• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.967-972
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• 2013

A MILD (Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of coanda nozzle geometrical parameters, nozzle passage gap length, nozzle passage length, nozzle angle and expansion length. The optimal configuration of coanda nozzle for the best entrainment flow rate was gap length, 0.5 mm, expansion angle, 4o and expansion length, 146 mm. The nozzle passage length was irrelevant to the exhaust gas entrainement.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.53-60
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• 2017

Various researches have been conducted for the reduction of NOx at the combustion furnace and exhaust gas recirculation method is commonly used technology for NOx reduction. The present research adopted coanda nozzles at the outside pipes of furnace to entrain the exhaust gas for the exhaust gas recirculation and the mixed gas was ejected to the tangential direction to cause the swirl flow in the furnace. The combustion flow characteristics in the exhaust gas recirculation burner with coanda nozzle has been elucidated by analyzing the swirl flow streamlines, temepraure and reaction rate distribution in the furnace. The exhaust gas entrained flow rate has been investigated by changing the excess air factor and coanda nozzle gap and the exhaust gas entrained flow rate increased with the increase of excess air factor and it decreased with the increase of coanda nozzle gap. The mean temperature at the exit plane of exhaust gas decreased with the excess air factor and it was little affected by the increase of coanda nozzle gap. The NOx mass fraction at the exhaust gas exit plane remarkably decreased with the excess air factor and it was also little affected by the increase of coanda nozzle gap.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.6
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• pp.569-578
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• 2008

The Coanda effects demonstrate that a jet stream applied tangential to a curved surface can generate lift force by increasing the circulation. Many experimental and numerical studies have been performed on the Coanda effect and it is found to be useful in various fields of aerodynamics. The Coanda effect may have practical application to marine hydrodynamics since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, numerical computations are performed to find the applicability of the Coanda effect to the marine control surfaces. For the purpose, changes in flow characteristics around a flapped foil due to the Coanda effect have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM). In the process, special attention has been given to the influence of jet nozzle arrangement on the lift characteristics of the Coanda foil. It is found that the shape as well as the location of the jet intake and jet exit affects the lift performance of the foil significantly.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.222-231
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• 1982

A single free jet formed by the interaction of two curved wall jets on a Cylinder surface is defined as "the Coanda nozzle jet" in this study. In order to investigate the characteristics of Coanda nozzle jet, an experimental analysis was carried out; measurements of the static pressure distribution on the cylinder surface, the mean velocity profile, the turbulence intensity, and the Reynolds shear stress by using x-type hot-wire probe.ire probe.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.8
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• pp.706-713
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• 2007

The jet structure issuing from a conventional convergent nozzle of variable expansion rate is compared with the result from the nozzle of a constant expansion rate using a normal type annular slit. In experiments, to investigate the jet characteristics between the two cases of jet, the mean velocity of nozzle exit is fixed to be 90m/s, the pressures along the jet axis and radial directions are measured by a scanning valve system moving with 3-axis auto-traverse unit, and the velocity distribution obtained by calculation from the measured static and total pressures is compared. Also to obtain the highly stable and convergence jets, it is turned out that the flow through a nozzle of constant expansion rate using the Coanda effect with an annular slit is the most preferable than that case through variable expansion rate nozzle. Furthermore, it is found that the pressure drop along the nozzle for the constant expansion rate nozzle is small relatively against to the case of variable expansion rate nozzle.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.65.2-65.2
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• 2005

• Journal of the Korean Institute of Gas
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• v.23 no.3
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• pp.1-6
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• 2019

The purpose of the present study is to elucidate flue gas recirculation device for reduction of nitrogen oxides using coanda nozzle without adopting additional power driving fan in a waste incinerator. The characteristics of the exhaust gas recirculation flow rate and the average temperature change at the outlet of the mixed gas were investigated according to the change of air supply nozzle gap and the position of air supply nozzle. When the gap of the air supply nozzle was changed to 3.22, 4.03, and 4.84 mm, the largest recirculation flow ratio, which is the ratio of exhaust gas recirculation flow rate and air supply flow rate, was 2.227 for the case with 3.22 mm and its mean temperature at outlet was $594.8^{\circ}C$. When the position of the air supply nozzle changes to the front position, neck position, and expansion position of the coanda nozzle neck, the recirculation flow ratios at the forward position and the neck position were nearly almost the same value, 1.843, and 1.696 at the expansion position, their mean temperatures were $559.8^{\circ}C$ and $544.3^{\circ}C$, respectively.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.152-158
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• 2016

Nitrogen oxide is generated by the chemical reaction of oxygen and nitrogen in higher temperature environment of combustion facilities. The NOx reduction equipment is generally used in the power plant or incineration plant and it causes enormous cost for the construction and maintenance. The flue gas recirculation method is commonly adopted for the reduction of NOx formation in the combustion facilities. In the present study, the computational fluid dynamic analysis was accomplished to elucidated the cold flow characteristics in the flue gas recirculation burner with coanda nozzles in the flue gas recirculation pipe. The inlet and outlet of flue gas recirculation pipes are directed toward the tangential direction of circular burner not toward the center of burner. The swirling flow is formed in the burner and it causes the reverse flow in the burner. The ratio of flue gas recirculation flow rate with the air flow rate was about 2.5 for the case with the coanda nozzle gap, 0.5mm and it was 1.5 for the case with the gap, 1.0mm. With the same coanda nozzle gap, the flue gas recirculation flow rate ratio had a little increase when the air flow rate changes from 1.1 to 2.2 times of ideal air flow rate.

• Journal of the Korean Institute of Gas
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• v.18 no.2
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• pp.21-27
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• 2014

A MILD(Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used a coanda nozzle for the exhaust gas recirculation in a MILD combustor. A numerical analysis was accomplished to elucidate the effect of exhaust gas entrainment toward the furnace with or without a coaxial contractor. The result of the present CFD analysis showed that the entrainment mass flow rate without a coaxial contractor had 18% larger than that with a coaxial contractor when the mixed gas outlet pressure was ambient pressure. On the other hand, if the outlet pressure increased, the mass flow rate with a contractor was larger than that without a contractor. It could be analysed by the entrainment driving force composed with the nozzle throat pressure, inlet and outlet pressures and flow cross sectional area.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.543-552
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• 2010

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coanda jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient $C_j$ = 0.1 and the rudder angle ${\alpha}=10^{\circ}$.