Gas Assisted Jet Ignition of Ultra-Lean LPG in a Spark Ignition Engine

Gas assisted jet ignition is an advanced prechamber ignition process that allows ignition of ultra lean mixtures in an otherwise standard spark ignition engine. The results presented in this paper indicate that in a gas assisted jet ignition system fuelled with LPG in both the main chamber and prechamber, the lean limit can be extended to between λ = 2-2.35, depending on the load and speed. Although the fuel combinations that employ H₂ as the prechamber fuel can extend the lean limit furthest (λ = 2.5-2.6), the extension enabled by the LPG-LPG prechamber-main chamber combination provides lower NOx emission levels at similar λ. In addition, when LPG is employed in place of gasoline as the main chamber fuel, hydrocarbon emissions are significantly reduced, however with a slight penalty in indicated mean effective pressure due to the gaseous state of the LPG. The results of this paper show the potential of a sole fuel gas assisted jet ignition system that employs LPG as both the main chamber and prechamber fuel. Such a system would enable the lean burn of a commercially available alternative fuel, without the difficulties of storing a separate prechamber fuel or onboard reforming, both problems currently associated with hydrogen assisted jet ignition (HAJI).