• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.686-689
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• 2002

The application of the ultrasonic nozzle has been extended because it is possible atomization of liquid material. In this study, the characteristics of the ultrasonic nozzle and ceramic oscillator were investigated. The oscillator for the ultrasonic nozzle were made piezoelectric ceramic of $Pb[(Sb_{1/2}Nb_{1/2})_{0.035}-(Mn_{1/3}Nb_{2/3})_{0.065}-(Zr_{0.49}Ti_{0.51})_{0.90}]O_3$. The electromechanical coupling factor$(k_p)$ and mechanical quality factor$(Q_m)$ showed the values of 0.555, 1,214 respectively when the Zr/Ti ratio was 49/51. Moreover, this oscillator will have the temperature stability because it's curie temperature is $322[^{\circ}C]$. The driving current of ultrasonic nozzle showed the value of 80[mA] when the driving time was 10[min.]. Also, The surface temperature of ceramic oscillator showed $80[^{\circ}C]$ at driving time 10[min.] We knew that the ultrasonic nozzle had stabile driving above 10[min.].

• Journal of the Korean Society for Heat Treatment
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• v.5 no.3
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• pp.171-178
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• 1992

The effect of nozzle characterristics on the mist-cooling heat transfer was investigated under the various flow conditions. Two different types of twin fluid nozzle were used, one is a $90^{\circ}$ angle tip nozzle with needle and the other is a $90^{\circ}$ angle tip non-needle nozzle. The cooling rate from the heated surface was measured and obtained the boiling curve as a function of surface temperature. An immersion sampling was employed for the measurement of droplet size of the spray. As a result of this experiment, the liquid sheet type nozzle shows better atomization when the mass ratio Mr>2.0, and collects more liquid droplets on the heated surface that results in better cooling effect. It was found that the maximum heat flux and heat transfer coefficient increased with increase in the volumetric flow rate, whereas the maximum heat flux decreased with increase in spray distance. The cooling effect depends upon the amount of collected droplet and droplet size, but it strongly depends upon the amount of collected droplet.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.68-75
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• 2017

Dual bell nozzle is a type of altitude compensation nozzle, which is a nozzle that minimize the losses of the specific impulse at the off-design point of a typical bell nozzle. In this paper, numerical computations are performed to understand the transition characteristics of dual bell nozzles with fixed expansion ratios. The major design variables are the length of extension and the angle of inflection. As the length of the extension increased, the transition altitude and transition duration increased and the reduction of the thrust coefficient decreased. As the angle of inflection increased, the transition altitude and transition duration decreased and the reduction of the thrust coefficient increased.

• Current Industrial and Technological Trends in Aerospace
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• v.9 no.1
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• pp.139-149
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• 2011

The combustion chamber and nozzle of a liquid rocket engine need thermal protection against the high temperature combustion gas. The nozzle extension of a high-altitude engine also has to be compatible with high temperature environment and several kinds of cooling methods including gas film cooling, ablative cooling and radiative cooling are used. Especially for an upper-stage nozzle extension having a large expansion ratio, the weight impact on the launcher performance is crucial and it necessitated the development of light-weight refractory material. The present survey on the nozzle extension materials employed in the liquid rocket engines of USA, Russia and European Union has revealed a trend that the heavier metals like stainless steels and titanium alloys are being substituted with light weight carbon fiber or ceramic matrix composite materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.200-203
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• 2000

The application of the ultrasonic nozzle has been extended because it is possible atomization of liquid material. In this study, the characteristics of the ultrasonic nozzle and ceramic oscillator were investigated. The oscillator for the ultrasonic nozzle were made piezoelectric ceramic of Pb[($Sb_{1/2}$ $Nb_{1/2}$)$_{0.035}$-($Mn_{1/3}$$Nb_{2/3}$)$_{0.065}$-($Zr_{0.49}$$Ti_{0.51}$)$_{0.90}$]$O_3$. The electromechanical coupling factor($k_p$) and mechanical quality factor(Qm) showed the values of 0.555, 1, 214 respectively when the Zr/Ti ratio was 49/51. Moreover, this oscillator will have the temperature stability because it's curie temperature is 322[$^{\circ}C$]. The driving current of ultrasonic nozzle showed the value of 80[mA] when the driving time was lO[min.]. Also, The surface temperature of ceramic oscillator showed 80[$^{\circ}C$] at driving time lO[min.] We knew that the ultrasonic nozzle had stabile driving above 10[min.].

