotordynamic investigations or for machines where the disk is comparatively thin or weak, Coriolis effects as well as centrifugal effects like stress stiffening and spin softening have to be taken into account. For the analysis of complex structures the finite element method is today the most commonly used modeling approach. To handle the numerical effort in such an analysis, the aim of the present work is the further development of an existing reduced order model, which also allows the consideration of Coriolis effects without the loss of accuracy for a wide range of rotational speeds. In addition to the investigation of the tuned design of the bladed disk using cyclic boundary conditions, the described method is also appropriate to investigate mistuning phenomena including Coriolis effects. Due to the fact that the computation time can be reduced by two orders of magnitude, the method also opens up the possibility for performing probabilistic mistuning investigations including Coriolis effects.
On the Simulation of Unsteady Turbulence and Transition Effects in a Multistage Low Pressure Turbine: Part III — Comparison of Harmonic Balance and Full Wheel Simulation
Authors: Kügeler Edmund , Geiser Georg , Wellner Jens , Weber Anton , Moors Anselm
Published: August 2018

This is the third part of a series of three papers on the simulation of turbulence and transition effects in a multistage low pressure turbine. The third part of the series deals with the detailed comparison of the Harmonic Balance calculations with the full wheel simulations and measurements for the two-stage low-pressure turbine. The Harmonic Balance simulations were carried out in two confingurations, either using only the 0th harmonic in the turbulence and transition model or additional in all harmonics. The same Menter SST two-equation k–ω turbulence model along with Menter and Langtrys two-equation γ–Reθ transition model is used in the Harmonic Balance simulation as in the full wheel simulations. The measurements on the second stator ofthe low-pressure turbine have been carried out separately for downstream and upstream influences. Thus, a dedicated comparison of the downstream and upstream influences of the flow to the second stator is possible. In the Harmonic Balance calculations, the influences of the not directly adjacent blade, i.e. the first stator, were also included in the second stator In the first analysis, however, it was shown that the consistency with the full wheel configuration and the measurement in this case was not as good as expected. From the analysis ofthe full wheel simulation, we found that there is a considerable variation in the order ofmagnitude ofthe unsteady values in the second stator. In a further deeper consideration of the configuration, it is found that modes are reflected in upstream rows and influences the flow in the second stator. After the integration of these modes into the Harmonic Balance calculations, a much better agreement was reached with results ofthe full wheel simulation and the measurements. The second stator has a laminar region on the suction side starting at the leading edge and then transition takes place via a separation or in bypass mode, depending on the particular blade viewed in the circumferential direction. In the area oftransition, the clear difference between the calculations without and with consideration ofthe higher harmonics in the turbulence and transition models can be clearly seen. The consideration ofthe higher harmonics in the turbulence and transition models results an improvement in the consistency.
On the Simulation of Unsteady Turbulence and Transition Effects in a Multistage Low Pressure Turbine: Part II — Full-Wheel Simulation
Authors: Geiser Georg , Wellner Jens , Kügeler Edmund , Weber Anton , Moors Anselm
Published: August 2018

This is the second part of a series of three papers on the simulation of turbulence and transition effects in a multistage low pressure turbine. In this second part, the investigated two-stage low pressure turbine is described and results of a nonlinear full-wheel time-domain simulation are presented, analyzed and compared with the available experimental data. Furthermore, recent improvements to the CFD solver TRACE are described in brief that lead to significantly reduced wall-clock times for such large scale simulations. The utilized models match those used in the Harmonic Balance (HB) based simulations that are presented in the third paper of this series, such that the full-wheel result can be utilized to validate the HB result. Transition, flow separation and wall pressure fluctuations on the stator blades of the second stage are analyzed in detail. A strong azimuthal π-periodicity is observed, manifesting in a significantly varying stability of the midspan trailing edge flow with a quasi-steady closed separation bubble on certain blades and highly dynamic partially open separation bubbles with recurring transition and turbulent reattachment on other blades. The energy spectrum of fluctuating wall quantities in that regime shows a high bandwidth and considerable disharmonic content, which is challenging for the HB based simulations.
On Deposition and Build-Up Detachment in Compressor Fouling
Authors: Casari Nicola , Pinelli Michele , Suman Alessio
Published: August 2018

Compressor fouling is a severe problem for both heavy-duty and aero-propulsion gas turbines. Particles can impinge on the blade and annulus surfaces, sticking there. The consequences of particle deposition are the increase of the roughness and an uncontrolled variation in the surface shape. These problems have a major effect on the performance of the compressor over time.

