bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐term outcomes of domiciliary intravenous iloprost in idiopathic and connective tissue disease‐associated pulmonary arterial hypertension
Authors: Ramjug Sheila , Hussain Nehal , Hurdman Judith , Elliot Charlie A. , Sabroe Ian , Armstrong Iain J. , Billings Catherine , Hamilton Neil , Kiely David G. , Condliffe Robin
Published: September 2016

Background and objective

There are few published data on the efficacy of i.v. iloprost in pulmonary arterial hypertension (PAH). We present long‐term outcomes in PAH patients receiving i.v. iloprost in a large UK referral centre.

Methods

Eighty patients with idiopathic PAH (iPAH, n = 46) or PAH associated with connective tissue disease (CTD‐PAH, n = 34) were identified as receiving domiciliary i.v. iloprost between January 1999 and April 2015. Baseline characteristics, doses achieved, functional class at follow‐up and survival data were retrieved from hospital databases.

Results

Median maximum dose achieved was 4.6 ng/kg/min in the iPAH group and 5.0 ng/kg/min in CTD‐PAH patients. Exercise capacity significantly improved in the first 6 months of therapy in IPAH patients. Overall 1‐, 3‐ and 5‐year survival was 78%, 64% and 52% in iPAH (P = 0.002) and 64%, 26% and 21% in CTD‐PAH. Independent predictors of survival were age and exercise capacity.

Conclusion

We report improved survival to that previously reported in iPAH patients treated with domiciliary i.v. iloprost. This may be in part related to higher administered doses. Patients with CTD‐PAH had poorer survival, reinforcing the need for early transplantation referral in suitable patients.
Information Presentation in Decision and Risk Analysis: Answered, Partly Answered, and Unanswered Questions
Authors: Keller L. Robin , Wang Yitong
Published: September 2016

For the last 30 years, researchers in risk analysis, decision analysis, and economics have consistently proven that decisionmakers employ different processes for evaluating and combining anticipated and actual losses, gains, delays, and surprises. Although rational models generally prescribe a consistent response, people's heuristic processes will sometimes lead them to be inconsistent in the way they respond to information presented in theoretically equivalent ways. We point out several promising future research directions by listing and detailing a series of answered, partly answered, and unanswered questions.
European Civic Neighbourhood: Towards a Bottom‐Up Agenda Across Borders
Authors: Laine Jussi
Published: September 2016

The EU's borderland between Finland and Russia provides a fascinating setting to study how different understandings of state and civil society meet, overlap, and fuse. Focusing on this border region, this study pits the conventional bilateral framework against the more recent EU one in depicting a cross‐border space for civic activity. It offers a critical perspective on the official European Neighbourhood and illustrates a complementary vision of a non‐territorial civic neighbourhood seeking to capture the networked and fluid topologies of contemporary cross‐border processes. The paper underlines the role of civil society in bridging the gaps created by borders, and suggests that they provide a powerful driver for maintaining neighbourly relations in a tense climate. To better understand the transnational network‐space they fashion, we must abandon the geographical idea of territorial exceptionality and be receptive to alternative interpretations not tied to a particular policy framework and the restrictions defined by it.
Regional Innovation Systems or Innovative Regions? Evidence from Italy
Authors: De Marchi Valentina , Grandinetti Roberto
Published: September 2016

The literature on regional innovation systems (RIS) has focused so far just on a few exemplary cases of regions where innovation resulted from systemic interactions between firms and institutions. This paper aims at evaluating quantitatively which regions can be considered RIS using Community Innovation Survey data on Italy. The analysis reveals a new geography of innovation in the country as compared to results emerging from studies on the 1990s, suggesting a high dynamism in innovation capabilities of Italian regions. Four clusters of regions are identified, but none of them can be described as a true RIS: the most innovative ones lack ‘systemicness’ and those that come closest to the RIS model have not the best innovative performance.
The Challenge of the Dutch Port‐City Interface
Authors: A. Daamen Tom , Louw Erik
Published: September 2016

This paper explores the shifting geography of the port‐city interface in The Netherlands since the mid 1970s, and assesses its current scene. With an eye on port‐urban governance and planning, we provide a dynamic account of the forces that have played a major role in the implementation of waterfront redevelopment schemes in Amsterdam and Rotterdam. Our account shows that the power balance between the port authority, the municipal planning office, and the users of the port has shifted. This has compelled urban planners in both port cities to adopt a more incremental waterfront development strategy than they had anticipated, and has given port users more influence on the plans for the current port‐city interface.
Positivity properties of the bundle of logarithmic tensors on compact Kähler manifolds
Authors: Campana Frédéric , Păun Mihai
Published: September 2016

