• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.295-298
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• 2007

The effectiveness of passive control techniques for reducing the pressure oscillation generated in a supersonic cavity flow was investigated numerically and experimentally, respectively. The control device includes a sub-cavity installed in the upstream edge of a rectangular cavity. Time-dependent supersonic cavity flow characteristics with turbulent features were examined by using the three-dimensional, mass-averaged Navier-Stokes computation based on a finite volume scheme and large eddy simulation. The results show that the pressure oscillation near the trailing edge dominates overall time-dependent cavity pressure variations. Such an oscillation can be attenuated more significantly in the presence of the sub-cavity compared with the cavity without sub-cavity, and a larger sub-cavity leads to better control performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.18-23
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• 2018

For the control of pre-burner combustion pressure, the open angle of the TTR (Throttle for Thrust Regulation) valve was varied from $143^{\circ}$ to $185^{\circ}$ while testing cold flow, ignition, and combustion. The major performance variables of rocket engines and hydraulic performance of the TTR valve regarding the open angle were verified. However, the controllability of pre-burner combustion pressure was not verified due to the limitations of the test. Comprehensive research will be done after addressing these problems.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.403-412
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• 2001

The Present study analyzed the pressure-flow characteristics of a Korean shunt valve. Changes in the characteristic currie depending on the design parameters were also investigated. The Korean shunt valve used in the present study was constant pressure type and our analyses were validated through experiments. We applied fluid-structure interaction to solve the flow dynamic Problem because the small diaphragm in the valve was made from flexible silicone elastomers. Considering the material nonlinearity of the hyper-elastic material. the Mooney-Rivlin approximation was employed. The results of the numerical analyses were close to the experimental results The major Pressure drop was observed to happen in the small diaphragm. The slope of the pressure-flow characteristic curve was computed to be 0.37mm$H_2O$.hr/cc, which was similar to the average value of commercial shunt valves. 0.40mm$H_2O$.hr/cc. Therefore. our valves analyzed in the Present study showed a Proper Pressure control characteristics of the constant pressure type shunt valves. The opening pressure could be controlled by adjusting the amount of predeflection of the valve diaphragm. In order to obtain opening pressures of 25mm$H_2O$ and 80mm$H_2O$, respectively, and the required predeflection was found to be 10.2$\mu$m and 35.3$\mu$m. The flow orifice size was found to be within 10$\mu$m during valve operation Therefore, Precision design and manufacturing techniques are necessary for successful operations of the shunt valve. The study indicated the amount of predeflection as well as the magnitude of corner rounding of the diaphragm edge are important design parameters to influence the slope of the pressure-flow characteristic curve.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.208-215
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• 2016

To control and improve a combustion behavior of an engine, various studies for the in-cylinder pressure have been consistently carried out. In this paper, the level of the combustion noise for a diesel engine is estimated from the in-cylinder pressure and defined as the combustion noise index. The combustion noise index is calculated from the FFT(Fast Fourier Transform) of the in-cylinder pressure and its validity is verified. The control system based on the combustion noise index is developed and implemented in a vehicle. A number of injection parameters are controlled to meet the desired combustion noise index, and the combustion noise of a vehicle is improved up to 4.0 dB(A) in the specified frequency band.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.89-95
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• 2021

Pressure sores are an unresolved human challenge. In this study, a keyboard-type medical bed was developed and a body pressure sensor was installed to provide a method to control the keyboard so that the pressure sores do not reach the critical pressure. For this, a keyboard-type mattress using a 4bar link is developed, and a method of controlling the height adjustment of the keyboard within the critical pressure through a body pressure sensor is used. There is a feeling of discomfort in the body when the keyboard is raised and lowered from pressure sores, which is an important factor: pressure x time, and only time control is performed, but if the proposed method is used, pressure is controlled within the critical pressure, thereby preventing bedsores in a comfortable state. The effectiveness and validity of the developed medical bed system were verified through theories and experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.18-24
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• 2006

Passive control of the shock wave/turbulent boundary-layer interaction utilizing slotted plates and a porous plate over a cavity has been carried out. Effect of various slot configurations on the characteristics of the interaction has been observed. Pitot/wall surface pressure distributions and flow visualizations including Schlieren images, kerosene-lampblack tracings and interference fringe patterns over a thin oil-film have been obtained at the downstream of the shock interactions. For the streamwise-slot configuration, a local higher pitot pressure was noticed at the downstream of the interaction as compared with the case of no control, however, not much improvement in pitot pressure was observed for the spanwise-slot configuration.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.145-151
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• 2004

In this paper, a pressure control type ratio control valve(RCV) is designed for a metal belt CVT. Steady state and transient characteristics of the pressure control CVT are investigated by simulations and experiments. In addition, P-line is proposed to predict the shift performance. It is found that the bigger the pressure margin, the faster the shift response. It is expected that the P-line can be used in design of the RCV to meet the desired shift performance.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.206-211
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• 1992

A mathematical model of the blow-down type wind tunnel is developed in order to design the controller which controls the stagnation pressure being used to obtain the setpoint Mach Number. The motion of compressible fluids in the tunnel is modeled using the one-dimensional gasdynamics. The time responses of the wind tunnel states, such as pressures, mass flow rates, and valve open area, are investigated by digital computer simulation. By the simulation study it is shown that the real blow-down wind tunnel can be simulated by the obtained mathematical model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.291-298
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• 2013

In this paper a new hybrid-type control system is proposed which reduces the pump speed of an electro-hydraulic actuator consisting of a pressure-compensated variable displacement piston pump and a valve-controlled hydraulic cylinder, whenever the flow rate demand is low. In order to avoid interfering with the pressure regulator which also has an effect on swash plate angle, the pump speed is changed in proportion to the mean value of the speed component of position commands. Additionally a pressure switch is employed to prevent the system pressure from getting lower than a reference value. Based on computer simulation & experimental results, it is shown that the hybrid control can save the idling power up to 44% at a stand-by mode by reducing the pump speed from 1,800 rpm to 600 rpm without affecting the dynamic response of the electro-hydraulic actuator.

• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.485-490
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• 2007

The purpose in having a control rod on a buoy system is to control the motion of it. The system may be composed entirely of a single circular cylinder and a long mooring anchor cable. A control rod has one function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of the effects of mutual interference. then determine the stability characteristics of the body. In this paper, the study of control-rod-attached buoy's 2-dimensional section was accomplished. model tests and numerical simulations had been carried out with different diameters of control rods. and varying the Reynolds number $Re=5,000{\sim}25,000$ based on the cylinder diameter(D=50mm) to predict the performance of the body and the 2 frame particle tracking method Iud been used to obtain the velocity distribution in the flow field. 50mm circular cylinder Iud been used during the whole experiments and measured results had been compared with each other.