scholarly journals Dynamic Characteristics and Wall Effects of Bubble Bursting in Gas-Liquid-Solid Three-Phase Particle Flow

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 760 ◽  
Author(s):  
Jianfei Lu ◽  
Tong Wang ◽  
Lin Li ◽  
Zichao Yin ◽  
Ronghui Wang ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Phase Particle ◽  
Particle Flow ◽  
Wall Effects ◽  
Bubble Bursting ◽  
Three Phase ◽  
Bursting Process ◽  
Bubble Burst

The bubble bursting process existing in the particle flow is a complex gas-liquid-solid three-phase coupling dynamic problem. The bubble bursting mechanism, including dynamic characteristics and wall effects, is not clear. To address the above matters, we present a modeling method for the piecewise linear interface calculation-volume of fluid (PLIC-VOF) based bubble burst. The bubble bursting process near or on the wall is analyzed to reveal the dynamic characteristics of bubble bursting and obtain the effect of a bubble bursting on the surrounding flow field. Then a particle image velocimetry (PIV) based self-developed experimental observation platform is established, and the effectiveness of the proposed method is verified. Research results indicate that, in the high-speed turbulent environment, a large pressure difference existed in the bubble tail, which induces the bubble burst to occur; the distance between the wall and the bubble decreases; the higher the flow velocity is, the less time is acquired for bubble bursting, but when the flow velocity exceeds the critical velocity 50 m/s, more time is needed; the coalescence-burst process of double bubbles increases the bubble bursting time, which causes the acceleration of particle motion to reduce.

Experimental Study on Bubble Bursting and Droplet Releasing Characteristics Under Different Liquid Phase Conditions

2018 ◽  
Author(s):  
Hao Chen ◽  
Haifeng Gu ◽  
Xiang Yu ◽  
Yanmin Zhou ◽  
Zhongning Sun ◽  
...  
Keyword(s):  
Liquid Phase ◽  
High Speed ◽  
Single Point ◽  
Experimental Studies ◽  
Phase Changes ◽  
Radioactive Aerosol ◽  
Bubble Bursting ◽  
Bubble Rising ◽  
Liquid Ring ◽  
Bursting Process

The phenomenon that bubble bursts at the water surface and results in droplets production is one of the source of radioactive aerosol release, when the gas goes through the aerosol pool. Based on this, a high-speed photographic visualization experimental device was used to visualize the bubble bursting process at liquid surface under different conditions. Experimental studies show that: the bursting process of the bubbles with 7mm–28mm in diameter is a Single point rupture process. The process includes bubble rising, bubble cap draining, punctured point appearing, the liquid film rolling-up which forms the liquid ring, droplets emission as liquid ring breaks. The different punctured position changes the process of bubble bursting and the distribution of the droplets, thus the location of punctured position were divided into different area, which mainly locates at the foot of the bubble cap. Furthermore, the change of liquid phase conditions will affects the location of the punctured position, the number and the sizes of droplets. In the experiments, as temperature of the liquid phase changes from 16°C to 60°C, the process of drainage of bubble cap is shortened, and the probability of punctured position at the bottom increases. When punctured position is the same position, the number of droplets decreased and the diameter of droplet increased as temperature was increasing.

Direct Current Deadbeat Predictive Controller for BLDC Motor Using Single DC-Link Current Sensor

2020 ◽  
Vol 38 (8A) ◽  
pp. 1187-1199
Author(s):  
Qaed M. Ali ◽  
Mohammed M. Ezzalden
Keyword(s):  
Control System ◽  
High Speed ◽  
Fast Response ◽  
Bldc Motor ◽  
Current Controller ◽  
Three Phase ◽  
Predictive Controller ◽  
Two Phases ◽  
Dc Current ◽  
Three Phase Inverter

BLDC motors are characterized by electronic commutation, which is performed by using an electric three-phase inverter. The direct control system of the BLDC motor consists of double loops; including the inner-loop for current regulating and outer-loop for speed control. The operation of the current controller requires feedback of motor currents; the conventional current controller uses two current sensors on the ac side of the inverter to measure the currents of two phases, while the third current would be accordingly calculated. These two sensors should have the same characteristics, to achieve balanced current measurements. It should be noted that the sensitivity of these sensors changes with time. In the case of one sensor fails, both of them must be replaced. To overcome this problem, it is preferable to use one sensor instead of two. The proposed control system is based on a deadbeat predictive controller, which is used to regulate the DC current of the BLDC motor. Such a controller can be considered as digital controller mode, which has fast response, high precision and can be easily implemented with microprocessor. The proposed control system has been simulated using Matlab software, and the system is tested at a different operating condition such as low speed and high speed.

