Fuel Consumption and Emission Reduction of a Small Two-Stroke Engine Through Air-Assisted Fuel Injection and Delayed-Charging

The classical small two-stroke engine is mechanically simple with a high power-to-weight ratio. But direct fuel losses are high and therefore induce a high fuel consumption and an unacceptable pollution level. We have developed a simple device (named Delayed-Charging) which is able to largely reduce fuel losses by almost separating the scavenging and fuel-charging functions and, consequently, retaining the major part of delivered fuel in the cylinder. Recent improvements, by use of an air-assisted injection combined with an air curtain to deviate the fuel spray trajectory throughout the cylinder, lead to a further reduction of hydrocarbon emission level from 4% (FIDHC methane equivalent) in a standard carbureted engine down to a 1% level associated to a fuel consumption reduction within a larger speed range in our newly modified 50 cc engine.

To better understand the behavior of the fuel flow, a local instantaneous fuel-concentration measurement in the exhaust duct by a continuous Laser Induced Fluorescence (LIF) process (with a Argon Laser beam) is associated to the continuous mean measurement of HC emission, giving information on the fuel transport and utilization throughout the engine.