• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.638-642
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• 2016

현재 양력발생의 원리는 긴 경로 이론과 동시 통과 이론 등으로 알려져 있으며, 이 이론들은 간단히 설명하려는 목적으로 인해 양력발생의 원리가 와전되어왔다. 본 연구에서는 여러 양력발생의 원리 중 Kutta-Joukowski의 이론을 이용하여 순환을 통한 양력발생의 관계에 대해 연구를 수행하였다. 해석 모델은 대칭형 에어포일인 NACA0012를 이용하였다. 해석 프로그램으로는 EDISON을 이용하였으며 시간에 따른 와도를 확인하기 위해 비정상상태 해석을 진행하였다. 그 결과 유동이 시간의 경과에 따라 에어포일 뒷전으로 밀려나면서 Kutta-Joukowski의 이론에 중요한 논점인 출발 와류가 생성됨을 확인할 수 있었다. 이로 인해 순환이 형성되어 양력이 발생함을 추측할 수 있다. 추가적으로 받음각과 출발 와류 사이의 영향성을 연구하였다. 받음각이 커짐에 따라 출발 와류가 에어포일 뒷전에서 더 크게 발생하였고, 받음각이 낮아질수록 출발 와류의 진행이 가속화됨을 확인할 수 있었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.9-12
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• 2010

This paper discusses experimental data for the assessment of flow discharging characteristics of double swirl coaxial injectors operating at fuel-rich conditions. Combustion tests employing liquid oxygen and kerosene (Jet A-1) were conducted and a discharge coefficient was utilized for defining flow characteristics. A mass flow rate, a pressure, and a temperature were measured to estimate discharge coefficients. Fuel injectors revealed a fixed value of a discharge coefficient regardless of matched LOx injector design, chamber pressure, and mixture ratio. However, oxidizer injectors showed varying discharging coefficients depending on chamber pressure and mixture ratio. Flame structure variations seem to affect flow discharging characteristics of the oxidizer side.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.790-797
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• 2010

Mode transition of the axi-symmetric screech tone in the low supersonic Mach number range from 1.0 to 1.20 is numerically analyzed. The axi-symmetric Navier-Stokes equations and the k-e turbulence model are solved in the cylindrical coordinate system. The dispersion-relation-preserving(DRP) scheme is applied for space discretization and the optimized four levels marching method are used for time integration. At low supersonic Mach numbers with an axi-symmetric A1 mode in the simulation, it is shown that acoustic propagation due to the nonlinear effects is seen in the lateral direction and the screech tone frequency is the same as the vortex passing frequency due to the generation of intense large-scale vortical motions.

• Journal of computational fluids engineering
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• v.8 no.2
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• pp.49-56
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Navier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Journal of computational fluids engineering
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• v.8 no.3
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• pp.1-6
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Wavier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. the endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency The effects of both turbulence model and convective differencing scheme on the Prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence modei on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.47-55
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• 1999

A study on swirl chamber for diesel engine is to realize lower fuel consumption and exhaust emission than the current marketing engines. Author formerly reported the performance characteristics of small IDI diesel engine with swirl chamber by changing the jet passage area and its angle, and the depth and shape of the piston top cavity. Following after the first report, in this paper, the characteristics of fuel consumption, soot emission, and exhaust gas temperature were examined and analyzed after dimension of jet passage area expanded to $70.1mm^2$ The results were that the optimum values of the jet passage area depending on the depth of the piston top cavity were different at each engine speeds and loads, and in accordance with application of engine running conditions they were able to be selected as optimum dimensions of each design parameters.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.371-374
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• 2006

The objective of this study is to determine the influence of free-stream turbulent intensity on the three-dimensional turbulent flow in a linear turbine cascade. The range of free-stream turbulence intensity considered is 0.7~10%. This study was performed numerically. The results show that the mass averaged loss coefficient increased according to the increase of free-stream turbulence intensity due to increased value of the mass averaged total pressure loss coefficient which was higher than the decreased value of the mass averaged secondary flow loss coefficient. The loss coefficient distribution was changed suddenly at a free-stream turbulence intensity of 10% while the loss coefficient distribution was rarely changed at a lower free-stream turbulence intensity of 5%.

• Journal of computational fluids engineering
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• v.8 no.1
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• pp.8-15
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Wavier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• 연구논문집
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• s.25
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• pp.55-65
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• 1995

Three-dimensional incompressible turbulent flow fields within the passage of the steam turbine nozzle with/without tip clearance have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The extended k-e model is applied to modeling the Reynolds stresses. Grids in the computational domain are generated by solving the Poisson's equations to improve the smoothness and orthogonality. Flow losses, secondary flow, velocity profiles, and deviation angles are obtained. The computated results without tip clearance show good agreement with the experimental data.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.23-29
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• 2005

Numerical analysis of three-dimensional viscous flow-fields in the turbine rotor passages was carried out to investigate flow physics including the interaction between secondary vortices, tip leakage vortex, and the rotor wake. The blade tip geometry was accurately modeled adopting the embedded H grid system. An explicit four-stage Runge-Kutta scheme was used for the time integration of both the mean flow and turbulence equations. The computational results for the entire turbine rotor flows, particularly the tip clearance flow and the secondary flows, were interpreted and compared with the experimental data from the Penn State turbine stage. The predictions for major features of the flow field have been found to be in good agreement with the experimental data.