Loss Analysis of a HD-PPC Engine with Two-Stage Turbocharging Operating in the European Stationary Cycle

摘要

Partially Premixed Combustion (PPC) has demonstrated substantially higher efficiency compared to conventional diesel combustion (CDC) and gasoline engines (SI). By combining experiments and modeling the presented work investigates the underlying reasons for the improved efficiency, and quantifies the loss terms. The results indicate that it is possible to operate a HD-PPC engine with a production two-stage boost system over the European Stationary Cycle while likely meeting Euro VI and US10 emissions with a peak brake efficiency above 48%. A majority of the ESC can be operated with brake efficiency above 44%. The loss analysis reveals that low in-cylinder heat transfer losses are the most important reason for the high efficiencies of PPC. In-cylinder heat losses are basically halved in PPC compared to CDC, as a consequence of substantially reduced combustion temperature gradients, especially close to the combustion chamber walls. Pumping losses are on the other hand three times higher than for CDC due to the increased mass flow rate over the valves from the charge dilution and the high amounts of EGR. Friction losses remain uncertain with respect to the direct injection of gasoline instead of diesel, but have been estimated to be slightly higher than for CDC in this work. A sensitivity analysis demonstrates that further reductions of in-cylinder heat transfer losses are possibly the most beneficial for further increases in brake efficiency. Further improvements can also be reached by reducing exhaust port and manifold heat transfer losses and optimized gas exchange and boosting systems. A PPC engine with 57% gross indicated efficiency is likely to reach more than 50% brake efficiency.