• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.17-26
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• 2004

In this paper, power transmission systems converts the shaft power of a Turbo-shaft Engine with Free Power Turbine into the generator power and be composed of a method being supplied in the thrust motor driving a propellers. Being used this, Gas turbine engine works to flat rating about 110 kw (147 shp) that the thrust motor be extremely supplied from the engine of 317shp. In this test equipment, the engine is installed with the flywheel being able to the damping function when happen to the varying load between gas turbine engine output-shaft and generator. Then if the flywheel of inertial moment be not considered, the generator and motor not get the required power from the engine for raising the load. Also it is certified that the engine works the abnormal operation. Hence the flywheel of inertial moment is determined the required range to do the performance analysis with the dynamic transient from the given and tested engine data. This system is able to get the required power after a mounting test with the redesigned flywheel.

• Journal of Animal Science and Technology
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• v.52 no.1
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• pp.57-64
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• 2010

This study was conducted to compare the aspects of behavior between miniature pigs and conventional sows during gestation and lactation periods. Miniature pigs and conventional sows at 3 parity were used in this experiment with 4 pigs per treatment. The behavioral patterns and stereotyped behaviors were observed on day 60 and 90 of gestation, at farrowing, and on day 10 of lactation before and after the feeding. On 60 and 90 days of pregnancy, both treatments showed the tendency of frequent lateral lying rather than other postures. On ventral lying, eating and drinking, miniature pigs spent more time than conventional pigs at day 90 of gestation (P<0.01, P=0.0539, P<0.05, respectively). The occurrence of stereotyped behaviors included bar biting and bar mouth chewing. At 90 day of pregnancy was observed, conventional pigs was higher than miniature pigs (P<0.05). At farrowing, miniature pigs spent more time on ventral lying, standing and walking than conventional sows (P<0.05), however, there were more frequency of drinking and eating. And on day 10 of lactation, there was no significant difference in stereotyped behaviors between miniature pigs and conventional sows. In conclusion, miniature pigs were generally more sensitive than conventional sows although sows were reared in stall during gestation and lactation period and the behavioral pattern during lactating period showed the similarity between miniature pigs and conventional sows for protection of nursing pigs. In consideration of the general reproductive performance of conventional sows, the high sensitivity and stress of miniature pigs did not affect the reproductive performance of miniature pigs.

• Korean Journal of Animal Reproduction
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• v.21 no.4
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• pp.411-421
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• 1997

A survey was carried out to investigate the symptoms and occurance of reproductive disorder in Hanwoo(Korean native cattle). Data of the reproductive disorder of 561 heads from 28 farm households have been collected from Dec. '95 to Nov. '96 and analyzed calving no, nutritional body condition and housing forms. The results obtained are summarized as follows: 1. The incidence of reproductive disorder was 20.1% and the major common symptoms were repeat breeding(39.8%), anestrous(31.0%), nymphomania(10.6%) and subestrous(8.9%). 2. The incidence of reproductive disorder according to the calving no., that of heifer, calved one to two calving no. and over three calving no. were 20.6%, 13.9% and 34.5%, respectively. 3. Reproductive disorder incidence according to the nutritional body condition was 18.3%, 14.6% and 48.7% at body condition score(BCS) less than 2.0, 2.5 to 3.0 and over than 3.5, respectively. At BCS over 3.0, the symptoms of common reproductive disorder were repeat breeding(17.6%), anestrous(12.2%), nymphomania(10.8%) and subestrous(2.7%). 4. The incidence of reproductive disorder according to the housing form 15.8% and 34.6% for group feeding in open house and individual stanchion feeding in stall, respectively. In group feeding, reproductive disorder incidence of cows raised in space of more than 9.9$m^2$ per head was 14.1%, while that of cows raised less than 9.9$m^2$ per head was 18.2%. And incidence of repeat breeding, aneestrous and subestrous was more frequent in individual stanchion feeding than group feeding.

• The KSFM Journal of Fluid Machinery
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• v.4 no.1 s.10
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• pp.7-13
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• 2001

In developing a multistage compressor, the stage matching is one of the critical design issues. The mismatching can be often observed even if each stage has been proven good and then used as part of a compression system. A good matching among the stages can be achieved by changing various design parameters (i.e., passage cross sectional areas, blades angles, stagger angles, curvature, solidity, etc.). Therefore, designers need to find out what parameters must be changed and how much. In this study, a method to search the design parameters for optimum stage matching has been used based on an 1-D mathematical model of a compressor, which uses the data obtained from the preliminary test to identify the design parameters. This methodology is applied with a two-stage axial compressor, which was originally designed for a helicopter gas turbine engine. After identifying design parameters using preliminary test data, an optimization process has been employed to achieve the best matching between the stages (i.e., maximum efficiency of the compressor at its operation modes within a given range of the rotor speed under given restrictions for required stall margins and mass flow). 3-D flow calculations have been performed to confirm the usefulness of the corrections based on the 1-D mathematical model. Calculational results agree well with the experimental data in view of the performance characteristics. Some promising results were produced through the methodology proposed in this paper in conjunction with flow calculations.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.70-80
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• 2016

