• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1588-1598
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• 2001

The effects of recirculated exhaust gas on the characteristics of NOx and soot emissions under a wide range of engine loads were experimentally investigated by using a four-cycle, four-cylinder, sw irl chamber type, water-cooled diesel engine operating at three engine speeds. The purpose of this study was to develop the EGR-control system for reducing NOx and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions, and a novel diesel soot removal device with a cylinder-type scrubber for the experiment system was specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. The experiments were performed at the fixed fuel injection timing of 4$^{\circ}$ ATDC regardless of experimental conditions. It was found that soot emissions in exhaust gases were reduced by 20 to 70% when the scrubber was applied in the range of the experimental conditions, and that NOx emissions decreased markedly, especially at higher loads, while soot emissions increased owing to the decrease in intake and exhaust oxygen concentrations, and the increase in equivalence ratio as the EGR rate is elevated.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.418-423
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• 2014

Small hydropower has been considered as a solution to resolve the problem of exhaustion of fossil fuel and industrial pollution. In this study, we developed and tested a Cross-Flow Turbine with two guide vanes to optimize the small hydropower for the site condition with large fluctuation of head and flow rate. Furthermore, in the condition of constant inlet head, CFD analysis was carried out to analyze the effect of air suction and valve position on the performance characteristics. The results showed that the air suction can minimize the hydraulic loss caused by the Recirculation flow in the runner passage and flow impact on main shaft so that it can increase the turbine efficiency and output power.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.6
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• pp.407-412
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• 2008

Heat transfer from three-dimensional heat-generating modules was investigated. Simulated electronic module in an array configured with dummy module elements were used to measure the average heat transfer coefficients. Various module arrangements were tested using module spacings of 0.85 and 1.15 cm for six Reynolds numbers ranging from 500 to 975. The results show that a module placed in-line with and upstream of a heated module results in the heat transfer enhancement due to high turbulence intensity prompted by upstream modules. The highest enhancement occurs when the separation distance between modules is close to the module length in the flow direction. The laminar flow was observed on the front of the first module, slow recirculation regions on the sides parallel to the airstream, and turbulent flow on the back side. It appears that the first module serves to trip the air stream and produce a high level of turbulence, which enhances the heat transfer rate downstream.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.95-98
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• 2010

A multi-injector rocket engine using high concentrated hydrogen peroxide and kerosene as the oxidizer and fuel was designed and fabricated. Six coaxial swirl injectors were mounted on the mixing head and flow analysis in the manifold was performed to minimize stagnation and recirculation zones. Finally, uniformity of mass flow rate and spray pattern was evaluated by cold flow tests and the mixing head design process was successfully verified the results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.1
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• pp.58-62
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• 2002

The efforts of EGR on performance and emissions were investigated in this study. The engine used for the tests was a six-cylinder, 11 liter, and turbo-charged, heavy-duty diesel engine with a low pressure route ECR system. The volume of recirculated gas was controlled by a manually operated valve which was installed between the turbine outlet and compressor inlet. The experiments were performed at various engine speeds and loads while the ECR rates were set at 4% and 8%. Exhaust emissions with EGR system were compared with the baseline emissions.

• Journal of Pharmaceutical Investigation
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• v.27 no.3
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• pp.189-198
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• 1997

The purpose of the present study was to investigate the effect of medium chain fatty acid salts, reported as enhancers in insulin nasal absorption, on the rectal absorption of insulin in rats. The serum glucose and remained insulin level in perfusate were measured after rectal recirculation of insulin with or without sod. laurate, sod. caprate and sod. caprylate in situ. The addition of sod. laurate or sod. caprate reduced serum glucose concentration considerably. Sod. caprate (1.0%) showed the greatest promoting effect on the decrement of serum glucose. Eudispert hv hydrogels containing insulin with medium chain fatty acid salts were, thereby, prepared and evaluated. The release rate of insulin from Eudispert hv hydrogels was reduced with an increase in the content of Eudispert hv, and was raised with increasing NaOH concentration. Ten percent Eudispert hv hydrogels were offered for the rectal administration of insulin. The addition of 1.0% sod. caprate reduced serum glucose concentration remarkably after rectal administration of 10% Eudispert hv hydrogels containing insulin. The level of glucose decrement was greater by 30% compared to subcutaneous administration of insulin solution. From the above findings, Eudispert hv hydrogels would be used as useful rectal delivery systems of insulin.

