Transient Control of Thermal and EGR Systems for Third Generation GDCI Multi-Cylinder Engine 2018-01-0902
A third generation Gasoline Direct Injection Compression Ignition (GDCI) engine has been designed and built. The engine is intended to meet stringent US Tier 3 emissions standards with diesel-like fuel efficiency. While nearly every aspect of the engine design has been improved over the previous second generation engine, this paper is primarily concerned with two of the most critical subsystems - the thermal management and EGR systems. These are especially important because gasoline compression ignition combustion is sensitive to intake gas temperature and exhaust gas dilution. Both parameters may deviate from steady state targets during transients.
The quality of combustion control during transient vehicle operation is limited by significant response delay in both the thermal management and EGR systems. The intake air coolers must be sized for sufficient heat transfer capacity under peak load operating conditions, which results in coolers having significant thermal inertia. The low-pressure EGR and air intake systems necessarily have a finite volume with significant gas transport delays. These systems have been redesigned to minimize these transport delays. A control system with new algorithms, EGR estimator, and fast response sensors have been developed to optimize both the speed and accuracy of control.
This paper describes the design features of the engine and controller. The system design has been guided by extensive use of transient co-simulation and modeling for which results are presented.