Let $X$ be a compact Kähler manifold, endowed with an effective reduced divisor $B=\sum Y_{k}$ having simple normal crossing support. We consider a closed form of $(1,1)$-type $\unicode[STIX]{x1D6FC}$ on $X$ whose corresponding class $\{\unicode[STIX]{x1D6FC}\}$ is nef, such that the class $c_{1}(K_{X}+B)+\{\unicode[STIX]{x1D6FC}\}\in H^{1,1}(X,\mathbb{R})$ is pseudo-effective. A particular case of the first result we establish in this short note states the following. Let $m$ be a positive integer, and let $L$ be a line bundle on $X$, such that there exists a generically injective morphism $L\rightarrow \bigotimes ^{m}T_{X}^{\star }\langle B\rangle$, where we denote by $T_{X}^{\star }\langle B\rangle$ the logarithmic cotangent bundle associated to the pair $(X,B)$. Then for any Kähler class $\{\unicode[STIX]{x1D714}\}$ on $X$, we have the inequality $$\begin{eqnarray}\displaystyle \int _{X}c_{1}(L)\wedge \{\unicode[STIX]{x1D714}\}^{n-1}\leqslant m\int _{X}(c_{1}(K_{X}+B)+\{\unicode[STIX]{x1D6FC}\})\wedge \{\unicode[STIX]{x1D714}\}^{n-1}.\end{eqnarray}$$ If $X$ is projective, then this result gives a generalization of a criterion due to Y. Miyaoka, concerning the generic semi-positivity: under the hypothesis above, let $Q$ be the quotient of $\bigotimes ^{m}T_{X}^{\star }\langle B\rangle$ by $L$. Then its degree on a generic complete intersection curve $C\subset X$ is bounded from below by $$\begin{eqnarray}\displaystyle \biggl(\frac{n^{m}-1}{n-1}-m\biggr)\int _{C}(c_{1}(K_{X}+B)+\{\unicode[STIX]{x1D6FC}\})-\frac{n^{m}-1}{n-1}\int _{C}\unicode[STIX]{x1D6FC}.\end{eqnarray}$$ As a consequence, we obtain a new proof of one of the main results of our previous work [F. Campana and M. Păun, Orbifold generic semi-positivity: an application to families of canonically polarized manifolds, Ann. Inst. Fourier (Grenoble) 65 (2015), 835–861].
Fixed-Order Decoupling of Interval Plant Families
Authors: Negim Mostafa , Nobakhti Amin
Published: September 2016

A method for the reduction of interactions in linear time invariant (LTI) multivariable uncertain systems is proposed. An H∞-norm metric is proposed for the assessment of interactions in interval uncertain multiple-input multiple-output (MIMO) plants. Based on this, a procedure for the design of fixed-order dynamic decoupling precompensators for MIMO plants with interval uncertainty is outlined which can be solved using efficient solvers such as cvx. The proposed methodology is used to develop a low-order robust multivariable controller for voltage and frequency control of an islanded distributed generation (DG) unit.
An Experimental Investigation of the Permeability in Porous Chip Formed by Micropost Arrays Based on Microparticle Image Velocimetry and Micromanometer Measurements
Authors: Wang Haoli , Wang Pengwei
Published: September 2016

Measurements of velocity and pressure differences for flows in porous chip fabricated with micropost arrays arranged in square pattern were implemented by using micro-particle image velocimetry (micro-PIV) and high precision micromanometer. Based on the measurement results, the permeability was solved by Brinkman equation under the averaged velocities over the cross section, two-dimensional velocities on the center plane of the microchannels, and the averaged velocities on the center plane considering the effect of depth of correlation (DOC), respectively. The experimental results indicate that the nondimensional permeability based on different velocities satisfies the Kozeny–Carman (KC) equation. The Kozeny factor is taken as 40 for the averaged velocity over the cross section and 15 for two kinds of center velocities based on the micropost array of this study, respectively. The permeability calculated by the velocities on the center plane is greater than that by the averaged velocity over the cross section.
Pressure Drop Through Orifices for Single- and Two-Phase Vertically Upward Flow—Implication for Metering
Authors: Zeghloul Ammar , Azzi Abdelwahid , Saidj Faiza , Messilem Abdelkader , Azzopardi Barry James
Published: September 2016

