Increase In Flow Ratio Research Articles

Visualization experiment of solid-liquid two-phase flow transportation in a jet pump

Abstract Due to its lack of internal moving components, the jet pump offers widespread application possibilities in solid-liquid two-phase flow transportation. Utilizing high-speed photography, this research established a visual experimental platform for jet pumps, allowing for a detailed study and analysis of the dynamics of solid particles entering, mixing, and being conveyed through the jet pump. The following results were obtained. The introduction of solid phase particles into the jet pump results in decreased pressure ratio and efficiency, yet the general trajectory of change within the pump system remains constant. With decreasing particle size, particles become increasingly susceptible to being entrained and propelled into the jet pump by the high-velocity jet flow. The proportion of particle distribution in the mixing chamber rises as the flow ratio goes up. However, when the flow ratio falls below 0.6, the changes in particle distribution beneath the jet zone of the mixing chamber become insignificant, primarily due to the impact of particle deposition within the suction chamber. A reflux zone is observed in the throat, which gradually shrinks in length as the flow ratio increases.

Experimental study on heat storage characteristics of an air-sand moving bed heat exchanger

The air-sand moving bed heat exchanger, designed for storing fluctuating medium-temperature gas waste heat, offers significant potential for energy conservation and carbon reduction in industrial settings. However, its operational characteristics are insufficiently explored. This study investigates the heat storage process involving direct contact and cross-flow of air and quartz sand within a rectangular heat exchanger chamber. Comprehensive analyses were conducted to explore flow resistance characteristics, temperature response, and heat storage performance. Results indicate that pressure drop increases with higher air velocity and temperature, and lower air pressure, particle diameter. The relative discrepancy between fitted pressure drops and experimental data is below 10%. The primary heat transfer zone exists during particle descent. As the air-particle mass flow ratio increases, the descent rate of this zone along the airflow direction slows. Additionally, higher air temperatures elevate the optimal air-particle mass flow ratio. With inlet temperatures for air and particles set at 350 °C and 30 °C respectively, and a mass flow ratio of 0.81, an exergy efficiency of 58.93% and a power density of 600.64 kW·m−3 are achieved. These findings offer crucial insights for air-sand moving bed heat exchangers for medium-temperature gas waste heat recovery.

Effect of pulsating flow on flow-induced vibrations of circular and square cylinders in the laminar regime

Through fluid-structure interaction simulations, this study assesses the dynamic response characteristics of elastically mounted circular and square cylinders subjected to pulsating inflow conditions, providing valuable insights into the analysis and optimization of these systems. The main focus of the present work is on analyzing the effects of two factors: (i) the ratio of the oscillatory velocity component to the steady velocity component in pulsating flow (flow ratio) and (ii) the ratio of the oscillation frequency of pulsating flow to the natural frequency of the structure (frequency ratio). The simulation results for different parameters of interest are analysed using Fourier analysis and Poincaré maps of time series data, and contour plots of vorticity. For the circular cylinder, it is found that cylinder loses synchronization in lock-in as the flow and frequency ratios are increased. Three distinct vibration patterns of vortex-induced vibration are observed for selected combinations of flow and frequency ratios at a Reynolds number of 110 for circular cylinder. For the galloping of square cylinder at a Reynolds number of 250, it is found that the instability and nonlinearity of vortex shedding become more pronounced as the flow ratio increases.

Impact of Radial Wall Strain on Serial Changes in Vascular Physiology in Patients with Intermediate Coronary Stenosis.

Coronary biomechanical stress contributes to the plaque rupture and subsequent events. This study aimed to investigate the impact of plaque biomechanical stability on the physiological progression of intermediate lesions, as assessed by the radial wall strain (RWS) derived from coronary angiography. Patients with at least one medically treated intermediate lesion at baseline who underwent follow-up coronary angiography over 6 months were included. The maximal RWS ( ) of the interrogated lesion was calculated from the baseline angiogram. The primary endpoint was to determine the association between baseline and the functional progression of coronary lesions, defined as an increase in the lesion-specific quantitative flow ratio (L- QFR, calculated as the absolute change in QFR across the lesion) on serial angiograms. Among 175 lesions in 156 patients, 63 lesions showed an increase in L- QFR during a median follow-up period of 12.4 months. Baseline values were significantly higher in lesions with increased L- QFR than in those with stabilized or decreased L- QFR (11.8 [10.7, 13.7] vs.10.8 [9.7, 11.7]; p 0.001). Baseline presented an area under the curve of 0.658 (95% confidence interval [CI]: 0.572-0.743, p 0.001) for the prediction of increased L- QFR. After full adjustment for clinical and angiographic factors, a high ( 12) was found to be an independent predictor of functional lesion progression (odds ratio: 2.871, 95% CI: 1.343-6.138, p = 0.007). A high calculated from baseline angiograms was independently associated with the subsequent physiological progression in patients with intermediate coronary lesions.