Variations in the flow field can make the flow quantities close to the deposit to change, and it may happen that the conditions for the sticking do not hold any longer. If this is the case, the build-up detachment may happen. This occurrence can mitigate the fouling effects and may be exploited for keeping the performance of the compressor as high as possible over the operating period. In this work, an innovative model is proposed in order to evaluate the adhesion forces and the possible detachment. Particularly, the same forces that keep a gecko stuck to a surface are considered: the van der Waals forces (due to the proximity of the two bodies) and the Laplace force (due to the curvature of the liquid film related to the humidity). The so formulated model, named gecko-like for such a reason, is used for the numerical analyses of a deposition problem. Both the sticking and possible build-up detachment are considered. The outcome of this work can be regarded as an a-priori estimate of the forces to be kept into account when dealing with compressor fouling problems.
Flame and Spray Dynamics During the Light-Round Process in an Annular System Equipped With Multiple Swirl Spray Injectors
Authors: Prieur Kevin , Durox Daniel , Vignat Guillaume , Schuller Thierry , Candel Sébastien
Published: August 2018

The ignition process of an annular combustor can be divided in several steps that end with the light-round. This corresponds to the sequence from the ignition of the first injector to the merging of the two flame fronts spreading in the annular system. The present article focuses on this important step, where two arch-like flame branches propagate in the chamber. These two turbulent travelling flames, nearly perpendicular to the combustor backplane, successively ignite the injection units and finally collide head-on and merge. In the present study, light-round of spray flames fed by liquid n-heptane is investigated. A high-speed camera operating at a frame rate of 6000 Hz and equipped with a filter centered on CH* emission is positioned on the side of the annular combustor, at the chamber backplane level and records images of one half of the chamber annulus. Acoustic pressure fluctuations are recorded through waveguide microphones plugged on the chamber backplane and microphones flush mounted in the annular plenum. The behavior of one injector ignited by the passing flame front is examined. One finds that the swirling flame structure formed by each injection unit evolves in time and that the anchoring location changes just after the passage of the travelling flame and during a period of a few milliseconds. This behavior can eventually lead to a flashback of the flame in the injector with possible severe damages. This dynamical phenomenon is described in detail. The propagation of the arch-like flame branch is then investigated. Flame images are used to determine the direction and velocity of the flame front by making use of a PIV like processing. One may distinguish two regions for the flame propagation. One is near the backplane, moving in a purely azimuthal direction, while the other corresponds to the remaining flame motion in the azimuthal and axial directions due to the volumetric expansion of the burnt gases. Filtered light images give some indications on the complex flame structures and on the typical length scales characterizing the moving front. Information is also obtained on the dynamics of the spray by shining a continuous laser sheet passing through one injector central axis and recording the light scattered by the n-heptane spray of droplets. These images are used to determine the influence of the incoming flame front on the evaporating n-heptane liquid droplets. A major result is that the flame modifies the spray much before its leading point reaches the injector unit and that its passage through the spray drastically changes the local droplet concentration and thus the local mixture composition.
A Methodology for Fully-Coupled CFD Engine Simulations, Applied to a Micro Gas Turbine Engine
Authors: Teixeira Mateus , Romagnosi Luigi , Mezine Mohamed , Baux Yannick , Anker Jan , Claramunt Kilian , Hirsch Charles
Published: August 2018

The development of new generations of aircraft engines with reduced environmental impact heavily relies on high-fidelity 3D numerical analysis of the main engine components, compressor, combustion chamber, turbine and their interactions, including the transient and off-design behavior of the full engine.

Unlike component-by-component analysis, which requires separate assumptions for the pressure and temperature boundary conditions for each component, a fully coupled approach requires only knowledge of the compressor inlet and turbine outlet flow conditions. In addition, the engine rotation speed can also be varied during the simulation to converge to the correct balance of power between compressor and turbine.

This integrated approach provides a detailed description of the flow field inside the full engine at the desired operating point with one single CFD simulation.

The full engine simulation methodology can be developed at several levels: (1) RANS simulations with mixing-plane interfaces between components; (2) advanced RANS treatment with inputs from the nonlinear harmonic (NLH) methodology to allow for tangential non-uniformity, such as hot streaks entering the turbine nozzle from the combustor; (3) inclusion of the unsteady rotor-stator interactions, via NLH, in compressor and turbine stages; (4) coupling with LES simulations in the combustor.

