• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.128-133
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• 2006

Influence of changing combustor pressure on flame stabilization and nitrogen oxide (NOx) emission in the swirl-stabilized flame with secondary fuel injection was investigated. The combustor pressure was controlled by suction at combustor exit. Pressure index ($P{\ast}=P_{abs}/P_{atm}$), where $P_{abs}$ and $P_{atm}$ indicated the absolute pressure and atmosphere pressure, was controlled in the range of $0.7{\sim}1.3$ for each equivalence ratio conditions. The flammable limits of swirl flames were largely influenced by changing combustor pressure and they showed different tendency compared with laminar flames. Emission index showed maximum value near atmospheric condition and decreased with decreasing pressure index for overall equivalence ratio conditions. R.m.s of pressure fluctuations also showed similar tendency with nitric oxide emission. By injecting secondary fuel into flame zone, the flammable limits were extended significantly. Emission index of nitric oxide and r.m.s. of pressure fluctuations were also controlled by injecting secondary fuel. The swirl flames were somewhat lifted by secondary fuel with high momentum, hence low nitric oxide emission. This NOx reduction technology is applicable to industrial furnaces and air conditioning system by adopting secondary fuel injection.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.686-691
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• 2010

Flash boiling takes place when the thermodynamic state of the liquid deviates from its saturation limit over which the liquid temperature exceeds by a certain degree of superheat. The liquid jet introduced into the lower pressure zone than the liquid saturation pressure experiences a sequence of the atomization and disintegrated into numerous faster and smaller droplets. In the present study spray characteristics for a flash swirl spray were experimentally investigated. Injectant temperature is raised by a high frequency dielectric heating method and local spray characteristics are instantly measured by Global Sizing Velocimetry (GSV, TSI Inc.). Dependence of dimensionless superheat degree and injection pressure on total and local SMDs and mean droplet size is quantitatively examined. The flash swirl spray has the relation in the injection pressure and nozzle diameter in order to determine the spray quality, including the dimensionless superheat degree. Small droplets occur in the void core and local droplet size distributions largely depend on the dimensionless superheat degree and the injection pressure.

• 한국추진공학회지
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• 제7권2호
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• pp.62-69
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• 2003

Swirl형 인젝터는 연소가 안정적이고 효율이 높으며 비교적 넓은 구간의 혼합비 변화에 민감하게 반응하지 않는 장점을 가지고 있다. 바깥쪽 오리피스 끝단에서 안쪽 오리피스 끝단까지의 길이인 Recess 길이는 Swirl형 인젝터 성능의 주요 변수로, 추진제의 충돌, 혼합, 분무, 연소에 많은 영향을 준다. 이에 본 연구에서는 Recess 길이에 따라 엔진의 성능이 어떻게 변화하는지에 대해 수치해석, 비연소 실험, 연소 실험을 통해 확인해 보았다. 그 결과 Recess 길이에 따른 로켓엔진의 성능 변화를 확인 할 수 있었고, 인젝터의 성능을 평가하는 과정에서 수치해석, 비연소 실험을 통한 성능 예측이 연소실험을 통해 타당한 과정임을 확인 할 수 있었다.

• 한국표면공학회지
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• 제36권1호
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• pp.69-73
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• 2003

The atmospheric pressure plasma is regarded as an effective method for surface treatments because it can reduce the period of process and doesn't need expensive vacuum apparatus. The performance of non-transferred plasma torches is significantly depended on jet flow characteristics out of the nozzle. In order to produce the high performance of a torch, the maximum discharge velocity near an annular gap in the torch should be maintained. Also, the compulsory swirl is being produced to gain the shape that can concentrate the plasma at the center of gas flow. In this work, the distribution of gas flow that goes out to atmosphere through a plenum chamber and nozzle is analyzed to evaluate the performance of atmospheric pressure plasma torch which can present the optimum design of the torch. Numerical analysis is carried out with various angles of an inlet flow velocity. Especially, three-dimensional model of the torch is investigated to estimate swirl effect. We also investigate the stabilization of plasma distribution. For analyzing the swirl in the plenum chamber and the flow distribution, FVM (finite volume method) and SIMPLE algorithm are used for solving the governing equations. The standard k-model is used for simulating the turbulence.