• Journal of ILASS-Korea
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• v.24 no.3
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• pp.137-144
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• 2019

The Y-jet nozzle has benefits such as simple design and wide operating conditions. Because of these benefits, it is used in various combustion devices including industrial boilers. The most important variables in the design of the Y-jet nozzle are the mixing chamber length, the supply diameter of the liquid fuel and gas, and the exit orifice diameter. In addition, because of the use of a twin-fluid, optimized data is required depending on the spray condition. In this study, spray experiment was carried out under the pressure condition of 7 bar or more, which is the spraying condition used in industry. There was no change in flow rate with the length of the Y-jet nozzle mixing chamber, but the difference in SMD was confirmed. Adjusting the exit orifice diameter is most important to achieve the desired flow rate. Changes in the liquid and gas inlet port diameters ratio were found to be help improve the operating range and significant difference in SMD was observed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.844-854
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• 2017

The Expansion-Deflection(E-D) nozzle is a nozzle that has a performance gain through the altitude compensation effect by changing the effective area within the nozzle according to the altitude. An E-D nozzle has been known to reduce the length of the nozzle and achieve the payload gain of the launch vehicle. Due to the potential advantages of an E-D nozzle, related research has been carried out in the United Kingdom, Germany, Australia and Europe etc. In the UK, the flow characteristics of the E-D nozzle and the performance comparison with the dual-bell nozzle which is altitude compensation nozzle were studied. In order to understand the transition characteristics of the E-D nozzle in DLR, the transition characteristics according to the nozzle pressure ratio change were analyzed. In Europe, numerical study using the E-D nozzle concept on upper stage of the launch vehicle Ariane 5 ESC-B was carried out to confirm the possibility of payload gain according to the nozzle length reduction. In this paper, research trends of an E-D nozzle performed outside the country are classified and analyzed according to their characteristics and utilized as basic data of E-D nozzle research in the future.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.630-638
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• 2009

A computational fluid dynamics(CFD) model is developed and validated with on-site experiments for a urea-based SNCR(selective non-catalytic reduction) process to reduce the nitrogen oxides($NO_x$) in a municipal incinerator. The three-dimensional turbulent reacting flow CFD model having a seven global reaction mechanism under the condition of low CO concentration and 12% excess air and droplet evaporation is used for fluid dynamics simulation of the SNCR process installed in the incinerator. In this SNCR process, urea solution and atomizing air were injected into the secondary combustor, using one front nozzle and two side nozzles. The exit temperature($980^{\circ}C$) of simulation has the same value as in situ experiment one. The $NO_x$ reduction efficiencies of 57% and 59% are obtained from the experiment and CFD simulation, respectively at NSR=1.8(normalized stoichiometric ratio) for the equal flow rate ratio from the three nozzles. It is observed in the CFD simulations with varying the flowrate ratio of the three nozzles that the injection of a two times larger front nozzle flowrate than the side nozzle flowrate produces 8% higher $NO_x$ reduction efficiency than the injection of the equal ratio flowrate in each nozzle.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.285-288
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• 2014

Experiments have been performed for the burners used in the non-oxidizing direct fired furnaces for the cold rolled plate to investigate the effect of fuel/air mixing patterns of the burner nozzle on flame shape, temperature and combustion gas concentration. CFD simulation has also been performed to investigate the mixing state of air-fuel for a nozzle mixing burner and a partially pre-mixing burner. A partially pre-mixing burner showed that flame temperature increased up to $26^{\circ}C$ on average compared than that of the nozzle mixing. It also showed that the mixing distance is important at the partially pre-mixing burner. Test results for a partially pre-mixing burner showed that the residual oxygen concentration and the volume ratio of $CO/CO_2$ of the flame were applicable to be used in field furnaces.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.289-292
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• 2008

Highly over-expanded nozzle of the rocket engines will be excited by non-axial forces due to flow separation at sea level operations. Since rocket engines are designed to produce axial thrust to power the vehicle, non-axial static and/or dynamic forces are not desirable. Several engine failures were attributed to the side loads. Present work investigate the unsteady flow in an over-expanded rocket nozzle in order to estimate side load during a shutdown/starting. Numerical computations has been carried out with density based solver on multi-block structured grid. Present solver is explicit in time and unsteady time step is calculated using dual time step approach. AUSMDV is considered as a numerical scheme for the flux calculations. One equation Spalart-Allmaras turbulence model is selected. Results presented here is for two nozzle pressure ratio i.e. 100 and 20. At 100 NPR, restricted shock separation (RSS) pattern is observed while, 20 NPR shows free shock separation (FSS) pattern. Side load is observed during the transition of separation pattern at different NPR.