This paper presents results from levels (1) and (2) of this methodology applied to a micro-turbine gas engine including the HP compressor, combustor, HP and LP turbines and the exhaust hood. The geometry has been obtained from the redesign of the KJ66 micro gas turbine engine using preliminary design tools. The injection and burning of fuel inside the combustion chamber are modeled with a simplified flamelet model. The paper presents the approach and results of the full engine simulation; as well as the initial steps towards level (3).
Turbopump Booster Turbine Performance: Comparison Between Monophase and Multiphase Flows Using CFD
Authors: Lindquist Whitacker Luiz Henrique , Tomita Jesuino Takachi , Bringhenti Cleverson
Published: August 2018

Boosters are commonly used in liquid propellant rocket engines (LPRE) to allow lower propellant pressures in their storage tanks and, thus, smaller structural masses, contributing to cavitation free operation in the subsequent main turbopumps (TP). Boosters can be identified as key components for the overall performance of large engines, and if their operating requirements are stringent, they can operate under cavitation. Thus, effective design and performance tools are fundamental to design the components of these boosters considering this phenomenon. The simulation techniques based on turbulent and multiphase 3-D Computational Fluid Dynamics (CFD) were used in this work at steady state regime. The simulations were done using the commercial software CFX from ANSYS® Workbench. The study was conducted analyzing the performance of the first stage of the hydraulic axial turbine of the liquid oxygen (LOX) booster of the Space Shuttle Main Engine (SSME), at various operation points under cavitation, considering 3.0% tip clearance relative to blade height. The results obtained for, the performance parameters of this stage were compared with those obtained through monophase simulation, and the multiphase technique showed results closer to the experimental ones around the design point (DP), with increased simulation times acceptable for the computational resources currently available. Moreover, the results from the current work show the importance of considering the effects of cavitation through multiphase flow in hydraulic turbines.
Engine-Scalable Rotor Casing Convective Heat Flux Evaluation Using Inverse Heat Transfer Methods
Authors: Cuadrado David G. , Lozano Francisco , Andreoli Valeria , Paniagua Guillermo
Published: August 2018

In this paper, we propose a two-step methodology to evaluate the convective heat flux along the rotor casing using an engine-scalable approach based on Discrete Green’s Functions. The first step consists in the use of an inverse heat transfer technique to retrieve the heat flux distribution on the shroud inner wall by measuring the temperature of the outside wall; the second step is the calculation of the convective heat flux at engine conditions, using the experimental heat flux and the Green Functions engine-scalable technique. Inverse methodologies allow the determination of boundary conditions, in this case the inner casing surface heat flux, based on measurements from outside of the system, which prevents aerothermal distortion caused by routing the instrumentation into the test article. The heat flux, retrieved from the inverse heat transfer methodology, is related to the rotor tip gap. Therefore, for a given geometry and tip gap, the pressure and temperature can also be retrieved. In this work, the Digital Filter Method is applied in order to take advantage of the response of the temperature to heat flux pulses. The Discrete Green’s Function approach employs a matrix to relate an arbitrary temperature distribution to a series of pulses of heat flux. In the present procedure, the terms of the Green’s Function matrix are evaluated with the output of the inverse heat transfer method. Given that key dimensionless numbers are conserved, the Green’s Functions matrix can be extrapolated to engine-like conditions.

A validation of the methodology is performed by imposing different arbitrary heat flux distributions, to finally demonstrate the scalability of the Green’s Function Method to engine conditions. A detailed uncertainty analysis of the two-step routine is included based on the value of the pulse of heat flux, the temperature measurement uncertainty, the thermal properties of the material and the physical properties of the rotor casing.
Fouling on a Multistage Axial Compressor in the Presence of a Third Substance at the Particle/Surface Interface
Authors: Aldi Nicola , Casari Nicola , Dainese Devid , Morini Mirko , Pinelli Michele , Spina Pier Ruggero , Suman Alessio
Published: August 2018

Solid particle ingestion is one of the principal degradation mechanisms in the compressor and turbine sections of gas turbines. In particular, in industrial applications, the micro-particles not captured by the air filtration system can cause deposits on blades and, consequently, can result in a decrease in compressor performance. It is of great interest to the industry to determine which zones of the compressor blades are impacted by these small particles. However, this information often refers to single stage analysis.

This paper presents three-dimensional numerical simulations of the micro-particle ingestion (0.15 μm – 1.50 μm) in a multistage (i.e. eight stage) subsonic axial compressor, carried out by means of a commercial CFD code. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separately from the continuous phase.

The effects of humidity, or more generally, the effects of a third substance at the particle/surface interface (which is considered one of the major promoters of fouling) is then studied. The behavior of wet and oiled particles, in addition to the usual dry particles, is taken into consideration. In the dry case, the particle deposition is established only by using the sticking probability. This quantity links the kinematic characteristics of particle impact on the blade with the fouling phenomenon. In the other two cases, the effect of the presence of a third substance at the particle/surface interface is considered by means of an energy-based model. Moreover, the influence of the tangential impact velocity on particle deposition is analyzed.