A modified damping model of vector form intrinsic finite element method for high-speed spiral bevel gear dynamic characteristics analysis

2021 ◽  
pp. 030932472110188
Author(s):  
Xiangying Hou ◽  
Yuzhe Zhang ◽  
Hong Zhang ◽  
Jian Zhang ◽  
Zhengminqing Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Numerical Solutions ◽  
Bevel Gear ◽  
Spiral Bevel Gear ◽  
Vector Form ◽  
Good Efficiency ◽  
Spiral Bevel ◽  
Damping Model

The vector form intrinsic finite element (VFIFE) method is springing up as a new numerical method in strong non-linear structural analysis for its good convergence, but has been constricted in static or transient analysis. To overwhelm its disadvantages, a new damping model was proposed: the value of damping force is proportional to relative velocity instead of absolute velocity, which could avoid inaccuracy in high-speed dynamic analysis. The accuracy and efficiency of the proposed method proved under low speed; dynamic characteristics and vibration rules have been verified under high speed. Simulation results showed that the modified VFIFE method could obtain numerical solutions with good efficiency and accuracy. Based on this modified method, high-speed vibration rules of spiral bevel gear pair under different loads have been concluded. The proposed method also provides a new way to solve high-speed rotor system dynamic problems.

scholarly journals Optimization of Air Gap Length and Capacitive Auxiliary Winding in Three-Phase Induction Motors Based on a Genetic Algorithm

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4407
Author(s):  
Mbika Muteba
Keyword(s):  
Genetic Algorithm ◽  
Design Process ◽  
Power Factor ◽  
High Speed ◽  
High Efficiency ◽  
Air Gap ◽  
Element Analysis ◽  
Three Phase ◽  
High Torque ◽  
Cage Induction Motor

There is a necessity to design a three-phase squirrel cage induction motor (SCIM) for high-speed applications with a larger air gap length in order to limit the distortion of air gap flux density, the thermal expansion of stator and rotor teeth, centrifugal forces, and the magnetic pull. To that effect, a larger air gap length lowers the power factor, efficiency, and torque density of a three-phase SCIM. This should inform motor design engineers to take special care during the design process of a three-phase SCIM by selecting an air gap length that will provide optimal performance. This paper presents an approach that would assist with the selection of an optimal air gap length (OAL) and optimal capacitive auxiliary stator winding (OCASW) configuration for a high torque per ampere (TPA) three-phase SCIM. A genetic algorithm (GA) assisted by finite element analysis (FEA) is used in the design process to determine the OAL and OCASW required to obtain a high torque per ampere without compromising the merit of achieving an excellent power factor and high efficiency for a three-phase SCIM. The performance of the optimized three-phase SCIM is compared to unoptimized machines. The results obtained from FEA are validated through experimental measurements. Owing to the penalty functions related to the value of objective and constraint functions introduced in the genetic algorithm model, both the FEA and experimental results provide evidence that an enhanced torque per ampere three-phase SCIM can be realized for a large OAL and OCASW with high efficiency and an excellent power factor in different working conditions.

Dynamic characteristics of a drill in the drilling process

2003 ◽  
Vol 217 (2) ◽  
pp. 161-167 ◽  
Author(s):  
B W Huang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Thrust Force ◽  
Time Dependent ◽  
Drilling Process ◽  
Improve Quality ◽  
Vibration Model ◽  
High Speed Drilling ◽  
Spinning Speed ◽  
Twisted Beam

The dynamic characteristics of high-speed drilling were investigated in this study. To improve quality and produce a higher production rate, the dynamic characteristics of the drilling process need to be studied. A pre-twisted beam is used to simulate the drill. The moving Winkler-type elastic foundation is used to approximate the drilling process. A time-dependent vibration model for drilling is presented. The spinning speed, pre-twisted angle and thrust force effects of the drill are considered. The numerical analysis indicates that the natural frequency is suddenly reduced as the drill moves into a workpiece.

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