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Diesel burners have been used to regenerate diesel particulate filters (DPF) because of their simplicity in engine torque control and less oil dilution by fuel compared with the commonly used in-cylinder post fuel injection method. We previously developed a novel diesel burner using rotating plasma as an ignition source and found it to be effective in DPF regeneration. Here, we carry out in-depth studies on combustion efficiency of this plasma-ignited diesel burner and investigate the effects of influential factors such as plasma power, the amount of fresh air supplied, and O2 concentration in the exhaust gas on combustion characteristics of the burner. The obtained results show that fresh air supplied to the burner plays an important role in ignition and the early stage of combustion, and O2 concentration in the exhaust gas is identified as the most dominant factor for combustion efficiency.

One of most effective NOx control technology of modern diesel engines is SCR with ammonia. Current NOx reduction systems are designed to use a solution of urea dissolved in water as a source of ammonia. However, the liquid urea systems have technical difficulties, such as a freezing point below −11°C and solid deposit formation in the exhaust temperature below 200°C. The objective of this study is to investigate the possibility of a new ammonia generation system that uses low-cost solid ammonium salt, such as solid urea and ammonium carbonate. The result shows that ammonium carbonate is more suitable than solid urea because of low decomposition temperature and no change to the other ammonium salt during the decomposition process. This paper also shows the NOx reduction capability of the new ammonia delivery system that uses ammonium carbonate.

Owing to the presence of oxygen atoms in biodiesel, the use of this fuel in compression ignition (CI) engines has the advantage of reducing engine-out harmful emissions. In this context, biodiesel fuel can also be used to extend the low temperature combustion (LTC) regime because it inherently suppresses soot formation within the combustion chamber. Therefore, in this study, LTC characteristics of biodiesel were investigated in a single cylinder CI engine; the engine performance and emission characteristics with biodiesel and conventional petro-diesel fuels were evaluated and compared. A modulated kinetics (MK)-like approach was employed to realize LTC operation. The engine test results showed that LTC operation was achieved by retardation of the fuel injection timing. The results also showed that using biodiesel reduced smoke, THC, and CO emissions but increased NOx emissions.

Because of the concerns regarding global warming caused by greenhouse gases and the high cost of fossil fuels, research on improving the fuel economy and emissions in internal combustion engines has become important. Specifically for spark ignition engines, lean-burning direct injection is the most promising technology because the fuel economy and emissions can be improved using a stable combustion of a stratified mixture. This study aimed to develop a spray-guided, lean-burning liquefied petroleum gas (LPG) direct injection engine through optimizing the combustion parameter controls. In previous research, the brake thermal efficiency in an LPG direct injection engine was significantly increased and stable combustion was secured with an interinjection spark ignition (ISI) strategy under low-load operating conditions.

A Diesel Particulate Filter (DPF) is an effective technology for reducing Particulate Matter (PM) emitted from diesel engines. In modern light duty diesel engines, DPF is regenerated by the post-fuel-injection method. In this method, the fuel is injected into the combustion chamber during the expansion stroke to produce heat to burn out the PM trapped in the DPF. However, this method also causes several problems, such as complicated engine torque control and oil dilution by fuel. In this study, a rotating plasma burner was developed for DPF regeneration as an alternative to the postfuel-injection method. Since it is important to reduce the electric energy consumption for plasma generation, which is directly related with electric noise and system cost, several design factors, such as the boosting voltage of transformers, electrode gaps, and plasma frequency were evaluated. A transformer with a low boosting voltage is desirable to ensure low electric noise.

Diesel engine is being used widely in many industrial fields, as it provides merits in the aspects of higher thermal efficiency and less CO₂ emission. However, NOx regulations for diesel engines are being strengthened and it is impossible to meet the emission standard without aftertreatment systems such as SCR (Selective catalytic reduction), LNC (Lean NOx catalyst), and LNT (Lean NOx trap). Among the NOx reduction aftertreatments, Urea-SCR system is known as the most stable and efficient method to solve the problem of NOx emission. But this device has some issues associated with the ammonia slip phenomenon which is occurred by shortage of evaporation and thermolysis time, and that makes it difficult to achieve uniform distribution of the injected urea.

Nowadays, automobile manufacturers are focusing on reducing exhaust-gas emissions because of their harmful effects on humans and the environment, such as global warming due to greenhouse gases. Direct injection combustion is a promising technology that can significantly improve fuel economy compared to conventional port fuel injection spark ignition engines. However, previous studies indicate that relatively high levels of nitrogen oxide (NOx) emission were produced with gasoline fuel in a spray-guided-type combustion system as a result of the stratified combustion characteristics. Because a lean-burn engine cannot employ a three-way catalyst, NOx emissions can be an obstacle to commercializing a lean-burn direct injection engine. Liquefied petroleum gas (LPG) fuel was proposed as an alternative for reducing NOx emission because it has a higher vapor pressure than gasoline and decreases the local rich mixture region as a result of an improved mixing process.

Combustion and emission characteristics of LPG(Liquefied Petroleum Gas) and gasoline fuels were compared in a single cylinder engine with direct fuel injection. While fuel injection pressure and IMEP(indicated mean effective pressure) were varied with 60, 90, 120 bar and 2 to 10 bar, another parameters for the engine operation as engine speed, air excess, and fuel injection timing were fixed at 1500 rpm, 1.0, and BTDC 300 CA respectively. Experimental results showed that MBT timing for LPG was less sensitive to IMEP, and high injection pressure made combustion stability worse at IMEP=2 bar. Through heat release analysis LPG showed shorter 10 and 90% MBD(mass burn duration) than gasoline due to fast flame speed and for both fuels injection pressure hardly affected burn duration. It was also found that thermal efficiency of LPG had a little higher than that of gasoline. Hydrocarbon emissions of gasoline rose to a level of three-fold than those of LPG.

The combustion and exhaust emission characteristics of a DME fueled HCCI engine were investigated. Different fuel injection strategies were tested under various injection quantities and timings with exhaust gas recirculation (EGR). The combustion phase in HCCI was changed by an in-cylinder direct injection and EGR, due to changes in the in-cylinder temperature and mixture homogeneity. The gross indicated mean effective pressure (IMEPgross) increased and the hydrocarbon (HC) and carbon monoxide (CO) emissions decreased as the equivalence ratio was augmented. The IMEPgross with direct injection was greater than with the port injection due to retarded ignition timing resulting from latent heat of direct injected DME fuel. It was because that most of burn duration was completed before top dead center owing to higher ignitability for DME with high cetane number. However, HC and CO emissions were similar for both injection locations.