Introducing the effect of a third substance, such as humidity or oil, the phenomenon of fouling concerns the same areas of the multistage compressor. The most significant results are obtained by combining the effect of the third substance with the effect of the tangential component of the impact velocity of the particles. The deposition trends obtained with these conditions are comparable with those reported in literature, highlighting how the deposits are mainly concentrated in the early stages of a multistage compressor. Particular fluid dynamic phenomena, such as corner separations and clearance vortices, strongly influence the location of particle deposits.
Development and Testing of the Hybrid Electric Drive Program for the Navy’s DDG 51 Class Ships
Authors: Buonamici Gianfranco , Schauble Michael
Published: August 2018

This paper will discuss the development and testing of an electric drive option designed for the propulsion system of the US Navy’s DDG 51 Class ships. It will briefly explain the history of the Hybrid Electric Drive (HED) program, including that of its predecessor, Proof of Concept (PoC), and the HED’s planned shipboard installation schedule.

Operating at lower ship speeds, in a range where the currently installed propulsion gas turbines are less fuel efficient, the HED is expected to increase the ship’s fuel economy, allowing the ship to remain on station accomplishing its mission for a longer period of time. This paper will discuss how the gas turbine propulsion system, in concert with the HED, will be used to provide the most fuel efficient drive combination for various operating scenarios. Also covered will be a description of the major stakeholders involved in the HED’s development and implementation along with some of the constraints and challenges that were encountered in the testing phase of the program, both at the OEM facilities and at the US Navy’s Land Based Engineering Site (LBES) in Philadelphia PA.

Planned fuel economy testing results obtained at the LBES facility will also be presented, intended to determine an estimate of the fuel savings that can be expected when the system is first placed in service on USS TRUXTUN (DDG 103) July 2018.
Development and Testing of a Gas Turbine Engine Combustion Air Inlet Protection Shroud for the USMC Amphibious Combat Vehicle
Authors: Gastopoulos Thomai , McGinn Patricia , Lawton Joseph
Published: August 2018

The Marine Corps Systems Command is evaluating alternative propulsion systems to achieve high water speed for the future USMC Amphibious Combat Vehicle (ACV). A gas turbine engine is one of the propulsion systems evaluated. The primary risk of operating a gas turbine engine in the ACV is power loss due to the ingestion of marine contaminants such as saltwater mist in the air, saltwater spray generated from the vehicle operation, green water wash caused by the operation of the vehicle in the surf zone or in rough seas, and hard particles such as sand present in the marine environment.

The Auxiliary Ships and New Acquisition Support Branch (Code 425) of the Naval Surface Warfare Center, Philadelphia Division conducted a study to assist the Marine Corps Systems Command in assessing the feasibility of using a gas turbine engine as a propulsion system on future USMC ACVs. The study was focused on developing and testing a gas turbine intake solution for the ACV that can remove saltwater from the intake airstream of the notional 3,000 horsepower ACV engine.

Code 425 developed a two-part solution for the intake of the ACV. The first part of the solution is the Combustion Air Protection Shroud (CAPS) located at the entrance of the engine intake and designed to protect the ACV engine from green water wash by elevating the intake above the ACV deck. The second part of the solution is a gas turbine intake filtration system located downstream of the intake shroud and designed to remove marine contaminants that enter the intake shroud.

A reduced-scale model of the CAPS was designed by Code 425 in conjunction with Gibbs & Cox and tested at the Davidson Laboratory High Speed Test Basin at the Stevens Institute of Technology to determine the optimum extension height of the CAPS to protect the engine intake. This paper covers the design and testing of the CAPS. The results showed that a 2.67 ft. tall CAPS with selectively closeable air intake louvers is sufficient to keep out saltwater from the ACV gas turbine engine.
Heat Transfer in a Rotating Two-Pass Rectangular Channel Featuring Reduced Cross-Sectional Area After Tip Turn (AR=4:1 to 2:1) With Profiled 60 Deg Angled Ribs
Authors: Chen Andrew F. , Shiau Chao-Cheng , Han Je-Chin , Krewinkel Robert
Published: August 2018

The internal cooling channels of an advanced gas turbine blade typically have varying aspect ratios from one pass to another due to the varying thickness of the blade profile. Most of the fundamental internal cooling studies found in the open literature used a fixed aspect ratio for multi-pass channels. Studies on a reduced cross-section and aspect ratio channel are scarce. The current study features a two-pass rectangular channel with an aspect ratio AR = 4:1 in the first pass and an AR = 2:1 in the second pass after a 180 deg tip turn. In addition to the smooth-wall case, ribs with a profiled cross-section are placed at 60 deg to the flow direction on both the leading and trailing surfaces in both passages (P/e = 10, e/Dh ≈ 0.11, parallel and inline). Regionally averaged heat transfer measurement method was used to obtain the heat transfer coefficients on all surfaces within the flow passages. The Reynolds number (Re) ranges from 10,000 to 70,000 in the first passage, and the rotational speed ranges from 0 to 400 rpm. Under pressurized condition (570 kPa), the highest rotation number achieved was Ro = 0.39 in the first passage and 0.16 in the second passage. Rotation effects on both heat transfer and pressure loss coefficient for the smooth and rib-roughened cases are presented. The results showed that the turn induced secondary flows are reduced in an accelerating flow. The effects of rotation on heat transfer are generally weakened in the ribbed case than the smooth case. Significant heat transfer reduction on the tip wall was seen in both the smooth and ribbed cases under rotating condition. A reduced overall pressure penalty was seen for the ribbed case under rotation. Reynolds number effect was found noticeable in the current study. The heat transfer and pressure drop characteristics are sensitive to the geometrical design of the channel and should be taken into account in the design process.
Experimental and Numerical Analysis of Additively Manufactured Coupons With Parallel Channels and Inline Wall Jets
Authors: Parbat Sarwesh Narayan , Yang Li , Min Zheng , Chyu Minking K.
Published: August 2018

