A Compound Cycle Employing Two-Stage Combustion to Reduce Automotive Air Pollution

This paper presents a compound engine concept that has the potential of significantly reducing exhaust emissions. This cycle is based on a combination of components of the spark-ignition engine and the gas turbine. The cycle utilizes a two-stage combustion process involving fuel-rich combustion at high temperatures to reduce NO_x formation and followed by lean burning to eliminate unburned hydrocarbons in a thermodynamically productive manner. A thermodynamic analysis of this cycle and a comparison with the conventional otto cycle is presented. The combustion processes involved are examined and methods of implementing this cycle in a practical manner are shown. The results of this analysis indicate that a practical automotive power cycle with excellent part load and transient response characteristics is possible via this approach.