• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.563-570
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• 2017

Experimental and numerical studies were performed to investigate the performance and internal flow characteristics of a supersonic second throat exhaust diffuser (STED) with back pressure ($P_a$). An ejector system was used to vary the back pressure ($P_a$) conditions. The operating gas for the STED and the ejector was high pressure nitrogen at room temperature. When the back pressure ($P_a$) at a constant nozzle inlet pressure $P_0$) decreases, the pressure recovery location moves downstream. If the pressure ratio $P_0/P_a$) is the same, even if the nozzle inlet pressures $P_0$) are different, the diffuser's internal flow pattern and starting pressure ratio ($(P_0/P_a)_{st}$) are almost the same.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.346-351
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• 2017

A numerical study has been conducted to investigate flow characteristics of STED with ram structure shape. By increasing the attack angle of shock cone, vacuum pressure is increased because of oblique shock at ram structure and separation point moved to the downstream of the second throat. By increasing blockage ratio, expansion wave angle is increased at ram structure while vacuum pressure is constant.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.485-490
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• 2000

This paper dipicts the computational results for the axisymmetric subsonic/sonic ejector systems with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-Averaged Navier-Stokes equation in a domain that extends form the stagnation chamber to the ejector diffuser exit. In order to obtain practical design factors for subsonic/sonic ejector systems, the ejector throat area, the mixing section configuration, and the ejector throat length were changed in computations. For the subsonic/sonic ejector systems operating in the range of low operation pressure ratio, the effects of the design factors on the flow are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.269-276
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• 2001

This paper dipicts the computational results for the axisymmetric subsonic/sonic ejector systems with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-Averaged Navier-Stokes equation in a domain that extends from the stagnation chamber to the ejector diffuser exit. In order to obtain practical design factors for subsonic/sonic ejector systems, the ejector throat area, the mixing section configuration, and the ejector throat length were changed in computations. For the subsonic/sonic ejector systems operating in the range of low operation pressure ratio, the effects of the design factors on the flow are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.487-491
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• 2009

A study is analyzed on the design factor of Center-body diffuser and performed on conceptual design of Center-body diffuser with Computational Fluid Dynamic. The flow field of Center-body diffuser is calculated using Axisymmetric two-dimensional Navier-Stokes equation with $k-{\omega}$ turbulence model. The center-body diffuser is compared with second throat exhaust diffuser in terms of starting pressure, the degree of vacuum pressure, the design factor.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.34-39
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• 2014

A study is analyzed on the design factor of center-body diffuser and performed on conceptual design of center-body diffuser with computational fluid dynamic. The flow field of center-body diffuser is calculated using axisymmetric two-dimensional Navier-Stokes equation with $k-{\epsilon}$ turbulencemodel. The center-body diffuser is compared with second throat exhaust diffuser in terms of starting pressure, the degree of vacuum pressure and the design factors. The counter flow jet on cone-tip of the center-body is applied for thermal protection system in the center-body diffuser.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.65-74
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• 2002

Optimal supersonic diffuser shape of integrated rocket ramjet engine was derived which maximizes the total pressure recovery. Mass flux is considered as a design constraint and the second oblique shock angle of the external ramp, the cowl-lip angle and the throat area are selected as design variables. Refined response surface method through design space transformation technique was developed and employed, and high confidence level of the regression model could be obtained. Genetic algorithm was implemented for both system optimizer and subspace regression model optimization. Virtual nozzle was located at the end of throat to adjust the back pressure. With only 20 aerodynamic analyses, optimal supersonic diffuser shape which has 14% improved total pressure recovery characteristics was successfully designed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.881-884
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• 2011

Secondary throat supersonic exhaust diffusers were designed by Normal-shock theory and manufactured. Experimental studies of the diffusers were performed using nitrogen gas of room temperature. It showed a difference about 18% between the experimental and theoretical results. The difference was shown by friction loss at the wall of the diffuers.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.475-478
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• 2012

In this study, preliminary design of a high-altitude test facility (HATF) was performed to simulate the high-altitude environment using a rocket engine that liquid oxygen and kerosene were used as the propellant. Experimental facility consists of vacuum chamber, supersonic exhaust diffuser, heat exchanger, ejector and gas generator. The vacuum chamber was simulated and maintained high-altitude environmental pressure by supersonic exhaust diffuser. Combustion gas of the rocket engine was cooled by water at heat exchanger after that the mixed gas was emitted to the air by ejector. The ejector which was operated by the steam generator using 75% ethanol and liquid oxygen as propellants and water for steam maintains a vacuum condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.279-288
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• 2014

Second throat supersonic exhaust diffusers (STEDs) were designed to simulate high-altitude conditions according to the normal-shock model. Experimental studies were performed on the STEDs to investigate how performance characteristics varied with the length and diameter of the STED using high-pressure nitrogen gas. The variation in performance due to length indicated that the performance of the STED could be very slightly improved by adjusting the diffuser inlet length ($L_d$), and it could be significantly improved by optimizing the second throat length ratio ($L_{st}/D_{st}$) and the divergence length ($L_s$). The starting and vacuum chamber pressures exhibited the highest level of performance near ($A_d/A_{st}$) of the design point.