• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.58-66
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• 1999

The flow characteristics of supersonic ejectors is often subject to compressibility, unsteadiness and shock wave systems. The numerical works carried out thus far have been of one-dimensional analyses or some Computational Fluid Dynamics(CFD) which has been applied to only a very simplified configuration. For the design of effective ejector-pump systems the effects of secondary mass flow on the supersonic ejector flow should be fully understood. In the present work the supersonic ejector-pump flows with a secondary mass flow were simulated using CFD. A fully implicit finite volume scheme was applied to axisymmetric compressible Navier-Stokes equations. The standard two-equation turbulence model was employed to predict turbulent stresses. The results obtained showed that the flow characteristics of constant area mixing tube types were nearly independent of the secondary flow rate, but the flow fields of ejector system with the second-throat were strongly dependent on the secondary flow rate due to the effect of the back pressure near the primary nozzle exit.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.1
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• pp.61-66
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• 2005

A theoretical analysis is developed for an annular-injection-type supersonic ejector having a second-throat downstream the ejector under the assumption that the Fabri choking is placed in mixing chamber. Non mixing theory is applied to formulate secondary flow pressure in the region between inlet of the mixing chamber and Fabri choking. To describe the shock standing at the inlet of the mixing chamber, two dimensional oblique shock relations are used and it is assumed that the shock affects only primary flow at Fabri choking plane. Physical constraint, which is that primary flow pressure and secondary flow pressure are same at Fabri choking plane, is added. In conclusion, it agrees well with experiments in case of small contracting angle of mixing chamber, under 4degrees.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.54-63
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• 2006

Ejector system are used to transport a low momentum flow to the higher pressure flow by the momentum change between high and low momentum flows. This system is used to simulate the high altitude and Mach number condition over altitude 20 km and Mach 4 of the supersonic test facility. We applied the design and the performance analysis technique(EISIMP code) of the Ramjet Test Facility(RJTF) air system in JAXA to the ejector system of the ramjet test facility in KARI. After preliminary design of the ejector system, we performed a computational study using FLUENT and investigated shock structures and flow characteristics of the ejector system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.9-15
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• 2005

From the geometric parameter study, an optimal ejector design procedure of pressure recovery system for chemical lasers was acquired. For given primary flow reservoir conditions, an up-scaled ejector was designed and manufactured. In the performance test, secondary mass flow rate of 100g/s air was entrained satisfying the design secondary pressure, $40{\sim}50torr$. Performance validation of a supersonic ejector system along with an investigation of effects of supersonic diffuser was conducted. Placement of the diffuser at the secondary inlet further reduced diffuser upstream pressure to 7torr. Lastly, the duplicate of apparatus (air 500g/s secondary mass flow rate each) was built and connected in parallel to assess proportionality behavior on a system to handle larger mass flow rate. Test and comparison of the parallel unit demonstrated the secondary mass flow rate was proportional to the number of individual units that were brought together maintaining the lasing pressure.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.23-29
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• 2006

In an annular injection supersonic ejector, the supersonic primary flow is injected along the side wall, therefore a funnel-shaped shock wave is generated by the contraction angle of the mixing chamber. In the present study, we developed a simple funnel shock wave model using 2-D wedge and conical shock wave relations. In result, the secondary flow pressure can be predicted more accurately than using a simple 2-D wedge shock wave model. Through the same analysis, the compression ratio and the adiabatic efficiency according to the entrainment ratio were calculated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.200-203
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• 2011

Supersonic ejectors are simple mechanical components, which generally perform mixing and recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for high altitude testing (HAT) of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser (SED). This paper aims at the improvement in HAT facility by focusing attention on the vertical firing rocket test stand with shock generators. Shock generators are mounted inside the SED for improving the pressure recovery. The results clearly showed that the performance of the ejector-diffuser system was improved with the addition of shock generators. The improvement comes in the form of reduction of the starting pressure ratio and the vertical height of test stand. It is also shown that shock generators are useful in reducing the total pressure loss in the SED.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.13-19
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• 2003

A supersonic ground test facility to develop Ramjet and SCRamjet(Supersonic Combustion Ramjet) engine should be able to simulate high altitude and high Mach number conditions including air total pressure, oxygen level and specific heat ratio at the combustion chamber entrance. The test facility also should simulate the effect of oblique shock wave caused by the flight vehicle. The test facility developed in this study is supersonic free-jet blowdown type, which consists of high pressure air supply source(maximum pressure=32MPa), air heater(vitiation type), supersonic diffuser, ejector, and test chamber(nozzle exit dimension=200mm$\times$200mm).

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.135-138
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• 2002

High-speed ejection of burnt gases from the resonator cavity is essential for performance optimization of the chemical laser system. Additionally, to maintain the population of lasing species at a level for maximum optical power, the pressure within the cavity must be of order of 10 torr. In the present study, a small-scale ejector was designed and built for parametric study of its performance. High-pressure air was used as a motive gas. Measurements include schlieren visualization and pressure distribution trace near the ejector nozzle and along the diffuser downstream of the ejector. preliminary tests showed performance of the ejector is a function of parameters including mass flow rate and stagnation pressure of the motive gas, ejector nozzle area ratio, throat area of the diffuser downstream of the ejector.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.4
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• pp.53-62
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• 2003

A supersonic ground test facility to develop Ramjet and SCRamjet(Supersonic Combustion Ramjet) engine should be able to simulate high altitude and high Mach number conditions including air total pressure, oxygen level and specific heat ratio at the combustion chamber entrance. The test facility also should simulate the effect of oblique shock wave caused by the flight vehicle. The test facility developed in this study is supersonic free-jet blow down type, which consists of high pressure air supply source(maximum pressure=32MPa), air heater(vitiation type), supersonic diffuser, ejector, and test chamber(nozzle exit dimension=200mm${\times}$200mm).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.405-408
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• 2005

A theoretical analysis is developed for an annular injection type supersonic ejector having a second-throat downstream under the assumption that the Fabri-chocking is placed in mixing chamber. Non-mixing theory is applied to formulate secondary flow pressure in the region between inlet of the mixing chamber and Fabri-chocking. To describe the shock standing at the inlet of the mixing chamber, two dimensional oblique shock relations are used and it is assumed that the shock affects only primary flow at Fabri-chocking plane. In conclusion, it agrees well with experiments in case of small contracting angle of mixing chamber, under 4degrees.