bluuebunny/crossref_metadata_2025 huggingface dataset:
TRACING ORIGINS OF TWENTY‐FIRST CENTURY ECOTHEOLOGY: THE POETRY OF CHRISTOPHER SOUTHGATE
Authors: Rappaport Margaret Boone , Corbally Christopher
Published: August 2018

With the goal of better understanding how science, religion, and poetic art came together in the work of Christopher Southgate, the authors first explore his spiritual poetry. They come away with a better understanding of the author's commitment to a broad naturalism that contributes, along with his own faith experience, to his prose works in the emerging field of ecotheology. The authors conclude that Southgate's work is part of the worldwide emergence of a theological rationale that supports environmentalism, the protection of species, and the conservation of biodiversity. The authors find Southgate's poetry warm, appealing, accessible, and re‐readable to good effect, but with a thread of danger and warning throughout. Both features are quite appropriate for the environmental movement in the twenty‐first century.
RESPONSE WITH A SELECT BIBLIOGRAPHY
Authors: Southgate Christopher
Published: August 2018

In this response to the articles in this issue, Southgate considers lessons to be learned in respect of science–religion teaching, and about his edited textbook God, Humanity and the Cosmos. He emphasizes the importance of collaborative work in theology. He then considers issues in evolutionary theodicy raised by other contributors, especially eschatology, divine passibility, and the status of the “only way” explanation of evolutionary suffering. Lastly, he engages with critiques of his work based on a preference for characterizing the disvalues of creation in terms of “mysterious fallenness.” The article is followed by a select bibliography of his published work since 1979.
How Mental Health Clinicians Can Address Issues of Diversity with Incarcerated Individuals
Authors: M.S. MFT Eman Tadros
Published: August 2018

Mental Health Clinicians are accustomed to being confronted with not only difficult situations, but difficult conversations. Although discussing issues of diversity can be challenging, these dialogues are vital to the therapeutic process. In order to work under a multicultural framework, a clinician must minimally have basic knowledge on the culture of the client(s) being treated. Therapists are to use culturally appropriate intervention strategies and be mindful of the rules of the client’s culture. It is advised to work with the client(s) to define their culture, what it means to them, and what it means to society. It is the duty of a clinician to exemplify this for clients and give clients the power, permission, and invitation that they may believe they need, to do the same. This article discusses issues of diversity in the incarcerated system, clarifies the clinician’s role, and empowers clinicians to utilize multicultural techniques in treatment.
A New Educational Program to Improve Posture and Quality of Life Among Students by Means of the Feldenkrais Method and a New Program: MAP-Motion and Posture
Authors: Gil Iris
Published: August 2018

Newborns possess a natural ability for correct body posture, but most of us lose this ability to the extent of causing damage and consequently a decline in quality of life. Damage can be manifested in pain (mainly in the back), decline in functioning, and damage to emotional aspects of life. To examine the nature of the connection between body posture and quality of life by focusing on the question of whether and how practicing the well-known Feldenkrais method or the unknown Motion and Posture (MAP) method improves quality of life and body posture. The study was conducted among 243 students. An educational program for correct posture was conducted with physical exercises derived from both the Feldenkrais method and the new MAP method. The study employed a mixed-methods approach, and the tools utilized were two questionnaires, a digital inclinometer, Visual Analog Scale (VAS), and a metric tape measure. A positive trend of improvement was found both in the participants’ quality of life and posture. The qualitative measurement found a connection between improvement in quality of life and improvement in posture. The participants in the MAP program had an advantage over the participants in the Feldenkrais program. The innovation of the present study is in presenting the importance of posture for quality of life. This study is a new construct for understanding quality of life as a synergy between emotional and physical aspects that draws on improving posture by means of the Feldenkrais and MAP methods.
Combustion Simulation of Propane/Oxygen (With Nitrogen/Argon) Mixtures Using Rate-Controlled Constrained-Equilibrium
Authors: Yu Guangying , Metghalchi Hameed , Askari Omid , Wang Ziyu
Published: August 2018

The rate-controlled constrained-equilibrium (RCCE), a model order reduction method, has been further developed to simulate the combustion of propane/oxygen mixture diluted with nitrogen or argon. The RCCE method assumes that the nonequilibrium states of a system can be described by a sequence of constrained-equilibrium states subject to a small number of constraints. The developed new RCCE approach is applied to the oxidation of propane in a constant volume, constant internal energy system over a wide range of initial temperatures and pressures. The USC-Mech II (109 species and 781 reactions, without nitrogen chemistry) is chosen as chemical kinetic mechanism for propane oxidation for both detailed kinetic model (DKM) and RCCE method. The derivation for constraints of propane/oxygen mixture starts from the eight universal constraints for carbon-fuel oxidation. The universal constraints are the elements (C, H, O), number of moles, free valence, free oxygen, fuel, and fuel radicals. The full set of constraints contains eight universal constraints and seven additional constraints. The results of RCCE method are compared with the results of DKM to verify the effectiveness of constraints and the efficiency of RCCE. The RCCE results show good agreement with DKM results under different initial temperature and pressures, and RCCE also reduces at least 60% CPU time. Further validation is made by comparing the experimental data; RCCE shows good agreement with shock tube experimental data.
On the Interactions of a Rotor Blade Tip Flow With Axial Casing Grooves in an Axial Compressor Near the Best Efficiency Point
Authors: Chen Huang , Li Yuanchao , Katz Joseph
Published: August 2018

