• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.726-739
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• 2003

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.324-327
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• 2008

We simulated the performance improvement of a wind turbine installed on the pitched roof-building(apartment in urban area, 50m height). A nozzle shape wind guide is added on the roof of a model apartment. The nozzle-diifuser structure effects for the free stream wind (average 4m/s, 50m height in Incheon) is studied by a basic CFD analysis. This paper examines the effects of roof structure on the wind velocity and the wind distortion effects by a front building. The possible wind power generation capacity on building roof in urban is calculated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.36-43
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• 2014

Recently, research has been conducted to develop the ORC (organic Rankine cycle), to recover waste heat from facilities such as industrial plants ultimately to create mechanical or electrical energy. The ORC system consists of a heat exchange, a condenser, a pump and a boiler. In this paper, 84 flow analyses were conducted with 21 cases and three variables, i.e., a number of large wings, a number of small wings, and RPMs. R245fa was used as a refrigerant. The flow cavitation phenomenon was investigated through a flow analysis, and a flow stream analysis was conducted.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.55-62
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• 2003

This paper describes the effect of the incidence angle on the turbulence structure in the wake of a turbine rotor blade at the low inlet free-stream turbulence level. For three incidence angles of -5, 0 and 5 degrees, mid-span energy spectrum as well as mid-span profiles of mean velocity magnitude and turbulence intensity are reported at three downstream locations in the wake. Vortex shedding frequencies are obtained from the energy spectrum. The result shows that as the incidence angle changes from-5 to 5 degrees, the boundary layer on the suction surface tends to be thickened, which results in widening of the wake. Strouhal numbers based on the shedding frequencies have a nearly constant value of 0.3, independent of tested incidence angles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1195-1207
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• 1998

Periodic pulsations in the static pressure near turbine surfaces as blade rows move relative to each other is one of the important sources of turbine unsteadiness. The present experiment aims to investigate the effect of the static pressure pulsations on the interaction of film coolant flows from two rows of staggered holes with mainstream and its effect on film cooling heat transfer. Potential flow pulsations are generated by the rotating shutter mechanism installed downstream of the test section, The free-stream Strouhal number based on the boundary layer thickness is in the range of 0.033 - 0.33, and the amplitude of about 10-20%. Measured are time-averaged and phase-averaged velocity variations, pressure variations and temperature distributions of the flow field. Experimental conditions are identified by boundary layer measurements. Injectant behavior is characterized by the measurements of unsteady pressure in the plenum chamber and free-stream static pressure. The film cooling effectiveness is evaluated from the insulated wall temperature measurement. It has been found that bulk flow pulsation provides very large diffusion of the injectants and the effectiveness is significantly reduced by the flow pulsations.

• Ocean and Polar Research
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• v.42 no.4
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• pp.293-301
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• 2020

Blades of tidal stream turbines have to sustain many different loads during operation in the underwater environment, so securing their structural safety is a key issue. In this study, we focused on periodic loads due to wave orbital motion and propose a load reduction method with a blade design. The flap of an airplane wing is a well-known structure designed to increase lift, and it can also change the load distribution on the wing through deflection. For this reason, we adopted a passive flap structure for the load reduction and investigated its effectiveness by an analytical method based on the blade element moment theory. Flap torsional stiffness required for the design of the passive flap can be obtained by calculating the flap moment based on the analytic method. Comparison between a flapped and a fixed blade showed the effect of the flap on load reduction in a high amplitude wave condition.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.1
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• pp.95-104
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• 2022

Micro hydropower is a readily available renewable energy source that can be harvested utilizing hydrokinetic turbines from shallow water canals, irrigation and industrial channel flows, and run-off river stream flows. These sources generally have low head (<1 m) and low velocity which makes it difficult to harvest energy using conventional turbines. A horizontal-axis screw turbine was designed and numerically tested to extract power from such low-head water sources. The 3-bladed screw-type turbine is placed horizontally perpendicular to the incoming flow, partially submerged in a narrow water channel at no-head condition. The turbine hydraulic performances were studied using Computational Fluid Dynamics models. Turbine design parameters such as the shroud diameter, the hub-to-shroud ratios, and the submerged depths were obtained through a steady-state parametric study. The resulting turbine configuration was then tested by solving the unsteady multiphase free-surface equations mimicking an actual open channel flow scenario. The turbine performance in the shallow channel were studied for various Tip Speed Ratios (TSR). The highest power coefficient was obtained at a TSR of 0.3. The turbine was then scaled-up to test its performance on a real site condition at a head of 0.3 m. The highest power coefficient obtained was 0.18. Several losses were observed in the 3-bladed turbine design and to minimize losses, the number of blades were increased to five. The power coefficient improved by 236% for a 5-bladed screw turbine. The fluid losses were minimized by increasing the blade surface area submerged in water. The turbine performance was increased by 74.4% after dipping the turbine to a bottom wall clearance of 30 cm from 60 cm. The final output of the novel horizontal-axis screw turbine showed a 2.83 kW power output at a power coefficient of 0.63. The turbine is expected to produce 18,744 kWh/year of electricity. The design feasibility test of the turbine showed promising results to harvest energy from small hydropower sources.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.929-936
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• 2015

Nacelle anemometers are mounted on wind-turbine nacelles behind blade roots to measure the free-stream wind speed projected onto the wind turbine for control purposes. However, nacelle anemometers measure the transformed wind speed that is due to the wake effect caused by the blades' rotation and the nacelle geometry, etc. In this paper, we derive the Nacelle Transfer Function (NTF) to calibrate the nacelle wind speed to the free-stream wind speed, as required to carry out the performance test of wind turbines according to the IEC 61400-12-2 Wind-Turbine Standard. For the reference free-stream wind data, we use the Light Detection And Ranging (LiDAR) measurement at the Shinan wind power plant located on the Bigeumdo Island shoreline. To improve the simple linear regression NTF, we derive the multiple nonlinear regression NTF. The standard error of the wind speed was found to have decreased by a factor of 9.4, whereas the mean of the power-output residual distribution decreased by 6.5 when the 2-parameter NTF was used instead of the 1-parameter NTF.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1249-1259
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• 2002

The present study investigates the convective heat/mass transfer inside a cooling passage of rotating gas-turbine blades. The rotating duct has various configurations made of ribs with 70。 attack angle, which are attached on leading and trailing surfaces. A naphthalene sublimation technique is employed to determine detailed local heat transfer coefficients using the heat and mass transfer analogy. The present experiments employ two-surface heating conditions in the rotating duct because the surfaces, exposed to hot gas stream, are pressure and suction side surfaces in the middle passages of an actual gas-turbine blade. In the stationary conditions, the parallel rib arrangement presents higher heat/mass transfer characteristics in the first pass, however, these characteristics disappear in the second pass due to the turning effects. In the rotating conditions, the cross rib present less heat/mass transfer discrepancy between the leading and the trailing surfaces in the first pass. In the second pass, the heat/mass transfer characteristics are much more complex due to the combined effects of the angled ribs, the sharp fuming and the rotation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.1
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• pp.21-29
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• 2016

The wake effects behind wind turbines were investigated by using data from a Met Mast tower and the SCADA (Supervisory Control and Data Acquisition) system for a wind turbine. The results of the wake investigations and predicted values for the velocity deficit based on the eddy viscosity model were compared with the turbulence intensity from the Lange model. As a result, the velocity deficit and turbulence intensity of the wake increased as the free stream wind speed decreased. In addition, the magnitude of the velocity deficit for the center of the wake using the eddy viscosity model was overestimated while the turbulence intensity from the Lange model showed similarities with measured values.