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Performance Improvement of Oil Pump by Design of Gerotor (Combined Profile ? Two Ellipses) and Port
곽효서(Hyo Seo Kwak),이승환(Sheng Huan Li),김철(Chul Kim) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.3
A gerotor is suitable for miniature manufacturing because it has high discharge per 1 cycle and a simple structure, while also being widely used for lubrication oil of engines and as a hydraulic source of automatic transmission. In the automobile industry, improvements in fuel efficiency and noise reduction have recently come to the fore. It has also been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency through optimal gerotor and port shape design. In this study, to develop an optimal gerotor with a new lobe shape, 2-ellipses-combined, the equation of the lobe shape was derived, and CFD analysis results were compared for 2-ellipses with those of the previous gerotors (3-ellipses and ellipse1-involuteellipse2). A performance test for the oil pump with the optimal rotor (2-ellipses) was carried out and showed good agreement with the results obtained from CFD analysis.
곽효서(Hyo Seo Kwak),이승환(Sheng Huan Li),김철(Chul Kim) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.11
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.
타원 1-타원형 인벌루트-타원 2 로브 형상의 제로터 최적 설계
곽효서(Hyo Seo Kwak),이승환(Sheng Huan Li),김철(Chul Kim) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.12
제로터(Gerotor) 오일펌프는 구조가 간단하고 1 회전당 토출량이 많기 때문에 소형화에 유리하며, 자동차의 엔진 윤활유 공급원 및 자동 변속기의 유압원으로 널리 사용되고 있다. 최근 자동차 산업에서는 연비향상 및 소음저감이 가장 중요한 문제로 대두되는데, 내접형 기어펌프 측면에서는 제로터의 치형설계 및 포트형상 설계를 통하여 이를 대처하고 있다. 이에 본 논문에서는 유량맥동이 매우 작은 값을 가지도록 조합된(타원 1-타원형 인벌루트-타원 2) 외부로브 형상에 대하여 치형의 기구학적 조건을 만족하는 식을 유도하여 내부로브 형상을 창출하였으며, 이에 대한 첨점 및 루프가 발생하지 않는 설계인자 범위를 결정하였다. 또한 설계인자의 변화가 치형의 형상 및 성능인자(유량, 유량맥동)에 미치는 영향을 파악하여 최적의 치형을 구하고자 하였다. A gerotor can be manufactured in a miniature size because it has a high discharge per cycle and a simple structure. Gerotors are widely used for the lubrication oil of an engine and as the hydraulic source of an automatic transmission. Recently, improvements in fuel efficiency and noise reduction have come to the fore in the automobile industry, and it has been necessary for better fuel efficiency to continuously improve the flow rate and noise of internal gear pumps through the optimal design of the gerotor and port shape. In this study, gerotors were generated based on the equations derived for a lobe shape with multiple profiles (ellipse 1-elliptical involute-ellipse 2). The ranges of the design parameters were considered to prevent a cusp and loop. In addition, the optimal lobe shape was obtained by determining the influence of the lobe shape on the performances (flow rate, irregularity, etc.), according to the values of the design parameters.
Design of Tip Clearance in the D.D.I. Process to Manufacture Pressure Vessel
곽효서(Hyo Seo Kwak),박건영(Gun Young Park),김철(Chul Kim) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.7
The liner of CNG pressure vessel was manufactured using a deep drawing and ironing (D.D.I.) process with a single punch. Tip clearance between billet and die suggested in the actual field has been widely used to reduce forming load and to improve die life. However, the analysis and design of tip clearance is necessary for the third stage of forming defect. In this study, the tip clearance of the third stage was determined to limit the ratio of reduction of cross-sectional area based on theoretical analysis. The proposed tip clearance was verified via finite element analysis. In addition, the simulation technique was established by comparing the forming load based on theoretical calculation with the load determined via FEM.
