Experimental investigation of the impact of biodiesel on the combustion and emission characteristics of a heavy duty diesel engine at various altitudes

As a widely recommended alternative fuel for diesel engines, biodiesel has been proven to be useful for the reduction of emissions from diesel engines, especially particle emissions. Equipped with an on-board engine test bench and a portable emission measurement system designed for mobile tests, this work investigated the emission of a Euro III emission standard heavy-duty diesel engine fueled with petroleum diesel and soybean-oil biodiesel at four different altitudes. Combustion data were also collected during the emission test at each altitude, which was helpful for the analysis of the emission results. These results showed that the use of biodiesel at high altitude advanced the start of ignition and reduced the proportion of the premixed combustion stage. The PM (particulate matter), THC (total hydrocarbon) and CO (carbon monoxide) emissions of the engine fueled with biodiesel were reduced at each investigated altitude, but the reduction of PM and THC emissions caused by biodiesel decreased as the altitude increased. The NO_X (nitrogen oxides) emission of both fuels showed no obvious variation with altitude, and the use of biodiesel led to a slight reduction in NO_X emission.