• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.97-106
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• 1995

An improving example for traditional rapid mix system was studied in the base of mechanisms of alum coagulation. Local status of the major water treatment plants was also investigated and evaluated for upgrading these plants. A new design and operating criterium for rapid mix system was proposed to velocity gradient, G of $1,000-1,500sec^{-1}$ and detention time, t of 1 sec from the results of experiments and literature reviews. Comparing the present rapid mix system to this criterium, apparent difference existed between them. In this study, for improving Seongnam water treatment plant, a design criterium of velocity gradient, and detention time was set to $1,100sec^{-1}$, 1 sec, respectively. A new rapid mix system adopted the nozzle injection countcurrently cross the inlet pipe to the whole area. The injection velocity was 17m/s, nozzle diameter was 1.0mm, and number of nozzle was 70. The new modified system without running present four 75 HP agitators was able to improve water quality(based on sedimentation effluent) by 15-35% and to reduce electrical energy by 98%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.395-399
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• 2009

Advanced afterburner used in the most modernized gas turbine has new designing paradigm to cope with reinforced power density. The most distinct change is the designing trend to integrate fuel injectors and flame holder in order to manage higher temperature of inlet air. F414 and F110-GE-132 engine adopted this methodology and installed a variable nozzle utilizing CMC(Ceramic Matric Composite) material and active cooling of nozzle flap with ejector nozzle in order to enhance the life cycle of engine components and an economical aspect. These technological trends can be utilized for an advanced ramjet engine and combined cycle engine like TBCC.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.30-38
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• 2010

Experiments were performed to investigate the flow characteristics of a partial admission supersonic turbine depending on the relative positions of nozzle and cascade. The flow was visualized by a Schlieren system. The static pressures at the turbine cascade inlet, passage and outlet were measured by pressure transducers. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions of the supersonic turbine were observed by the experiments. And the flow characteristics in the supersonic turbine as the relative positions were observed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.61-68
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• 2015

The function of Feed Water Ring is to provide the flow path from Feedwater Nozzle to inside of SG(steam generator). Significant amounts of general FAC on the outside of the Feed Water Ring are not likely due to the low flow velocities in this area. However, on the interior of the Feed Water Ring, there may be areas of local higher flow velocity which could lead to higher FAC rates. These may include the inlet tee from the Feedwater Nozzle into the Feed Water Ring, the areas where the Feed Water Ring changes diameter, and especially the entrance area to the J-Nozzles. In this paper, the results of root cause analysis of through-wall hole observed at domestic WH 51F SG Feed Water Ring and its effect on the integrity and performance of SG are described. And, the maintenance strategy for WH 51F SG Feed Water Ring and the monitoring strategy for Downcomer Feed Water Ring of CE System 80 SG are presented.

• New & Renewable Energy
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• v.10 no.1
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• pp.6-19
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• 2014

Organic Rankine cycle (ORC) has been widely used to convert renewable energy such as solar energy, geothermal energy, or waste energy etc., to electric power. For a small scale output power less than 10 kW, turbo-expander is not widely used than positive displacement expander. However, the turbo-expander has merits that it can operate well at off-design points. Usually, the available thermal energy for a small scale ORC is not supplied continuously. So, the mass flowrate should be adjusted in the expander to maintain the cycle. In this study, nozzles was adopted as stator to control the mass flowrate, and radial-type turbine was used as expander. The turbine operated at partial admission. R245fa was adopted as working fluid, and supersonic nozzle was designed to get the supersonic flow at the nozzle exit. When the inlet operating condition of the working fluid was varied corresponding to the fluctuation of the available thermal energy, optimal operating condition was investigated at off-design due to the variation of mass flowrate.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.30-35
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• 2014

This study has been conducted to develop an ejector system applied in the aircraft engine-bay ventilation system. Tandem-Ejector was selected as a component of ventilation system because it could achieve high ventilation performance in spite of motive flow with small flow rate. Tandem-Ejector is composed of a primary nozzle and two mixing ducts ($1^{st}$ mixing duct and $2^{nd}$ mixing duct). In this study, 1-D Tandem-Ejector model has been built with conservation laws and isentropic relation for 1-D ejector sizing and performance prediction. Computational Fluid Dynamics(CFD) has been conducted to investigate ejector performance and flow characteristics in the ejector. Also, Tandem-Ejector performance tests have been conducted to obtain ejector pumping performance and to investigate stand-off (gap between primary nozzle and $1^{st}$ mixing duct inlet) effect on ejector pumping performance.

• The KSFM Journal of Fluid Machinery
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• v.17 no.1
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• pp.12-21
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• 2014

An organic Rankine cycle was analyzed to work at the optimal operating point when the heat source is fluctuated. R245fa was adopted as a working fluid, and an axial-type turbine as expander on the cycle was designed to convert the heat energy to the electricity since the turbo-type expander works at off-design points better than the positive displacement-type expander. A supersonic nozzle was designed to increase the spouting velocity because a higher spouting velocity can produce more output power. They were designed by the method of characteristics for the operating fluid of R245fa. Three different cases, such as various spouting velocities, various inlet total temperatures, and various nozzle numbers, were studied. From these results, an optimal operating cycle can be designed with the organic Rankine cycle when the available heat source as renewable energy is low-grade temperature and fluctuated.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.31-39
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• 2011

The flowfield in a solid rocket motor was simulated at the wall-injection test model, which has a fin-slot grain and submerged nozzle, and visualized by a smoke-wire. The high speed CCD camera captured the visualized images around the nozzle inlet through the grain center port. The vortical tube structure and circumferential flow patterns at the nozzle throat were visualized. The radial momentum transfer caused by the shear-interactions of slot-outlet flow, fin-base flow and grain port flow from upstream worked as the source of these phenomena.

• Journal of the Korean Society of Combustion
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• v.13 no.2
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• pp.1-6
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• 2008

An experimental study of the flame response in a turbulent premixed combustor has been conducted with room temperature, atmospheric pressure inlet conditions using premixed natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable speed siren. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function as a function of the modulation frequency. Of particular interest is the effect of flame structure on the flame response predictions and measurements. The results show that both the gain and the phase of flame transfer function are closely associated with the flame length and structure, which is dependent upon the upstream flow perturbation as well as equivalence ratio in the current study.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.367-370
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• 2006

This paper deals with the modeling and simulation of the internal flowfield in a valveless airbreathing pulse detonation engine (PDE) currently under experimental development at the U.S. Naval Postgraduate School. The system involves no valves in the airflow path, and the isolation between the inlet and combustor is achieved through the gasdynamics in an isolator. The analysis accommodates the full conservation equations in axisymmetric coordinates, and takes into account variable properties for ethylene/oxygen/air system. Chemical reaction schemes with a single progress variable are implemented to minimize the computational burden. Detailed flow evolution during a full cycle is explored and propulsive performance is calculated. Effect of initiator mass injection rate is examined and results indicate that the mass injection rate should be carefully selected to avoid the formation of recirculation zones in the initial cold flowfield. Flow evolution results demonstrate a successful detonation transmission from the initiator to the combustor. However, strong pressure disturbance may propagate upstream to the inlet nozzle, suggesting the current configuration could be further refined to provide more efficient isolation between the inlet and combustor.