Gyeung Ho Choi

The Effect of Hydrogen Enrichment on Exhaust Emissions and Thermal Efficiency in a LPG fuelled Engine

The concept of hydrogen enriched LPG fuelled engine can be essentially characterized as low emissions and reduction of backfire for hydrogen engine. The purpose of study is obtaining low-emission and high-efficiency in LPG engine with hydrogen enrichment. In order to determine the ideal compression ratio, a variable compression ratio single cylinder engine was developed. The objective of this paper is to clarify the effects of hydrogen enriched LPG fuelled engine on exhaust emission, thermal efficiency and performance. The compression ratio of 8 was selected to minimize abnormal combustion. To maintain equal heating value, the amount of LPG was decreased, and hydrogen was gradually added. In a similar manner, the relative air-fuel ratio was increased from 0.8 to 1.3 in increment of 0.1, and the ignition timing was controlled to be at MBT each case.

Investigation of Coal-Water Slurry Fuel Combustion in Reciprocating , Internal Combustion Engine

Coal-water slurry(CWS) engine tests designed to investigate the ignition and combustion processes of the fuel are described in this paper. The effects of three different parameters, namely, (a) needle lift pressure, (b) fuel injection timing, and (c) percent coal loading in the slurry fuel are studied in detail. Successful operation of the engine using the coal water slurry required modifications to the engine and support systems. The physical trends of combustion under single parametric variations are presented in terms of the cylinder pressure, heat release rates, and cumulative heat release curves. The major conclusions of the work include: (a) higher needle lift pressures led to shorter ignition delay times for the CWS fuel: (b) the ignition delay time of the advanced injection start was little different from that of retarded fuel injection timing due to poor atomization: and (c) dilution of the slurry with water can significantly affect the combustion processes and ease of fuel handling.

A numerical study of the effects of swirl chamber passage hole geometry on the flow characteristics of a swirl chamber type diesel engine

Abstract This research simulates the in-cylinder flow of a swirl chamber type diesel engine using a computational fluid dynamics (CFD) code and reveals the generation and distortion of swirling, tumbling vortices and their influence on turbulence kinetic energy depending on the shape, angle, and area of the jet passage. The CFD code was applied to the intake and compression processes. Results show that flow characteristics were affected by inflow velocity, which depends on the change in the jet passage shape. The swirl ratio was increased as a result of a decrease in the jet passage area. Turbulence kinetic energy was generated by mixing effects of the swirling and tumbling vortices.

Comparison study between mixer and liquefied petroleum injection system fuel supply methods in a heavy-duty single cylinder engine

Abstract The purpose of this study is to analyse the combustion and emission characteristics of a heavy-duty single cylinder engine (HDSCE) with a mixer and a liquefied petroleum injection (LPi) system. The mixer and LPi systems provide liquefied petroleum gas (LPG) in vapour and liquid phases throughout the intake manifold. Sensors such as the crankshaft position sensor (CPS) and Hall sensor supply spark and injection timing data to the ignition controller. An HDSCE runs at an engine speed of 800–1400 r/min, a compression ratio (CR) of 8, and a relative air-fuel ratio (Λ) value of 0.8–1.3. The major conclusions of this work include: LPi and mixer systems exhibit similar brake specific fuel consumption (b.s.f.c.) levels of 275g/kWh. Fuel efficiencies of LPi and mixer methods are almost identical. All these methods exhibit generally similar CO emission properties, and LPi wide-open throttle (WOT) and mixer WOT methods exhibit similar NOx emission properties.

An Experimental and Numerical Study of a Miller Cycle for a Gas Engine Converted From a Diesel Engine

Studies on internal combustion engines have made great efforts to develop engines with high efficiency for energy saving and emission gas reduction. The thermal efficiency of an internal combustion engine can be increased by expanding the pressure energy obtained through combustion to the maximum extent to convert the supplied thermal energy into work to the maximum extent. The cycle that can realize this goal is the Miller cycle. This Miller cycle converts the supplied thermal energy into mechanical energy to the maximum extent by making the expansion ratio greater than the compression ratio by changing the intake valve close timing. It is essential that study be performed for the development of the engine with high efficiency for energy saving in this era of rising oil prices. Therefore, this study realized a low compression and high expansion ratio engine by changing the intake valve close timing in order to investigate the characteristics of the Miller cycle. Furthermore, it confirmed that both the compression pressure and maximum combustion pressure increased through thermodynamic analysis. In addition, using the engine analysis program developed by the Ricardo Company known as WAVE, this study obtained the result that the output, torque and break thermal efficiency increased by 2 PS, 1.5kg and 2%, respectively at WOT (Wide Open Throttle) position and ABDC55° through simulation by changing the intake valve close timing.Copyright

Numerical Analysis of Flow Characteristics in a Swirl Chamber Type Diesel Engine Depending on Passage Hole Type

In a swirl chamber type diesel engine, a strong swirl is produced inside the swirl chamber during the compression stroke. By spraying the fuel into this chamber and thus forming a good mixture, the engine can obtain excellent combustion even at high speeds. Therefore, swirl chamber type diesel engines are favorable for high-speed operations, and because they can produce high power from a small size, they are used often for small, high-speed diesel engine applications. In order to simultaneously realize a reduction in harmful emissions and improvement in fuel consumption of the swirl chamber type diesel engine, reduction of the mixture formation period and complete combustion must be pursued; an optimum combustion chamber to achieve these tasks must first be designed. In this experiment, the effects of the area and the angle of the passage hole, which are the primary design factors of the swirl chamber type diesel engine, on the engine’s turbulent flow will be investigated. Using the commercial numerical analysis program the passage hole area and angle will be varied to analyze the intake and compression stages.Copyright