Air and fuel characteristics in a spark-ignition engine

Researchers are studying the interaction of air and fuel in the intake system of a port-fuel-injected spark-ignition engine.

The flow of air into internal-combustion engines and optimization of the fuel/air mixture in the intake port and cylinders are critical to the combustion process and reduction of exhaust-gas emissions. Thus engineers are investigating the fuel-spray and airflow interaction in the intake system of a spark-ignition (SI) engine, in isolation from the exhaust system and piston motion.

For the experiments, the cylinder head and intake manifold of a production five-cylinder SI engine were connected to a large-capacity plenum tank. An electrical motor at engine speeds between 1000 and 5000 rpm drove the camshaft of the intake valves, with air sucked through the system via a fan. The wave action in the primary runners of the simplified manifold system was representative of the dynamic effects of an engine, especially at high engine speeds. The velocities of airflow and fuel droplets were measured with a laser-Doppler anemometer through a window in the intake port of one cylinder.