Outlet End Research Articles

The Complete Performance Map of Gas Wave Ejector and Analysis on the Variation Laws and Limitation of Performance

Abstract The gas wave ejector (GWE) is an efficient gas wave equipment using pressure waves to realize energy exchange. In this paper, a theoretical analysis of the limitation of application range and the factors affecting the performance of GWE was carried out by numerical simulation. And a complete experimental system including an adjustable GWE was employed to obtain the specific performance values in various working conditions. Such theoretical analysis showed that the device became inapplicable with a relatively high driving pressure ratio, resulting from the generation of supersonic flow at the outlet end of the passages. A relatively high supercharging ratio also limited the equipment application because of the weakening of the reflected expansion waves and the enhancement of the reversed compression wave. Furthermore, the mixing, vortex, viscosity, and other flow losses could also affect the equipment performance. Then, a complete performance map indicating the specific performance values in the application range was obtained by plenty of experiments. The performance map proved that GWE had excellent efficiency and broad applicability especially as the driving pressure ratio was lower than 2.6. The results are significant for practical application and performance improvement of GWE.

MEMS-Based Microfluidic Fuel Cell for In Situ Analysis of the Cell Performance on The Electrode Surface

The present study investigates various effects of MEMS-based microfluidic fuel cell on the performance of direct formic acid microfluidic fuel cells that breathe air as an oxidant. A miniaturized fuel cell of the structure and design of a typical T-shaped air- breathing Direct Formic Acid Fuel Cell with micro channel is 1.5 mm x 25 mm in width multiply length. Both anode and cathode electrode having a width and length of 0.6 mm and 20 mm, respectively, with an electrode spacing of 0.3 mm. An air-breathing microfluidic fuel cell having a 0.6 mm in width and 20 mm in length that is placed on cathode GDE down-side. In such systems for the fluid delivery, both formic acid (0.5 M) as a fuel solution mixing sulfuric acid (0.5 M) at a node channel side and as an electrolyte used sulfuric acid (0.5 M) place take on the cathode channel side are injected together into the end of the channel outlet by two syringe pumps. Firstly, a three-dimensional microfluidic fuel cell model was established using Computational Fluids Dynamics to simulate the fuel cell performance. Further, both V-I curves obtained from simulation and published experimental data under similar operating condition were compared to assure the validity of the simulation. Modelling the transport and electrochemical phenomena were described with hydrodynamic equations, the porous media flow, mass transport, electrochemical reaction and charge equation. The porous media flow in the gas diffusion layer was described by Brinkman equation. The Butler-Volmer equations were applied to get the V-I-P curves. An anode electrode surface performance, respectively, is presented.

Acoustic impedance of microperforated plates with stepwise apertures

Microperforated plates (MPPs) are efficient sound absorbers typically made of thin panels, which restricts practical application in engineering. This paper investigates MPPs with stepwise apertures on thick panels to enhance acoustic performance and overcome the lack of appropriate strength. Thermoviscous acoustic simulations of the MPPs demonstrate that the acoustic pressure, local velocity, and the power dissipation change abruptly at the step edges, similar as the behaviors at the inlet and outlet ends of the uniform perforations. The step generates additional acoustic impedance, which has a strong relationship with cross section ratio. Empirical impedance correction models for sharp-edged circular holes located concentrically on square or circular end panel are derived based on numerical simulations. Experimental data validate that the proposed models offer accurate prediction for acoustic impedance of MPPs with stepwise apertures.

Use of CFD to Investigate Flow Characteristics and Oil Distribution Inside an Oil-injected Screw Compressor

The well-developed CAE tools are used to investigate flow characteristics and oil distribution inside an oil-injected screw compressor. The flow field of gas mixed with oil is calculated by ANSYS CFX. TwinMesh generates high quality hexahedral grids for the compression chambers. There are two cases studied in this study. In the first case, the compressor models under four loading conditions are analyzed. The pressure curve is used to see if the designed built-in volume index is appropriate. In the second case, the compressor models under oil-free and oil-injected conditions are analyzed. The pressure gradients on rotor surfaces and velocity vector fields are used to describe the effects of lubrication and sealing in the sealing line gap, the tip gap, and the outlet end gap of rotors. The designer could optimize the slider and know if the oil is properly distributed in each gap.

