Comparison of fuel economies of high efficiency diesel and hydrogen engines powering a compact car with a flywheel based kinetic energy recovery systems

Coupling of small turbocharged high efficiency diesel engines with flywheel based kinetic energy recovery systems is the best option now available to reduce fuel energy usage and reduce green house gas (GHG) emissions. The paper describes engine and vehicle models to generate engine brake specific fuel consumption maps and compute vehicle fuel economies over driving cycles, and applies these models to evaluate the benefits of a H2ICEs developed with the direct injection jet ignition engine concept to further reduce the fuel energy usage of a compact car equipped with a with a flywheel based kinetic energy recovery systems. The car equipped with a 1.2 L TDI Diesel engine and KERS consumes 25 g/km of fuel producing 79.2 g/km of CO2 using 1.09 MJ/km of fuel energy. These CO2 and fuel energy values are more than 10% better than those of today's best hybrid electric vehicle. The car equipped with a 1.6 L DI-JI H2ICE engine consumes 8.3 g/km of fuel, corresponding to only 0.99 MJ/km of fuel energy.