• 연구논문집
• /
• s.33
• /
• pp.39-51
• /
• 2003

This paper deals with the noise measurement and evaluation method of a reciprocating air-compressor and its noise reduction. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known as motor, belts, suction/discharge valves, moving piston, and flow-induced noise which are caused by edges or discontinuities along the flow path e.g. expansions, contractions, junctions and bends. As a result, it can be found that main noise sources of the air-compressor can be categorized by the suction/discharge noise, valve noise, and compressed-air tank noise. Based on the investigations, mufflers are designed to reduce both the suction/discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, engineering plastics are used as a new one for the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings in the cylinder head. As a result of the countermeasure plans, it can be achieved that the noise reduction of the air-compress is up to 10 dB.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.5
• /
• pp.730-736
• /
• 2008

The purpose of this study is to find out a flow characteristics when a crossflow-fan is installed inside the computer case and to provide information about the preliminary data of cooling efficiency of CPU and a flow inside and outside of a computer case. Under the condition of operating the fan inside the experimental duct we changed the position of a installation of the slot, and the experiment measured with PIV and the results are as follows. Under the influence of the crossflow-fan installed to the air discharging side, mean velocity between 35 to 45 on the point 80 of the Slot 0.2.3 of the case increased and it influences discharging the air inside of the computer case. On the left-upper end. which isn't directly influenced by the suction-discharging fan installed inside the PC, a flow occurs caused by vortex due to the Sirocco-Fan and Slot installed on the center of the right side. We can see that a flow distribution increases when the Sirocco-Fan operates and a whirl appears stronger between the slot and the suction fan. It is thought that this phenomenon is influenced by a flow while it is on the way of entering from the suction-fan and going out to the discharging-fan.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.461-462
• /
• 2009

• Journal of ILASS-Korea
• /
• v.3 no.2
• /
• pp.14-23
• /
• 1998

The negative pressure as much as 10's mmHg is demanded at nozzle inside, in case of atomizing the large density molten materials. by conventional air jet nozzle. In this study, suction type fluid nozzle is designed by applying the ejector principle in order to clarify the air flow of nozzle inside, mechanism of liquid suction and liquid film formation. The results of this experimental study areas follows. Suction force of liquid is magnified by using liquid nozzle, and it is able to supply the liquid stable. Negative pressure at nozzle inside is varied by throttle angle of liquid nozzle, position and outer diameter of air jet nozzle, and have a influence on liquid suction quantity and liquid film formation.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.6
• /
• pp.146-151
• /
• 2011

Wax spin coating is a part of several wafer handling processes in the silicon wafer polishing station. It is important to ensure the wax layer free of contamination to achieve the high degree of planarization on wafers after wafer polishing. Three-dimensional air flow characteristics in a wax spin coater are numerically investigated using computational fluid dynamics techniques. When the bottom of the wax spin coater is closed, there exists a significant recirculation zone over the rotating ceramic block. This recirculation zone can be the source of wax layer contamination at any rotational speed and should be avoided to maintain high wafer polishing quality. Thus, four air suction ducts are installed at the bottom of the wax spin coater in order to control the air flow pattern over the ceramic block. Present computational results show that the air suction from the bottom is quite an effective method to remove or minimize the recirculation zone over the ceramic block and the wax coating layer.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.4
• /
• pp.418-423
• /
• 2014

Small hydropower has been considered as a solution to resolve the problem of exhaustion of fossil fuel and industrial pollution. In this study, we developed and tested a Cross-Flow Turbine with two guide vanes to optimize the small hydropower for the site condition with large fluctuation of head and flow rate. Furthermore, in the condition of constant inlet head, CFD analysis was carried out to analyze the effect of air suction and valve position on the performance characteristics. The results showed that the air suction can minimize the hydraulic loss caused by the Recirculation flow in the runner passage and flow impact on main shaft so that it can increase the turbine efficiency and output power.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.9
• /
• pp.25-32
• /
• 1998

The forced cooling system is designed to shorten the overhaul time of steam turbine, which is important in view of economic concern of utility companies, Forced cooling of the hot turbine is achieved by suction of air flow into the turbine after the turbine shuts down. The heat transfer process by suction of air flow can cause thermal stress due to the thermal gradients. In this paper, the analysis of heat transfer is performed to calculate the air flow rate. Based on the prediction of cyclic fatigue damage and the experience, the cooling equipment is designed for shortening the cooling time of steam turbine.

• 한국전산유체공학회:학술대회논문집
• /
• 2002.10a
• /
• pp.114-119
• /
• 2002

A numerical model is employed for design of a spinner device to dry the 5-th generation LCD glass panel. The turbulent flow in a spinner is driven by rotation of a large disk and suction by the exhaust system connected to vacuum chamber, which is simulated by using the FLUENT package. Based on numerical simulation, the required capacity of exhaust system is assessed. The effects of the presence of cover on the flow characteristics are examined. A computational trouble shooting is attempted to resolve the problem of panel rising which occurred in real experiments.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1070_1071
• /
• 2009

Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow hydraulic turbine is proposed for small hydropower development in this study. The turbine‘s simple structure and high possibility of applying to the sites of relatively low effective head and large flow rate can be advantages for the introduction of the small hydropower development. The purpose of this study is not only to investigate the effects of air layer in the turbine chamber on the performance and internal flow of the cross-flow turbine, but also to suggest a newly developed air supply method. CFD analysis for the performance and internal flow of the turbine is conducted by an unsteady state calculation using a two-phase flow model in order to embody the air layer effect on the turbine performance effectively. The result shows that air layer effect on the performance of the turbine is considerable. The air layer located in the turbine runner passage plays the role of preventing a shock loss in the runner axis and suppressing a recirculation flow in the runner. The location of air suction hole on the chamber wall is very important factor for the performance improvement. Moreover, the ratio between air from suction pipe and water from turbine inlet is also significant factor of the turbine performance.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.3
• /
• pp.23-28
• /
• 2011

In this study, the ejector design was modeled using Fluent 6.3 of FVM(Finite Volume Method) CFD(Computational Fluid Dynamics) techniques to resolve the flow dynamics in the ejector. A vacuum system with the ejector has been widely used because of its simple construction and easy maintenance. Ejector is the main part of the desalination system, of which designs determine the efficiency of system. The effects of the ejector was investigated geometry and the operating conditions in the hydraulic characteristics. The ejector consists mainly of a nozzle, suction chamber, mixing tube (throat), diffuser and draft tube. Liquid is supplied to the ejector nozzle, the fast liquid jet produced by the nozzle entrains and the non condensable gas was sucked into the mixing tube. The multiphase CFD modeling was carried out to determine the hydrodynamic characteristics of seawater-air ejector. Condition of the simulation was varied in entrance mass flow rate (1kg/s, 1.5kg/s, 2kg/s, 2.5kg/s, 3kg/s), and position of driving nozzle was located from the central axis of the suction at -10mm, 0mm, 10mm, 20mm, 30mm.. Asaresult, suction flow velocity has the highest value in central axis of the suction.