bluuebunny/crossref_metadata_2025 huggingface dataset:
“Double carbapenem” and oral fosfomycin for the treatment of complicated urinary tract infections caused by blaNDM‐harboring Enterobacteriaceae in kidney transplantation
Authors: Rosa Rossana , Rudin Susan D. , Rojas Laura J. , Hujer Andrea M. , Perez‐Cardona Armando , Perez Federico , Bonomo Robert A. , Martinez Octavio , Abbo Lilian M. , Camargo Jose F.
Published: October 2017

Infections with carbapenemase‐producing carbapenem‐resistant Enterobacteriaceae represent an emergent problem worldwide. Treatment of infections caused by New Delhi metallo‐beta‐lactamase (NDM)‐harboring Enterobacteriaceae is particularly challenging as it frequently involves the use of nephrotoxic agents, which is problematic in kidney transplant recipients and non‐renal transplant patients with marginal kidney function. We present two cases of urinary tract infections caused by NDM‐harboring Enterobacteriaceae successfully treated with a combination of “double carbapenem” and oral fosfomycin.
Management of adnexal masses in pregnancy
Authors: Alalade Aderemi O , Maraj Hemant
Published: October 2017

Key content

Adnexal masses are commonly identified in pregnancy but they are rarely malignant.

Most adnexal masses either resolve spontaneously or can be managed conservatively during pregnancy.

Pregnancy may alter the serum levels of tumour markers, making the interpretation of results difficult.

Surgery in pregnancy is indicated in cases of an acute abdomen and high suspicion of malignancy.

In cases where there is a high suspicion of malignancy, a multidisciplinary approach is required taking into account the woman's age, gestation, parity, desire for fertility and the likely stage of disease.

Learning objectives

To be aware of the clinical presentation and ultrasound characteristics of clinically significant adnexal masses in pregnancy.

To understand the limitations of investigations in pregnancy and the importance of a multidisciplinary approach in the management of complex adnexal masses.

To be aware of the indications for surgery and evaluate the appropriateness, mode and timing of surgery in pregnancy.
Influence of catecholamines at different dosages on the function of the LiDCO sensor in isoflurane anesthetized horses
Authors: Hopster Klaus , Ambrisko Tamas D. , Kästner Sabine B. R.
Published: October 2017

Objective

To compare the lithium dilution method for cardiac output (LiDCO) and bolus‐thermo‐dilution (BTD) measurements before and during infusion of dobutamine, dopamine, phenylephrine, or noradrenaline at 2 different doses in anesthetized horses and to examine the correlation between sensor voltages (saline–blood exposed) and possible measurement errors.

Design

Prospective experimental study.

Setting

University teaching hospital.

Animals

Nine Warmblood horses.

Interventions

Following 90 minutes of equilibration, 3 different doses of dobutamine (0.5–3 μg/kg/min), dopamine (1–5 μg/kg/min), phenylephrine (0.5–3 μg/kg/min), or noradrenaline (0.1–0.5 μg/kg/min) were administered for 15 minutes in anesthetized horses, and measurements using the LiDCO were performed at the lowest and highest doses. Pairs of LiDCO and BTD measurements were collected and sensor voltages exposed to blood and saline were measured before and at the end of each infusion period. Agreement between LiDCO and BTD was assessed with the Bland–Altman method.

Measurement and Main Results

The biases (2 standard deviations) before infusion of dobutamine, dopamine, phenylephrine, and noradrenaline were 1.1 (5.7), 1.6 (7.3), 0.2 (6.6), and 1.5 (4.1) L/min, respectively, and minimally and nonsignificantly changed following low‐dose catecholamine infusions. Following infusion of higher doses, biases were significantly higher compared to baseline with 10.7 (7.8), 11.2 (11.9), 6.9 (11.7), and 3.5 (3.8) L/min, respectively. The difference between saline‐ and blood‐exposed sensor voltage decreased during infusion of high doses of catecholamines with correlations (rs = 0.62) between cardiac output differences and sensor voltage differences (saline‐blood).

Conclusions

This study demonstrated that catecholamines could lead to overestimation in a dose‐dependent fashion in LiDCO measurements. Monitoring changes in sensor voltage differences (saline‐blood) is a valuable and clinically applicable tool to predict errors in LiDCO measurements.
Carbon source utilization‐based metabolic activity of Salmonella Oranienburg and Salmonella Saintpaul in river water
Authors: Medrano‐Félix José Andrés , Castro‐del Campo Nohelia , Peraza Garay Felipe de Jesús , Martínez‐Rodríguez Célida Isabel , Chaidez Cristóbal
Published: October 2017

The presence of introduced or non‐native bacteria in river water can create a selective pressure due to their ability to overcome fluctuations in physicochemical conditions and carbon source availability. The carbon source concentrations (monosaccharides and polysaccharides), physicochemical parameters (turbidity, total dissolved solids, biochemical oxygen demand, temperature and pH) and metabolic activity of Salmonella Oranienburg and Saintpaul were determined in water from the central Sinaloa state rivers. This study's results revealed that the carbohydrate availability and physicochemical conditions of river water make it a suitable niche for the establishment of Salmonella serotypes. Metabolic profiles showed that Salmonella Typhimurium could consume a wide variety of carbon sources but only at moderate levels; in contrast, Salmonella Oranienburg and Salmonella Saintpaul demonstrated intense carbon source utilization of a limited diversity of carbon sources. Carbohydrates, amino acids and carboxylic acids were the metabolites most utilized by the environmental Salmonella strains, demonstrating their superior ability to adapt to and survive in river water.
Convergence Properties of the Kalman Inverse Filter
Authors: Petschel B. S. , Soltani Naveh K. , McAree P. R.
Published: October 2017

