• Journal of the Korean Institute of Gas
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• v.23 no.1
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• pp.12-18
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• 2019

Exhaust gas recirculation method is widely used among various methods for reducing nitrogen oxides in automobile engines and incinerators. In the present study, the computational fluid dynamic analysis was accomplished to derive the optimal location of air nozzle exit position by changing its position in a venturi tube for the maximum flue gas recirculation effect. In addition, the flue gas recirculation characteristics with a cone at the exit of air nozzle was elucidated with flue gas recirculation flow rate ratio and mixed gas exit temperature. When the air nozzle exit position was changed from the start position (z = 0) to the end position (z = 0.6m) of the exhaust gas recirculation exit pipe, the change of streamline and temperature distribution in the venturi tube was observed. The exhaust gas recirculation flow rate and the average temperature at the mixed gas exit position was quantitatively compared. From the present study, the optimal location of air nozzle exit position for the maximum flue gas recirculation flow rate ratio and maximum mixed gas exit temperature is z = 0.15m (1/4L). In addition, when the cone is installed at the outlet of the air nozzle, the velocity of the air nozzle outlet is increased, the flue gas recirculation flow rate was increased by about 2 times of the flow rate without cone, and the mixed gas exit temperature is increased by $116^{\circ}C$.

• Journal of Hydrogen and New Energy
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• v.25 no.5
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• pp.516-524
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• 2014

Proper discharge of nitrogen gas and water condensate is required in a conventional fuel cell system for performance, stability and durability of fuel cell stacks. Present study covers the development of integrated unit and its functioning logic for simultaneous nitrogen gas purge and water condensate drainage in a fuel cell vehicle system. Configuration of condensate drainage pipe, purge valve and level sensor is considered and optimized in physical integration. As a key factor, discharge time is considered and optimized based on the test result of constant-current operation with various operating temperature in logic development. Consequently, derived optimal values are applied and verified in actual vehicle drive mode test. Increase of system design flexibility, weight reduction and cost reduction are anticipated with this study. Additional study for physical and logical improvement is currently being implemented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.123-127
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• 2005

LRE(liquid rocket engine) performance design code with several modules for each engine component has been developed for a preliminary design purpose. Thrust chamber, non-cryogenic centrifugal pump, single stage axial impulse turbine, gas generator and exhaust pipe for extra thrust have been considered. For simplicity, pump exit pressures are fixed, which eliminates pressure balancing problem between thrust chamber and turbopump unit. In this paper, calculated performance parameters with system flow charts and the design methodologies for each component are briefly presented and the results are compared with tile real engine specification.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1928-1939
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• 1992

In this study, a computer program has been developed which predicts the variation of the volumetric efficiency with the change of design of the intake system effectively by the analysis of the flow in each part of a multi-cylinder compression ignition engine. For the calculation of the flow in the intake and exhaust systems, the method of characteristics has been used, and the double Wiebe's function has been adopted for the calculation of the heat release rate in the cylinders. The accuracy of presented method has been proved through the comparison between the simulation and experimental results over the various engine speeds and intake pipe lengths.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1260-1271
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• 2001

The simulation program which predicts the gas behavior in a spark ignition engine has been developed and verified by the comparison with the experimental results foy the MPI engine, naturally aspirated and turbochared engines with a carburettor. First paper describes the calculations of the behavior of gas in the intake and exhaust system. The generalized method of characteristics including friction, heat transfer, area change and entropy gradients was used to analyse the pipe flow The constant-Pressure model was applied for the analysis of the flow through engine valved, and the constant-pressure perfect-mixing model was applied for the flow at manifold junction. The concept of the sudden area change was used for the muffler and catalytic convertor. Fer the plenum chamber in an MPI engine, constant-pressure model and constant-volume model were both examined. Through the comparison of predicted results with experiments, the simulation program was verified by showing good prediction of the behavior of IC engine qualitatively and quantitatively under wide range of operating conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.87-100
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• 2000

