Analysis on vibration characteristics of throwing impeller of stalk impeller blower

Abstract: An impeller blower mainly consists of throwing impeller, shell, discharge tube, etc. When the impeller blower is working, the material is transported by mechanical centrifugal force and airflow which are generated by a high-speed rotating impeller. As the core component of the impeller blower, the impeller have to bear the comprehensive effect of the centrifugal force, the pressure of high-speed air flow inside the impeller blower and impeller gravity, which may produce violent vibration. The vibration will not only accelerate the throwing blade's fatigue fracture and affect its service lifetime but also produce environmental noise. In the meantime, if the excitation frequency is closed to some-order natural frequency of the throwing impeller, the whole device would produce resonance which seriously affects the work performance, the service life and reliability of the impeller blower. Therefore, in order to improve the working performance of impeller blower and avoid the resonance, it is quite important to analyze the vibration characteristics of the throwing impeller. In this paper, the modal frequency and vibration types of the first 12-order free modal and constraint modal were calculated using the finite element analysis software ABAQUS. In order to verify the accuracy of numerical calculation, a modal test of the impeller was carried out using the PSV-500-3D Scanning Vibrometer, which showed the maximum error of numerical modal frequencies and experimental modal frequencies was 8.5%, the vibration types were basically the same, and the numerical calculation results were reliable. Based on analyzing the characteristics of external excitation frequency, the structural parameters such as blade number, blade thickness, whether reinforcement were simulated and compared. The results show that: 1) Prestress increased each order natural frequency of the impeller, and only the first and the second order frequency increased largely while other frequencies increased a little. Prestress has no impact on the vibration type of the impeller. 2) When the speed of impeller was 1 500 r/min, the deviation of excitation frequency and the first order natural frequency of the impeller with 3 blades was 57% and the resonance of impeller most unlikely took place. The deviation of excitation frequency and the first order natural frequency of the impeller with 4 blades was 15.9% and the resonance of impeller also couldn't take place. The excitation frequency deviated from the first order and second order natural frequency of the impeller with 5 blades by 13%, which most likely caused the resonance of impeller. 3) The lower natural frequencies of the impeller decreased and the higher natural frequencies increased with the blade thickness increasing. The natural frequency of the impeller with 4 mm thick blade deviated from the excitation frequency by 23% and the resonance of impeller most unlikely took place, while the natural frequency of the impeller with 5 mm thick blade deviated from the excitation frequency by 15.9% and the resonance of impeller also unlikely took place. But the impeller with 6 mm thick blade had low first order natural frequency and deviated from the high excitation frequency by 13%, which most likely caused the resonance of impeller. 4) The impeller with stiffeners could effectively avoid the vibration frequency, improve the dynamic performance and avoid the resonance.