Abstract:

A turbocharged spark-ignition engine with port fuel injection (PFI) was developed suing compressed natural gas (CNG) based on a secondary development for a downsizing gasoline engine to reduce both vehicle tailpipe CO2 emissions and other exhaust gas emissions without compromising driving performance. This paper quantified the advantage of fuel performance characteristics of the downsized CNG engine with reduced knock sensitivity, optimized compression ratio, and improved combustion efficiency. While peak cylinder pressure was controlled below 12 MPa, peak torque 180 Nm, same level as gasoline variant, was realized from 3 000 r/min. With adapted compression ratio for CNG operation, effective combustion efficiency is over 38%, which is even higher than turbocharged gasoline direct injection (TGDI) version. Therefore, compared to gasoline application, operation with CNG will lead to 24.2% of CO2 emission reduction as well as 46.4% of mileage-specific fuel cost saving.

Key words: spark-ignition engine, port fuel injection (PFI), compressed natural gas (CNG), turbo-charger, thermal efficiency, CO2 emission reduction