Performance Study of a Multifuel Engine Operating Simultaneously with CNG and Ethanol in Various Proportions

The technological development of automotive engines is focused on alternative energy sources and optimized use of conventional fuels. The current flexible engines in Brazil can operate with gasohol and ethanol blends in any proportion, but the flexibility is restricted to liquid fuels. The present investigation consists on the use of electronic injection systems for ethanol and for CNG, allowing the use of these fuels simultaneously. The objective of this work is to determine the best proportion of CNG-ethanol mixture in order to maximize the use of the natural gas, fuel which offers the lowest BSFC on conventional SI engines. The low volumetric efficiency inherent in the use of CNG is compensated by the injection of a small quantity of ethanol. The latent heat of vaporization of the alcohol is used to take heat from the intake air and increase its mass, taking advantage from the high latent heat of vaporization of the ethanol and the low BSFC of the CNG. The present investigation is a pioneer study concerning the simultaneous use of CNG and ethanol and is a breakthrough in the development of new management strategies on a flexible engine. The ethanol-CNG mixture proportion and the stoichiometry could be set according to the torque demand but always giving priority to the CNG, with results on low BSFC (compared to the exclusive use of ethanol).