• Journal of Power System Engineering
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• v.17 no.6
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• pp.18-24
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• 2013

An experimental study was performed to investigate the characteristics of combustion pressure and exhaust emissions when the pilot injection timing and EGR rate were changed in a CRDI 4-cylinder diesel engine. The pilot injection timing and EGR rate have a significant impact on the combustion and emission characteristics of diesel engine. In this study, the pilot injection timing and EGR rate variation were conducted to 2000rpm of engine speed with torque 50Nm. Combustion pressure and heat release rate were decreased under high EGR rate conditions but increased under the pilot injection timing $20^{\circ}$(BTDC). IMEP and the maximum pressure in cylinder(Pmax) were decreased under the same injection timing with the increase of EGR rate. The NOx emission was decreased with increasing the EGR rate. On the other hand, in the same injection timing conditions, CO, HC, $CO_2$ emissions were increased with increasing the EGR rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.64-70
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• 2007

Raising exhaust gas temperature during cold-start period is very crucial to improve emission performance of SI engines because it enhances the performance of catalyst in the early stage of engine start. In this study, control variables such as ignition timing, idle speed actuator(ISA) opening and fuel injection duration were extensively investigated to analyze variations in exhaust gas temperature and engine stability during cranking period. Experimental results showed that spark timing affected engine stability and exhaust gas temperature but the effects were small. On the other hand, shortened injection duration and increased ISA opening led to a significant increase in exhaust gas temperature. Under such conditions, increase in cranking time was also observed, showing that it becomes harder to start the engine. Based on these observations, a pseudo fuel-air ratio, defined as a ratio of fuel injection time to degree of ISA opening, was introduced to analyze the experimental results. In general, decrease in pseudo fuel-air ratio raised exhaust gas temperature with the cost of stable and fast cranking. On the contrary, an optimal range of the pseudo fuel-air ratio was found to be between 0.3 to 0.5 where higher exhaust gas temperatures can be obtained without sacrificing the engine stability.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.1-13
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• 1997

The key point that guarantees the durability of the ceramic monolith filter is to lower peak temperature and temperature gradient inside filter during regeneration. The control of the exhaust gas flow rate into the filter, by the bypass technique of the exhaust gas, enables the gas temperature in filter to be constant for regeneration. A couple of methods, which are the ON/OFF and PID control of the bypass valve, were used for feedback control of the gas temperature. These techniques showed that the ceramic filter was regenerated perfectly under the peak temperature and peak temperature gradient limitations for durability.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.13-19
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• 2008

Among the various prime movers for combined heat and power (CHP) system, the CNG engine is the most commonly used power generation equipment of which power is less than 1MW. The 300 kW class CNG engine for CHP can meet stringent emission regulations with the adoption of stoichiometric air-fuel ratio control and three way catalyst. As the thermal efficiency of the stoichiometric ratio engine is lower than that of lean burn engine, it is necessary to operate the stoichiometric engine at its minimum spark advance for the best torque (MBT). However, knock control should be introduced for the engine under high intake air temperature conditions because MBT operating conditions are generally very close to those of knock occurrence. In this study, engine performances and knocking characteristics were experimentally investigated for the CNG engine that needs to be operated at higher intake air temperature conditions than normal conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.727-734
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• 2015

Recently, because of the increased oil prices globally, there have been studies investigating the improvement of fuel-conversion efficiency in internal combustion engines. The improvements realized in thermal efficiency using lean combustion are essential because they enable us to realize higher thermal efficiency in gasoline engines because lean combustion leads to an increase in the heat-capacity ratio and a reduction of the combustion temperature. Gasoline direct injection (GDI) engines enable lean combustion by injecting fuel directly into the cylinder and controlling the combustion parameters precisely. However, the extension of the flammability limit and the stabilization of lean combustion are required for the commercialization of GDI engines. The reduction characteristics of three-way catalysts (TWC) for lean combustion engines are somewhat limited owing to the high excess air ratio and low exhaust gas temperature. Therefore, in the present study, we assess the reaction of exhaust gases and their production in terms of the development of efficient TWCs for lean-burn GDI engines at 2000 rpm / BMEP 2 bar operating conditions, which are frequently used when evaluating the fuel consumption in passenger vehicles. At the lean-combustion operating point, $NO_2$ was produced during combustion and the ratio of $NO_2$ increased, while that of $N_2O$ decreased as the excess air ratio increased.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.1-10
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• 2023

