Performance and safety of transport vehicles fueled with alternative fuels in plateau environment: A review

Alternative fuels including natural gas, alcohols and biodiesel for transport vehicles have been applied worldwidely. However, the performance and safety of alternative fuel vehicles have changed when the application environment varies from plain condition to the plateau, resulting from the variation of air density and atmospheric pressure. Natural gas-fueled vehicles exhibited lower output and greater fuel consumption than gasoline-fueled vehicles in plateau environment. The oxygenated additives including alcohols and biodiesel can supply extra oxygen into the cylinder, which may benefit the engine performances compared with traditional petroleum in plateau environments. However, compared with plain environment, vehicles fueled with oxygenated fuels worsen the engine thermal efficiency, the power performance and the fuel economy in the plateau. With the increase of altitude, HC and CO emissions increase; whereas NO emissions show no evident change at various altitudes. Intake boosting, spark or injection timing optimization, and intake manifold optimization can effectively improve the combustion and performance of vehicles in the plateau. Safety is another significant factor for application of alternative fuels. Compared with plain environment, safeties of vehicles fueled with natural gas or biodiesel in the plateau have not been reduced, whereas safety of methanol and ethanol vehicles decrease, because they are easier to form air fuel mixture, have lower flash points, and have higher possibilities of gas resistance. The study proves that the performance and safety and alternative fuel vehicles deteriorate when the application locale varies from the plain region to the plateau region.