• Journal of Biosystems Engineering
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• v.22 no.2
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• pp.189-198
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• 1997

In order to find out the potential of LP gas as a substitute fuel for small fm engine, experiments were carried out with a four-stroke spark-ignition engine which was modified from a kerosene engine mounted on the power tiller. Performance characteristics of kerosene and LP gas engine such as torque, volumetric efficiency fuel consumption rate, brake thermal efficiency, exhaust temperature, and carbon monoxide and hydrocarbon emissions were measured and analyzed under various levels of engine speed and compression ratio. The results were summarized as follows. 1. It showed that forque of LPG engine was 41% lower than that of kerosene engine with the same compression ratio, but LPG engine with compression ratio of 8.5 it was showed similar torque level to kerosene engine with compression ratio of 4.5. 2. Fuel consumption of LPG engine was reduced by about 5.1% and thermal efficiency was improved by about 2% compared with kerosene engine with the same compression ratio. With the incrasing of compression ratio in LPG engine fuel consumption rate decreased and thermal efficiency increased. 3. Exhaust temperature of LPG engine was about 15% lower than that of kerosene engine. Concenrations of emissions from LPG engine was affected insignificantly by compression ratios, and carbon monoxide emissions from the LPG engine was not affected by engine speed so much. The carbon monoxide and hydrocarbon emissions from LPG engine were about 94% and 66% lower than those of kerosene engine, respectively.

• Journal of Biosystems Engineering
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• v.31 no.2 s.115
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• pp.108-114
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• 2006

This study was conducted to design and fabricate a controller for variable-rate application of granular fertilizer based on physical and chemical information, to analyze the performance of the controller and characteristics of a discharger. The result of the study are summarized as follows: 1. The charge ratios of discharger by accumulation heights of fertilizer in hopper were examined, and the variations in charge ratio were $72.58{\sim}93.33%$ and $63.14{\sim}94.42%$ for the fertilizers Super 21 and Sinsedae, respectively. The charge ratio also decreased as the rotational speed of discharger increased. 2. The coefficient of variation of discharge amount by rotational speed and discharge time of discharger were in the range of $2.94{\sim}11.23%$ and $2.82{\sim}10.80%$ for the fertilizer of Super 21 and Sinsedae. Except the rotational speed of 12 rpm, the coefficient of variation for discharge amount were relatively small with 4% more or less 3. In order to evaluate the rotational speed of discharger, the control signal in the range of $0{\sim}5V$ was subdivided into the 50 steps by 0.1V. The regression equation for the rotational speed of discharger was Y=55.984X-79.174(X: input voltage, V, Y: discharger speed, RPM) and the $R^2$ was 0.99. 4. In order to evaluate the performance of the controller for variable-rate application of granular fertilizer, settling time to unit step input was examined. The settling time varied from 0.8sec to 1.4 sec.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.308-311
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• 2004

Nowadays, plastic industry has needed to produce parts that require high precision and quality. To make a high precision and quality part, before injection molding, plastic material is investigated about their properties such as shrinkage, warpage, etc. In this study, experiments were conducted with PA6(polyamid) to figure out shrinkage behavior according to three type aspect ratio of samples. The injection speed that affects on shear rate, molecular orientation within plastic part was determined as main variable of experiment. As a result of experimental study, part shrinkage had a tendency to be decreased by increasing injection speed and aspect ratio of samples.

• Laser Solutions
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• v.13 no.3
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• pp.7-12
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• 2010

In this study, laser welding of aluminum AA5182 with AA5356 filler wire was carried out and the formability of the weld joint was evaluated through Erichsen test according to laser power, welding speed and wire feed rate. Fracture was occurred in both directions, perpendicular and parallel to the weld line at 0.75 of Erichsen ratio. Second order Regression model to estimate Erichsen ratio with experimental variables was proposed and the performance of model was evaluated with F-test and average error rate.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.103-108
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• 2003

The control of flame shapes in a laminar pre-mixed flame has been experimentally investigated for propane/air pre-mixed laminar flames. Flames of different size and shapes are observed with heated wires or by controlling the equivalence ratio and flow rate of a mixture. The characteristics of the partitioning of a flame or the merge of flames are analyzed and explained by considering the balance between laminar flame speed and upstream mixture velocity. A combustor might be sized down while maintaining its heat production rate the same by partitioning a flame established in it. When the equivalence ratio of mixture is decreased, individual flames are merged together and the upstream mixture velocity can be practically decreased on a nozzle having opening ratio less than unity. As a result, the flame shape is to he adjusted until the newly established balanced condition is satisfied, and then. the stable combustion can be achieved again.