Experiments in a refractive index-matched axial turbomachine facility show that semicircular skewed axial casing grooves (ACGs) reduce the stall flowrate by 40% but cause a 2.4% decrease in the maximum efficiency. Aiming to elucidate mechanism that might cause the reduced efficiency, stereo-PIV measurements examine the impact of the ACGs on the flow structure and turbulence in the tip region near the best efficiency point (BEP), and compare them to those occurring without grooves and at low flowrates. Results show that the periodic inflow into the groove peaks when the rotor blade pressure side (PS) overlaps with the downstream end of the groove, but diminishes when this end faces the suction side (SS). Entrainment of the PS boundary layer and its vorticity generates a vortical loop at the entrance to the groove, and a “discontinuity” in the tip leakage vortex (TLV) trajectory. During exposure to the SS, the backward tip leakage flow separates at the entrance to the groove, generating a counter-rotating circumferential “corner vortex,” which the TLV entrains into the passage at high flowrates. Interactions among these structures enlarge the TLV and create a broad area with secondary flows and elevated turbulence near the groove's downstream corner. A growing shear layer with weaker turbulence also originates from the upstream corner. The groove also increases the flow angle upstream of the blade tip and varies it periodically. Accordingly, the circulation shed from the blade tip and strength of leakage flow increase near the blade leading edge (LE).
Thermomechanical Safety Analyses for a 238Pu Production Target at the HFIR
Authors: Hurt Christopher J. , Freels James D. , Jain Prashant K. , Ivan Maldonado G.
Published: August 2018

Safety analyses at the high flux isotope reactor (HFIR) are required to qualify irradiation of production targets containing neptunium dioxide/aluminum cermet (NpO2/Al) pellets for the production of plutonium-238 (238Pu). High heat generation rates (HGRs) due to a fertile starting material (237Np), low melting temperatures, and previously unstudied material irradiation behavior (i.e., swelling/densification, fission gas release) require a sophisticated set of steady-state thermal simulations in order to ensure sufficient safety margins. Experience gained from previous models for preliminary target designs is incorporated into a more comprehensive production target model designed to qualify a target for three cycles of irradiation and illuminate potential in-reactor behavior of the target.
Extremum Seeking for Plants With a Time-Varying Disturbance: Application to Photovoltaic Maximum Power Point Tracking
Authors: Kehs Michelle A. , Fathy Hosam K.
Published: August 2018

This paper presents an extremum seeking controller for photovoltaic maximum power point tracking (MPPT). The controller belongs to the broad family of “perturb and observe” algorithms, where the terminal voltage of a photovoltaic system is adjusted to maximize its output power. One critical challenge with these algorithms is that it can be difficult to distinguish between changes in photovoltaic power resulting from changes in irradiation versus the control input. With regard to this challenge, we develop an extremum seeking algorithm that uses least-squares estimation to explicitly separate the effect of the control input from the effect of time-varying disturbances. While the use of least-squares estimation in the context of extremum seeking is not new, our separation of time-varying effects is. In addition, our formulation retains much of the structure of traditional extremum seeking, thereby allowing us to perform a stability analysis comparable to the existing literature. This stability analysis assumes the time-varying disturbance to be slow, but we test the controller beyond this limit in simulation for photovoltaic MPPT. We compare our controller to two benchmarks (a similar controller that does not separate time-varying effects and a traditional extremum seeking controller), and our controller outperforms both.
Tribological Investigation of Multilayer Graphene Reinforced Alumina Ceramic Nanocomposites
Authors: Ahmad Iftikhar , Anwar Saqib , Xu Fang , Zhu Yanqiu
Published: August 2018

We investigated the wear resistance properties of high-frequency induction heat (HFIH) sintered alumina (Al2O3) ceramic nanocomposites containing various multilayer graphene (MLG) concentrations. The tribology of the monolithic Al2O3 and nanocomposites samples was assessed against spherical ceramic (Si3N4) counter sliding partner at sliding loads ranging from 6 to 40 N using ball-on-disk wear test configuration. Compared with the monolithic Al2O3, the incorporation of 1.0 vol % MLG reduced the friction coefficient by 25% and the wear rate by 65% in the MLG/Al2O3 nanocomposites tested under 40 N sliding load. Based on the mechanical properties, brittle index, and microstructure, the active wear mechanisms for the nanocomposites were analyzed. The MLG contributed in the nanocomposites tribology process, indirectly, by enhancing the mechanical properties and, directly, by reducing the friction between the counter sliding partners. The synergistic role of MLG thin triboflim and twirled MLG for improving the tribological performance of the nanocomposites is discussed.
Rheological and Film Forming Behavior of the Developed Nanocomposite Greases Under Elastohydrodynamics Lubrication Regime
Authors: Singh Jayant , Kumar Deepak , Tandon N.
Published: August 2018

