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수력발전소 가이드 베인 저개도율 운전에 따른 가이드 베인 베어링 부슁의 마모 가속효과 평가
김종성(Jong Sung Kim),김세나(Se Na Kim) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.10
가이드 베인은 수력발전소 수차에 공급되는 물량을 제어하는 핵심적인 역할을 수행한다. 가이드 베인 베어링 부슁에 발생하는 마모와 관련하여 많은 정비 사례들이 보고되고 있다. 수력발전소의 중요기능인 주파수 조정, 급전 등과 같은 부수적 서비스는 가이드 베인을 작게 열고 운전하는 저개도율 운전을 반복적으로 수행하게 한다. 이러한 저개도율 운전은 가이드 베인 베어링 부슁의 마모율을 증가시키는 것으로 경험적으로 알려져 있다. 본 연구에서는 수력발전소의 가이드 베인 저개도율 운전이 가이드 베인 베어링 부슁의 마모를 가속시키는 효과를 유한요소 유동/응력 해석 및 상대적인 마모 평가를 통해 정량적으로 평가한다. 평가 결과, 가이드 베인 개도율이 작을수록 가이드 베인면에 작용하는 압력이 증가하고 가이드 베인 스템 외면과 베어링 부슁 내면 사이의 접촉길이는 감소하였으며 베어링 부슁 표면에 작용하는 접촉압력이 크게 발생하여 상대적으로 마모량이 증가함을 확인하였다. A guide vane plays a key role in controlling the flow rate of water supplied to the turbine of a hydropower plant. It has been reported that guide vane bearing bushings are subjected to considerable wear, which requires them to be maintained. An ancillary service such as frequency control and black start causes cyclic low opening operation of the guide vanes. It is empirically well known that such operation increases the wear rate of the guide vane bearing bushing. In this study, the effect of low opening operation on the increasing wear of the guide vane bearing bushing is quantitatively assessed via finite element flow analysis, finite element stress analysis, and relative wear evaluation. As a result of the assessment, it is identified that the pressure applied on the guide vane surface increases and the contact length between the outer surface of the guide vane stem and the inner surface of the bearing bushing decreases with a decrease in the opening of the guide vane. In addition, low opening of the guide vanes results in an increase in the relative wear owing to the generation of high contact pressure on the bearing bushing surfaces.
수력발전소 가이드 베인 저개도율 운전에 따른 가이드 베인 베어링 부슁의 마모 가속효과 평가
김종성(Jong Sung Kim),김세나(Se Na Kim Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.2
가이드 베인은 수력발전소 수차에 공급되는 물량을 제어하는 핵심적인 역할을 수행한다. 가이드 베인의 스템들은 베어링 부슁을 통해 헤드 커버내 구멍들과 접촉된다. 수력발전소의 가이드 베인 베어링 부슁에 발생하는 마모와 관련하여 많은 정비 사례들이 보고되고 있다. 수력발전소의 중요기능인 주파수 조정, 급전 등과 같은 부수적 서비스는 가이드 베인을 작게 열고 운전하는 저개도율 운전을 반복적으로 수행하게 한다. 이러한 저개도율 운전은 가이드 베인 베어링 부슁의 마모율을 증가시키는 것으로 경험적으로 알려져 있다. 그러나, 이러한 주제에 대한 어떠한 연구도 수행된 바 없다. 따라서 본 연구에서는 수력발전소의 가이드 베인 저개도율 운전이 가이드 베인 베어링 부슁의 마모를 가속시키는 효과를 유한요소 유동/응력 해석 및 상대적인 마모 평가를 통해 정량적으로 평가한다. 평가 결과, 가이드 베인 개도율이 작을수록 베어링 부슁 표면에 작용하는 접촉압력이 크게 발생하여 상대적으로 마모량이 증가함을 확인하였다. Guide vane plays a key role to control water flow rate which is supplied to a turbine of hydropower plant. Stems of the guide vanes make contact with holes in head cover via bearing bushing. It has been reported that there are lots of the maintenance histories related to wear occurred on the guide vane bearing bushings in hydropower plants. The ancillary service such as frequency control and black start, which is important function of the hydropower plant, gives rise to cyclic low opening operation of the guide vanes. It is empirically well known that this low opening operation increases the wear rate of the guide vane bearing bushing. But, no study about this topic has performed yet. Therefore, in this study, acceleration effect of the low opening operation on the wear of the guide vane bearing bushing is quantitively assessed via finite element flow analysis, finite element stress analysis, and relative wear evaluation. As a result of the assessment, low opening of the guide vanes results in increase of the relative wear quantity due to generation of high contact pressure on the bearing bushing surfaces.
