Thermodynamic Cycles of Internal Combustion Engines for Increased Thermal Efficiency, Constant-Volume Combustion, Variable Compression Ratio, and Cold Start 2007-01-4115

An internal-combustion engine platform that may operate on a portfolio of cycles for increased engine expansion ratio, combustion under constant volume, variable compression ratio, and cold start is introduced. Through unique thermodynamic cycles, the engine may be able to operate on a much greater expansion ratio than the compression ratio for a significantly improved thermal efficiency. This improvement is attained without involving a complex mechanical structure or an enlarged engine size, and at the same time without reducing the compression ratio. The engine with these features may serve as an alternative to the Atkinson cycle engine or the Miller cycle engine. Additionally, based on the same engine platform, the engine may operate on other cycles according to the load conditions and environmental considerations. These cycles include those for combustion under constant volume, variable compression ratio under part load conditions, and cold start for alternative fuels.

It is believed that the introduced thermodynamic cycles associated with the engine platform may enable a future internal combustion engine that could generally increase the thermal efficiency by about 20% under full and part load conditions and overcome the cold start problem associated with diesel fuels or alternative fuels such as ethanol and methanol.