Output Flow Rate Research Articles

Multi‐rate model predictive control algorithm for systems with fast‐slow dynamics

This study proposes a novel multi-rate model predictive control (MPC) scheme for linear discrete-time systems subject to input constraints. The proposed scheme consists of two control layers, acting at two different timescales. At a slow timescale, the outputs associated with the slow dynamics are steered to their reference values while at a fast timescale, a shrinking horizon MPC regulator is designed to refine the control action computed at the slow timescale. The proposed control scheme shows to be particularly useful, not only to control systems with different open-loop dynamics but also in cases when the controlled variables are required to have different responsiveness in a closed loop. Simulation results on a fire tube boiler example are reported, which indeed show that different dynamics can be efficiently imposed on the controlled variables, i.e. the boiler pressure and the water level, in the presence of variations of the disturbance represented by the steam output flow rate.

Design of a Portable Pneumatic Power Source With High Output Pressure for Wearable Robotic Applications

Despite the rapid advances in soft robotic actuation technologies, the main energy source that powers most wearable systems remains the conventional tethered stationary air compressor that greatly limits these systems’ applicability. Several portable pneumatic energy sources have been introduced; however, the limited maximum output pressure and flow rate, size and weight, large operational noise, and potential safety hazards must still be resolved before being applied to current wearable applications. In this study, we propose the design of a portable double-piston crank microcompressor that can generate up to a maximum gauge output pressure of 986 kPa and a maximum flow rate of 9.78 L/min, while maintaining a simple structure, static mass of 1.5 kg and not generating any safety hazards. The design requirements in terms of maximum pressure and flow rate were optimized based on wearable robotic applications. The sound intensity level generated by the developed microcompressor was approximately 65 dB, which can be used for long-term usage, at maximum flow rate when measured from a 0.5 m distance.

On-line solvent exchange system: Automation from extraction to analysis

Removal of organic solvent from sample extracts is required before analysis by reversed phase HPLC to preserve chromatographic performance and allow for bigger injection volumes, boosting sensitivity. Herein, an automated on-line extraction evaporation procedure is integrated with HPLC analysis. The evaporation occurs inside a 200 μm microfluidic channel confined by a vapor permeable membrane. A feedback control algorithm regulates evaporation rate keeping the output flow rate constant. The evaporation process across this membrane was firstly characterized with water/solvent mixtures showing organic solvent removal capabilities. This system allowed continuous methanol, ethanol and acetonitrile removal from samples containing up to 80% organic solvent. An evaporative injection procedure was developed demonstrating the use of the device for fully integrated extract reconstitution coupled to HPLC analysis, applied to analysis of the antibiotic chloramphenicol in milk samples. Sample reconstitution and collection was performed in less than 10 min and can be executed simultaneously to HPLC analysis of the previous sample in a routine workflow, thus having minimal impact on the total sample analysis time when run in a sequence.

Equivalent Circuit Modeling for a Valveless Piezoelectric Pump

Various kinds of the models had been proposed to explain the relationship between the performance and the structural parameters of valveless piezoelectric pumps, so as to evaluate the functional performance such devices. Among the models, the equivalent circuit model, which converts the multi-field problem of a valveless piezoelectric pump system into a simple circuit problem, is the most simple and clear one. Therefore, the proposed structure and working principle of the valveless piezoelectric pump with multistage Y-shape treelike bifurcate tubes are analyzed; then, the equivalent circuit model of the valveless piezoelectric pump is established based on the working principles of this pump and liquid-electric analogy theory. Finally, an experimental study of the pump is carried out, with a comparative analysis of the experimental results and the simulation results of the generated equivalent circuit. The experimental results show that with a driving voltage of 100 V and frequency of 6 Hz, the maximum flow rate of the valveless piezoelectric pump is 1.16 mL/min. Meanwhile, the output current of equivalent circuit also reaches its peak at the frequency of 6 Hz, therefore, indicating a good predictive ability of this model in calculating the maximum output flow rate and best working frequency of valveless piezoelectric pumps.

