艦艇用 分離板型 遠心分離機의 彈性支持 設計 및 傳達騷音 制御에 관한 硏究

Abstract

Equipment mounted on naval vessel or submarine must satisfy the special performance (internal noise, environmental vibration, underwater radiation noise, etc.) required before loading. As for newly built ship-based equipment, the effect on the Air Born Noise (ABN) and the Structure-Borne Noise (SBN) along with the development of detection radar and sonic detection technology is being strictly considered. In order to satisfy these conditions, resilient mounting systems are widely applied. The abnormal noise generated during the test repeats increasing and decreasing. A form of abnormal noise with such periodicity is generally known as a form of noise caused by a beat phenomenon. Whether it is beat phenomenon, which is the cause of the noise generated by the disc stack centrifuge, and the frequency of the beat occurrence were confirmed by vibration measurement. In the case of designing a rotating machine such as a disc stack centrifuge, a method to prevent such a beat phenomenon was proposed. In this paper, the design method of resilient mounting systems, evaluation, and analysis to be considered for mounting equipment on naval ship was conducted. Also, the control method for abnormal noise discovered in the evaluation process was studied. A single mounting system and a double mounting system were designed by disc stack centrifuge, and their natural frequencies were analyzed and verified using a commercial FEM analysis program. The performance evaluation of resilient mounts, which are important design factors in the mounting system, was presented as an experimental method. This test proposed a method to evaluate and apply performance based on the difference in acceleration between the top and bottom of the mount in the SBN measurement frequency range. It was confirmed that, in the case of a disc stack centrifuge with a double mounting system, the satisfaction of the SBN standard may vary depending on the resilient mount arrangement. In the evaluation of the resilient mount performance, the resilient mount having a relatively uniform vibration isolation performance over the entire frequency band of SBN satisfies the criteria. The reason for using a double mounting system rather than a single mounting system was confirmed through SBN and ABN measurement. It was difficult to satisfy the SBN & ABN criteria for a disc stack centrifuge with only a single mounting system, and the double mounting system sufficiently satisfies the SBN & ABN criteria. The abnormal noise that periodically increased and decreased from the disc stack centrifuge discovered during the test process was solved by approaching it as a beat phenomenon. Although the noise generated by the disc stack centrifuge did not exceed the standards for SBN and ABN, it should be reduced or eliminated in consideration of the emotional aspects of crew members operating the equipment. As a result of vibration measurement for abnormal noise, the beat phenomenon was the cause of the abnormal noise, and two adjacent frequencies were found that caused the beat phenomenon. It was confirmed that one frequency was 6 times the number of rotations on the horizontal axis and the other frequency was 1 times the number of revolutions on the vertical axis. A method was devised to reduce the abnormal noise of disk stack centrifuges and observed changes after application. The abnormal noise was completely eliminated by widening the interval between the two frequencies that caused the beat phenomenon, which is the cause of the abnormal noise. It was confirmed that there was no significant difference between the vibration values measured by the equipment in the state in which the abnormal noise was generated and the state in which the abnormal noise was removed. When it is necessary to change the rotation speed designed to eliminate the beat phenomenon, the stability evaluation of the rotating machine and the evaluation method for the change caused by the rotation speed change using the commercial finite element analysis program were reviewed and confirmed.

KEY WORDS : Resilient mount (탄성 마운트); Structure-borne noise (SBN: 고체전달소음); Air-borne noise (ABN: 공기전달소음); Disc stack centrifuge (분리판형 원심분리기); Beat (맥놀이 현상)