Investigation on the showerhead film cooling of the turbine vane considering combustor swirling outflow

The mutual interference between the combustor and turbine of modern aero-engines has gradually increased with recent advancements, and turbine cooling design considering the flow characteristics at the combustor exit has not been investigated thoroughly. More importantly, no effective solution has been proposed for the negative impact of swirling inflow on vane cooling. This paper presents a comprehensive study on vane leading edge cooling, where the region is most susceptible to the swirling inflow. The film cooling effectiveness (η) of the showerhead film cooling is measured by PSP (pressure-sensitive-paint) technology, and flow characteristics are obtained by numerical simulation. Based on the in-depth analysis, a new film hole layout is proposed to suppress the negative impact of the swirl intake condition on film cooling. The results show that the swirling inflow changes the vane pressure distribution, leading to a significant radial deflection of the film. This causes the film to concentrate in the partial area of the vane, thereby increasing the film distribution inhomogeneity. The mass flow ratio increase only restrains the negative influence of swirling inflow on the cooling effect to a certain extent under the high swirl intensity intake condition (SN = 0.45). At SN = 0.45, an efficient showerhead cooling scheme is desired, and we propose a new cooling scheme to this end. According to the pressure distribution on the leading edge, the new film hole layout scheme can exhibit excellent inhibitory effect on the radial deflection of the film. Therefore, the new cooling scheme can increase the film coverage area and improve the uniformity of film distribution. The increase in surface-averaged film cooling effectiveness (ηsur-ave) is up to 23.1%. Furthermore, the new cooling scheme reduces the relative standard deviation of film cooling effectiveness by up to 24.1%. Thus, the proposed scheme highlights the influence of the combustor outflow on the showerhead film cooling, which can provide a reference for vane cooling design.

Research on Two-stage Humidification-dehumidification Heat Pump Desalination System

For the humidification-dehumidification desalination unit to perform more efficiently, a two-stage humidification-dehumidification heat pump desalination system was proposed. So as to improve the heat and mass transfer effect between seawater and moist air, the two-stage humidifier was employed to recover the waste heat of seawater discharged from the first stage humidifier. The models of a one-stage and two-stage humidification heat pump seawater desalination system were built using Aspen Plus simulation software. Multi-condition simulation studies were carried out for different inlet seawater temperatures, liquid-gas mass ratios, and refrigerant flow rates of the heat pump. According to the comparative examination of the simulation’s outcomes, it is concluded that: with the increase in inlet seawater temperature and liquid-gas flow ratio, the two-stage humidifier system’s recovery rate and gain output ratio are superior to those of the first-stage humidifier system, and the inlet seawater temperature and circulating airflow needed for the two-stage humidifier system to perform at its best are less demanding than those for the first-stage humidifier system., indicating that the two-stage humidifier dehumidification desalination technology of the heat pump has great performance improvement and a broad application prospect.

Synthesis of CuO thin films by a direct current reactive sputtering process for CO gas sensing application

A direct current magnetron reactive sputtering, one of the well-known physical vapour deposition (PVD) techniques, was employed for the preparation of CuO thin films at room temperature for CO gas sensing application. The effect of the O2 gas flow ratio on the phase formation of copper oxide was studied by varying the O2 flow rate in the total flow of Ar/O2 gas mixture. Cu2O phase was found to form at a low O2 flow ratio of 10% and gradually converted into stable CuO phase with an increase in O2 flow ratio through the intermediate phase of Cu4O3. The films exhibited a granular morphology, and the average grain size increased with an increase in the O2 partial flow. Single-phase CuO thin film has been obtained with 40% of O2 gas flow ratio. The evolution of the copper oxide phases with increasing O2 partial flow was also confirmed using the Cu 2p and O 1s core-levels of X-ray photoelectron spectroscopy. The CO gas sensing characteristics of the CuO thin film were examined by varying the operating temperature in the range of 200 °C–400 °C. An optimized CO sensing response of 127% has been obtained at 375 °C towards 91 ppm concentration with a response/recovery time of 161 s/99 s.

