A Mild Hybrid SIDI Turbo Passenger Car Engine with Rankine Waste Heat Recovery
In the strive for more fuel-efficient vehicles all possible measures are considered to increase the efficiency of the combustion engine. 48V mild hybrid technology is one such measure; SIDI (Spark Ignited Direct Injection) engines with Miller technology another, while recovering energy from the engine waste heat (WHR) is yet an option to increase fuel conversion efficiency. Here, for the first time, we will publish the results from an advanced engineering project at Volvo Cars including all these components. We have successfully built an ethanol based Rankine system around a 4-cylinder, 2.0 litre SIDI-engine, including 48V mild hybrid technology. The Rankine system uses the engine exhaust as heat source, while the expansion of the ethanol steam occurs in an axial piston expander coupled both electrically to the hybrid system and mechanically to the engine crankshaft.