Due to the development of the industrial revolution, regulations on exhaust emissions have been continuously strengthened to reduce the rapidly increasing greenhouse gas emissions. The use of environmentally friendly fuels is essential to meet these regulations. Hydrogen has been attracting attention as a future environmentally friendly fuel, but due to its material properties, it faces significant challenges in handling and storage. As an alternative, ammonia has been proposed. Ammonia can be easily liquefied at room temperature compared to hydrogen and has a high energy density. In order to examine the applicability of ammonia as an engine fuel, experiments were conducted to investigate the effects of changes in combustion control parameters in a direct injection ammonia combustion engine. The experiments were conducted by varying two variables: spark timing and excessive air ratio. Observations were made on combustion stability and the trends of exhaust emissions such as nitrogen oxides and unburned ammonia under the conditions of an engine speed of 1,500 rpm and medium to high loads (brake torque of 200 Nm). By optimizing the combustion control parameters, conditions for stable combustion even when using ammonia as the sole fuel were identified, and plans are underway to apply strategies for future expansion of the operating range.

• Journal of the Korean Institute of Gas
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• v.22 no.3
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• pp.74-83
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• 2018

Anyone who wants to install local ventilation system must obtain a permission from the Ministry of Employment and Labor even if he has permission from the Ministry of Environment. This is because not only the Atmospheric Environmental Protection Act, but also the manufacturing industry's hazardous risk prevention plan under Article 48 Clause 2 of the Industrial Safety and Health Act is to be submitted by 15 days before the construction. Under the current Environmental Protection Act, the Ministry of Environment regulates only the emission of pollutants from local exhaust ventilation systems into the atmosphere and the contents of workers' safety and health within industrial sites are managed by the Ministry of Employment and Labor. Even with the approval of the Ministry of Environment, the number of unsuccessful cases by the Ministry of Employment and Labor has increased, causing a growing discontent among the sites due to production delays and additional costs of improvement. In addition, local exhaust systems that are at greater risk of fire explosion have increased the risk of severe industrial accidents due to fire explosion. This is due to insufficient design of air volume, control speed, return speed, duct size, and risk of fire explosion. This is because the criteria and procedures for approval of local exhaust ventilation systems are similar, but the Industrial Safety and Health Act adds additional screening items for safety and safety of workers and fire and explosion. In this study, the Environment Ministry and the Employment and Labor Ministry seek to find a reasonable way to operate the system by comparing local exhaust ventilation system installation approval standards.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.217-224
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• 2012

In general, transportation sources include both on-road vehicles and off-road equipment. Off-road vehicles have usually used diesel engines, which have the disadvantage of high NOx emission. Common rail direct injection (CRDI) and after-treatment systems have been applied to meet the exhaust gas emission regulations for diesel vehicles. In the present, agricultural machinery has satisfied the Tier 3 emission regulations by using waste gate turbocharger (WGT) and internal exhaust gas recirculation (EGR). In this paper, the combustion and emission characteristics of an EGR system applied to a 56kW off-road vehicle in non-road transient cycle (NRTC) mode have been investigated. The EGR map was made from foundation experiments determining the EGR duty for all engine operating conditions, and then this map was applied to the NRTC mode. Consequently, the NOx emission was reduced by the EGR system, and the Tier 4 interim emission regulations were satisfied by using both the EGR system and an after-treatment system.

