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In Thailand, exhaust emission from automobile has been one of the major pollution problems. It is known that Intake Valve Deposit (IVD) causes poor driveability and deterioration of exhaust emissions, but there has been no established test method of IVD in Thailand. Toyota 1G-FE engine was selected for an IVD test. After the evaluation of IVD from various experiment using the matrix of various engine speed and load, the combination of 3000 rpm and 50% opened throttle was determined to be the most appropriate operating condition of this IVD test. This test method has good repeatability and can differentiate IVD weight from different fuels or additives. This new test method may be considered to be the standard IVD test method for Thailand in the future.

This study describes the ignition of methanol spray formed by an ultrasonic atomizer under sub-zero conditions and the design of the methanol combustor as a H2+CO generator, based on partial oxidation reaction, for cold starting methanol engines. The methanol spray formed by the ultrasonic atomizer was observed to be ignited using a conventional ignition system even at sub-zero temperatures. Analysis of the spray characteristics showed that this successful ignition was attributed to the high amount of methanol vapor generated, which results from the fine spray and low momentum. The combustor using the ultrasonic atomizer was designed and tested. The combustor produced gaseous starting fuel (H2+CO) satisfactorily by using an adequate air register.

Our aim to develop an engine to drive an emergency portable fire pump resulted in the development of a small-light-weight 2-stroke diesel spark ignition engine which utilized an ultrasonic atomizer. As the base engine we used a 499cc twin cylinder 2-stroke S.I. outboard motor engine. The fuel supply for this engine was controlled by a carburetor. In this original form it was not possible to run the base engine using only diesel fuel and although a mixture of diesel fuel and gasoline would run the engine it produced a large quantity of white smoke emissions. To solve these problems it became necessary to atomize the diesel fuel, improve the fuel-air mixture and facilitate easier combustion. First we installed an ultrasonic atomizer to the intake of the base engine. Due to the fine spray and low penetration produced by the ultrasonic atomizer we obtained good mixture and distribution.

This paper describes a fuel atomizer developed for S.I. engines based on ultrasonic vibrations. As the spray is characterized by fine droplet size and low penetration, it facilitates fuel movement and the formation of a homogeneous mixture. The spray behavior of this atomizer is easily influenced by ambient air motion. Therefore, the spray is most effectively delivered to the cylinders by precise injection timing. The ultrasonic atomizer disperses a fine spray over a wide flow rate range. A single cylinder engine fitted with the atomizer showed advantages in combustion speed and transient response performance. When used in a commercial SPI engine, the ultrasonic atomizer maintained constant A/F distribution in all cylinders with no geometrical modification of the intake manifold. In cold weather conditions, the atomizer demonstrated excellent startability.