Phase-field modeling of an immiscible liquid-liquid displacement in a capillary.

We develop a numerical model for a two-phase flow of a pair of immiscible liquids within a capillary tube. We assume that a capillary is initially saturated with one liquid and the other liquid is injected via one of the capillary's ends. The governing equations are solved in the velocity-pressure formulation, so the pressure levels are imposed at the capillary inlet and outlet ends. We model the structure of the flow and the shape of the interface. We are able to reproduce the flow for a wide range of capillary numbers, when the meniscus preserves its shape moving together with the flow, and when the meniscus constantly stretches resembling the transport of a passive impurity. We demonstrate that the phase-field approach is capable of reproducing all features of the liquid-liquid displacement, including the motion of a contact line, the dynamic changes of the capillary pressure, and the dynamic changes of the apparent contact angle.

Method Validation for Determination of Metformin Hydrochloride in Pharmaceutical Formulations by Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection

A method for the determination of metformin hydrochloride (MH) in pharmaceutical formulations by capillary electrophoresis with capacitively coupled contactless conductivity (C4D) detection was investigated. The separation was achieved under normal polarity mode at 17.5°C, 30 kV, hydrodynamic injection (50 mbar for 8 s) and using a bare fused silica capillary 72 cm × 75 µm i.d. (detection length, 10.5 cm from the outlet end of the capillary). The optimized background electrolyte consisted of 10 mM 2-morpholinoethanesulfonic acid and 10 mM histidine, pH 6.8. C4D parameters were set at fixed amplitude of 100 V and frequency of 650 kHz. Under the optimum conditions, the method shows good linearity over the range of 10-30 µg mL-1 MH (r2=0.9971). Limits of detection and quantitation based on S/N ratio of 3 and 10 were 0.049 and 0.15 µg mL-1, respectively. The proposed method was successfully applied to the assay of MH in pharmaceutical formulations and establishing the dissolution profiles for both immediate and extended release formulations of MH.

The Effect of Brine Supply on CO2 Injectivity Impairment Due to Salt Precipitation

Salt clogging has been recognized as an important factor for injectivity impairment in the CO2 injection wells. While only a small amount of field experience with salt clogging has been reported to date, a large number of experimental and numerical studies have been published on the topics of injectivity impairment, drying mechanisms in porous media and salt precipitation due to CO2 or gas injection. The motivation for our work was to provide a better insight into which combinations of petrophysical properties and operational parameters would enable long term CO2 injection with minimal injectivity impairment caused by salt precipitation. Two supercritical CO2 injection experiments into brine-saturated Berea sandstone cores were performed in a core flooding setup at reservoir conditions. Salt concentration was moderate, at around 10 wt%. X-ray computed tomography scanning of the cores was performed prior to and after the flooding experiments. We focused on recreating conditions in the near-well region where CO2 injection rate is high, and brine back-flow rate is low, and thus evaporative regime is expected. The novelty in our experimental approach was that we introduced a continuous brine supply through a thin borehole in the outlet end of the core. This mimics a situation where the dry-out zone close to the injection well is (partially) replenished by brine from the surrounding reservoir. Complete salt clogging occurred in both experiments. The main difference between the two experiments was that CO2 injection rate was higher in the second experiment. In the first experiment, CT-imaging shows that salt precipitated in sheets with a helical structure mostly in the lower half of the core. In the second experiment, the salt accumulation was displaced further towards the core outlet and concentrated around the brine injection borehole. The average permeability across the core samples decreased substantially in both cases: by 99 % in the first experiment and by 96 % in the second. Our results confirm that salt clogging is a complex process where different parameters, such as salinity, CO2 and brine injection rates, permeability, pressure and temperature, can have significant effect on whether injectivity impairment occurs.

Design and Analysis of an Operative Inlet

This paper describes the effect of intake manifold with the application of intake runner as the operative inlet used in racing car that participate in Formula Student (FSAE) competition. The design analysis of the runner is carried out to give uniform distribution of the air flow getting into engine. Air flow behavior plays an important role in order to provide better air fuel mixture inside the intake manifold before it is drawn to the combustion chamber. The results from this study indicate that longer runner gives low percentage of pressure loss but cause the air velocity to drop. Changing the outlet diameter of runner gives higher velocity at the smaller diameter and highest angle resulted higher air mass flow rate inside the runner. The new design of runner is built of 60mm length, 55mm outlet diameter and 55° angle and the results show 0.05% improvement occur in air flow distribution at the end of each runner outlet.