Size, Morphology and Crystallinity Control Strategy of Ultrafine HMX by Microfluidic Platform.

The crystal structure has a great influence on mechanical sensitivity and detonation performance of energetic materials. An efficient microfluidic platform was applied for size, morphology, and crystallinity controllable preparation of ultrafine HMX. The microfluidic platform has good mixing performance, quick response, and less reagent consumption. The ultrafine γ-HMX was first prepared at room temperature by microfluidic strategy, and the crystal type can be controlled accurately by adjusting the process parameters. With the increase in flow ratio, the particle size decreases gradually, and the crystal type changed from β-HMX to γ-HMX. Thermal behavior of ultrafine HMX shows that γ→δ is easier than β→δ, and the phase stability of HMX is β > γ > δ. Furthermore, the ultrafine β-HMX has higher thermal stability and energy release efficiency than that of raw HMX. The ultrafine HMX prepared by microfluidic not only has uniform morphology and narrow particle size distribution, but also exhibits high density and low sensitivity. This study provides a safe, facile, and efficient way of controlling particle size, morphology, and crystallinity of ultrafine HMX.

Modulation of the conductive behavior of NiO thin film deposited by HiPIMS through varying the O2 flow ratio

Nickel oxide (NiO) films were prepared through High Power Impulse Magnetron Sputtering (HiPIMS). The influence of O2/(Ar + O2) flow ratio (oxygen flow ratio) from 0.5% to 3% on structural and optoelectronic qualities of NiO films were studied. The results indicate that deposition rate of NiO film reduces as increase of oxygen flow ratio. Atomic force microscopy shows that as oxygen flow ratio increases, surface roughness of NiO films decrease. The transmittances of the NiO films are over 60% in the visible wavelengths. Hall effect measurements suggested that by adjusting the oxygen flow ratio NiO films with different type of conduction can be obtained. The carrier concentration of NiO films increase significantly as oxygen flow ratio goes up, which is caused by the fact that more nickel vacancies and interstitial oxygen are formed in NiO films. Therefore, the electrical conductivity enhances accordingly. The XPS analysis demonstrates the presence of both Ni2+ and Ni3+ oxidation states and also confirms the transition of conductive type of the NiO films. HiPIMS is a potential approach for depositing n type or p type transparent conductive oxide NiO films.

Low-frequency shock train oscillation control in a constant area duct

The self-excited shock train oscillation control using partial removal of boundary layer flow in a constant area duct is studied numerically using unsteady Reynolds Averaged Navier–Stokes simulation. The effect of varying the suction flow ratio on the shock train oscillatory characteristics is analyzed using steady and unsteady statistics, space–time contour, power spectra, and cross correlation analysis. For the present study, a constant area duct of height 0.032 mm, and the aspect ratio of 25, at freestream Mach number of 2.0 and back pressure ratio of 0.52 is considered. The removal of the boundary layer through an angled suction slot with three different suction flow ratios is performed. Numerical results indicate that the removal boundary layer restricts the bifurcation process of the shock train and appears to be a single curved normal shock at a higher suction flow ratio. Also, the transition of regular reflection to the Mach reflection type is noted. The suction flow from the top and bottom slot tends to initiate a lateral oscillation that forms a wavy mixing flow region. The power spectral density contour suggests that the increase in suction flow ratio will tend to increase the dominant frequency ranges from (0.034 to 0.094). The cross correlation indicates the presence of downstream pressure disturbance that moves toward the upstream direction. With suction flow, a disturbance that emerges from the suction slot moves in the opposite direction and dominates at a lower suction flow ratio and these disturbances disappear at a large suction flow ratio.