The Kalman filter has a long history of use in input deconvolution where it is desired to estimate structured inputs or disturbances to a plant from noisy output measurements. However, little attention has been given to the convergence properties of the deconvolved signal, in particular the conditions needed to estimate inputs and disturbances with zero bias. The paper draws on ideas from linear systems theory to understand the convergence properties of the Kalman filter when used for input deconvolution. The main result of the paper is to show that, in general, unbiased estimation of inputs using a Kalman filter requires both an exact model of the plant and an internal model of the input signal. We show that for unbiased estimation, an identified subblock of the Kalman filter that we term the plant model input generator (PMIG) must span all possible inputs to the plant and that the robustness of the estimator with respect to errors in model parameters depends on the eigenstructure of this subblock. We give estimates of the bias on the estimated inputs/disturbances when the model is in error. The results of this paper provide insightful guidance in the design of Kalman filters for input deconvolution.
Effect of Solid Carburization on the Tribological Behaviors of Ti13Nb13Zr Alloy
Authors: Luo Yong , Rao Xu , Yang Ting , Zhu Junhao
Published: October 2017

Due to its high mechanical strength, exceptional biocompatibility, low elastic modulus, and superior corrosion resistance, Ti13Nb13Zr alloy is one of the potential candidates for implanted joints. However, the poor tribological property of Ti13Nb13Zr alloy has greatly limited its wide usage in artificial joints. The elevated temperature solid carburizing technology was used to improve tribological property of Ti13Nb13Zr alloy. It was found that the surface hardness of Ti13Nb13Zr alloy was increased to 812 HV after the carburization at 1523 K due to the formation of titanium carbide on the surface. With the increase in experimental temperature, the thickness of the carburized layer increased to 120 μm. In addition, the wear rate of Ti13Nb13Zr alloy decreased by 63.9% under serum lubrication condition after the carburization at 1473 K due to the formation of hard TiC on the surface of Ti13Nb13Zr.
Entropy Generation for Oscillatory Flow Inside Thermal-Lag Type Stirling Engine: Numerical Analysis
Authors: Hachem Houda , Gheith Ramla , Ben Nasrallah Sassi , Aloui Fethi
Published: October 2017

The present paper investigates the heat characteristics of oscillatory piston-driven flow inside thermal-lag type Stirling engine. The geometry consists of a cylinder partially filled with a porous metal structure called regenerator, heated at the lateral wall on one side and cooled on the other side. Brinkman-Forchheimer-Lapwood extended Darcy model is assumed to simulate heat transfer within the regenerator.

A numerical model is used to evaluate average entropy generation rate in the regenerator depending on its characteristics (form factor Lr /Dr, porosity and material) and on the oscillatory flow characteristics (working fluid, rotational engine speed, hot end temperature and initial pressure). The output power of the thermal lag Stirling engine is estimated for different working conditions. Results show that, the two main contributors to entropy generation in the regenerator are: entropy due to heat transfer (imperfection loss, internal conduction loss) and entropy due to viscous friction. Regenerator design leading to minimum entropy generation was investigated.
Numerical Analysis of Internal and External Flow Fields of a Fluidic Actuator for Active Flow Control Applications
Authors: Aram Shawn , Lee Yu-Tai , Shan Hua , Vargas Abel
Published: October 2017

A numerical study is conducted to explore the unsteady nature of fluidic oscillators which is responsible for generating sweeping jets for effective flow control of large-scale applications. Two- and Three-dimensional (2D and 3D) Unsteady Reynolds-Averaged Navier-Stokes (URANS) and 3D Improved Delayed Detached Eddy Simulation (IDDES) are employed to simulate and resolve the flow structures in the internal flow passages of a fluidic oscillator and external flow field in a quiescent flow condition. The predicted flow generated by an enlarged actuator with an outlet diameter of 25 mm using air as a working fluid is validated against measurements at various supply rates. Comparison of current computational results using 2D and 3D URANS with experiments indicates a reasonable agreement in the jet oscillation frequency. However, a significant discrepancy in the streamwise velocity field is observed between the 2D URANS and experimental data. The 3D URANS also under-predicts the jet width and consequently over-predicts the extension of the jet in the axial direction downstream of the actuator exit. Excellent agreement in the jet oscillation frequency and internal and external flow field is obtained at two supply rates between 3D IDDES and measurements.
A Numerical Investigation to Study Roughness Effects in Oscillatory Flows
Authors: Ghodke Chaitanya D. , Apte Sourabh V.
Published: October 2017

