Pressure data measurements have been made in a single-cylinder, spark-ignition engine over 100 consecutive cycles. The engine was operated on natural gas at a wide range of engine speed and equivalence ratios. The effects of spark electrode geometry, combustion chamber geometry, spark gap and throttling have also been examined. From these pressure measurements standard deviations in burning times in mass-fraction-burned values were determined. Because of the existing evidence that the origin of cyclic variations is in the early combustion period, the standard deviations of cyclic variation in time required for a small (almost zero) mass-fraction-burned is estimated by extrapolation. These extrapolated values of standard deviation are compared with the implication of a hypothesis that cyclic variations in combustion in spark-ignition engines originate in the small-scale structure of turbulence (after ignition).
The nature of turbulence structure during combustion is deduced
from existing knowledge of mixture motion within the combustion chamber
of the engine. This research determines the turbulent parameters, such
as turbulence intensity, turbulent length scales and laminar burning
velocity. The standard deviation in burning times in the early stages
of combustion is estimated, within experimental uncertainty, by the
parameter ā/4uā where ā is the Taylor microscale and uā is the laminar
burning velocity of the unburned mixture. This parameter is the
consequence of the Tennekes model of small-scale structure of
turbulence and Chomiak's explanation of the high flame propagation
rate in regions of concentrated vorticity and the assumption that theignition behaves as though it were from a point source.
The general conclusion reached is that the standard deviation in the burning time for small mass-fraction-burned is associated with the early stages of burning-predictable from the knowledge of the Taylor microscale and the laminar burning velocity. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/28392 |
| Date | January 1988 |
| Creators | Kapil, Anil |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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