Improvement of the conductivity and transmittance of AZO/Ag/AZO composite film via lattice oxygen ratio regulation

High conductivity and high transmittance are usually contradictory for transparent conductive films. AZO/Ag/AZO composite film was deposited with magnetron sputtering on K9 glass substrate at room temperature, and O 2 was used as the reactive gas to control the ratio of lattice oxygen and that of oxygen vacancy in the bottom AZO layer, which regulated the composite film's conductivity and transmittance. The results showed that the lattice oxygen ratio of the bottom AZO layer first increased and then decreased as the O 2 flow ratio increased from 0% to 30%, while the oxygen vacancy ratio decreased continuously; both the in-plane stress in the AZO layer and the lattice mismatch between AZO and Ag layers first decreased and then increased. The crystallization quality of the Ag layer increased first and then decreased and got the best at 10% O 2 flow ratio, while the roughness first decreased and then increased, and got the minimum value at 10% O 2 flow ratio. As the O 2 flow ratio increased from 0% to 30%, the transmittance of the AZO/Ag/AZO composite film first increased and then decreased, while the sheet resistance first decreased and then increased; when the O 2 flow ratio was 10%, the average visible transmittance (380–780 nm) of the composite film got the maximum 78.28%, the sheet resistance got the minimum 6.745 Ω/sq. • AZO/Ag/AZO composite film was deposited with magnetron sputtering at room temperature. • The lattice oxygen ratio first increased and then decreased with O 2 flow ratio increase. • The lattice mismatch between AZO/Ag layers got the minimum at 76% lattice oxygen ratio. • Ag layer surface roughness was depended on the lattice mismatch. • The film got an average visible transmittance 78.28% and a sheet resistance 6.745 Ω/sq.

Effect of O2/Ar flow ratio and heat treatment on the structure and properties of SiO2 film prepared by magnetron sputtering

SiO2 thin film was deposited on quartz glass substrate with radio frequency (RF) magnetron sputtering. The effects of O2/Ar flow ratio and heat treatment on the O/Si molar ratio, surface morphology and optical properties of the film were investigated. SiO2 film was composed of amorphous nanoparticles. When the O2/Ar flow ratio increased from 30% to 60%, the film's O/Si ratio increased continuously from severe O-deficiency 1.68:1 to 1.93:1, close to the stoichiometric ratio 2:1. Meanwhile, the particles' average size decreased and became more uniform, and the surface roughness decreased with the O2/Ar flow ratio increase. And the film's refractive index and absorptivity decreased continuously, while the coated glass substrate's average transmittance (hereinafter referred to as the film's transmittance) within 300–1100 nm increased from 91.7% to 92.9% continuously. Heat treatment at 550 °C resulted in an obvious agglomeration of the nanoparticles, reduced the refractive index of the film and improved its transmittance.

An In Vivo Data-Based Computational Study on Sitting-Induced Hemodynamic Changes in the External Iliac Artery.

Although sedentary behavior (characterized by prolonged sitting without otherwise being active in daily life) is widely regarded as a risk factor for peripheral artery disease (PAD), underlying biomechanical mechanisms remain insufficiently understood. In this study, geometrical models of ten external iliac arteries were reconstructed based on angiographic data acquired from five healthy young subjects resting in supine and sitting (mimicked by side lying with bent legs) positions, respectively, which were further combined with measured blood flow velocity waveforms in the common iliac arteries (with each body posture being maintained for 30 min) to build computational models for simulating intra-arterial hemodynamics. Morphological analyses showed that the external iliac arteries suffered from evident bending deformation upon the switch of body posture from supine to sitting. Measured blood flow velocity waveforms in the sitting position exhibited a marked decrease in mean flow velocity while increase in retrograde flow ratio compared with those in the supine position. Hemodynamic computations further revealed that sitting significantly altered blood flow patterns in the external iliac arteries, leading to a marked enlargement of atheroprone wall regions exposed to low and oscillatory wall shear stress (WSS), and enhanced multidirectional disturbance of WSS that may further impair endothelial function. In summary, our study demonstrates that prolonged sitting induces atheropromoting hemodynamic changes in the external iliac artery due to the combined effects of vascular bending deformation and changes in flow velocity waveform, which may provide important insights for understanding the involvement of biomechanical factors in sedentary behavior-related PAD.