Effects of roughness on the near-bed turbulence characteristics in oscillatory flows are studied by means of particle-resolved direct numerical simulations (DNS). Two particle sizes of diameter 375 and 125 in wall units corresponding to the large size gravel and the small size sand particle, respectively, in a very rough turbulent flow regime are reported. A double-averaging technique is employed to study the nature of the wake field, i.e., the spatial inhomogeneities at the roughness length scale. This introduced additional production and transport terms in double-averaged Reynolds stress budget, indicating alternate pathways of turbulent energy transfer mechanisms. Budgets of normal components of Reynolds stress reveal redistribution of energy from streamwise component to other two components and is attributed to the work of pressure in both flow cases. It is shown that the large diameter gravel particles significantly modulate the near-bed flow structures, leading to pronounced isotropization of the near-bed flow; while in the sand case, elongated horseshoe structures are found as a result of high shear rate. Effect of mean shear rate on the near-bed anisotropy is significant in the sand case, while it is minimal for the gravel-bed. Redistribution of energy in the gravel case showed reduced dependence on the flow oscillations, while for the sand particle it is more pronounced towards the end of an acceleration cycle.
Simulations of Particle Detachment From a Flat Surface
Authors: Palakurthi Nithin Kumar , Ghia Urmila , Turkevich Leonid
Published: October 2017

Understanding particle detachment from surfaces is necessary to better characterize dust generation and entrainment in large-scale industries (such as metallurgical and foundry facilities, clean room settings, semiconductor device fabrication) and in health care (powder inhalers in pharmaceuticals, or the unwanted respiratory exposure to small particles, e.g., asbestos). The present work investigates the aerodynamics of a particle attached to a surface subjected to given fluid flow. The particle is represented as a sphere in a parallel plate channel, and this constitutes a three-dimensional (3D) flow problem. Since many of the challenges and results of the full 3D problem are also manifest in a corresponding two-dimensional (2D) configuration, as a first step, 2D simulations are conducted in a parallel plate channel, with the particle approximated as a cylinder. In both 2D and 3D cases, to model the particle just touching the surface leads to a singularity in grid generation; we have addressed this issue with two concurrent approaches. In the first approach, the particle is located at various finite distances from the surface; results are then extrapolated to zero height (particle just touching the surface). In the second approach, the bottom of the particle is embedded into the surface at different depths; again, results are extrapolated to zero embedding depth. In all cases, the flow is assumed to be steady, incompressible and laminar: (1 < Rechannel < 2000), and is represented by the Navier-Stokes equations. A fully-developed velocity profile is specified at the channel inlet. The computational domain is discretized using structured and hybrid grids, considering the boundary-layer physics. The governing equations are solved using the finite-volume FLUENT code. From the obtained numerical results, the coefficients of lift, drag and moments are computed, and compared with the results available in the published literature. For the particle touching the surface, aerodynamic forces (drag and lift) and moments are obtained by extrapolation for both approaches (particle located at finite height off the wall, and the partially embedded particle). The results of the 2D and 3D simulations show that, for a particle touching the surface, a threshold velocity (with corresponding threshold Re) exists for particle detachment (i.e., positive lift), and the moment plot indicates that the particle will tend to roll as it detaches.
Study on Appropriate Diameter of Centrifugal Fan Surrounded by Heat Exchanger in Air Conditioner
Authors: Sato Daiwa , Iwase T. , Xue J. , Tsuchihashi K. , Obara H. , Fushimi N.
Published: October 2017

To meet the demand for energy-saving air conditioners, the pressure drop must be reduced and the air velocity distribution of the heat exchanger made uniform to improve the performance of both the fan and the heat exchange cycle. To investigate the effect of the fan on the pressure drop and the velocity distribution, we changed the fan diameter and fixed the shape of the heat exchanger. First, we investigated the fan by comparing the total pressure efficiency when the fan was mounted in an indoor unit and unmounted as a standalone fan. We found that the mounted fan performed worse than the standalone fan. The difference between these conditions was whether the heat exchanger was around the fan. Next, to determine the appropriate diameter, the performance of the mounted fan was evaluated by measuring its efficiency and the fan power. The diameter with the highest efficiency differed from the diameter with the lowest fan power. Because of this, the fan performance was strongly affected by the heat exchanger and the vortex. When the standard deviation of the air flow distribution in the heat exchanger was evaluated, the diameter with the lowest standard deviation was the same as the diameter with the lowest fan power. Since the standard deviation needs to be reduced to improve the performance of both the fan and the heat exchange cycle, the mounting conditions need to be considered to determine the fan shape. Thus, the flow field around the fan was visualized, and the velocity distributions for the investigated diameters were compared. We found the distance between the fan and the heat exchanger was an important factor determining the performance. A fan with the most appropriate diameter was prototyped to evaluate the fan performance. Results revealed it used 3% less power than a standard-diameter fan.
Oil Aeration and Degassing Measurements for the Study of Aero-Engine Oil Pump Performance in Cavitation
Authors: Ippoliti Laurent , Vincké Joëlle , Hendrick Patrick
Published: October 2017

