Simple Flow Control Research Articles

Flowmeter-free chemical dosing control system: A new volume measurement-based design offers cost-effective and reliable operations

This study discusses a new volume measurement-based chemical dosing control system design and performance analysis. In conventional dosing systems, chemical dosing control is carried out by an analogue or digital flowmeter with different operating principles placed on the pump outlet line. In these systems, the amount of dosing chemicals is controlled based on the feedback received via the flowmeter. To obtain a steady measurement with flowmeters, the pulsations from the dosing pumps must be dampened and the line pressure must be kept constant with pressure regulators. In the proposed dosing system, the measurement of the dosing chemical is performed via the pump suction line, making it independent of the pump output character and line pressure. The amount of dosing chemicals is measured instantaneously by placing a volume-level measurement tube on the pump suction line. The system is designed to handle the metering of viscous fluids at an operating pressure of (0–400) bar and a flow rate of 10 L/h. The proposed and the conventional systems have been experimentally tested and performance data have been obtained at various operating pressure and flow rates. Experimental results confirmed that a simple and flowmeter-free flow control system is achieved, thanks to the low component count. Furthermore, a cost saving of 40 % has been achieved compared to conventional systems.

Isolated UIPC-intertied AC-DC microgrids operation with novel dynamic flexible loads model

This work discusses the islanding operation of hybrid microgrids (HµGs) interconnected by a unified interphase power controller (UIPC). It is illustrated that considering islanding operation of HµG, the problem of power dispatch among intertied AC and DC µGs, as well as voltage and frequency control, can be handled by UIPC. The power dispatch among various AC and DC µGs using UIPC is analyzed and formulated through defining a simple demand condition function (DCF). A new control structure is proposed for the series power converter of the UIPC which enjoys the robustness of sliding mode control (SMC) concept and adopts a new energy management system (EMS) with embedded decision-making. This provides a fast, robust, and simple power flow control unit which acts as a general supervisory system for the UIPC and islanding operation of HµG. Also, a novel generalized dynamic model for flexible loads has been proposed. These loads have been directly controlled through UIPC supervisory system here. The analytical response of the proposed flexible load model is discussed and further developed using the nonlinear autoregressive-moving-average artificial neural network (ANN) model. The Levenberg-Marquardt learning algorithm is used to train the network based on the model estimation error. Besides, a new model predictive-based optimal control scheme is proposed for the flexible load. Simulation results using MATLAB support the usefulness of the proposed UIPC-based islanded HµG platform.

G-Reactor at Micro-Plan

The stirrer reactor govern the industrial pharmaceutical productions up to the present, however the complex transmission systems may increase the costs exponentially with the power rates and the hermetic rector sealing. G-reactor improves the analogous reactors with simple pneumatic power device to heavy duty performances at high technological risks by pathogens and per substitution of complex transmissions by own-design; a single compression unit produces the sterile air to the power input of micro-plants and the oxygen of aerobic processes; important economic technical profits is foreseen; microplants distinguishes by small installations for compressed air and the services with overall automatic control available; the reliable performance for the human health, variable speed and standard impeller system, simple sterilization, safe sampling and supplies, foam-breaks to avoiding chemicals and simple automatic flow control distinguish the installations. The mathematical simulation of G-reactor performances to the mixing operations at gas-liquid systems to mass-transfer is shown; a solved example to a specific process illustrates the calculus fundamentals; the software enables the calculus of consumption parameters to the reactor scale-up and micro-plants of maximum capacity; the descriptive data analysis is discussed for the primary technical evaluations and general conclusions. The innovation is proposed for the small production scale of drugs and the unit operations of the chemical industry; a brief technical description of micro-plants and the production of sterile air may lead to the process engineering and the preliminary analysis of costs. The prophylactic treatment of the residual gas flow is shown.

Automated cellular stimulation with integrated pneumatic valves and fluidic capacitors.