Digitally-controlled driving power supply for dual-active-valve piezoelectric pump

The dual-active-valve piezoelectric pump (DAVPP) can achieve a precise and bidirectional delivery of liquid with flexibility through multiple control methods. Compared with the unidirectional piezoelectric pump, DAVPP has broader application prospects. For instance, for medical applications, DAVPP is promising to complete blood sample collection as well as drug injection in minute and accurate quantities, further to realize the integration between automatic diagnosis and disease treatment. The objective of this work is to keep DAVPP in operation with an innovative newly developed digitally-controlled driving power supply. First, a direct digital synthesis technology was adopted to generate two sine signals with an adjustable frequency and a phase difference. Then, a T-type resistor network was applied to regulate the voltage. Finally, high-voltage and power amplifying unit was utilized to achieve a sufficient driving ability. A prototype of the supply was made and its driving characteristics were tested in experiments. Experimental results demonstrate that the sine waveform output is satisfactory, the maximum voltage is up to 175 V, the frequency range is 5–500 Hz with a minimum resolution of 1 Hz, and the phase difference can be regulated from 0° to 360° with a minimum resolution of 11.25°, which perfectly matches the driving requirements of DAVPP. Control variables of DAVPP (namely driving voltage, frequency and phase difference) can be adjusted independently and continuously. By adjusting the driving phase difference, the direction of a liquid delivery can be changed, meanwhile, the output flow rate and output pressure can also be modulated smoothly.

Parametric study of a wave energy converter (Searaser) for Caspian Sea

Over the past decades, different types of energy converters have been invented because wave energy is a renewable energy source with high potential for extraction of considerable clean energy. Many numerical and experimental tests have been conducted to calculate the power generation of ocean waves, and these tests have demonstrated the significance of this energy. In this paper, the hydrodynamic performance of a new energy converter called "Searaser" has been evaluated using numerical simulation to study different aspects of this energy converter. Since previous studies have found ocean wave energy converters excellent for implementation in the Caspian Sea, the aim of this study is to investigate its performance for that sea, so this study presents a numerical simulation of Searaser inside an experimental wave tank using commercial software Flow-3D. To model the motion of the energy converter, Reynolds Averaged Navier-Stokes was coupled with a volume-of-fluid (VOF) model to generate three-dimensional numerical linear propagating waves for solving the fluid field. Grid independency was also carried out to determine the best mesh numbers for the original simulations. Finally, the Searaser hydrodynamic performance was numerically calculated for different wave heights, and some of the most important parameters of point absorbers were captured, including output flow rate in different seasons, extractable wave power, and output power. Accordingly, the obtained results indicate that the output flow rate and the power generation are significantly increased by incremental changes in wave height, and using this type of converter device has potential for practical and profitable use in industrial applications.

Slewing valve based on bypass pressure-compensation principle for dynamic control of large inertia load

Typical slewing valve is a three-position six-way proportional valve based on bypass throttle principle, whose output flow rate and opening dead zone of the main valve port are both affected by the load. Thus, it has poor performances in dynamic control of varying loads. This article presents a novel slewing valve based on bypass pressure-compensation principle, which has much better performance in dynamic control of varying loads and even for large inertia loads. A pressure-compensated valve is added to connect the out ports of the main valve port and the bypass port to keep the pressure differences at the main valve port and the bypass port in same. As a result, the flow distribution ratio of these two ports keeps stable for a certain spool position, which can avoid the output flow rate fluctuation despite the varying loads. In addition, the opening dead zone of the main valve port is very small and keeps almost unchanged. These advantages make the proposed valve to control large inertia load with great stability. In the article, a mathematical model formulating the dynamic performance of the valve is further established to provide guide for the optimization of the parameters, including the shapes and orifice areas of the main valve port and bypass port, the stiffness of the spring controlling spool motion, and so on. A prototype valve was manufactured based on the presented method. A series of tests on experiment bench and real crane validate its great performances on flow rate and dead zone stabilities as well as fast dynamic response.

Purification of textile wastewater by using coated Sr/S/N doped TiO2 nanolayers on glass orbs

Simultaneous doping of TiO2 nanoparticles with three elements including Sr, S, and N is reported. The resulting material shows superior photocatalytic performance toward degradation of textile waste under visible and sunlight. The pure and doped TiO2 nanolayers were prepared by sol-gel method and were fixed on a bed of glass orbs. The immobilized TiO2 were characterized by a variety of techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), spectroscopy diffusion reflection (DRS), energy dispersive X-ray spectrometry (EDS) and elemental analysis (CHNS). The photocatalytic activity of the prepared fixed-bed materials toward degradation of the textile wastes was determined by using ultraviolet-visible spectroscopy (UV-Vis) and measurement of the chemical oxygen demand testing (COD). The best photocatalytic activity was observed with the use of Sr/S/N-TiO2 nano-layers. Afterwards, the experimental conditions were optimized by tuning reaction parameters, including amount of doped metal ion on photocatalyst structure, sample solution pH and photoreactor output flow rate. The results confirmed that at natural pH 5.9 of sample solution, maximum decomposition of 91-99% of azo dyes was obtained in 8 h under visible irradiation. Finally, the experiments were repeated under 1.5 AM sunlight with high volume of reactants in order to confirm the cost-effectiveness of the designed photocatalyst.