Cavitation combined with degassing strongly affect the pump performance in low-pressure operation. The understanding of oil aeration and degassing mechanisms is of great interest to explain and model the pump performance. This paper presents the techniques used for the measurement of the degassing and aeration phenomena applied to turbine lubrication oil. The measurement principle is to cause oil to degas and measure the flow density, which indicates the volume of degassed air and the oil aeration. The density was experimentally measured with two devices, one based on Coriolis forces and one on X-ray transmission. The paper describes and discusses the results obtained for various operating conditions and cases, such as constant aeration, degassing transient (pressure decrease) and aeration transient (pressure increase). The transient results fit exponential laws which give the asymptotical values and the time constant of the phenomenon. The comparison of the two techniques is also discussed.
Lumped Parameter and Three-Dimensional CFD Simulation of a Variable Displacement Vane Pump for Engine Lubrication
Authors: Rundo Massimo , Altare Giorgio
Published: October 2017

The paper describes the modelling and the experimental tests of a variable displacement vane pump for engine lubrication. The approach used for the simulation has involved 3D commercial tools for tuning a 0D customized model implemented in the LMS Amesim® environment. Different leakage paths are considered and the axial clearances are variable to take into account the deformation of the pump cover, calculated through a finite element analysis with ANSYS®. The vane tip clearances are calculated as function of the dynamic equilibrium equation of the vanes. The displacement control takes into account the internal forces on the stator due to the pressure in all variable chambers and to the contact force exerted by the vanes. The discharge coefficients in the resistive components have been tuned by means of a complete 3D transient model of the pump built with PumpLinx®. The tuned 0D model has been proved to be reliable for the determination of the steady-state flow-speed and flow-pressure curves, with a correct estimation of the internal leakages and of the pressure imposed by the displacement control. The pump has been also tested using a simplified circuit and a fair agreement has been found in the evaluation of the delivery pressure ripple.
DNS of Turbulent Bubbly Flows in Plane Channels Using the Front-Tracking Algorithm of TrioCFD
Authors: Bois G. , du Cluzeau A.
Published: October 2017

Two-phase turbulence is studied using DNS of upward turbulent bubbly flows in a plane channel. Fully deformable monodispersed bubbles are tracked by the Front-Tracking algorithm implemented in TrioCFD code on the TRUST platform. Two sets of fluid properties are used. Firstly, two simulations are performed with virtual fluids at a low void fraction of 3% and for a Reynolds friction number of 127 to benchmark our code against [1]. Good agreements are obtained for both deformable and spherical cases. A third simulation closer to pressurized water reactor (PWR) conditions was performed at higher void fraction and Reynolds number to push the limits of DNS capabilities.

DNS results are averaged (i) to provide reference profiles for an up-scaling methodology towards RANS two-fluid models and (ii) to analyze the equilibrium between buoyancy, surface tension, viscous and turbulent shear at statistically steady-state. Surface tension forces and turbulence are essentials to capture the equilibrium. Their accurate modeling is the key to velocities and void fraction predictions in averaged codes. Our analysis reveals the important role of surface tension, not only in the determination of the bubble shapes, but also as a source of local imbalance of the momentum transfer between phases. More advanced models considering interfacial energy are necessary to predict these flows.
Transient Pressure Pulsations of a Model Pump-Turbine During Power Failure
Authors: Hu Jinhong , Zeng Wei , Yang Jiandong , Tang Renbo
Published: October 2017

Pump-turbine can operate in either pump mode or turbine mode. The quick response to load changes as well as the ability to store energy makes it essential to the stability of power grid. When a pump-turbine works in different condition, flow-induced instabilities occur, including Rotor Stator Interaction (RSI) between the runner and vanes, vortex formations and back flow regions. To understand these complicated flow dynamics, experimental and numerical investigations have been conducted by many researchers. Among these researches, many experiments on model test rigs are mainly focused on steady state, and knowledge for instabilities during transients is still lacking. In this paper, power failure experiments with constant guide van opening are conducted on an open-loop test rig. During the process, the operating point of the pump-turbine in the 4 quadrant characteristics moves from pump region through the brake region, turbine region to turbine brake region. Finally the pump-turbine settled down at runaway rotational speed. In our experiments, flow rate, rotational speed, torque, pressure in the spiral casing and the draft tube inlet are measured. Especially, dynamic pressure sensors mounted in the guide vane channels are used to measure transient pressure pulsations. Measured data are analyzed in both time domain and frequency domain. Results indicate that during power failure pressure pulsations in the vane channels vary significantly with the operating conditions. In the pump region, pressure pulsations are mainly composed of RSI. In the brake region, intensive stochastic noises occur, and the amplitude of RSI rises. In the turbine region, the magnitude of pressure pulsations drops sharply as the noise intensity goes down. In the turbine brake region, significant noises appear, and the amplitude of RSI increases dramatically.
Research on the Geometry Parameters of Diffuser Vane Influence on the Performance of Bulb Tubular Pumping System
Authors: Jin Yan , Wu Junxin , Chen Hongcheng , Liu Chao
Published: October 2017