The comparison of two commercial codes(FLUENT and STAR-CCM+) and an open-source code(OpenFOAM) are carried out for the aerodynamic analysis of flight vehicles at low speeds. Tailless blended-wing-body UCAV, main wing and propeller of HALE UAV(EAV-3) are chosen as geometries for the investigation. Using the same mesh, incompressible flow simulations are carried out and the results from three different codes are compared. In the linear region, the maximum difference of lift and drag coefficients of UCAV are found to be less than 2% and 5 counts, respectively and shows good agreement with wind tunnel test data. In a stall region, however, the reliability of RANS simulation is found to become poor and the uncertainty according to code also increases. The effect of turbulence models and meshes generated from different tools are also examined. The transition model yields better results in terms of drag which are much closer to the test data. The pitching moment is confirmed to be sensitive to the existence and the location of transition. For the case of EAV-3 wing, the difference of results with ${\kappa}-{\omega}$ SST model is increased when Reynolds number becomes low. The results for the propeller show good agreement within 1% difference of thrust. The reliability and uncertainty of three codes is found to be reasonable for the purpose of engineering use. However, the physical validity and reliability of results seem to be carefully examined when ${\kappa}-{\omega}$ SST model is used for aerodynamic simulation at low speeds or low Reynolds number conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.47-53
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• 2004

An Experimental investigation into the effects of the blowing jet type and jet orientation on the aerodynamic characteristics over an elliptic type airfoil is explored. This study is aimed at expanding the data base of blowing jet application in separation control of elliptic airfoil. Present data includes: surface pressure, blowing jet exit velocity measurements and integrated aerodynamic loads. The experiments were performed for an elliptic airfoil at Reynolds number $8.22{\times}10^5$. The improvement of effects of pulsed jet on the increase of aerodynamic characteristics was significant for the post-stall angle. For reduced mass flow rates, pulsed jet allowed considerably higher lift to be generated. The jet orientation also showed dominant parameter on the separation control Positive jet angle delay or avoid separation, whereas negative jet angle promotes it.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.2
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• pp.134-143
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• 2014

A significant degradation in the aerodynamic performance of wind turbine system can occur by ice accretion on the surface of blades operated in cold climate. The ice accretion can result in performance loss, overloading due to delayed stall, excessive vibration associated with mass imbalance, ice shedding, instrumental measurement errors, and, in worst case, wind turbine system shutdown. In this study, the effects of ice accretions on the aerodynamic characteristics of wind turbine blade sections are investigated on the basis of modern CFD method. In addition, the computational results are used to predict the performance of three-dimensional wind turbine blade system through the blade element momentum method. It is shown that the thickness of ice accretion increases from the root to the tip and the effects of icing conditions such as relative wind velocity play significant role in the shape of ice accretion.

• Journal of Animal Environmental Science
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• v.14 no.2
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• pp.91-96
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• 2008

The odours from spreading the slurry, manure storage tanks, and the stall are a source of annoyance for the neighbors and sometimes even become a case for civil appeal. Reducing the odourant and ammonia emission is an urgent need to be addressed. It is known that brown coal and oak charcoal have an ability to absorb odour. We designed an experiment set in lab scale and used the brown coal and oak charcoal as additives in the test to reduce odour. The test are divided into two categories; namely aeration and no-aeration. The additives were added to the each sample at a concentration of 5% and 10% of total base solids, besides the control samples. We carried out the Phenate Method for ammonia analyzing. In the non-aerated case, the results showed a reducing efficiency of 23.7% and 26.4% with an addition rate of 5% and 10% of additives, respectively. In the aerated test, the reducing efficiency of ammonia was 17.8% and 21.0% with an addition rate of 5% and 10% of additives, respectively. In case of oak charcoal, non-aeration showed removal efficiencies of ammonia at 15.9% and 16.1% with addition rates of 5% and 10%, respectively, With aeration, they were 11.4% and 26.4% with addition rates of 5% and 10% oak charcoal, respectively. The tests show that brown coal and oak charcoal have a reducing effect on ammonia emissions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.7
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• pp.549-557
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• 2008

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(${\kappa}-\;{\varepsilon}$) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model.

• 대한공업교육학회지
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• v.32 no.1
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• pp.117-133
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• 2007

The purpose of this study was to develop the force measuring device of learning wind tunnel, teaching-learning materials in order to enhance understanding of flight principle and give interest about aviation technology in secondary school. The content of this study was consisted of the development and experiment of force measuring device for learning wind tunnel. The main results of this study were as follows: This device developed here is simple structure applying lever principle instead of the comparatively expensive load cell used in engineering college or a aviation research institute and so on. Measurement of lift and drag as well as the comparison experiment of a fluid resistance is possible with only one device developed here. The lift coefficient with angle of attack has shown the same tendency in both of theoretical and experimental values. And the stall phenomenon was found under the larger angle of attack of experimental rather than expected theoretical values. The drag coefficient with angle of attack has shown the same tendency in both of theoretical and experimental values. And drag coefficient the rate of increasement of the experimental values increased more gently than its theoretical values.