Comprehensive Simulation Methodology for the 2-Step Variable Compression System – Dual Mode VCS^TM

Abstract

Achieving the future stringent CO₂ targets, especially in real driving conditions, requires new technologies to further optimize the internal-combustion-engine (ICE). Besides hybridization of the powertrain, the ICE itself needs to bring an improved brake-thermal-efficiency (BTE). Along with friction reduction measures, light weight design, thermal-management strategies a variable compression ration system can build a significant lever to reduce fuel consumption.

This paper depicts a comprehensive simulation methodology coupling the component dynamics with the hydraulic system to maintain proper switching during operation from long to short mode and vice versa. During development these models are regularly updated with measurement data gained from functional and single cylinder tests. The growing maturity of the simulation methods allow for a broad simulation-based frontloading to maintain the function of the system. In addition to that the structure is evaluated in terms of high-cycle-fatigue and damage according to the loads applied to the system from gas and mass forces. For multi-cylinder application the impacts on the oil system will be discussed to provide the proper boundary conditions for the 2-step switching, not compromising fuel consumption benefits.