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Lee, Hyunjun,Park, Yeongseop,Sunwoo, Myoungho Professional Engineering Publishing Ltd 2014 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>Exhaust gas recirculation systems are used in diesel engines to reduce nitrogen oxide emissions. Since excessive recirculation in the cylinders may lead to an increase in generation of particulate matter and to unstable combustion, the exhaust gas recirculation rate should be measured correctly and should be controlled precisely. Unfortunately, the harsh conditions of the exhaust gas recirculation path make it difficult to measure the exhaust gas recirculation mass flow rate directly by using the relevant sensors. Therefore, precise control of the exhaust gas recirculation system depends on accurate estimation of the exhaust gas recirculation rate. To estimate accurately the exhaust gas recirculation rate in a turbocharged diesel engine, we propose an observer based on a model reference identification scheme. A linear parameter-varying model of the intake manifold pressure was derived to serve as the observer’s reference model. An update rule of the observer was designed with the model reference identification scheme. The intake and exhaust temperature models were developed through an empirical approach. Convergence of the proposed observer was proven in terms of the Lyapunov stability criterion. The proposed observer was implemented on a real-time embedded system and validated successfully through experiments on the engine.</P>
Baek, Sungha,Jin, Dongyoung,Jang, Wonwook,Myung, Cha-Lee,Park, Simsoo,Lee, Jeongmin Professional Engineering Publishing Ltd 2016 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>The nanoparticle emissions from gasoline direct-injection engines are of concern because of the high particle number concentrations compared with those from a gasoline port fuel injection engine. A gasoline particulate filter is a potential solution for reducing the particulate matter emissions. In this study, a 2.0 l turbocharged gasoline direct-injection vehicle with a metal-foam-type gasoline particulate filter was tested using the New European Driving Cycle and steady vehicle operating conditions. The particle number concentration, the particle-size distribution and the filtration efficiency were determined using a condensation particle counter and a fast response differential mobility spectrometer (DMS500). The particle number emissions (particle numbers per vehicle travelling distance (particles/km)) over the New European Driving Cycle were 1.95x10(12) particles/km for a base vehicle equipped with a three-way catalytic converter and 5.68x10(11) particles/km for the additional installation of a gasoline particulate filter on the base gasoline direct-injection vehicle. The filtration efficiency of the particle number and the particulate matter mass reached approximately 71% and 67% respectively. The nucleation-mode particles in the size range less than 23nm for the gasoline direct-injection vehicle equipped with a three-way catalytic converter were further reduced on installation of a gasoline particulate filter at the downstream position of the three-way catalytic converter. A sharp pressure drop between the gasoline particulate filter of 21.0 mbar was obtained at a vehicle speed of 120km/h in the New European Driving Cycle. The exhaust gas temperature before the gasoline particulate filter reached around 380-610 degrees C at steady vehicle speeds of 60-120km/h. The installation of the gasoline particulate filter has the potential to satisfy the Euro 6c particle number emissions regulations for light-duty gasoline direct-injection vehicles.</P>
Professional Engineering Publishing Ltd 2014 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>A novel bellows-type flow regulator was designed with the ability to maintain a steady thrust level and to adjust the thrust of a liquid rocket engine. The flow regulator showed good performance not only in maintaining the flow rate despite changes in the pressure difference across the flow regulator, but also in adjusting the flow rate in response to a changing shaft angle. A mathematical static model of the flow regulator was developed. A design criterion for ideal performance of the flow regulator was derived by theoretical analysis of the mathematical model. It was established that the main design parameters of the flow regulator affecting flow rate maintenance were the number and the width of ports in the 2nd throttle. The static characteristics predicted by the mathematical model show good agreement with experimental results, thus validating the mathematical model.</P>
Choi, Seungmok,Shin, Seung-Hyup,Lee, Jeongwoo,Min, Kyoungdoug,Choi, Hoimyung Professional Engineering Publishing Ltd 2015 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>This paper presents how injector nozzle distributions and the combustion chamber geometry affect the emission characteristics of diesel engines. The number of nozzle holes was increased from seven to 12 by a using double-row nozzle distribution to enhance the air–fuel mixing and the spatial distribution of the spray while avoiding spray overlap. The combustion chamber geometry was modified to have a wide shallow two-step bowl, which ensured adequate spray penetration with the double-row nozzle, to observe the influence of the spray–piston interaction on the combustion and emissions. Three hardware combinations (a seven-hole single-row nozzle with a conventional piston, a 12-hole double-row nozzle with a conventional piston, and a two-step piston) were tested in a single-cylinder direct-injection diesel engine under three boost and exhaust gas recirculation conditions. The injection timing was adjusted to result in a similar power by maintaining 50% of the total fuel mass fraction burned points for each hardware combination. For a conventional boost pressure (1.10 bar) and 30% exhaust gas recirculation, the 12-hole double-row nozzle with a conventional piston exhibited the best emission characteristics with a significant reduction in the particulate matter emissions. For a high boost pressure (1.30 bar) and 30% conventional exhaust gas recirculation, the nitrogen oxide emissions slightly increased and the particulate matter emissions decreased for the 12-hole double-row nozzle with a conventional piston compared with those for the seven-hole single-row nozzle. The two-step piston resulted in decreased particulate matter emissions but increased nitrogen oxide emissions under a high boost pressure. For 60% high exhaust gas recirculation, which is characterized by low-temperature combustion, the particulate matter emissions, the carbon monoxide emissions, and the total hydrocarbon emissions decreased simultaneously without an increase in the nitrogen oxide emissions using the 12-hole double-row nozzle with a two-step piston.</P>
Influence of gas-to-liquid fuel on the combustion and pollutant emission characteristics
Park, Su Han,Lee, Donggon,Lee, Chang Sik Professional Engineering Publishing Ltd 2014 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>The purpose of this work was to investigate the combustion performance and the pollutant emission characteristics of gas-to-liquid fuel in a passenger car’s diesel engine. In order to perform this study, the test facilities were set up on a 1.6 l four-cylinder compression ignition diesel engine with a common-rail injection system. Gas-to-liquid fuel combustion under a high-engine-load condition was compared with conventional diesel and biodiesel derived from soybean oil. The performance test results revealed that the gas-to-liquid fuel shows more rapid ignition than diesel and biodiesel do because of its high cetane number. The rates of increase in the combustion pressure in gas-to-liquid fuel and biodiesel were smaller than that in diesel, and the maximum rate of heat release from gas-to-liquid fuel was the lowest among the three test fuels. In terms of emission analysis, gas-to-liquid fuel shows a slight decrease in the nitrogen oxide emissions and significant reductions in the hydrocarbon and the carbon monoxide emissions compared with other test fuels. Meanwhile, the combustion of gas-to-liquid fuel indicates a lower concentration of soot emissions than those from conventional diesel but slightly higher than those from biodiesel owing to the variation in the low heating value parameter.</P>