• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.984-991
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• 2009

In this study, transonic aeroelastic response analyses have been conducted for the DLR-F4(wing-body) aircraft configuration considering shockwave and flow separation effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to wing-body configurations. In transonic flight region, the characteristics of static and dynamic aeroelastic responses have been investigated for a typical wing-body configuration model. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.58-64
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• 2006

This work focuses on reducing the noise and vibration levels of an LPi fuel pump, which are generated from the dynamic motions of pump elements and non-uniform flow of fuel. The noise and vibration levels increase as the revolution speed of the cam goes up. The fuel pump consists of five cavity cells, plungers and diaphragms, which are driven by the cam. The optimal design of the cam profile is performed to decrease the accelerations of moving Parts and to obtain a smooth hydraulic force through a dynamic analysis of a cam-plunger mechanism. The cam-Plunger with a cavity is modeled as a 2 degrees of freedom system having non-linear contacts, the cam profile being represented in terms of Fourier series in order to determine the optimal shape of the cam. From the optimized cam Profile, the acceleration of the diaphragm is reduced in $78\%$, the hydraulic force becoming smoother in case that the hydraulic force is rapidly dropped.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.32-37
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• 2007

Aerodynamic forces and moments have been used to control rocket propelled vehicles. If control is required at very low speed, Those systems only provide a limited capability because aerodynamic control force is proportional to the air density and low dynamic pressure. But thrust vector control(TVC) can overcome the disadvantages. TVC is the method which generates the side force and roll moment by controlling exhausted gas directly in a rocket nozzle. TVC is classified by mechanical and fluid dynamic methods. Mechanical methods can change the flow direction by several objects installed in a rocket nozzle exhaust such as tapered ramp tabs and jet vane. Fluid dynamic methods control the flight direction with the injection of secondary gaseous flows into the rocket nozzle. The tapered ramp tabs of mechanical methods are used in this paper. They installed at the rear in the rocket nozzle could be freely moved along axial and radial direction on the mounting ring to provide the mass flow rate which is injected from the rocket nozzle. In this paper, the conceptual design and the study on the tapered ramp tabs of the thurst vector control has been carried out using the supersonic cold flow system and schlieren system. This paper provides the thrust spoilage, three directional forces and moments and distribution of surface pressure on the region enclosed by the tapered ramp tabs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.784-794
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• 1998

The present study has been directed at developing thermal models to investigate the dynamic behavior of a solar cooling system including an absorption chiller, solar collectors, a hot water storage tank, a fan coil unit, and the air-conditioned space. The operation of the system was simulated for 8 hours in two different operation modes. In the mode 1, the system operated without any capacity control.0 the mode 2, an auxiliary boiler supplied heat to the generator if hot water temperature became lower than a certain value. Moreover, the mass flow rate of hot water to the generator was controlled by comparing the instantaneous room air temperature with the design value. The variation of temperature and concentration in the system components and that of heat transfer rates in the system were obtained for both modes of operation. It was found that the room temperature was maintained near the desired value in the mode 2 by supplying auxiliary heat or controlling the mass flow rate of hot water, while the deviation of room temperature was quite great in the mode 2.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.2
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• pp.78-85
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• 2010

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flow rate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.479-485
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• 2019

As exhaust gas systems of ships become more complicated, it is necessary to calculate an accurate pressure loss at their design stage. If the dynamic loss coefficients of non-standard fittings mainly used in exhaust gas pipe (EGP) are well-documented, it would be possible to calculate precise pressure loss more readily than using the conventional method that analyzes the entire system. In the case of a ship's EGP, the flow rates and temperatures of exhaust gas are determined by engine specifications, and the range of the flow rate and temperature is limited according to operating conditions. In addition, as it is possible to define non-standard fittings frequently used in an EGP, a database can be easily constructed and effective. This paper illustrates effective parameters and analysis cases of several types of non-standard fittings mounted in ship EGPs. The analysis procedure proposed in this paper is verified using existing research results on HVAC fittings. The numerical procedure, which is minimally affected by manpower and grid, is established such that it can be applied at the industry level.

• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.125-131
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• 2002

Respiratory air flow rate is necessarily measured for the pulmonary function evaluation. The currently used devices are exposed to the problems of measurement reliability and cross-patient infection. The present study introduced a new technique which converted the bidirectional air flow rate into averaged dynamic pressure based on the famous Bernoulli's energy conservation principle. Single use plastic sensing element was assembled within the flow tube(mouth piece) made of paper, which was named "functional single use flow tube". Experiment demonstrated only ${\pm}1.5%$ relative error in the standard 3L volume measurement procedure well within the error limit suggested by the American Thoracic Society(ATS). Disposable use design completely eliminated cross-patient infection. The present device is best useful and safe for clinical respiratory air flow measurement such as spirometry.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1006-1011
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• 2003

In this study, a novel systematic design procedure by Genetic Algorithm of a two stage relief valve is proposed. First of all, a mathematical model describing the dynamics of a balanced piston type relief valve has been derived. Governing equations such as dynamic equations for the main spool and the pilot spool and flow equations for each orifice are established. The mathematical model is verified by comparing the results of simulation with that of experiments. Furthermore, influences of the parameters on the dynamic characteristics of a relief valve have been investigated by simulation of the proposed model. Major design parameters on the valve response are determined, which affect the system response significantly. And then, using the determined parameters, the optimization of the two stage relief valve by Genetic Algorithm, which is a random search algorithm can find the global optimum without converging local optimum, is performed. The optimal design process of a two stage relief valve is presented to determine the major design parameters. Fitness function reflects the changing pressure according to parameters. It is shown that the genetic algorithms satisfactorily optimized the major design parameters of the two stage relief valve.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.501-506
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• 2002

In this study, a novel systematic design procedure by Genetic Algorithm of a two stage relief valve is proposed. First of all. a mathematical model describing the dynamics of a balanced piston type relief valve has been derived. Governing equations such as dynamic equations for the main spool and the pilot spool and flow equations for each orifice are established. The mathematical model is verified by comparing the results of simulation with that of experiments. Furthermore, influences of the parameters on the dynamic characteristics of a relief valve have been investigated by simulation of the proposed model. Major design parameters on the valve response are determined, which affect the system response significantly. And then, using the determined parameters, the optimization of the two stage relief valve by Genetic Algorithm, which is a random search algorithm can find the global optimum without converging local optimum, is performed. The optimal design process of a two stage relief valve is presented to determine the major design parameters. Fitness function reflects the changing pressure according to parameters. It is shown that the genetic algorithms satisfactorily optimized the major design parameters of the two stage relief valve.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.107-112
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• 2005

A cross-flow fan is generally used on the region within the low static pressure difference and the high flow rate. It relatively makes high dynamic pressure at low rotating speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. At off-design points, there are a rapid pressure head reduction, a noise increase and an unsteady flow. Those phenomena are remarkably influenced by the setting angle of a stabilizer. Therefore, it should be considered how the setting angle of a stabilizer affects on the performance and the flow fields of a cross-flow fan. It is also required to investigate the effect of the volumetric flow rate before occurring stall. Two-dimensional, unsteady governing equations are solved using a commercial code, STAR-CD, which uses FVM. PISO algorithm, sliding grid system and standard k - ε turbulence model are also adopted. Pressure and velocity profiles with various setting angles are graphically depicted. Furthermore, the meridional velocity profiles around the impeller are plotted with different flow rates for a given rotating speed.