Experimental and numerical investigation of different geometrical parameters in a centrifugal blood pump

Purpose Due to the importance of public health and economics, cardiovascular disease has become one of the most important debates and challenges for scientists. However, few studies have been done to address this challenge. The main objective of this document is to provide an optimal model to improve the performance of the left ventricular assist device and reduce costs. In this way, in the present study, the experimental and numerical procedures were developed to analyze the effects of the geometrical features and operational parameters on the performance of a centrifugal blood pump (CBP). Methods In order to achieve this aim, first, experimental tests were carried out to study the influence of the working fluid temperature and the rotational speed on the CBP. Subsequently, the performance of the CBP was assessed using computational fluid dynamics (CFD), and comparison was made against the experimental data. In addition, the influence of mounting an inducer on the overall performance of CBP was also investigated. Results Good agreement between the CFD and the data was obtained. The CFD results showed that increasing the fluid temperature and rotational speed leads to an increase in the hydraulic efficiency, pressure difference, and power. In addition, the reduction of the pressure difference and hydraulic efficiency with increasing the surface roughness was observed. While mounting an inducer on the pump did not significantly impact its overall performance, the highest value of the wall shear stress dropped moderately on the impeller and, therefore, unveiled the possibility of improving the performance of such designs.

Switching Control of Latex Balloon Expansion by using Switching Valve mediated with the Coanda Effect

Soft robots have advantages in terms of safety, softness, and compliance compared to traditional robotic systems. However, fluid-driven soft actuators, often employed in soft robots, require a corresponding number of bulky pressure supplies/valves to drive. Here, we consider a valve that can control the flow without mechanical moving parts for simplifying the driving system of soft actuators. We developed a system comprising a pump, a switching valve, and two latex balloons to demonstrate the feasibility of introducing a fluid valve into soft robotics. As the valve, which makes use of the Coanda effect, can switch the flow between two outlets when the pressure difference between the outlets is 3 kPa, we employed a latex balloon connected to each outlet. The system can control the expansion of each balloon by switching the flow from the pump. The experimental results proved that the system could actuate each balloon.

Influences of Randomly Uncertain Factors on Dynamic Coefficients of an Interlocking Labyrinth Seal-Rotor System

Many randomly uncertain factors inevitably arise when gas flows through a labyrinth seal, and the orbit of the rotor center will not rotate along a steady trajectory, as previously studied. Here, random uncertainty is considered in an interlocking labyrinth seal-rotor system to investigate the fluctuations of dynamic coefficients. The bounded noise excitation is introduced into the momentum equation of the gas flow, and as a result, the orbit of the rotor center is expressed as the combination of an elliptic trajectory with the bounded noise perturbation. Simulation results of the coefficients under randomly uncertain perturbations with various strengths are comparatively investigated with the traditional predictions under ideal conditions, from which the influences of random uncertain factors on dynamic coefficients are analyzed in terms of the rotor speed, pressure difference, and inlet whirl velocity. It is shown that the deviation levels of the dynamic coefficients are directly related to the random perturbations and routinely increase with such perturbation strengths, and the coefficients themselves may exhibit distinct variation patterns against the rotor speed, pressure difference, and inlet whirl velocity.

Fuel Flowrate Control for Aeroengine and Fuel Thermal Management for Airborne System of Aircraft—An Overview

Fuel flowrate control system and fuel thermal management are very important for aeroengine and the overall aircraft, and it has been researched for several decades. This survey paper makes a comprehensive and systematic overview on the exiting fuel flowrate regulation methods, thermal load of fuel metering units, fuel-based thermal management, and the fuel tank’s thermal management topology network with drain and recirculation. This paper firstly reviews the mechanism, technical advantages, and technical challenges of the fuel metering unit with flowrate control valve and constant pressure difference valve compensator, flowrate control valve and variable displacement pump-based pressure difference compensator, and motor-based flowrate regulation. Then, the technical characteristics of above fuel flowrate control methods related to thermal management are discussed and compared. Meanwhile, the behaviors of recirculated fuel flow within single tank system and dual tank system are explored. Thirdly, the paper discusses the future directions of fuel flowrate control and thermal management. The survey is significant to the fuel flowrate control and fuel thermal management of the aircraft.

Underwater gas self-transportation along the femtosecond laser-written open superhydrophobic surface microchannels (< 100 µm) for bubble/gas manipulation

Underwater transportation of bubbles and gases has essential applications in manipulating and using gas, but there is still a great challenge to achieve this function at the microscopic level. Here, we report a strategy to self-transport gas along the laser-induced open superhydrophobic microchannel with a width less than 100 µm in water. The femtosecond laser can directly write superhydrophobic and underwater superaerophilic microgrooves on the polytetrafluoroethylene (PTFE) surface. In water, the single laser-induced microgroove and water medium generate a hollow microchannel. When the microchannel connects two superhydrophobic regions in water, the gas can be spontaneously transported from the small region to the large area along this hollow microchannel. The gas self-transportation can be extended to the laser-drilled microholes through a thin PTFE sheet. Anti-buoyancy unidirectional penetration is even achieved. The gas can overcome the buoyance of the bubble and spontaneously transport downward. The Laplace pressure difference drives the processes of spontaneous gas transportation and unidirectional bubble passage. We believe the property of gas self-transportation in the femtosecond laser-structured open superhydrophobic and underwater superaerophilic microgrooves/microholes has significant potential applications related to manipulating underwater gas.