Performance of grease lubricated point contact under elastohydrodynamics lubrication (EHL) regime is critical in many engineering applications. The present work deals with the evaluation of rheological, film forming characteristics and elastic recovery of newly developed nanocomposite greases. The nanocomposite greases are formulated by dispersing different nano-additives to bare grease (BG). The nano-additives include reduced graphene oxide (rGO) nanosheets, CaCO3 and α-Al2O3 nanoparticles. The microstructure evaluation of the nano-additives and different greases is done using high-resolution transmission electron microscopy (HRTEM). Estimation of the rheological parameters (storage and loss moduli) is done using rotational rheometer. The film forming behavior is recorded using elastohydrodynamic (EHD) rig for range of speed at different temperatures and constant load. The results indicate that change in microstructure due to nano-additive incorporation improves the responses of different greases. Based on rheological response, CaCO3 doped grease seems better but rGO doped grease is able to bear high shear stresses. Further, based on film forming characteristics and reflow or recovery behavior, rGO doped grease is better. The rGO-based grease registers approximately 90% elastic recovery followed by 75% for CaCO3-based grease, 65% for BG and 10% for α-Al2O3-doped grease.
The Role of Vortex Shedding in the Trailing Edge Loss of Transonic Turbine Blades
Authors: Melzer A. P. , Pullan G.
Published: August 2018

The loss of square, round, and elliptical turbine trailing edge geometries, and the mechanisms responsible, is assessed using a two-part experimental program. In the first part, a single blade experiment, in a channel with contoured walls, allowed rapid testing of a range of trailing edge sizes and shapes. In the second part, turbine blade cascades with a subset of sizes of the trailing edge geometries tested in part one were evaluated in a closed-loop variable density facility, at exit Mach numbers from 0.40 to 0.97, and exit Reynolds numbers from 1.5 × 105 to 2.5 × 106. Throughout the test campaign, detailed instantaneous Schlieren images of the trailing edge flows have been obtained to identify the underlying unsteady mechanisms in the base region. The experiments reveal the importance of suppressing transonic vortex shedding, and quantify the influence of this mechanism on loss. The state and thickness of the blade boundary layers immediately upstream of the trailing edge are of critical importance in determining the onset of transonic vortex shedding. Elliptical trailing edge geometries have also been found to be effective at suppressing transonic vortex shedding. For trailing edges that exhibit transonic vortex shedding, a mechanism is identified whereby reflected shed shockwaves encourage or discourage vortex shedding depending on the phase with which the shocks return to the trailing edge, capable of modifying the loss generated.
Surrogate Modeling of Manufacturing Variation Effects on Unsteady Interactions in a Transonic Turbine
Authors: Brown Jeffrey M. , Beck Joseph , Kaszynski Alexander , Clark John
Published: August 2018

This effort develops a surrogate modeling approach for predicting the effects of manufacturing variations on performance and unsteady loading of a transonic turbine. Computational fluid dynamics (CFD) results from a set of 105 as-manufactured turbine blade geometries are used to train and validate the surrogate models. Blade geometry variation is characterized with point clouds gathered from a structured light, optical measurement system and as-measured CFD grids are generated through mesh morphing of the nominal design grid data. Principal component analysis (PCA) of the measured airfoil geometry variations is used to create a reduced basis of independent surrogate model parameters. It is shown that the surrogate model typically captures between 60% and 80% of the CFD predicted variance. Three new approaches are introduced to improve surrogate effectiveness. First, a zonal PCA approach is defined which investigates surrogate accuracy when limiting analysis to key regions of the airfoil. Second, a training point reduction strategy is proposed that is based on the k–d tree nearest neighbor search algorithm and reduces the required training points up to 38% while only having a small impact on accuracy. Finally, an alternate reduction approach uses k-means clustering to effectively select training points and reduces the required training points up to 66% with a small impact on accuracy.
Nonisothermal Evaporation of Layers of Aqueous Salt Solutions
Authors: Misyura S. Y. , Morozov V. S.
Published: August 2018

Evaporation of layers of aqueous solutions of salts (LiBr, CaCl2, NaCl, MgCl2, BaCl2, and CsCl) is studied experimentally. Experimental data are compared with evaporation of the water layer. The solution is placed on a horizontal surface of a cylindrical heating section. Experiments on surface crystallization of salts are carried out. For aqueous solutions of salts LiBr, LiCl, and CaCl2, there is an extremum for the heat transfer coefficient αl. For water and for solutions of salts NaCl and CsCl, the extremum is absent. The first factor is a decreasing function of time, and the second factor is an increasing function of time. For the water layer, both factors continuously increase with time, and the maximum evaporation rate corresponds to the final stage of evaporation. The heat balance for interface layer is made up. The role of the free gas convection in the heat balance strongly depends on the salt concentration and varies with the rise of evaporation time. For low salt concentrations the influence of free convection in the gas phase on heat transfer in the liquid phase can be neglected; however, for high concentrations this effect is comparable with other factors. The curves for the rate of crystallization have been built. More than two time differences between the experiment and the calculation are associated with the kinetics of dendritic structures.
Modeling Machine Motion and Process Parameter Errors for Improving Dimensional Accuracy of Fused Deposition Modeling Machines
Authors: Lyu Jiaqi , Manoochehri Souran
Published: August 2018