With the goal to realize gas turbine engine cycle efficiency of 65%, the turbine inlet temperature is predicted to rise to 1700° C. Additive manufacturing (AM) has opened new avenue to explore complex design spaces to enhance cooling in gas turbine blades. Present paper developed a series of additively manufactured parallel cooling channels with streamwise wall jets inside, which could be suitable for double wall and near wall cooling configurations in gas turbine hot section components. The tested coupons consisted of parallel channels, each channel further divided into small chambers using several spanwise separation walls. Height of these walls was kept less than channel height, thus forming a crossover slot jet with one of the end walls. Coolant entered from one side of channel and formed streamwise wall jet while crossing through the slot over to the downstream chamber. The test coupons were additively manufactured by Selective Laser Sintering technique using Inconel 718 alloy. Both experimental and numerical study has been conducted to analyze effect of pitch and blockage ratio on heat transfer. Pitch between subsequent slots was defined in terms of slot hydraulic diameter and was varied from 5Dj to 11Dj. Blockage ratio consisted of ratio of separation wall height to the channel height and varied from 0.5 to 0.75. Steady state heat transfer experiments with constant wall temperature boundary condition were performed for a channel Reynolds number range of 1800 to 5000. ANSYS CFX solver with the SST k-ω turbulence model was used to perform numerical simulation to obtain detailed understanding of existing flow field. Experimental results showed heat transfer enhancement of up to 6.5 times that of a smooth channel for the highest blockage ratio of 0.75. The blockage ratio exerted stronger effect both on pressure drop and heat transfer characteristics, as compared to pitch. The heat transfer as well as pressure drop were found to increase with a decrease in pitch and with an increase in blockage ratio. The numerical results revealed complex flow field which consisted of wall jets along with impingement, separation and recirculation zones in each chamber. It also revealed significant uniformity in heat transfer coefficient distribution on the slot side end wall. For all configurations, the gain in heat transfer was accompanied with high pressure drops. However, coupled with the high heat transfer, this design could lead to potential coolant savings.
Performance Assessment of a Micro Gas Turbine Cycle With Exhaust Gas Recirculation Fueled by Biogas for Post-Combustion Carbon Capture Application
Authors: Nikpey Somehsaraei Homam , Mansouri Majoumerd Mohammad , Assadi Mohsen
Published: August 2018

As a renewable energy source, biogas produced from anaerobic digestion seems to play an important role in the energy market. Unlike wind and solar, which are intermittent, gas turbines fueled by biogas provide dispatchable renewable energy that can be ramped up and down to match the demand. If post-combustion carbon capture systems are implemented, they can also result in negative CO2 emissions. However, one of the major challenges here is the energy needed for CO2 chemical absorption in post-combustion capture, which is closely related to the concentration of CO2 in the exhaust gas upstream of the capture unit. This paper presents an evaluation of the effects of biogas and exhaust gas recirculation use on the performance of the gas turbine cycle for post-combustion CO2 capture application. The study is based on a combined heat and power micro gas turbine, Turbec T100, delivering 100kWe. The thermodynamic model of the gas turbine has been validated against experimental data obtained from test facilities in Norway and the United Kingdom. Based on the validated model, performance calculations for the baseline micro gas turbine (fueled by natural gas), biogas-fired cases and the cycle with exhaust gas recirculation have been carried out at various operational conditions and compared together. A wide range of biogas composition with varying methane content was assumed for this study. Necessary minor modifications to fuel valves and compressor were assumed to allow the engine operation with different biogas composition. The methodology and results are fully discussed in this paper.
A Detailed Techno-Economic Analysis of Gas Turbines Applied to CSP Power Plants With Central Receiver
Authors: Martín Manuel , Sánchez David
Published: August 2018

