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개방형 원심압축기에서의 틈새크기에 따른 유동특성에 관한 실험적 연구
김진형,조강래 연세대학교 산업기술연구소 1994 논문집 Vol.26 No.2
The Pressure loss due to leakage flow is directly related to the tip clearance size of centrifugal impeller. The performance and the pressure distribution along the shroud casing are measured by using pressure transducer system for unshrouded centrifugal compressor at different size of tip clearance. The characteristic curves With respect to the size of tip clearance are presented as one curve regardless of rotational speed. As the size of tip clearance increases form 0.5mm through 2.0 mm, the values of pressure coefficient of characteristic curves decrease linearly due to the increase of leakage loss. The reduction rate of static pressure coefficients per 1 mm tip clearance is 0.04∼0.047, and the reduction rate per c/b₂is 0.28 evenly. The pressure coefficient for radial direction on the shround casing surface is presented as one curve regardless of rotational speed and decreases linearly. The reduction rate of pressure coefficient is nearly identical to that of characteristic curves.
굴삭기 상부작업체에서 틈새의 영향을 고려한 버켓의 거동의 편차에 대한 연구
신대영(D. Y. Shin),강태곤(T. G. Kang),황성호(S. H. Hwang) 유공압건설기계학회 2018 유공압건설기계학회 학술대회논문집 Vol.2018 No.11
The excavator consists of boom, arm and bucket, and the boom, arm and bucket are driven by hydraulic cylinder. The clearance of the upper part of the excavator reflects the clearance of the joint part of the hydraulic cylinder and compares the angles of the joint parts and studies the deviation of the bucket behavior due to the clearance of the joint. As the clearance of the joint increases, the angle of rotation of the joint increases, this ultimately affects the deviation of the bucket behavior.
굴삭기 상부작업체에서 틈새에 의한 버켓의 거동 편차에 대한 연구
신대영,강태곤 사단법인 유공압건설기계학회 2019 드라이브·컨트롤 Vol.16 No.4
Bucket trajectory is crucial regarding precision work with an excavator. In general, the bucket trajectory deviation is determined by the machining deviation of the frame, driving deviation of the driving hydraulic cylinder, clearance in the joints, and deformation of the structure. This paper investigated the relationship between the respective clearance in joints and the trajectory deviation of the bucket at the finishing work of the ditching for a 20-ton excavator. As a result, the larger the clearance, the larger deviation is increased at trajectory. However, it was found that the deviation of the rotation angle and displacement of the bucket was limited and the size of clearance does not affect closely on the contact angle of the pin shaft.
고기동 위성용 태양전지판 힌지 틈새의 진동감쇠효과 분석
김용하,김현덕,박정선 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11
항공 우주 구조물에서는 두 개 이상의 요소가 합쳐진 경우가 많다. 힌지는 두 개 이상의 요소를 연결해주는 역할은 한다. 실제 힌지로 채결된 구조물은 제작오차나 마모로 생긴 미세 틈새가 존재하지만 힌지로 채결된 구조물의 과도해석은 힌지 사이의 미세 틈새가 없다고 가정하여 진행된다. 본 연구에서는 400 ㎏급 고기동 소형위성의 태양전지판 모듈의 핀 조인트 사이의 미세틈새 유무와 틈새의 크기에 따른 진동감쇠효과를 분석하였다. In the aerospace structure, There are a great amount structure consisting of two parts. The hinge makes a role connecting of two parts. In the real structure consisting of hinge, there is a clearance of hinge owing to errors of manufacturing, abrasion and wear. The transient analysis of structures consisting of hinges is progressing by assuming that there is not clearances of hinges. This thesis analyse the vibration damping effects by existence of clearance and magnitude of clearance in the solar array structure module for 400 ㎏ class high-agility satellite.
