Abstract
During the rice-threshing process, straws always attached to a threshing cylinder and induced vibration and modal variation. In this paper, the constraint and threshing modals of the threshing cylinder were tested under idling and load conditions, and the causes of vibration and modal variation were explained. Based on the constraint and modal of the threshing cylinder, the vibration amplitudes and frequencies undergoing rice threshing were tested and analyzed. Results showed that mass of straws decreased gradually with the separation of rice grains and straws. And there was a nonuniform change in the circumferential resistance of the threshing cylinder. The fluctuating torque, speed, and frequencies during threshing process would cause vibration of the threshing cylinder. During rice-threshing process, the other natural frequencies were greater than the excitation frequency. With the accumulation of a large amount of straws, the threshing modal frequencies of the tangential threshing cylinder increased. The threshing bars caused vibration of the tangential threshing cylinder in the left and right direction mainly at two frequencies. At idling state of no-load, the vibration frequency 42.97 Hz of the tangential threshing cylinder in X direction was close to the constraint modal frequency 41.58 Hz. The eccentric load caused the excitation frequency to increase during the rice-threshing process. The vibration frequency was also closely related to the threshing modal. The tangential threshing cylinder with low vibration characteristics could be designed by using the eccentric vibration characteristics during the threshing process.
Highlights
Rotating cylinders similar to the rice-threshing cylinder have applications in many industrial machineries, such as blenders, impregnators, coaters, granulators, and cement mixers [13, 14]
Koynov et al measured the axial dispersion coefficient of powder in a rotating cylinder, and particle motions in rotating cylinder were quantified as a function of process [16]. e vibration characteristics of the engine rotor and hydromechanical rotor in the disturbed state have been studied above. e external excitation has an important influence on the vibration characteristics of the rotor
By analyzing the dynamic characteristics of the rotating rotor, the reliability and performance of the rotor and whole machine were greatly improved [17]. e rice-threshing cylinder has typical vibration characteristics during the ricethreshing process. e vibration begins at the beginning of threshing process and disappears with the end of threshing process
Summary
2.1. reshing Structure and Eccentric Load in reshing Process. e threshing cylinder can thresh rice and separate grain from the concave sieve. e combine harvester with multiple threshing cylinders is a mainstream type. En, rice straws attached to the tangential threshing cylinder formed the eccentric mass. Another type was the threshing modal, which was constrained by the both ends of the drive shaft and constrained by the straws in threshing process.
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