On the optimal choice of operating points in large series hybrids

This paper investigates some fundamental relationships for the optimal choice of operating points of ICEs in large series hybrids. It approaches the fuel minimization problem under the assumption that the engine cannot be switched off. The analysis focuses on the two operating point case with linear and quadratic break specific fuel consumption (bsfc) dependencies. Generalizations of these results to nonlinear (and non-quadratic) dependencies will be performed using a bounding argument. Explicit fuel saving conditions are given for the linear case and the amount of fuel savings will be quantified.