Pressure drop has been measured for upward single- and two-phase gas–liquid flow across an orifice in a vertical pipe. A conductance probe provided average void fraction upstream of the orifice. Six orifices with different apertures/thickness were mounted in turn in a 34 mm diameter transparent acrylic resin pipe. Gas and liquid superficial velocities of 0–4 m/s and 0.3–0.91 m/s, respectively, were studied. For single-phase flow, pressure drop, expressed as an Euler number, was seen to be independent of Reynolds number in turbulent region. The Euler number increased with decreasing the open area ratio/orifice thickness and increasing velocity. The pressure drop was well predicted by the correlation of Idel'chik et al. (1994, Handbook of Hydraulic Resistances, 3rd ed., CRC Press, Boca, Raton, FL.), which uses a form of Euler number. The corresponding two-phase flow pressure drop depends on the flow pattern. Decreasing open area ratio/orifice thickness increased the pressure drop. For a given liquid superficial velocity, the pressure drop increases with gas superficial velocity except for low open area ratio where this increase is followed by a decrease beyond a critical superficial gas velocity for the high liquid superficial velocities. Relevant correlations were assessed using the present data via a systematic statistical approach. The two-phase multiplier equations of Morris (1985, “Two-Phase Pressure Drop Across Valves and Orifice Plates,” European Two Phase Flow Group Meeting, Marchwood Engineering Laboratories, Southampton, UK.) and Simpson et al. (1983, “Two-Phase Flow Through Gate Valves and Orifice Plates,” International Conference on Physical Modelling of Multiphase Flow, Coventry, UK.) are the most reliable ones.
First Step Toward the Codesign of Planing Craft and Active Control Systems
Authors: Castro-Feliciano Esteban L. , Sun Jing , Troesch Armin W.
Published: September 2016

This paper takes a novel approach to the design of planing craft with active control systems (ACS) by codesigning the longitudinal center of gravity (lcg) and ACS, and compares its performance with a vessel where the lcg and ACS are designed sequentially (traditional approach). The vessels investigated are prismatic in shape. The ACS are modeled as forces on the vessel. The ACS controller is a linear quadratic regulator (LQR) designed using a reduced-order model of the vessel. In the design, only the calm-water drag is optimized. The simulated codesigned vessel had 10% lower calm water and mean seaway drag than the sequentially designed vessel. However, the codesigned vessel's seakeeping was poorer—vertical acceleration doses 25% higher. Results indicate that the traditional sequential design approach does not fully exploit the synergy between a planing craft and its ACS; as a first step, the stability constraints should be relaxed in the design exploration, and the ACS should be considered early in the design stage.
Dynamic Analysis of 4-SPS/CU Parallel Mechanism Considering Three-Dimensional Wear of Spherical Joint With Clearance
Authors: Wang Gengxiang , Liu Hongzhao , Deng Peisheng , Yin Kaiming , Zhang Guanggang
Published: September 2016

The dynamic performance of 4-SPS/CU (spherical joint, prismatic joint, cylindrical joint, and universal joint) parallel mechanism considering spherical joint with clearance is developed, and the three-dimensional (3D) wear property of the socket is based on the Archard's wear model. First, the kinematics model of spherical joint with clearance is established, and the updated procedure pertaining to the contact mechanics and wear state is explained via a flowchart. An improved contact force model was proposed by Flores et al. contact force model through a revised contact stiffness coefficient. The normal and tangential contact forces between ball and socket are calculated using the improved contact force model and a modified Coulomb friction model. Second, the dynamic model of the parallel mechanism considering spherical joint with clearance is formulated based on the multibody equations of motion. In order to obtain the 3D wear property of spherical joint with clearance, the contact force is decomposed into three components in the global coordinate system. The three components of sliding distance are computed based on the 3D revolute property of the parallel mechanism. Finally, the contact pressures in three different directions are calculated by the corresponding contact force and approximate contact area components for the sake of predicting the 3D wear depth of socket based on the Archard's wear model. The simulation results show that the wear depth in different directions along the socket surface is nonuniform, which affects the performance of 4-SPS/CU parallel mechanism.
Model for a Sphere–Flat Elastic–Plastic Adhesion Contact
Authors: Wang Zhi Qian , Wang Jin Feng
Published: September 2016

This paper presents a cubic model for the sphere–flat elastic–plastic contact without adhesion. In the cubic model, the applied load and the contact area are described by the cubic polynomial functions of the displacement to the power of 1/2 during loading and unloading, and the applied load is also expressed as the cubic polynomial function of the contact area to the power of 1/3 during loading. Utilizing these cubic polynomial functions, the elastic–plastic load (EPL) index, which is defined by the ratio between the dissipated energy due to plastic deformations and the work done to deform the sphere during loading, is calculated analytically. The calculated EPL index is just the ratio between the residue displacement after unloading and the maximum elastic–plastic displacement after loading. Using the cubic model, this paper extends the Johnson–Kendall–Roberts (JKR) model from the elastic regime to the elastic–plastic regime. Introducing the Derjaguin–Muller–Toporov (DMT) adhesion, the unified elastic–plastic adhesion model is obtained and compared with the simplified analytical model (SAM) and Kogut–Etsion (KE) model.
Prediction of Rail and Bridge Noise in Near- and Far-Field: A Combined 2.5-Dimensional and Two-Dimensional Method
Authors: Song X. D. , Li Q. , Wu D. J.
Published: September 2016

