• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.84-89
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• 2014

Not only the emission regulation of on-road vehicle engine, but also emission regulation of off-road engine have been reinforced. It is the reason of wide application of emission reduction technology for off-road engines. In this study, optimization of engine parameters (Injector hole number, Injection timing and EGR rate) for reduction of NOx and smoke emissions were conducted by using the analysis of sensitivity and S/N ratio of Taguchi method(DOE). As results, this paper shows optimum value of the parameters for NOx and smoke emission reduction. From the result of reproducibility verification, it is final that the prediction value of NOx and smoke has the error of below 10%. Consequently, the method and results of this study will be used for quantitative reference to EGR control mapping in next study.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.91-97
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• 2023

Aging construction machinery and vehicles with old diesel engines usually have a long life span, so they continue to emit harmful emissions. Therefore, replacing these older diesel engines with engines that meet the latest emisstion standard is expected to help improve air quality, and engines with propane fuels, which are easily available at construction sites, can be an appropriate alternative. In this study, a propane fueled engine was developed based on a 6.8-liter CNG engine, and technologies such as gas injectors, exhaust gas recirculation (EGR), and enhanced catalysts were applied. As a result, nitrogen oxides achieved half of the emission performance at the Stage-V level, the latest emission standard, while securing diesel engine output and torque in the same class.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.139-148
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• 2013

In this study, an ejector was designed to recirculate the anodic off-gas of SOFC, and a parametric study of the system performance was conducted at various ejector entrainment ratios. Aspen Plus, a chemical engineering program, was used to calculate the operational conditions of the ejector. To minimize the calculation load of the CFD and to ensure the global optimum, a genetic algorithm and Kriging model were used for the optimization. The optimization results showed that the dominant design variables of the sonic ejector are the throat diameter and the first flow nozzle position. The designed ejector has enough flexibility for different operating conditions of a 1-kW SOFC system. When the ejector was applied to the SOFC, it reduced 56% of the steam and 8.4% of the fuel compared to the reference case.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.115-125
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• 2008

Recently, Exhaust Gas Recirculation (EGR) system which re-flow a cooled exhaust gas from vehicles burning diesel as fuel to a combustion chamber of engine has been used to solve the serious air pollution. For the design and mass production of EGR system, it is essential to ensure structural integrity evaluation. The EGR system consisted of ten dimpled oval core rectangular tubes, two fix-plates, two coolant pipes, shell body and two flanges in this study. To confirm the safety of the designed system, finite element modeling about each component such as the dimpled oval core tube with the dimpled shape and others was carried out. The reliability of EGR system against exhaust gas flow with high temperature was investigated by flow and pressure analysis in the system. Also, thermal and strength analysis were verified the safety of EGR system against temperature change in the shell and tubes. Furthermore, modal analysis using ANSYS was also performed. From the results of FE analysis, there were confirmed that EGR system was safe against the flow of exhaust gas, temperature change in EGR system and vibration on operation condition, respectively.

• Journal of ILASS-Korea
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• v.29 no.2
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• pp.60-67
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• 2024

This study compared exhaust gas recirculation (EGR) and excess air strategies for improving thermal efficiency and emissions of hydrogen combustion engines at low-load operation. The experimental investigation was conducted in a single-cylinder, heavy-duty engine under throttling and wide-open throttle (WOT) conditions. Although both EGR and excess air strategies reduced peak heat release rates and increased combustion durations, the net indicated thermal efficiencies were improved by reducing the pumping losses. Under the constraint of similar nitrogen oxides emissions, the EGR strategy had higher net indicated thermal efficiencies compared to the excess air strategy in throttling operation. However, the difference between their thermal efficiencies was reduced under WOT condition. The trend of reducing nitrogen oxides emissions according to the two strategies was similar.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.857-862
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• 2004

HCCI engines take advantage of high compression ratio and heat release rate, they exhibit high efficiency in compression ignition engines. HCCI engines also utilize a lean air/fuel ratio resulting in low emissions of NOx and particulate matter(PM). The objective of this research is to determine the effects of EGR rate on the combustion processes of HCCI. For this purpose, a 4-cylinder, compression ignition engine was converted into a HCCI engine, and a heating device was installed to raise the temperature of the intake air and also to make it more consistent. In addition, a pressure sensor was inserted into each of the cylinders to investigate the differences in characteristics among the cylinders.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.4
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• pp.24-31
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• 1985

본 논문은 Comprex압력파 과급기(Pressure-wave Supercharger;이하 PWS)의 공기 역학적인 원 리에 대해 기술하였으며, 또 기체 동력학적인 현상들이 별도의 제어장치없이도 우수한 운전성과 낮은 연료소모율, 적은 배기 배출물을 형성하는 차량들에 대해 기계적으로는 간단하면서도 완벽 한 boosting장치를 만들어 내는데 어떻게 사용될 수 있는지를 설명하였다. 근본적인 목적은 종 래의 turbo charger와 동일이지만 Comprex PWS는 현재 응용되고 있는 승용차가 요구하는 여러 가지면, 즉 1) 부하변동에 대한 충진공기압의 빠른 응답성 2) 엔진속도 전영역에 걸친 높은 boost 효과 3) 배기배출물특성을 좋게할 수 있는 배기가스 재순환(EGR)효과 등에서 종래의 것과 구별된다. 따라서 PWS의 중요한 특징들을 기술하였으며 마지막으로 최근 자동차용 Diesel Engine에의 몇 가지 예를 보았다.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.10-14
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• 2005

The Effects of cooled and hot EGR(exhaust gas recirculation) on the characteristics of smoke and NOx emission have been investigated using a single cylinder, water-cooled, four cycle, DI diesel engine at several loads and speeds. In this study, a manually controlled EGR system was installed on a agricultural diesel engine which was operated at various operating system. And, the effects of hot EGR and cooled EGR on smoke and NOx emission were compared. The results showed that cooled EGR method was more effective than hot EGR method on smoke and NOx emission.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.39-47
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• 2020

Flue gas recirculation(FGR) is an effective combustion technique for reducing nitrogen oxides(NOx) and is applied in various fields of low-pollution combustion. Continuing the previous study, a numerical analysis was conducted to identify changes of flame characteristics and NOx formation mechanism with applying FGR technique in CH₄/air premixed counterflow flames. NOx emitted was divided into four main reaction paths(thermal NO, prompt NO, N₂H and N₂O), showing relatively the production rate of NO with the recirculation ratio. As a result, thermal NO contributed greatly to the overall NO whereas the effect of N₂H was minimal. In addition, emission index of NO was compared as the recirculation ratio increased by modifying the UC San Diego mechanism to examine the contribution of thermal NO.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.140-156
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• 1997

The combustion characteristics of DI Diesel engine using turbocharging and EGR are numerically studied. Computations are carried out for the wide range of trubochyarged pressures, EGR ratios, and Ar/He dilution. Numerical results indicate that the Ar/He dilution in the intake gas significantly influence the engine performance, the spray combustion process, and the pollutant formation.