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To investigate the combustion stability in a natural gas engine at idle, the burn parameters are determined on a cycle-by-cycle basis through the analysis of the engine pressure data. Combustion analysis based on cylinder-pressure provides a mechanism through which a combustion researcher can understand the combustion process. The parameters lowest normalized value (LNV) introduced by Hoard and Rehagen and coefficient of variation (COV) are used to investigate the combustion stability at idle. Measurements of combustion pressure are used to determine values for these parameters in a Ricardo research engine. The fuel used natural gas, and compression ratios between 6 and 14 are explored. The objective of this work is to identify whether these variables are a significant source of cycle-by-cycle combustion variability in a natural gas engine at idle.

A gasoline spark-ignition (SI) engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injection, but the combustion stability at idle is not improved compared to a carburetted engine. The combustion variability in SI engines limits the use of lean mixtures, the amount of recycled exhaust the engine will tolerate, and lower idle speeds because of increased emissions and poor engine stability. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of ignition energy, fuel injection timing, spark timing, and air-fuel ratio on gasoline engine stability at idle.

A gasoline engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injector, but the stability of engine operation at idle is not improved compared with a carburetted gasoline engine. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of fuel injection timing, spark timing, dwell angle, and air-fuel ratio on engine stability at idle.

A new empirical formula for instantaneous heat transfer coefficients was determined. The determination of this formula is in necessary for prediction of the instantaneous value of heat transfer coefficients to analyze in more detail the time variation of heat transfer rate from the gas to the wall in the combustion chamber of a spark ignition engine. The following formula was determined. Using this empirical formula the instantaneous heat transfer coefficients of gas in the combustion chamber of spark ignition engine was predicted and compared with experimental values.

Smoke is emitted in diesel engines because fuel injected into the combustion chamber burns with insufficient oxygen. The emission smoke from diesel engines is a very important air pollution problem. Smoke emission, which is believed to be largely related to the diffusion combustion in diesel engines, results from pyrolysis of fuel not mixed with air. Therefore, the smoke emission is dependent on diffusion combustion phenomena, which are controlled by engine parameters. This paper presents an analysis of combustion by relating the smoke emission with heat release in diesel engines. An analysis is made of the diffusion combustion quantity, the smoke emission, and the fraction of diffusion combustion as related to the engine parameters which are air-fuel ratio, injection timing, and engine speed.

The design and development of a turbocharged engine requires an understanding of the characteristics of engine performance and thermal flow. In this study a naturally aspirated gasoline engine was equipped with a turbocharger. A thin-film temperature probe was manufactured and was installed into the combustion chamber wall to measure the unsteady temperature. The unsteady heat flux at the combustion chamber wall was evaluated by a one dimensional unsteady conduction equation with the wall temperature and temperature gradient.

In order to realize lean burn engine by improving the ignitability of ignition system, the possibility about the adaptability of the Multi Spark Capacitor Discharge Igniter (MSCDI) was analyzed. The MSCDI had an effect on the increase of the ignition energy and discharge period, and it was excellent in high speed without noise. The result of engine test with the MSCDI shown about 10% extension of lean limit, and 5% increase of brake thermal efficiency than the ignition system with single spark ignition apparatus. And the coefficient of cycle variation in the IMEP was remarkably decreased.