Diffuser vane of tubular pump is different with that of the axial flow pump, since the diffusion angle after the impeller is larger than as usual, which is an important part of bulb tubular pump system. By calculating the hydraulic loss of each part of bulb tubular pump system, it is found that the hydraulic loss of diffuser vane is in large proportion of the whole hydraulic loss. For this situation, focuses on the design parameters of diffuser vane such as diffuser vane length, unilateral edge diffusion angle, equivalent diffusion angle are necessary. In this paper, CFD method is used to simulate the turbulent flow in a bulb tubular pumping system with two different diffuser vanes. The three dimensional flow fields in the whole passage of pumping system with different diffuser vanes are obtained. The results show that all the main geometry parameters of the diffuser vane design affect the performances of tubular pumping system, it should be chosen the parameters reasonably based on the actual situation.
Computations of Buoyancy Driven Motion of a Single Droplet in Another Immiscible Liquid
Authors: Homma Shunji , Yoshikawa Tamaki
Published: October 2017

Buoyancy driven motion of a single droplet in another quiescent fluid was simulated by a Front-Tracking method. The rising velocity and the projected area of the droplet were obtained in spherical, ellipsoidal, and wobbling regimes. Form and skin drag forces were calculated by integrating pressure distribution and velocity profiles along the interface of the droplet. Drag coefficient was obtained from those values when the rising velocity reached the terminal velocity. The scaling for drag of a liquid droplet was compared with the theoretical model. When the viscosity of the droplets was lower than that of the surrounding fluid, the drag coefficients can be predicted by the model for the limiting case of gas bubbles. When the viscosity of the droplets was larger than that of the surrounding fluid, on the other hand, the drag coefficients can be predicted by the model when solid particles are assumed.
Pipe Inclination Effects on Slug Flow Characteristics of High Viscosity Oil-Gas Two-Phase Flow for Near Horizontal Pipes
Authors: Ekinci Samet , Aydin T. B. , Sarica C. , Pereyra E. , Kim T.
Published: October 2017

An experimental study of the inclination angle (±2° from horizontal) effects on high viscosity oil and gas two-phase flow has been conducted, and the available multiphase flow models/correlations have been evaluated using the acquired data.

The effect of pipe inclination on the slug flow characteristics of highly viscous oil-gas two-phase flow was studied based on 1,040 data points covering a wide range of experimental conditions and liquid viscosities in a 50.8-mm-ID pipe at 2° downward and upward inclinations from horizontal. The oil viscosity ranged from 155 cP to 587 cP. Superficial liquid and gas velocities varied from 0.1 m/s to 0.8 m/s and from 0.1 m/s to 5 m/s, respectively. The basic two-phase flow parameters and slug flow characteristics have been analyzed and compared with the past studies conducted for near horizontal pipes.
Improving LPG Pump Efficiency by Considering Variant Physical-Properties of Liquefied Petroleum Gas
Authors: Lara-Rodriguez G. , Begovich O. , Naredo J. L.
Published: October 2017

In a Liquefied Petroleum Gas (LPG) plant, the gas is received, stored, and finally, pumped to tanker trucks for distribution to consumers. In the pumping stage, a reduction in the efficiency of the pump for values below the density of the LPG is observed. As an option to resolve this problem when pumping LPG with varying density, this analysis evaluates a temperature control system in the plant’s pipeline by means of the installation of heat exchange equipment, attempting to reduce the temperature of the LPG. The theoretical data that the density of the liquid corresponds to 0.540kg/m3 at 288.65K is taken into account, supposing that if the temperature of the liquid can be reduced, the density of the LPG can be increased, thus improving the efficiency of the pump.

In this research, a methodology of dimensional analysis is used to combine real operating conditions and simulations on commercial grade Computational Fluid Dynamics (CFD) software; it is proposed to cool the liquid gas stored in the LPG plant during its trajectory from the storage spheres to the pumping equipment.

Therefore, the research being reported in this paper focuses on a modification to the LPG pumping process, installing a heat exchanger as an alternative or means to compensate for the loss of efficiency in LPG pumps and evaluating its application in the hydrocarbons industry.
Aerodynamic Design and Optimization of Pipe Diffuser for a High-Loading Centrifugal Compressor
Authors: Yang Xi , Jin Dong-hai , Gui Xing-min
Published: October 2017

Pipe diffuser draws more attentions these years as the stage pressure ratio and loads grow, since it is known that the pipe diffuser has a superior performance to the traditional vane diffuser as the diffuser inlet flow field is transonic or supersonic. Generally speaking, when the pressure ratio is high enough to give rise to the emergence of a critical cross-section, it would usually be in the diffuser, closing to the leading edge other than in the impeller. Therefore, the diffuser would have a significant impact on stage choke margin and its performance while be difficult to design and to match the impeller with satisfaction. To address the problem, a preliminary geometry design method for pipe diffuser is presented in this paper. In this paper, the performance and flow field analysis are based on numerical simulation carried out by Numeca, a commercial simulation software. For verified the calculated results′ reliability and grid independence, corresponding calculations and comparisons are conducted and discussed. Then, the performance of stage with pipe diffuser is compared with the stage with vane diffuser. Next, the specific effects of incidence on the performance and flow field are analyzed and discussed respectively. At last, an optimized aerodynamic structure of pipe diffuser is presented. As shown in the CFD results, the stage peak isentropic efficiency can reach up to 83.65% with the stage total pressure ratio slightly increased from 6.50 to 6.78, which means 4.29% of isentropic efficiency was raised by substituting the pipe diffuser for the vane diffuser.
Transient Lift on a Blade During Orthogonal Vortex Cutting
Authors: Saunders D. Curtis , Marshall Jeffrey S.
Published: October 2017