Bridge noise and rail noise induced by passing trains should be included while estimating low- and medium-frequency (20–1000 Hz) noise in railway viaducts. However, the prediction of bridge noise and rail noise using a three-dimensional (3D) acoustic model is not efficient, especially for far-field points. In this study, a combined 2.5-dimensional (2.5D) and two-dimensional (2D) method is proposed to predict bridge noise and rail noise in both the near- and far-field. First, the near-field noise is obtained by combining the 2.5D acoustic model and a 3D vehicle–track–bridge interaction analysis. Then, the 2D method is used to estimate the attenuation of bridge noise and rail noise in the far-field, and the accuracy is validated through comparison with the 2.5D method. Third, the near-field points are treated as reference sources, and the noise at far-field points is predicted by combining the 2.5D and 2D methods. Finally, the proposed method is used to predict the bridge noise and rail noise for a box girder and a U-shaped girder. The spatial distribution of the bridge noise and rail noise is investigated. Generally, the rail noise is dominant above the bridge, and the bridge noise has a larger contribution to the total noise beneath the bridge. The rail noise from the U-shaped girder is much smaller than that from the box girder due to the shielding effect of the webs.
Dynamics and Control of a Differential Drive Robot With Wheel Slip: Application to Coordination of Multiple Robots
Authors: Konduri Shyamprasad , Torres Edison Orlando Cobos , Pagilla Prabhakar R.
Published: September 2016

In differential drive robots, wheel slip severely affects the ability to track a desired motion trajectory and the problem is exacerbated when differential drive robots are used in applications involving coordination of multiple robots. This problem is investigated and, based on the wheel–ground traction forces, a simple slip avoidance control strategy is discussed. Differential drive robots with two driven wheels and one or more ball-type caster wheels are considered. The traction forces between the wheels and the ground surface are determined by assuming rigid wheel, rigid ground interaction. These traction forces are used to determine the maximum value of the input wheel torque that can be applied on the wheel before it slips. To avoid wheel slip, this limiting torque value is used to set a saturation limit for the input torque computed by a trajectory tracking controller. Stability of the closed-loop system with the slip avoidance strategy is shown. Experiments are conducted with this strategy using a single robot as well as multiple robots in a platoon. A representative sample of the experimental results is presented and discussed.
Spectral Analysis of Electrohydraulic System
Authors: Yoon Yongsoon , Sun Zongxuan
Published: September 2016

This paper presents spectral analysis of an electrohydraulic system. For a linear system, spectral analysis using a frequency response function (FRF) offers great insight into system dynamics and controls. The objective of this paper is to extend such benefits to the nonlinear electrohydraulic system. To achieve the objective, generalized frequency response functions (GFRFs) and output spectra of the electrohydraulic system are analyzed in frequency domain. In this paper, two different approaches are proposed to derive the GFRFs. In the first approach, the analytic GFRFs are derived from physical dynamics of the electrohydraulic system. Thus, the dynamic features of the electrohydraulic system can be explored with respect to the physical parameters explicitly in frequency domain. In the second approach, the experimental GFRFs are identified from frequency response data. Although the explicit relationship with the physical parameters is not available, they can predict the output spectrum without a priori knowledge of the electrohydraulic system. The proposed approaches are applied to derive the GFRFs analytically and experimentally for spectral analysis of an electrohydraulic system. Spectral analysis reveals the critical dynamic features of the electrohydraulic system in frequency domain, and it turns out to be crucial for system design, identification, and controls of the electrohydraulic system.
Model-Based Robust Optimal Control for Layer-By-Layer Ultraviolet Processing of Composite Laminates
Authors: Yebi Admu , Ayalew Beshah , Pilla Srikanth , Yu Xiaoyan
Published: September 2016

This paper first discusses some experimental verification of proposed ultraviolet (UV) radiation curing process models and then it outlines a robust process optimization and control scheme for layer-by-layer UV processing of a thick composite laminate. The experiments include UV transmission, cure kinetics, and in situ temperature measurements for UV curing of a one-dimensional (1D) composite material sample. The validated models are used to motivate how optimizing the layer-by-layer curing process can help address the challenge of maintaining through-cure due to the in-domain attenuation of the UV input during thick-part fabrication. The key insight offered is to model the layer-by-layer deposition and curing process as a multimode hybrid dynamic system with a growing spatial domain, where the interlayer hold times and the UV intensity at each layer addition can be taken as the augmented control variables to be selected optimally. Specifically, the control input is set to have feed forward and output feedback components, which act on the UV intensity at each layer and are constructed to track a reference surface temperature trajectory. The feedback gains at each layer addition are designed by posing a robust optimization problem that penalizes the sensitivity of the objective function to process uncertainties. It is illustrated using simulation analyses that augmented control with robust optimal static feedback of UV intensity at each layer and nominal optimization of the interlayer hold times gives very close tracking of a desired final cure level distribution in the presence of parametric uncertainty.
Resonant Response of Mistuned Bladed Disk Expressed by Vibratory Stress
Authors: Kaneko Yasutomo , Mori Kazushi , Ooyama Hiroharu
Published: September 2016