The dimensional accuracy of fused deposition modeling (FDM) machines is dependent on errors caused by processing parameters and machine motions. In this study, an integrated error model combining these effects is developed. Extruder temperature, layer thickness, and infill density are selected as parameters of this study for three FDM machines, namely, Flashforge Finder, Ultimaker 2 go, and XYZ da Vinci 2.0 Duo. Experiments have been conducted using Taguchi method and the interactions between processing parameters are analyzed. Based on the dimensional deviations between fabricated parts and the computer aided design (CAD) geometry, a set of coefficients for the integrated error model are calculated to characterize each machine. Based on the results of the integrated error model, the original CAD geometry is optimized for fabrication accuracy on each machine. New parts are fabricated using the optimized CAD geometries. Through comparing the dimensional deviations of parts fabricated before and after optimization, the effectiveness of the integrated error model is analyzed and demonstrated for the three FDM machines.
Design and Validation of a Heart Rate and Speed Monitoring Device With Intelligently Controlled Assistive Rehabilitation Elliptical
Authors: Pfeifer Chase M. , Rowen Douglas A. , Buster Thad W. , Cesar Guilherme M. , Irons Sonya L. , Burnfield Judith M.
Published: August 2018

Cardiovascular assessment and fitness training are often overlooked in physical rehabilitation. Many current rehabilitation exercise devices do not allow for the recording and exportation of variables related to cardiovascular fitness. Therefore, the purpose of this work was to design, prototype, and validate a data logger that measures, records, and exports time, heart rate (HR), and speed data with the commercially available rehabilitation device called the Intelligently Controlled Assistive Rehabilitation Elliptical (ICARE). Validation involved using the data logger device in parallel with devices currently used in research environments for measuring HR (TrueOne 2400 metabolic cart with polar HR monitoring chest strap) and speed (ICARE's console). Ten healthy individuals without known disability impacting walking or ability to use the ICARE, exercised on the ICARE while HR and ICARE speed were measured. It was found that the data logger can be used to accurately measure, record, and export HR (linear regression: P < 0.001; R2 = 0.892) and speed (linear regression: P < 0.001; R2 = 0.997) data when used with the ICARE.
Numerical Investigation of Fluid Flow Parameters in a Combustor Simulator
Authors: Barhaghi Darioush G. , Hedlund Lars
Published: August 2018

In recent years computational fluid dynamics (CFD) is substantially employed in the design process of gas turbines. To increase the performance of the turbines an efficient cooling system design is essential. This is largely dependent on the accuracy of the predicted temperature at the exit of the combustor. Lack of accuracy of the predicted temperature at the combustor-turbine interface results in using large safety factors which affect the performance negatively.

It is believed that the RANS methods are incapable of predicting the mixing process in highly swirling flows in the combustors. In this study the flow in a none-reactive model combustor simulator is investigated numerically using RANS, SAS and LES turbulence models in ANSYS CFX code. The model combustor consists of three swirling mixers through which the hot air passes. The cold air that goes through many small effusion holes of the outer and inner liners mixes up with the swirling hot air. The computational domain however consists only of one sector and periodic boundary condition is applied in the circumferential direction.

The numerical results are compared with the experimental results that are provided by the University of Florence as part of the European FACTOR project. It is confirmed that the RANS or URANS methods are not capable of reproducing the experimental results.
Design of a Transonic High Flow Coefficient Centrifugal Compressor by Using Advanced Design Methods
Authors: Wittrock David , Reutter Oliver , Nicke Eberhard , Schmidt Thomas , Klausmann Jan
Published: August 2018

A high flow coefficient centrifugal compressor was designed in a joint cooperation of DLR and MAN Diesel & Turbo SE Berlin. The main goal of this work is to increase the flow coefficient in the aerodynamic design point by 20% in comparison to the reference design. Besides a significant increase in flow coefficient, isentropic efficiency should be at least equal to the reference design. Design methods of the last decades are not able to reach a high flow coefficient without a reasonable compromise in efficiency. Furthermore, common design methods introduce splitter blades to gain a higher flow coefficient. Usually splitter blades lead to structural mechanical issues by introducing different eigenfrequencies. Reference impeller and vaned diffuser as well as the main design goals and constraints are provided by MAN Diesel & Turbo SE Berlin. DLR performed the design studies using their in-house design suite including TRACE as the CFD solver, PERMAS as the CSM program and AutoOpti for the multiobjective optimization tool. In preliminary design investigations it was found that a reduction of blade and vane number is necessary to avoid diffuser choking at high flow coefficients. Finally, a favorable geometry is chosen for a future test rig configuration at MAN Diesel & Turbo SE Berlin. The new design works totally in transonic conditions. The selected design fulfills all aerodynamic and structural mechanical design goals.
Experimental and Numerical Investigations of Characteristics of an Axial Jet in the Vicinity of a Confined Concentric Swirl Flow in a Model Combustor
Authors: Bhagwan R. , Habisreuther P. , Zarzalis N.
Published: August 2018

