Abstract
The European Commission has accepted the target of 10 per cent replacement of conventional fuels by alternative fuels (biofuels, CNG, hydrogen) in the road transportation sector by 2020. Natural gas is widely used in the refining industry of liquid transportation fuels. It is seen as a bridge to a future hydrogen-based economy. The natural gas-powered vehicle fleet is growing and reached 6.5 million in 2007. The average growth since 2000 has been 30 per cent.
Technology for light-duty CNG vehicles is well established, and CNG vehicles have performance comparable to their petrol-fuelled equivalents. CNG is commonly used in spark ignition engines because their powertrains are relatively easy to convert from liquid to gaseous fuels.
An analysis of CO, HC, NOx and CO2 emissions during testing on a chassis dynamometer, as well as performance, of a vehicle fuelled with petrol and CNG in turn are presented here. Analyses were performed on a vehicle with an SI engine equipped with an MPI feeding system operating in closed-loop control, a typical three-way-catalyst, and a heated oxygen sensor. The vehicle had been adapted by its manufacturer for fuelling with CNG by using additional special equipment mounted onto the existing petrol fuelling system. The vehicle tested featured a multipoint gas injection system (IV generation).
The tests subject to the analyses presented here were performed in the Engine Research Department of BOSMAL Automotive Research and Development Centre in Bielsko-Biala, Poland, within a research programme investigating the influence of alternative fuels on exhaust emissions from automotive vehicles with spark-ignition and compression-ignition engines.
Keywords: Alternative fuel, CNG, engine, exhaust emission, vehicle