• Journal of Welding and Joining
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• v.33 no.5
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• pp.47-52
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• 2015

In this study, it was tried to analyze the effects of welding parameters on the weld penetration and aspect ratio when a STS316L pipe was welded in a horizontal position by GTAW. Experiments were systematically designed using a L18 orthogonal array, and the effects of welding parameters were statistically analyzed by ANOVA(Analysis of Variance). The shielding gas type has the largest effect on both the penetration and aspect ratio. The welding current type and shielding gas flow rate have a little effect on the penetration, whereas the electrode tip angle has a little effect on the aspect ratio. When welded at a selected welding condition, which is composed of He shielding gas, pulse current of 300/45 A, electrode tip angle of 90o, and shielding gas flow rate of 30 l/min, the estimated interval at least 95 % confidence was $1.99{\pm}0.18mm$ for the penetration and $0.31{\pm}0.04$ for the aspect ratio. From the confirmation experiments, the average penetration and aspect ratio were well agreed with the estimation as 1.96 mm and 0.30, respectively. Additionally, the effects of the welding speed and welding current on the penetration and aspect ratio were experimented and analyzed by linear regression. The penetration was linearly increased with the decrease of the welding speed and with the increase of the welding current, but the aspect ratio showed a tendency to a little decrease with the increase of both the welding speed and current.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1998.06b
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• pp.206-216
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• 1998

The structural characteristics of small scale rice polisher was analyzed to improve its performance. Spraying characteristic of nozzles used for rice polishing was also analyzed by a machine vision system. The internal pressure of the polishing chamber was measured according to outlet resistance, water spraying , and roller shaft speed. In addition , the performance of the rice polisher was evaluated to improve it in the basis of internal pressure in polishing chamber, whiteness , and broken rice ratio of clean rice according to the operating conditions. Actual nozzle discharge rate and drop size were 125cc/min and 86.97㎛, respectively. In the case of water spraying on rices, the internal pressure showed 4.9-9.8N/㎠ increase, broken rice ration decreased , and there was no difference in whiteness . The internal pressure increased up to two time with the increase of the outlet resistance. Also, the pressure at the upper part of screen was one and half times as high as the pressure at the lower part. In the case of water spraying rate of 150 cc/min, the roller shaft speed of 850 rpm resulted in no difference in whiteness and decrease of 0.3%in broken rice ratio, comparing to the roller shaft speed of 950 rpm.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.237-243
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• 2002

A centrifugal compressor of 50HP for reverse brayton cryocooler using neon as a coolent has been developed. It has relatively low total-to-total pressure ratio but mass flow rate is very small and the voting gas, neon, has greater specific heat ratio than air. It was essential to have very high rotational speed of 100,000 RPM. The efficiency of compressor has great effects on overall system and the COP of cryocooler. To meet the design requirement of the compressor efficiency and to minimized the required rotational speed, highly efficiency impeller having low specific speed was designed. To maintain the overall system efficient high, gas bearing of bump type and high speed permanent magnet synchronus motor was developed and adopted. In this paper, design and performance prediction results of the compressor impeller is presented.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.181-183
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• 2012

Syngas laminar flame speed measurements were carried out at atmospheric pressure and ambient temperature using the Bunsen flame configuration with nozzle burner as a fundamental study on flame stability of syngas. Representative syngas mixture compositions ($H_2:CO$) such as 25:75%, 50:50% and 70:25% and equivalence ratios from 0.5 to 1.4 were investigated. The measured laminar flame speeds were in good agreement with the previous numerical data as well as experimental data available in the literatures over a wide range of equivalence ratio tested. It was reconfirmed that the laminar flame speed gradually increased with the increase in $H_2$ content in a fuel mixture. In particular, the significant increasing rate of flame speed was observed with the increase in equivalence ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.86-96
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• 1997

In this paper, engine-CVT consolidated control algorithm was developed. Engine -CVT control strategy suggested uses throttle control based on power difference and CVT ratio control based in CVT ratio map. Simulation results showed that the larger the rate of CVT ratio, the better the engine performance in the optimal operation line. Also, it was found that the engine performance where the magnitude of the acceleration changes abruptly depends on the magnitude of the rate of CVT ratio. Comparing the results of CVT control only without engine control, the engine-CVT control algorithm suggested in this work showed better performance demonstrating that the consolidated control algorithm should be required for the engine optimal operation.