Gas turbine combustion engineers strive to obtain high flame stability at low power conditions (idle); whereas good emissions characteristics are desired at high power conditions. Although lean combustors provide good emissions characteristics, they suffer from the issue of poor flame stability. Often a pilot flame along with a lean main flame is used in order to improve flame stability issue. Positioning of an axial jet concentric to a swirl jet is one of commonly used configurations for a pilot flame. The interaction between both co-annular jets leads to distinct flow patterns in the combustor and subsequently the flame structure is impacted. If the axial jet is able to penetrate the inner recirculation zone (IRZ) generated by the swirled flow of the main jet, then a jet type of flame is obtained. The jet flame in vicinity of co-annular swirled flow is also denoted as type 1 flame, and is known to have good flame stability. On the other hand, if the pilot jet is not able to penetrate the IRZ, then the recirculating type of flame is obtained. A recirculating flame type has good emissions characteristics but suffers from poor flame stability. In this work the numerical predictions have been performed to gain more insight into occurrences of these two different flame structures which have been experimentally recorded. Using ANSYS Fluent CFD software, non-reactive steady state turbulent flow simulations have been performed to understand the flow and mixing field in a 3D combustor. Laser Doppler Anemometry (LDA) and hydroxyl radical (OH*) chemiluminescence have been used to measure the flow and characterize the flame structure, respectively.
Aerodynamic Design of a Ported Shroud Casing Treatment for a Turbocharger Compressor of a Miller-Cycle Gasoline Engine
Authors: Schäfer Christoph , Bogner Mathias , Ehrhard Jan , Dunzer Matthias
Published: August 2018

The emission laws for internal combustion engines become more and more strict. Therefore, new concepts have to be implemented. In the so called Miller approach the intake valve is closed before the intake stroke is finished, thus resulting in a lower combustion end temperature and pressure. As a negative result, the specific power of the engine is reduced. This disadvantage has to be compensated by an increased boost pressure delivered by a turbocharger compressor. For the turbomachinery this means for low end torque engine operation a compressor operating point at high pressure ratio and low mass flow. Thus an increased risk for surge results.

A cost-effective measure to establish an utilizable compressor map in this regime is a ported shroud casing treatment. Here, a circumferential cavity connects the low channel at the inducer with the compressor housing inflow, allowing fluid to recirculate at low mass flows. Thereby, the gross inducer mass flow is increased, the flow stabilized and hence the surge line improved. In this paper, a ported shroud casing treatment is developed employing CFD. The aim is to improve the surge line as well as the stability of the compressor characteristics and to minimize the impact on compressor efficiencies at high flows as well as the acoustic behaviour at the same time. In order to validate the performance of the design, standard hot gas measurements as well as acoustic measurements are conducted and analyzed.

Furthermore, the impact of a commonly applied 90° inflow bend on the performance of the ported shroud cavity is investigated by experimental data.
Incidence Effect on the Aero-Thermal Performance of a Film Cooled Nozzle Vane Cascade
Authors: Abdeh H. , Barigozzi G. , Perdichizzi A. , Henze M. , Krueckels J.
Published: August 2018

In the present paper, the influence of inlet flow incidence on the aerodynamic and thermal performance of a film cooled linear nozzle vane cascade is fully assessed. Tests have been carried out on a solid and a cooled cascade. In the cooled cascade, coolant is ejected at the end wall through a slot located upstream of the leading edge plane. Moreover, a vane showerhead cooling system is also realized through 4 rows of cylindrical holes. The cascade was tested at a high inlet turbulence intensity level (Tu1 = 9%) and at a constant inlet Mach number of 0.12 and nominal cooling condition, varying the inlet flow angle in the range ±20°. The aero-thermal characterization of vane platform was obtained through 5-hole probe and end wall adiabatic film cooling effectiveness measurements. Vane load distributions and surface flow visualizations supported the discussion of the results. A relevant negative impact of positive inlet flow incidence on the cooled cascade aerodynamic and thermal performance was detected. A negligible influence was instead observed at negative incidence, even at the lowest tested value of −20°.
Modelling Strategies to Obtain the Forcing Function for a Forced Response Analysis
Authors: Connell Stuart , Zori Laith , Patil Sunil
Published: August 2018

The forced response analysis of a turbomachinery component requires the transient pressure field over that component. For an accurate prediction, this pressure field or forcing function needs to contain the frequency signatures of adjacent components. This paper compares various efficient modelling strategies to include the effect of these adjacent components in obtaining this pressure field. The example used in this work is a hydro turbine though the strategies could be applied to other turbo machines.

