• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.132-136
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• 2004

Experimental study has been conducted to investigate effect of mainstream turbulence intensity on film cooling performance of staggered rows of rectangular holes in combustor. Temperature fields and adiabatic film cooling effectiveness under $10\%$ mainstream turbulence intensity are measured. The results of temperature fields show that overall values are decreased and thicker film of coolant is formed downstream of rows of holes for high mainstream turbulence intensity. The results of film cooling effectiveness show that the values around the holes are smaller than the case of the low mainstream turbulence intensity, however, the difference of film cooing performance is decreasedforthefurtherdownstream.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.1-6
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• 2003

Natural gas is one of the promising alternative fuels because of the abundant deposits and the cleanness of emission gas. CNG has a lot of merits except lower burning speed has a slow disadvantage. One way to overcome the disadvantage is to raise a turbulence intensity. We give various intake for changing turbulence intensity in the cylinder by three kinds of swirl control valve with a way to raise a turbulence intensity. In the present study, a $1.8\ell$ conventional gasoline engine is modified to use a CNG as a fuel instead of gasoline. We try to virify combustion and emission characteristics in each engine parameters. Parameters of experimentation are equivalence ratio, spark timing and intake flow change. The results of this study are as swirl flows. In the case of adding swirl flow, burning speed and torque are increased. But NOx and THC concentration are increased a little respectively.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.2
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• pp.33-38
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• 2006

Heat transfer coefficients and static pressure distributions on a gas turbine vane endwall were experimentally investigated in a 5 bladed linear cascade. The Reynolds number based on an axial chord length and the cascade exit velocity was 500,000. Both heat transfer and pressure measurements on the vane endwall were made at the two different turbulence intensity levels of 6.8% and 10.8%. Detailed heat transfer coefficient distributions on the vane endwall region were measured using a hue detection based transient liquid crystals technique. Results show various regions of high and low heat transfer coefficients on the vane endwall surface due to several types of secondary flows and vortices. Heat transfer coefficient and endwall static pressure distributions showed similar trends for both turbulence intensity, however, the averaged heat transfer coefficients for higher turbulence intensity case was higher than the lower turbulence intensity case by 15%.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.279-289
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• 2017

In this study, a series of conjugate heat transfer (CHT) analyses are conducted for a stage of a fully cooled high-pressure turbine (HPT) at elevated levels of free stream turbulence (Tu = 5% and 25.7%). The goal of the analyses is to investigate the influence of high turbulence intensity on the fluid-thermal characteristics of a nozzle guide vane (NGV). The turbine inlet temperature is defined by considering a typical radial temperature distribution factor (RTDF). The Unsteady Reynolds Average Navier-Stokes (URANS) CHT simulations are carried out using CFX 15.0, a commercial CFD package. The presented CFD modeling approach for high turbulence intensity is verified with the experimental data from two types of NASA C3X NGVs with films. The computation grid is generated for both the fluid and solid domains. The fluid domain grid is created using a tetrahedral grid system with prism layers because of its complex geometry, and the solid domain grid is composed of only tetrahedral elements. The analytical results are compared to understand the effect of turbulence on flow characteristics and metal temperature distributions. The results obtained in this study provide useful insights on the effects of high free stream turbulence and unsteadiness. The results also lead to the proposal of meaningful turbine design guidelines.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.813-820
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• 2003

The purpose of this research is to develop the model of turbulence modulation due to the presence of particles in various types of particle-laden flows Available experimental data are surveyed and the dependence of turbulence modulation of carrier-phase on particle size, concentration and. particle Reynolds number are examined. This study takes into account the effect of wake produced by particle, the drag between phases and the velocity gradient in the wake to estimate the production of turbulence. The model of turbulence modulation using the mixing length theory under the assumption of equilibrium flow is proposed. Numerical results show that the model is successful in predicting the characteristics of the particle-laden in various flow conditions both qualitatively and quantitatively.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.181-186
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• 2003

