Light-Duty Single And Multi-Shaft Boosting And Compounding Studies With In-Cylinder Insulation

A set of two-cylinder engine concepts utilizing a supercharger and piston- or turbine-compounding were compared to a turbocharged engine modeled with a consistent methodology developed in previous works. In-cylinder insulation was added to each of the engines to evaluate the effects on performance. The goals of this simulation were to utilize energy that otherwise would be bypassed around the turbine side of a turbocharger and redirect it to the crankshaft, as well as to redirect energy that would previously have entered the coolant into the exhaust gases where it could be reclaimed by a second expansion process. Gains in performance and efficiency were thoroughly analyzed to provide insight into the magnitudes and mechanisms responsible. It was found that the second expansion process from exhaust-compounding was able to significantly improve engine performance at moderate to high loads, as well as compensate for the loss in volumetric efficiency that accompanies in-cylinder insulation. The piston-compounded single-shaft DCDE was able to outperform the turbocharged multi-shaft DCDE at mid to high loads, and in maximum brake power due to the low losses in the coupled nature of the second expansion, while the turbine-compounded engine suffers higher losses due to the turbomachinery mismatch with the positive displacement power cylinders.