Vortex cutting imposes significant forces on blades in applications such as wind turbines operating in the wake of upstream turbines, helicopter rotor vortex impingement on the tail rotor, intake vortex interaction with a pump impellor, and streamwise vortex ingestion into a submarine propeller. The transient lift on a blade during orthogonal cutting of a vortex with non-zero axial flow was examined in the current paper using a combination of scaling theory, an analytical solution for instantaneous cutting and full Navier-Stokes simulations. The paper focuses on two distinct forces that occur during vortex cutting — the transient lift force that occurs during penetration of the blade leading edge into the vortex core and the steady-state lift force associated with the difference in vortex core radius over the blade surface. We show that the maximum value of the lift coefficient for the transient blade penetration force is proportional to the impact parameter and inversely proportional to the axial flow parameter. This observation is used to collapse predictions of the full Navier-Stokes simulations for lift coefficient over a wide range of values of the governing dimensionless parameters.
Investigation on Pulsating Flow Effect of a Turbocharger Turbine
Authors: Ding Zhanming , Zhuge Weilin , Zhang Yangjun , Chen Hua , Martinez-Botas Ricardo
Published: October 2017

Turbocharger turbines in internal combustion engines operate under highly pulsating flow conditions. The pulsating inflow has a complicated interaction with the turbine flow field and generates strong unsteadiness across the turbine stage, which produces oscillatory behavior and renders turbine performance distinct from that under steady conditions. However, the unsteady effect of the pulse flow is not considered when matching turbocharger turbines to engines due to the lack of effective simulation tools and unsteadiness criterion.

In this paper, a one-dimensional (1D) unsteady turbine model is proposed which could consider the volute curvature and preserve circumferential non-uniformity at rotor inlet. A parametric investigation of the response of a turbocharger turbine to inlet pulses is conducted based on the 1D model. The effects of various pulse parameters such as the amplitude, load, and frequency on the unsteady performance loops are studied. The influence of turbine operating conditions as the average inlet temperature and rotating speed on turbine unsteady performance is assessed. A dimensionless unsteadiness criterion Λ is used to correlate the relative importance of turbine unsteadiness. Results show that Λ is an effective criterion to judge the relative importance of unsteadiness. The investigation demonstrates turbine behaviors under different pulsating flow conditions, and strengthens the understanding of pulsating flow effect on turbine unsteady performance.
Rotor Stability Evaluation for High Pressure Multi-Stage Pump by Excitation Diagnosis Method
Authors: Peng Shichao , Arai Akira , Fukuchi Takaki , Katayama Taiju , Matsushita Osami
Published: October 2017

High pressure multi-stage pump is one of the most important machinery in various plants. Due to the high rotational speed, there are cases where excessive vibration problems occur. Especially, the self-excited vibration arises from the fluid force, which exists within the clearance of the oil film bearings and balancing drum (annular seal). In order to evaluate the rotor system stability, we developed an excitation method based on Bently-Muszynska model, and applied this method to the air test and water test. Through the test results, the onset (threshold) of instability (self-excited vibration) can be evaluated by the rotor system natural frequency and the fluid average angular circumferential velocity within the clearance of the bearings and balancing drum. Moreover, the balancing drum had a significant effect on the rotor stability, and the resulting frequency of the self-excited vibration matched the fluid average angular circumferential velocity in the balancing drum.
Capability Assessment of Five Different RANS-Based Turbulence Models to Simulate the Various Regions of Slot Turbulent Impingement Jet Flow
Authors: Charmiyan Mahmoud , Azimian Ahmed-Reza , Shirani Ebrahim , Aloui Fethi
Published: October 2017

In this paper, impingement of a turbulent rectangular flow to a fixed wall is investigated. The jet flows from bottom-to-top and the output jet Reynolds is 16000. The nozzle-to-plate distance is equal to 10 (H/e = 10). Five turbulence models, including k-ε, RNG k-ε, k-ω SST, RSM and v2f model have been used for two-dimensional numerical simulation of the turbulent flow. Because of the complexities of the impingement flow, such as curved streamlines, flow separation, normal strains and sudden deceleration in different areas, different turbulence models are proposed to simulate different regions of the flow. To investigate the capability of these turbulence models in simulating different regions of the impinging jet, the mean flow velocity field and turbulent kinetic energy are extracted and compared with the experimental data of a two-dimensional particle image velocimetry (PIV). The calculated error of these five turbulence models was presented for the various flow regions, while it have not been clearly investigated earlier. Results indicate the highest conformity of the v2f model with the experimental data at the jet centerline. However, this model does not predict well the flow at the shear layer and wall-jet areas. RSM Gibson and Lander model has the highest conformity with the experimental data in these regions.
POD Analysis of the Wake Development of a Pivoted Circular Cylinder Undergoing Vortex Induced Vibrations
Authors: Marble E. , Morton C. , Yarusevych S.
Published: October 2017

