Formaldehyde for the premixed compression-ignition engine - an additive for ignition-timing control -

Lean fuel/air mixtures with various fuel/fuel ratios between methane and n-butane were supplied to a premixed compression-ignition engine (i.e. homogeneous charge compression ignition engine, HCCI) with or without supplementary gaseous formaldehyde induction as an ignition controlling additive. In the no additive case the methane and butane function as the two fuels in the high/low-octane two-fuel premixed compression-ignition operation we proposed previously as another ignition control procedure. The formaldehyde addition to the methane/ butane/air mixtures has given the engine desired and stable ignition timings controllable by the amount of formaldehyde to be added, almost independent on the fuel/fuel ratios between methane and butane. The efficacy of formaldehyde has been confirmed as an ignition controlling medium for the piston-compression ignition of hydrocarbon/air mixtures.