At the Aachen Colloquium next week, Ricardo and Geely will present research work into the application of the Ricardo Magma xEV gasoline engine concept into a commercial vehicle series hybrid powertrain, delivering 45% brake thermal efficiency.
The Ricardo Magma concept was developed as a deep Miller cycle engine (earlier post) delivering fuel efficiency benefits while maintaining full-load specific performance.
The basic architecture of the Magma concept was a boosted four-stroke gasoline engine with four valves per cylinder. The Magma concept architecture closes the inlet valve early to reduce pumping losses. A long exhaust stroke then extracts maximum efficiency.
The concept placed particular demands on the boosting system. Early closure of the inlet valves leaves a smaller window for the charge fill the cylinder. Magma, which uses a mechanical supercharger and a turbocharger as well as two stages of intercooling to ensure the charge air is as cold and dense as possible as it enters the cylinder, runs on higher boost pressures than have been the norm.
Magma xEV is an extension of these principles to hybrid vehicles, to take advantage of the new flexibilities offered by such applications.
This engine concept is particularly attractive for series-hybrid and range-extender powertrain applications, in which the driver experiences an EV style of driving with tractive effort provided through an electric motor. As the combustion engine acts as an electrical generator, it can be optimized to a significantly higher level of efficiency.
In the paper co-authored with Geely, Ricardo engineers describe the processes of simulation-led development and physical testing of a single cylinder prototype. The Magma xEV concept described in the paper uses homogenous lean-burn combustion with knock mitigation assessed through approaches including both direct and port water injection.
The results of this research have demonstrated the capability of the Magma xEV to achieve a brake thermal efficiency of 45% in this application, offering the potential of significant fuel economy improvements over and above those of a conventional gasoline engine used in such a series hybrid powertrain.
Alongside this high efficiency hybrid powertrain research with Geely, Ricardo will also be highlighting a range of new concepts and technologies including its recently unveiled high efficiency scalable electric drive unit (EDU); battery pack and management system developments; and its virtual reality engineering review app, which enables collaborative simultaneous engineering design reviews to be carried out by multiple users in different geographical locations.