Browse Publications Technical Papers 2019-26-0031

Coupled Dynamic Simulation of Two Stage Variable Compression Ratio (VCR) Connecting rod Using Virtual Dynamics 2019-26-0031

A variable compression ratio (VCR) could be one measure to reduce fuel consumption in highly boosted gasoline engine, as operating an engine with higher compression ratios at part load can improve fuel consumption and, hence CO2 emissions. FEV’s VCR solution is a two-stage system based on a variable length conrod with eccentric piston pin suspension. The small end of the conrod is equipped with an eccentric sleeve housing and wrist pin. By rotating the eccentric sleeve, the effective conrod length can switch between two positions, altering the distance between the piston head and the cylinder head and thus the compression ratio. To vary the conrod length, FEV uses the rotation of an eccentric bearing in the conrod small end and a two-cylinder system within the conrod along with a 3/2 way valve. All functional elements are concentrated into only one component, the conrod. The system is a combined hydraulic and mechanical system, fed by the engine oil supply from the main bearings. The system works without “external” energy supply. In order to analyze and optimize the system dynamics, FEV is using a highly sophisticated simulation approach based on coupled simulations of the mechanical and the hydraulic subsystem of the VCR conrod. The co-simulations are carried out in time domain using the commercial software FEV Virtual Engine for the elastic multi body simulations and GT Suite for the 1D fluid simulations. In this article the simulation methodology along with simulation results will be presented.


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