• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.335-338
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• 2010

A recent study for tracing the profiles of supersonic axisymmetric Minimum Length Nozzle with uniform and parallel flow at the exit section, the stagnation temperature is taken into account. The aim of this work is to add optimization algorithm to the supersonic nozzle design in order to get the optimum nozzle shape. The comparisons of the nozzle contours based on the method of characteristics are presented. The specific heats and their ratio vary with the stagnation temperature when this temperature of a perfect gas increases. An application is made for air in a supersonic nozzle.

• 한국분무공학회지
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• 제13권3호
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• pp.134-142
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• 2008

In the case of heavy duty diesel engines, the Urea-SCR system is currently considered to reduce the NOx emission as a proved technology, and it is widely studied to get the high performance and durability. However, the nozzles to inject the urea-water solution into the exhaust pipe occur some problems, including the nozzle clogging, deposition of urea-water solution on the inner wall of the exhaust pipe, resulting in the production of urea salt. In this study, a swirl-type twin-fluid nozzle to produce more fine droplets was used as a method to solve the problems. The effect of the nozzle cap geometry, including the length to diameter ratio ($l_o/d_o$) and chamfer, on the spray characteristics were investigated experimentally. The length to diameter ratio of nozzle cap were varied from 0.25 to 1.125. The chamfer angle of the nozzle cap was constant at 90o. The mean velocity and droplet size distributions of the spray were measured using a 2-D PDA (phase Doppler analyzer) system, and the spray half-width, AMD (arithmetic mean diameter) and SMD (Sauter mean diameter) were analyzed. At result, The larger length to diameter ratio of nozzle cap were more small SMD and AMD. The effect of the chamfer did increase the radial velocity, while it did not affect the atomization effect.

• 전기의세계
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• 제22권5호
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• pp.19-32
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• 1973

This paper treats with some of plasma jet behaviors under magnetic field for the purpose of controlling important characteristics of plasma jet in the practices of material manufacturings. Under the existence and non-existence of magnetic field, the pressure distribution, flame length, stability and noise of plasma jet are comparatively evaluated in respect of such parameters as are current, gap of electrode, quantity of argon flow, magnetic flux density, diameter and length of nozzle. The results are as follows: 1) the pressure, the length and the noise of plasma jet rise gradually with the increase of are current, and have high values under identical arc current as the diameter of nozzle increases, but reverse phenomenon tends to appear in the noise. 2) The pressure, the flame length and the noise increase with the increased quantity of argon flow, and the rising slope of noise is particularly steep. Under magnetic field, the quantity of argon flow in respect of flame length has the critical value of 80(cfh). 3) The pressure and length of flame decrease with small gradient value as the length of gap increases, but the noise tends to grow according to the increase of nozzle diameter. 4) The pressure and the length of jet flame decrease inversly with the increase of magnetic flux density, which have one critical value in the 100 amps of arc current and two values in 50 amps. The pressure of jet flame can be below atomospher pressure in strong magnetic field. 5) "The constriction length of nozzle has respectively the critical value of 6(mm) for pressure and 23(mm) for the length of flame. 6) Fluctuations in the wave form of voltage become greater with the increase of argon flow and magnetic flux density, but tends to decrease as arc current increases, having the frequency range of 3-8KHz. The wave form of noise changes almost in parallel with that of voltage and its changing value increases with argon flow, arc current and magnetic flux density, having the freuqency range of 6-8KHz. The fluctuation of jet presurre is reduced with the increase of argon flow and magnetic flux density and grows with arc current.rent.

• 한국구조물진단유지관리공학회 논문집
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• 제22권6호
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• pp.157-163
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• 2018

본 연구는 기존에 사용되어 지고 있는 타설 노즐 내부에 블레이드를 설치함으로써 타설 시 시멘트 복합체에 혼입된 섬유의 방향성을 제어하고 동시에 분포도를 향상시키고자 하였다. 블레이드 변수 최적화를 위하여 시멘트계 매트릭스 재료의 유동과 혼입된 섬유의 운동, 노즐간의 상호작용을 고려한 다중물리계 유한요소해석을 수행하였다. 사용되는 섬유길이를 변수로 하여 블레이드의 간격, 길이, 위치를 결정하였다. 내부 블레이드 간격이 섬유길이의 약 1.2~2.4배, 블레이드 길이는 섬유길이의 약 4~8배, 설치 위치는 시멘트 복합체가 도출되는 입구에서부터 섬유길이의 14배 이하일 때 섬유 방향각이 약 $15^{\circ}$이하로 제어되었다. 또한, 본 연구에서 제시된 블레이드형 노즐은 기존의 섬유보강 시멘트 복합체 타설장비와 타설관을 그대로 사용하면서, 탈 부착식으로 제작될 수 있어 사용성과 편의성을 동시에 제공할 수 있을 것으로 판단된다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.1-8
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• 2000

