# Tribological Behavior of Biomass Fast Pyrolysis Fuel and Diesel Blends  
[PERSON]  
School of Mechanical Engineering, Hefei University of Technology, Hefei 230009, China; [EMAIL_ADDRESS] (H.Y.); [EMAIL_ADDRESS] (H.S.)  
Huiqiang Yu  
School of Mechanical Engineering, Hefei University of Technology, Hefei 230009, China; 1982800074@hfut.  
combustion engine. Therefore, the quality of the engine fuel lubricity has been a focus of many researchers.  
[PERSON] et al. [8] aimed to assess the effect of propyl gallate additive on the sustainability and lubrication behavior of B30 (30% biodiesel in diesel) blend on mild steel flat surface by using a high-frequency reciprocating rig. The tribological results indicated that propyl-gallate-doped B30 provided better lubricating performance than other tested additives for steel/steel contacts. The presence of propyl gallate caused the least weight loss (0.0003 g) with the least wear scar width (1.13 mm). The average coefficient of friction was also observed to be minimal for the propyl-gallate-doped B30 blend. The compounds formed on the mild steel surface when tested with propyl-gallate-doped B30 showed relatively less oxygen and high carbon content. The possible mechanism in enhancing lubricity of propyl-gallate-doped B30 blend could be attributed to the formation of relatively more stable and effective ester-based tribo-films at the contact surfaces.  
[PERSON] et al. [9] studied the fuel dilution rate of three lubricating oils (E0, E10, and B16) in a marine engine operating in on-water conditions with a start-and-stop cycle protocol. The level of fuel dilution increased with the number of cycles for all three fuels. The most dilution was observed with B16 fuel, and the least with E10 fuel. In all cases, fuel dilution substantially reduced the oil viscosity. The impacts of fuel dilution and the consequent viscosity reduction in the lubricating capability of the engine oil in terms of friction, wear, and scuffing prevention were evaluated by four different test protocols. Although the fuel dilution of the engine oil had minimal effect on friction because the test conditions were under the boundary lubrication regime, significant effects were observed on wear in many cases.  
[PERSON] et al. [10] aimed to examine the diesel engine's performance and emission of secondary fuels (SFs) comprising waste plastic oil (WPO) and palm oil biodiesel (POB), and to analyze their tribological properties. Five SFs (10-50% POB in WPO) were prepared by mechanical stirring. The results showed that the secondary fuels had great influence on the diesel engine's performance.  
In general, advanced alternative fuels provide an essential mechanism for reaching global aspirations of peak CO2 emissions and net-zero carbon, driving research and development. There are many opportunities for the development of sustainable fuels, but equally many challenges [11; 12]. It is important for the selection and application of biofuel in diesel, in which it is key data for the lubricity of biofuel and diesel blends. In the present study, the rice husk rapid pyrolysis fuel made by our research group was selected, and the biomass fuel was modified by a simple and practical emulsification method to improve the quality of biomass fuel. The lubrication characteristics of emulsified mixed oil (or emulsified biomass fuel) of biomass fuel and diesel with different ratios (5 wt.%, 10 wt.%, and 20 wt.%) were discussed, which was expected to provide basic data for the future application of the biomass fuel in engines.