On the One-Point Model for the Productivity Evaluation in Jingbian Sector of Yan’an Gas Field

The productivity equation of a gas well is, in the final analysis, an expression that describes the relationship between the production of a gas well and its bottom-hole flowing pressure. There are two kinds of productivity equations in common use at present: binomial productivity equation and exponential productivity equation. Combined with the modified isochronal well test, the test data are interpreted, and it is found that the open flow rates calculated by the two productivity equations are basically the same when the pressure difference at the test point is large, and the deviation of the exponential productivity equation is large when the pressure difference at the test point is small. Using binomial productivity equation and modifying isochronous well test, we established the single-point deliverability formula for the Jingbian sector of the Yan’an gas field. The field experience formula and production data are used to verify it. Their average errors are 2.59% and 7.12%, respectively; and the coincidence rate of productivity evaluation is 90%. The one-point productivity formula established has high precision and is suitable for productivity analysis of gas wells in paleozoic reservoirs in the Jingbian sector of the Yan’an gas field. This paper provides insights into the one-point productivity evaluation and its future application in the gas field.

An Investigation Into the Effect of Pre-bending on the Tube Hydro-forging Technology

Tube hydro-forging (THFG) combining with the pre-bending is an advanced method to manufacture the complex cross-sectional tubular component with curved axis. However, the effect of pre-bending on the subsequent THFG, especially on the critical internal pressure required to inhibit wrinkling, has not been clarified yet. Therefore, this paper makes a detailed study on it. At first, based on the energy method, the change rule between the critical internal pressure and the hoop strain was established when pre-bending was considered. Subsequently, the mechanics condition difference between single and double curvature differential segment during THFG was analyzed. Via the plastic theory, the distribution of hoop strain could be obtained. Mainly due to the uneven distribution of thickness and cold work-hardening caused by pre-bending, the maximum hoop strain at the outer straight-wall was greater than that at the inner straight-wall during THFG. Substituting the maximum hoop strain at the outer/inner straight-wall into the change rule, then their mathematical model of the critical internal pressure to restrain the wrinkling could be solved respectively. Finally, the critical internal pressure considering pre-bending was determined by that of outer straight-wall, and its value was always greater than the critical internal pressure without considering pre-bending under the same punch stroke. With the increase of bending radius, the critical internal pressure difference between considering and not considering pre-bending also increases. When the bending radius was 250 mm, the critical internal pressure difference was 33%, while it increased to 74% as the bending radius reduced to 100 mm, all of which were verified by experiment. The effect of friction coefficient on the critical internal pressure was also studied. In conclusion, this work provided a new and more accurate prediction model of critical internal pressure to guide practical production for when existing the pre-bending.

Interannual variability of atmospheric Nitrous Oxide (N2O)

The 12-monthly running means of N2O measured at seven locations during 1977-91 were used for obtaining the yearly percentage growth rate series (4 values per year, centered 3 months apart), which were subjected to MESA (Maximum Entropy Spectral Analysis). The spectra revealed significant QBO and QTO (Quasi-biennial and Quasi-triennial oscillations) with QBO periods in the range (2.04-2.38) years and QTO periods near 4.0 years. These do not resemble the QBO of 2.58 years of the 50 hPa low latitude wnal wind but do resemble the QBO of 2.31 years and the 4.1 year periods of the Southern oscillation phenomenon, represented by Tahiti minus Darwin sea level atmospheric pressure difference (T-D).

Study of Relationships between Ceiling Smoke Leakage Rate and Evacuation Time in the Ward

With reference to the requirements of CNS 15038 and testing principles, this study proposes a set of equipment for measuring the leakage volume of ceilings and provides detailed assembly specifications for future users. In this study, a total of 405 tests were conducted as part of a set of experiments for measuring the leakage volume of ceilings, using various ceiling materials, ceiling sizes, and construction methods, in conjunction with the principles of fluid mechanics, to propose a method for evaluating the leakage volume of ceilings of various sizes and materials. Two cases—bottom-up airflow and top-down airflow—were considered. According to our research findings, in the case of bottom-up airflow, the pressure difference, panel weight, and panel size were correlated with the leakage volume; the more significant the pressure difference, the larger the leakage volume; the heavier the panel weight, the more minor the leakage volume; and the larger the panel size, the more significant the leakage volume. On the other hand, in the case of top-down airflow, different leakage volumes were observed for different ceiling materials, even if the ceiling size was identical. On the other hand, when the ceiling material was the same, and the ceiling size was different, there was not a positive relationship between the leakage volume and a larger panel size; instead, the leakage volume observed for the largest panel was the smallest. Finally, in this study we propose a volumetric leakage assessment table for assessing a ceiling as a whole, which can be utilized by engineers in the future to calculate the smoke leakage value and to estimate the smoke fall time for ward escape designs.