Microfluidic technologies have proven to be a reliable tool in profiling dynamic insulin secretion from islets of Langerhans. Most of these systems rely on external pressure sources to induce flow, leading to difficulties moving to more elaborate systems. To reduce complexity, a microfluidic system was developed that used a single vacuum source at the outlet to drive fluidic transport of immunoassay reagents and stimulation solutions throughout the device. A downside to this approach is the lack of flow control over the reagents delivered to the islet chamber. To address this challenge, 4-layer pneumatic valves were integrated into the perfusion lines to automate and control the delivery of stimulants; however, it was found that as the valves closed, spikes in the flow would lead to abnormal insulin secretion profiles. Fluidic capacitors were then incorporated after the valves and found to remove the spikes. The combination of the valves and capacitors resulted in automated collection of insulin secretion profiles from single murine islets that were similar to those previously reported in the literature. In the future, these integrated fluidic components may enable more complex channel designs to be used with a relatively simple flow control solution.

A passive loss reduction method of square-to-square sudden expansions

Mechanical ventilation in edifices is a key contributor to the significant energy consumption of the building industry. Therefore, rational energy management in ventilation systems plays a major role in promoting the energy efficiency of buildings. The present investigation aims at the moderation of fluid mechanical losses – thus the overall energy expenditure of ventilation ducts – of a symmetric square-to-square sudden expansion, frequently found in ventilation systems. A simple passive flow control method with moderate manufacturing costs was proposed, and its efficiency was examined experimentally. The loss reducing appendages were short rectangular sheets of adjustable angle, so-called miniflaps, placed at the step edge of the sudden expansion. Flow characteristics were examined for a fully developed turbulent flow at the inlet of the sudden expansion, for an area ratio of 2.78 and a miniflap length of 0.4 step heights. The investigated Reynolds number range was Re = (0.37–1.82)·105, being representative of ventilation systems. Fluid mechanical losses were determined from wall static pressure measurements. Velocity and turbulence intensity fields were mapped with the help of a laser Doppler anemometer. The miniflaps successfully reduced the loss coefficient of the sudden expansion through quick uniformization of the velocity profile. The loss coefficient was reduced by an absolute value of 0.07–0.11, i.e. a relative value of 14%–25%, for an optimum miniflap angle of α = 12° ± 1°. Reattachment length was also reduced from 11 to 7 step heights in the wall-normal and from 14 to 13 step heights in the diagonal plane. The loss reducing capacity together with the compactness of the miniflaps and the overall reduction of the affected zone downstream of the element presents a competitive advantage of the miniflaps in the building industry, which is often characterized by limited space allowance.

Numerical Study on Rod Thrust Vector Control for Physical Applications

Mechanical thrust vector control is a classical and significant branch in the thrust vector control field, offering an extremely reliable control effect. In this article, steady-state and unsteady-state aerodynamic characteristics of the rod thrust vector control technology are numerically investigated in a two-dimensional supersonic nozzle. Complex flow phenomena caused by the penetrating rod in the diverging part of the supersonic nozzle are elucidated with the purpose of a profound understanding of this simple flow control technique for physical applications. Published experimental data are used to validate the dependability of current computational fluid dynamics results. A grid sensitivity study is carried through and analyzed. The result section discusses the impacts of two important factors on steady-state aerodynamic features, involving the rod penetration height and the rod location. Furthermore, unsteady-state flow features are analyzed under various rod penetration heights for the first time. Significant vectoring performance variations and flow topology descriptions are illuminated in full detail. While the rod penetration height increases, the vectoring angle increases, whereas the thrust coefficient decreases. As the rod location moves downstream close to the nozzle exit, the vectoring angle and thrust coefficient increase. In terms of unsteady-state aerodynamic effects, certain pressure oscillations occur upstream of the rod, which resulted from the expanding and shrinking of the upstream anticlockwise separation bubbles.

