Driving Air Pressure Research Articles

Isolated slug traveling in a voided line and impacting at an end orifice

Driven by upstream high-pressure steam, liquid slugs in nuclear power plant pipelines impact the end orifice at high speed, leading to bursting pipelines and threatening the plant's safety. This research aimed to accurately and efficiently assess the dynamic behavior of an isolated slug driven by pressurized air in a voided line with an end orifice. An improved one-dimensional (1D) model for the slug motion and impact was established. The dynamic variation of the pressure at both the slug's tail and front, the variation of the slug length, and the frictional resistance coefficient in the model was obtained by three-dimensional (3D) computational fluid dynamics (CFD). Based on 27 cases with different pipeline diameters and tank pressures, it was observed that the driving air pressure had a quadratic relationship and that the slug length had a constant rate of decrease vs the slug tail displacement. Finally, the decrease in the driving air pressure behind the slug, the increase in the air pressure ahead of the slug, the holdup coefficient, and the friction factor obtained from the 3D CFD results were interpreted in the 1D model, and the velocity histories of the liquid slug were found to be in excellent agreement with the 3D CFD solutions.

3D printed smart elastomeric foam with force sensing and its integration with robotic gripper

Robotic grippers are extensively investigated as terminal actuators for gripping workpieces in robotic applications. Lately, implementing closed-loop force control for grippers to grip fragile workpieces securely is attractive. This paper aims to provide a dual-security solution combining gripping force control and stress-buffering capability. An integrated force-sensitive smart polydimethylsiloxane (PDMS) foam containing an embedded force-sensitive resistor (FSR) was designed and directly fabricated by 3D printing technology. The real-time force measurement was fed back into the control loop with proportional-integral (PI) rectification to precisely regulate the driving air pressure. In addition, the inherent stress plateau effect of the PDMS foam structure provides a constant stress buffer to absorb potential collision energy. The results show that the dual-security gripper with smart PDMS foam is able to precisely control the applied force and reliably grip fragile objects even in the presence of disturbances, enhancing the reliability of gripping applications. • Smart elastic foams with embedded force sensing capability are designed and 3D printed. • The printed smart elastic foams provide tunable mechanical and electrical properties. • The smart foam integrated with robotic gripper exhibits excellent stress buffering and closed-loop force feedback performance.

Three-dimensional CFD analysis of liquid slug acceleration and impact in a voided pipeline with end orifice

ABSTRACT This research describes the dynamic behavior of an isolated slug driven by pressurized air in a voided line with an end orifice. A three-dimensional (3D) computational-fluid-dynamics (CFD) model is used to simulate the rapid propulsion and impact at the orifice for given slug length and driving air pressure, and is validated against experimental data. New mechanisms are observed: (i) the driving air pressure at the slug tail decreases with the slug motion; (ii) when the slug arrives at the orifice, the air fraction is almost one hundred percent in the most upstream part of the pipe, then it attenuates rapidly until an invariant eighty percent is achieved with a constant mass shedding rate; (iii) the velocity distribution in the radial direction of the cross-section at the midpoint of the slug length evolves from uniform to trapezoidal and then to logarithmic during slug movement; (iv) the initial vertical slug front changes its shape due to air intrusion at the top of the slug front; (v) the slug’s acceleration decreases first and then increases under the combined effects of its decreasing mass, nonlinear attenuation of the driving pressure, and increasing skin friction; (vi) the slug length has a constant rate of decrease.