• Journal of the KSME
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• v.35 no.6
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• pp.542-553
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• 1995

복합열병합 발전 플랜트의 장점은 도시 근교에 발전 플랜트를 간단히 건설할 수 있으며, 공해를 크게 줄이면서 독립적인 발전이 가능하다는 측면에서 신도시, 신공업단지, 도서지방 등에서 아주 유리한 것으로 알려져 있다. 또한 가스 터빈 배기열을 이용하여 대규모 주거 지역이나 공업 단 지내에서 필요한 난\ulcorner냉방열이나 공업열원으로의 활용이 손쉬우며, 주변 시설이 복잡하지 않고, 개선된 연소기술에 의하여 공해를 크게 줄일 수 있다. 최근 들어 분당\ulcorner일산\ulcorner부천 지역 등에 열병합 플랜트가 건설되고 있으나 거의 모든 설계기술은 외국 기술에 의존되고 있으며, 국산화 율도 극히 저조하여 '93년도에 완공된 부천 화력(473MW)의 경우 약 30% 정도이다. 복합열병합 발전 시스템은 가스 터빈, 스팀 터빈 등의 터보기계 기술을 근간으로 하며, 열회수장치 및 열교 환장치의 설계기술, 각종 제어기술 등의 종합 설계기술로서 이미 선진국에서는 실용화된지 오 래되었으며 우리 나라에도 여러 종류의 플랜트가 도입되어 사용되고 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.177-177
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• 2010

티타늄 화합물은 뛰어난 물리적 특성과 인체 무해성을 가지고 있어 생체, 내식 및 내마모 재료 등에 널리 응용되고 있으며, 다양한 색상 구현을 통한 미려한 외관 등 기능성을 위한 표면처리 분야에도 많은 관심을 받고 있다. 이중 질화 티타늄은 금색을 대체할 수 있는 물질로 코팅방법과 기판온도, 바이어스, 질소유량 등과 같은 공정변수 제어를 통해 그 물성을 변화시킬 수 있어 기능적 측면과 함께 미려한 외관처리에 응용이 가능하다. 본 연구에서는 아크(cathodic arc) 코팅 시스템을 이용하여 다양한 조건에서 TiN 박막을 제조하고 그 특성을 평가하였다. 아크 장비는 화합물 박막을 코팅할 수 있는 아크 소스와 시편 홀더, 가스 주입구, 시편 가열장치 그리고 배기 장치로 구성되어 있고, 아크 소스에 장착된 타겟은 99.5%의 Ti 타겟을 사용하였다. 시편과 타겟 간의 거리는 약 31cm이며, 시편은 알코올과 아세톤으로 초음파 세척 된 강판(냉연 강판), 실리콘 웨이퍼를 사용하였다. 시편을 진공용기에 장착하고 ${\sim}10^{-6}$ Torr까지 진공배기를 실시하고, Ar 가스를 진공용기 내로 공급하여 ${\sim}10^{-4}$ Torr에서 시편에 bias (Pulse : 400V)를 인가한 후 아크를 발생시켜 약 5분간 청정을 실시하였다. 플라즈마 청정이 끝나면 시편에 인가된 bias를 차단하고, 질소 유량, 온도, bias, 시간 등의 공정변수에 따라 코팅을 실시하였다. 질소의 유량이 80sccm 일 때, Ti 금속 결정구조가 나타났는데, 이는 질소와 충분하게 반응하지 못한 Ti이 기판에 코팅되어 나타나는 현상으로 판단된다. 색상변화에서는 질소 유량이 증가함에 따라 노란색이 짙어지며, TiN은 시편에 인가되는 bias 전압이 높아질수록 붉은색이 증가하고, 온도에 따른 큰 변화는 관찰되지 않았다. 공정변수에 따른 반사율 변화는 TiN의 경우 질소 가스 유량이 200sccm, bias 150V, 공정 온도 200도에서 반사율이 가장 높았으며, 코팅 시간이 짧을수록 반사율이 높아지는 경향을 나타냈다. 따라서 본 연구에서 얻어진 결과를 외관 코팅 분야에 응용한다면 장식성과 외관의 경도, 내마모성, 내식성의 향상 등 많은 장점을 가질 것으로 예상된다.