Several studies are currently dealing with the so-called ‘new generation two-stroke engines’. In nearly all these, charge control by means of fuel injection has been proposed to overcome the well-known problems of fuel and lube-oil consumption, and the probably unacceptable level of pollutant emissions. Direct injection, in particular, seems to guarantee the best results as it allows to avoid the short-circuiting of the fuel to the exhaust.
The direct-injection systems proposed in recent times do not seem to be widely applicable especially to small two-stroke engines as they introduce considerably complicated and consequently high-cost systems.
A new direct injection system, based on the hydraulic phenomenon commonly known as “water hammer”, has been proposed by the authors as a reliable means of achieving high injection pressures while maintaining the simple manufacturing and low-cost characteristics of two-stroke engines. Though ideal for small two-stroke engines this concept appears suitable also for every other kind of spark-ignited engine.
The system, equipped with a low-pressure fuel pump, provides high injection pressure values thanks to the conversion of the kinetic energy of the fluid into a local pressure rise which takes place when the fuel flow is suddenly halted by an automatic valve.