Study on the Structure and Performance of an Antagonistic Pneumatic Bidirectional Rotary Joint

An antagonistic pneumatic bidirectional rotary flexible joint was developed to improve both safety and environmental adaptability of service robots and associated human interactions. The joint comprises two semicircular rotary actuators with positive and negative symmetrical distributions and a pneumatic brake. As such, it achieves forward and reverse rotations, and its damping and braking are adjustable in real time, enabling it to maintain its position. According to the force/torque balance at the free end of the rotary actuator, the rotation angle static model was established. The relationship between the actuator rotation angle, driving torque, impedance torque, and air pressure was obtained experimentally. The brake airbag was manufactured using additive manufacturing and silicone gel casting technologies. The mathematical model of the braking torque was established next, and the model was verified through experiments. Furthermore, an experimental system was constructed to carry out the air pressure-angle, air pressure-torque, and speed response experiments without the load on the joint. The results have shown that the joint can achieve any position within ± 68.5° when the driving air pressure varies from 0 to 0.30 MPa; the time required to reach the maximum angle was 0.85 s. The joint has shown good adjustable damping characteristics. Lastly, the braking torque reached 4.21 Nm at 0.32 MPa, effectively maintaining the position.

An Octopus-Inspired Bionic Flexible Gripper for Apple Grasping

When an octopus grasps something, the rigidity of its tentacle can change greatly, which allowing for unlimited freedom, agility, and precision. Inspired by this, a three-finger flexible bionic robot gripper was designed for apple picking. First, a flexible chamber finger was designed to drive the gripper finger to elongate, shorten, and bend, which works through a process of inflating and deflating. Further, we proposed a three-finger mode to achieve two kinds of motion states: grasping and relaxing, by simulating the movement of an octopus grasping at something. In this paper, we evaluated the bending property of the designed flexible bionic gripper through an apple grasping experiment. The experimental results show that the 100.0 g bionic gripper can load an apple with a weight of 246.5~350.0 g and a diameter of 69.0~99.0 mm, and the grasping success rate is 100%. It has a good grasping performance. Compared to other soft grippers, the proposed bionic flexible gripper has the advantages of being lightweight, and having good cushioning, low driving air pressure, and a strong grasping force.

Research on Multi-point Continuous Electromyography Control Algorithm and Its System for Multi-Finger Dexterous Hand

As the application field of robots expands from industry to agriculture, medical rehabilitation and service industries, its working environment becomes dynamic and not good. The end effectors of robots also need to be more flexible to adapt to changing operating objects. Based on the existing research of our group, a multi-finger dexterous hand included two kinds of bending joints is designed which used human hand as the prototype and combined with the characteristics of human hand joint movement. The EMG signal is proposed as the control source to improve the diversity and flexibility of dexterous hand movement. In the link of EMG signal processing algorithm, EMG signal feature value of the independent and complete action is discretized to form a continuous characteristic parameter curve. And multi-point continuous myoelectric control which is used to characterize the action process can be realized. The real-time adjustment of the driving air pressure is realized by the control system. And the system can control the different action forms of multi-finger dexterous hand. Finally, the relative error of proposed control algorithm and its system was verified to be about 3.23% by the joint position control test.

Variation of Streaming Potentials with Time under Steady Fluid Pressure in Bone

This paper investigates the streaming potentials’ behaviors when fluid flows through the micropores in bone. An experimental setup was developed for measuring the streaming potentials between two surfaces of a bone plate specimen. It was found that the streaming potentials measured increased almost linearly with time under a constant fluid pressure gradient, which does not agree with the prediction from the classical theory of streaming potentials. To explain the reasons associated with the results obtained, a theoretical model was proposed in which the electric charge densities on the inner surfaces of the capillary are unevenly distributed. A formula was developed for solving the model, and the solutions demonstrate that nonuniform accumulations of electric charges carried by the fluid on the inner surfaces of the microcanals in bone can induce streaming potentials which linearly increase with time during the driving air pressure holding period. This phenomenon represents the specific characteristics of bone. The solution implies that the streaming potentials in Haversian canals, lacunas and canaliculi are not affected by electro-viscous resistance in the bone fluid.