The present work presents a very detailed techno-economic analysis of the technology made up of two complementary models. A performance model implemented in Thermoflex environment is used to explore alternative integration layouts to enable the simultaneous operation on solar and fossil energy. Then, a detailed cost analysis approaches the capital and operation costs of the plant from an EPC (Engineering, Procurement and Construction) standpoint. These two models are then combined in annual simulations to obtain the final Levelized Cost of Electricity from which a solid conclusion about the true potential of solar gas turbines can be ascertained. A sensitivity analysis with respect to the main boundary conditions is also provided.
Integral Techno-Economic Analysis of Supercritical Carbon Dioxide Cycles for Concentrated Solar Power
Authors: Crespi Francesco , Sánchez David , Sánchez Tomás , Martínez Gonzalo S.
Published: August 2018

Previous work by the authors has shown that broader analyses than those typically found in literature (in terms of operating pressures allowed) can yield interesting conclusions with respect to the best candidate cycles for certain applications. This has been tested for the thermodynamic performance (1st and 2nd Laws) but it can also be applied from an economic standpoint. This second approach is introduced in this work where typical operating conditions for CSP applications (current and future generations of solar tower plants) are considered (900 °C and 30 MPa). For these, the techno-economic performance of each cycle are assessed in order to identify the most cost-effective layout when it comes to the Overnight Capital Cost. This analysis accounts for the different contributions to the total cost of the plant, including all the major equipment that is usually found in a CSP power plant such as the solar field and thermal energy storage system. The work is thus aimed at providing guidelines to professionals in the area of basic engineering and pre-feasibility study of CSP plants who find themselves in the process of selecting a particular power cycle for a new project (set of specifications and boundary conditions).
Fuel Variation Effects in Propagation and Stabilization of Turbulent Counter-Flow Premixed Flames
Authors: Abbasi-Atibeh Ehsan , Jella Sandeep , Bergthorson Jeffrey M.
Published: August 2018

Sensitivity to stretch and differential diffusion of chemical species are known to influence premixed flame propagation, even in the turbulent environment where mass diffusion can be greatly enhanced. In this context, it is convenient to characterize flames by their Lewis number (Le), a ratio of thermal-to-mass diffusion. The work reported in this paper describes a study of flame stabilization characteristics when the Le is varied. The test data is comprised of Le ≪ 1 (Hydrogen), Le ≈ 1 (Methane), and Le > 1 (Propane) flames stabilized at various turbulence levels.

The experiments were carried out in a Hot exhaust Opposed-flow Turbulent Flame Rig (HOTFR), which consists of two axially-opposed, symmetric turbulent round jets. The stagnation plane between the two jets allows the aerodynamic stabilization of a flame, and clearly identifies fuel influences on turbulent flames. Furthermore, high-speed Particle Image Velocimetry (PIV), using oil droplet seeding, allowed simultaneous recordings of velocity (mean and rms) and flame surface position.

These experiments, along with data processing tools developed through this study, illustrated that in the mixtures with Le ≪ 1, turbulent flame speed increases considerably compared to the laminar flame speed due to differential diffusion effects, where higher burning rates compensate for the steepening average velocity gradient, and keeps these flames almost stationary as bulk flow velocity increases.

These experiments are suitable for validating the ability of turbulent combustion models to predict lifted, aerodynamically-stabilized flames. In the final part of this paper, we model the three fuels at two turbulence intensities using the FGM model in a RANS context. Computations reveal that the qualitative flame stabilization trends reproduce the effects of turbulence intensity, however, more accurate predictions are required to capture the influences of fuel variations and differential diffusion.
Large-Eddy Simulation of Corner Separation in a Compressor Cascade
Authors: Min Byung-Young , Joo Jongwook , Mendoza Jomar , Lee Jin , Xia Guoping , Medic Gorazd
Published: August 2018

In this paper, wall-resolved LES computations for a compressor cascade from Ecole Centrale de Lyon [1] are presented. A computational grid containing about 600 million computational cells was used in these simulations. This grid resolves the details of tripping strips used in the experiments, located near the leading edge of the blade on both suction and pressure sides. Endwall turbulent boundary layer at cascade inlet was measured to be at a momentum thickness based Reynolds number of about 7000 to 8000, with quite a bit of variation in the pitchwise direction. In order to avoid the cost of simulating the entire duct upstream of the cascade, and any auxiliary flat plate boundary layer simulations, the inlet fluctuations for LES computations were generated using digital filtering method for synthetic turbulence generation [27]. Turbulence statistics from a database of high fidelity eddy simulations of flat plate boundary layers (at similar Reynolds numbers) from KTH Royal Institute of Technology in Stockholm [28] were used to fully define the properties of the cascade inlet boundary layer.

