• Journal of Power System Engineering
• /
• v.16 no.5
• /
• pp.40-46
• /
• 2012

For free surface flow problem, a high-order spectral/boundary element method is adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. Using the combination of these two methods, the free surface flow problems of a submerged moving body are solved in time domain. In the present study, lifting surface theory is added to the former work to include effects of lift force. Therefore, a new formulation for the basic mathematical theory is introduced to contain the lift body in calculation.

• Korean Journal of Agricultural Science
• /
• v.19 no.1
• /
• pp.91-96
• /
• 1992

Diesel engine being used on power tiller has over heating problem while running at the rated power range, The reason for overheating the engine is mainly owing to so small capacity of cooling system. This study was conducted to determine relatively optimum capacity of cooling system for the diesel engine. The results obtained are summarized as follows. 1. The capacity of cooling system for the diesel engine being used in the rural area was not sufficient to cool the engine at the rated power. 2. It is desirable that the cooling water flow rate was $12{\ell}/min$ if we used supplementary pump for increasing the cooling efficiency. 3. As cooling water was circuited $12{\ell}/min$, highest temperature of cooling water was $91^{\circ}C$. This value is within $88^{\circ}C{\pm}5^{\circ}C$ of SAE Standard criterion.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.14 no.1
• /
• pp.94-102
• /
• 2015

The high-pass(brand name of Electronic Toll Collection System) utilization trend on the highway continues to grow as 59.4% (by the end of 2013). In this study, we applied the carbon balance method using a fuel chassis dynamometer with the four passenger car classes in order to measure the fuel consumption of the car using the expressway tollgate. We experimented 18 driving mode at general tollgate and high-pass tollgate. As a result, in case of entry/exit toll there were 21.0~56.4ml/veh fuel consumption savings, in case of open toll fuel consumption savings was analyzed as 10.5~28.1ml/veh. In addition, the annual fuel cost savings by virtue of high-pass was 28.2~57.3 billion won at 70% utilization rate, 32.2~65.5 billion won at 80%, 36.2~73.7 billion won at 90% and 40.3~81.9 billion won at 100%.

• 대한공업교육학회지
• /
• v.33 no.2
• /
• pp.218-231
• /
• 2008

The purpose of this study was made for the pre-teacher of university to enhance understanding for the concept of engine performance and to provide information regarding engine performance in the institute of teacher educator. This study was carried out through engine performance experiment with The Cussons Engine Test Bed P8250, internal combustion engine, in order to analyze data quantitatively, and apply and verify factors of controlling engine performance. The main results of this study are as follows: First, power and brake horsepower increased linearly, and torque over the mid-speed as engine rps(revolution per second) decreased. Second, the change of torque and specific fuel consumption were able to be verified and the concept of engine performance was able to be understood. Third, the experimental values of brake horsepower and torque on engine performance showed the same tendency as theoretical values. Fourth, air/fuel ratio increased proportionally as engine speed increased.

• Korean Journal of Food Science and Technology
• /
• v.20 no.3
• /
• pp.303-309
• /
• 1988

The heat generation at the start-up period of an autogeneous single screw extruder was determined with various feed materials, die structure and operational conditions. The highest heat generation rate was observed with defatted soybean meal, while the lowest value was obtained with rice flour, and wheat and barley flour showed the intermediate rate. As the moisture content of the flour decreased and the screw speed increased, the electric power requirement and heat generation rate increased. The temperature at compression section increased with the decrease in the particle size. The same effect was also observed as breaker plate was installed. The optimum operation was established as the temperature profile was maintained in decreasing order of metering section, die and compression section.

• Journal of Biosystems Engineering
• /
• v.13 no.2
• /
• pp.18-27
• /
• 1988

The basic model of impeller was developed for the theoretical analysis of performance. The developed model was tested with two different blade radius of curvature based on the pumping efficiency under the operating conditions in Korea. And the pump performance of the impeller was also tested for the various speeds. The results obtained are summarized as follows; 1. There was no significant effect on the different blade radius of curvatures on the discharge and pump efficiency. 2. Head and power requirement was increased in proportion to the blade radius of curvature. 3. In the mathematical approach of the blade radius of curvature, the method of involute curve was more recommendable as compared with the method of circular arc curve. 4. The pump efficiency of the model impeller developed based on the theoretical analysis increased about 10% more than that of the existing impeller.