Coating Distribution in a Commercial SCR Filter

A commercial SCR filter, deployed in the USA in 2015, was sectioned and examined using techniques including mercury porosimetry, electron microscopy, and micro-X-ray computed tomography. The catalyst washcoat was found to be consistent with Cu/SSZ-13, possibly including some zirconia and alumina. Three distinct regions were observed with respect to catalyst loading and location. A region at the inlet end of the filter, comprising 15 to 21% of the total effective filter length, was relatively lightly coated. Most of the catalyst present in this region was observed inside the porous filter walls, and the catalyst concentration was generally greater near the upstream filter wall surfaces. Moving axially down the monolith toward the outlet, a second region comprising 14 to 20% of the total effective filter length was more heavily coated, with catalyst present throughout the thickness of the porous filter walls, as well as coatings on both the upstream and downstream filter wall surfaces. The final region at the outlet end of the monolith, which accounted for 65 to 70% of the filter length, had an intermediate catalyst loading. Most of the catalyst here was again observed inside the porous filter wall. Concentrations in this region were higher near the downstream filter wall surfaces. Detailed models of multi-functional aftertreatment devices, such as the one examined here, have included representations of catalyst distribution within the filter bricks and indicate that catalyst distribution may have an impact on flow distribution, soot loading patterns, local concentrations, and ultimately conversion efficiency. Previous work has also shown that catalyst distribution across the thickness of an exhaust filter wall can have significant impacts on backpressure during soot loading.

Non-invasive image processing method to map the spatiotemporal evolution of solute concentration in two-dimensional porous media

A color visualization-based image processing method is developed in this paper to quantify the concentration evolution of the Brilliant Blue FCF transport through a two-dimensional homogeneous porous medium. A series of images are recorded at known time intervals, then the spatial distribution is estimated using a calibration curve, linking the gray pixel value to the solute concentration. Using a multi-dimensional concentration distribution map extraction technique the longitudinal and transverse concentration distributions could be observed with the physical model. The image-processed concentrations are then compared directly with the measured concentrations sampled at the outlet end. The tracer breakthrough curves sampled at multiple points along the central line of the medium are also compared with the solutions from the standard advection–dispersion equation model. It is shown that the non-invasive image processing method may be used to map the spatiotemporal evolution of a solute’s concentration without disturbing the flow or the transport dynamics, although the measured solute breakthrough curves feature some non-Fickian dynamics that cannot be efficiently captured by the standard transport model.

A Portable Device Integrated with Aligned Carbon Nanotubes for Sensitive Virus Capture and Detection.

Point-of-care virus diagnosis is highly desirable in worldwide infectious disease control. Here we report a hand-held device for capturing viruses by applying physical size based exclusion inside a point-of-care device integrated with vertically aligned carbon nanotube (VACNT) nanostructures to achieve label-free and high throughput virus capture. The microfluidic device is constructed from a VACNT channel wall synthesized bottom-up via chemical vapor deposition (CVD). The VACNT has ~117 nm average gap size and ~97& porosity. By bonding with a polydimethylsiloxane (PDMS) cover sealing the top, the aqueous sample containing virus particles filter through the VACNT channel wall under negative pressure applied at the outlet end. We have demonstrated that the device is capable of filtering 50 μL of PBS containing ~6.3 × 104 counts of lentivirus particles in 10 minutes with 97& of capture efficiency, quantified by the cell infectious titration technique.

Dynamic variation of arc discharge and its effect on corrosion direction under current-carrying sliding

Current-carrying sliding tests were performed on an HST-100 high-speed multifunction friction and wear tester. Cf/Cu/C composite was used as the pin, and commercial QCr0.5 was employed as the disk. Sliding tests were carried out at a speed of 30 m/s and a load of 70 N under 25 A, 50 A, 75 A, and 100 A, respectively. Light intensity was collected by a photodiode, and the arc discharge process was recorded by a high-speed camera (HX-5) with a capture rate of 20,000 fp/s. The worn surfaces were characterized by a Nova NanoSEM230 scanning electron microscope and a NANO Focus AG three-dimensional topography instrument. The result indicates that arc discharge occurs randomly, both temporally and spatially, as long as the condition is suitable and occurs more at the beginning and end of the friction process. The arc moves constantly along the friction direction to the outlet. Compared to the inlet, the erosion of the outlet is considerably worse. This finding indicates the arc is moving towards the outlet and grows by a large margin when it leaves the friction surface at the outlet end.

