• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.521-529
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• 2017

Three-dimensional flow characteristics within a high-acceleration first-stage turbine vane passage has been investigated in a newly-built vane cascade for propulsion. The result shows that there is a strong favorable pressure gradient on the vane pressure surface. On its suction surface, however, there exists not only a much stronger favorable pressure gradient than that on the pressure surface upstream of the mid-chord but also a subsequent adverse pressure gradient downstream of it. By employing two different oil-film methods with upstream coating and full-coverage coating, a four-vortex model horseshoe vortex system can be identified ahead of each leading edge in the cascade, and the separation line of inlet boundary layer flow as well as the separation line of re-attached flow is provided as well. In addition, basic flow data such as secondary flow, aerodynamic loss, and flow turning angle downstream of the cascade are obtained.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.155-165
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• 1998

The resistance coefficient and heat transfer performance are studied for the turbulent water flow in a smooth coiled tube having variable curvature ratios and a corrugated-coiled tube having a ratio of coil to tube diameter of 22. Experiments are carried out for the fully developed turbulent flow of water in tube coils on the uniform wall temperature condition. This work is limited to tube coils of R/a between 22 and 60 and Reynolds numbers from 13000 to 53000. The tube having a ratio of coil to tube diameter of 27 among the 3 smooth tube coils shows the best heat transfer performance. A corrugated-coiled tube(R/a=60) shows more excellent performance than a smooth coiled tub (R/a=60) at a similar curvature ratio. The friction factor f is sensitive to changes in the velocity profile caused by a temperature gradient. Allowance was made for the pressure loss in the short inlet and outlet lengths and due to the presence of the thermocouple inlet and outlet as a result of separate experimental on a straight tube. It is to be expected that the allowance at the exit will be somewhat too low because of secondary flow effects carried over from the coil.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.47-52
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• 1998

To eliminate foreign substance like metal rust and sand in natural gas pipeline, 250um strainer filter is used present in Korea Gas Corporation. But particles smaller than 250um passing the filter have bad effects to the valves and the measuring equipments. In order to eliminate small paticle in the pipeline, it is necessary to cut down the pore size of filter When we cut down the pore size of filter, the pressure difference between the front of filter and that of the rear part is increasing and disturb normal condition of gas supply. So it is very important to control the condition between the pore size of filter and the pressure difference. In this study, using head loss coefficient K, the estimation method of efficiency of gas filter according to the pore size and the pressure difference is presented.

• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1144-1153
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• 2002

A hybrid performance prediction method is proposed in the present study. A channel diffuser is divided into four subregions: vaneless space, semi-vaneless space, channel, and channel exit region. One-dimensional compressible core flow and boundary layer calculation of each region with an incidence loss model and empirical correlation of residuary pressure recovery coefficient of a channel predict the performance of diffusers. Three channel diffusers are designed and tested for validating the developed prediction method. The pressure distributions from an impeller exit to the channel diffuser exit are measured and discussed for various operating conditions from choke to nearly surge conditions. The strong non-uniform pressure distribution which is caused by impeller-diffuser interaction is obtained over the vaneless and semi-vaneless spaces. The predicted performance shows good agreement with the measured performance of diffusers at a design condition as well as at off-design conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1062-1070
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• 2016

The heat transfer and flow characteristics of gas turbine blade tip were investigated in this paper by using the conjugate heat transfer analysis. The rotor inlet boundary condition profile which was taken from the first stage nozzle outlet was used to analyse. The profile contained the velocity and temperature information. This study presents the influence of tip clearance about aerodynamic loss, heat transfer coefficient and film cooling effectiveness with the squealer tip designed blade model which tip clearance variation range from 1% to 2.5% of span. Results showed that the aerodynamic loss and the heat transfer coefficient were increased when the tip clearance was increased. Especially when the tip clearance was 2% of the span, the average heat transfer coefficient on the tip region was increased obviously. The film cooling effectiveness of tip region was increasing with decreasing of the tip clearance. There was high film cooling effectiveness at cavity and near tip hole region.

• Journal of computational fluids engineering
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• v.19 no.1
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• pp.21-26
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• 2014

Butterfly valve is a valve that controls fluid flow depending on the size of the opening angle. In general, the size of the opening angle of the valve increases, the fluid flow has also increased sharply. However, sometimes, in a specific piping system, a particular operating condition is needed that the fluctuation of the fluid flow should not have large amount although the size of opening angle of the valve become larger. In butterfly value, the shape of a typical thin plate, it is impossible to control a minute fluid, but in thick plate type, it is possible. In this study, we got the fluid flow control characteristics and pressure drop through both a numerical method and an experimental method about thick plate type. The numerical result and experimental result of flow coefficient show a similar pattern. In addition, we could find that minute fluid flow control was possible in the area of small size of the opening angle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.301-307
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• 2012

The characteristics of pressure loss in an asymmetric bifurcating tube were investigated numerically for steady inspiratory conditions. The loss coefficient K calculated for various asymmetry and flow-distribution ratios found in human lung airways showed a power-law dependence on the Reynolds number (Re) and length-to-diameter ratio (L/d), with different exponents for Re $\geq$ 100 and Re < 100. The fundamental characteristics of the asymmetric bifurcation are similar to the case of symmetric bifurcation. In addition, the effect of skewed inlet velocity profiles on the pressure loss was weak, and decreased with an increasing number of bifurcations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2171-2180
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• 1991

An analysis model for off-design performance of radial inflow turbines with or without variable area guide vane is developed, where two important factors in loss models, total pressure ratio between variable area guide vane exit and scroll casing inlet and rotor loss coefficient are determined without experimental data. The analysis results show that the predicted trends with or without variable area guide vane are consistent with the experimental observations. The comparison of present method with the well-known NASA off-design performance analysis program shows that the mass flow rate and static efficiency by present analysis are in good agreement with those by the NASA program. Therefore, this method can be used to predict off-design performance of radial inflow turbines with validity of the loss models used by present analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.312-322
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• 2001

This paper investigates the combined effects of parameters such as die surface finish, die directionality of stoning contact pressure and draw speed on the resulting coefficient of friction. Also, this study show the correlation between the NN(Neural Network) and DOE(Design of Experiments) to reduce the number of experiments without the loss of the effects of parameter upon coefficient of friction. The experiments were run in random order with at least three replicates. It was found that the directional stoning orthogonal to the pulling direction is lower friction than directional stoning parallel to the pulling directi on using FCD55 die and SPCEN.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.89-95
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• 2017

The improvement of a flow coefficient for the recirculation chill-down flow in a main oxidizer shut-off valve has been presented. The flow coefficient, which is mainly affected by the recirculation outlet port size and the configuration inside the valve, has been predicted with measured flow coefficient values. The comparison of experimentally measured flow coefficient with the predicted value shows the effect of valve inside configuration on the flow coefficient. Consequently, the flow coefficient is twice the previous value and about 75% of the pressure loss assigned to the main oxidizer shut-off valve can be used for additional pressure losses for other components in the recirculation chill-down system of a launch vehicle.