Performance study of a continuously-variable stroke internal combusion engine

The performance of a continuously-variable stroke internal combustion engine was simulated with a computer model. The engine has a mechanism which provides a different stroke length for each of the four strokes in the engine cycle. Specifically, the variable-stroke engine has a smaller clearance volume at the start of the intake stroke than at the end of the compression stroke, and the expansion stroke is lengthened to get more work from the combustion products.

A conventional engine was also modeled to provide a reference for comparison of the computer results. The models include subroutines for calculation of piston movement, intake and exhaust mass flow, combustion, heat transfer, friction, and shaft power.

The program results indicated that the variable-stroke engine yields a 12% gain in output horsepower. The gain is attributed to the engine's higher volumetric efficiency.