Effect of a novel mechanical CWL system on economic performance of a turbocharged spark-ignition engine fuelled with gasoline and ethanol blend

摘要

In order to improve the fuel economic performance of the gasoline engine, a novel mechanical continuously variable valve lift (CVVL) system with self-regulation of the valve timing (CVVLT) is proposed. The bench tests are conducted on the original and prototype engines with the ethanol blend fuel. Then, a simulation model is developed to evaluate the benefits of the proposed CVVLT system. Moreover, theoretical analysis of intake pumping losses in two engines is carried out, and the comparison between the CVVLT engine and original engine is performed in this regard. According to tested dates, it is found that on the one hand, compared with the original engine, the PMEP of the CVVLT engine at 1500 r/min, 2000 r/min and 3000 r/min are decreased by 23%, 25% and 22%, respectively. On the other hand, the improvements in the fuel economy at 2000 r/min and 3000 r/min reach 14% and 11%, respectively at low to medium load conditions. Although the EVVLT system slightly lengthens the combustion process at low loads, it greatly improves the gross mechanical efficiency and thus improves the effective thermal efficiency. Simulation results show that the retarded intake valve opening timing positively affects the combustion quality and the optimized valve opening timing can reduce the fuel consumption up to 1%-2%. The results demonstrate the proposed CVVLT system has a high potential for improving the economic performance of conventional spark-ignition engines in the low to medium load conditions.