The Piezoelectric Valve-Less Pump: Series and Parallel Connections

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Amos Ullmann ◽  
Yehuda Taitel
Keyword(s):  
Preferential Flow ◽  
Flow Direction ◽  
Open Circuit ◽  
Low Flow ◽  
Operational Conditions ◽  
Wide Range ◽  
Parallel Arrangement ◽  
In Series ◽  
Computational Fluid Dynamics Cfd ◽  
Parallel Connections

The piezoelectric valve-less pump is an attractive device to be used as a micropump for low flow rates. In these pumps, the nozzle/diffuser elements that have a preferential flow direction replace conventional valves, to direct the flow from the inlet to the outlet. This work is a study on the performance of such pumps when several of them (up to four) are combined for use in series and/or parallel arrangement. Two basic pumping configurations are considered: (a) pumping of fluid from low pressure to a higher pressure in an open circuit and (b) pumping of fluid in a closed circuit through a flow resistance. The performance analysis procedure developed is simple and quick and allows studying a wide range of operational conditions. Such an analysis is difficult to conduct using elaborate computational fluid dynamics (CFD) approach. The performance characteristics of the different combinations is reported and critically evaluated.

Novel Centrifugal Compressor Architecture for Wide-Range Operation: A Feasibility Assessment

2017 ◽  
Author(s):  
Eric M. Krivitzky ◽  
Louis M. Larosiliere
Keyword(s):  
Internal Combustion Engines ◽  
Critical Role ◽  
Stability Boundary ◽  
Current Approach ◽  
Low Flow ◽  
Engine Operation ◽  
Feasibility Assessment ◽  
Wide Range ◽  
In Series ◽  
Low Efficiency

Turbocharger compressor performance plays a critical role in the ability of advanced Internal Combustion Engines (ICE) to meet the required fuel economy and drivability targets. Increased use of exhaust gas recirculation (EGR) combined with engine downsizing has pushed compressor operation towards — and often beyond — the stability boundary. However, certain applications and market trends require that no compromise be made to the rated power conditions. This has led to a highly disparate set of requirements for a single turbocharger system resulting in much of the compressor map, including the highest-efficiency area, unused or underutilized. A large percentage of the drive cycle is spent operating the compressor at low flow rates and low pressure ratios, near the compressor surge line, in an area of low efficiency. Compromises in efficiency in critical regions of engine operation result from balancing the disparate requirements. A current approach to meeting these disparate flow targets is the use of two turbochargers in series that are sized such that the operating compressor efficiency is markedly improved. This paper introduces a novel, hybrid single-stage compressor architecture which aerodynamically matches the functions of a series sequential dual turbocharger compression system. The use of a variable flow rate inducer bypass can provide a throttleable work-adding alternate flowpath for high-flow conditions, essentially emulating an efficient large compressor when the bypass is open and a small compressor when the bypass is closed. Using the variable bypass, the low-flow performance improves through an aerodynamically regulated inducer that is tailored to this flow regime. An engineering feasibility assessment supported by CFD, vector diagram analysis, and structural FEA suggest a substantial potential for improved performance across a wide flow range with this novel architecture.

THE RESPONSE OF SEISMOMETERS IN SERIES AND PARALLEL CONNECTIONS

Geophysics ◽  
1959 ◽  
Vol 24 (1) ◽  
pp. 49-63
Author(s):  
A. J. Seriff
Keyword(s):  
Normal Modes ◽  
Angular Frequency ◽  
Open Circuit ◽  
Harmonic Oscillators ◽  
Sustained Oscillation ◽  
Small Current ◽  
Adjacent Pair ◽  
Second Mode ◽  
In Series ◽  
Parallel Connections

Two similar seismometers connected in series with a load exhibit two independent or “normal” modes of motion. In the first mode the two coils move so that the voltages generated are almost equal and in phase, producing a large current in the circuit and considerable damping of the motion. This is the mode normally considered in designing the external damping circuit for series seismometers. In the second mode the coils move nearly 180° out of phase, produce a relatively small current in the circuit, and, consequently, experience very little damping in addition to their open circuit damping. Strong initial excitation of this mode can produce a sustained oscillation damaging to later parts of the seismic record. The usual mathematical description of this system, i.e., two harmonic oscillators coupled through their damping terms, readily yields approximate expressions for the size and damping of the load current in the case of nearly identical seismometers with little internal damping. For example, two such seismometers connected to a load producing large damping for the first mode will exhibit a damping of only [Formula: see text] in the second mode. Here [Formula: see text] and [Formula: see text] are the angular frequencies of the two separate seismometers, ω is the average angular frequency, and f is the fraction of critical damping for the first mode. Two seismometers connected in parallel can have considerable electromagnetic damping in both modes of oscillation. For n seismometers in series, there are n−1 modes which may be poorly damped. The frequencies of these modes are distributed so that one lies between each adjacent pair of the original uncoupled frequencies. The damping in each mode is of the order of [Formula: see text]. The steady‐state characteristic can be readily examined using the seismometer equivalent circuits. The result is strongly dependent on the mode of excitation. For example, if two similar seismometers are connected in series but only one is excited, the frequency characteristic shows both a maximum near the rms of the two seismometer frequencies and a minimum at the frequency of the seismometer not excited.