Study on a new pressure loss model of T-junction for compressible flow with particle image velocimetry test

The energy transfer and conversion of exhaust gas flowing across junctions of exhaust manifold plays an important role in determining performance of turbocharging system. With the increase of engine boost pressure, exhaust gas velocity increases significantly, which increased compressibility of exhaust gas flow simultaneously. The existed exhaust T-junction models that do not take gas compressibility into consideration are not capable to simulate the exhaust gas flow with high boost pressure good enough. In order to predict pressure loss coefficients of high-pressure gas flow with higher accuracy, this paper developed a new T-junction models in which compressibility of gas flow was taken into consideration. A particle image velocimetry (PIV) test rig was established to provide data for investigating influences of flow parameters on the flow state and thermodynamic parameters in the T-junction. The results show that there are obvious streamline contractions in the internal flow field of the junction, and the formed boundary streamline divides the junction into two regions, as the flow ratio increases, the absolute value of the vorticity increases, and the vorticity in most areas of the branch joint is zero. In addition, the flow ratio of the branch pipe and the main pipe and the Mach number of the outflow affect the flow of the junction. Based on the results of the PIV test, a new pressure loss coefficient T-junction model for compressible flow is proposed. The new model has good prediction accuracy of the pressure loss coefficient and the prediction accuracy of the exhaust pressure wave increases by 4.43% when the pressure coefficient model is used in one-dimensional simulation program.

Oxygen doping effect on wettability of diamond-like carbon films

DLC films were deposited on Ge substrates using direct ion beam deposition method, followed by investigating the influence of O2 doping on their morphological, electrical, and structural properties. The films were doped with oxygen under flow rates of 5, 10, 20, and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy. Result showed that by increasing oxygen incorporation, sp2 content decreases, sp3 content increases, and the C-C bonding loses its order. The hydrophilicity of the layers was analyzed by the contact angle measuring experiment. The results showed that by increasing the O2 flow ratio from 5 to 40 sccm, the percentage of O2 increases from 1.1 to 3.9%. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°.

Pedestrian crossing design and analysis for symmetric intersections: Efficiency and safety

Abstract Traffic engineers are making efforts to mitigate congestion and to improve efficiency at intersections. The symmetric intersection (SI) can increase the capacity of intersections and is economical, practical, efficient and convenient. The pedestrians’ crossing patterns tailored for SI has not yet been studied. This paper not only develops three pedestrian crossing patterns but also analyzes crossing patterns from the aspects of efficiency and safety. For efficiency, delay models are proposed by considering through and diagonal pedestrian movements. For safety, exposure conflicts and the number of potential traffic accidents are analyzed. Then delay and potential accidents are converted into money value respectively and the total cost is calculated. The case study results show that SI performs better in terms of increasing capacity and decreasing pedestrian delay compared with conventional intersection. Crossing pattern 1 is efficient but unsafe while the total delay and safety cost of pattern 3 is usually the highest. The sensitivity analysis indicates that cycle length has a negative impact on average pedestrian cost and if critical flow ratio increases, the average pedestrian cost of pattern 1 and pattern 3 will increase and decrease respectively. Furthermore, the best pedestrian pattern choice under different values of cost per accident and cost of pedestrian delay is also studied.

P‐45: Effect of Ar / O2 Flow Ratio during Sputtering of InZnO Active Layer on Photocurrent and Responsivity Characteristics of Amorphous InZnO Thin Film Transistors

The photocurrent and responsivity characteristics of amorphous InZnO (a‐IZO) thin film transistors (TFTs) under different Ar:O2 gas flow ratio when growing the IZO active layer by sputtering are investigated. As the Ar:O2 gas flow ratio increases, the photocurrent and responsivity increase by nearly two orders of magnitude, under the same light power density at a wavelength of 400 nm to 475 nm light illumination.