Vortex Induced Vibrations (VIV) of a pivoted circular cylinder with two degrees of freedom are investigated experimentally, focusing on quantifying the wake topology. Experiments are performed in a water tunnel for a pivoted cylinder with a fixed mass ratio of 10.8, moment of inertia ratio of 87.0–109.5, and a diameter-based Reynolds number of 3100. The reduced velocity was varied from 4.42 to 9.05 by varying the natural frequency of the structure. Velocity measurements were performed via time-resolved, two-component Particle Image Velocimetry (PIV), synchronized with cylinder displacement measurements. Time and phase-averaging are employed to analyze the wake development and relate it to the structural response. Proper Orthogonal Decomposition (POD) is utilized to gain insight into the development of coherent structures in the cylinder wake. The observed shedding patterns agree well with the Morse & Williamson [1] shedding map except for the cases at the boundary between 2P and non-synchronized shedding. The results show that the cylinder follows an elliptical trajectory with equal frequency of oscillation in streamwise and transverse directions. For the 2P regime, the tilt and direction of trajectory affect the formation and development of vortices in the wake. This results in a distinct asymmetry about the wake centerline in time-averaged statistics.
Numerical Study on Flow Characteristics in High Multi-Stage Pressure Reducing Valve
Authors: Chen Fu-qiang , Gao Zhi-xin , Qian Jin-yuan , Jin Zhi-jiang
Published: October 2017

In this paper, a new high multi-stage pressure reducing valve (HMSPRV) is proposed. The main advantages include reducing noise and vibration, reducing energy consumption and dealing with complex conditions. As a new high pressure reducing valve, its flow characteristics need to be investigated. For that the valve opening has a great effect on steam flow, pressure reduction and energy consumption, thus different valve openings are taken as the research points to investigate the flow characteristics. The analysis is conducted from four aspects: pressure, velocity, temperature fields and energy consumption. The results show that valve opening has a great effect on flow characteristics. No matter for pressure, velocity or temperature field, the changing gradient mainly reflects at those throttling components for all valve openings. For energy consumption, in the study of turbulent dissipation rate, it can be found that the larger of valve opening, the larger of energy consumption. It can be concluded that the new high multi-stage pressure reducing valve works well under complex conditions. This study can provide technological support for achieving pressure regulation, and benefit the further research work on energy saving and multi-stage design of pressure reducing devices.
Evaluation of the Effectiveness of a Coastal Wave Reduction and Sediment Retention Structure Using CFD Simulations
Authors: Dabelow Steven , Zhang Ning
Published: October 2017

The Louisiana coast experiences significant erosion due to wave actions. There are wetlands and marshes located in the coastal areas, however loss of these wetlands is a major threat. Although coastal waves and floods cause erosion, they do carry sediments, which can potentially counter-act some of the wetland losses. Innovative shoreline protection designs that reduce the wave actions but still allow sediments to travel through could be very beneficial. This research aims to evaluate the effectiveness of the wave reduction and sediment retention of several such designs using CFD simulations. CFD simulations were used to determine the alternations of the wave characteristics and the sediment transport with the designed structures. Small scale experiments of such designs will be conducted in a wave tank facility to validate the modeling results. The research aims to disclose the detailed physics of the flow and sediment transport in this complicated flow-structure interaction problems, and, based on the discoveries, we will provide suggestions to improve the current design to enhance the performance significantly.
Reduction Method for the Secondary Flow Loss in Turbine Cascade
Authors: Mizuguchi S. , Kusano K. , Oyama H. , Kawata Y.
Published: October 2017

The aerodynamic loss accounted to the secondary flow, or secondary loss, is one of the most prominent cause of the internal losses in turbine cascades. Secondary losses are mostly due to the interaction of Horse-Shoe Vortex and endwall crossflow. Authors have developed a so called endwall fence to reduce the secondary loss in gas turbine cascade by mitigating this interaction. However, the improvements resulting by the application of this method to a steam turbine cascade proved to be not so remarkable as for the gas turbine cascade.

By conducting total pressure measurements at the endwall, previous results showed that the stream wise evolution of the losses presents two peaks; Horse-Shoe Vortex peak and crossflow peak. The abovementioned endwall fence is blocks the Horse-Shoe Vortex, but its screening effect on the crossflow is not sufficient. So in this research the use of two kinds of fences is proposed to reduce the secondary loss: one is to block the pressure side leg of the Horse-Shoe Vortex, the second is to block and guide the crossflow, which starts from the middle of the blade passage, toward the outlet. Therefore, they are called respectively Horse-Shoe Vortex fence and crossflow fence.