Dynamic Force on an Elbow Caused by a Traveling Liquid Slug

The impact force on an elbow induced by traveling isolated liquid slugs in a horizontal pipeline is studied. A literature review reveals that the force on the elbow is mainly due to momentum transfer in changing the fluid flow direction around the elbow. Therefore, to accurately calculate the magnitude and duration of the impact force, the slug arrival velocity at the elbow needs to be well predicted. The hydrodynamic behavior of the slug passing through the elbow needs to be properly modeled too. A combination of 1D and 2D models is used in this paper to analyze this problem. The 1D model is used to predict the slug motion in the horizontal pipeline. With the obtained slug arrival velocity, slug length, and driving air pressure as initial conditions, the 2D Euler equations are solved by the smoothed particle hydrodynamics (SPH) method to analyze the slug dynamics at the elbow. The 2D SPH solution matches experimental data and clearly demonstrates the occurrence of flow separation at the elbow, which is a typical effect of high Reynolds flows. Using the obtained flow contraction coefficient, an improved 1D model with nonlinear elbow resistance is proposed and solved by SPH. The 1D SPH results show the best fit with experimental data obtained so far.

Statistical analysis of the effects of polyethylene glycol concentration and molecular weight on the sedimentation and resuspendability behavior of model aqueous dispersions

This work investigates the flocculation effect of polyethylene glycol (PEG) on typical aqueous dispersions, such as O/W emulsions and solid/liquid suspensions. Hereby, sunflower oil and flubendazole were selected as model ingredients, whereas microfluidization at variable driving air pressure was used to enable particle size distribution variations for both systems. The molecular weight of PEG varied from 2000 to 12,000g/mol while its concentration ranged from 50 to 100mg/ml. Statistical analysis revealed that both PEG concentration and molecular weight showed a flocculation enhancing effect. Hereby the inhibiting effect of particle size toward the formation of voluminous and easily resuspendable sediment could at least partially be overcome by selecting appropriate PEG characteristics.

Study of the Different Factors That Influence Jet Pump Performance

The objective of this work is to study experimentally the characteristics of jet pump. Suction head, driving air pressure and the percentage of the distance between throat section and nozzle are recorded. The effect of each parameter on the pump performance is investigated, in order to have a better understanding about the behavior of such pump under various conditions. A simple geometry jet pump was designed, developed and tested. The experiments show that we should be careful in increasing the suction head, and stability must be considered between the suction head and the driving air mass flow rate. While the effect of increasing Pa will stop at certain maximum of the ratio of the mass flow rate of water to air (M), that is any increase in Pa will meet no change in M. While increasing S/Dth will leads to decrease in the percentage of M because the optimum S/Dth = 0.5 so that at this value we will have the best performance and any other values for S/Dth the percentage M will decreases, but this effect is not so clear and it could be neglected. The pump performance is not so sensitive with the change of S/Dth after S/Dth = 0.5. Also this information will help improving and extending the use of the jet pump in many practical applications.

An Artificial Larynx Built in TE Shunt Valve That Produces Substitute Voice by Only Patient's Own Expiration (Preliminary Study for Suitable Tone Pitch and Its Controllability)

A large portion of patients of larynx cancer tekes total laryngectomy and loses their original voice consequently. Some ways to obtain substitute voice for total laryngectomees have been presented, however, each of them cannot conquer inconveniences, tone quality, extremely low tone, monotonousness etc. We invented very simple, small enough to be built in TE (tracheaesophageal) shunt valve but functional substitute voice that is driven by patient's own expiration and its tone pitch can be controlled by expiratory pressure simultaneously. The new device has an outward-striking membrane as an oscillating valve and a set of piston-cylinder mechanism, which controls oscillator's tension and alters pitch of sound. As results of performance experiments applied to the prototype model made as twice scale as an actual dimension, the device produces the lowest sound frequency of 205 Hz and pitch range of 374 cent being approximately proportional to driving air pressure between 0.8 and 2.2 kPa. It is said that normal pitch of female voice is around 210 Hz, thus we consider the possibility of the device as a new substitute voice was shown that contributes to improvement of total laryngectomees' QOL particularly to female patients.

