Enhancing the stability and combustion of a nanofluid fuel with polydopamine-coated aluminum nanoparticles

In this experimental study, we examine the stability and combustion of a new nanofluid fuel created by mixing kerosene and nano-aluminum (n-Al) particles coated with polydopamine (PDA). Focus is placed on examining the effect of the PDA coating time, and hence the PDA film thickness, with the aid of a proposed heat transfer mechanism for the combustion of n-Al@PDA/kerosene droplets. The results indicate that n-Al@PDA(1 h)/kerosene (i.e. a PDA coating time of one hour), which remains stable for seven hours, exhibits better stability than all the other samples, but that the stability worsens as the PDA coating time increases. The ignition character of n-Al/kerosene nanofluid droplets is not quite sensitive to PDA layer. The combustion processes of n-Al/kerosene and n-Al@PDA/kerosene are remarkably similar, consisting of four distinct stages: ignition, classic combustion, vapor flame extinguishing, and Al droplet combustion. The burning intensity of n-Al agglomerates coated with PDA is stronger than that without PDA, with more black smoke generated and more n-Al particles expelled near the end of the n-Al burning stage. The combustion rates of kerosene droplets containing 5% n-Al@PDA(1 h) and 5% n-Al@PDA(2 h) are higher than other samples. The intensity of the emission spectra for the n-Al@PDA(2 h) agglomerates is the highest among all the samples. Taken together, these results indicate that, compared with uncoated n-Al/kerosene and other PDA-coated nanofluid fuels, n-Al@PDA(2 h)/kerosene exhibits superior ignition and combustion characteristics, opening new possibilities for tailoring Al-based nanofluid fuels.