scholarly journals The study of output current in photovoltaics cell in series and parallel connections

2020 ◽  
Vol 1 (1) ◽  
pp. 7-12
Author(s):  
Norlinda Binti Mohd Yusof ◽  
Annuar Bin Baharuddin
Keyword(s):  
Photovoltaic Effect ◽  
Photovoltaic Cells ◽  
Preliminary Observation ◽  
System Efficiency ◽  
Output Current ◽  
Current Clamp ◽  
Parallel Arrangement ◽  
In Series ◽  
Parallel Connections ◽  
Good Agreement

Photovoltaic cells in solar is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect.  In this work, series and parallel arrangement of the photovoltaic cells in solar system were investigated over a range of voltage, current and power. The data obtained were statistically analyzed to predict the optimal energy conservation of photovoltaic cells and finally experiments were conducted for verification.  The experiment designed is to observe the output current in both series and parallel PV cells arrangement with the output current of the three sets of photovoltaic cells (PV), with a minimum input supply of 18.7V DC and 8.82A respectively. Digital multimeter and current clamp meter are the main instruments used to measure the parameters in the experiment. The parameters for the circuit are analyzed based on the voltage, current, power and the efficiency of the system. Indeed, the output current and voltage for both arrangements were able to be used to derive the efficiency of the system and showed good agreement with the results from the preliminary observation.  It is shown that the efficiency of parallel arrangement is higher compare to the series. Therefore, considerable investigation towards the types of arrangements is of great importance since it can determine the better system efficiency when there are any faulty panels

scholarly journals The Problem of Accounting for Heat Exchange between the Flow and the Flow Part Surfaces When Modeling a Viscous Flow in Low-Flow Stages of a Centrifugal Compressor

2020 ◽  
Vol 10 (24) ◽  
pp. 9138
Author(s):  
Sergey Kartashov ◽  
Yuri Kozhukhov ◽  
Vycheslav Ivanov ◽  
Aleksei Danilishin ◽  
Aleksey Yablokov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Centrifugal Compressor ◽  
Calculation Model ◽  
Flow Coefficient ◽  
Low Flow ◽  
Relative Width ◽  
Adiabatic Wall ◽  
Flow Part ◽  
Computational Fluid Dynamics Cfd

In this paper, we review the problem of accounting for heat exchange between the flow and the flow part surfaces when creating a calculation model for modeling the workflow process of low-flow stages of a centrifugal compressor using computational fluid dynamics (CFD). The objective selected for this study was a low-flow intermediate type stage with the conditional flow coefficient Փ = 0.008 and the relative width at the impeller exit b2/D2 = 0.0133. We show that, in the case of modeling with widespread adiabatic wall simplification, the calculated temperature in the gaps between the impeller and the stator elements is significantly overestimated. Modeling of the working process in the flow part was carried out with a coupled heat exchanger, as well as with simplified accounting for heat transfer by setting the temperatures of the walls. The gas-dynamic characteristics of the stage were compared with the experimental data, the heat transfer influence on the disks friction coefficient was estimated, and the temperature distributions in the gaps between disks and in the flow part of the stage were analyzed. It is shown that the main principle when modeling the flow in low-flow stage is to ensure correct temperature distribution in the gaps.

scholarly journals Flow and Particle Modelling of Dry Powder Inhalers: Methodologies, Recent Development and Emerging Applications

Pharmaceutics ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 189
Author(s):  
Zhanying Zheng ◽  
Sharon Shui Yee Leung ◽  
Raghvendra Gupta
Keyword(s):  
Dry Powder Inhaler ◽  
Research Direction ◽  
Particle Methods ◽  
Future Research ◽  
High Dose ◽  
Dry Powder ◽  
Multi Scale ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Discrete Element Methods