Determination of Biogenic Amines in Seawater Using Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection.

A rapid and green analytical method based on capillary electrophoresis with capacitively coupled contactless conductivity detection (C4D) for the determination of eight environmental pollutants, the biogenic amines (putrescine, cadaverine, spermidine, spermine, tyramine, 2-phenylamine, histamine and tryptamine), is described. The separation was achieved under normal polarity mode at 24 °C and 25 kV with a hydrodynamic injection (50 mbar for 5 s) and using a bare fused-silica capillary (95 cm length × 50 µm i.d.) (detection length of 10.5 cm from the outlet end of the capillary). The optimized background electrolyte consisted of 400 mM malic acid. C4D parameters were set at a fixed amplitude (50 V) and frequency (600 kHz). Under the optimum conditions, the method exhibited good linearity over the range of 1.0–100 µg mL−1 (R2 ≥ 0.981). The limits of detection based on signal to noise (S/N) ratios of 3 and 10 were ≤0.029 µg mL−1. The method was used for the determination of seawater samples that were spiked with biogenic amines. Good recoveries (77–93%) were found.

Nitrous oxide in waste anesthetic gases with different fresh gas flow: a case-based pilot observation and a practical thought on scavenging.

Use of nitrous oxide (N2O) as an anaesthetic gas has been on contradicting views for various reasons; operating room (OR) pollution and occupational exposure is one of those controversies. The present pilot experiment was planned to analyze the anaesthesia gas waste at the machine end of scavenging outlet and calculate the probable portion of N2O in the OR air, which is likely to help us in informed decision making. Anaesthesia gas waste was sampled at the machine end of scavenging outlet and was connected directly and analyzed using a gas analyzer attached to Mindray A7 anaesthesia workstation. An assembly of L connector, sampling line, corrugated tube and endotracheal tube were used to perform the procedure. The measurements were taken at 600, 1200 and 1800 mL/minutes of fresh gas flow (FGF). A total of 15 paired readings from five general anaesthesia cases were taken. The N2O percentage in the anaesthesia waste gases with a FGF of 600, 1200 and 1800 mL was 3.4 ± 0.54, 8.2 ± 0.83 and 14.0 ± 0.70, respectively. On calculation, the likely concentration of N2O in OR with FGF of 600 mL/min is 0.576 ppm, which will lead to the time weighted average 4.6 ppm exposure per day in modular OR. Reducing FGF to 600 mL/min reduces the N2O concentration in OR by 75% as compared to the FGF of 1800 mL/min. The time weighted average exposure to N2O is far below the permissible limit in modular OR.

Direct methanol fuel cell bubble removal mechanism using magnetic actuation

ABSTRACTThis article develops a direct methanol fuel cell (DMFC) with a magnet-actuated bubble removal mechanism. A micro-DC motor is used to control the bubble removal mechanism. The lower magnetic device is operated to extrude a Polydimethylsiloxane (PDMS) runner to compress the liquid fuel in the anode flow channel, forcing the CO2 bubbles in the runner to flow toward the outlet end. The bubble retention in the anode flow channel is thereby improved, enhancing the cell performance. The proposed mechanism stability and performance and Polymethylmethacrylate (PMMA) runner are also discussed.

Investigation into aerodynamic and heat transfer of annular channel with inner and outer surface of the shape truncated cone and swirling fluid flow

