• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.888-894
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• 2001

Advanced gas turbine engines employ turbine entry temperatures so high that cooling of the turbine blades is essential. The coolant flow introduces losses which need to be minimized, and therefore it is important that the minimum amount of coolant should be used. This work presents the result of the one-dimensional analysis and the effect of the boundary conditions on coolant flow rate in gas turbine blades.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.535-542
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• 2011

To utilizing CFX V12.0.l, internal flow characteristics of denture high-speed air turbine hand-piece unit was identified, in order to analyze the performance of the torque values were compared. In order to find out the difference of torque by mash values, under steady condition, performed grid convergence test. It compared theoretical torque with torque through flow analysis. To describe the motion of turbine blade was used to immerged solid method. Depending on the location of the turbine blade were calculated from five case. Maximum and minimum values of turbine blades was analyzed. To analyze the performance of the torque values were compared with speed of turbine blade.

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

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.4
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• pp.141-148
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• 2009

Afterfogging of the regenerative gas turbine system has an advantage over inlet fogging in that the high outlet temperature of air compressor makes the injection of more water and the recuperation of more exhaust heat possible. This study investigates the effects of turbine inlet temperature (TIT) on the performance of regenerative gas turbine system with afterfogging through a thermodynamic analysis model. For the standard ambient conditions and the water injection ratios up to 5%, the variation of system performance including the thermal efficiency is numerically analyzed with respect to the variations of TIT and pressure ratio. It is also analyzed how the maximum thermal efficiency, net specific work, and pressure ratio itself change with TIT at the peak points of thermal efficiency curve. All of these are found to increase almost linearly with the increases of both TIT and water injection ratio.

• Journal of Ocean Engineering and Technology
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• v.29 no.4
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• pp.317-321
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• 2015

Many kinds of generation systems have been developed to use ocean energy. Among these, with the use of an oscillating water column (OWC) for power generation is attracting attention. The OWC-type wave power generation system converts wave energy into electricity by operating a generator turbine with the oscillating water level in a column of water. There are two ways to convert wave power into electricity using an OWC. One uses a cross-flow turbine using the water level inside the OWC. The other method uses the flow of air in a Wells turbine, which depends on the water level. An experiment was carried out using a 2-D wave tank in order to minimize the number of empirical tests. The design factors were taken from Koo et al. (2012) and the experimental environment assumed by free surface motion. This paper deals with characteristics of two types of wave energy conversion systems combine with a breakwater. One model uses an air-driven Wells turbine and a cross-flow water turbine. The other type uses a cross-flow water turbine. Wave energy converters with OWCs have mostly been studied using air-driven Wells turbines. The efficiency of the cross-flow turbine was about 15% higher than that of the other model, and the water level of the OWC internal chamber for the cross-flow water turbine and air-driven Wells turbine was less than about 40% lower than the one using only the cross-flow water turbine.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.819-824
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• 2005

Recently, micro hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. However, suitable turbine type is not normalized yet in the range of micro hydropower and it is necessary to study for the effective turbine type. Moreover, relatively high manufacturing cost by the complex structure of the turbine is the highest barrier for developing the micro hydropower turbine. Therefore, a cross-flow turbine is proposed for micro-hydropower in this study because of its simple structure and high possibility of applying to low head. The purpose of this study is to further simplify the turbine structure and improve the performance, A guide vane is removed and the runner chamber is made compact using a new air supply method. The results show that the efficiency of the turbine is improved in a wide operating range and the size of the turbine is remarkably reduced.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.240-242
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• 2011

Wind power system is generally divided into the onshore wind turbine and the offshore wind turbine according to site locations. The offshore wind turbine is manufactured as a closed nacelle cooling system including a heat exchanger to prevent corrosion, but the onshore wind turbine is manufactured as open nacelle cooling system dependent on only the outdoor air without a heat exchanger. The indoor of a nacelle which is composed of a generator, foil power converters and a gearbox with a lot of heat is very narrow and airtight. This aim of the study is to demonstrate the temperature effect depending on positions of air-supply and exhaust ports. And this study discusses the flow field and removal efficiency of heat caused by components.

• Journal of Ocean Engineering and Technology
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• v.24 no.2
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• pp.1-9
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• 2010

Oscillating Water Column is one of the most widely used converting systems all over the world. The operating performance is influenced by the efficiencies of the two converting stages in the OWC chamber-turbine integrated system. In order to study the effects of the pressure drop induced by the air turbine, the experiments using the impulse turbine and the orifice device are carried out in the wave simulator test rig. The numerical simulation utilizing the orifice and porous media modules is calculated and validated by the corresponding experimental data. The numerical wave tank based on the two-phase VOF model embedded with the above modules is employed to investigate the wave elevation, pressure variation inside the chamber and the air flow velocity in the duct. The effects of the air turbine on the integrated system and interaction among the wave elevation, pressure and air flow velocities variations are investigated, which demonstrates that the present numerical model are more accurate to be employed.

• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.28-37
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• 2004

An experimental study is conducted to investigate flow characteristics on a small axial-type turbine which is applied as the rotating part of air tools. It operates in a partial admission due to consumption restriction of the high pressure air. In this operating condition, it is necessary to understand flow characteristics for obtaining the high specific output power. Tested turbine consists of two stages and the mean radius of flow passage is less than 10mm. A 6 bar pressure air is used to operate the turbine. The experimental results show that flow angles depend on the measuring location along the circumferential direction, but its discrepancy is alleviated along the axial direction. Absolute flow velocities show three times difference according to the measuring location at the exit of the first rotor due to the partial admission, but they show similar value at the exit of the second rotor by the velocity diffusion. From the measured flow angles and velocities, a ratio of output power obtained by the first and second rotor is estimated. It shows that the output power obtained by the second rotor is about $11\%$ to that by the first rotor at 60,000 RPM. It is effective therefore to improve the first rotor for increasing the turbine output power.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.3-12
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• 2003

This paper reviews the present state of the art on the self-rectifying air turbines, which could be used for wave energy conversion. The overall performances of the turbines under irregular wave conditions, which typically occur in the sea, have been evaluated numerically and compared from the viewpoints of the starting and running characteristics. The types of turbine included in the paper are as follows: (a) Wells turbine with guide vanes (WTGV); (b) turbine with self-pitch-controlled blades (TSCB); (c) biplane Wells turbine with guide vanes (BWGV); (d) impulse turbine with self-pitch-controlled guide vanes (ISGV) and (e) impulse turbine with fixed guide vanes (IFGV). As a result, under irregular wave conditions it is found that the running and starting characteristics of the impulse type turbines could be superior to those of the Wells turbine. Moreover, the authors have explained the mechanism of hysteretic behavior of the Wells turbine and the necessity of links for improvement of the performance of ISGV.