In this paper, time-averaged results from three LES computations for this configuration are presented — one with no inlet fluctuations at the cascade endwall at the domain inlet, and then two computations with inlet fluctuations and boundary layers at Reθ of 7000 and 8183. These provide a sensitivity of LES predictions of corner separation in the cascade to the boundary layer thickness at cascade inlet.

A comparison of these simulations with prior DDES (and RANS) simulations from UTRC [26], as well as existing LES results from Ecole Centrale de Lyon [12], allows to further the understanding of critical elements of the endwall flow physics. More specifically, it provides more insight into which phenomena need to be sufficiently resolved (e.g. horseshoe vortex) in order to capture both the average behavior of the corner separation, as well as its unsteady dynamics. In addition, it provides new information which will help define best practice guidelines for the use of eddy simulations to resolve endwall features in compressors at off-design conditions.
An Investigation on the Static Performance of the Non-Circular Journal Bearing Using Fourier Analysis
Authors: Tian Jiale , Yang Baisong , Yu Lie , Zhou Jian
Published: August 2018

As one of the most important components in a rotor-bearing system, journal bearings provide proper support and damping to the rotor so that it can run both smoothly and efficiently and keep stable under different working conditions. As the rotating speed of the rotor growing faster and load getting heavier, the traditional cylinder journal bearing can no longer meet the demand of stabilizing the rotor, so different kinds of non-circular journal bearings were invented, such as elliptical bearing, multi-lobe bearing, wave bearing and etc., to provide better stability and greater load capacity. However, these kinds of non-circular bearings were mostly designed by experience of the engineers, and also the current hydrodynamic bearing design methodology still depends on empirical design. There lacks of corresponding theoretical foundation. In order to develop a theoretical method for bearing designing, an innovative analyzing approach needs to be carried out to explore the mechanism of the bearings and its performance. In this paper, a new approach is presented focusing on the profile of each bearing and their film thickness. A universal mathematical expression for different types of non-circular bearings has been put forward based on the Fourier series theory. The influence of periodic harmonics of film thickness on the static performance of non-circular bearings of finite length is studied for incompressible lubricant. The results show that the film thickness can always be expanded into a Fourier series, and the harmonic components of film pressure can be obtained by solving the Reynolds equation. Finally, the relation between the k-th order harmonic component H0,k and the corresponding static pressure component P0,k is established. This new investigation can be used to improve the non-circular bearing designing methodology with theoretical guidance.
The Influence of Thermal Transient Rates on Coated Turbine Parts Life Expectancy
Authors: Staroselsky Alexander , Martin Thomas J. , Borkowski Luke
Published: August 2018

During rapid engine throttling operations, turbine airfoils can experience very rapid heating and cooling, particularly at take-off conditions. These rapid transient events lead to the generation of high thermal gradients and non-uniform stress distributions through the thermal barrier coating, environmental barrier/bond coating and substrate. This in turn can lead to coating delamination, overheat of the substrate materials, creep and thermo-mechanical fatigue of the part. We present the process and computer modeling methodology for a physics-based prediction of deformation, damage, crack propagation and local failure modes in coated turbine airfoils and other parts operating at hot section turbine environment conditions as a function of engine operational regimes, with a particular emphasis on rapid transient events. The overall goal is to predict the effects and severity of the cooling and heating thermal rates on transient thermal mechanical fatigue life of coated hot parts (turbine airfoils, blade outer air seals and combustor liners). The computational analysis incorporates time-accurate, coupled aerothermodynamics with non-linear deformation thermal-structural finite element modeling and fracture mechanics modeling for high rate thermal transient events. Thermal barrier coating thermal failure and spallation are introduced by the use of interface fracture toughness and interface property evolution as well as dissipated energy rate. The spallation model allows estimations of the part remaining life as a function of the heating/cooling rates. Applicability of the developed model is verified using experimental coupons and calibrated against burner rig test data for high flux thermal cycles. Our results show a decrease in TBC spall life due to high rate transient events.
Ultrasound imaging for lateral knee pain: popliteus tendon highlighted
Authors: Ricci Vincenzo , Özçakar Levent
Published: August 2018

.
Review Article: Gas and vapor sorption measurements using electronic beam balances
Authors: Minnick David L. , Turnaoglu Tugba , Rocha Maria Alejandra , Shiflett Mark B.
Published: August 2018

The beam balance is one of the oldest known measuring instruments. Until the 20th century, balances had been the most sensitive and precise instruments used for scientific measurements. The original balances used a beam supported at the center with pans hung from cords on both ends. The modern electronic beam balances still resemble those original designs; however, the resolution, accuracy, and capabilities have been significantly improved. This review provides a short introduction to the history of beam balances followed by a detailed description of three gravimetric microbalances manufactured by Hiden Isochema for measuring gas and vapor sorption in a variety of materials.
Physical Literacy at the Start Line: Young Children’s Motor Competence, Fitness, Physical Activity, and Fitness Knowledge
Authors: Gu Xiangli , Chen Senlin , Zhang Xiaoxia
Published: August 2018