The Hydro turbine example comprises a spiral casing (or a volute), inlet guide vanes, stay vanes and a rotating runner. The pitch ratio between the guide vanes and runner is 14:15. The desire is to compute the unsteady pressure field in the runner domain. The flow solver employed has a variety of simulation techniques available to compute flows in cases with unequal numbers of blades/vanes in adjacent rows (“unequal pitch”). These techniques, range from mixing plane and frozen rotor methods for steady flows to various transformation methods for unsteady flows. The transformation methods remove the need for large full or part wheel calculations. Therefore, solution can be obtained at fraction cost of the full wheel simulation. The Fourier transform method is used in this paper to model the pitch change between stator and rotor. Three transient pitch-change modelling strategies are presented, and its accuracy and solution efficiency are compared to full wheel simulation. The three pitch-change variations are: a single-frequency frozen gust analysis, a blade coupling between runner and guide vanes using pitch-change interface, and multiple-frequency frozen gust analysis which will account for the asymmetry due to presence of the spiral casing.
Measured Thermodynamic Effect of Wet Gas Compression
Authors: Simons Sarah , Cater Ryan , Brun Klaus , Musgrove Grant , Kurz Rainer
Published: August 2018

Significant work has been performed to qualify and quantify the effects of operating with wet gas in a centrifugal compressor system [1, 2]. Of particular interest is the sharp decrease in the isentropic efficiency of the machine when operating with process gas containing various liquid volume fractions. However, it is unknown how much of the performance losses are due to aerodynamic effects, such as blade profile and flow separation losses, rather than the basic thermodynamic effects of compressing a multiphase gas that has a higher density, integral wet-cooling, and contains small amounts of high-density droplets. Previous studies showed that the overall efficiency losses exceeded those expected from purely thermodynamic effects so aerodynamic effects have been principally blamed for the lower efficiency. However, no test data exists in the public domain that quantifies these losses and it is experimentally difficult to perform this type of testing in centrifugal compressor.

Therefore, a series of tests was performed on a reciprocating compressor with power and efficiency recorded through dynamic pressure measurements obtained inside the compression cylinder, torque measured on the shaft, and enthalpy rise measurements obtained outside the cylinders. Using this approach one can eliminate (or differentiate) the aerodynamic effects of wet gas compression, such as valve losses, thus allowing the direct determination of the thermodynamic losses of wet gas compression. Specifically, when there is multi-phase flow entering the machinery, there is the thermodynamic effect of how a mixture of water and air behaves when being compressed [from a process perspective] and the aerodynamic effect of moisture encountering the blades of a centrifugal compressor [performance loss] or the valve passages of a reciprocating compressor [pressure loss]. Directly instrumenting the internals of a reciprocating compressor cylinder allows the evaluation of the thermodynamic performance of multi-phase compression separate from any aerodynamic penalties.

This paper describes the tests performed in a reciprocating compressor open test loop operating with varying amounts of liquid volume fractions (LVFs) of water in the process gas (air). The data was reduced using Pressure-Volume card measurements inside and outside the cylinder, enthalpy rise, as well as torque to determine the impact of volume fraction on compression power and efficiency. Additionally, the valve losses, system efficiencies, and peak compression “spike” were evaluated in relations to the LVFs.
Isothermal Oxidation of René N5 at 1150°C
Authors: Walker Megan , Huang Xiao
Published: August 2018

In this study, single crystal superalloy René N5 was exposed in air at 1150 °C for up to 16 hours to evaluate the alloy’s short-term oxidation behaviour and the potential for developing a no-bond coat TBC system. The results showed that after 1 hour of exposure, a three layered oxide developed on the surface, consisting of spinel, Ta-containing oxide and alumina just above the substrate. After 4 hours of exposure, oxide spallation occurred; this became more pronounced after 16 hours. The oxide spallation took place between the top spinel layer and alumina layer, where Ta-rich oxide was more abundant. All samples tested for 0.5, 1, 2, 4 and 16 hours developed alumina near the substrate while the occurrence of NiO, spinel and Ta-oxides varied, depending upon the exposure time.
A Physically Consistent Reduced Order Model for Plasma Aeroelastic Control on Compressor Blades
Authors: Motta Valentina , Malzacher Leonie , Peitsch Dieter , Quaranta Giuseppe
Published: August 2018

Plasma actuators may be successfully employed as virtual control surfaces, located at the trailing edge of blades, both on the pressure and on the suction side, to control the aeroelastic response of a compressor cascade. Actuators generate an induced flow against the direction of the freestream. As a result, actuating on the pressure side yields an increase in lift and nose down pitching moment, whereas the opposite is obtained by operating on the suction side. A properly phased alternate pressure/suction side actuation allows to reduce vibration and to delay the flutter onset. This paper presents the development of a linear frequency domain reduced order model for lift and pitching moment of the plasma-equipped cascade. Specifically, an equivalent thin airfoil model is used as a physically consistent basis for the model. Modifications in the geometry of the thin airfoil are generated to account for the effective chord and camber changes induced by the plasma actuators, as well as for the effects of the neighboring blades. The model reproduces and predicts correctly the mean and the unsteady loads, along with the aerodynamic damping on the plasma equipped cascade. The relationship between the parameters of the reduced order model with the flow physics is highlighted.
Fixed Area Nozzle With Free Power Turbine: What Makes the Match?
Authors: Baig Muhammad Nadeem , Noman Muhammad , Hayat Nasir
Published: August 2018