Cooling in Poor Air Quality Environments—Impact of Fan Operation on Particle Deposition

Environmental pollutants are a source for reliability issues across data center and telecommunications equipment. A primary driver of this is the transport and deposition of particle matter (PM$_{2.5}$, PM$_{10}$) on printed circuit boards, electronic components and heat exchange surfaces. This process is enhanced by turbulent air flows generated from cooling fans. Particle pollutants can persist after contemporary filtering, highlighting the importance of elucidating particle transport mechanisms and utilising this information to design robust equipment. This study investigates particle transport behaviour arising from axial fans operating under varied aerodynamic conditions. Transient, multi-phase numerical simulations were performed to model the flow of millions of microscale particles in air and determine their fate. Across a comprehensive range of fan operation conditions, from aerodynamic stall to free delivery, non-dimensional deposition velocities spanned an order of magnitude. Deposition profiles vary from monotonic to non-monotonic behaviour, influenced by local flow impingement, blade tip vortices, and shear velocity. A simple flow control solution that mitigates the factors influencing deposition has been demonstrated for equipment already deployed. The findings and numerical methods can be applied for the optimization of fan-cooled equipment intended for indoor and outdoor environments where air quality is poor, or pollution levels are high.

Influences of slotted blade on performance and flow structure of a transonic axial compressor

Main reason of compressor instability is boundary layer separation on the surface of blades. As one of flow control methods of the compressor, slotted blade has attracted many researchers’ attention because of its simple geometric structure and remarkable flow control effect. In order to evaluate its availability in the compressor, a type of convergent slot is designed to implement in a single-stage transonic axial compressor. Three configurations, i.e. rotor slot, stator slot and rotor-stator combined slot, are introduced to study the aerodynamic performance of compressor by numerical simulations. Furthermore, flow structures have been analyzed to explain the corresponding mechanism. The results show that overall stability margin of the compressor has been improved by flow control with slotted blade. Behavior of the rotor slot is better than that of the stator slot, but due to mass flow leakage in the slot, peak efficiency and chocking mass flow rate of the compressor are decreased by 1.18% and 3.8% respectively. The low momentum flow on pressure surface is sucked into the jet slot of stator blade, which improves the overall stability margin of 0.63%. The combined scheme with slotted rotor and slotted stator has obtained the best aerodynamic behavior with the increase of the overall stability margin of 2.83%. During the future research, main goal will be improvement of the compressor performance and extension of the mass flow rate range.

Active Flow Control of a Pump-Induced Wall-Normal Vortex With Steady Blowing

Abstract The emergence of a submerged vortex upstream of a pump can reduce pump intake efficiency and cause structural damage. In this study, we consider the use of active flow control with steady blowing to increase the pressure distribution within a single-phase pump-induced wall-normal vortex model, which is based on the Burgers vortex with a no-slip boundary condition prescribed along its symmetry plane. The goal of our control is to modify the vortex core velocity profile. These changes are sought to increase the core pressure such that detrimental effects on the pump are alleviated. Three-dimensional direct numerical simulations are performed to examine the dynamics of the vortex with the application of axial momentum injection at and around the root of the vortex. We find that the active flow control approach can effectively modify the wall-normal vortical structure and significantly increase the low-core pressure by up to 81% compared to that of the uncontrolled case. The result shows that the control setup is also effective when it is introduced in an off-centered manner. Compared to the unsteady blowing and suction-based actuation from our previous work (Liu, Q., An, B., Nohmi, M., Obuchi, M., and Taira, K., 2018, “Core-Pressure Alleviation for a Wall-Normal Vortex by Active Flow Control,” J. Fluid Mech., 853, p. R1.), the current steady control technique offers an effective and simple flow control setup that can support robust operations of pumps.