파이로테크닉 분리 너트 내부 분할 너트 체결 특성에 대한 틈새의 영향
우정민(Jeongmin Woo),강다훈(Dahoon Kang),최재영(Jaeyoung Choi),김정호(Jeong Ho Kim),조진연(Jin Yeon Cho),장승교(Seung-gyo Jang),양희원(Hee Won Yang) 한국항공우주학회 2018 韓國航空宇宙學會誌 Vol.46 No.12
유한요소 해석을 이용하여 분할 너트를 이용하는 파이로테크닉 분리 너트의 체결부 특성을 파악하였다. 분할 너트를 이용하는 경우, 체결 과정에서 분할 너트가 반경 방향으로 벌어지는 것을 막기 위해 구속해주는 구속원통이 필수적이다. 이때, 제작 과정에서 공차로 인해 분할 너트의 외경과 구속원통 내경 사이에 발생하는 틈새의 영향을 파악하기 위하여 적절한 유한요소 볼트 체결 모델링 기법을 연구하였으며, 틈새가 0.00, 0.03, 0.06, 0.10 ㎜인 모델을 만들어 해석 결과를 검토하였다. 해석 결과를 통해 너트의 분할 여부 및 틈새 크기에 따라 달라지는 체결부의 특성을 확인하였으며 이로부터 신뢰성 있는 파이로테크닉 분리너트 설계를 위해 고려해야 할 사항을 파악하였다. The clamping characteristics of segmented nuts in pyrotechnic separation nut are investigated using finite element analysis. When the segmented nuts are used to clamp objects, a constraint cylinder is necessary to prevent the segmented nuts from spreading out to the radial direction. During the manufacturing process, a clearance is usually introduced between the outer diameter of the segmented nuts and the inner diameter of the constraint cylinder. Therefore to find out the effect of the clearance, proper finite element modeling method is suggested to describe the clamping procedure appropriately. In addition, finite element analysis with the clearance of 0.00, 0.03, 0.06, and 0.10 ㎜ are performed. From the analysis results, the clamping characteristics of segmented nuts are investigated according to the clearance, and several factors which should be considered to design a reliable pyrotechnic separation nut are figured out.
고압 인젝터의 동적 거동을 고려한 최적 틈새 조합에 관한 연구
류대원(Daewon Ryu),김동준(Dongjun Kim),박상신(Sang-Shin Park),류봉우(Bongwoo Ryu) 한국트라이볼로지학회 2021 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.37 No.5
An injector is a mechanical device present inside the engine. Its main function is to supply an appropriate volume of fuel into the combustion chamber, which is directly related to the overall engine efficiency of a car. During the operation of an injector, a magnetic force lifts the parts of the injector from closed position to open position which generates a horizontal force on the needle. The horizontal force acts on a different position from that of the center of mass of the needle. Therefore, this causes eccentricity in the needle and the generation of a tilting motion during the lifting operation which can result in wear. However, appropriate selection of clearances for these parts can prevent wear. In this study, lubrication analysis is conducted to determine the optimum clearance of parts with sliding motion inside the injector. The height functions are derived considering the dynamic behavior and relative velocity of the parts. Using the derived height function, the pressure profiles are calculated for the lubricated surfaces from the Reynolds" equation. Subsequently, the fluid reaction forces are calculated. The equations of motions are applied to the fluid reaction forces and external forces are solved to calculate the minimum film thickness between each part with variation in the clearances. Finally, the optimum clearances are determined. The effect of the clearances on the behavior of the moving parts is presented and discussed.
축류팬 팁 틈새와 유량이 공력 및 소음 특성에 미치는 영향에 관한 수치적 연구
조기영(Kiyeong Jo),한상욱(Sangwook Han),김형민(Hyung Min Kim),양시영(Siyoung Yang) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
The thermal management of the industrial and technical systems are the most important topic to increase the performance and energy efficiency of the system. The simplest way to cool the system is to use an axial fan, however another problem with improving the cooling performance is the fan noise caused by the airflow. And it is known that the noise intensity of the axial fan is affected by the tip clearance. In the research it has been performed a flow simulation with a rotating fan to determine the relationship between the noise and tip clearance. For the turbulent flow RANS, k-omega SST turbulence model has been applied and BNS model are applied to define the noise level by the flow. By comparing the performances of the axial fan as tip clearance varies from 1 to 3mm, it was verified that the flow rate at BEP is not coincides with the designed volume flow rate. In addition, it was confirmed that the acoustic power level increased as the tip clearance increased.
김웅(Woong Kim),이춘만(Choon Man Lee),황영국(Young Kug Hwang) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.9
The spindle is the main component in machine tools. To develop high speed machine tools, a lot of studies have been carried out for high speed spindle. Bearing is very important part in spindle. The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of shrink fits. The aims of this study are to grasp the shrink fits and behavior of a bearing which is a deeply connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). This paper proposed optimum value of shrink fit considering deformation of spindle and stress of fitting area using design of experiments. Thus, the proposed formula can be used to obtain bearing internal clearance.
직선 이중관식 소형 온수히터 개발을 위한 열유동 특성 해석
양영준 한국기계기술학회 2021 한국기계기술학회지 Vol.23 No.5
Small-sized heater is usually used to make the hot water in resting place, factory, household affairs and so on. One of methods to obtain hot water in short time is known as using instantaneous electric water heater. In this study, numerical analysis for small-sized hot water heater with straight double tube-type was tried to achieve the basic design data. This study aims to investigate the characteristics of thermal flow, for instance, such as pressure difference, outlet mean temperature and velocity, due to clearance. As the clearance is decreased, outlet mean temperature and pressure difference(Pmax.-Pmin.) are increased. Therefore appropriate relations between area of heat source and pressure difference should be set up. Further small-sized hot water heater in this study must be equipped with electric device capable of heating over 90℃.