• 한국정밀공학회지
• /
• 제33권11호
• /
• pp.927-935
• /
• 2016

A gerotor is suitable for miniature manufacturing because it has a high discharge per cycle and a simple structure, while also being widely used as lubrication oil of engines and the hydraulic source of automatic transmission. In the automobile industry, it has been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency through optimal gerotor design. In this study, to obtain an optimal gerotor with an ellipse-elliptical involute-ellipse combined lobe shape, an automatic program was developed for calculating performance parameters and drawing a gerotor profile. An oil pump was assembled with the optimal gerotor together with the port used at the actual field and CFD analysis was performed on this assembly using Ansys-CFX. A performance test for the oil pump was carried out and showed good agreement with the results obtained from the theoretical analysis and the CFD analysis.

• 한국정밀공학회지
• /
• 제34권4호
• /
• pp.287-292
• /
• 2017

A gas turbine is the main equipment used in a combined heat and power plant. It generates a high sound pressure noise level. To reduce the noise level, an enclosure is installed around the turbine. The sound insulation performance of the enclosure affects the amount of external noise reduction. In this study, a sound transmission loss analysis is performed using the boundary element method to predict sound insulation performance according to the numbers and shapes of the supporter. Radiated noise analysis is also performed for the main external points of the enclosure using ray-acoustics. The results of these analyses are presented and a design plan is proposed that reduces the sound pressure noise level of the enclosure.

• Tribology and Lubricants
• /
• 제23권5호
• /
• pp.234-239
• /
• 2007

Recently one of the automobile customer's greatest concerns is quietness in a vehicle along with various functional requirements such as comfort, stability, mobility etc. Therefore car makers place more weight on vehicle noise. Especially, in the case of diesel engine, as the noise level of engine becomes more silent by the development of engineering technology. The noise of alternator with vacuum pump has been able to be noticed enough becoming an issue on vehicles. In this study vacuum pump noise on alternator was identified andclassified into five types. DOE was applied to induce the statistical analysis result to reduce the vacuum pump noise. It was done by subjective listening. Design and statistical analysis are done with Minitab software. This work provides dominant elements of vacuum pump noise on alternator and can be the basis of furture studies.

• 화약ㆍ발파
• /
• 제34권3호
• /
• pp.21-26
• /
• 2016

도심 발파작업에서 주거지에 근접하여 발파작업을 수행하는 경우, 발파공사시 발생하는 진동 및 소음을 최대한 저감시키기 위해 일회 발파규모를 최소화시켜 공사를 진행하게 된다. 이런 경우 발파횟수의 증가로 인하여 오히려 민원이 증가하여 예정된 공사기간을 맞추지 못하는 경우가 발생하고 있다. 본 사례는 도심 아파트 건설 현장으로서 일반뇌관 사용할 경우 일일 목표 생산량을 충족시키기 위하여 발파횟수를 증가시켜야 하는 단점을 극복하고자, 발파횟수 증가 없이도 일일 발파물량을 증가시킬 수 있는 전자뇌관을 활용한 분산장약 공법을 적용함으로서 효과적으로 민원 감소와 공사기간을 단축시킨 시공사례이다.

• 정보저장시스템학회:학술대회논문집
• /
• 정보저장시스템학회 2005년도 추계학술대회 논문집
• /
• pp.197-202
• /
• 2005

Current Optical Disk drive is dominating high share gradually in information storage device market through development of great skill. These technologies can achieve not only improvement of transmission speed but also elevation of recording/reproduction technology. However, these present state cause not only the increase of vibration in structural viewpoint but also problem of serious noise while the ODD becomes high speed/high performance. Specially, air-born noise is being bigger than structural-born noise as disk rotation speed increases gradually. The object of this research is that reduce the air-born noise in optical disk drive by reducing a quantity of flow by using a miniaturized muffler. The micro muffler is a miniaturized muffler. The muffler is used widely by solution to reduce air-born noise which is generated by flow. According to frequency band of the noise source, it can be applied by muffler of various forms. In this research, we examined the noise characteristics of the micro muffler and applied it by noise reduction solution of the ODD. It could get an excellent noise reduction in high frequency band by using the micro muffler than the opened case through the decrease of an inner flow. But it could not get a noise reduction in low frequency band through the decrease of an inner flow.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집
• /
• pp.659-666
• /
• 2009