Theoretical and Computational Analysis on Double-End Submerged Hollow Fibre Membrane Modules

This paper studies the potential increase in permeate output flow rate that submerged hollow fibres can achieve when operating in double-end suction. The flow dynamics of submerged hollow fibre membranes with different combinations of fibre inner diameter, membrane thickness, and membrane permeability were numerically simulated. Fibre features (fibre inner diameter, membrane thickness, and membrane permeability) are then characterised for their effects on the increment in permeate flow rate due to change in configuration. Concurrently, an analytical model of a fibre in double-end suction is modelled. Analysis on the double-end fibre model has indicated that the fibre characteristic ratio, λ, has a direct influence on the relative increase in output flow rate when both ends are open. Parametric investigations on the three fibre features have shown that their effects on relative output increase agree with the co-relations indicated by λ. For fibres with λ less than 4, a proportional relationship between a fibre’s λ value and the percentage increment in permeate flow rate is observed when adopting double-end suction. The fibre characteristic ratio, λ, in addition to characterising flux uniformity, can further be used to consider the effectiveness of applying double-end suction in Submerged Hollow Fibre Membrane Module (SHFMM) systems at the design stage.

Effects of Land Cover Changes to the Quantity of Water Supply and Hydrologic Cycle using Water Balance Models

The hydrologic cycle is a recurring consequence of different forms of movement of water and changes of its physical state on a given area of the earth. The land cover of a certain area is a significant factor affecting the watershed hydrology. This also affects the quantity of water supply within the watershed. This study assessed the impacts of the changing land cover of the Ipo watershed, a part of the Angat-Ipo-La Mesa water system which is the main source of Metro Manila’s water supply. The environmental impacts were assessed using the interaction of vegetation cover changes and the output flow rates in Ipo watershed. Using hydrologic modelling system, the hydrological balance using rainfall, vegetation and terrain data of the watershed was simulated. Over the years, there has been a decreasing land cover within the watershed caused mostly by deforestation and other human activities. This significant change in the land cover resulted to extreme increase in water discharge at all streams and rivers in the watershed and the water balance of the area were affected as saturation and shape of the land terrain changes.

Validation of Engine Performance for Tests on Ballast Water Heat Treatment Using Engine Waste Heat

Heat treatment has been considered as a suitable option for treatment of ballast water. Utilising the waste heat from the diesel engine fresh water and exhaust gases would be an economic option. For recovering the heat from the exhaust gases, heat exchangers are required to be placed in their flow path. The sea water coolant after recovering heat from fresh water has to be directed to this heat exchanger for sterilisation. For testing the effectiveness of these heat recoveries on species’ mortalities, a mini-scale system was arranged and tests were carried out. The engine output and other flow rates were maintained to achieve a temperature range of 55 to 80 o C. Data was obtained from the sensors and probes fitted at relevant points. The engine performance was monitored with computerised control equipment. Operational data from five test runs were analysed and verified by two approaches. In the first approach, the heat recovered by the water was compared with the heat lost by the exhaust gases and the maximum variation was observed to be 3.4%. In the second approach, the input energies were computed using two different methods using data values of brake power, thermal efficiency, mass flows, calorific value and specific fuel consumption. A maximum variation of -11% was seen for only one test run, while for other tests the variation was between -0.7% to -1.7%. The values obtained from the connected probes and the computed results were thus validated and further tests on species were carried out.

Thermal performance of a solar assisted horizontal ground heat exchanger

This paper presents an experimental study of a solar assisted horizontal ground heat exchanger system (HGHEs) operating as a daily heat storage unit. Initially, several soils were assessed as sensible heat storage mediums, with sand and gravel selected as the most appropriate. Then, a HGHEs was designed and connected to a 15 m2 test room with a heating load of 1 kW at Nottingham Trent University. Heating cables, simulating solar input, were used to heat the soil in the HGHEs to 70 °C, then a heat transfer fluid (HTF), was circulated through a closed loop heat exchanger to extract the stored heat. The parameters of soil backfill and HTF mass flow rate were investigated in the HGHEs. Several output flowrates ranging between 0.1 and 0.6 L/min were tested, producing discharge times varying between a few hours to a few days. The HTF mass flowrate was found to be the most significant parameter, affecting the HGHEs thermal capacity and heat exchange rates. The sand filled HGHE produced approximately 50% more hot water (T > 35 °C) during a longer duration achieving an efficiency of 78% compared to the gravel filled HGHE with a lower system efficiency of 58%. Insulating the HGHE system was found to reduce heat losses and avoid temperature fluctuations in the HGHEs. Overall, the results show the hot water quantity, temperature range and duration produced from the system were in line with low temperature district heating guidelines and can be applied to some household heating applications incorporating low flows and low temperatures.

