Katsumi Kataoka

Fundamental Study on Combustion Improvement by Mixture-Flow in Natural Gas-Fueled Lean-Burn SI Engines

For the final goal of developing the natural gas-fueled spark-ignition engines with high thermal efficiency and low pollutant emission, the effects of the fluid flow inside a combustion chamber on the combustion process of a homogeneous lean methane/air mixture were examined using a rapid compression combustor. The rapid compression combustor was designed to simulate the combustion process in a spark-ignition engine involving the rapid compression of a mixture and the heat release during the flame propagation. The main advantage of using this combustor is that experiments can be made under the idealized and well-controlled conditions. The time history of pressure in the combustion chamber was measured with a pressure transducer. The fluid flow in the combustion chamber was varied as follows; the mixture was injected into the combustion cylinder before the compression stroke, and the direction of the injection and the time interval between the end of mixture charge and the start of compression stroke were varied. The position of spark ignition was also varied. And the flame propagation was photographically observed. Moreover, the two-dimensional velocity distribution of the swirl flow was measured with particle image velocimetry. As expected, the combustion duration decreased with increases in the mean velocity and the turbulence intensity of the fluid flow. When the intense swirl flow existed in the combustion chamber, the combustion duration was minimized with spark ignition at the eccentric location.

Effects of Piston Design and Inlet Gas flow on the Performance and Exhaust Emissions in a Natural Gas Fueled Spark Ignition Engine.

An experimental study was made on a natural gas fueled spark ignition engine to improve its thermal efficiency and exhaust emissions by the lean burn operation. A multi-cylinder engine was tested for purposes of practical application. Investigated were the effects of the piston design and the gas motion induced by a shrouded inlet valve on the combustion process, the thermal efficiency, exhaust emissions and the lean limit of stable operation. It was found that a bowl-in-piston resulted in higher thermal efficiency and extended lean limit as compared with a flat piston. A shrouded inlet valve generally resulted in shorter duration of combustion, lower NOx emissions and lower thermal efficiency than a conventional valve. When a shrouded inlet valve was set so as to direct the mixture flow toward the prechamber throat, the lean limit was extended with low exhaust emissions and relatively high thermal efficiency.

Effect of the Factors of Combustion Chamber on the Performance and Exhaust Emissions in a Natural Gas Fueled Spark Ignition Engine

An experimental study was made on a natural gas fueled spark ignition engine to improve its thermal efficiency and exhaust emissions by the lean burn operation. A multi-cylinder engine was used to obtain the data for practical application. Investigated were the effects of the throat area of the orifice which separated a prechamber from a main chamber, the position of ignition spark in the prechamber and the compression ratio on the thermal efficiency, the exhaust emissions and the lean limit of stable operation. The results showed that a small throat area resulted in low emissions of NOx, low thermal efficiency and narrow lean limit. The spark ignition at the center of prechamber or near the throat was preferable to the top of prechamber in terms of the thermal efficiency. Higher compression ratio resulted in shorter combustion duration, higher thermal efficiency and extended lean limit.

Effect of Fuel Properties on the Performance of a Spark Ignition Engine.

The coming shortage of crude oil supply and the demand for environmental conservation has resulted in an increased interest in introducing alternative fuels for internal combustion engines. The objective of the present work is to identify the role of the properties of various liquid fuels in the performance of a spark ignition engine. Fuels tested were methanol, ethanol, isooctane, benzene and regular gasoline. Attention was focused mainly on the chemical aspect of the fuel properties, while the influence of physical parameters was minimized. A test engine was devised so as to allow the liquid fuel to vaporize well and to mix with fresh air prior to being charged inside the combustion chamber. The mixtures were observed by means of the laser light scattering method. The cylinder pressure, rate of heat release, combustion duration, thermal efficiency and NO emissions were measured.

Computational Estimation of the Performance of a S.I. Engine with Various Fuels

The performance of a spark ignition engine operated with various fuels was calculatedly estimated by the computer model. The difference of thermal efficiency and NO emissions among fuels was derived mainly from the difference of flame temperatures. The cycles operated on alcohols or paraffines yeild high thermal efficiency and low emissions of NO owing to their comparatively low flame temperatures. On the contrary, when acetylene, hydrogen or benzene is used as a fuel, the flame temperatures rise high enough to cause the deterioration of the efficiency because of thermal dissociation, resulting in fairly high emissions of NO, especially with lean mixtures. Provided that hydrogen is used under its stoichiometric mixture, the NO emissions are relatively low.