Although bladed disks of turbomachinery are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all blades on a disk are slightly different due to the manufacturing tolerance, the deviation of the material property, the wear during operation, and so on. These small variations break the cyclic symmetry, and split the eigenvalue pairs. The actual bladed disks with the small variations are referred to a mistuned system. In the forced response of a mistuned bladed disk, the responses of all blades become different, and the response of a certain blade may become extremely large due to the split of the duplicated eigenvalues, the distortion of the vibration modes, and so on. On the other hand, many researchers suggest that the mistuning suppresses the blade flutter, because the complete travelling wave mode is not formed in a disk. In other words, the main conclusions of researches on mistuning are that while mistuning has an undesirable effect on the forced response, it has a beneficial (stabilizing) effect on the blade flutter (the self-excited vibration). Although such mistuning phenomena of bladed disks have been studied since 1980s, almost all studies focused on the amplification factor of the displacement response, and few studies researched the amplification factor of the vibratory stress response. In this study, first, the frequency response analysis of the mistuned simple bladed disk consisting of flat plates is carried out. Comparing the amplification factor of the displacement response with that of the vibratory stress response, the amplification factor expressed by the vibratory stress is studied in detail. Second, the mistuning analysis of the actual bladed disk used in a steam turbine is carried out. From these results, the mistuning effect expressed by the vibratory stress is clarified.
Gas Turbine Operation Offshore: Increased Operating Interval and Higher Engine Performance Through Optimized Intake Air Filter System
Authors: Madsen Stian , Bakken Lars E.
Published: September 2016

Optimized operation of gas turbines is discussed for six LM2500PE engines at a Statoil North Sea offshore field. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load (T5.4 control), hence the production rate is limited by the available power from these engines. All of the six engines discussed run continuously without redundancy, gas turbine uptime is therefore critical for the field’s production and economy. The performance and operational experience with upgraded inlet air filter systems and online water wash at high water-to-air ratio, as well as successful operation at longer intervals and higher average engine performance are described.

For North Sea operation, a key property of the filter system is the ability to handle high humidity and high salt-content through the harsh environment in these waters. The upgraded filter systems analyzed in this paper is a 2-stage system (vane separator stage upstream of the high-efficiency-filter stage), which is a simplified design versus the old traditional 3-stage systems (louvre upstream and vane separator downstream of the filter stage). These 2-stage systems rely on an efficient upstream vane separator to remove the vast majority of water from the airflow before it reaches the high-efficiency filters. The high-efficiency filters are especially designed to withstand moisture. Deposit analysis from the downstream side of the filters has been performed. Extensive testing of both new and used filter elements, of different filter grade and operated at different intervals, has been performed on a filter test rig facility onshore.

All six engines have historically been operated with 4-month intervals between maintenance stops. Online wash is performed daily between the maintenance stops at full load (i.e. normal operating load for the subject engine). As a result of successful development and pilot testing of new filters and optimized filter change intervals, as well as successful online water wash, the engine operating intervals are now extended to 6 months with very low deterioration rate.

Understanding the gas turbine performance deterioration is of vital importance. Trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine’s condition. Instrument resolution and repeatability are key factors in order to get reasonable results from the performance analysis. Improvement of the package instrumentation has been implemented on three of the analyzed engines, for better performance monitoring. As a result of these analyses, a set of monitoring parameters is suggested for effective diagnostics of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.
LES of a Round Impinging Jet: Investigation of the Link Between Nusselt Secondary Peak and Near-Wall Vortical Structures
Authors: Aillaud Pierre , Duchaine Florent , Gicquel Laurent
Published: September 2016

In an attempt to improve our understanding of the fundamental flow problem that is an impinging jet, a wall-resolved Large Eddy Simulation (LES) is produced to investigate large-scale unsteady flow features, mixing processes near the wall and heat transfer. The simulation focuses on a single unconfined round jet normally impinging on a flat plate at a Reynolds number (based on the pipe diameter and bulk velocity) of Re = 23 000 and for a nozzle to plate distance of H = 2D. This configuration is known to lead to a double peak in the Nusselt distribution. Evaluation of the high order statistics, such as Skewness and Kurtosis of the temporal evolution of axial velocity and wall heat flux, provides first-ever insights into the effect of the vortical structures on the mean wall heat transfer. Heat transfer statistics such as probability density functions (PDF) confirm the ability of LES to reproduce the strong intermittent thermal events responsible for the increase of the mean wall heat transfer radial distribution. Axial velocity and temperature temporal distributions are analysed simultaneously to gain further insight into the mixing process near the wall. In particular, the probabilities of the different cold/hot fluid ejection/injection events prove that the strong intermittent thermal events are linked to a change in the mixing behavior induced by the passage of the large-scale vortical structures. These structures are found to preferentially produce a cold fluid flux towards the wall leading to the local heat transfer enhancement usually identified by the secondary peak.
Experimental/Numerical Investigation of Crossover Jet Impingement in a Rib-Roughened Trailing-Edge Cooling Channel
Authors: Taslim Mohammad E. , Xue Fei
Published: September 2016