HC and CO emissions during the cold start contribute the majority of the total emissions in the legislated driving cycles. Therefore, in order to minimize the cold-start emissions, the fast light-off techniques have been developed and presented in the literature. One of the most encouraging strategies for reducing start-up emissions is to place the light-off catalyst, in addition to the main under-body catalyst, near the engine exhaust manifold. This study numerically consider three-dimensional, unsteady compressible reacting flow in the light-off and under body catalyst to examine the impact of a light-off catalyst on thermal response of the under body catalyst and tail pipe emission. The effect of flow distribution on the temperature distribution and emission performance have also been examined. The present results show that flow distribution has a great influence on the temperature distribution in the monolith at the early stage of warm-up process and the ultimate conversion efficiency of light-off catalyst is severly deteriorated when the space velocity is above $100,000hr^{-1}$.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.93-99
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• 2008

To improve the performance of plasma-DeNOx catalyst, a research on active system was performed experimentally. Two hydrocarbons, propane and diesel, were used as a reductant in this study. First, using propane, basic performances of plasma-DeNOx catalyst such as the effects of plasma and C/N ratio were measured at the various engine operating conditions. NOx conversion of catalyst was improved as plasma power or C/N ratio was increased. Next, diesel was injected in the exhaust gas flow as a reductant. The first test using diesel as a reductant is spray visualization in a high temperature flow and spray images were utilized for analysis of posterior test results. To evaluate the effect of an injection direction, it was compared with 6 installation methods of diesel injector due to THC concentrations at the inlet of plasma. From the results, injector was installed toward downstream direction below the pipe. Then, basic performances of plasma-DeNOx catalyst with various injection quantities were measured. As an injection quantity was increased, $NO_2$ conversion of plasma reactor was increased but NOx conversion of catalyst was nearly zero. This was because NOx conversion of catalyst had slowed as time goes by due to black particles which had been adhered to the catalyst.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.117-122
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• 2013

This study is aimed to develop LNT(Lean NOx Trap) aftertreatment system for DME engine. Modified DME engine, which was changed from diesel to current DME engine, is used for this research and is equipped with common rail type injector and fuel supplying system. LNT system has reductant injector. DME is also used as reduction agent. For this research, reduction agent injection time width and interval were varied. And also, swirler was used to improve homogeneity of reducing agent in exhaust pipe. The reduction rate of NOx by LNT was increased by longer injection width, short interval and swirler. The maximum diminution of NOx by LNT was over 85%.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.521-527
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• 2005

The effects of an urae injection at the exhaust pipe for a 4-cylinder DI(Direct Injection) diesel engine are investigated experimentally. The urea quantity was controlled by NOx quantity and MAF(Manifold Air Flow). The urea injection must be precisely metered and then I used the urea syringe pump. I have tested 4 kinds of items that were with the EGR base engine and without the EGR engine. Then I tested each urea-SCR(Selective Catalytic Reduction) system. As the results, I can caculate the SUF(Stoichiometric Urea Flow) and visualize the NOx results by variation of engine speed and engine load. Also, I can make the NOx map. Therfore, I knew that NOx reduction effects of the urea-SCR system without the EGR engine were better than the with EGR base engine except of low load and low speed.

• Journal of ILASS-Korea
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• v.24 no.4
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• pp.178-184
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• 2019

Diesel engines have the advantages of higher thermal efficiency and lower CO2 emissions than gasoline engines, but have the disadvantages that particulate matter (PM) and nitrogen oxides (NOx) emissions are greater than those of gasoline engines. In particular, nitrogen oxides (NOx) emitted from diesel engines generates secondary ultrafine dust (PM2.5) through photochemical reactions in the atmosphere, which is fatal to humans. In order to reduce nitrogen oxides (NOx), pre-treatment systems such as EGR, post-treatment systems such as LNT and Urea SCR have been actively studied. The Urea SCR consists of an injection device injecting urea agent and a catalytic device for reducing nitrogen oxides (NOx). The nitrogen oxide (NOx) reduction performance varies greatly depending on the urea uniformity in the exhaust pipe. In this study, spray characteristics according to the spray hole structure were confirmed, and the influence of spray uniformity on spray characteristics was studied through engine evaluation.