• The KSFM Journal of Fluid Machinery
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• v.18 no.4
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• pp.30-35
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• 2015

This study analyzed the variations in the performance and operation of a 200 kW class micro gas turbine according to performance degradation of compressor and turbine. An in-house code, developed by the present authors and presented in the first part of these series of papers, were used for the analysis. The degradation of compressor and turbine were simulated by modifications in the their performance maps: mass flow rate, pressure ratio and efficiency were decreased from the reference values. Firstly, the variations in the operating conditions (air flow rate, pressure ratio) were predicted for the full load condition. Then, the same analysis were performed for a wide partial load operating range. The change in engine's performance (power output and efficiency) due to the component degradation was predicted. In addition, the change in the compressor surge margin, which is an important indicator for safe engine operation, was evaluated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.437-443
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• 2014

Electric motors and drives consume the largest amount of electricity more than 40% of global electricity consumption. In addition, motors, drives and its components are included in the global high-trade products and the main driving source for industrial equipment and house appliances. Thus, International standards and regulations for their safety and efficiency are internationally being discussed and created for the protection of its citizens and energy saving. So, understanding the international standards and the regulation of each country is essential to enhance overseas market and to develop product. In this paper, on the basis of this background, status and trends of international standards and regulations are introduced for safety and efficiency of motors and the drives. Safety and efficiency of the IEC (International Electrotechical Commission) standards are introduced in the emphasis. Also, regulations are studied about the differences and trends in each county.

• International Journal of Fluid Machinery and Systems
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• v.8 no.2
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• pp.94-101
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• 2015

To investigate the influence of blade profiles on cavitation behavior in impeller of centrifugal pump, a centrifugal pump with five different blade profiles impellers are studied numerically. The impellers with five different blade profiles (single arc, double arcs, triple arcs, logarithmic spiral and linear-variable angle spiral) were designed by the in-house hydraulic design code using geometric parameters of IS 150-125-125 centrifugal pump. The experiments of the centrifugal pump have been conducted to verify numerical simulation model. The numerical results show that the blade profile lines has a weak effect on cavitation inception near blade inlet edge position, however it has the key effect on the development of sheet cavitation in impeller, and also influences the distribution of sheet cavitation in impeller channels. A slight changing of blade setting angle will induce significant difference of cavitation in impeller. The sharp changing of impeller blade setting angle causes obvious cavitation region separation near the impeller inlet close to blade suction surface and much more flow loss. The centrifugal pump with blade profile of setting angle gently changing (logarithmic spiral) has the super cavitation performance, which means smaller critical cavitation number and lower vapor cavity volume fraction at the same conditions.

• International Journal of Fluid Machinery and Systems
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• v.8 no.2
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• pp.73-84
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• 2015

Aerating hydroturbines have recently been proposed as an effective way to mitigate the problem of low dissolved oxygen in the discharge of hydroelectric power plants. The design of such a hydroturbine requires a precise understanding of the dependence of the generated bubble size distribution upon the operating conditions (viz. liquid velocity, air ventilation rate, hydrofoil configuration, etc.) and the consequent rise in dissolved oxygen in the downstream water. The purpose of the current research is to investigate the effect of location of air injection on the resulting bubble size distribution, thus leading to a quantitative analysis of aeration statistics and capabilities for two turbine blade hydrofoil designs. The two blade designs differed in their location of air injection. Extensive sets of experiments were conducted by varying the liquid velocity, aeration rate and the hydrofoil angle of attack, to characterize the resulting bubble size distribution. Using a shadow imaging technique to capture the bubble images in the wake and an in-house developed image analysis algorithm, it was found that the hydrofoil with leading edge ventilation produced smaller size bubbles as compared to the hydrofoil being ventilated at the trailing edge.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.475-481
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• 2001

Foil bearings have been successfully used for small high speed rotors, such as ACM(Air Cycle Machine), turbo charger, turbo compressor, high speed motor, etc. Recently advanced researches are concentrated on the high load capacity and the extreme temperature foil bearings to extend the application boundary. Some bearings are already adopted into cryogenic machines and micro gas turbines. In this paper, a foil journal bearing designed for high load capacity, which is under development, is introduced. The bearing is for the turbo refrigerator which has a rotor of 18${\~}$25 kgf rotating at 23,000${\~}$38,000 rpm. This application is well beyond conventional spectrum of foil bearings because the rotor is relatively heavy and the rotational speed is low. Therefore, the development is challenging. The foil bearing is a bump type, the size is 60mm in diameter and 50mm in length, the operating fluid is air and rotational speed is 26,000 rpm. In-house software was developed and used for bearing design. Tested maximum load capacity is 80kgf, 0.62 in terms of load capacity coefficient, and testing is being continued.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.544-547
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• 2002