The effect of atmospheric pressure on ventricular assist device output

The effect of cabin pressure change on the respiratory system during flight is well documented in the literature, but how the change in atmospheric pressure affects ventricular assist device (VAD) output flow has not been studied yet. The purpose of our study was to evaluate the change in VAD output using a mock circulatory system in a low-pressure chamber mimicking high altitude. Changes in output and driving pressure were measured during decompression from 1.0 to 0.7 atm and pressurization from 0.7 to 1.0 atm. Two driving systems were evaluated: the VCT system and the Mobart system. In the VCT system, output and driving pressure remained the same during decompression and pressurization. In the Mobart system, the output decreased as the atmospheric pressure dropped and recovered during pressurization. The lowest output was observed at 0.7 atm, which was 80% of the baseline driven by the Mobart system. Under a practical cabin pressure of 0.8 atm, the output driven by the Mobart system was 90% of the baseline. In the Mobart system, the output decreased as the atmospheric pressure dropped, and recovered during pressurization. However, the decrease in output was slight. In an environment where the atmospheric pressure changes, it is necessary to monitor the diaphragmatic motion of the blood pump and the driving air pressure, and to adjust the systolic:diastolic ratio as well as the positive and negative pressures in a VAD system.

Development of a compact wearable pneumatic drive unit for a ventricular assist device

The purpose of this study was to develop a compact wearable pneumatic drive unit for a ventricular assist device (VAD). This newly developed drive unit, 20 x 8.5 x 20 cm in size and weighing approximately 1.8 kg, consists of a brushless DC motor, noncircular gears, a crankshaft, a cylinder-piston, and air pressure regulation valves. The driving air pressure is generated by the reciprocating motion of the piston and is controlled by the air pressure regulation valves. The systolic ratio is determined by the noncircular gears, and so is fixed for a given configuration. As a result of an overflow-type mock circulation test, a drive unit with a 44% systolic ratio connected to a Toyobo VAD blood pump with a 70-ml stroke volume achieved a pump output of more than 7 l/min at 100 bpm against a 120 mmHg afterload. Long-term animal tests were also performed using drive units with systolic ratios of 45% and 53% in two Holstein calves weighing 62 kg and 74 kg; the tests were terminated on days 30 and 39, respectively, without any malfunction. The mean aortic pressure, bypass flow, and power consumption for the first calf were maintained at 90 x 13 mmHg, 3.9 x 0.9 l/min, and 12 x 1 W, and those for the second calf were maintained at 88 x 13 mmHg, 5.0 x 0.5 l/min, and 16 x 2 W, respectively. These results indicate that the newly developed drive unit may be used as a wearable pneumatic drive unit for the Toyobo VAD blood pump.

IN VIVO AND CLINICAL STUDY OF PHOENIX-7 TOTAL ARTIFICIAL HEART

This paper concerned with results of implantation of the Phoenix-7 total artificial heart (TAH) in the growing calves. Experimental study had been conducted 41 times in 41 calves. All the calves could breathe, stand, eat and void by themselves in two hours after operation. The causes of death essentially included respiratory failure, sepsis, hemorrhage shock, thrombo-embolism, and multiple organ failure. Autopsy was performed in all deaths. The phoenix hearts were opened and examined. Blood morphology and blood chemistry were welt analyzed. Deformation of the red blood cells was found in most of the cases. Cell destruction, however, was not obvious. Besides, there was no evidence of red blood cell aggregation. Initial clinical experience was undertaken for a 46-year-old male who was in cardiogenic shock. The patient was indwelled with intra-aortic balloon counter-pulsation (IABP) and supported by extra-corporeal membrane oxygenator (ECMO) before the implantation. With IABP and ECMO, the patient's blood pressure was maintained at 90/60mmHg, but oliguria persisted with the complication of hemolysis. The patient was then implanted with the Phoenix-7 TAH and the condition was improved tremendously. With the TAH, the patient's blood pressure was maintained at 90∼100mHg / 40∼50mmHg. Cardiac output was adequately maintained at 4.2~5.8 Llmin by an operating model on modifying the parameters of driving air pressure for both the right and left hearts, heart rate and systolic ratio. The patient had been on the device for 15 days until a successful simultaneous orthotopic heart and heterotopic kidney transplantation from a suitable donor was undertaken.

