• The KSFM Journal of Fluid Machinery
• /
• v.7 no.6 s.27
• /
• pp.15-20
• /
• 2004

Numerical analysis of the partial admission turbine in the KARI turbopump has been performed. Flow field of the partial admission turbine is intrinsically unsteady and three dimensional. To avoid heavy computational efforts, the frozen rotor method is adopted in computation and compared with the mixing plane approach. The frozen rotor method can represent the variation of a flow field along the circumferential direction of rotor blades, which have the different relative positions to the nozzle with one another. It also illustrates the wake loss mechanism starting from the lip of a nozzle, which is not captured in the mixing plane method. The frozen rotor method has proven to be an efficient tool for the design of a partial admission turbine.

• Proceedings of the Safety Management and Science Conference
• /
• 2000.11a
• /
• pp.7-11
• /
• 2000

기업 생산 활동의 중요한 요소 4가지를 살펴본다면 사람, 기계, 원료, 방법이라고 이야기 한다. 기업에서는 생산성을 높이기 위하여 각종의 여러 기법등을 통하여 생산성 향상에 촛점을 두고 있다. 그러나 생산성 향상만큼 중요한 것은, 기업이 생산활동을 하는데 있어 기업의 손실을 최대한으로 감소시킬 수 있느냐에 따라서 기업의 성공여부가 결정될 수 있을 것이다. 기업에서 발생되는 손실부분중 커다란 부분을 차지하고 있는 것이, 산업재해로 인한 인적·물적인 손실이라고 할 수 있다. 현재 기업의 산업안전에 관한 실태를 살펴보면 인간중심의 안전관리보다는 기계중심의 안전관리가 더 우월하게 이루어지고 있다. 산업재해를 예방하기 위한 방법으로 기업 내에서 실시되는 산업 안전 교육이 기업 내에서 효율적으로 자리잡아 기업의 생산성 향상에 도움이 되고자 한다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.72-80
• /
• 1988

Partially premixed diffusion system is analyzed using the matched asymptotic expansion technique adopting counterflow with supplying fuel and oxidizer from one side and fuel only from the other as a model problem. Results show that single-stage extinction always occurs as stretch increases, and the partially premixed diffusion flame can hardly exist. Depending on the initial mixture concentrations, either premixed or diffusion flame extinction leads to complete extinction of the system, and the diffusion flame can change its character to premixed flame such that two premixed flames can exist in the partially premixed-diffusion system.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.10
• /
• pp.2457-2466
• /
• 1993

A simple method is presented for determining transient responses of locally nonlinear structures using substructure eigenproperties and Lagrange multiplier technique. Although the method is based upon the mode synthesis formulation procedure, the equations of the combined whole structure are not constructed compared with the conventional methods. Lagrange multi-pliers are used to enforce the conditions of geometric compatibility between the substructure interfaces and they are treated as external forces on each substructure itself. Substructure eigenvalue problem is defined with the substructure interface free of fixed. The transient analysis is based upon the recurrence discrete-time state equations and offers the simplicity of the Euler integration method without requiring small time increment and iterative solution procedure. Numerical examples reveal that the method is very accurated and efficient in calculating transient responses compared with the direct numerical integration method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.1
• /
• pp.79-84
• /
• 2004

A light-guide is one of several important components of backlight unit in TFT-LCD. The manufacturing technology and optical system design of the light guide is very sensitive to quality and cost of the TFT-LCD module. In the present study a new manufacturing method which is called as direct surface forming(DSF) has been tested under various conditions. DSF is very similar to the well-known hot embossing except for partial contact between mold and substrate. The final V-groove pattern shows different shapes depend on the temperature of mold surface, contact time of mold and depth of V-groove.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2002.05a
• /
• pp.871-877
• /
• 2002

현재 공작기계의 상당부분에서 자동화 및 무인화가 이루어지고 있는 추세이며, 이러한 대부분의 산업시설들과 기계류에는 회전체 부품들을 가지고 있다. 이들 부품들에서 베어링(Bearing)은 절대적으로 매우 중요한 부분을 차지하고 있으며, 만일 회전축시스템(Rotor System)에 베어링의심각한 이상은 시스템이 정지되는 사태를 불러일으킬 수도 있다. 따라서 이상에 대한 조기 감지의 역할은 전체 시스템의 향상뿐만 아니라, 비용이나 시간적인 측면에서도 크나큰 이익을 가져다 줄 수 있다. 지금까지 이러한 회전축시스템에 대한 다양한 이상진단을 시도하여 왔으며 앞으로도 많은 종류의 이상진단이 이루어지리라 생각한다. 이런 다양한 형태의 이상진단은 시스템에서 추출되는 데이터를 여러 가지 기법과 추출하는 센서의 특징을 파악하여 이상진단 알고리즘을 수립하는 과정을 망라하게 된다. 특히 이상진단 알고리즘에는 측정된 데이터의 불확실성을 감안한 이론이 적용되어야 한다. 본 연구에서는 회전축시스템의 베어링에 대한 이상진단을 통계적 기법, Fuzzy Clustering, Neural network과 Neuro-fuzzy를 이용한 기법과의 상호비교를 통해서 여러 종류의 이상을 구분하는 작업수행을 연구하고자 한다.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.4 s.37
• /
• pp.13-19
• /
• 2006

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• Proceedings of the KSME Conference
• /
• 2001.06b
• /
• pp.341-348
• /
• 2001

In this study, a method is presented to find out a relationship between modes of a substructure and those of the system structure. Superelement analysis is performed for a full vehicle system, where the bus is partitioned by six parts. In this study, Modal Assurance Criteria(MAC) which is to represent the correlation between two mode shapes is used to investigate the contribution factor of each substructure for the full system. The proposed participation factor can be used for design of substructures to meet the design target of the total structural system.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.899-904
• /
• 2004

Multibody dynamics formulation has been developed based on relative cartesian coordinates for subsystem analysis. Relative cartesian coordinates are defined with respect to a reference body of a subsystem. Relative cartesian formulation inherits the same merits of absolute cartesian formulation, such as generality and easy implementation. Two methods have been applied. One is Largrange Multiplier Elimination method and the other is independent coordinate method. A 1/4 car simulation has been carried out to verify the formulations. Since both methods provide identical results, it proves the validity of the formulation.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.911-916
• /
• 2004

The paper deals with the dynamic stability of a cantilevered Timoshenko beam on partial elastic foundations subjected to a follower force. The beam is assumed to be a Timoshenko beam with a concentrated mass taking into account its rotary inertia and shear deformation. Governing equations are derived by extended Hamilton's principle, and FEM is applied to solve the discretized equation. Critical follower force depending on the attachment ratios of partial elastic foundations, concentrated mass and rotary inertia of the beam is fully investigated.