09 AVL Lean Burn Systems CCBR and CBR Light for Fuel Economy and Emission Optimization on 4-Stroke Engines 2002-32-1778

The CBR [1] (Controlled Burn Rate) is a port deactivation concept developed by AVL and is already applied in series production cars. The benefit of this concept is the low engine-out emission (CO, HC and NOx) and good fuel economy. By creating turbulent kinetic energy at the correct time and place in the combustion chamber a rapid and stable combustion occurs which allows to run the engine well above a Lambda Excess Air Ratio of 1.5. The CBR system features two different intake ports, one charge motion port and one filling port. Additionally a device for port-deactivation (slider, butterfly) is applied. At part load points and lower engine speeds the filling port is switched off.

The CBR concept was now evoluted for compact engines as CCBR - with carburetor and as CBR Light - for engines with electronic fuel injection.

CCBR stands for Carbureted Controlled Burn Rate. The advantages in comparison to conventional port designs are a remarkable fuel consumption improvement compared to standard Carbureted engines and reduction of HC, CO and NOx emissions along with very little add-on cost. For low output engines the emission standard of Euro II can be achieved without any exhaust aftertreatment. Also Euro III standard shall be realizable by additional secondary air and oxidation catalyst application.

For fuel injected engines CBR-Light has been developed, a Lean Burn System with electronic fuel injection and if required Air/Fuel sensor and closed loop control.

The system CBR-Light can whether be operated as a lean burn system - aspirating air and fuel only with even better benefits than CCBR, but can also be operated at a stoichiometric Air/Fuel ratio with a Three-Way Catalyst and additional EGR (Exhaust Gas Re-circulation) of up to 25% (w/o residual gas) thus reducing the NOx emission and improving the fuel economy.

The development steps are described in the paper and the results from the CFD simulation up to the combustion and the “Visio Tomo” (Tomographic Combustion Analysis) results are depicted.