Numerical and experimental investigation on self-synchronization of two eccentric rotors in the vibration system

In this paper, we study the coupling dynamic characteristic of a single mass vibration machine driven by two eccentric rotors rotating oppositely. According to the coordinate of rotor flux, we deduce the electromagnetic torque of an induction motor in the steady state operation. From three ways of numerical analysis, model simulation and experiment, we discuss the coupling dynamic characteristic by using the actual parameters of this vibration machine. The results show that when the synchronization condition is satisfied, not only the vibration synchronization transmission can be achieved, but also the synchronization motion of the two motors with different power supply frequencies also can be achieved. The phase of the bigger mass-radius product lags behind that of the smaller one, the phase of the bigger distance between the rotation center of eccentric rotor and the mass center of the vibration rigid body lags behind that of the smaller one, and the phase difference decreases with increasing the synchronization velocity. We present a new method that adjusting the power supply frequencies of the two motors to make the vibration system with different structure parameters carry out the 0 phase difference, and its feasibility is verified by experiment

Numerical and experimental investigation on self-synchronization of two eccentric rotors in the vibration system

In this paper, we study the coupling dynamic characteristic of a single mass vibration machine driven by two eccentric rotors rotating oppositely. According to the coordinate of rotor flux, we deduce the electromagnetic torque of an induction motor in the steady state operation. From three ways of numerical analysis, model simulation and experiment, we discuss the coupling dynamic characteristic by using the actual parameters of this vibration machine. The results show that when the synchronization condition is satisfied, not only the vibration synchronization transmission can be achieved, but also the synchronization motion of the two motors with different power supply frequencies also can be achieved. The phase of the bigger mass-radius product lags behind that of the smaller one, the phase of the bigger distance between the rotation center of eccentric rotor and the mass center of the vibration rigid body lags behind that of the smaller one, and the phase difference decreases with increasing the synchronization velocity. We present a new method that adjusting the power supply frequencies of the two motors to make the vibration system with different structure parameters carry out the 0 phase difference, and its feasibility is verified by experiment

Thingking and utilization technology of coalbed methane in soft and low permeability coal seams in Huainan Mining Area

In order to solve the problems that restrict the efficient development of coalbed methane resources under the conditions of soft and low permeability outburst coal seams in Huainan Mining Area, such as complex coal seam structure, multi-source gas emission, rapid decline of drainage flow, high rock roadway and drilling costs, and low (ultra-low) concentration coalbed methane utilization rate, six key technologies suitable for the coordinated development mode of coal and coalbed methane under the condition of coal seam group mining in Huainan mining area are put forward, namely: coalbed methane extraction technology of ground level staged fracturing wells, shield rapid construction technology of coalbed methane extraction roadways, enhanced extraction technology of underground soft coalbed methane, coalbed methane extraction technology of pressure relief in ground mining area, the construction technology of "replacing roadways with holes", and cascade utilization technology of low concentration coalbed methane. The application of supporting key technologies shows that staged fracturing technology and refined drainage and production technology of roof horizontal wells in broken and soft coal seam have effectively improved the pre pumping production of coalbed methane; The full face hard rock roadheader in deep coal mine roadway greatly improves the roadway excavation efficiency, realizing the automation and less humanization of hard rock excavation; Sand adding of hydraulic fracturing and ultra-high hydraulic slotting have realized pressure relief and permeability enhancement in large areas underground coal mine; Type III and IV surface mining area wells can replace the roof high drainage roadway in the treatment of pressure relief gas in coal seam group mining, and reduce the coalbed methane drainage intensity of other measures; The technology of "replacing roadways with holes" has significantly improved the quality of successful directional drilling at middle and high levels in complex roof; Cascade utilization technology of low concentration coalbed methane has greatly reduced the emission of coalbed methane. The six key technologies have guaranteed the safe production in Huainan mining area, and comprehensively improved the output of coal and coalbed methane and the utilization level of coalbed methane. Six key technologies ensure the safe production in Huainan mining area, and comprehensively improved the output of coal and coalbed methane and the utilization level of coalbed methane. Finally, in view of the problems such as high operation cost, low production, small scope of hydraulic fracturing coal reservoir reconstruction technology for surface horizontal wells, and the risk of breakage of mining wells, and small scale of cascade utilization of ultra-low concentration coalbed methane, the development direction of deep CBM precise geological guidance, super large scale efficient reservoir volume transformation, pumping effect evaluation technology, stable and continuous pumping technology of surface wells in mining areas, underground large area intelligent hydraulic enhanced permeability technology, "one well with multiple uses" collaborative pumping CBM technology, and full concentration CBM comprehensive utilization technology are proposed

Multiple-Frequency Controlled Synchronization of Two Homodromy Eccentric Rotors in a Vibratory System

Multifrequency controlled synchronization of two homodromy eccentric rotors is investigated. The vibrating screen with two rotors is a typical underactuated system. So, the model of the vibrating screen is converted to a synchronization motion problem. Firstly, the mechanical-electromagnetic coupling dynamical model of the vibrating system is established. And then the fuzzy PID method is used for the two motors which are based on the master-slave control strategy. The slave motor uses the method of the phase ratio to trace the master motor and achieve the synchronous motion. Through the simulation, the two rotors cannot reach the state of multifrequency self-synchronization. And, then, it is realized by multifrequency controlled synchronization. The article presents the motion trails of the vibrating system between one and two times and realizes the zero phase difference after each period. Finally, some experiments are used to verify the accuracy and effectiveness of the conclusion in the simulation and analysis of the feature of the movement tracks

Shark Skin—An Inspiration for the Development of a Novel and Simple Biomimetic Turbulent Drag Reduction Topology

In this study, a novel but simple biomimetic turbulent drag reduction topology is proposed, inspired by the special structure of shark skin. Two effective, shark skin-inspired, ribletted surfaces were designed, their topologies were optimized, and their excellent drag reduction performances were verified by large eddy simulation. The designed riblets showed higher turbulent drag reduction behavior, e.g., 21.45% at Re = 40,459, compared with other experimental and simulated reports. The effects of the riblets on the behavior of the fluid flow in pipes are discussed, as well as the mechanisms of fluid drag in turbulent flow and riblet drag reduction. Riblets of various dimensions were analyzed and the nature of fluid flow over the effective shark skin surface is illustrated. By setting up the effective ribletted surface on structure’s surface, the shark skin-inspired, biomimetic, ribletted surface effectively reduced friction resistance without external energy support. This method is therefore regarded as the most promising drag reduction technique

On the Synchronization of Two Eccentric Rotors with Common Rotational Axis: Theory and Experiment

We study synchronization of two eccentric rotors (ERs) with common rotational axis in the vibration system of the far-resonant spatial motion. We deduce the dimensionless coupling equation of two ERs with applying the average method of small parameters. We convert the synchronization problem into the existence and stability of solving the zero solutions for the dimensionless coupling equations. By introducing the synchronization torque and the difference between the residual torques of two motors, we obtain the synchronization condition that two ERs achieve the synchronized motion. We derive the stability condition of the synchronized motion, which satisfies Routh-Hurwitz criterion. We discuss numerically the choosing motion feature of the vibration system, which indicates that the vibration system has two steady motion modes. The synchronization torque forces the phase difference to approach π when the structural parameters of the vibration system satisfy the condition of the spatial cone motion, and the synchronization torque drives the phase difference to approach zero when those satisfy the condition of the spatial circle motion. Finally, through the comparison and analysis of experimental data, the structural parameters of the vibration system satisfying the above two conditions can guarantee the synchronization stability for two ERs