Spray and engine performance of cerium oxide nanopowder and carbon nanotubes modified alternative fuel

Abstract

This work aims to experimentally investigate and demonstrate the impacts of using Cerium Oxide (CeO2) and multi-wall carbon nanotube (CNT) blended with the alternative fuel, which is gas-to-liquid fuel (GTL) in this study, compared to diesel fuel (DF) on engine performance and study the macroscopic spray characteristics through a Constant Volume Vessel (CVV). Results demonstrate Cerium Oxide nanopowder and carbon nanotubes have very limited impacts on the average cone angle of gas-to-liquid fuel and diesel fuel. Cerium Oxide nanopowder and carbon nanotubes can individually reduce spray penetration during injection under a small ambient pressure when blended with diesel fuel, whilst the effect on gas-to-liquid fuel is less significant because the smaller density and lighter compositions of gas-to-liquid fuel promote its breakup process. In the post-injection period, carbon nanotubes increases the spray penetration of gas-to-liquid fuel, because gas-to-liquid fuel molecules are smaller than diesel fuel. Consequently, more gas-to-liquid fuel molecules stay inside the carbon nanotubes, which can only evaporate through two ends, and thus results in an overall reduced evaporation rate. Moreover, experiments also demonstrate that the average cone angle is independent of rail pressure, but it can be reduced by decreasing ambient pressure and increasing ambient temperature. During injection, both ambient pressure and rail pressure can influence the spray penetration, whilst after the end of injection, only ambient temperature has an effect on it. The engine experiment indicates that Cerium Oxide nanopowder can reduce nitrogen oxides, unburnt hydrocarbons and particulate number emissions simultaneously for both diesel fuel and gas-to-liquid fuel due to its catalysis at high-temperature conditions, whilst carbon nanotubes has a weaker effect on reducing nitrogen oxides and particulate number for gas-to-liquid fuel than diesel fuel.