Local and average heat transfer coefficients were measured in a test section simulating a rib-roughened trailing edge cooling cavity of a turbine airfoil. The rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven cross-over jets, issued from these slots entered the trailing-edge channel, impinged on eleven ribs, made a 90-degree turn and exited from the end of the trailing-edge channel. Tests were run for the baseline case of smooth target wall as well as four angles of attack between the axial flow and the ribs (0°, 45°, 90° and 135°). Cross-over jet axis made a zero-degree angle with the trailing-edge channel center-plane. Jet Reynolds number was varied from 10,000 to 35,000. The numerical models contained the entire trailing-edge and supply channels with all slots and ribs to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. The k–ω with Shear Stress Transport (SST) turbulence model was used for turbulence closure. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each cross-over hole from the total flow for different rib geometries. The major conclusions of this study were:a) Both measured and numerically-obtained results show that the local Nusselt numbers correlate well with the local jet Reynolds numbers, b) 90° rib arrangement, that is when the cross-over jet axis was parallel to the rib longitudinal axis, produced a higher heat transfer coefficient, and c) Numerical heat transfer results were generally in good agreement with the test results. The overall difference between the CFD and test results was about 10%.
Perspectives and Experience With Wet Gas Compression
Authors: Musgrove Grant O. , Poerner Melissa A. , Beck Griffin , Kurz Rainer , Bourn Gary
Published: September 2016

In oil and gas applications, gas-liquid mixtures of a process fluid are commonplace and the phases of the mixtures are separated upstream of pump or compressor machinery. Considering compressors, the separation of phases is important because the liquid causes the compressor to operate significantly different than with dry to affect the range, performance, and durability of the machine. Even with separation equipment, liquid can be ingested in a compressor by liquid carryover from the separator or condensation of the process gas. Additionally, there is no single definition of what is considered a wet gas.

In this paper, the definition of wet gas from multiple applications is reviewed and a general definition for wet gas is formulated. The effects of wet gas on reciprocating, screw-type, and centrifugal compressors are reviewed to provide insight into how their operation is affected. The limited information for screw compressors is supplemented with multiphase effects in screw pumps.
An Investigation of Turbine Film Cooling Effectiveness With Shaped Holes and Internal Cross-Flow With Varying Operational Parameters
Authors: Wilkes Ellen , Anderson Joshua , McClintic John , Bogard David
Published: September 2016

This study focuses on specifics of gas turbine film cooling. Laboratory film cooling tests are important for industry because actual engine conditions are too hot, too small, and too fast to take accurate and high resolution measurements. Experiments are typically conducted using a plenum to feed coolant through round or shaped film cooling holes. Less common are experiments using cross-flow fed coolant, a method that flows coolant perpendicular to the mainstream flow and better represents engine designs. There are a few studies that have explored shaped holes in cross-flow, but none have looked at the effect cross-flow channel parameters other than Mach number.

Here, the effectiveness of film cooling is quantified by measuring adiabatic effectiveness on a flat plate with a single row of shaped film cooling holes in cross-flow. A preliminary examination of the effect of cross-flow versus plenum fed coolant on the adiabatic effectiveness of the axial 7-7-7 shaped hole, a laidback fan-shaped hole with a 30 degree injection angle, is first conducted. Subsequently, the effects of two internal coolant parameters on film cooling effectiveness are presented: Reynold’s number inside the cross-flow channel, and velocity ratio (defined as the ratio of cross-flow channel average velocity to mainstream velocity). By measuring the effect of these parameters, a chain of relative importance can be generated and applied to future experimentation. Parameters that heavily influence film cooling effectiveness can be studied further and optimized for turbine film cooling design.
Unmanned Air Vehicle Interdisciplinary Design Project
Authors: Templalexis Ioannis , Lekas Theodore , Koutsomichalis Agelos , Kalfas Anestis
Published: September 2016