• 한국추진공학회지
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• 제15권5호
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• pp.66-71
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• 2011

고압의 주위 압력 영역에서 토모그래피 기법을 이용하여 분무의 단면을 계측하였다. 구성된 분무 단면은 간접촬영방법을 이용한 이미지와 함께 비교되어 분무 단면의 크기를 확인하였고 토모그래피에 의해 재구성된 단면의 경계를 설정할 수 있었다. 이를 통해 고압의 주위 압력 영역에서도 토모그래피를 적용하여 분무를 구성할 수 있다는 것을 확인하였다.

• 한국전산유체공학회지
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• 제5권3호
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• pp.1-7
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• 2000

In high-pressure diesel engine, the injected fuel spray impinges on the piston cavity surface due to the short distance between the injection nozzle and the cavity wall. The behavior of the impinging spray has the great influence on the dispersion of fuel, the evaporation, and the mixture formation process. In this study, the numerical simulation using the GTT code was performed to study the gas flows, the spray behaviors, and the fuel vapor distributions in the combustion of a D.I engine for variation of spray angle and swirl ratio.

• 한국전산유체공학회지
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• 제12권3호
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• pp.8-12
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• 2007

An optimized bidet nozzle design to form the required swirl water jet is proposed with the help of numerical analysis. The bidet can do the cleaning process of human body by water injection and the speed/pressure/injection angle/magnitude of swirl intensity of water jet determine the cleaning capability and personal subjective feeling. The objective of this research is to design optimal water injection nozzle to make stable swirl intensity. The effect of individual design variables are analyzed from the basic design and the final design is deduced to make high performance water jet within the pre-determined operation conditions.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.3-10
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• 2002

In this work, numerical parametric studies on spray combustion have been conducted. In simulation of turbulence, RNG ${\kappa}-{\varepsilon}model$ is adopted. Initial spray distribution is specified by Rosin-Rammler distribution function. Eddy break-up model is adopted as a combustion model. The parameters considered are inlet air temperature, swirl number, and SMD. With higher inlet air temperature, the axial velocities are increased and penetration of primary jet is stronger than that of lower inlet air temperature and temperature at the exit of combustor is more uniform. Combustion efficiency is improved with high inlet air temperature. The effect of swirl number on flow field is not significant. It affect only recirculation zone. So temperature at upstream of combustor is influenced. Combustion efficiency deteriorate as SMD of fuel spray increase.

• 한국분무공학회지
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• 제19권4호
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• pp.167-173
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• 2014

The spray characteristics of Gas-Centered Swirl Coaxial Injector was investigated that there were different characteristics with or without gas flow. As gas flow was accelerated, the momentum of gas was transferred to the momentum of liquid in the low liquid Reynolds number. Therefore, the axial velocity of liquid was increased and the measured value was smaller than without gas flow. However, in the high momentum flux ratio, the momentum transfer hardly occurred and the results had constant values. As the recess length was increased, the mixing area of gas and liquid also was increased, the results were decreased.

• 대한기계학회논문집B
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• 제22권7호
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• pp.937-945
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• 1998

The purpose of this paper is to investigate the relationship between pressure recovery and turbulent characteristic value of velocity and pressure, in the case where a swirling flow streams into a conical diffuser. The results of both measurements of the wall pressure fluctuation and velocity fluctuation revealed them to role the large part of the total pressure loss of the flow. The cause of the fluctuation of flow was showed to be the flow separation at the inlet of diffuser at low intensity of swirl, but the flow of diffuser center was instable at high intensity of swirl. The static pressure recovery depends strongly on the magnitude of the turbulent energy in the diffuser, and that this magnitude of the turbulent energy varies as the intensity of swirl at the diffuser inlet.