This study presents a novel crank mechanism which enables easy and fast compression ratio adjustment. The novel crank mechanism and piston travel are explained and highlighted. The basic idea is that eccentric gear is installed on a crankshaft web. Eccentric gear is fitted to the big end of the connection rod and eccentricity is controlled by rotating the control gear a discrete amount. Thus the position of eccentricity is varied and controls an effective stroke length. The compression ratio is adjusted to best fit current load demand, either optimizing fuel efficiency or engine power and torque. Adjustments are individual to each cylinder. The system is capable of adjusting from min to max within 10 milliseconds [ms]. Emphasis is on reduction of CO2 emissions and reducing fuel consumption, especially at part load condition.
The governing mechanical equations are presented. This novel crank mechanism has two new governing design parameters: Eccentricity and the angle of eccentricity when the cam angle is 0°. In our demonstration unit, the gear ratio between the eccentric gear and control gear is set to 1.5. This will make the induction-compression cycle different from the expansion-exhaust cycle. This gives a greater degree of freedom to design the engine performance.
The governing mechanical equations are presented. This novel crank mechanism has two new governing design parameters: Eccentricity and the angle of eccentricity when the cam angle is 0°. In our demonstration unit, the gear ratio between the eccentric gear and control gear is set to 1.5. This will make the induction-compression cycle different from the expansion-exhaust cycle. This gives a greater degree of freedom to design the engine performance.
The first full-scale engine demonstration test runs were made at Oulu University engine laboratory. The demonstration version was modified from an existing commercial (Honda R18A2) SI engine.
In addition to reduction of CO2 emissions, the engine is adjustable for different fuels, making the most out of fuel consumption.