Key Parameters for Startability Improvement Applied to Ethanol Engines 2009-01-0616

It is well known that high ethanol content fuels have to face poor quality regarding startability in cold conditions on a spark ignited engine.

This paper will show test results when using E0, E85 and E100 fuels led on a single cylinder engine equipped with an active valve train research system. In order to improve engine behavior in severe thermal conditions, influence of several parameters was investigated. Injection strategies (timing, split injection, flow rate), valve train laws (delayed intake opening, valve lift…), ignition parameters (timing, multi-spark, strong energy coil…) as well as intake pressure were analyzed thanks to cylinder pressure analysis and specific test procedure. CFD investigations (influence of fuel, wall wetting) helped us to confirm some hypothesis on physical phenomenon. Those simulations were correlated with spray and wall film visualizations in the inlet port on an optical engine.

To conclude, it has been clearly shown that valve lift and valve timing optimization are the most efficient strategies as well as injection timing and low intake pressure to minimize start duration. Fruitful CFD results were also found on wall wetting process and underline some guidelines to optimize settings. This work provides a useful help to get efficient tuning on flex fuel engines.