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Technical Paper

Effects of Compression Ratio and Valve Overlap on Feasibility of HCNG Engines for Heavy-Duty Vehicles

To counteract the harmful effects of vehicle emissions on humans and the environment, such as global warming due to greenhouse gases, there is a focus on gaseous fuels as an alternative energy source of transportation. Heavy-duty natural gas vehicles are widely used to improve the air quality of urban areas in Korea because natural gas has the advantage of low greenhouse gas emission levels. However, more in-depth study is required in order for clean fuel vehicles to hold a dominant position over well-developed diesel vehicles. It is difficult to meet reinforced emission standards with only a lean combustion strategy without an aftertreatment system in a lean-burn natural gas engine. Hydrogen-natural gas (HCNG) blends have been proposed as an alternative to improve fuel economy and emissions of lean-burn natural gas engines, since they have a wider flammability range and faster burning speed. HCNG blends could also play a role as a technical bridge for the hydrogen era.
Journal Article

Performance and Emission Characteristics of a Diesel Engine Fueled with Pyrolysis Oil-Ethanol Blend with Diesel and Biodiesel Pilot Injection

The vast stores of biomass available worldwide have the potential to displace significant amounts of petroleum fuels. Fast pyrolysis of biomass is one of several possible paths by which we can convert biomass to higher value products. Pyrolysis oil (PO) derived from wood has been regarded as an alternative fuel to be used in diesel engines. However, the use of PO in a diesel engine requires engine modifications due to the low energy density, high acidity, high viscosity, and low cetane number of PO. Therefore, PO should be blended or emulsified with other fuels that have a high cetane number or used through pilot injection. PO has poor miscibility with light petroleum fuel oils; the most suitable candidate fuels for direct fuel mixing are alcohol fuels. Early mixing with alcohol fuels has the added benefit of significantly improving the storage and handling properties of the PO.
Technical Paper

Effect of Injection Timing Retard on ISI Strategy in Lean-burning LPG Direct Injection Engines

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.
Technical Paper

Development of a Rotating Plasma Burner for the Regeneration of Diesel Particulate Filters

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.
Technical Paper

Comparative Study on Effect of Intake Pressure on Diesel and Biodiesel Low Temperature Combustion Characteristics in a Compression Ignition Engine

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.
Technical Paper

Emission Characteristics of Gasoline and LPG in a Spray-Guided-Type Direct Injection Engine

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.
Technical Paper

Knock and Emission Characteristics of Heavy-Duty HCNG Engine with Modified Compression Ratios

Reduction of carbon dioxide (CO₂) emission, which causes global warming, is an important guideline for vehicle engine development. There are two types of methods for reducing the CO₂ emission of a vehicle engine. The first involves improving engine efficiency. The second involves the use of a low-carbon fuel, i.e., fuel with high hydrogen to carbon ratio. Hydrogen-compressed natural gas blend (HCNG) has been researched as a low-carbon fuel. Given that thermal efficiency of an engine cycle increases with its compression ratio (CR), an HCNG engine with high compression ratio not only has high efficiency but also low CO₂ emission. However, unexpected combustion such as knock could occur owing to the increased CR. In this study, we investigated the knock and emission characteristics of an 11-L heavy-duty HCNG engine with a modified CR. A conventional CNG engine was fuelled with HCNG30 (CNG 70 vol% and hydrogen 30 vol%).
Technical Paper

Combustion and Emission Characteristics of Heavy Duty SI Engine Fueled with Synthetic Natural Gas (SNG)

Natural gas produced from coal or biomass is known as synthetic natural gas (SNG), which is expected to replace compressed natural gas (CNG). In this study, we used an 11-l heavy-duty CNG engine in a feasibility study of SNG. SNG, which is composed of 90.95% methane, 6.05% propane, and 3% hydrogen, was produced for the experiment and used as fuel to estimate its effects on combustion and emission characteristics. The torque, fuel flow rate, efficiency, fuel consumption, combustion stability, combustion phase, and emissions characteristics obtained using SNG were compared to those obtained using CNG in an engine speed range of 1,000-2,100 rpm under full load conditions. In addition, an engine fueled with SNG was given an overall evaluation using the World Harmonized Stationary Cycle (WHSC) emission test. The engine's knock characteristic was analyzed at 1,260 rpm under a full load condition. The results showed that there was no difference in power output.
Technical Paper

The Research about Engine Optimization and Emission Characteristic of Dual Fuel Engine Fueled with Natural Gas and Diesel