공압식 소재물림 가이드부쉬 시스템의 설계 및 가공정도 평가
이재훈(Jae-Hoon Lee),이수민(Su-Min Yi),박성훈(Seonghun Park),이시복(Shibok Lee) 한국생산제조학회 2010 한국생산제조학회지 Vol.19 No.6
Generally, a fixed type guide-bush system is installed during machining miniature work-pieces with high precision in the multi-task CNC lathe. But a conventional guide-bush system does not provide a constant clamping force under the condition of varying work-piece diameters. It is important to maintain a constant clamping force for guaranteeing machining precision. This paper proposes a new guide-bush system with a pneumatic clamping device for the CNC Swiss-turn lathe to keep constant clamping force with changes in work-piece diameters. Through performance tests, new clamping system developed in the study showed better machining precision at the cost of a small increase in the temperature of the system than conventional systems due to an increase in the frictional heat and a change in the heat transfer route.
자동차용 Shock Absorber의 경량화를 위한 Plastic Rod Guide 개발
박호성(Hoseong Park),하동헌(Dongheon Ha),김성수(Seongsoo Kim) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
The Rod Guide controls automobile’s behavior and it is one of the components of the Shock Absorber which implements the stability of adjustment and the comfortable riding quality by absorbing impact and vibration energy. The Rod Guide conducts functions of oil sealing, Rod-support and Sliding. The development of changing material from sinteried material to plastic is recently done to reduce weight and cost. However strength, lubricity, resistance to abrasion, dimensional stability, thermal resistance of material has to be maintained even material changes to plastics. This study is about developing an alternative material that can be applied to body and Du-Bush part with plastic resin such as PPA, PAA, PPS, POM, PEEK, PA12, PA66 for the effective material change. We evaluated properties as making test-specimens of each materials, and applied the most superior material to the component. We tried to find the optimum injection methods and shape which can maximize characteristics of materials, and raise applicability through durability test of assembly.
윤보람(Boram Yoon),최연국(Yeon Guk Choi),변문환(Mun Hwan Byoun) 한국자동차공학회 2023 한국자동차공학회 부문종합 학술대회 Vol.2023 No.5
Brake caliper is a critical component that applies braking force by pressing pistons against the brake disc. While caliper is primarily designed for functionality, external coating and design are also considered for caliper appearance. Caliper cover is an accessory that can be attached to the caliper to enhance its external appearance independent of caliper function. This cover is made of lightweight materials and designed with various colors and lettering. The attachment method and potential interference with other caliper components should be carefully considered to ensure proper assembly and attachment strength for caliper cover. In this paper, we study about caliper cover attachment method using rubber bush which offers advantages compared to other attachment methods. Caliper cover design is developed with consideration for aluminum die-casting productivity and avoiding interference with other caliper components. Assembly, detachment force and vibration durability tests are conducted using four combinations of caliper body and caliper cover samples. Through these test results, we confirmed the feasibility and effectiveness of the rubber bush attachment method for caliper cover.
On the Instantaneous and Average Piston Friction of Swash Plate Type Hydraulic Axial Piston Machines
Jeong, Heon-Sul,Kim, Hyoung-Eui The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.10
Piston friction is one of the important but complicated sources of energy loss of a hydraulic axial piston machine. In this paper, two formulas are derived for estimating instantaneous piston friction force and average piston friction moment loss. The derived formula can be applicable for piston guides with or without bushing as well as for axial piston machines of motoring and pumping operations. Through the formula derivation, a typical curve shape of friction force found from several experimental measurements during one revolution of a machine is clearly explained in this paper that it is mainly due to the equivalent friction coefficient dependent on its angular position. Stribeck curve effect can easily be incorporated into the formula by replacing outer and inner friction coefficients at both edges of a piston with the coefficient given by Manring (1999) considering mixed/boundary lubrication effects. Novel feature of the derived formula is that it is represented only by physical dimensions of a machine, hence it allows to estimate the piston friction force and loss moment of a machine without hardworking experimental test.