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하태웅,Ha Tae-Woong 한국유체기계학회 2006 한국유체기계학회 논문집 Vol.9 No.3
Leakage reduction through annular type seals of turbomachinery is necessary for enhancing their efficiency and the precise prediction method of seal leakage is needed. The analysis based on Bulk-flow concept has been mainly used in predicting seal leakage. However, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved for improving the prediction of seal leakage. FLUENT 6 which is commercial CFD(Computational Fluid Dynamics) code based on FVM(Finite Volume Method) and SIMPLE algorism has been used to analyze leakage of various non-contact-type seals in this presentation. Comparing with the results of Bulk-flow model analysis and experiment, the result of CFD analysis shows good agreement with that of existing theoretical analysis for the incompressible grooved seal and compressive plain and staggered seal. The CFD analysis also shows improvement on the leakage prediction of the incompressible plain seal and compressive see-through-type labyrinth seal.
Moody 마찰계수식을 사용한 래버린스 실의 회전체 동역학적 해석
하태웅,Ha, Tae Woong 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.3
The leakage and rotordynamic coefficients of see-through type gas labyrinth seals are determined using a two-control-volume-model analysis with Moody's wall-friction-factor formula which is defined with a large range of Reynolds number and relative roughness. Jet flow theory are used for the calculation of the recirculation velocity in the cavity. For the reaction force from the labyrinth seal, linearized zeroth-order and the first-order perturbation equations are developed for small motion about a centered position. The leakage and rotordynamic coefficient results of the present analysis are compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula and Pelletti's experimental results. The comparison shows that the present analysis using Moody's wall-friction-factor formula and Scharrer's theoretical analysis using Blasius' wall-friction-factor formula give the same results for a smooth seal surface and the range of Reynolds number less than $10^5$.
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 한국유체기계학회 2001 한국유체기계학회 논문집 Vol.4 No.2
Basic equations and their solution procedure we derived for the analysis of an annular pump seal in which the rotor has a large static displacement from the centered position. The Bulk-flow is assumed for a control volume set in the seal clearance and the flow is assumed to be completely turbulent in axial and circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about an eccentric position. Flow variables are expanded by using Fourier series for the solution procedure. Integration of the resultant first-order pressure distribution along and around the seal defines the 12 elements of rotordynamic coefficients of the eccentric annular pump seal. The results of leakage and rotordynamic coefficients aye presented and compared with the Marquette's experimental results and the San Andres' theoretical analysis.
하태웅,홍승준,Ha, Tae-Woong,Hong, Seung-Jun 한국자동차안전학회 2020 자동차안전학회지 Vol.12 No.3
This paper has presented the headlight inspection standards and methods of two-wheeled motorcycles considering Korean Motor Vehicle Safety Standards (KMVSS), Korean Motor Vehicle Inspection Standards (KMVI) and the inspection standards of the International Motor Vehicle Inspection Committee (CITA). As a result of analyzing the headlight luminous intensity test result with fixed inspection equipment, 21% does not meet the inspection standard proposed in this study, and 33.3% in mobile inspection equipment does not meet. The average luminous intensity of motorcycle less than 50 cc is 8,340 cd, so all the lightweight small sized motor cycles do not meet the proposed headlight inspection standard.
터보 펌프 고압 후로팅 링 실의 누설량 및 회전체 동역학적 특성 해석
하태웅,이용복,김창호,Ha, Tae Woong,Lee, Yong-Bok,Kim, Chang-Ho 한국유체기계학회 2001 한국유체기계학회 논문집 Vol.4 No.3
The floating ring seal has the ability of minimizing clearance without the rubbing phenomenon. It is often used in the turbo pump units of liquid rocket engines due to its superior leakage performance. The exact prediction of the lock-up position of the floating ring, the leakage performance, and the rotordynamic coefficients of the seal is necessary to evaluate the rotordynamic performance of the turbo pump unit. The governing equations(which are based on the Bulk-flow Model) we solved by the Fast Fourier Transform method. The lock-up position, leakage flow rate, and rotordynamic coefficients are evaluated according to the geometric parameters of the floating ring seal.
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(Tae Woong Ha) 한국트라이볼로지학회 2008 한국윤활학회지(윤활학회지) Vol.24 No.6
In order to improve the leakage prediction and rotordynamic analysis of an annular seal with a smooth rotor and circumferentially grooved stator, CFD analysis using FLUENT has been performed to determine the groove penetration angle α which is the angle of separation line between control volumes Ⅱ and Ⅲ in groove section of Ha and Lee's three-control-volume theory. Validation to the present analysis using new penetration angle determined by the CFD analysis is achieved by comparisons with the results of published Ha and Lee's analysis. For the leakage prediction the present analysis shows slight improvement and CFD results yields the best. Direct damping and cross-coupled stiffness coefficients are predicted better to the experimental ones. However, direct stiffness coefficient is predicted worse.
CFD를 사용한 스팀터빈용 각이 진 패킹 링 실의 누설량 예측
하태웅(Tae Woong Ha),강정현(Jung Hyun Kang) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.5
An angled labyrinth seal is used for the diaphragm-packing-ring seal design of steam turbine due to its leakage reduction characteristic. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted angle which yields the best leakage reduction. Results show that the optimum value of slanted angle is -30° independent of number of labyrinth teeth, inlet pressure, and tooth height to pitch ratio. 3D CFD analysis has been performed for predicting leakage of the angled labyrinth seal. Comparing with the result of 2D CFO analysis, 3D CFD analysis shows 1.4% smaller.