• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1244-1251
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• 2006

The objective of this paper is to get excitation forces of the engine at each of the brackets for the prediction of the vehicle interior noise by the powertrain. A powertrain geometry model is produced by CATIA and its FE model is made by MSC/Patran. A vibration mode analysis and a running mode analysis are experimentally implemented. After getting a satisfied MAC value by doing a correlation about a measured mode analysis value and analyzed value through MSC/Nastran software, all components are assembled through MSC/ADAMS software which is a dynamic analysis tool. We can predict the vibration of brackets which is the last points to occur the force of the engine combustion by analyzing the combustion force produced by engine mechanism.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.678-683
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• 1998

Combustion instability by thermoacoustic feedback incite strong low frequency noise and vibration which damage the system and provoke the environmental problems. Therefore, it is necessary to control the thermoacoustic oscillation. In the way of controlling the instability, active control method using adaptive algorithm is applied. In this study, active noise control method using anti-sound technique is selected, whose principle is cancelling the noise with the addition of opposite phase sound. At first, simulation is performed to confirm the stability of controller, and after that control of combustion instability is carried out to get cancellation of 20-30dB SPL.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.492-497
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• 1998

Thermoacoustic oscillation is a significant problem in cylindrical-type combustors such as common internal combustion engines, industrial furnaces, gas turbine, etc. This kind of low frequency oscillation can give rise to serious troubles such as the destruction of system or producing of a strong noise. Accurate numerical simulation of thermoacoustic phenomena is a complex and challenging problem. Especially, considering the reaction of mixture intensifies the difficulty of analysis. Like as other simulations of the aerodynamics and aeroacoustics, direct computation of thermoacoustic phenomena requires that the Navier-Stokes equations be solved using accurate numerical differentiation and time-marching schemes, with non-reflecting boundary conditions. In this study,, numerical approach aims at qualitative analysis and efficient prediction of problem, not at the development of an accurate scheme. Overally speaking, numerical prediction is reasonably matched with experimental result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.654-657
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• 2014

In this paper, we study the analytical method to predict the excitation forces for the engine system. The engine system on the construction equipment is one of the important power sources, and the characteristics of the engine decide the performance of noise and vibration for the equipment. We predict the excitation forces using the geometrical data of the crank system and the combustion pressure in the cylinder. The excited forces are represented by the torque fluctuation above the center of the crank shaft.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.322-330
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• 2020

This study investigates the far-field noise from three Falcon 9 vehicle launches from Vandenberg Air Force Base, CA, USA, as measured from the same location within the nearby community of Lompoc. The overall sound pressure levels for the three launches are shown to be similar, but some differences in the early launch period are thought to be weather-related. The peak directivity angle in overall level is approximately 65 deg, which is consistent with horizontally-fired, static rocket data. For the third launch, waveforms and spectra are analyzed for different events during the launch sequence. The measured spectral bandwidth decreases with time, but spectral levels remain above the ambient noise throughout the main-engine firing. Additionally, late-launch phenomena observed in the data appear to be correlated with main-engine cutoff and second-stage engine start.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.353-358
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• 2009

For the successful development of 75 tonf class liquid rocket engine, a plenty of tests on each engine component has to be performed and this is equally true for a combustor. However the test facility which is in operation at Korea Aerospace Research Institute lacks its capacity to perform fire tests of a 75 tonf class combustor at its nominal thrust. Since the test facility has to be ready prior to the start of development tests, it is very urgent to establish the test facility. The preliminary design of a test facility for a 75 tonf class combustor which was performed according to the urgent necessity is described in the paper.

• Journal of KSNVE
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• v.8 no.2
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• pp.239-250
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• 1998

Traditionally, intake noise from internal combustion engine has not recevied much attention compared to exhaust noise. But nowadays, intake noise is a major contributing factor to automotive passenger compartment noise levels. The main objective of this paper is to identify the mechanism of generation, propagation and radiation of the intake noise. With a simplest geometric model, one of the main noise sources for the intake stroke is found to be the pressure surge, which is generated after intake valve closing. The pressure surge, which has the nonlinear acoustic behavior, propagates and radiates with relatively large amplitude. In this paper, unsteady compressible Navier-Stokes equations are employed for the intake stroke of axisymmetric model having a single moving cylinder and a single moving intake valve. To simulate the periodic motion of the piston and the valve, unsteady deforming mesh algorithm is employed and Thompson's non-reflecting boundary condition is applied to the radiation field. In order to resolve the small amplitude waves at the radiation field, essentially non-oscillatory(ENO) schemes with an artificial compression method (ACM) are used.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.91-104
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• 2002

Jet noise of propulsion systems is major source of acoustic loads of launch vehicles and sounding rockets. The investigation of characteristics of jet noise is inevitable for successful missions. In this paper, the mechanism of generation of acoustic loads due to jet noise was investigated. The major parameters that change the characteristics of acoustic loads were also suggested so that effects of the parameters could be investigated. The temporal and spatial characteristics of acoustic loads of KSR-III was demonstrated. The results show that the maximum value of the acoustic loads is found in the octave bands whose center frequencies are 250 Hz and 500 Hz. Finally, the methods and the facilities for the further investigation of acoustic loads were proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.19-19
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• 1998

최근 화학, 연소, 동력, 제철 등의 각종 플랜트에서 조업압력이 고압화되어 가고 있으며, 이에 수반하여 배관계를 통하는 고압가스 유동에 관한 연구가 활발하게 진행되고 있다. 배관계를 통하는 고압가스의 유동에 있어서 유량의 적절한 제어, 유동에 의하여 야기되는 배관계의 소음·진동, 그리고 배기가스의 적절한 처리법 등은 공학적으로 매우 중요한 문제로 알려져 왔다. 일반적으로 정상운전을 하는 플랜트에서 고압 배기가스의 문제는 배기가스 Expander에 의하여 에너지를 회수하는 방법이 생각될 수 있으나, 실제 공업현장에서는 배기가스를 안전하고, 또 소음·진동을 발생시키지 않도록 적절하게 처리하는 것이 매우 중요한 기술적 과제로 남아 있다. 일반적으로 배기가스의 압력이 임계압력(critical pressure) 이상으로 되는 경우(실제 대부분의 플랜트에서 배기가스의 압력은 임계압력보다 매우 높다), 배관계 내부에서 충격파(shock-wave)가 발생하여 난류와동 혹은 난류경계층과 간섭하게 됨으로써 강력한 공기역학적 소음이나 진동을 발생시키게 된다. 이와 같은 소음·진동에 대한 대책으로는 현재 가스배출부에 감압밸브를 직렬로 설치하거나, 유로에 다공판(porous plates)들을 삽입하여 감압과정을 공간적으로 분산시킴으로써, 충격파가 발생하지 않도록 하는 방법을 주로 채택하고 있다. 그러나 이러한 방법을 적용하는 경우 배기가스 유동에 대한 유량의 제어기능이 저하되는 문제가 발생한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.507-514
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• 2009

Large eddy simulation code was developed to predict the turbulent flows over backward-facing steps including a recirculating flow phenomena. Localized dynamic ksgs-equation model was employed as a LES subgrid model and the LES solver was implemented on parallel computer consisting of 16 processors to reduce computational costs. The results of laminar flow showed qualitative and quantitative agreements between current simulations and experimental results availablein literatures. The simulation of the turbulent flows also yielded reasonable results. From these results, it can be expected that developed LES code will be very useful to analyze the combustion in stabilities and noise of a practical combustor in the future.