The second edition of MANmagazine, published by MAN Corporate Communications for MAN Truck and Bus, has a feature on fuel technology developments for buses. In it, Herbert Knorr of MAN’s Alternative Fuels research department discusses possibilities for natural gas in future combustion engines.Building on an accumulation of 40 years experience with gas drives, Herbert Knorr’s development team in Nuremberg put a compressed natural gas (CNG) powered 310-hp turbo engine in a Euro 6 version for municipal buses on the road. The MAN Lion’s City CNG bus is offered with a six-cylinder engine with 200 kW (272 HP) and 228 kW (310 HP). In some cases, emission performance is said to be significantly better than what is required by the stringent Euro 6 regulations.
The increasingly widespread network of natural gas fueling stations has alleviated fuel supply anxiety, enabling municipal bus companies to turn to natural gas engines as an environmentally friendly, economical and sustainable alternative for transportation. Recently metro fleets in Paris and Bordeaux purchased the Euro 6 CNG buses.
According to the article entitled Power Performance, Korr says MAN is committed to exploring the potential for reduced fuel consumption using natural gas engines. As an example he mentions recycling the cooled exhaust which could make the mixture of natural gas, air and waste gas considerably more knock-proof and therefore more economical.
Korr’s team is also exploring direct injection fuel technology, whereby a small amount of diesel is injected with natural gas directly into the combustion chamber under high pressure, producing spark-free ignition. “Due to the high compression ratio, this method could achieve fuel consumption similar to that of a diesel engine,” predicts Knorr.