The tests are carried out using the wind tunnel cascade and the test fences are made by 3D printer. The total loss is estimated by means of an automatically moving pitot tube located downstream the cascade. Many kinds of fences are tested and the optimum fence shape and position to minimize the secondary loss is obtained.
Effects of a Groove Patterned Cooling Tube on the Film Cooling Performance of a Gas Turbine Blade
Authors: Lee Yeon-Ho , Kim Youn-Jea
Published: October 2017

A high working fluid temperature in a gas turbine is required to improve its efficiency. However, high temperatures also reduce turbine blade durability. Film-cooling is one blade cooling method to control gas turbine blade temperature. In this study, film cooling performance was numerically investigated with various configurations of a groove patterned cooling tube. The CO2 blowing ratio of the cooling fluid was varied from 0.6 to 1.4 with 0.2 intervals. The numerical analysis was conducted using the ANSYS CFX ver. 16.1 commercial code. The film cooling efficiency and pressure distribution were graphically depicted and analyzed to derive the groove configuration with the highest film cooling efficiency. In particular, the flow field on the turbine blade with the circular groove configuration showed more uniform distribution compared to the reference model.
A Critical Comparison of Numerical and Experimental Results for the Examination of a Cascade Consisting of NACA 65-010 1% Profiles
Authors: Baum Andreas , Berger Constantin , Landfester Christian , Böhle Martin
Published: October 2017

Numerical and experimental investigations through different spans of the rotor are a common approach in turbo machinery design. As the aerodynamic quality of rotor blades is crucial for turbo machinery’s efficiency, mass-averaged loss coefficients ζ and turning angles Δβ are of particular interest. Using the example of commonly used NACA-65 profiles, a comparison between the results obtained by those methods should investigate whether Computational Fluid Dynamics (CFD) applying the Transition SST turbulence model delivers sufficiently accurate results regarding both 2D and 3D modeling approaches. The comparison is supplemented by the singularity method based on the potential theory as well as historical data provided by NACA.

While CFD produced a noticeable offset for some angle configurations, the 2D results of Δβ were in good agreement for singularity method, historical data and experimental investigations on the center line of the cascade supporting the validity of the measurement. Although significant deviations were also found for ζ, it can be stated that CFD reproduced the qualitative course sufficiently for both variables considered. A similar picture emerges from the 3D comparison: Despite noticeable deviations in quantitative terms, a good correspondence was found for both variables regarding local and mass-averaged values.
Low-Memory Reduced-Order Modelling With Dynamic Mode Decomposition Applied on Unsteady Wheel Aerodynamics
Authors: Kiewat Marco , Haag Lukas , Indinger Thomas , Zander Vincent
Published: October 2017

Wheel aerodynamics has a major impact on the overall aerodynamic performance of a vehicle. Different vortex excitation mechanisms are responsible for the induced forces on the geometry. Due to the high degree of complexity, it is difficult to gain further insight into the vortex structures at the rotating wheel. Therefore, wheel aerodynamics is usually investigated using temporally averaged flow fields. This work presents an approach to apply a recently introduced low-memory variant of Dynamic Mode Decomposition (DMD), namely Streaming Total DMD (STDMD), to investigate temporally resolved simulations in greater detail. The performance of STDMD is shown to be comparable to conventional DMD for a rotating generic closed wheel simulation test case. By creating a Reduced-Order Model (ROM) using a comparably small amount of DMD modes, the amount of complexity in the flow field can be drastically reduced. Orthonormal basis compression, amplitude ordering and a newly introduced amplitude weighting method are analyzed for creating a suitable ROM of DMD modes. A combination of compression and ordering by eigenvalue-weighted amplitude is concluded to be best suited and applied to the Delayed Detached Eddy Simulation (DDES) of the rotating generic closed wheel and a production vehicle rim wheel. The most dominant flow structures are captured at frequencies between 18Hz and 176Hz. Leading modes for both geometries are found close to the wheel rotation frequency and multiples of that frequency. The modes are identified as recirculation modes and vortex shedding.
Modeling Shear Heating in the Hydrodynamic Lubrication of Crankshaft Journal Bearing of a High-Torque Diesel Engine Operating at a Low Speed
Authors: Naseer Saqib , Qasim Syed Adnan , Azim Raja Amer
Published: October 2017

Journal bearing plays a critical role in carrying the extensive transient hydrodynamic loads to prevent adhesive wear of crankshaft of a high-torque low-speed diesel engine. The nominal clearance between the shaft-pin and the bearing journal invites viscous shearing of the lubricant on the initiation of rotation at the time of low speed engine start up. Shear heating adversely affects the load carrying ability of the bearing by reducing its viscosity as a function of time. It invites physical contact and wear of bearing and the crankshaft compromising their designed life. In this work the 2-D Reynolds equation is used to model hydrodynamic lubrication phenomenon of crankshaft covering the steady state wedging and transient squeeze which are modeled under the lubricant flooding conditions. The viscous shear heating is modeled by solving energy equation encompassing 2-D convection and 1-D conduction phenomena. The lateral displacements are incorporated in the lubrication model to analyze the effects of secondary dynamics of crankshaft on viscous shearing and friction. The relationships between temperature, viscosity and density are defined to ascertain their effects on bearing lubrication at low engine speed. The numerical simulation results are analyzed for the complete 720-degree 4-stroke engine cycle at a low operating speed. The results show that viscous heating adversely affects the lubrication of journal bearing by significantly reducing the viscosity of lubricant film at low transient loads and speed. The study determines hydrodynamic pressures, temperature, density, viscosity and thermal conductivity of lubricant suitable to minimize the possibility of rupture and adhesive wear due to shear heating under the flooding conditions at a low initial engine speed. It will facilitate towards enhancing the life of crankshaft of a heavy-duty diesel engine.