Urine flow rate monitoring in hypovolemic multiple trauma patients

BackgroundThe urine output is an important clinical parameter of renal function and blood volume status, especially in critically ill multiple trauma patients. In the present study, the minute-to-minute urine flow rate and its variability were analyzed in hypotensive multiple trauma patients during the first 6 h of their ICU (intensive care unit) stay. These parameters have not been previously reported.MethodsThe study was retrospective and observational. Demographic and clinical data were extracted from the computerized Register Information Systems. A total of 59 patients were included in the study. The patients were divided into two study groups. Group 1 consisted of 29 multiple trauma patients whose systolic blood pressure was greater than 90 mmHg on admission to the ICU and who were consequently deemed to be hemodynamically compromised. Group 2 consisted of 30 patients whose systolic blood pressure was less than 90 mmHg on admission to the ICU and who were therefore regarded as hemodynamically uncompromised.ResultsThe urine output and urine flow rate variability during the first 6 h of the patients’ ICU stay was significantly lower in group 2 than in group 1 (p < 0.001 and 0.006 respectively). Statistical analysis by the Pearson method demonstrated a strong direct correlation between decreased urine flow rate variability and decreased urine output per hour (R = 0.17; P = 0.009), decreased mean arterial blood pressure (R = 0.24; p = 0.001), and increased heart rate (R = 0.205; p = 0.001).ConclusionThese findings suggest that minute-to-minute urine flow rate variability is a reliable incipient marker of hypovolemia and that it should therefore take its place among the parameters used to monitor the hemodynamic status of critically ill multiple trauma patients.

Application of Nanosize Zeolite Molecular Sieves for Medical Oxygen Concentration.

The development of a portable oxygen concentrator is of prime significance for patients with respiratory problems. This paper presents a portable concentrator prototype design using the pressure/vacuum swing adsorption (PVSA) cycle with a deep evacuation step (−0.82 barg) instead of desorption with purge flow to simplify the oxygen production process. The output of the oxygen concentrator is a ~90 vol % enriched oxygen stream in a continuous adsorption and desorption cycle (cycle time ~90 s). The size of the adsorption column is 3 cm in diameter and 20 cm in length. A Li+ exchanged 13X nanosize zeolite is used as the adsorbent to selectively adsorb nitrogen from air. A dynamic model of the pressure and vacuum swing adsorption units was developed to study the pressurization and depressurization process inside the microporous area of nanosized zeolites. The describing equations were solved using COMSOL Multiphysics Chemical Engineering module. The output flow rate and oxygen concentration results from the simulation model were compared with the experimental data. Velocity and concentration profiles were obtained to study the adsorption process and optimize the operational parameters.

Experimental investigation of the effect of grooves cut over the piston surface on the volumetric efficiency of a radial hydraulic piston pump

AbstractA radial piston pump often used in high pressure applications. The geometry of the pistons used affects the mechanical and volumetric efficiency of the pump and its long term performance. In the present study, the effect of grooves cut on the piston surface, the number of the grooves and their location over the piston surface on the volumetric efficiency of the hydraulic radial piston pumps was investigated. In order to perform the research tests, the three-piston fixed displacement pump with seven configurations was firstly designed and fabricated. The output flow rate of the pump was determined at pressure outlets of 350 and 500 bar and then the volumetric efficiency was calculated as the mean values of measured data. The results showed that the grooves cut on the piston surface produces a higher piston–cylinder overall leakage and then tend to reduce the volumetric efficiency. Also as the number of grooves being cut on piston surface increases, an increase in leakage will happen. In addition, b...

An analysis of thermodynamic properties in both traditional and enhanced geothermal systems to compare thermal efficiencies

This meta-study draws upon previous research on both Enhanced Geothermal Systems (EGS) and traditional geothermal systems (GS), using these findings to compare and investigate the thermal efficiency of each system. Efficiency calculations include reservoir enthalpy, maximum drilling well temperature, power output (per unit mass of liquid) and mass flow rate of these systems to determine whether EGS’s are viable as an alternative, more readily available renewable energy source. This meta-study suggests that EGS are more viable than naturally occurring GS in the context of future geothermal energy production as they perform with a similar average efficiency of 10-15% and, in addition, can be used in a wider range of geothermal environments.