The effects of nozzle arrangements, nozzle distances and fuel flowrates on the flame stabilities such as flame length, liftoff height and blowout characteristics are investigated experimentally. Three nozzle arrangements - diamond 4 nozzle, linear 5 nozzle, cross 5 nozzle- are used. Flame interactions result in the increase of the blowout flowrates and constant turbulent liftoff heights. The flames separated about 10 nozzle diameters are sustained as nozzle attached flames to the higher fuel flowrates than the other separation cases. Normally flames are extinguished at the lifted states. Blowout flowrates are affected by the nozzle configuration, nozzle seperation distance. Blowout flowrates for the diamond- or cross- shaped nozzle arrangements are parabolic function of nozzle distances. Maximum blowout flowrates for the 5 nozzle configuration case except linear one is about 2.9 times that of single equivalent nozzle case. Turbulent liftoff heights are not function of flowrates for the interacting flames.

• 한국분무공학회지
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• 제4권1호
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• pp.55-61
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• 1999

The first maximum point in the stability curve of liquid jet, i.e., the critical point is associated with the critical Reynolds number. This critical Reynolds number should be predicted by simple means. In this work, the critical Reynolds number in the stability curve of liquid jet are predicted using the empirical correlations and the experimental data reported in the literatures. The critical Reynolds number was found to be a function of the Ohnesorge number, nozzle lengh-to-diameter ratio, ambient Weber number and nozzle inlet type. An empirical correlation for the critical Reynolds number as a function of the Ohnesorge number and nozzle length-to-diameter ratio is newly proposed here. Although an empirical correlation proposed in this work may not be universal because of excluding the effects of ambient pressure and nozzle inlet type, it has reasonably agrees with the measured critical Reynolds number.

• 설비공학논문집
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• 제13권3호
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• pp.209-216
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• 2001

A numerical study is peformed to investigate the effect of circumferential velocity generated by the guide vane on the nozzle flow of a jet fan, s a way of increasing the penetration force of jet fan with nozzle of 175mm diameter. For the validation of numerical results. the velocity is measured by a 5-hole pitot tube and flow visualization is conducted by the tuft method. Under the inlet condition that the maximum circumferential velocity in the stator outlet of the present jet fan is 1.8m/s, the axial velocity in the nozzle outlet has the feature that the velocity at the axis is low and the velocity near the wall high. Therefore, to increase the throw length of the jet fan, the configuration of the fairing and nozzle needs to be developed and the precise revise of the stator angle is required, In addition, the bigger the circumferential velocity, the smaller the axial velocity at the axis and the bigger non-uniformity of the flow distribution.

• 한국분무공학회지
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• 제11권1호
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• pp.24-29
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• 2006

Spray characteristics produced by conventional and electrostatic pressure-swirl nozzles for an oil burner have been studied, using kerosine as a test liquid. The charge injection mechanism is used to design the electrostatic nozzle, where specific charge density, breakup length, spray angle and mean diameter are measured and analyzed. Three nozzles with orifice diameters of 0.256, 0.308 and 0.333mm at injection pressures of 0.7, 0.9, 1.1 and 1.3 MPa are used in the study. In case of the electrostatic nozzle, voltages ranging from -5 to -12kV are applied. Comparison of the spray characteristics is made between the conventional and electrostatic nozzles. The results showed that, the electrostatic nozzle is superior to the conventional nozzle. This is due the effect of voltage on the liquid surface tension.

• 한국정밀공학회지
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• 제11권5호
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• pp.98-109
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• 1994

This paper is studied on the junction stress of the large tank and the cylindrical outlet such as a pressure vessel attached to a pope or nozzle theoretically. It is assumed that the diameter of tank is much larger than that of the nozzle cylinder, so it can be approximated that nozzle cylinder is attached to plate. As the current nozzle shape is manufactured as "Through Type" to reduce the stress concentration around the nozzle junction part of pressure vessel, a theoretical analysis on the cylinder with finite length should be performed to accomodate this fact. Each theoretical optimal values were obtained through the analysis of stress concentration caused by the variation of cylinder length and thickness, and these results were estimated by performing FEM Analysis. Analysis.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.13-17
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• 2009

Ejector is an equipment devised for making use of the low pressure occurring from the fast fluid injection and it is a transportation equipment which can obtain vacuum using the kinetic energy of the fluid. This ejector system is, nowadays, widely used for construction machinery, heavy equipments, the cooling and ventilation of electronic devices and for the various fluid transportation and pumps. In this study, it is attempted to perform a numerical analysis and an experiment to find out the characteristics of fluid quantity, velocity and the pressure distribution of the induction pipe by changing the length and the radius ratio of the nozzle of ejector. From the results, it is investigated that the distributions of velocity and pressure of induction pipe attached are changing with the length and the radius ratio of the nozzle. In addition, it is shown that for the small and large ejector, the efficiency is the maximum when the length of the nozzle arrived to the neck of the ejector, however, if it is installed at below or above the neck the efficiency is rather decreased.