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Flow near a spark plug is important for early flame kernel development (EFKD) and combustion efficiency. Velocity data have been measured by a laser Doppler velocimetry (LDV) for three different positions near a spark plug within a ported single cylinder optical spark ignition (SI) engine with a heart-shaped combustion chamber and a compression ratio of 8.9. LDV measurements have been performed under the wide-open motored conditions with an engine speed of 1,000 rpm conditions and maximum data collection rates of 22 kHz per channel. This work examines the mean and turbulence flow fields as interpreted through ensemble, cyclic, discrete wavelet transformation (DWT) analysis and the energy cascade as analyzed through continuous wavelet transformation (CWT) for flows near a spark plug.

At the present time there are rapid changes occurring in the fleets of transit buses that are used in cities. These changes involve improvements in conventional diesel buses, Compressed Natural Gas, CNG, and more recently hybrid electric vehicles. In order to evaluate the performance of the transit buses, driving cycles have been developed, and two of the most popular are the New York City, NYC, and the Central Business District, CBD. These cycles have proven to be very valuable for predicting both performance and emissions of the transit buses, however they do not well characterize some of the unique characteristics of certain cities, such as San Francisco with its hills and high grade. In this paper we present the results of Chassis dynamometer measurements and modeling of the performance of four different types of transit buses on the typical grades that exist in San Francisco.

In the immediate future the introduction of a wider variety of fuel types will play a significant role in reducing emissions and in solving the energy needs of the transportation industry. Both compressed natural gas, CNG, and hydrogen are expected to play very large roles, and the present paper shows that these fuels, when used together, can offer large benefits in NOx emissions. Significant reductions in NOx emissions will be required for CNG transit buses and heavy duty trucks, if they are to meet the future stringent emissions standards that come into effect in the year 2007. In the present paper a detailed engine model was used to understand and predict the results from engine dynamometer tests from a production automotive engine over a range of hydrogen/CNG gas fuel mixtures.

The early flame kernel development period has a strong influence on the ultimate performance and emission characteristics of spark ignition engines. The fibre-optic instrumented spark plug, FOSP, is a tool used to characterise the early flame kernel development period without the need to modify production engines. Simultaneous in-cylinder pressure, fibre-optic spark plug and secondary ignition system voltage measurements have been made in the GM 2.8 L and the high swirl 3.1 L production engines modified to run on a single cylinder. The secondary ignition system voltages indicate that restrikes are occurring and that spark anemometry is a promising tool to extract information about the flow near the spark plug at the time of ignition. Further development of the technique is, however, required.