• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.1-7
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• 2010

Dual throat nozzle(DTN) is recently attracting much attention as a new concept of the thrust vectoring technique. This DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze a fundamental performance of a dual throat nozzle(DTN) at various nozzle pressure ratios(NPR) and throat area ratios. Two-dimensional, axisymmetric, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. NPR was varied in the range of NPR from 2.0 to 10.0, at different throat area ratios. The present computational results were validated with some experimental data available. Based upon the present results, the performance of DTN is discussed in terms of the discharge coefficient and thrust efficiency.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.72-78
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• 2005

We conducted the performance test of micronozzle having nozzle throat diameter of 1.0, 0.5, 0.25 mm in an ambient pressure. We used N2 gas as a cold gas propellant. We varied chamber pressure from 2 to 20 bar and measured the thrust and mass flow rate. Through the test, we concluded that viscous losses were increased with decreasing chamber pressure. We found that micronozzle performance was higher than orifice performance through thrust comparison.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.9-17
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• 2013

A considerable deal of work has been carried out to get an insight into the gas-solid suspension flows and to specify the particle motion and its influence on the gas flow field. In this paper an attempt is made to develop an analytical model to study the effect of nozzle inlet/exit pressure ratio, particle/gas loading and the particle diameter effect on gas-solid suspension flow. The effect of the particle/gas loading on the mass flow, Mach number, thrust coefficient and static pressure variation through the nozzle is analyzed. The results obtained show that the presence of particles seems to reduce the strength of the shock wave. It is also found that smaller the particle diameter is, bigger will be the velocity as bigger particle will have larger slip velocity. The suspension flow of smaller diameter particles has almost same trend as that of single phase flow with ideal gas as working fluid. Depending on the ambient pressure, the thrust coefficient is found to be higher for larger particle/gas loading or back pressure ratio.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.19-28
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• 2017

Effects of cavitation and hydraulic flip in circular and elliptical nozzles on the flow characteristics have been studied. Spray tests were conducted using injectors with different ratios of an orifice length(L) to a diameter(d) and of a major axis diameter(a) to a minor axis diameter(b). With the increment of an injection pressure drop, discharge coefficients slightly decreased in cavitation flows, and those suddenly dropped and were almost constant in hydraulic flip flows. For elliptical nozzles with L/b > 8 and L/a < 8, discharge coefficients and flow patterns showed different results from those in previous circular nozzles. When a flow in the elliptical nozzle was under steady condition, as the liquid column went downstream from the nozzle, its spray angle a little decreased in the plane of a major axis and increased in the plane of a minor axis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.27-31
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• 2003

An experimental investigation for impingement of under-expanded, axisymmetric jets on a flat plate has been conducted, and the surface pressure, the adiabatic wall temperature distributions on the plate have been measured in detail at small nozzle-to-plate distances. the pressure ratio and the nozzle-to-plate distance have been considered as experimental parameters.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.915-920
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• 1998

본 논문에서는 반구형 헤드(hemi-spherical head)를 가진 압력용기에 비방사형(non-radial) 노즐을 가공할 경우, 개구(opening) 간격이 반구형 헤드의 설계에 미치는 영향을 검토하기 위하여 개구 간격의 변화에 따른 응력분포변화를 분석하였다. ASME 코드는 NB-3222.4(d)의 설계 조건을 만족하는 압력 용기의 혜드에 노즐을 가공할 경우, NB-3338.2(d)에서 개구사이의 최소거리를 제시하고 있다. 본 논문에 서는 ASME 코드가 제시하고 있는 개구사이의 최소거리의 타당성과 설계상 이 요건을 만족하지 못하는 경우에 대하여 분석하고 검토하였다. 해석모델은 한국 표준형원자로의 가압기를 기본모델로하여 개구사이의 간격변화에 따른 응력변화를 검토하고, 설계시 고려하여야할 인자를 분석하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.53-61
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• 1999

Impinging jets are observed when exhaust gases from missiles or V/STOL aircrafts impinge on the ground, flame deflector, ship deck, etc. The flow shows different patterns according to the nozzle geometry, nozzle-to-plate distance, and plate angle, for example. This paper describes experimental works on the phenomena (pressure distribution, occurrence of stagnation bubble, and so on.) when underexpanded supersonic jets impinge on a perpendicular flat plate using a supersonic cold-flow system, and compares the results with those obtained using a shock tunnel. The flow characteristics for the supersonic cold-flow system were also investigated. Surface pressure distribution of supersonic cold-flow system differed from that of shock tunnel because of water and temperature in the low-pressure chamber. Surface pressure distribution as to underexpanded ratio showed similar patterns together.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.119-122
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• 2005

Ablation phenomena is very complicated because it includes momentum, energy and mass transfer, chemical reactions as well as phase change. In this paper, ablation at the rocket nozzle throat is modeled as unsteady one dimensional axi-symmetric with proper boundary conditions and field equation is solved numerically. Analytical results are compared with measured ablation data from firing experimental liquid rocket engine. Test variables are combustion pressure and mixture ratio. for low combustion pressure and low mixture ratio, the discrepancy between analysis and experiments are large but for the normal rocket operation range, two results show a simliar trend with maximum discrepancy of $100\%$.

• Journal of agriculture & life science
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• v.50 no.3
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• pp.119-127
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• 2016

The current disinfection method of vehicles being applied in South Korea has various shortcomings. So, the epidemic has generated continuously at livestock farms. It is very important to develop an effective disinfection system for reduction of the epidemic. And various basic data is required for this development. Therefore, this study was performed to identify the nozzle type and proper discharge pressure of sprayers. The experiment was conducted from January 10, 2012 until February 28, 2012. All the performance measurement experiments were repeated five times. The subjects of experiment were the A, B and C company's products. The sprayed capacity, angle of spray and the covering area ratio were measured for each product. As a result, the sprayed capacity, angle of spray and the covering area ratio were increased as the discharge pressure of the sprayer was increased. In conclusion, the conical shaped of the nozzle is considered more appropriate than V-shaped, and the proper discharge pressure is expected to be at least 20kg/㎠.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.349-352
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• 2008

Thrust vectoring control by injection of secondary jet inside a convergent-divergent supersonic nozzle was studied by both experimentally and computationally. For various stagnation pressure of the secondary jet injected at a specific location(12 mm-downstream of throat) in the divergent section of nozzle, the characteristics of thrust vectoring were observed. Present numerical results were compared with previous investigators' results and Schlieren flow visualizations for the identical boundary conditions, and it showed a qualitatively good agreement. It was also noticed that the characteristics of thrust vectoring is strongly related to the reflection structure of oblique shock inside nozzle, ie., the pressure ratio of the secondary jet, SPR.