Too Big, Too Small or Just Right? Why the 28 French Chest Tube Is the Best Size

BackgroundTube thoracostomy is a commonly performed procedure in trauma patients. The optimal chest tube size is unknown. This study measures chest tube drainage in a controlled laboratory setting and compares measured flowrates to those predicted by the Hagen–Poiseuille equation. Materials and methodsA model of massive hemothorax was created, consisting of a basin containing synthetic blood substitute (aqueous Glycerin and Xanthan gum) and a standard pleur-evac setup at −20 cm H2O suction. Flow measurements were calculated by measuring the time to drain 2L of blood substitute from the basin. Chest tube sizes tested were 20F, 24F, 28F, 32F, and 36F. Thoracostomy opening was modeled using custom built device that represents two ribs, with the distance between varied 2 to 12 mm. Flowrate increases were compared against predicted increases according to the Hagen–Poiseuille equation. Percent of predicted increase was calculated, both incremental increase and using 20F tube benchmark. ResultsAll tubes were occluded at a 2 mm thoracostomy opening. At 3 mm, 32F and 36F were occluded while smaller tubes were patent. Tubes 28F and larger exhibited high speed and consistent flowrates, even after decreasing thoracostomy opening down to 7 mm, while flowrates rapidly decreased at opening smaller than 7 mm. Smaller 24F and 20F tubes exhibited highly variable flowrates through the system. Maximum flowrates were 21.7, 36.8, 49.6, 55.6, and 61.0 mL/s for 20F–36F tubes, respectively. The incremental increase in flow ratio for increasing chest tube size was 1.69 (20F to 24F), 1.35 (24F to 28F), 1.12 (28F to 32F), and 1.10 (32F to 36F). ConclusionsThe 28F chest tube exhibited high and consistent velocity, while smaller tubes were slower and more variable. Larger tubes offered only slightly higher flowrates. The 28F is a good balance of reasonable size and high flowrate and is likely the optimal size for most clinical applications.

Conjugate Heat Transfer Predictions on Combined Impingement and Film Cooling of a Blade Leading Edge Model

In this paper, numerical simulation is performed to predict combined impingement and film cooling on a model of the turbine blade leading edge by the heat flow coupling method. The first-stage rotor blade leading edge of the GE-E3 engine high-pressure turbine is adopted for the simulation. The relative performances of turbulence models are compared with experimental data and the results show that standard k-ω model is the best, based on simulation accuracy. The standard k-ω model is adopted for the simulation. A grid independence study is also carried out. Five different mass flow ratios and seven different film cooling hole configurations are studied in detail. The results indicate that (1) the overall film cooling effectiveness on the leading edge surface and the Nusselt number on the target surface increase with increases of coolant mass flow ratio; (2) the blade leading edge temperature decreases with an increase in mass flow ratio; and (3) the area-averaged overall film cooling effectiveness increases with a decrease in spanwise film cooling injection angle, when the injection angle is lower than 25°, while it does not change much otherwise.

Carotid Revascularization and Its Effect on Cognitive Function: A Prospective Nonrandomized Multicenter Clinical Study

Background: There is conflicting data on the effect of carotid revascularization on cognitive function. Objective: To examine cerebral blood flow and cognitive function after carotid revascularization. Methods: Patients with unilateral, asymptomatic hemodynamically significant carotid artery stenosis (80% by computed tomography angiography or magnetic resonance angiography) were eligible. Cerebral blood flow was measured preoperatively and 1 month postoperatively using quantitative phase contrast magnetic resonance angiography. Preoperative flow impairment was defined as ipsilateral flow at least 20% less than contralateral flow (ie, an ipsilateral and/or contralateral flow ratio ≤0.8). Significant improvement in blood flow was defined as at least a 0.15 increase in flow ratio from pre- to postoperative. A control group was managed medically. Four cognitive domains were assessed at baseline, 1 month, and 6-12 months postoperatively. Results: Seventy-five patients were enrolled at 6 sites; 53 carotid endarterectomy, 11 carotid artery stenting, and 11 medical management only controls. Preoperative Trails B scores were similar between groups. Revascularization was associated with significant improvement in executive function (Trials B) while no improvement was observed in controls (P = .007). Of patients with improvement in middle cerebral artery (MCA) flow, 90% had improved Trails B scores compared to 46.5% of patients without MCA flow improvement (P = .01). Greater absolute improvement in mean Trails B scores was observed in patients with MCA flow improvement compared to those without (48 seconds versus 24.7 seconds, P = .001). Conclusions: In a cohort of patient with asymptomatic carotid stenosis, improvement in MCA flow following carotid revascularization is associated with improvement in executive functioning.