Dry powder inhaler (DPI) is a device used to deliver a drug in dry powder form to the lungs. A wide range of DPI products is currently available, with the choice of DPI device largely depending on the dose, dosing frequency and powder properties of formulations. Computational fluid dynamics (CFD), together with various particle motion modelling tools, such as discrete particle methods (DPM) and discrete element methods (DEM), have been increasingly used to optimise DPI design by revealing the details of flow patterns, particle trajectories, de-agglomerations and depositions within the device and the delivery paths. This review article focuses on the development of the modelling methodologies of flow and particle behaviours in DPI devices and their applications to device design in several emerging fields. Various modelling methods, including the most recent multi-scale approaches, are covered and the latest simulation studies of different devices are summarised and critically assessed. The potential and effectiveness of the modelling tools in optimising designs of emerging DPI devices are specifically discussed, such as those with the features of high-dose, pediatric patient compatibility and independency of patients’ inhalation manoeuvres. Lastly, we summarise the challenges that remain to be addressed in DPI-related fluid and particle modelling and provide our thoughts on future research direction in this field.

The Dynamics of a Cantilevered Pipe Aspirating Fluid Studied by Experimental, Numerical and Analytical Methods

2010 ◽  
Author(s):  
Dana Giacobbi ◽  
Stephanie Rinaldi ◽  
Christian Semler ◽  
Michael P. Pai¨doussis
Keyword(s):  
Analytical Model ◽  
Low Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Computational Structural Mechanics ◽  
Cantilevered Pipe ◽  
The Galerkin Method ◽  
Csm Model ◽  
Ocean Mining ◽  
Flow Experiments ◽  
Flow Velocities

This paper investigates the dynamics of a slender, flexible, aspirating cantilevered pipe, ingesting fluid at its free end and conveying it towards its clamped end. The problem is interesting not only from a fundamental perspective, but also because applications exist, notably in ocean mining [1]. First, the need for the present work is demonstrated through a review of previous research into the topic — spanning many years and yielding often contradictory results — most recently concluding that the system loses stability by flutter at relatively low flow velocities [2]. In the current paper, that conclusion is refined and expanded upon by exploring the problem in three ways: experimentally, numerically and analytically. First, air-flow experiments, in which the flow velocity of the fluid was varied and the frequency and amplitude of oscillation of the pipe were measured, were conducted using different elastomer pipes and intake shapes. Second, a fully-coupled Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM) model was developed in ANSYS in order to simulate experiments and corroborate experimental results. Finally, using an analytical approach, the existing linear equation of motion describing the system was significantly improved upon, and then solved via the Galerkin method in order to determine its stability characteristics. Heavily influenced by a CFD analysis, the proposed analytical model is different from previous ones, most notably because of the inclusion of a two-part fluid depressurization at the intake. In general, both the actual and numerical experiments suggest a first-mode loss of stability by flutter at relatively low flow velocities, which agrees with the results from the new analytical model.

scholarly journals Exploring the physical controls of regional patterns of flow duration curves – Part 4: A synthesis of empirical analysis, process modeling and catchment classification

2012 ◽  
Vol 16 (11) ◽  
pp. 4483-4498 ◽  
Author(s):  
M. Yaeger ◽  
E. Coopersmith ◽  
S. Ye ◽  
L. Cheng ◽  
A. Viglione ◽  
...  
Keyword(s):  
Low Flow ◽  
Middle Portion ◽  
Qualitative Synthesis ◽  
Statistical Parameters ◽  
Regional Patterns ◽  
Flow Duration ◽  
Analysis Process ◽  
Wide Range ◽  
Physical Controls ◽  
Flow Duration Curves

Abstract. The paper reports on a four-pronged study of the physical controls on regional patterns of the flow duration curve (FDC). This involved a comparative analysis of long-term continuous data from nearly 200 catchments around the US, encompassing a wide range of climates, geology, and ecology. The analysis was done from three different perspectives – statistical analysis, process-based modeling, and data-based classification – followed by a synthesis, which is the focus of this paper. Streamflow data were separated into fast and slow flow responses, and associated signatures, and both total flow and its components were analyzed to generate patterns. Regional patterns emerged in all aspects of the study. The mixed gamma distribution described well the shape of the FDC; regression analysis indicated that certain climate and catchment properties were first-order controls on the shape of the FDC. In order to understand the spatial patterns revealed by the statistical study, and guided by the hypothesis that the middle portion of the FDC is a function of the regime curve (RC, mean within-year variation of flow), we set out to classify these catchments, both empirically and through process-based modeling, in terms of their regime behavior. The classification analysis showed that climate seasonality and aridity, either directly (empirical classes) or through phenology (vegetation processes), were the dominant controls on the RC. Quantitative synthesis of these results determined that these classes were indeed related to the FDC through its slope and related statistical parameters. Qualitative synthesis revealed much diversity in the shapes of the FDCs even within each climate-based homogeneous class, especially in the low-flow tails, suggesting that catchment properties may have become the dominant controls. Thus, while the middle portion of the FDC contains the average response of the catchment, and is mainly controlled by climate, the tails of the FDC, notably the low-flow tails, are mainly controlled by catchment properties such as geology and soils. The regime behavior explains only part of the FDC; to gain a deeper understanding of the physical controls on the FDC, these extremes must be analyzed as well. Thus, to completely separate the climate controls from the catchment controls, the roles of catchment properties such as soils, geology, topography etc. must be explored in detail.

