HEHC Cycle

LiquidPiston’s HEHC is a patented thermodynamic cycle that combines the advantages of Diesel, Otto and Atkinson thermodynamic cycles. The cycle elements include:
  1. Compression: 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.
  2. A dwell near top-dead-center forces combustion to occur at nearly constant-volume conditions.
  3. Combustion products are over-expanded using a larger expansion volume than compression volume, as in the Atkinson Cycle.
  4. Cycle-skipping power modulation allows high efficiencies at low power settings while simultaneously cooling the engine’s walls internally and providing partial heat recovery.
  5. 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.