CNG/diesel dual-fuel engine is using CNG as a main fuel, and injects diesel only a little as an ignition priming. In this study, remodeling an existing diesel engine into dual-fuel engine that can inject diesel with high pressure by CRDI (Common Rail Direct Injection), and injecting CNG at intake port for premixing. The results show that CNG/diesel dual-fuel engine satisfied coordinate torque and power with conventional diesel engine. And CNG alternation rate is over 89% in all operating ranges of CNG/diesel dual-fuel engine. PM emission is lower 94% than diesel engine, but NOx emission is higher than diesel engine. The output of dual fuel mode is 95% by the diesel mode. At this time, amount of CO₂ and PM are decreased while CO, NOx, and THC are increased. In NEDC mode, exhaust gases except NOx are decreased.
Technical Paper

An Experimental Study Combustion and Emission Characteristics of HCNG with Dual Spark plug in a Constant Volume Chamber

Finding an alternative fuel and solving the environmental pollution are the main targets for the future internal combustion engines. CNG(Compressed Natural Gas) bus is used for a public transportation in Korea because it has low carbon/hydrogen ratio and discharges low pollutant emissions. But CNG fuel has low burning rate. Therefore, in this study, hydrogen is added and DSP(Dual Spark Plugs) are used for making up for the demerits in CNG. HCNG(Hydrogen-CNG) as a fuel is now considered as one of the alternative fuels due to its low pollutant emissions and high burning rate. An experimental study was carried out to obtain the fundamental data about the combustion and emission characteristics of premixed hydrogen and CNG in a CVC(Constant Volume Chamber) with various fraction of Hydrogen-CNG blends using SSP(Single Spark plug) and DSP.
Technical Paper

Effect of Exhaust Gas Recirculation on a Spark Ignition Engine Fueled with Biogas-Hydrogen Blends

Efforts have been made to apply biogas to an IC engine for power generation as a way to cope with the energy crisis as well as to reduce greenhouse gas. However, due to its gas component variations by origin and low energy density, using biogas in the engine applications and achieving a steady power generation is not an easy task. One way to overcome these deficiencies is to add hydrogen in biogas. Because of the excellent combustion characteristics of hydrogen, use of hydrogen-biogas blend fuel can allow not only accomplishing stable in-cylinder combustion, but also reducing the harmful emissions such as THC and CO. Despite several advantages of this approach, there exists a major drawback~a significant increase in NOx emission caused by high adiabatic combustion temperature of hydrogen.
Technical Paper

Combustion and Emission Characteristics in a Direct Injection LPG/Gasoline Spark Ignition Engine

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.
Technical Paper

Experimental study on characteristics of diesel particulate emissions with diesel, GTL, and blended fuels

Various alternative diesel fuels such as gas to liquid (GTL) fuels, blends of diesel and biodiesel (D + BD20), and blends of GTL and biodiesel (G + BD20) were tested in a 2.0 L four-cylinder turbocharged diesel engine. A noticeable reduction in exhaust emissions as compared to diesel fuel, except for NOx emissions, was observed by blending biodiesel with diesel and GTL fuel under selected part load conditions. There was a maximum reduction of 33% for THC emissions and 27% for CO emissions for G + BD20 fuel as compared to diesel fuel. For PM size distributions, a noticeable decrease in the PM number concentration for all particle sizes less than 300 nm was observed with the blending of biodiesel. In contrast, there was a slight increase in the number concentration of PM with diameters of less than 50 nm for the cases of EGR. In the case of particulate matter (PM) mass concentration, there were reductions of 31~59% for D + BD20 fuel and 57~71% for G + BD20 fuel.
Journal Article

Improvement of DME HCCI Engine Performance by Fuel Injection Strategies and EGR

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.
Technical Paper

Characteristics of Syngas Combustion Based on Methane at Various Reforming Ratios

Characteristics of syngas combustion at various reforming ratios were studied numerically. The syngas was formed by the partial oxidation of methane to mainly hydrogen and carbon monoxide and cooled to ambient temperature. Stiochiometric and lean premixed flames of the mixtures of methane and the syngas were compared at the atmospheric temperature and pressure conditions. The adiabatic flame temperature decreased with the reforming ratio. The laminar burning velocity, however, increased with the reforming ratio. For stretched flames in a counterflow, the high temperature region was broadened with the reforming ratio. The maximum flame temperature decreased with the reforming ratio for the stoichiometric case, but increased for the lean case except for the region of very low stretch rate. The extinction stretch rate increased with the reforming ratio, implying that the syngas assisted flame is more resistance to turbulence level.