High water recovery and improved thermodynamic efficiency for capacitive deionization using variable flowrate operation

Water recovery is a measure of the amount of treated water produced relative to the total amount of water processed through the system, and is an important performance metric for any desalination method. Conventional operating methods for desalination using capacitive deionization (CDI) have so far limited water recovery to be about 50%. To improve water recovery for CDI, we here introduce a new operating scheme based on a variable (in time) flow rate wherein a low flow rate during discharge is used to produce a brine volume which is significantly less than the volume of diluent produced. We demonstrate experimentally and study systematically this novel variable flowrate operating scheme in the framework of both constant current and constant voltage charge-discharge modes. We show that the variable flowrate operation can increase water recovery for CDI to very high values of ∼90% and can improve thermodynamic efficiency by about 2- to 3-fold compared to conventional constant flowrate operation. Importantly, this is achieved with minimal performance reductions in salt removal, energy consumption, and volume throughput. Our work highlights that water recovery can be readily improved for CDI at very minimal additional cost using simple flow control schemes.

Rapid enumeration of CD4 + T lymphocytes using an integrated microfluidic system based on Chemiluminescence image detection at point-of-care testing.

An integrated microfluidic system has been developed for rapid enumeration of CD4 + T lymphocytes at point-of-care (POC) settings. A concise microfluidic chip, which consists of three separate chambers, respectively, for reaction, detection and waste storage, is developed to automate CD4 detection. To simplify CD4 + T lymphocyte enumeration, a single polycarbonate bead immobilized with CD4 antibody is adopted by the microfluidic chip to capture the CD4 antigen in the lysed testing sample. Desired performance is achieved by actuating the single bead for efficient mixing, as well as transferring it between different reaction chambers to reduce non-specific reaction. A controllable external magnetic field is applied to drive the single bead with a built-in ferrous core for different purposes. Chemiluminescence reaction is implemented in an independent chamber to reduce non-specific binding of enzyme. A simple flow control strategy is adopted to conveniently release the waste reagent into the waste storage chamber by just opening the vent hole without actively pumping. A sensitive CCD camera is used to collect the reaction signal by taking picture from the single bead, and then the signal intensity is further analyzed for CD4 + T lymphocyte enumeration. Experimental results show that rapid, convenient, accurate and low-cost CD4 + T lymphocyte enumeration can be obtained with the developed microfluidic system at POC test.

Scalable Synthesis of Sub-Nanosized Platinum-Reduced Graphene Oxide Composite by an Ultraprecise Photocatalytic Method

In this work, an industrially scalable method for a precisely controlled deposition of subnanosized metallic particles (e.g., platinum) on reduced graphene oxide has been developed. Partially reduced graphene oxide, a band gap engineered form of graphene, has been utilized for two purposes: the reduction of the metallic particles and a support layer. For the partial reduction, graphene oxide has been treated with a highly concentrated sodium hydroxide solution and the reduction process has been continued (and monitored) until obtaining a stable product. The chemical stability and band gap modulation process of the partially reduced graphene oxide have been discussed comprehensively. We have shown that the graphene oxide which also exhibits semiconducting properties is not a suitable choice as a photocatalyst material mainly because of its chemical instability and considerable photocorrosion. An innovative reactor with large-scale production capacity for pulsed UV illumination and continuous treatment of the reaction suspensions has been designed. A simple flow control in this reactor enables us to have precise control of the number of photoexcited electrons and consequently of the photodeposition of the subnanosized Pt particles.