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.24-30
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• 2013

Flame stabilization characteristics of premixed flames in an annular coaxial 5-tubes burner (AC5TB) were investigated experimentally. The AC5TB was made of five quartz tubes, and the flame stabilization conditions in that burner were investigated with the variation of equivalence ratio and the flow velocities. Flame behaviors inside of narrow annular tubes could be observed directly. Overall flame stabilization conditions were similar to that of the previous study, while the flame behaviors and structures were different mainly due to the controlled uniform distribution of the velocities in channels. Flame flashback conditions were thought to be governed by the competition between heat release rate, heat loss and heat recirculation in each channel. Stationary flames at a fixed location were compared in its velocity distribution and burned gas temperature across the channel. This AC5TB can be a basic configuration for the development of flame stabilization model of porous media combustors, and it will help understand about the real behavior of flames in meso-scale combustion spaces.

• Environmental Engineering Research
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• v.17 no.4
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• pp.191-196
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• 2012

Analysis of hydrological safety as well as the determination of many substance concentrations are necessary when bioreactor systems are introduced to landfill operations. Therefore, hydrological and substance balance model was developed since it can be applied to various bioreactor landfill operation systems. For the final evaluation of the model's effectiveness, four different methods of injections (leachate alone, leachate and organic waste water, leachate and reverse osmosis concentrate, and all the above three combination) was applied to 1st landfill site of Sudokwon landfill. As a result, the water content of the hypothetical cases for four different systematic bioreactors is projected to be increased up to 35.5% in next 10 years, and this indicated that there will be no problems in meeting the hydrological safety. Also, the final $Cl^-$ concentration after 10-yr time period was projected to be between from minimum 126 to maximum 3,238 mg/L, which could be still a decrease from the original value of 3,278 mg/L. According to the proposed model, whether the substance concentration becomes increased or decreased largely depends on the ratio of initial quantity of inner landfill leachate and the rate of injection.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.56-64
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• 2015

This study presents a model-based gain scheduling strategy for PI-based EGR controllers. The air-to-fuel ratio is used as an indirect measurement of the EGR rate. In order to cope with the nonlinearity and parameter varying characteristics of the EGR system, we proposed a static gain model of the EGR system using a new scheduling parameter. With the 810 steady-state measurements, the static gain model achieved 0.94 of R-squared value. Based on the static gain of the EGR system, the PI gains were robustly designed using quantitative feedback theory. Consequently, the gains of the PI controller are scheduled according to the static gain parameter of the EGR path in runtime. The proposed model-based gain scheduling strategy was validated through various operating conditions of engine experiments such as setpoint step responses and disturbance rejections.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.179-184
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• 2007

In this study, the potential use of oxygenated fuels such as ethylene glycol mono-normal butyl ether (EGBE) was investigated in an attempt to reduce the emission of exhaust smoke from diesel engines. Effects of the combustion method on exhaust emission of DI and IDI diesel engines were also examined. Since EGBE is composed of approximately 27.1% oxygen, this is one of several potential oxygenated fuels that could reduce the smoke content of exhaust gas. EGBE blended fuels have been proven to reduce smoke emission remarkably compared to the conventional commercial fuels. The test was conducted with single and four cylinder, four stroke, DI and IDI diesel engines. The study showed that a simultaneous reduction of smoke and NOx emission could be achieved by the combination of oxygenated blend fuels and the cooled EGR method in both DI and IDI diesel engines. It was also found that a reduction rate of exhaust emission in a DI engine was larger than an IDI diesel engine.