Mechanical Engineers graduating from the Hellenic Air Force Academy (HAFA), are initially appointed in a military squadron, to support and manage the aircraft maintenance workload. Throughout their career, they will at some point, be appointed in a procurement or in a research department, where they will need to have an integral understanding of how a certain aircraft in conjunction with its propulsion system, can meet prescribed operational needs. The syllabus of the Mechanical Engineering degree offered at the HAFA, encompasses several modules related to Aircraft Design, Material Science and Propulsion Systems. The Aircraft Design Project (ADP) presented herein, aims to stimulate the cadets in applying a diverse field of knowledge on a single application, building thus soon enough the missing communication link between those who deal with the power plant and those who deal with the aircraft design. The assignment input is only confined in a short description of the operational profile of an Unmanned Air Vehicle (UAV) to be designed. A number of teams are formed which act competitively and develop a design proposal, each one for its own sake. As part of the project, they also have to print a 3D mock-up and do a testing in the wind tunnel operated within the HAFA. Finally, each team has the obligation to defend its design in front of an audience consisting of HAF military officers, HAFA academics and delegates from industries. The proposed exercise constitutes a novel conception of coursework type, extending over one year, engaging three Academic Sectors and aiming to achieve the following educational targets: a) Learn to work in a team within a competitive environment. Each cadet has to collaborate with his teammates and compete with the members of the other team(s). b) Combine and apply knowledge acquired from various scientific fields. c) Learn how to “sell” a product to a diverse audience being interested in engineering excellence (academia) cost effectiveness (industry) and degree of compliance with operational needs (military).
Heat Transfer Coefficients and Film Cooling Effectiveness of Transonic Turbine Vane Suction Surface Using TSP Technique
Authors: Shiau Chao-Cheng , Chowdhury Nafiz H. K. , Yang Shang-Feng , Han Je-Chin , MirzaMoghadam Alexander , Riahi Ardeshir
Published: September 2016

This paper experimentally studies the effect of transonic flow on local heat transfer coefficients and film cooling effectiveness distributions of a turbine vane’s suction surface with compound-angle shaped-hole configuration. A Temperature Sensitive Paint (TSP) method is used to determine the local heat transfer coefficients and film cooling effectiveness simultaneously. Tests were performed in a five-vane annular-sector cascade blow-down facility. The exit Mach numbers are controlled to be 0.7 and 0.9, from subsonic to transonic conditions. Compressed air is used as coolant with a coolant-to-mainstream density ratio 0.91 on film cooling and heat transfer study. Three averaged coolant-to-mainstream blowing ratios in the range, 0.7, 1.0, and 1.6 are investigated. The test vane features three rows of radial-angle cylindrical holes around the leading edge, and two rows of compound-angle shaped holes on the suction side. Effects of blowing ratio and exit Mach number on the vane suction surface heat transfer and film cooling effectiveness distributions are obtained, and the results are presented and explained in this investigation.
Theoretical Analysis and Numerical Simulation of Oil Lubricated Foil Bearing With Elastic Supported Bump Foil Structure
Authors: Zhang Guanghui , Chen Qiang , Yan Jiajia , Wang Xianghe , Liu Zhansheng , Xu Fangcheng
Published: September 2016

The oil lubricated multi-leaf foil bearing is developed to meet the demand of high rotating speed for hydraulic turbo-pump, where the lubricated oil is easy to obtain. For the stability of this kind oil lubricated foil bearing needs to be guaranteed, the bearing with elastic supported bump foil structure is proposed to improve the performance of foil bearing. Theoretical analysis and numerical simulation is carried out in this paper. The film thickness expression of multi-leaf foil bearing is established for the cases with and without top foil deformation. The total flexibility matrix considering elastic supported bump foil structure is developed based on Castigliano’s theorem. By employing the Reynolds boundary condition, the oil cavitation effect is presented. The established flexibility matrix is substituting into classical incompressible Reynolds equation, then the deformation equation of the foil and Reynolds equations are solved coupling by successive over relaxation method. The static characteristics such as pressure distribution, bearing load and static equilibrium position are obtained. By employing the perturbation method to Reynolds equations and foil deformation equation, the dynamic characteristics of multi-leaf foil bearing with elastic supported bump foil structure are acquired. The stability of the bearing is analyzed and compared with other type bearings by Routh-Hurwitz method. The effects of bearing load and sommerfeld parameter on the stiffness and damping coefficients are studied. The results indicate that the performance of foil bearing with elastic supported bump foil structure is improved and this kind bearing is suitable for high rotating speed application.
A Water Lubricated Hybrid Thrust Bearing: Measurements and Predictions of Static Load Performance
Authors: San Andrés Luis , Phillips Stephen , Childs Dara
Published: September 2016

Process fluid lubricated thrust bearings (TBs) in a turbomachine control rotor placement due to axial loads arising from pressure fields on the front shroud and back surface of impellers. To date, prediction of aerodynamic induced thrust loads is still largely empirical. Thus needs persist to design and operate proven thrust bearings and to validate predictions of performance derived from often too restrictive computational tools. This paper describes a test rig for measurement of the load performance of water lubricated hydrostatic/hydrodynamic thrust bearings operating under conditions typical of cryogenic turbo pumps.