The matching of free power turbine with gas producer/generator turbine in a twin shaft industrial gas turbine configuration is a complex fluid interaction with the fact that maximum output must be achieved at fully choked nozzle segments while fixing the compressor and gas producer turbine pressure ratios. The paper presents characteristics of different turbo-machines with power turbine chiefly the matching of fixed area nozzle with low Wobbe Index Fuels. It also addresses the peculiar behavior of bleed valve, control limits, power as well as correlation of low Wobbe Index fuels. Mechanically, the gas producer/generator turbine and power turbine are independent in twin shaft gas turbines for oil and gas applications; i.e., the speed of free power turbine is controlled by driven equipment like pump or compressor similar to single shaft gas turbine generator set applications. The only contact remains between them is burnt gases generated by Gas producer Turbine. The full/optimum power will be obtained with correct aerodynamic matching of free power turbine at different match temperatures. The paper describes how turbine rotor inlet temperature ‘TRIT’ can be controlled by fixing discharge pressure of axial flow compressor, gas producer speed, flow through first power turbine nozzle etc. Important fluid phenomenon, the high TRIT in fully choked nozzle and bleed valve closing delay at high ambient match will be discussed in more detail. Last but not least, a correction factor is introduced by mathematical correlation of fixing the exit area of nozzles with complex calculations performed for low Wobbe index fuels keeping in view the match temperature.
Investigation on a Blockerless Cascade Thrust Reverser System Based on Response Surface Method
Authors: Zhou Li , Wang Zhanxue , Shi Jingwei , Zhang Xiaobo
Published: August 2018

The blockerless cascade thrust reverser is one of the innovative thrust reverser systems, which replaces the traditionally mechanical blocker door with the aerodynamic blocker door by high-pressure secondary injection, thus significantly reduces the nacelle weight and the complexity of the actuator, and especially suitable for high-bypass-ratio turbofan engine. In order to obtain the optimum performance of a blockerless cascade thrust reverser system and provide the guidance for the design of the blockerless cascade thrust reverser system, a blockerless cascade thrust reverser system was studied in this paper based on the Response Surface Method (RSM), focusing on the effect of different geometric and aerodynamic parameters on the thrust reverser performance. Results show that the secondary injection with high pressure forms the blockage effect to the fan flow, then forces the fan flow to deflect and discharge from the cascade window, realizing the reverse thrust. The thrust reverser performance is mainly affected by fan pressure ratio (FPR), secondary flow pressure ratio (SPR), secondary injection position (Xjet), secondary injection angle (αjet) and cascade installation angle (β), and the dominated factors are FPR, SPR and Xjet. According to the obtained response equation of the thrust reverser performance, the relationship between reverse thrust efficiency and various parameters are clearly described, and performance of thrust reverser can be quickly evaluated. Significant interaction effects exist between different two factors, which must be taken into consideration in the design process of the blockerless cascade thrust reverser system, especially for the interaction effect between FPR and Xjet, interaction effect between FPR and β. Optimization design with objective of maximum reverse thrust was carried out to determine the best parameter settings, and reverse thrust ratio ηTrev of 60% is achieved under the constraint of the secondary flow ratio.
Advanced Numerical Simulation of Turbine Rim Seal Flows and Consideration for RANS Turbulence Modelling
Authors: Gao Feng , Poujol Nicolas , Chew John W. , Beard Paul F.
Published: August 2018

This paper reports large-eddy simulations (LES) and unsteady Reynolds-averaged Navier-Stokes (URANS) calculations of a turbine rim seal configuration previously investigated experimentally. The configuration does not include any vanes, blades or external flows, but investigates inherent unsteady flow features and limitations of CFD modelling identified in engine representative studies. Compared to RANS and URANS CFD models, a sector LES model showed closer agreement with mean pressure measurements. LES models also showed agreement with measured pressure frequency spectra, but discrepancies were found between the LES and experiment in the speed and the circumferential lobe number of the unsteady flow structures. Sensitivity of predictions to modelling assumptions and differences with experimental data are investigated through CFD calculations considering sector size, interaction between the rim cavity and the inner cavity, outer annulus boundary conditions, and the coolant mass flow. Significant sensitivity to external flow conditions, which could contribute to differences with measurements, is shown, although some discrepancies remain. Further detailed analysis of the CFD solutions is given illustrating the complex flow physics. Possible improvement of a steady RANS model using a priori analysis of LES was investigated, but showed a rather small improvement in mean pressure prediction.
Comparative Study of a Felt Abradable Seal
Authors: Hasnedl Dan , Epikaridis Premysl
Published: August 2018

In turbo-machinery, abradable layers are used to protect sensible components while keeping minimal possible clearances for maximum efficiency. This article describes the experimental comparison of state of the art abradable layers used as steam turbine seals and a new type of abradable layer made of a metallic felt. The comparison is done via abradability and leakage testing. The leakage is also compared to a state of the art analytical formula to show the effect on the thermal cycle calculation.

