Characteristics of an Unthrottled, Auxiliary Chamber, Spark Ignition Engine 630514
The ignition of very lean fuel-air mixtures by means of a turbulent flame, and the operation of a stratified-charge engine employing a single, auxiliary combustion chamber to serve that requirement are considered. A suitable modification of the CFR engine demonstrates the principle. Results indicate a greater development potential to efficiently convert hydrocarbon fuels to mechanical energy at part loads than that which exists for the modern, conventional, spark-ignition engine. The system described is shown to be inherently rough from the combustion standpoint, but is less fuel sensitive, and does not recognize antiknock quality as a factor of major importance.
The effect of combustion chamber and fuel system design parameters on part-load economy, full-load combustion roughness, and air utilization are discussed in terms of experimental data. The relationship of the turbulent-flame engine to other experimental stratified-charge designs is briefly discussed. It is concluded that the advantages of stratified-charge engines of various types are such that their serious development and general use would lead to diminished importance of octane quality, and even volatility, as primary motor fuel specifications. The emergence of a single fuel for all internal combustion engines is therefore envisaged as the logical terminal result of engine-fuel development.