Chaotic dynamics of large-scale structures in a turbulent wake

The dynamics of a 3D bimodal turbulent wake downstream a square-back Ahmed body are experimentally studied in a wind-tunnel through high-frequency wall pressure probes mapping the rear of the model and a horizontal 2D velocity field. The barycenters of the pressure distribution over the rear part of the model and the intensity recirculation are found highly correlated. Both described the most energetic large-scale structures dynamics, confirming the relation between the large-scale recirculation bubble and its wall pressure foot-print. Focusing on the pressure, its barycenter trajectory has a stochastic behavior but its low frequencies dynamics exhibit the same characteristics as a weak strange chaotic attractor system, with two well defined attractors. The low frequencies dynamics associated to the large-scale structures are then analyzed. The largest Lyapunov exponent is first estimated, leading to a low positive value characteristic of strange attractors and weak chaotic systems. Afterwards, analyzing the autocorrelation function of the time-series, we compute the correlation dimension, larger than two. The signal is finally transformed and analyzed as a telegraph signal showing that its dynamics correspond to a quasi-random telegraph signal. This is the first demonstration that the low frequencies dynamics of a turbulent 3D wake are not a purely stochastic process but rather a weak chaotic process exhibiting strange attractors. From the flow-control point of view, it also opens the path to more simple closed-loop flow control strategies aiming at the stabilization of the wake and the control of the dynamics of the wake barycenter.

Generation of digitized microfluidic filling flow by vent control

Quantitative microfluidic point-of-care testing has been translated into clinical applications to support a prompt decision on patient treatment. A nanointerstice-driven filling technique has been developed to realize the fast and robust filling of microfluidic channels with liquid samples, but it has failed to provide a consistent filling time owing to the wide variation in liquid viscosity, resulting in an increase in quantification errors. There is a strong demand for simple and quick flow control to ensure accurate quantification, without a serious increase in system complexity. A new control mechanism employing two-beam refraction and one solenoid valve was developed and found to successfully generate digitized filling flow, completely free from errors due to changes in viscosity. The validity of digitized filling flow was evaluated by the immunoassay, using liquids with a wide range of viscosity. This digitized microfluidic filling flow is a novel approach that could be applied in conventional microfluidic point-of-care testing.

Conditional forwarding: simple flow control to increase adaptivity for fully adaptive routing algorithms

Fully adaptive routing algorithm has been widely used by modern commercial supercomputers due to its high path diversity. However, fully adaptive routing algorithm is prone to deadlock especially when wormhole switching with non-atomic virtual channel (VC) allocation is employed. Non-atomic VC allocation means that a VC can be immediately allocated once the tail flit of last packet arrives. Duato's theory gives a general methodology for deadlock-free fully adaptive routing design by dividing VCs into escape and adaptive ones, and prohibiting packets from using adaptive VCs after using escape VCs. However, this prohibition usually induces adaptivity loss and performance degradation. To address these issues, we extend Duato's theory and propose conditional forwarding flow control (CFFC): for packet residing in escape VC and requesting adaptive VC, it can be forwarded if the requested adaptive VC has enough free buffers to hold the whole packet. By allowing packets to regain adaptivity, CFFC enables the design of a fully adaptive routing algorithm with high routing adaptivity. By supporting non-atomic VC allocation, CFFC maintains efficient VC utilization. We prove that CFFC will not introduce deadlock if the routing algorithm is deadlock-free using non-atomic VC allocation, i.e. the routing subfunction applied in escape VCs is connected and deadlock-free. Simulation results show that our proposed method exhibits higher VC utilization and performs averagely 14.8 % better than existing fully adaptive routing algorithms.

Simple Power Flow Control Method for Reducing the Power Source Capacity and Managing the Storage Energy for Hybrid Power Source Electric Vehicles

SUMMARYElectric railway vehicles require high electric power when powering and return high electric output when regenerating. Therefore, the fall in vehicle performance due to a voltage drop and the restriction on regenerative power due to a load shortage become problems in a dc‐electrified railway. Therefore, energy storage devices (ESDs) are mounted on vehicles to assist the power of powering operation and to absorb the power of regeneration. In recent years, various hybrid vehicles have been studied because the performance of ESDs has become good enough for them to be mounted on vehicles. Generally, the design of the controller is a complicated problem because the vehicle operates under various running conditions. In this paper, a simple controller for ESDs is designed in the frequency domain. This controller aims at smoothing the input power and at managing the ESD energy. The proposed controller is examined under various running conditions with numerical simulations.