The test rig comprises of a rigid rotor composed of a thick shaft and two end collars. A pair of flexure-pivot hydrostatic journal bearings (38 mm in diameter) support the rotor and quill shaft connected to a drive motor. The test rig hosts two thrust bearings (8 pockets with inner diameter equal to 41 mm and outer diameter equal to 76 mm); one is a test bearing and the other is a slave bearing, both facing the outer side of the thrust collars on the rotor. The slave TB is affixed rigidly to a bearing support. A load system delivers an axial load to the test TB through a non-rotating shaft floating on two aerostatic radial bearings. The test TB displaces to impose a load on the rotor thrust collar and the slave TB reacts to the applied axial load.

The paper presents measurements of the TB operating axial clearance, flow rate and pocket pressure for conditions of increasing static load (max. 3,600 N) and shaft speed to 17.5 krpm (tip speed 69.8 m/s) and for an increasing water supply pressure into the thrust bearings, max. 17.2 bar (250 psig). Predictions from a bulk flow model that accounts for both fluid inertia and turbulence flow effects agree well with recorded bearing flow rates (supply and exiting thru the inner diameter), pocket pressure and ensuing film clearance due to the imposed external load. The measurements and predictions show a film clearance decreasing exponentially as the applied load increases. The bearing flow rate also decreases, and at the highest rotor speed and lowest supply pressure, the bearing is starved of lubricant on its inner diameter side, as predicted. The measured bearing flow rate and pocket pressure aid to the empirical estimation of the orifice discharge coefficient for use in the predictive tool. The test data and validation of a predictive tool give confidence to the integration of fluid film thrust bearings in cryogenic turbo pumps as well as in other more conventional (commercial) machinery. The USAF Upper Stage Engine Technology (USET) program funded the work during the first decade of the 21st century.
Influences of Target Surface Roughness on Impingement Jet Array Heat Transfer: Part 2 — Effects of Roughness Shape, and Reynolds Number
Authors: Buzzard W. , Ren Z. , Ligrani P. M. , Nakamata C. , Ueguchi S.
Published: September 2016

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. The surface roughness shapes considered here are rectangle and triangle, in combination with larger rectangular pins. Configurations considered include: (i) arrays of small rectangular roughness, (ii) arrays of small triangle roughness, (iii) combinations of small rectangle roughness and large pins together, and (iv) combinations of small triangle roughness and large pins together. Tests are performed at impingement jet Reynolds numbers of 900, 1500, 5000, and 11000. Local and overall impingement cooling performance depends upon the shape of the roughness elements, as well as upon the jet Reynolds number. Depending upon the magnitude of jet Reynolds number, different behavior and trends are observed for the arrays of small rectangle roughness, compared with arrays of small triangle roughness. These differences are related to the abilities of the two different roughness shapes to generate different distributions of local mixing and vorticity at different length and time scales. Overall, results demonstrate the remarkable ability of target surface roughness to produce increased surface heat transfer augmentation levels of impingement jet array cooling, relative to target surfaces which are smooth.
Numerical Study on Aeroelastic Instability for a Low Speed Fan
Authors: Lee Kuen-Bae , Wilson Mark , Vahdati Mehdi
Published: September 2016

Over recent years engine designs have moved increasingly toward low specific thrust cycles to deliver significant specific fuel consumption (SFC) improvements. Such fan blades are more loaded than conventional fan blades and therefore can be more prone to aerodynamic and aeroelastic instabilities. The aim of this paper is to analyse the flutter stability of a low speed/low pressure ratio fan blade. By using a validated CFD model (AU3D), three dimensional unsteady simulations are performed for a modern low speed fan rig for which extensive measured data are available. The computational domain contains a complete fan assembly with an intake duct and the downstream OGVs (whole LP domain). Flutter simulations are conducted over a range of speeds to understand flutter characteristics of this blade. Only the 1F (first flap) mode is considered in this work. Measured rig data obtained by using the same fan set but with two different intakes showed a significant difference in the flutter boundary for the two intakes. AU3D computations were performed for both intakes and were used to explain this difference between the two intakes, and showed that intake reflections play an important role in flutter of this blade. In the next phase of this work, two possible modifications for increasing the flutter margin of the fan blade were explored:

1. Changing the mode shape of the blade

2. Using acoustic liners in the casing

The results show that it is possible to increase the flutter margin of the blade by either decreasing the ratio of the twisting to plunging motion in 1F mode or by introducing deep acoustic liners in the intake. The liners have to be deep enough to attenuate the flutter pressure waves and hence influence the stability.

The results indicate the importance of reflection in flutter stability of the fan blade, and clearly show that intake duct needs to be included in flutter study of any fan blade.