Abstract
Bioethanol offers the potential of a more efficient, less polluting fuel but limitations in current engine platforms prevent it from being fully exploited. The EC funded project BEAUTY – Bio-Ethanol engine for Advanced Urban Transport by light commercial & heavy duty captive fleets – brought together automotive manufacturers, universities and research centers in a two-years project under the Sustainable Surface Transport program. The project was aimed at developing dedicated solutions (engines, combustion technologies and fuels). The project examined three different combustion approaches – stoichiometric SI engine for Heavy Duty applications, surface ignition Diesel engines for Light Duty applications and Controlled Auto-Ignition SI engines for Light Duty applications. In the spark ignited platform the project has developed and optimized the CAI (Controlled Autoignition) approach on the SI engine with the blends containing up to 85% bioethanol, getting a reduction in fuel consumption up to 10% at partial load. Experimental studies were performed on (SCRE) single cylinder research engine for SI (Spark Ignition) and CAI combustion modes with pure gasoline, E20 (20% of bioethanol by volume) and E85 (85% of bioethanol). The mixture preparation was performed with a SGDI (Spray Guided Direct Injection) technology. The exhaust valve system of the specific engine is hydraulically operated which allows to control the EGR composition in the combustion chamber. This approach is needed to control the auto-ignition process for CAI operation. The CAI mode in boosted engines shows slight improvement in comparison to SI engines which means that it is only reasonable to use CAI approach for naturally aspirated engine in which the combustion process is significantly improved in comparison to pure SI operation. Numerical simulations of the combustion process were performed with the use of the ECFM-3Z combustion model in AVL FIRE® code. The ECFM-3Z combustion model is equipped with data tables containing the ethanol laminar flame speed and auto-ignition delay time data for different pressure, temperature and equivalence ratio conditions. Results of simulations show good agreement with experimental data for SI and CAI processes.
Keywords: CAI, SI, ECFM-3Z, Gasoline, Ethanol