Dual fuel engine performance and emission characteristics using combination of natural gas and biodiesel blends

Abstract

Diesel dual fuel (DDF) engine is an alternative that has several potential advantages such as cleaner engine emission, fuel flexibility, more economical and better engine efficiency. Diesel and compressed natural gas (CNG) are commonly employed to operate the DDF engine. The substitution of diesel with biodiesel is believed to be able to achieve better emission results. Utilization of CNG and biodiesel in DDF engines can be considered as one of the optimum alternative solutions for fuel economy and can easily achieve auto ignition temperature. Several types of fuel namely, diesel, biodiesel, combination of diesel and natural gas as well as combination of biodiesel and natural gas were employed to compare their effects on the engine performance and emission. Six-cylinder 6.7L engines with auto-load connected to engine-dyno system were employed during the experimental tests. At maximum speed, results showed that increasing of biodiesel percentage in pilot fuel compound resulted in engine power reductions of approximately 132 hp compare to 139 hp recorded by industrial diesel fuel. Air to fuel ratio of industrial diesel and CNG recorded the highest result that was 3.94 at maximum speed compared to 20 % biodiesel blend and industrial diesel without CNG. Carbon dioxide, carbon monoxide and hydrocarbon emissions were reduced by 29 %, 35 % and 37 %, respectively at 2500 rpm and further reduced for engine operating without CNG. However, higher biodiesel blends in fuels had contributed in increasing of nitrogen oxide emission up to 321 ppm at maximum engine speed. Results recorded in this study proved that dual fuel engine provided significant advantages toward better engine performance and emission at maximum engine speed. The presence of biodiesel and CNG boosted the efficiencies of dual fuel engine system while providing cleaner fuels.