An improved air-powered impulsive shear-wave source

Abstract We have previously constructed an air-powered, impulsive, SH-wave source for shear-wave velocity measurements using a downhole configuration. One shortcoming of that source is the existence of a forerunning signal generated by the reaction to the rapid acceleration of an inertial mass when a poppet value is opened. By changing the poppet valve to a ball valve, a cleaner signal is generated. The improvement comes about because when a ball valve is opened, its flow capacity increases gradually, resulting in a smooth and gradual acceleration of the inertial mass. Tests involving ground coupling and driving air pressure were conducted to investigate physical parameters of shear-wave generation. We illustrate as an application the measurement of shear-wave velocity in a loess layer.

Pulmonary mechanics of dogs during transtracheal jet ventilation

To quantify the delivered tidal volume and other selected measurements of pulmonary mechanics in an animal model during transtracheal jet ventilation (TTJV), with comparison to positive-pressure mechanical ventilation (PPMV) and spontaneous breathing. Prospective, nonblinded laboratory animal study. Seven mongrel dogs weighing 24.5 +/- 3.7 kg were anesthetized, paralyzed, and placed within a specially designed volume plethysmograph with the head and neck externalized. Ventilation was performed using TTJV under variable inspiratory time:expiratory time ratios (TI:TE) (1:1, 1:2, 1:3, 1:4, 1.5:2.5, 2:1, 2:2, 3:1, and 4:1) and variable driving air pressures (40, 45, and 50 psi). The dogs then were ventilated with PPMV. Tidal volume, tracheal pressure, transpulmonary pressure, air flow, arterial pressure, central venous pressure, and arterial blood gases were measured during spontaneous ventilation, TTJV, and PPMV. Quasistatic compliance of the lungs was measured after all methods of ventilation. Statistical significance was accepted at P < .05. There was no significant difference between delivered tidal volume during TTJV (446 +/- 69 mL at a TI:TE of 1:3 and 45 psi) and spontaneous breathing (506 +/- 72 mL). TTJV delivered a tidal volume significantly higher than the standard 15 mL/kg volume used for mechanical ventilation in dogs. Tracheal pressure and transpulmonary pressure were not significantly different between TTJV and PPMV. Variations in TI:TE had no significant effect on most of the measured variables, specifically tidal volume or transpulmonary pressure. Minute ventilation increased significantly and PCO2 decreased significantly as frequency increased during TI:TE settings of 1:1, 1:2, and 2:1. Increases in the driving air pressure during TTJV significantly increased the tidal volume as it was raised from 40 psi to 50 psi. There was no change in quasistatic lung compliance during any method of ventilation. TTJV delivers an effective tidal volume comparable to both spontaneous breathing and PPMV in a dog model. In the absence of upper-airway obstruction, there was no significant difference in the pulmonary pressures, resistance, and compliance during TTJV, as compared to mechanical ventilation. Variation in TI:TE during TTJV had no major effect on pulmonary mechanics, except to increase minute ventilation and decrease PCO2 as the frequency was increased significantly. Increasing the driving air pressure to the TTJV apparatus significantly augmented delivered tidal volume due to increased air flow.