Exploring Heterogeneous NoC Design Space in Heterogeneous GPU-CPU Architectures

Computer architecture is transiting from the multicore era into the heterogeneous era in which heterogeneous architectures use on-chip networks to access shared resources and how a network is configured will likely have a significant impact on overall performance and power consumption. Recently, heterogeneous network on chip (NoC) has been proposed not only to achieve performance comparable to that of the NoCs with buffered routers but also to reduce buffer cost and energy consumption. However, heterogeneous NoC design for heterogeneous GPU-CPU architectures has not been studied in depth. This paper first evaluates the performance and power consumption of a variety of static hot-potato based heterogeneous NoCs with different buffered and bufferless router placements, which is helpful to explore the design space for heterogeneous GPU-CPU interconnection. Then it proposes Unidirectional Flow Control (UFC), a simple credit-based flow control mechanism for heterogeneous NoC in GPU-CPU architectures to control network congestion. UFC can guarantee that there are always unoccupied entries in buffered routers to receive flits coming from adjacent bufferless routers. Our evaluations show that when compared to hot-potato routing, UFC improves performance by an average of 14.1% with energy increased by an average of 5.3% only.

A Necessary and Sufficient Condition for Deadlock-Free Message Routing in Communication Networks

Deadlocks are an important issue in the design and analysis of communication networks. Wormhole switching is a popular switching technique in direct networks. It refers to a simple flow control system in computer network that is primarily based on fixed links. It also reduces the latency and storage requirements on each node. Deadlock analysis of routing function is a manual and complex task. In the absence of contention, latencies are proportional to the sum of the packet length and the distances to travel. We propose an algorithm to analyze the deadlock in communication networks. The deadlock-free routing algorithm is the first to automatically check a necessary and sufficient condition for deadlock-free routing. Our algorithm performs Effective analysis in this network.

Simple Power Flow Control Method for Reducing the Power Source Capacity and Managing the Storage Energy for Hybrid Power Source Electric Vehicles

SUMMARY Electric railway vehicles require high electric power when powering and return high electric output when regenerating. Therefore, the fall in vehicle performance due to a voltage drop and the restriction on regenerative power due to a load shortage become problems in a dc-electrified railway. Therefore, energy storage devices (ESDs) are mounted on vehicles to assist the power of powering operation and to absorb the power of regeneration. In recent years, various hybrid vehicles have been studied because the performance of ESDs has become good enough for them to be mounted on vehicles. Generally, the design of the controller is a complicated problem because the vehicle operates under various running conditions. In this paper, a simple controller for ESDs is designed in the frequency domain. This controller aims at smoothing the input power and at managing the ESD energy. The proposed controller is examined under various running conditions with numerical simulations.

Improvement of steel billet cleanliness and thermal responses of multiple strands through fluid flow control

Fluid flow of liquid steel in a six-strand billet tundish using a simple squared advanced pouring box (APB) promotes the formation of heavy skulls, particularly in the corners of the vessel, and heterogeneous product cleanliness and thermal responses in the strands. To improve the flow patterns, two other APBs were designed and tested through water model tracer injection techniques, ultrasound velocimetry and mathematical simulations. The first APB is the actual design. The second APB maintains the same geometry but is equipped with two circular orifices with zero angle respect to the horizontal at each lateral side placed toward the tundish back wall. The third APB geometry is also squared with elliptic orifices with double upward angles also oriented to the tundish back wall. The first two devices induce long shearing–circulating flows, leaving stagnant regions inside the fluid bulk and particularly in the four upper corners of the tundish, which explains the existence of skulls in the actual tundish. The third device provides a long recirculating flow that eliminates all stagnant regions. Mathematical simulations have indicated that this flow carries energy, through convection mechanisms, toward the upper bath surface, indicating the elimination of skulls. Trials at the caster proved that all skulling problems were eliminated, and thermal and metallurgical evenness was reached using this simple flow control device.