We have carried out Investigation into aerodynamic and convective heat transfer of the annular channel. Inner or outer surface of annular channel has shape of blunt-nosed cone tapering to outlet end. Truncated cone connects to a cyclone swirling flow generator. Asymmetric and unsteady flow from the swirling generator in the shape of periodic process gives rise to the formation of secondary flows of the type Taylor-Görtler vortices. These vortices occupy the whole space of the annular channel, with the axes, which coincide with the motion direction of the major stream. Contraction of cross-sectional area of channel (in both cases 52%) causes a marked increase in total velocity of flow, primarily due to its axial component and promotes a more intensive vortex generation. Vortex structures have a significant influence on both average heat transfer and surface distribution. At cross-sections of the annular channel we observe similarity of curves describing distribution of total velocity about wall and heat flux density on the surface. The coordinates of maximum and minimum values of velocity and heat flux coincide. At the average cross-section channel of maximum value of heat transfer is greater than minimum of about by a factor of 2.7 times for outer heat transfer surface and about by a factor of 1.7 times for inner heat transfer surface. Taper channel has a much higher influence on heat transfer of the inner surface than the outer surface and manifests itself at lower values of dimensionless axial coordinate. For the investigated taper cone geometry of the annular channel the heat transfer coefficient of inner surface increases at the outlet section and exceeds value in comparison with straight-line section by 91 … 98%. Heat transfer of the outer cylinder in the same section increases only by 5 … 11%. The increase in average heat transfer over the surfaces is 36% and 4% respectively.

Development of a dynamic simulation model of a hollow fiber membrane module to sequester CO2 from coalbed methane

A dynamic simulation model of a hollow fiber membrane module has been developed by deriving new transient mole fraction balances, energy balances, and gas velocity equations based on mole balances. The adopted flow type of the membrane module is a counter-current flow for the recovery of methane from coalbed methane (CBM), which is a form of natural gas extracted from coalbeds and is composed of mainly methane (up to 80–99vol%) and minor impurities (CO2, N2, etc.). This study assumes that the CBM feed gas for the dynamic simulation consists of 90% methane and 10% carbon dioxide. In the simulation model, CBM feed gas is supplied into the bore side feed, and purified methane rich gas, the retentate gas, is produced from the product side of the bores. Carbon dioxide rich gas, the permeate gas, is discharged from the outlet end of the shell side. The simulation results are very similar to the experimental data of Airrane Co., Ltd. in Korea. This paper presents the effects of design and operating conditions on the performance, and investigates the transient behaviors of membrane modules using the validated simulation model.

Capturing Excess Nutrients from Waterways

Capturing Excess Nutrients from Waterways

Research on Feasibility of Large-scale New Energy Islanding Detection Scheme Based on Impedance Measurement

A lot of research has been done on islanding detection of photovoltaic(PV) power system. In these schemes, islanding can be detected by schemes based on convertor control. The range of these research is islanding occurs in a single power station or distributed generation system. However, experiments proof that islanding also occurs in large-scale wind farms. Classical islanding detection schemes such as active frequency drift scheme or reactive power disturbance scheme may not suitable to this situation due to the different parameter when islanding occurs in large-scale new energy power stations. Meanwhile, islanding detection scheme based on system impedance detecion is an ideal scheme to detect islanding in large-scale new energy power stations. However, reaearch on islanding detection scheme based on system impedance only compute the impedance of the outlet end of the convertor, in other words, in a single power station and overlook the problems when the scheme is applied to large-scale new energy power stations, such as power quality problem and signal attenuation problem and so on. This artical will analyze the feasibility of using system impedance to detect islanding in large-scale new energy power stations.

Fast and Accurate Prediction of Stratified Steel Temperature During Holding Period of Ladle

Thermal stratification of liquid steel in a ladle during the holding period and the teeming operation has a direct bearing on the superheat available at the caster and hence on the caster set points such as casting speed and cooling rates. The changes in the caster set points are typically carried out based on temperature measurements at the end of tundish outlet. Thermal prediction models provide advance knowledge of the influence of process and design parameters on the steel temperature at various stages. Therefore, they can be used in making accurate decisions about the caster set points in real time. However, this requires both fast and accurate thermal prediction models. In this work, we develop a surrogate model for the prediction of thermal stratification using data extracted from a set of computational fluid dynamics (CFD) simulations, pre-determined using design of experiments technique. Regression method is used for training the predictor. The model predicts the stratified temperature profile instantaneously, for a given set of process parameters such as initial steel temperature, refractory heat content, slag thickness, and holding time. More than 96 pct of the predicted values are within an error range of ±5 K (±5 °C), when compared against corresponding CFD results. Considering its accuracy and computational efficiency, the model can be extended for thermal control of casting operations. This work also sets a benchmark for developing similar thermal models for downstream processes such as tundish and caster.