Experimental study on stratified lean-burn of non-road small SI engine with supplemental side air-injection

A supplemental side air-injection (SAI) system for obtaining stratified lean-burn in a non-road small spark ignition (SI) engine was put forward and the comparative performance was experimentally investigated. A SAI port is bored through one side of the engine cylinder wall and connected with an induction channel through a solenoid valve. In the periods of intake and detonation strokes, compressed air for SAI is introduced into cylinder to produce strong swirl while the combustible mixture is inhaled through the intake valve to yield tumble. The compressed air is provided by an air tank and the intake timing is controlled by a high-speed solenoid valve. Comparative experiments about fuel consumption and emissions of a non-road small SI engine with SAI system were carried out. The tested results showed that the supplemental SAI system can improve fuel economy with a rate of fuel saving 37.17% at low-load condition and significantly decrease CO and HC emissions, but increase NO_x emission to a certain extent.