According to the rising of national economic level. domestic consumption of vegetables having high additive values is increased continuously due to increased consumption of meat in last decade. These vegetables are produced almost in this country and are limited to import from neighbor countries in due of high transportation expenses for storing in refrigerated container. It is very important to mechanize the harvest work, forming more than 30% for their production cost, in order to cultivate variable vegetables at the same time according to their harvesting seasons. In this state its former harvest methods, with using of human power or semi-automatic harvest, caused to increase their production cost due to high labor cost and low working efficiency. The former onion harvest being operated almost by semi-automatic plant distributer mechanism have many limit and troublesome for cultivation spaces, vinyle mulched ridge, gravel mixture in soil. Therefore, it is necessary to develope a fully automatic and self-running situation and overcome above handicaps, even in the farm covered with vinyle house or mulch sheets. This newly developed onion harvest can be applied to plant various young trees and will be able to export together with onion haying their competition in the worldwide market in which the culinary vegetable method or farm conditions is similar to our country.

• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.294-303
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• 2015

The present study is conducted to identify a better design and optimal number of Francis runner blades for sediment laden high head micro hydropower site, Tara Khola in the Baglung district of Nepal. The runner is designed with in-house code and Computational Fluid Dynamics (CFD) analysis is performed to evaluate the performance with three configurations; 11, 13 and 17 numbers of runner blades. The three sets of runners were also investigated for the sediment erosion tendency. The runner with 13 blades shows better performance at design as well as in variable discharge conditions. 96.2% efficiency is obtained from the runner with 13 blades at the design point, and the runners with 17 and 11 blades have 88.25% and 76.63% efficiencies respectively. Further, the runner with 13 blades has better manufacturability than the runner with 17 blades as it has long and highly curved blade with small gaps between the blades, but it comes with 65% more erosion tendency than in the runner with 17 blades.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.48-53
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• 2012

This paper presents a systematic procedure for three-dimensional noise analysis of an axial-flow fan by using computational aero-acoustics based on Ffowcs Williams-Hawkings equation. Flow-fields of a basic fan model are simulated by solving three-dimensional, unsteady, Reynolds-averaged Navier-Stokes equations using the commercial code ANSYS CFX 11.0. Starting with steady flow results, unsteady flow analysis is performed to extract the fluctuating pressures in the time domain at specified local points on the blade surface of the axial flow fan. The perturbed density wave by rotating blades reaches at the observer position, which is simulated by an in-house noise prediction software based on Ffowcs Williams-Hawkings equation. The detailed far-field noise signatures from the axial-flow fan are analyzed in terms of source types, field characteristics, and interpolation schemes.

• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.346-354
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• 1990

In order to provide basic references for the design of heating on simple silkworm rearing house, the actual change of heating load coefficient by progress of adult silkworm rearing day from the reared in silkworm rearing house, the heating load coefficient by types of silkworm rearing houses and the heating requirement and the maximum heating load by types of silkworm rearing houses were determined. The results obtained from the study were as follows : 1. The average heating load coefficients of NS, OS and CC type simple silkworm rearing houses were $24.1KJ/m^2-hr-^{\circ}C$, $19.8KJ/m^2-hr-^{\circ}C$, and $10.8KJ/m^2-hr-^{\circ}C$, respectively. 2. The change of heating load coefficient by progress of silkworm rearing day after reared into simple silkworm rearing house could be expressed as Fig. 4. 3. Heating degree-hour for adult silkworm rearing in Suweon district was calculated as $951.6^{\circ}C-hr$ for spring season and $610.5^{\circ}C-hr$ for autumn season. 4. Yearly heating requirement of the NS type was estimated twice more than that of the CC type. Thus, some kinds of reinforced thermal adiabatic facilities is desirable for NS type. 5. The time for maximum heating load was turned out at the 4th instar during the spring season and after the mounting during the autumn season. 6. This study was performed in Suweon district. However, the estimated and analyzed data could be adapted to the major silkworm rearing district if their meteorology data were adjusted.

• Journal of Animal Environmental Science
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• v.20 no.3
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• pp.91-96
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• 2014

The temperature of a pig is the most key point in determining, it's health status. We wanted to monitor the body temperature of pig to find out if any changes would occur, we used 3 minipigs (about 20 kg) who were feed using a feeding system while being confined in a pig house. The infrared testings were taken from a height of 30 cm above the pigs backs over a period of 28 days. We were able to conclude that the results between the back and indoor temperature were y = 0.5487x + 18.459. These values were compared with the values found after infrared sensor results were taken. We found an error range of $0.004{\sim}1.82^{\circ}C$ and an average of $0.58^{\circ}C$. In conclusion, using an infrared thermometer made monitoring of pigs back possible. This system seems to be feasible and effective in monitoring pig temperature.