Some functional aspects of air-jet nebulizers

Mass median aerodynamic diameters (MMADs, /xm), flow rates (1 air/min) and mass outputs (ml/min and μ1/1 air) were determined over a range of air pressures (psig) for a variety of clinically used nebulizers. Nebulizers were also modified to determine the rate at which fluid was aspirated from the nebulizer cup into the nebulizer jets (ml/min and μ1/1 air). Only a small fraction of this fluid emerges as aerosol that can be inhaled. The ratio of mass output to fluid uptake from the reservoir is termed mechanical efficiency. The stability of the enzyme lactate dehydrogenase (LDH) to nebulization at two different starting volumes was examined in the 3-jet Collison nebulizer. The results are discussed with respect to the measured operating characteristics. In all the nebulizers tested, MMADs were inversely related (e.g. 6.4 to 3.8 μm at 10 and 40 psig, respectively, for the ‘Cirrus’ nebulizer), whereas mass outputs (e.g. 0.11 to 0.35 ml/min at 10 and 40 psig for the ‘Misty’) and flow rates (e.g. 4.5 to 10.4 l/min at 10 and 40 psig for the Misty) were directly related, to the driving air pressure. MMADs and mass output are measures of how well nebulizers atomize liquid into droplets of respirable sizes. Aspiration rates varied substantially between the nebulizers and ranged from 9 ml/min (5 psig) to 28 ml/min (40 psig) for the DeVilbiss No. 45 whereas the Collison 3-jet nebulizer aspirated liquid at 118 ml/min (5 psig) to 333 ml/min (40 psig). All nebulizers exhibited an exponential decline in the aspiration rate of liquid expressed in terms of the throughput of air (ml/1 air). Rate constants ranged from 0.6 to 21.6 (× 10 −2 min/1 air) in the DeVilbiss No. 45 and Airlife Misty, respectively. These values give an indication of how the aspiration of fluid is affected by the air flow. Nebulizer mechanical efficiency was never > 2% (vents closed); this parameter is inversely related to the probable number of times that a drug will be aerosolized within the nebulizer. LDH was inactivated by nebulization. The degree of inactivation was greater at a 10 ml starting volume than at a 40 ml starting volume. The results indicate that monitoring the functional characteristics of nebulizers may be helpful in the assessment of drug stability.

A full-to-empty mode controller for the pneumatically-driven blood pump

Presented in this paper is a microprocessor-based controller developed based upon the theory of finite state automata to activate the pneumatically-driven diaphragm blood pump in the full-to-empty mode. Under normal situations, each pumping cycle of the blood pump can be divided into several phases in a proper sequence, and such phase information is contained in the driving air pressure waveform. The controller tries to match the sequential phases with the pressure waveform sampled at real time in an attempt to search for the end-ejection or end-filling of the blood pump. If either the end-ejection or the end-filling can be found, the controller sends triggering signals to the driving unit, and if the sampled pressure waveform can not be matched with the sequential phases or the controller fails to detect the end-ejection or end-filling, the controller activates the driving unit by the parameters of the last measured pumping cycle; thus, the driving unit triggers the blood pump without any stop. The results of laboratory bench tests demonstrates its ability in finding the end-ejection and end-filling points and the reliability of the fail-safe measure.

On-line pressure estimation for a left heart assist device

Long term measurement of blood pressures is essential for control of circulatory systems with artificial hearts or circulatory assist devices. Efforts to obtain reliable continuous direct measurements of blood pressures, however, have not been successful. This paper describes an on-line pressure estimation technique for use with a portable pneumatically driven left heart assist device. The on-line maximum likelihood algorithms are used for the estimation with the technique based on the use of physical models of the components of the driver and blood pump system. This technique estimates the inlet and outlet pressures of the blood pump. The directly measured driving air pressure and piston position of the pneumatic actuator are used for the estimation. In vitro and in vivo experiments were made to test the use of the on-line estimation technique. The results show successful linear correlations between the actual pressures and their estimates. This technique offers the following advantages: accurate pressure information for on-line control, accessibility to the transducers for recalibration, and noninvasive location of the transducers.

Open-End Spinning Frames Driven by Air-Jet

Various devices driven and supported by air jet were tested for a high speed open-end spinning frame. Two types of rotors were prepared: the upper fluting rotor and the under fluting rotor. Each rotor was driven by air jet running against the fluting directly from the nozzles drilled on the inner surface of a stator. The rotor was supported by the dynamic pressure of air. A series of tests were made by changing conical angles, number and angle of the flutings, and driving air pressure. The results were as follows.(1) The rotor speed increases with increasing the air pressure. (2) When the stator conical angle is 92°, the optimum rotor conical angle is 108° for the upper fluting, and 102° for the under fluting. (3) The suitable number of flutings is about 40 for the upper fluting, and 20 for the under fluting. (4) The angle of flutings exerts influence considerably on the driving torque, and the most suitable angle is 45° for the upper fluting, and 25° for the under fluting.