A quasi-dimensional three-zone model for performance and combustion noise evaluation of a twin-spark high-EGR engine

The paper reports the research activity related to the development of a twin-spark SI engine equipped with a variable valve timing (VVT) device. Improvements on the fuel consumption at part load are expected when a high internal exhaust gas recirculation (internal EGR) level is realized with a proper phasing of the VVT device. The twin-spark solution is implemented to improve the burning speed at low load, and to increase the EGR tolerance levels. Both experimental and theoretical analyses are carried out to investigate the real advantages of the proposed engine architecture. In particular an original quasi-dimensional model for the simulation of the burning process in a twin-spark engine is presented. The model is mainly utilized to find the proper combination of VVT device position (and hence EGR level) and spark advance for different engine operating conditions. A comparison with the single-spark solution is also provided. In addition, a procedure for the estimation of the sound pressure levels originated from the combustion process is utilized, to estimate the increased radiated noise associated to the double ignition. The model is well suited to define the control strategy maps of the engine in its whole operating range.