The fist-sized rotary engine that stole that show at the SAE International/JSAE 2014 Small Engine Technology Conference in Pisa, Italy, is your answer.
LiquidPiston's showed their X Mini, a four-stroke 70 cc engine that they scaled down from its
bigger brother, itself also a revolutionary (excuse the pun) tiny rotary engine.
Liquid Piston's co-founder, Dr Alexander Shkolnik, told Gizmag since the launch of the low-vibration, high-efficiency 50 kW rotary and 30 kW compression ignition engines in 2012, the U.S. company has been focused on bringing its cellphone sized engines to market.
Their small rotary internal combustion engines were developed to operate on the High Efficiency Hybrid Cycle (HEHC). The cycle, which combines high compression ratio (CR), constant-volume (isochoric) combustion, and overexpansion, has a theoretical efficiency of 75% using air-standard assumptions and first-law analysis.
The company said such rotary engine architecture can be up to 60% effective with a brake efficiency of over 50%. As this engine does not have poppet valves and the gas is fully expanded before the exhaust stroke starts, the engine is also relatively quiet.
Similar to the Wankel rotary engine, the ‘X’ engine has only two primary moving parts, a shaft and a rotor, which make it possible to miniaturise the engine and maintain very low vibrations.
Unlike a Wankel, the fuel is spark ignited. Despite its tiny size, the X Mini puts out 3.5 bhp and weighs a dense 1,3 kg. For a comparison how far technology has come in four decades, a 900 cc two stroke engine in a 1964 DKW made 43 hp.
Shkolnik said the 70 cc X Mini currently rates for 3,5 old fashioned horse power, but it will be further optimized to increase its output to over five horsepower, (3,7 kW) with even lower operational noise.
LiquidPiston predicts the X Mini will mainly power handtools but will next year offer a cash prize for the best ideas for employing the new technology.
The company aims to have the X Mini on the market by 2017.