• Applied Chemistry for Engineering
• /
• v.30 no.2
• /
• pp.190-197
• /
• 2019

The adsorption of methyl green dye using an activated carbon from an aqueous solution was investigated. Adsorption experiments were carried out as a function of the adsorbent dose, initial concentration, contact time and temperature. The Langmuir isotherm model showed a good fit to the equilibrium adsorption data. Based on the estimated Langmuir separation factor, ($R_L=0.02{\sim}0.106$), this process could be employed as the effective treatment (0 < $R_L$ < 1). It was found that the adsorption was a physical process with the adsorption energy (E) value range between 316.869 and 340.049 J/mol obtained using Dubinin-Radushkevich equation. The isothermal saturation capacity obtained from brunauer emmett teller (BET) model increased with increasing the temperature. The kinetics of adsorption followed a pseudo second order model. The free energy and enthalphy values of -5.421~-7.889 and 31.915 kJ/mol, respectively indicated that the adsorption process follows spontaneous endothermic reaction. The isosteric heat of adsorption increased with the increase of equilibrium adsorption amounts, and the total interaction of the adsorbent - adsorbate increased as the surface coverage increased.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.8 no.2
• /
• pp.130-139
• /
• 2000

Serial basic tests were conducted for the determination of fundamental kinetics and for the actual application of kinetic parameter to food waste digestion with precise measurement of methane production under a thermophilic condition. The effects of food particle size, sodium ion concentration, and volatile solid (VS) loading rate on the anaerobic thermophilic food waste digestion process were investigated. Results of serial test for the determination of fundamental kinetic coefficients showed the value of k (maximum substrate utilization rate coefficient) and KS (half-saturation coefficient) as $0.24hr^{-1}$ and $700mg/{\ell}$, respectively, for non-inhibiting organic loading range. No inhibition effect was shown until $5g/{\ell}$ of sodium ion concentration was applied to a serum bottle reactor. However, the volume of methane gas was decreased gradually when the concentrations of more than $5g/{\ell}$ of sodium ion applied. All sizes of food waste particle showed the same constants (A : 0.45) but the maximum substrate utilization rate constant ($k_{HA}$) was inversely proportional to particle size. As an average particle size increased from 1.02 mm to 2.14 mm, $k_{HA}$ decreased from $0.0033hr^{-1}$ to $0.0015hr^{-1}$. The result reveals that particle size is one of the most important factors in anaerobic food waste digestion. There was no inhibition effect of sodium ion when VS loading rate was $30g/{\ell}$. And maximum injection concentration of VS loading rate was determined about $40g/{\ell}$.

• Korean Chemical Engineering Research
• /
• v.47 no.1
• /
• pp.11-16
• /
• 2009

Composite electrodes for redox supercapacitor were prepared potentiodynamically by the deposition of $RuO_2$ and the co-deposition of Ru-Co mixed oxide on the surface of single-walled carbon nanotube. Electrode of Ru-Co mixed oxide, in which Ru(13.13 wt%) and Co(2.89 wt%) were deposited on the carbon nanotube, exhibited a similar specific capacitance(${\sim}620\;F\;g^{-1}$) with $RuO_2$ electrode at a low potential scan rate($10\;mV\;s^{-1}$), but showed a superior one ($570\;F\;g^{-1}$) at a high scan rate($500\;mV\;s^{-1}$) than that of $RuO_2$($475\;F\;g^{-1}$). Such increase in the specific capacitance at high scan rate by the co-deposition of Ru and Co species was due to the structural support of Co species to provide the electronic conduction through Ru species.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.7 no.3
• /
• pp.1-11
• /
• 1987

Comprehensive laboratory experiments including digestion failures were conducted to identify differences between mesophilic and thermophilic digestion. Critical HRT was found to be near 10days for mesophilic and near 5days for thermophilic digestion. Inhibition occurred rapidly when operated below critical HRT. However, inhibition at mesophilic condition was much greater than that at thermophilic condition. Although digester performances were similar above critical HRT of mesophilic digestion, thermophilic digestion was considerably advantageous below this HRT. Thermophilic digestion produced smaller amount of sludges which had significantly higher settling velocity and lower specific resistance. Reaction rates also clearly demonstrated temperature and HRT effects on digestion. It was also found that gas production rates increased linearly with increasing reaction rates regardless of temperature and their relationships were almost identical at mesophilic and thermophilic temperature.