Effects of Pyrolysis Bio-Oils on Fuel Atomisation—A Review

Bio-oils produced by biomass pyrolysis are substantially different from those produced by petroleum-based fuels and biodiesel. However, they could serve as valuable alternatives to fossil fuels to achieve carbon neutral future. The literature review indicates that the current use of bio-oils in gas turbines and compression-ignition (diesel) engines is limited due to problems associated with atomisation and combustion. The review also identifies the progress made in pyrolysis bio-oil spray combustion via standardisation of fuel properties, optimising atomisation and combustion, and understanding long-term reliability of engines. The key strategies that need to be adapted to efficiently atomise and combust bio-oils include, efficient atomisation techniques such as twin fluid atomisation, pressure atomisation and more advanced and novel effervescent atomisation, fuel and air preheating, flame stabilization using swrilers, and filtering the solid content from the pyrolysis oils. Once these strategies are implemented, bio-oils can enhance combustion efficiency and reduce greenhouse gas (GHG) emission. Overall, this study clearly indicates that pyrolysis bio-oils have the ability to substitute fossil fuels, but fuel injection problems need to be tackled in order to insure proper atomisation and combustion of the fuel.