• Proceedings of the KSME Conference
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• 2001.06d
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• pp.858-863
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• 2001

In this paper, the test and result of flow and combustion for 21AFR lean fuel models are described. The necessity to develop the low emission combustor has been issued from the concern on the increase of green house and the destruction of ozone layer. To evaluate the flow and combustion performance of new designed 21AFR lean modules, the hydraulic tests in stereo lithographic airflows models, the low pressure combustion tests in three injectors model for weak extinction and ignition and the high pressure combustion tests in single sector for NOx, SAE and efficiency are performed. The low pressure tests reveal that the governing parameters in weak extinction and ignition at atmospheric condition are prefilmer length, swirl flow rotation direction, secondary swirl angle and flow split. As a results of combustion test at high pressure, the efficiency and smoke level are satisfied with performance targets, but EINOx of 17.8 is higher than target value of 13.1. The high pressure tests show that the main parameters influenced on NOx are primary swirl angle, swirl flow rotation direction, heatshield exit angle and liner mixing hole location.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.1
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• pp.8-14
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• 2000

The present day, interest in low flow statistics has been increased, primarily because of the increase in water demands and the contamination of water quality and the limitation of water resource development and the annual water supply stability. The model for estimating low flow statistics is points of this study chosen catchments in the Youngsan basin. For the purpose of this study. the low-flow discharge at 23 points, where absent gauging station is unmeasured and the data is used for the model. Finally, the regional formula to estimate the low flow statistics at the unmeasured point is proposed.

• Spatial Information Research
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• v.17 no.2
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• pp.223-239
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• 2009

The low fow analysis for small-mid sized river basins is very difficult because of insufficient flow data or ungauged basins. The objective of this study is to suggest effective method of low flow using area function method for calculating Total Maximum Daily Loads (TMDL) by considering environmental carrying capacity. Two watersheds which are Juchon watershed having $606km^2$ areas and ungauged watershed having $4,551km^2$ areas were selected for this study. As a result of application, the low flow in the downstream of Juchon River and the Han River after confluence of Okdong River were $1.9m^3/s$ and $20.7m^3/s$, respectively. Then we consider the target BOD of 1.0-1.2mg/l in Youngwol prefecture, the TDML was estimated 164-197kg/day and 1,788-2,146kg/day, respectively. This approach will useful for estimating TDML to insufficient watershed of flow data and ungauged watershed of flow data.

• Journal of the Korea Convergence Society
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• v.9 no.2
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• pp.171-176
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• 2018

The purpose of this study is to establish smart signage in a certain space and to analyze not only media ingestion and advertising inducement as well as any information (high vs. low vs. low) and flow level And the memory effect related to whether or not to remember. The results of this study show that the higher the interaction level and the higher the engagement level, the higher the advertising engagement is. In addition, media involvement was high when interaction level was low and flow level was high. Finally, if the level of interactivity is low and the level of flow is high, then non - valued attribution information is more likely to be recalled than the comprehensive evaluation information. If the interaction of smart signage is high and the flow of users is low, Recalled more recall information. In the future, detailed strategies for enhancing user flow will be needed rather than a strategy for unconditional enhancement of interaction in smart signage strategy.

• Water for future
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• v.14 no.1
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• pp.31-37
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• 1981

It was possible to synthesize the low flow frequency curves for ungauged stations of Geum river system through a correlation analysis using the morphological parameters such as basin area, bnsin relief, total stream length of first-order stream and the 7-day, 10-year low flow.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.356-361
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• 1997

To investigate parametric effect on CHF and to get CHF data, experimental study has been performed with vertical round tubes under the condition of low pressure and low flow (LPLF). Test sections are made of Inconel-625 tube and have the geometry of 8 and 10 mm in diameter, and 0.5 and 1.0 m in heated length. All experiments have been conducted at the pressure of under 9 bar, the mass flux of under 250 kg/$m^2$ and the inlet subcooling of 350 and 450 kJ/kg, for stable upward flow with water as a coolant. Flow regime analysis has been performed for obtained CHF data with Mishima's flow regime map, which reveals that most of the CHF occur in the annular-mist flow regime. General parametric trends of the collected CHF data are consistent with those of previous studies. However, for the pressure effect on CHF, two different are observed; For relatively high mass flux, CHF increases with pressure and far lower mass flux, CHF decrease with pressure. Using modern data regression tool, ACE algorithm, two new CHF correlations for LPLF condition are developed based on local condition and inlet condition, respectively. The developed CHF correlations show better prediction accuracy compared with existing CHF prediction methods.

• The KSFM Journal of Fluid Machinery
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• v.16 no.2
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• pp.48-53
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• 2013

This paper presents a numerical investigation of the influence of the blade back sweep angle on the performance and flow characteristics in a centrifugal compressor with a vaneless diffuser. Five impellers with different back sweep angles were tested in the flow simulations. It was found that a low back sweep angle could improve the total-to-total pressure ratio and the work coefficient over whole operating ranges. However, the flow field in an impeller with a low back sweep angle produced a more non-uniform velocity distribution at the impeller exit because the wake region was significantly increased. As a consequence, the impeller with a low back sweep angle caused a low diffuser performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1840-1850
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• 1994

Enhancement of numerical algorithms for low speed compressible flow will be considered. Contemporary time-marching algorithm has been widely accepted and applied as the method of choice for transonic, supersonic and hypersonic flows. In the low Mach number regime, time-marching algorithms do not fare as well. When the velocity is small, eigenvalues of the system of compressible equations differ widely so that the system becomes very stiff and the convergence becomes very slow. This characteristic can lead to difficulties in computations of many practical engineering problems. In the present approach, the time-derivative preconditioning method will be used to control the eigenvalue stiffness and to extend computational capabilities over a wide range of flow conditions (from very low Mach number to supersonic flow). Computational capabilities of the above algorithm will be demonstrated through computation of a variety of practical engineering problems.

• Journal of Mechanical Science and Technology
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• v.19 no.7
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• pp.1449-1459
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• 2005

This paper shows the results of local flow speed measurement using tunable AC thermal anemometry, which is suitable for the accurate measurement of wide range flow speed. The measurement accuracy is verified through the comparison between the measurement data and the analytic solution of the sensor temperature oscillation in stationary fluid. The relation between the phase lag and the flow speed is experimentally investigated at various conditions. The measurement sensitivity for low flow speed improves in a low frequency region and that for high flow speed improves in a high frequency region. Also, the sensitivity increases with decreasing thermal conductivity of the surrounding fluid. The local flow speed could be measured as low as 1.5 mm/s and the highest measurement resolution was 0.05 mm/s in the range of 4.5 $\~$5.0 mm/s at 1 Hz in this experiment.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2771-2788
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• 2020

Experiments are conducted to study bubble flow behavior during the instability of subcooled boiling under uniform and non-uniform transverse heating. The non-uniform heat distribution introduces nonuniform bubble generation and condensation rates on the heated surface, which is different from the uniform heating. These bubble generation and condensation characteristics introduce a non-uniform local pressure distribution in the transverse direction, which creates an extra non-uniform pressure on the flowing bubbles. Therefore, different bubble flow behavior can be observed between uniform and non-uniform heating conditions. In the uniform heating, bubble velocity fluctuations are low, and the bubbles travel straight along the axial direction. In the non-uniform heating, more fluctuation in the bubble velocity occurs at low mass flow rate and high subcooled inlet temperatures, and reverse flow is observed. Additionally, the bubbles show a zigzag trajectory when they pass through the channel, which indicates the existence of cross flow in the transverse direction.