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Optimising the Spark Ignition Pre-Chamber Geometry Including Spark Plug Configuration for Minimum Nox Emissions and Maximum Efficiency
Technical Paper
825004
Sector:
Language:
English
Abstract
Simulation studies of spark ignition engine combustion including
the effects of cycle-by-cycle variability on emissions and thermal
efficiency demonstrated that there exists a desirable regime of
engine operation.
This paper reports the achievement of these conditions in a
single cylinder CFR engine through the use of a precombustion
chamber. This engine was instrumented for flame mapping, combustion
heat release and emissions analysis. Combustion rates could be
varied by the adjustable geometry (volume and throat area) of the
pre-chamber. The location of the spark electodes and their
configuration could also be changed. Experimental search through a
multi-dimensional matrix of geometries, air-fuel ratios, spark
timing, manifold pressure, engine speed and compression ratio
demonstrated that 15% improvement in relative thermal efficiency
coupled with 70% reduction in NOx could be simultaneously
achieved.
The design of the near optimal pre-chamber for this engine is
reported. The location of the ignition source and the orientation
of the spark electrodes proved to be a dominant variable. The
traditional location of the spark gap at the closed end of the
pre-chamber proved to be least satisfactory.