Structure Design and Experimental Study on Ultrasonic Levitation Bearing Which Support Shaft in Two Directions
|Course||Mechanical Design and Theory|
|Keywords||Piezoelectric transducer Bearing Support in two directions Ultrasonic levitation|
This paper is based on the project of“the National Natural Science Foundation research of ultrasonic technology for shaft levitation in high-speed flywheel energy storage system”, The project propose using ultrasonic vibration bearing technology for shaft levitation in the flywheel energy storage system, to levitate the flywheel and shaft through High-frequency vibration, to reduce friction, achieve greater speed, lower energy consumption, improve the flywheel energy storage efficiency. This paper begined with analysis the theory of piezoelectric and ultrasonic, then designed and built the testing system of ultrasonic vibration bearings which support the in two directions, and tested it, testing showed that shaft was levitated in biggish speed and lower friction with ultrasonic vibration bearings can be achieved .The paper is composed of five chapters, the following is the main content:Chapter one: IntroductionThe development of bearing was introduced in briefly, cited the types of bearings which emerge recently; analyzed the characteristics of ultrasonic and it’s applications, base on that, put an emphasis on the ultrasonic levitation technology, summarized the domestic and international research of ultrasonic levitation technology , then raised the issue of this paper :research on the levitation technology of the bidirectional supported ultrasonic bearing in biggish speed and pointed out the main work which this paper will finish. Chapter two: The basic theory of piezoelectric ceramicsThis chapter based on the the basic theory of piezoelectric, introduced the basic concepts of piezoelectric effect and reverse piezoelectric effect; then deduced four piezoelectric equation base on the mechanical and electrical knowledge; discussed dozens of common piezoelectric material which are known by current, and focus on the most widely used piezoelectric materials—Piezoelectric Ceramics’discovery and development, analysed the polarization process of piezoelectric ceramic, discussed key performance parameters of piezoelectric ceramics; finally, researched the four resonant vibration characteristics of the piezoelectric oscillator made of piezoelectric ceramic, give the theoretical support for ultrasonic piezoelectric transducer which used in ultrasonic levitation bearing which support the shaft in two directions.Chapter there: Structure design and testing of the piezoelectric transducer used in ultrasonic levitation bearing which support the shaft in two directionsThis chapter analysed the common types of piezoelectric transducer, base on that, proposed the structure of the transducer used in this paper—piezoelectric transducer fastening by bolt,and made the outline to the main performance characteristics of the piezoelectric transducer; then designed the concrete structure of piezoelectricity ultrasonic transducer, based on the related knowledgeof vibration mechanics and acoustics, calculate the main size of the transducer after simplified the structure, afterwards using ANSYS to analyse the vibration situation of piezoelectric transducer, get longitudinal vibration chart, calculated the resonance frequency, and made contrast with the design frequency; according to vibration analysis result, after revised the partial designs size, manufactured two prototype of piezoelectric ultrasonic transducer; finally, with the manufactured transducer, made the impedance, the resonance frequency and the oscillation amplitude test, and did the experimental study to the relations between the levitation clearance and the load; test showed that, the heavier of the load, the smaller of the levitation clearance . Chapter four: Structure design and experimental study of test system of ultrasonic levitation bearing which support the shaft in two directionsThere are some difference compares with ultrasonic levitation bearing which support the shaft in lengthways or radial direction, the ultrasonic vibration bearing test system designed by the author can support the shaft in two directions, and achieved the goal: make the shaft levitate in biggish speed. the ultrasonic vibration has the supersonic radiation pressure, the pressure may support the shaft, with specifical transducer structure, divide the radiation pressure into two directions, make the shaft levitateing, this is the working principle of ultrasonic levitation bearing which support the shaft in two directions. after the explanations of the theorey of principle and illustrations, made the concrete design to the ultrasonic levitation bearing testing system, manufactured and assembly one prototype, using the prototype, did levitation phenomenon experiment and levitation clearance experiment, found that the shaft can be levitated within one scope of levitation clearance; base on this, tested the maximum speed in different levitation clearance, testing show that, the smaller the levitation clearance, the higher speed shaft can rotate; tested the friction torque of the ultrasonic levitation bearing, the results proved that, the friction torque is very small between the ultrasonic suspension bearing and the shaft; finally, according to the manufacture and assembly of the parts of the system, analysed the factors which might affect the experimental results.Chapter five: Conclusions and OutlookSummaried the research work of this paper, combining experimental results, presented the conclusion of the study of this paper: the ultrasonic levitation bearing which support the shaft in two directions can levitate the shaft which rotates in biggish speed and lower friction, it has use value .base on the testing system of this paper, put forward proposals and ideas, which build up a base for following study of ultrasonic levitation bearing.