Operating range in a Multi Cylinder HCCI engine using Variable Compression Ratio 2003-01-1829
Homogenous Charge Compression Ignition (HCCI) is a promising part load combustion concept for future power train applications. Different approaches to achieve and control HCCI combustion are today investigated and compared, especially concerning operating range. The HCCI operating range for vehicle applications should at least cover contemporary emissions drive cycles.
The operating range in terms of speed and load is investigated with a Naturally Aspirated (NA) four-stroke multi-cylinder engine with Port Fuel Injection (PFI). HCCI combustion control is achieved with Variable Compression Ratio (VCR) and inlet air preheating with exhaust heat. Both primary reference fuels and commercial gasoline are used in the tests.
HCCI combustion with commercial gasoline is achieved over a load range from 0 to 3.6bar BMEP, and over a speed range from 1000 to 5000rpm. Maximum load is at 1000rpm and decreases with an approximately straight slope to zero at 5000rpm. NOx emissions are kept below 15ppm and the rate of pressure rise below 6bar/CAD throughout the operating range. Combustion efficiency is above 90% for all positive loads. High amounts of unburned HC as well as CO emissions decrease combustion efficiency to 70% at zero load. Brake efficiencies up to 33% are obtained.