Cerebral microdialysis monitoring: determination of normal and ischemic cerebral metabolisms in patients with aneurysmal subarachnoid hemorrhage

2000 ◽  
Vol 93 (5) ◽  
pp. 808-814 ◽  
Author(s):  
Mette K. Schulz ◽  
Lars Peter Wang ◽  
Mogens Tange ◽  
Per Bjerre
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Cerebral Ischemia ◽  
Delayed Cerebral Ischemia ◽  
Neuronal Injury ◽  
Low Flow ◽  
Cerebral Microdialysis ◽  
Intracerebral Microdialysis ◽  
Content Type ◽  
Wide Range ◽  
Fine Print

Object. The success of treatment for delayed cerebral ischemia is time dependent, and neuronal monitoring methods that can detect early subclinical levels of cerebral ischemia may improve overall treatment results. Cerebral microdialysis may represent such a method. The authors' goal was to characterize patterns of markers of energy metabolism (glucose, pyruvate, and lactate) and neuronal injury (glutamate and glycerol) in patients with subarachnoid hemorrhage (SAH), in whom ischemia was or was not suspected.Methods. By using low-flow intracerebral microdialysis monitoring, central nervous system extracellular fluid concentrations of glucose, pyruvate, lactate, glutamate, and glycerol were determined in 46 patients suffering from poor-grade SAH. The results in two subgroups were analyzed: those patients with no clinical or radiological signs of cerebral ischemia (14 patients) and those who succumbed to brain death (five patients).Significantly lower levels of energy substrates and significantly higher levels of lactate and neuronal injury markers were observed in patients with severe and complete ischemia when compared with patients without symptoms of ischemia (glucose 0 compared with 2.12 ± 0.15 mmol/L; pyruvate 0 compared with 151 ± 11.5 µmol; lactate 6.57 ± 1.07 compared with 3.06 ± 0.32 mmol/L; glycerol 639 ± 91 compared with 81.6 ± 12.4 µmol; and glutamate 339 ± 53.4 compared with 14 ± 3.33 µmol). Immediately after catheter placement, glutamate concentrations declined over the first 4 to 6 hours to reach stable values. The remaining parameters exhibited stable values after 1 to 2 hours.Conclusions. The results confirm that intracerebral microdialysis monitoring of patients with SAH can be used to detect patterns of cerebral ischemia. The wide range from normal to severe ischemic values calls for additional studies to characterize further incomplete and possible subclinical levels of ischemia.

Numerical Simulation of Droplet Generation in Series Co-Flow Capillaries

2009 ◽  
Author(s):  
Yanxi Song ◽  
Jinliang Xu
Keyword(s):  
Reynolds Number ◽  
Disperse Phase ◽  
Weber Number ◽  
Three Dimensional ◽  
Continuous Phase ◽  
Disperse Flow ◽  
Double Emulsions ◽  
Wide Range ◽  
In Series ◽  
Dispersed Phases

We study the production and motion of monodisperse double emulsions in microfluidics comprising series co-flow capillaries. Both two and three dimensional simulations are performed. Flow was determined by dimensionless parameters, i.e., Reynolds number and Weber number of continuous and dispersed phases. The co-flow generated droplets are sensitive to the Reynolds number and Weber number of the continuous phase, but insensitive to those of the disperse phase. Because the inner and outer drops are generate by separate co-flow processes, sizes of both inner and outer drops can be controlled by adjusting Re and We for the continuous phase. Meanwhile, the disperse phase has little effect on drop size, thus a desirable generation frequency of inner drop can be reached by merely adjusting flow rate of the inner fluid, leading to desirable number of inner drops encapsulated by the outer drop. Thus highly monodisperse double emulsions are obtained. It was found that only in dripping mode can droplet be of high mono-dispersity. Flow begins to transit from dripping regime to jetting regime when the Re number is decreased or Weber number is increased. To ensure that all the droplets are produced over a wide range of running parameters, tiny tapered tip outlet for the disperse flow should be applied. Smaller the tapered tip, wider range for Re and we can apply.

Sign in / Sign up

Export Citation Format

Share Document