• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.331-335
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• 2006

Theoretically, stable operations of an inlet are achieved at the design condition. However, at off-design conditions supersonic inlets often encounter the problem of aerodynamic instability, called inlet buzz. During inlet buzz, supersonic inlets exhibit considerable oscillation of the shock system in front of the inlet and corresponding large pressure fluctuations downstream. This phenomenon results in decrease of engine performance. An experimental and numerical study was conducted to investigate the phenomenon of supersonic inlet buzz on a generic, axisymmetric, external-compression inlet with a single-surface center-body. This study suggest that intermittent buzz exist and the frequency become to be large as increasing the back pressure.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.70-77
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• 2005

An axisymmetric supersonic ejector equipped with a converging-diverging diffuser was built and pressure at various locations along the ejector-diffuser system was recorded with emphasis on the supersonic starting of the secondary flow. In order to find the effects of the opening size of the secondary flow, a number of openings were used with a constant primary pressure. Supersonic starting was possible only for d/D, the ratio of the opening diameter and the diffuser throat diameter, less than 0.306. for larger values of d/D, the ejection begins at subsonic secondary flow condition. With the closure of the opening, the primary flow brings the normal shock downstream of the converging-diverging diffuser And the starting of the ejector continues even after the closure was removed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.144-152
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• 2011

In order to investigate the operation performance behaviors of the UAV's propulsion system to be operated long time in high altitude, the engine performance tests, which are simulated in the altitude engine test facility should be needed. If the test is performed in a existing altitude engine test facility, additional test apparatuses are required. Among them a proper design of the inlet and exhaust ducts that may directly affect the engine performance is very important. If the design is not adequate, the engine performance loss due to the flow behavior change and the pressure loss may be not similar to the real engine performance. In this work, firstly the engine inlet and exhaust ducts to be mounted to the existing altitude facility are modelled in 3D and its flow behaviors and pressure losses are analyzed using a commercial CFD tool, ANSYS's CFX, and the engine performance with the duct losses is calculated using the performance analysis program developed by C. Kong et al. Finally, the optimized inlet and exhaust ducts' configurations are proposed through the repeated analyses of various duct configurations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1031-1038
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• 2017

In order to improve the performance of the air breathing engines, it is important to maximize the total pressure recovery through air intake. In this study, we investigated whether the Oswatitsch method, which guarantees the maximum pressure recovery for supersonic intake, is effective at hypersonic speed by compressing the intake air with the same intensity at each ramp. The non-linearity of the shock wave normal Mach number at each ramp stage was analyzed by comparing the compression ramp angle and the number of ramp to the inflow Mach number in terms of compressible thermodynamics and the operation limits of the inlet. Based on this analysis, the Oswaitisch technique yields valid conditions not only in supersonic but also hypersonic flight regime.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.426-437
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• 2007

off-design conditions, supersonic air inlets often encounter the problem of aerodynamic instability, called inlet buzz, which causes the significant degradation of the engine performance. An experimental and numerical study was conducted to investigate the phenomenon of supersonic inlet buzz on a generic, axisymmetric, external-compression inlet with a single-surface center-body. It is understood the mechanism of buzz onset as proving that the origin of buzz is the flow choking induced by separation at the intake throat. Also it is observed the intermittent and continuous buzz mode as area ratio varies and understood the transition process through this study. The buzz frequency become to be higher as decreasing the area ratio, but for each area ratio, the frequency of pressure oscillation is the same at all points of intake.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.4
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• pp.10-20
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• 2022

The performance analysis test of the scramjet engine intake was conducted under the Mach 5 condition of the scramjet engine test facility, a free-jet ground test facility of the Korea Aerospace Research Institute. A pitot/static pressure rake installed at the rear of the isolator was designed and manufactured to measure the total pressure recovery rate and mass capture ratio, which are typical performance factors of the scramjet engine intake. The effect of the rake mounted at the rear of the isolator on the intake, the performance analysis measured by the rake, and the change in wall static pressure distribution according to the angle of attack were performed. Finally, the point at which the intake unstart occurred was confirmed by using the rear back pressure adjusting device, which simulates pressure rise in the combustor, and the results are summarized in this paper.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.9-16
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• 2010

The SFRJ(Solid Fuel Ram-Jet) propulsion is attractive for projectiles because of the combination of high propulsive performance and low system complexity more than conventional projectiles. The Objective of this research was to characterize the inlet aerodynamic characteristics (center-body & pitot type) in SFRJ. Diffuser static pressure & combustion chamber pressure was tested and the AoA was changed $0^{\circ}$ and $4^{\circ}$ at Mach number of 3.0 for performance estimate. The performance study of inlet was carried out with the Schlieren system and Supersonic cold-flow system. Under mach 3.0, the center-body showed twice higher total pressure recovering ratio than the pitot type. A Computational fluid dynamic solution is applied internal flow of inlet and the solutions are compared with experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.133-137
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• 2009

Numerical simulations of flows in an axisymmetric supersonic inlet with bleed regions were performed. For the simulations, the existing code which solves the RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was transformed to axisymmetric form and bleed boundary condition was applied to the code. In this paper, the modified code was validated by comparing the results against an experimental data and other computational results for flow on a bump and over an oblique shock with bleed region. Using the code, numerical simulations were performed for the flow in the inlet with multiple bleed regions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.79-82
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• 2009

Unsteady numerical analysis of an entire supersonic propulsion system from intake to nozzle was performed to study dynamic interaction between terminal shock in the intake and flame in the combustor. Both acceleration and cruise flight-modes were considered. Acoustic mode of the entire engine for both flight-modes were investigated by detail analysis of pressure fluctuation at each location of engine.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.67-70
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• 2007

It is well known that the aircraft engine inlet should be safely designed against the bird strike at the aircraft development stage. The aircraft accident is increasing for FOD(Foreign Object Damage), especially bird of runway circumference. The aircraft accident due to bird strike brings about economic loss and which is connected with the life of passengers. In this study, MSC/DYTRAN has been utilized to analyze the aircraft engine inlet against the bird strike. In order to validate the proposed method for the bird strike analysis, this study was performed with comparison of precedence study results.