An abradable test rig is presented together with the test method. Test results show the value of the Felt seal compared to other two types at low contact speed area.

A steam test rig is also presented. Seal leakage at real operating conditions is evaluated and compared to an analytical formula. The leakage results show some efficiency gap compared to other two types of seals.
Effects of Mushroom-Shaped Tooth Wear on the Leakage Performance and Rotordynamic Coefficients of Labyrinth Seals
Authors: Chen Yaoxing , Li Zhigang , Yan Xin , Li Jun
Published: August 2018

The leakage performance and rotordynamic coefficients of the labyrinth seal are changed when a mushroom-shaped tooth wear occurs in actual transient operation resulting from rubbing and wear between stator teeth and the rotor. The objective of current study was to numerically investigate and characterize the variation of the leakage performance and rotordynamic coefficients as a result of an increased mushroom-shaped tooth wear at two typical inlet preswirl velocities and enhance the rotor stability of the after-damage labyrinth seal. In this paper, the Unsteady Reynolds-Averaged Navier-Stokes (URANS) solution based on the multi-frequency elliptical orbit rotor whirling mode and dynamic mesh technique was used to calculate the leakage flow rates and rotordynamic coefficients of the labyrinth seal with an unworn clearance and three after-damage clearances at two inlet preswirl velocities. The accuracy and availability of adopted transient computational methods in this work were validated by the published experimental data. Also, the influence of tooth mushroom radius and each cavity in the labyrinth seal on the rotor stability and some approaches to improve the rotor stability were discussed and conducted.

The conclusion shows that the leakage flow rate increases with an increase in the clearance, and a linear increase is expected when the after-damage clearance is over 0.4 mm. An increase in the after-damage clearance always leads to a drop in the effective damping or an increase in crossover frequencies. Also, the additional tooth mushroom radius plays an important role in the effective damping or crossover frequency and can not be neglected. The upstream cavity always possesses lower crossover frequency, and a drop of 9.9 Hz in the crossover frequency is found when the seal entrance axially extends 5 mm. In addition, the crossover frequency is decreased from 243.5 Hz to 164.2 Hz when typical anti-swirl brakes are installed in this labyrinth seal with the worn mushroom-shaped teeth.
Effects of the Location of the Pocket Cavity on Heat Transfer and Flow Characteristics of the Endwall With a Symmetrical Vane
Authors: Liu Jian , Hussain Safeer , Wang Lei , Xie Gongnan , Sundén Bengt
Published: August 2018

A pocket cavity is generated at the junction position of the Low Pressure Turbine (LPT) and the Outlet Guide Vane (OGV) in the rear part of a gas turbine engine. The OGV mainly controls the exhaust flow exiting and provides structural strength of the main engine frame. In the present work, the effect the location of the pocket on the heat transfer of the endwall with a symmetrical vane is investigated. A triangular pocket cavity is built in a rectangular channel and a symmetric vane is put on the endwall downstream of the pocket cavity. Heat transfer and turbulent flow characteristics over the endwall are investigated experimentally and numerically. The distance between the pocket cavity and the symmetrical vane is varied from 10 cm, 15 cm, and 20 cm. Liquid Crystal Thermography (LCT) is employed to measure the heat transfer over the endwall at Reynolds number ranging from 87,600 to 219,000. The turbulent flow details are presented by numerical calculations with the turbulence models, i.e., the k-ω SST model. From this study, high heat transfer regions are usually found at where flow impingement appears, i.e., the pocket boundary edge region and the vane head region. Compared with the case of the smooth channel, the heat transfer is decreased when a pocket cavity is placed upstream of the vane. With the distance between the pocket cavity and the vane becoming larger, the effect of the pocket cavity is weakened and the heat transfer is approaching the smooth channel case, i.e., case 0. The pocket cavity strengthens the flow shedding and separates the flow away from the endwall. The pushed upward flow weakens the flow impingement on the vane and then leads to the decreased heat transfer around the vane.
A Study of Dynamic Phenomena Caused by Impulse Mistuning in Case of Self-Excitation
Authors: Müller Peter , Hartung Andreas , Hackenberg Hans-Peter
Published: August 2018

Further reduction of vibratory stresses of blades and vanes using an appropriate damping system is required whenever the total damping of the stage is insufficient to avoid High Cycle Fatigue during the life of the blades. An alternative to standard friction based damping systems are impulse mistuning systems — a kind of vibration impact induced non-linear energy sink. Previous publications introduced impulse mistuning systems for avoidance of HCF caused by forced synchronous vibrations of blades and vanes. This included the development of the system, analytical predictions of the effectiveness as well as experimental validation. The effectiveness of the impulse mistuning systems in the case of self-excitation (e.g. flutter) has not been investigated yet to the knowledge of the authors. In this paper, a numerical study of the dynamic phenomena taking place in lumped-parameter models with negative damping and different impulse mistuning systems is presented. One of the results shown is that energy transfer takes place, whereby the vibration initiates at one mode and after some time gets transferred into higher vibration at another mode.