A Study on the Vibration Reduction of Turbine Rotor through Advanced Flexible Packing Rings
김현종(Hyeon Jong Kim),곽효서(Hyo Seo Kwak),성한샘(Han Saem Sung),이창렬(Chang Ryeol Lee),김철(Chul Kim) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.7
Steam turbines of thermal power plants are installed in such a way that packing ring surrounds the entire turbine rotors in order to reduce the amount lost due to a leak of steam and to improve performance. However, the conventional packing ring cannot affect positively fluid velocity of the direction of steam, so it does not have the power to reduce vibration of the rotor. In this research, a study was conducted to reduce it by lowering the rotational speed of steam in the rotor. Anti-swirl teeth which changes rotational speed of steam into axial speed of it, designed in front of the conventional packing rings, and their numbers, twist angles. The characteristics of the rotor and the anti-swirl teeth were chosen as design factors to reduce vibration of the rotor. Through the finite element, the improved packing ring designed with the optimal anti-swirl teeth was developed.
고영준(Young Jun Ko),곽효서(Hyo Seo Kwak),배준호(Jun Ho Bae),김철(Chul Kim) Korean Society for Precision Engineering 2014 한국정밀공학회지 Vol.31 No.12
Delta sash is an important part of automobile door, which has the functions of supporting and guiding seesaw of car’s window, preventing dust and air from outside. In previous manufacturing process, each part of the delta sash was independently formed by tandem processes, and rubber is bonded to steel by poisonous glue. So, the previous processes, including roll forming process and toxic gases, had low production rate and high failure rate. In this study, progressive process design of the delta sash was proposed in order to increase productivity and high utilization of the materials. And instead of the poisonous glue used for adhesion of rubber in the previous tandem process, embossing and piercing processes were designed in the new guide to help the rubber to adhere well to steel. And the optimal piercing distance was designed to ensure structural safety, and prototypes were manufactured for verifying reliability of the processes.
Development of an Advanced Oil Deflector Used in Thermoelectric Power Plant
최용훈(Yong Hoon Choi),곽효서(Hyo Seo Kwak),이창렬(Chang Ryeol Lee),김철(Chul Kim) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.8
Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.
최대 내용적을 갖는 수소압력용기의 형상설계 및 성형해석
박건영(Gun Young Park),곽효서(Hyo Seo Kwak),이광오(Kwang O Lee),김철(Chul Kim) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.10
최근 화석연료 고갈 및 환경오염 문제를 해결할 수 있는 대안으로 수소에너지가 주목받고 있으며, 고효율 및 주행거리 향상을 위한 수소 자동차 개발에 따라 수소 저장 압력용기의 내용적 증가 및 구조안전성이 요구되고 있다. 그러나, 반구형의 바닥부보다 내용적이 큰 타원형 바닥부의 형상설계가 이루어지지 않았으며, 타원형 바닥부의 성형공정에 관한 연구 또한 미비한 실정이다. 이에 본 연구에서는 수소압력용기 라이너의 타원형 바닥부 장단축비에 따른 최대 내용적을 계산하고 유한요소해석을 통한 구조안전성 검증 및 이에 대한 이론적 고찰을 검토하였다. 또한, 바닥부 성형 공정해석을 통하여 제안된 최대 내용적을 갖는 타원형상의 성형 가능성을 확보하였다. Recently, hydrogen energy has been in the spotlight as an alternative to diminishing fossil fuels and as a potential solution to environmental pollution. The development of hydrogen-fueled vehicles and the demands for improved fuel efficiencies have resulted in the need to increase the volume of the hydrogen pressure vessels. Pressure vessels having an elliptical bottom, as opposed to one that is hemispherical, allow for a greater capacity. However, there are insufficient studies on the feasibility of the forming process required for an elliptical bottom. In this study, the liner capacity is calculated according to the ratios of the major to the minor axes of the elliptical bottom part in a hydrogen pressure vessel. Structural safety is verified through finite element analyses, and the results are compared to the theoretical results. The feasibility of the proposed elliptical shape of the pressure vessel bottom, while filled to maximum capacity, is validated through forming analysis.