LiquidPiston, Inc. (LPI), the developer of engines based on its High Efficiency Hybrid Cycle (HEHC) (earlier post), has released a proof-of-concept video of its X Mini rotary engine applied in a go-kart.
LiquidPiston’s X Engine architecture is a non-Wankel rotary embodiment of the HEHC. The X Engine has few parts and three combustion events per rotor revolution, resulting in tremendous power density. The X Engine’s few moving parts consist of a rotor (the primary work-producing component) and an eccentric shaft. Except for ancillary parts such as injectors, fuel pumps, and oil pumps, there are no other moving parts.
|The X Mini 70cc rotary 4-stroke gasoline engine. Click to enlarge.
LiquidPiston’s HEHC combines the advantages of Diesel, Otto and Atkinson cycles. The cycle elements include:
For maximum efficiency, air is compressed to a high compression ratio, fuel is injected and compression ignited (CI-HEHC). The X Mini utilizes a spark-ignition (SI-HEHC) version of the cycle with a lower compression ratio standard for gasoline engines.
A dwell near top-dead-center forces combustion to occur at nearly constant-volume conditions.
Combustion products are over-expanded using a larger expansion volume than compression volume, as in the Atkinson Cycle.
Cycle-skipping power modulation allows high efficiencies at low power settings while simultaneously cooling the engine’s walls internally and providing partial heat recovery.
Water may be injected to internally cool the engine. Some of this cooling energy is recuperated, as the water turns to steam, increasing the chamber pressure.
To demonstrate the viability of the engine, the LiquidPiston team removed the go-kart’s traditional 39-pound engine, replacing it with the four-pound X Mini. Concurrent with the release of the video, LiquidPiston is allowing interested parties to place orders for the X Mini dev kit.
Last March, LiquidPiston signed a $1-million agreement with DARPA to develop fuel-efficient, lightweight, heavy-fueled, rotary combustion engine for the US Military. (Earlier post.)