서지주요정보
유체기계 흡/배기 소음원의 시변 및 비선형 특성에 관한 연구 = A study on the time-varying and nonlinear source characteristics of intake and exhaust systems in fluid machines
서명 / 저자 유체기계 흡/배기 소음원의 시변 및 비선형 특성에 관한 연구 = A study on the time-varying and nonlinear source characteristics of intake and exhaust systems in fluid machines / 장승호.
저자명 장승호 ; Jang, Seung-Ho
발행사항 [대전 : 한국과학기술원, 2002].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8013324

소장위치/청구기호

학술문화관(문화관) 보존서고

DME 02034

휴대폰 전송

도서상태

이용가능

대출가능

반납예정일

초록정보

The one-port acoustical source in a duct system can be characterized by the source impedance and strength using the linear frequency-domain modeling. It is known that the direct method yields different results from the indirect method, in other words, load method, in measuring the source parameters of many fluid machines. Although the real part of the source impedance is expected to be non-negative, the indirect method comes up with a negative source resistance at some frequencies. In the first part, this study is focused on the effect of the time-varying nature of fluid machines on the output results of two typical measurement methods: direct and indirect methods. For this purpose, a simplified fluid machine consisting of a reservoir, a valve, and an exhaust pipe is considered as representing a typical periodic, time-varying system and the measurement situations are simulated using the method of characteristics. The equivalent electro-acoustic circuits for such simulations are also analyzed by considering the system as having a linear time-variant source. It is found that the results from the indirect method are quite sensitive to the change of cylinder pressure and/or valve profile, in contrast to those from the direct method. In the indirect method, the source admittance turns out to be predominantly dependent on the valve admittance at the calculation frequency as well as the valve and load admittances at other frequencies. In the direct method, however, the source resistance is always positive and the source admittance depends mainly upon the zeroth order of valve admittance. In the second part of this study, the source model and measurement techniques are modified in order to evaluate the effect due to nonlinear and periodically time-varying source character as well as the linear property of the reflectivity of in-duct fluid machine source. With the a priori known kinematical information of the source, the types of nonlinear time-variant terms can be presumed by a simple physical model, in which there is practically no restriction on the form of the model. The concept of source impedance can be extendable by introducing the linear frequency response function for each nonlinear or time-variant component. Extending the conventional method and adapting the reverse MI/SO technique, it is possible to develop a direct method that can deal with the nonlinear time-variant source parameters. The proposed direct method has a novel feature that there is no restriction on the probability or spectral natures of the excited sound pressure data. In addition, the indirect method for dealing with the nonlinear time-variant source parameters is also suggested: different loads are applied to the same source and the equations are formulated, which can be solved simultaneously to extract the source parameters. The proposed direct and load methods can utilize the same input data with the conventional linear methods. The present methods are verified by the simulated measurements for simplified fluid machines and applied to measure the nonlinear time-variant characteristics of the blower and compressor sources. It is thought that the proposed method in this study would be useful in predicting the insertion loss or the radiated sound level from intake or exhaust systems of fluid machines.

서지기타정보

서지기타정보
청구기호 {DME 02034
형태사항 xvi, 167 p. : 삽도 ; 26 cm
언어 한국어
일반주기 부록 : A,다부하법에서의 부하선택. - B, 시변 체적을 가지는 음원에 대한 전기-음향 상사 해석
저자명의 영문표기 : Seung-Ho Jang
지도교수의 한글표기 : 이정권
지도교수의 영문표기 : Jeong-Guon Ih
수록잡지명 : "On the selection of loads in the multi-load method for measuring the acoustic source parameters of duct systems". Journal of the acoustical society of america
학위논문 학위논문(박사) - 한국과학기술원 : 기계공학전공,
서지주기 참고문헌 : p. 132-135
주제 유체기계
음원
시변
비선형
덕트
acoustics
source
fluid machine
time-varying
nonlinear
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