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하태웅 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.3
The objective of this study is to develope the inspection standards and methods of motorcycle based on the Korean Motor Vehicle Safety Standards (KMVSS), the Korean Motor Vehicle Inspection Standards (KMVI), the inspection standards of the International Motor Vehicle Inspection Committee (CITA), United Kingdom, United State of America and Japan. 20 items related with motorcycle safety are suggested to inspect. Brake performance, headlight lamp, and speed are suggested to measure by a mechanical devices while the rest of items to inspect visually. The inspection with the suggested methods for 138 various models of runs are conducted for verifying the adaptability of present inspection standards. 88.4%, 54%, and 100% of runs satisfy the inspection criteria of the brake performance, lamp, and speedometer, respectively. Inspection time is expected to be about 10 to 16 minutes.
고성능 원심펌프에서 임펠러 시라우드 및 마모 시일의 유체가진력 해석
하태웅,Ha, Tae-Woong 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1
The analysis of lateral hydrodynamic forces in the leakage path between a shrouded pump impeller through wear-ring seal and its housing is presented. Governing equations are derived based on Bulk-flow and Hirs' turbulent lubrication model. By using a perturbation analysis and a numerical integration method, governing equations are solved to yield leakage and rotordynamic coefficients of force developed by the impeller shroud and wear-ring seal. The variation of rotordynamic coefficients of pump impeller shroud and wear-ring seal is analyzed as parameters of rotor speed, pressure difference, shroud clearance, wear-ring seal clearance, and circumferential velocity at the entrance of impeller shroud for a typical multi-stage centrifugal pump.
하태웅,Ha, Tae-Woong 한국트라이볼로지학회 2007 한국윤활학회지(윤활학회지) Vol.23 No.2
Leakage reduction through annular type labyrinth seals of steam turbine is necessary for enhancing their efficiency. In this study, modified geometry of the original combination-type-staggered-labyrinth seal has been suggested and numerical analysis for leakage prediction has been carried out for the modified-combination-type-staggered-labyrinth seal both based on bulk-flow model and using the CFD code FLUENT. The theoretical analysis based on bulk-flow model yields leakage reduction of the modified combination type staggered labyrinth seal by about 11%. Comparing with the result of Bulk-flow model analysis, the leakage result of CFD analysis shows reasonable agreement within 9.8% error.
하태웅,최복성 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.4
Annular seals are primarily used to control the leakage in turbomachinery, such as pumps. Consequently, annular seals substantially affect the stability of turbomachinery. Designing the annular seals of high performance pumps require the accurate prediction of the seal’s leakage flow rate and rotordynamic coefficients. The bulk-flow model is the traditional means for leakage flow rate analysis and predictions. Bulk-flow analysis is based on the Hirs’ lubrication equation, which simplifies the Navier-Stokes equation. However, the analysis of the bulk-flow model requires a great amount of time to develop an analysis code. Furthermore, the code possesses many constraints for analyzing seals with complicated shapes. 3D CFD simulations provide faster and less expensive estimates of the flow field for a wide variety of operating parameters and flow conditions. In this study, the flow field and the rotordynamic coefficients of a plain-eccentricannular seal were simulated with circular whirl orbits using 3D CFD code. A relative coordinate system was defined to calculate the 3D velocity profile and the dynamic pressure distribution of the seal clearance for each rotor whirling speed. The rotordynamic coefficients were determined by reaction forces of seal fluid, which were calculated by integrating the dynamic pressures to the whole area of seal. The results from our analyses were compared to existing theoretical calculations as well as compared to results acquired from experiments. The present 3D CFD results of leakage and rotordynamic coefficients of K and C showed better improvement in prediction.
하태웅,이안성 한국소음진동공학회 1998 소음 진동 Vol.8 No.5
An analysis of lateral hydrodynamic forces of compressor labyrinth seals is presented. Basic equations are derived using a two-control-volume model for compressible flow. Blasius' wall friction-factor formula and jet flow theory are used for the calculaton of wall shear stresses and recirculation velocity in the cavity. Linearized zeroth-order and first-order perturbation equations are developed for a small motion about the centered position by expansion in the eccentricity ratio. Integraton of the resultant first-order pressure distribution over the seal defines the rotordynamic coefficients. As an application a rotordynamic analysis of the balance drum labyrinth seal found in an ethylene regrigeration copmressor is carried out. The rotordynamic characteristic results of the labyrinth seal are presented and compared with other types of seals, honeycomb seal and smooth seal.
마찰계수 급상승 특성이 실의 로터다이나믹 특성에 미치는 영향
하태웅 한국소음진동공학회 1996 소음 진동 Vol.6 No.2
This study is to analyze the rotordynamic effect of surface-friction- factor characteristics on an annular seal. The honeycomb geometry which shows friction-factor-jump phenomena is used in this study. A rotordynamic analysis for a contered annular seal has been developed by incorporating empirical friction-factor model for honeycomb stator surfaces. The results of the analysis for the honeycomb seal showing the friction-factor jump is compared to the non- friction-factor-jump case. The results yield that the friction-factor-jump decreasesdirect stiffness and cross coupled stiffness coefficients, and increases damping coefficient to stabilize rotating machinery in a rotordynamic point of view. The analysis of the honeyeomb seal for the friction-factor-jump case shows reasonably good compared to experimental results, especially, for cross coupled and damping coeffcients.