Time‐ and State‐Dependent Input Delay‐Compensated Bang‐Bang Control of a Screw Extruder for 3D Printing

SummaryIn this paper, a delay‐compensated bang‐bang control design methodology for the control of the nozzle output flow rate of screw extruder‐based three‐dimensional printing processes is developed. A geometrical decomposition of the screw extruder in a partially and a fully filled regions allows to describe the material convection in the extruder chamber by a one‐dimensional hyperbolic partial differential equation (PDE) coupled with an ordinary differential equation. After solving the hyperbolic PDE by the method of characteristics, the coupled PDE–ordinary differential equation's system is transformed into a nonlinear state‐dependent input delay system. The aforementioned delay system is extended to the non‐isothermal case with the consideration of periodic fluctuations acting on the material's convection speed, which represent the process variabilities due to temperature changes in the extruder chamber, resulting to a nonlinear system with an input delay that simultaneously depends on the state and the time variable. Global exponential stability of the nonlinear delay‐free plant is established under a piecewise exponential feedback controller that is designed. By combining the nominal, piecewise exponential feedback controller with nonlinear predictor feedback, the compensation of the time‐dependent and state‐dependent input delay of the extruder model is achieved. Global asymptotic stability of the closed‐loop system under the bang‐bang predictor feedback control law is established when certain conditions related to the extruder design and the material properties, as well as to the magnitude and frequency of the materials transport speed variations, are satisfied. Simulations results are presented to illustrate the effectiveness of the proposed control design. Copyright © 2017 John Wiley &amp; Sons, Ltd.

A bio-inspired 3D-printed hybrid finger with integrated ECF (electro-conjugate fluid) micropumps

The paper proposes a novel 3D-printed hybrid finger embedding ECF (electro-conjugate fluid) micropumps inspired from the hydraulic mechanism of spider legs. Two integrated ECF micropumps control two bellows-like joints respectively through fluidic channels built in the finger to realize the compliant motion with 2 DOFs (degree-of-freedom). Instead of the traditional CNC machining, molding and multiple manual assembly, the 3D printing technology of hybrid-material (hard and soft material) is utilized to fabricate our hybrid finger, which consists of (a) one monolithic body with the combination of a finger body base covered with rubber sheets and two bellows-like joints, (b) three finger body covers combined with rubber sheets, solving the annoying problems related to the complicated machining, the elaborate molding, and the delicate assembly and interfacing of soft and hard components. The ECF micropump with TPSEs (triangular prism & slit electrode pairs) was designed and fabricated by the MEMS process based on the micro-molding with thick photoresist and nickel electroplating. Characteristics experiments including output pressure and output flow rate measurement demonstrated that the fabricated ECF micropump had high output power density. The hybrid finger with ECF micropumps was successfully realized and its driving experiments validated the feasibility of our concept.

Computational Studies for the Design Parameters of Hollow Fibre Membrane Modules

In this paper, several design features of Hollow Fibre Membrane Modules have been studied using Computational Fluid Dynamics (CFD). The features studied included the combined effects of packing density, fibre length, fibre inner diameter, as well as the potting thickness, so as to analyse the corresponding changes to the local flux distribution and permeate output flowrate. Under different feed pressures, simulation results showed that the decrease in feed pressure along the membrane fibre was greatly affected by both the fibre length and packing density. In general, fibres packed at 0.5 packing density (i.e. 50% of the total space within the module is occupied by hollow fibres) had the highest permeate flow rate, and the optimum packing densities of longer fibres (Length≥1m) were lesser than those of shorter fibres. The increase in inner diameter led to a proportional reduction in the permeate pressure, while improving the overall Transmembrane Pressure (TMP) and permeate flowrate. The inner diameter required for optimum output flowrate was dependent on the length of fibre used, in which longer fibres used required a larger inner diameter to ensure optimum output flowrate. Finally, reduction in permeate flowrate caused by potting thickness was found to be proportional to the permeate flowrate at the outlet of the hollow fibre.

Design of microfluidic channel networks with specified output flow rates using the CFD-based optimization method

We report an effective, easy-to-use, computational fluid dynamics-based optimization method for designing purely resistive microfluidic networks with desired flow rates at user-specified outlets. The detailed topology and shape of the microchannel networks are obtained by minimizing the fluidic resistance of channels under a fixed driving flow rate at the inlet. This proposed method allows flexibility in setting up the relative positions among the inlet and outlets so that the layout of channel networks can be compactly adjusted based on the specific design requirements.