Low Pollution Characteristics of Urban Transit Buses Fueled with Liquefied Natural Gas

The advantages of liquefied natural gas as a fuel for urban transit buses are discussed. Urban transit buses powered by liquefied natural gas (LNG) are both feasible and practical as transportation systems for many metropolitan areas desiring cleaner air. The Rohr-Flxible LNG bus utilizes a four-cycle diesel engine that has been converted to spark ignition, natural gas operation. Analysis of gaseous exhaust emissions for the natural gas bus engine, plus its performance and noise characteristics, and installation details, are presented. Smoke and odor emissions are sensed as being negligible. This and other reported investigations on natural gas engine emissions, including the fact that the emitted hydrocarbons exhibit a low photochemical reactivity in polluted atmospheres, give heavy-duty LNG powered systems a clear advantage over diesel counterparts.