As the density and height of the buildings nearby subway lines get higher, the unprecedented residents' appeals for noise are on the rise. Furthermore, in accordance with the revision of enforcement regulations on the Noise and Vibration Control Act, the night time noise standards have been reinforced by 5dB effective on January 1st 2010 and the appropriate measures shall be taken accordingly. For the settlement of the public grievances against noise and vibration generated on tracks in at-grade and elevated section, the installation of continuously-welded-rail, rail lubrication system, improved fastening system and higher noise barrier is currently executed. Nevertheless, the noise and vibration levels in some areas are still exceeding the limits required in the regulation. Among the measures, an installation of higher noise barrier or noise tunnel seems to be the most effective way; however, it has limitations owing to the structural stability of existing elevated structures. The paper in consideration of the local conditions and foreign practices discusses the installation of fairing system under the train body as an noise insulation panel in order to reduce the rolling noise and under-carriage noise. Based on the result of this study, a performance verification test during actual train operation is in progress for further study.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.2163-2172
• /
• 2008

The noise to be considered as the most important in railway systems is the noise generated from the wheel/rail interaction. Such noise can be divided into three categories; that is, the rolling noise, the squeal noise and the wheel howling noise. Especially in metro systems, this type of noise has been considered seriously in recent years, and the diversified studies on the mechanism and solutions of such noise are in progress by many railways and researching bodies. In this study, a specially designed wheel absorber is installed in the wheel, and FEM analysis and laboratory tests are executed for the two cases, i.e. with wheel absorber and without wheel absorber, to check the effect of the wheel absorber in noise reduction. For the FEM analysis, the frequency response functions for respective cases are compared. And, for the laboratory test, following four cases are tested and compared; that is, i) with wheel only, ii) installation of ring damper only, iii) installation of damping material and cover, iv) installation of complete absorber system.

• 한국화재소방학회논문지
• /
• 제25권6호
• /
• pp.178-183
• /
• 2011

초고층 건물의 승강기는 혹한기에 연돌효과에 의한 차압 때문에 고층부의 승강기 문틈에서 소음을 유발하고, 1층에서 승강기 문 개폐에 영향을 줄 정도의 강한 압력이 발생하며, 화재시에는 건물 내에 연기를 전파시키는 주된 구동력이 된다. 또한 승강기를 피난용으로 사용하기 위해서도 연돌효과는 반드시 극복되어야 할 과제이다. 이 논문에서는 연돌효과가 고층건물의 승강기 승강로에 미치는 부정적 영향을 줄이기 위해 승강로를 가압하는 방식을 검토하였다. 승강로와 거실 사이를 균압화하고 승강로를 급기 가압하는 조건으로 시뮬레이션 함으로써 NFPA 92A와 IBC 2012에서 요구하는 조건에 근접하는 결과를 얻었다.

• 한국전산유체공학회지
• /
• 제14권2호
• /
• pp.68-76
• /
• 2009

The sloshing tank causes the instability of the fluid flows and the fluctuation of the impact pressure by the liquid on the tank. These flow characteristics inside the sloshing tank can generate the uncomfortable sloshing noise. In the present study, a numerical analysis for the reduction of a fuel tank sloshing noise was performed. To simulate the flow characteristics in a sloshing tank with partially filled liquid, a VOF method was used for interfacial flows by applying a momentum source term for the sloshing motion in a non-inertial reference frame. This numerical method was verified by comparing its results with the available experimental data. For the reduction of the sloshing noise, the horizontal and vertical baffles and porous media inside a sloshing tank were considered and numerically analyzed in the present study. For various installations of these baffles and porous media, the characteristics of the liquid behavior in the sloshing tank were obtained along with the impact pressure on the wall and the height of the free surface along the wall. These basic results can be used for the design of the actual vehicular fuel tank with the reduced sloshing noise.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권9호
• /
• pp.743-748
• /
• 2016

선박의 주기관으로 통상 사용되는 디젤기관은 터빈기관과 같은 회전기관과 달리 왕복동기관이기 때문에 실린더의 폭발력과 피스톤의 왕복관성력에 의한 불평형 관성력 및 관성모멘트, 실린더내의 주기적인 변동가스압력 등으로 인하여 본질적인 진동문제를 안고 있다. 이것은 엔진의 진동은 소음의 원인이 되고, 선체구조나 인접구조물에 전달되어 2차진동이 발생시키는 경우가 많다. 본 연구는 선박의 엔진과 축계의 자유진동해석과 엔진 폭발에 의한 강제진동해석을 하고, 나아가서 플라이휠에 부진동 장치인 동흡진기를 설치하여 진동을 줄이는 방법을 제안하고자 한다.