• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.399-405
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• 2002

This paper proposes a new type of piezoactuator-driven valve system. The piezoceramic actuator bonded to both sides of a flexible beam surface makes a movement required to control the pressure at the flapper-nozzle of a pneumatic valve system. After establishing a dynamic model, an appropriate size of the valve system is designed and manufactured. Subsequently, a robust H$_{\infty}$ control algorithm is formulated in order to achieve accurate tracking control of the desired pressure. The controller is experimentally realized and control performance for the sinusoidal pressure trajectory is presented in time domain. The control bandwidth of the valve system, which directly represents the fastness, is also evaluated in the frequency domain.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2509-2512
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• 2005

In this paper, a position control scheme of the ink droplet is presented for the high image quality and print speed inkjet printer. The proposed scheme estimates the impact position and compensates it by control of the fire strobe time based on the dynamic equations describing the moving trajectory of the ink droplet. Compared to the conventional fire strobe control which is based on the simple synchronization the fire strobe with the position signal of the inkjet nozzle, the proposed control scheme provides more accurate impact position control during the carrier is moving with accelerated or decelerated speed as well as constant speed. The availability of printing during the acceleration and deceleration states of the carrier moving enables the print speed up and the frame size down which means the cost down.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.673-678
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• 2001

This paper proposes a new type of piezoactuator-driven valve system. The piezoceramic actuator bonded to both sides of a flexible beam surface makes a movement required to control the pressure at the flapper-nozzle of a pneumatic valve system. After establishing a dynamic model, an appropriate size of the valve system is designed and manufactured. Subsequently, a robust $H_{\infty}$ control algorithm is formulated in order to achieve accurate tracking control of the desired pressure. The controller is experimentally realized and control performance for the sinusoidal pressure trajectory is presented in time domain. The control bandwidth of the valve system, which directly represents the fastness, is also evaluated in the frequency domain.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.85-90
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• 2011

Recently, many high elevation fountain are constructed for the beauty of beach landscape. Typically, a fountain has several nozzles that shoots water upwards or at an angle into the air. But unfortunately, the weather and wind can cause the water soak nearby walkways and pedestrians. Therefore, in this study, a mathematical model of high elevation fountain is suggested to predict the actual travelling distance of water droplet by the wind. To simplify our treatment of the water flow and to avoid issues such as fluid dynamics and surface tension, we have adopted a particle model for the fountain water. The particles are assumed not to interact with each other, and do not deform during their flight through air.

• Journal of the Korean Society of Combustion
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• v.16 no.2
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• pp.40-46
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• 2011

The diesel pre-heater has being used in cabin heating and coolant heating of engine to reduce the engine warm up time for commercial vehicle. The pre-heaters are classified as diesel spray combustor and it forms diffusion flame. By using swirler, a recirculation flow of hot product gases is established near the fuel nozzle and it helps the maintaining of diffusion flame. The design difference of swirler can affect on reaction characteristics and temperature distribution inside pre-heater. The purpose of this study is the investigation of the effect of swirler configuration on combustion characteristics. To solve spray combustion problem, the Euler-Lagrange approach discrete model is used to track droplet trajectory and evaporation history. The PDF equilibrium model is used for chemical reaction model. These models are implemented into the FLUENT code.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1727-1734
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• 2011

In this paper, a position control scheme of the ink droplet is presented for the high image quality and print speed ink jet printer. The proposed scheme estimates the impact position and compensates it by control of the jet strobe time based on the dynamic equations describing the moving trajectory of the ejected ink droplet. Compared to the conventional jet strobe control which is based on the simple synchronization with the position signal of the ink jet nozzle, the proposed control scheme provides more accurate impact position control while the carrier is moving with accelerated or decelerated speed as well as steady state speed with fluctuations. The availability of printing during the acceleration and deceleration states of the carrier moving enables the print speed up and the frame size down which means the cost down.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.1-10
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• 2018

This study investigated the acoustic forcing effects on the liquid column breakup length and the trajectory of liquid jets in crossflows. Cold-flow tests with a single hole circular nozzle injector were carried out by changing the injection pressure and acoustic forcing amplitude. Additionally, spray images were obtained at 12 phase angles to investigate the influence of the phage angle. The results revealed that the liquid column breakup lengths generally decreased under the acoustic forcing conditions, in comparison to those under the non-acoustic forcing conditions. However, they were not affected by the variation in the phase angles. On the contrary, it was found that the acoustic forcing hardly influenced the liquid column trajectories.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.70-77
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• 2014

In this paper, the development of unique model of the 2.75 inch rocket propulsion system is described. Recently developed korean 2.75 inch rocket propulsion system shows the improvement of a flame stability resulted from a change in the configuration of propellant grain, and of an incidental ignition protection function using the EMI(electromagnetic interference) filter on ignition system. Moreover it is shown that a directional flight stability is improved by increasing the number of fins and changing the nozzle configuration. Static firing test and thermal shock test were conducted for the validation before flight, and flight test of 210 rounds of rockets was conducted to verify the trajectory uniformity. In addition, intellectual property issues can be overcome with the unique korean 2.75 inch rocket motor as well as the performance improvement.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.6
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• pp.62-73
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• 2022

This research proposes a method to control combustion instability in a gas turbine combustor having an annular combustor form and compares the effect of flow symmetric braking through nozzle arrangement and the corresponding change in equivalent ratio. To this end, the symmetry breaking effect was confirmed through mode analysis of FFT, Time signal, and phase trajectory. In addition, the unstable area and the stable area were identified through mode analysis, and this was shown on the contour map. The present research shows that instability occurs when the equivalent ratio and the arrangement of the nozzles are symmetry or when the nozzles are continuously arranged, but if the arrangement and equivalent ratio are not symmetry, the combustion instability decreases dramatically even if the difference in the equivalent ratio is small.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.75-81
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• 2009

A study was performed to investigate the characteristics of two-phase jet injected into subsonic cross-flow using the external mixed gas blast two-phase nozzle. The shadowgraph method was adopted for the cross-flow jet visualization and PDPA system was used to measure droplet size, velocity, and volume flux. The atomization of two-phase jet is initially determined according to gas to liquid mass flow-rate ratio and the Reynolds number of cross-flows. The highest penetration trajectories of two-phase jet injected into cross-flow are governed by the momentum ratio at subsonic cross-flow. As GLR of two-phase jet injected into cross-flow increases, the droplet size decreases and the distribution area of volume flux increases. The distribution of volume flux that influenced by the counter vortex pair at the downstream of cross-flow is symmetric in shape of horseshoe.