A Single Cylinder Engine Study of Lean Supercharged Operation for Spark Ignition Engines

Charge dilution, due to the reduced combustion temperatures that it brings about, has long been proven as effective means of reducing Nitrogen Oxides (NOx) emissions in reciprocating engines. The extent of this dilution is practically bounded on the lean side of stoichiometric conditions by engine misfire or the point at which the combustion process is no longer sufficiently reliable to sustain engine operation within some specified limit. Extending this misfire limit of an engine becomes a worth while goal as it brings about further reductions in NOx emissions. Much work has been dedicated to reaching this end and several techniques have proven viable in natural gas fueled engines. This work explores potential synergies between two proven techniques for NOx reductions in lean-burn natural gas fueled engines, hydrogen enrichment of the natural gas fuel and application of laser spark ignition. Independently both techniques have been shown to provide significant NOx emissions reductions through lean limit extension in spark ignited gaseous fueled reciprocating engines [1–11, 13–15]. Here hydrogen is blended with natural gas at five different levels ranging from 0% to 40% by volume in a single cylinder engine. The mixtures are fired using a conventional spark plug based ignition system and then again with an open beam path laser induced breakdown spark ignition system. NOx emissions measurements were made at different levels including misfire conditions for each level of hydrogen enrichment with both ignition systems. Data are presented and the emissions and engine performance of two configurations are compared to determine realizable benefits that arise from combining the two techniques.

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A New Method of Investigating Piston Ring Friction Under Firing Conditions

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1243/pime_proc_1996_210_257_02 ◽

1996 ◽

Vol 210 (2) ◽

pp. 179-182

Author(s):

G R Paul ◽

I J Sixsmith

Keyword(s):

Piston Ring ◽

Spark Ignition ◽

New Method ◽

Single Cylinder ◽

Preliminary Results ◽

Single Cylinder Engine ◽

The Difference

A new method of investigating piston ring friction in a firing engine is described. Preliminary results are presented for a spark ignition four-stroke 15 cm3 single cylinder engine. Tests were carried out on both a ringed and ringless version of the same engine. From the difference in b.m.e.p. between the engines, the ring friction could be deduced under firing conditions. This friction increased linearly with speed.

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