• Journal of the Korean Society of Combustion
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• v.14 no.1
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• pp.31-38
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• 2009

The effects of acoustic excitation of coaxial air on mixing enhancement and reduction of nitrogen oxides (NOx) emission were investigated. A compression driver was attached to the coaxial air supply tube to impose excitation. Measurements of NOx emission with frequency sweeping were performed to observe the trend of NOx emission according to the fuel and air flow conditions and to inquire about the effective excitation frequency for reducing NOx. Then, Schlieren photographs were taken to visualize the flow field and to study the effect of excitation. In addition, phase-locked particle image velocimetry (PIV) was performed to acquire velocity field for each case and to investigate the effect of vortices more clearly. Direct photographs and OH chemiluminescence photographs were taken to study the variation of flame length and reaction zone. It was found that acoustic forcing frequencies close to the resonance frequencies of coaxial air supply tube could reduce NOx emission. This NOx reduction was influenced by mixing enhancement due to large-scale vortices formed by fluctuation of coaxial air jet velocity.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.76-83
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• 2010

Recently, as the current and future emission regulations go stringent, the research of NOx reduction has become a subject of increasing interest and attention in diesel engine. Selective Catalytic Reduction (SCR) is one of the effective technology to reduce NOx emission from diesel engine. Especially, Urea-SCR that uses urea as a reductant is becoming increasingly popular as a cost effective way of reducing NOx emissions from heavy duty vehicles. In this research, we designed urea injector and DCU (Dosing Control Unit) specially developed for controlling the Urea-SCR process onboard vehicles. As passenger and commercial diesel engine experiment, we grasped characteristics of NOx emission and SCR catalyst temperature level in advance. As a result, highest NOx emission level was shown in condition of low engine speed and high load. On the other hand, SCR catalyst temperature was highest at high engine speed and load. On the basis of these result, we conducted the NOx reduction test at steady engine operating conditions using the urea injector and DCU. It was shown that 74% NOx conversion efficiency on the average and 97% NOx conversion efficiency was obtained at high SCR catalyst temperature.

• Journal of ILASS-Korea
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• v.22 no.3
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• pp.122-128
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• 2017

Currently, the proportion of diesel vehicles in all automobile has grown significantly over the past few years. Air pollutant also grew up and became a social problem. In particular, the issue of NOx emissions caused by NOx high emission in real driving has become a global issue. Despite the fact that the regulatory and reduction project of the new vehicle is actively carried out, there are no existence regulations of In-use diesel vehicle's NOx emission. Therefore, the emission characteristics of the in-use diesel vehicles were investigated to seek ways to reduce NOx emissions in this study. The test targets were used in 237 close inspection of exhaust gases and model year varied from 1996 to 2011. However, the classification of emissions by emission standards differed considerably from NOx emissions. This means that the selection method for early retirement targets should be converted from model year to amount of emissions. If the current early retirement program was applied to the existing system, pre-Euro 3 was 22.530 g/km and Euro 4 was 21.810 g/km to NOx reduction. However, when the vehicle was changed to high emission target vehicle, NOx reduction increase maximum 84.705 kg/yr. According to the study results, an effective reduction in NOx emissions can be achieved if an earlier target in expanded to Euro 4 vehicles.

• Journal of the Korean Society of Combustion
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• v.10 no.1
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• pp.13-19
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• 2005

Measurements of flame length and NOx emissions have been conducted to investigate the effects of acoustic excitation on flame structure in turbulent hydrogen diffusion flames with coaxial air. When the acoustic excitation of a specific frequency is applied to coaxial air stream, flame length is dramatically reduced, resulting in reduction of flame residence time. Consequently, EINOx could decrease up to 35 % and this shows that acoustic excitation is effective in reducing NOx emissions. Mie scattering technique has been used to visualize the vortex structure induced by acoustic excitation and vortex formation, development and destruction were observed quantitatively. As a result, vortex entrains coflow air into fuel stream and mixing rate between fuel and air is significantly enhanced, which may contribute to reduction of NOx emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.71-76
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• 2003

A numerical simulation of selective catalytic reduction (SCR) for NO with $NH_3$ is conducted over the $V_2O_5/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The governing $NH_3$ and NO transport equations are considered by using the time-dependent FCT (Flux-Corrected Transport) algorithm. After a validating simulation for $NH_3$ step feed and shut-off experiments is analyzed, transient behavior of $NH_3$ and NO concentration in a SCR catalyst is investigated by changing such parameters as inflow $NH_3$ concentration, temperature of the catalyst, and $NH_3$/NOx ratios.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.79-84
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• 2011

Air pollutants from a small marine diesel engine are increasing and the IMO(International Marine Organization) regulation asked for its reduction. In this study, NOx reduction technologies such as improvement of various cooling systems are applied to the small marine diesel engine. The various cooling systems are a intercooler, a heat exchanger for engine coolant, and an exhaust manifold by water cooling. These systems are tested on an engine dynamometer and a exhaust gas analyzer by a marine diesel engine test regulation. Test results are shows that the small marine engine are satisfied the IMO NOx regulations; Tire II.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2762-2770
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• 2000

The refuse incineration plant has an important role in saving the combustion energy for local heating system. But harmful combustion gas(NOx etc.) leads to some serious environmental problem. To reduce the gas, a SCR(Selective Catalytic Reduction)system is installed and it is controlled by adjusting the flow of ammonia gas(NH3) . In this paper, we apply a repetitive control method to reduce NOx by adjusting the flow of ammonia gas for SCR system in a refuse incineration plant which is located in Haeundae, Pusan, Firstly, we analyze the inlet NOx period by FFt method, and verify its periodic variations. Secondly, we design a repetitive control system by using state space model method. Lastly, the effectiveness of repetitive control system is shown by comparing to a conventional PID control in simulation and experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.2
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• pp.248-255
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• 2002

Miller cycle was studied and analyzed by engine performance simulation to achieve very low fuel consumption and to meet the IMO NOx regulation on a medium speed diesel engine. Based on the performance simulation results the intake valve closing time for HYUNDAI HiMSEN 6H21/32 engine was set at 0deg.ABDC(After Bottom Dead Center). Also, the simulation results indicated that significant NOx reduction could be achieved with low reduction of fuel consumption. The performance simulation investigated the effect of compression ratio and turbocharger on fuel consumption and NOx concentration in combination with Miller cycle. The results indicated a significant reduction of fuel consumption with keeping NOx concentration. The results of performance simulation were compared with measured data to verify simulation results. The comparison showed the maximum error was 2.34% in exhaust temperature. Also, the experimental result showed that improvement in BSFC(Brake Specific Fuel Consumption) was 5.8g/kwh with keeping NOx level similar to simulation result.

• 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 Korean Society for Atmospheric Environment
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• v.4 no.2
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• pp.38-46
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• 1988

NOx is an important air pollution material which is generated when fossil fuels are burning, NOx removal in flue gas by selective catalytic reduction was studied over various catalysts in a fixed bed continuous flow reactor. The ranges of experimental conditions were at the temperatures between $200^\circ$C and $350^\circ$C, the $NH_3/NOx$ mole ratios between 0.8 and 1.4, oxygen concentrations between 1.5% and 3% and the space velocities between 5, 000 $hr^-1$ and 12, 500 $hr^-1$. The efficiency of NOx removal in the ranges of experimental conditions was highest at the temp. of 300$^\circ$C, oxygen concentration of 2.5-2.6% and $NH_3/NOx$ mole ratios of 1.0-1.2. The catalyst with high activity for NOx removal in flue gas was found to be $MoO_3-V_2O_5/TiO_2$.