An experimental study has been conducted to measure the temperature fields for two and three staggered rows of the rectangular shaped-holes with high turbulence intensity. 10 % turbulence intensity is obtained by installation of two kinds of grids which have different shapes. One grid which is installed at 30d upstream from center of 1st row of holes is composed of vertical cylinders of which diameter is 10 mm and center to center distance is 18 mm. The other installed 15d apart to upstream from center of 1st row of holes which has square pattern is constructed of 3 rum square bars and bar spacing is 25 mm. Temperature fields are measured by using a thermocouple rake which is attached on three-axis traversing system. The results show that the overall values are decreased and the thicker film of coolant is fanned downstream of rows of holes for high mainstream turbulence intensity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.244-254
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• 1996

Flow velocity was measured by, use of hot wire anemometer. Turbulence intensity was in proportion to mean flow velocity regardless of swirl velocity. And integral length scale has proportional relation with swirl velocity regardless of measurement position. Turbulent burning speed during flame propagation which was determined by flame photograph and gas pressure of combustion chamber was increased with the lapse of time from spark and was decreased a little at later combustion period. Because of combustion promotion effect, turbulent burning speed was increased according to increase of turbulence intensity. Burning speed ratio i.e. ratio of turbulent burning speed ($S_BT$) to laminar burning speed ($S_BL$) was found out by use of turbulence intensity u' and integral length scale $l_x$ , $\delta_L$ is width of preheat zone in laminar flame.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.435-446
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• 2014

Tidal turbulence was examined using three-dimensional tidal velocity data observed at a trench offshore of Tongyoung, Korea. The kinetic energy and intensity, including the variation period of the flow velocity and direction, were used to investigate the relationships between tidal turbulence and fishing gear dynamics, including the effects of swimming fish during fishing operations. As the resultant velocity increased from 0.2 to 0.9 m/s, the kinetic energy also significantly increased, while the turbulence intensity decreased from 50 to 10%. Tidal flow in strong flow fields displayed shorter periods of between 4 and 10 s, as determined by fast Fourier transform, the global wavelet method, and peak event analysis, and the periods were compared with the period of response to swimming fish and to oscillation of fishing gear. As mean velocity increased, velocity amplitude also increased from 0.1 to 0.6 m/s, and its directional amplitude changed markedly from 20 and $90^{\circ}$. Our study suggests that tidal turbulence can influence fish behavior or fishing gear geometry during fishing operations, although our analysis considered only a limited area. In future work, observations should be carried out over a more extensive depth and area.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.23-30
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• 1998

The stabilization characteristics of diffusion flame formed in the wake of a cylindrical flame holder were investigated. Distribution of turbulence intensity, concentration distribution of combustion gas, and ion currents were measured. The turbulence intensity in the wake of cylindrical- game holder is increased with increase of diameter or blockage ratio of grid. If the auxiliary fuel is injected into recirculation zone, the concentration of $C_3H_8$ is high, but the concentration of $CO_2$ is low at the boundary of recirculation zone. The region with highest average value of ion currents in the middle of flame is moved to the upstream side by the turbulent components of main stream. The flame mass with partially active reaction is moved fast for uniform flow and turbulence generator G3, but the flame mass with relatively slow reaction is moved slowly for turbulence generator G1.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.814-822
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• 2012

To improve the flow and mixing characteristics of marine SCR system, two different mixer including up-down and swirl type mixer were considered. The purpose of this study is to analyse turbulence intensity and uniformity index in detail and to improve the performance of SCR with respect to the mixer structure. The results showed that, the concentration uniformity index is improved by about 5% with the utilization of both mixers in the front of catalyst part. Although the RMS value and relative turbulence intensity increased after the up-down type mixer, it could observed that the value of two parameters decreased with the flow proceeding forward to the downstream. For the case of swirl type mixer, the decrease of RMS value and relative turbulence intensity were relatively smaller than that of up-down type mixer, and uniform distribution of relative turbulence intensity was observed. As a results, it could be concluded that the mixing effects and the distance of the two kinds of mixer were different.