Coupled Dynamic Simulation of Two Stage Variable Compression Ratio (VCR) Connecting Rod Using Virtual Dynamics

Abstract

<div class="section abstract"><div class="htmlview paragraph">The fuel consumption of combustion engines requires continuous reduction to meet future CO2 fleet targets. The progression of emission legislations shifted the focus on PN and NOX emissions in real world driving scenarios (RDE). Recently, the monitoring of CO emissions puts high load fuel enrichment for component protection into focus and a ban on enrichment is widely expected. Hence, gasoline engine technologies, which enable Lambda 1 operation in the entire engine map are specifically promoted. Variable Compression Ratio (VCR) attacks all these topics already at the combustion process. In addition to the well-known CO2 capability, VCR also enables enlargement of the lambda 1 operation in gasoline engines as well as reduced NOX emissions in diesel engines. The basic principle of developed VCR solution is to change the effective length of the connecting rod (and thereby the compression ratio) in two stages by several millimeters. Basically, the VCR connecting rod consists of a mechanical and hydraulic system which is fed with oil by the connecting rod bearing. All functional elements to realize the variability such as an eccentric, lever, support rods, check valves and shift valve are integrated into the connecting rod. The system works without “external” energy supply but uses mass- and gas forces - acting on the piston pin - to vary its length. In order to analyze and optimize the system dynamics, a highly sophisticated simulation approach based on coupled simulations of the mechanical and the hydraulic subsystem of the VCR connecting rod. The co-simulation is carried out in time domain using the commercial software Virtual Dynamics for the elastic multi body simulations and GT-Suite for 1D fluid simulations. In this article the coupled 3D-multi body simulation/1D-hydraulic co-simulation as used to optimize the VCR connecting rod performance are presented.</div></div>

Experimental analysis of the system behavior of a two-stage variable compression ratio (VCR) system in fired SI-engine operation

“…Important for any design improvement is a coupled simulation of the mechanical and the hydraulic subsystems. [22][23][24] So far, the validation process of this models has been based primarily on off-engine test results, for example, from component tests or the Advanced Functional Pulse Test (AFPT). 25,26 Special influences resulting from the fired engine operation therefore could not be sufficiently considered in the development process, so that the engine testing is indispensable for a consistent validation process of the existing simulation approaches.…”

Study on the Dynamic Characteristics of a Hydraulic Continuous Variable Compression Ratio System

“…, p L < 0.25 and the left globe valve opened 0, p L > 0.25 or the left globe valve closed (10) where A cd is the effective flow area of the check valve and ρ is the density of the hydraulic medium. System flow balance equation: According to the working principle of VCR, the system flow balance equation can be divided into two cases.…”