Purpose: Developing physically literate individuals is a major goal of school physical education. To date, no research in the United States has examined physical literacy by simultaneously measuring multiple dimensions among young children. The purpose of this study was to examine students’ current status of physical literacy in third grade. Method: Students (N = 342) from four elementary schools in Texas participated in the study. Dimensions of physical literacy including fundamental motor skills, health-related physical fitness, physical activity, and fitness knowledge were measured using the PE Metrics™, FitnessGram, accelerometers, and a written test, respectively. Results: The students showed varying levels of competencies across the physical literacy dimensions. Based on the results from multivariate analyses of variance, physical literacy as the single overarching factor was statistically associated with gender, Wilks’s λ = .90, F(5, 316) = 6.82, p < .01, weight status, Wilks’s λ = .81, F(5, 316) = 14.43, p < .01, and ethnicity, Wilks’s λ = .96, F(5, 316) = 2.47, p < .05. Subsequent univariate analyses showed that girls had higher cardiorespiratory endurance but lower physical activity than boys; students with healthy body weight had higher cardiorespiratory endurance and fundamental motor skills than those with unhealthy weight; and Hispanic children displayed higher muscular fitness than non-Hispanic children. Conclusion: The physical literacy discrepancies by gender, weight status, and ethnicity identified in this study are useful for physical educators to promote physical literacy in various student groups.
Amid fears of idea theft, NIH targets foreign funding links
Authors: Kaiser Jocelyn , Malakoff David
Published: August 2018

Agency reminds applicants to report all grant sources, warns against violating confidentiality of peer review.
Social science studies get a ‘generous’ test
Authors: Servick Kelly
Published: August 2018

New replication effort aimed to detect effects overstated in the original reports.
Federal research funding aims to ease societal challenges
Authors: Hoy Anne Q.
Published: August 2018

A key goal is to spread access to scientific excellence and federal research funding nationwide
Rearrangement bursts generate canonical gene fusions in bone and soft tissue tumors
Authors: Anderson Nathaniel D. , de Borja Richard , Young Matthew D. , Fuligni Fabio , Rosic Andrej , Roberts Nicola D. , Hajjar Simon , Layeghifard Mehdi , Novokmet Ana , Kowalski Paul E. , Anaka Matthew , Davidson Scott , Zarrei Mehdi , Id Said Badr , Schreiner L. Christine , Marchand Remi , Sitter Joseph , Gokgoz Nalan , Brunga Ledia , Graham Garrett T. , Fullam Anthony , Pillay Nischalan , Toretsky Jeffrey A. , Yoshida Akihiko , Shibata Tatsuhiro , Metzler Markus , Somers Gino R. , Scherer Stephen W. , Flanagan Adrienne M. , Campbell Peter J. , Schiffman Joshua D. , Shago Mary , Alexandrov Ludmil B. , Wunder Jay S. , Andrulis Irene L. , Malkin David , Behjati Sam , Shlien Adam
Published: August 2018

Looping together genes in cancer

A subset of human cancers are characterized by aberrant fusion of two specific genes. In some cases, the activity of the resultant fusion protein drives tumor growth. Most fusion genes in cancer appear to arise from simple reciprocal chromosomal translocations. Anderson
et al.
found that the characteristic fusion gene in a bone and soft tissue tumor called Ewing sarcoma is produced by a far more complicated mechanism (see the Perspective by Imielinski and Ladanyi). In nearly half of the tumors examined, the fusion gene was created by the formation of dramatic genomic loops that disrupt multiple genes. These complex rearrangements occur in early replicating and transcriptionally active regions of the genome and are associated with poor prognosis.

Science
, this issue p.
eaam8419
; see also p.
848
Increase in crop losses to insect pests in a warming climate
Authors: Deutsch Curtis A. , Tewksbury Joshua J. , Tigchelaar Michelle , Battisti David S. , Merrill Scott C. , Huey Raymond B. , Naylor Rosamond L.
Published: August 2018

Warming, crops, and insect pests

Crop responses to climate warming suggest that yields will decrease as growing-season temperatures increase. Deutsch
et al.
show that this effect may be exacerbated by insect pests (see the Perspective by Riegler). Insects already consume 5 to 20% of major grain crops. The authors' models show that for the three most important grain crops—wheat, rice, and maize—yield lost to insects will increase by 10 to 25% per degree Celsius of warming, hitting hardest in the temperate zone. These findings provide an estimate of further potential climate impacts on global food supply and a benchmark for future regional and field-specific studies of crop-pest-climate interactions.

Science
, this issue p.
916
; see also p.
846