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정의봉,유완석,박정근 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.8
The diesel engine is often a serious excitation source in ships. Both the varying cylinder gas forces and the reciprocating and rotating mass forces associated with the crank and the connecting rod mechanism produce ample possibilities for excitation of the engine structure itself, the shafting, the surrounding substructures as well as the hull girder. This paper presents a guide for optimization of excitation forces produced by the marine propulsion 2-stroke diesel engine. The computational program for predicting the excitation forces is developed and applied to 2-stroke in-line engines. The object function is defined as the work done by every cylinder excitation force which is related to the mode shape of the diesel engine system, especially in the torsional vibration of the shafting. As a practical application of the presented method. the crank angle of 7 cylinder 2-stroke engine is optimized to reduce torsional vibration stresses on the shafting. Compared with the regular firing angle, about 60 % of the 4th order torsional vibratory stress on the propeller shaft can be reduced by optimizing the crank angle irregularly. The usefulness of the presented optimization method is confirmed by the measurements.
박준희(Park, Joon Hee),도쑤웬푸(Do, Xuan Phu),구오흥(Nguyen, Quoc Hung),강옥현(Kang, Ok Hyun),최승복(Choi, Seung-Bok) 한국소음진동공학회 2013 한국소음진동공학회 논문집 Vol.23 No.5
This paper presents optimal design procedures of mount based on a magnetorheological(MR) fluid to isolate the vibration in heavy diesel engine system. At first, frequency response and force-displacement transmissibility methods are used to get required damping force that is necessary for effective vibration isolation. From this result, a new type of high damping force engine mount is proposed and the governing equation of Bingham plastic behavior of MR fluid in flow path is mathematically derived under cylindrical coordinates. Finally, parametric design optimization featuring finite element is performed using ANSYS software to get the required damping force in MR mount system which can be used to reduce engine vibration. Damping force of the MR mount is then determined as an objective function in this analysis based on ANSYS. Furthermore, Magnetic analysis is then applied in this process.
마운트편심과 기진력편심이 함정탑재장비의 진동특성에 미치는 영향
이현엽,이충현,유원선 대한조선학회 2017 大韓造船學會 論文集 Vol.54 No.6
A rigid body supported by 4 linear springs has been analyzed, to investigate the effects of eccentricities on the vibration responses for naval shipboard equipments supported by elastic mounts. Considering mount eccentricity (the location of the center of spring reaction forces relative to the mass center) and excitation force eccentricity (the location of the center of the excitation force relative to the mass center), the vibration phenomena have been formulated and discussed. Also, the effects of the eccentricities have been evaluated and discussed for the elastically mounted naval shipboard equipment. Results show that the mount eccentricity has little effects on the structure-borne noise above the natural frequency of the system, however the excitation force eccentricity has significant effects all over the frequency range.
박정근,정의봉,서영수 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.2
The excitation forces from the periodical firing pressure in cylinder and the rotating crank mechanism cause lots of vibration problems in diesel engines. In this Paper. the computational program for predicting the excitation force is developed and applied to 4-stroke In-line engines. The crank angle is also optimized to reduce the first and second order moment produced by engines. Compared to the conventional uniform crank angle, about 70 % of the first order horizontal and vertical moment can be reduced by re-designing the crank angle non-uniformly.
박준희(Joon Hee Park),도쑤웬푸(Do Xuan Phu),구오흥(Nguyen Quoc Hung),강옥현(Ok Hyun Kang),최승복(Seung-Bok Choi) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
This paper presents optimal design procedures of mount based on a magnetorheological (MR) fluid to isolate the vibration in heavy diesel engine system. At first, frequency response and forcedisplacement transmissibility methods are used to get required damping force that is necessary for effective vibration isolation. From this result, a new type of high damping force engine mount is proposed and the governing equation of Bingham plastic behavior of MR fluid in flow path is mathematically derived under cylindrical coordinates. Finally, parametric design optimization featuring finite element is performed using ANSYS software to get the required damping force in MR mount system which can be used to reduce engine vibration. Damping force of the MR mount is then determined as an objective function in this analysis based on ANSYS. Furthermore, Magnetic analysis is then applied in this process.
김성종(Sungjong Kim),이상권(Sangkwon Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The objective of this paper is to estimate the excitation force at the mount brackets of powertrain. The powertrain excitation force on mount bracket is used for the prediction of the vehicle interior noise induced by hybrid transfer path analysis. In order to do this research, a powertrain geometry model must be based on the real powertrain model, and its finite element model is made by meshing software. The multibody dyncamic model is based on the EMA(experimental modal analysis) and FEA(finite element analysis). The experimental modal analysis and operational deflection shape for powertrain are experimentally implemented. After the MBD model is assembled with vibration characteristic properties both EMA and FEA result. Then, the MBD model of ADAMS resemble the vibrational property of real powertrain. Consequently. ADAMS result of powertrain excitation forece is compared and verified with measured values.
주파수응답함수의 부분구조합성 법을 이용한 차 실내소음 예측
허덕재,박태원 한국소음진동공학회 2001 한국소음진동공학회 논문집 Vol.11 No.4
This paper presents the simulation methodology of the interior noise of vehicle using the frequency response function based hybrid modeling of the system which consists of multi-subsystem models obtained by the test or analysis. The complex systems such as a trimmed body of high modal density and a powertrain were modeled by using experimental data, and a sub-frame of a vehicle of low modal density was modeled by finite element data. Modeling of the whole system was executed and validated in the two stages. The first stave is combining the trimmed body and the sub-frame, and the second stage is attaching the powertrain, which is a exciting source, to the combined model of the first stage. The input force to the system was modeled as an equivalent force in the virtual space, which was obtained from impedance method using the FRFs of the powertrain and the responses. The interior noise predicted by the proposed method was very close to the direct measurement, which showed feasibility of the proposed modeling procedure. Since the methodology is easily applied to both the transfer path analysis of structure-borne noise and the analysis of noise contribution of a sub-system, it is expected to be a strong tool for design change of a vehicle in the earlier stare.
홍진숙,신구균,김상윤 한국소음진동공학회 2001 소음 진동 Vol.11 No.2
It is essential to analyze structural vibrations due to turbulent wall pressure fluctuations over a body surface which moves through a fluid, because the vibrations can be a severe source of noise affecting to passengers in airplanes and SONAR performance. Generally, this kind of problems have been solved for very simplified models, e.g. plates, which can be applied to the wavenumber domain analysis. In this paper, a finite element modeling of the walt pressure fluctuations is investigated, which can be applied to those over arbitrary smooth surfaces. It is found that the modeled wall pressure fluctuation at nodes becomes uncorrelated at higher frequencies and at lower flow speeds, and the response is over-estimated due to the aliased power. Then the frequency range available for uncorrelated loading model and two power correction schemes are presented.