Spray and combustion characteristics of F-T diesel blending oxygenated fuel based on constant volume combustion chamber

In this work, 20% of polymethoxy dimethyl ether (PODE) and n-butanol are blended with F-T diesel by volume, respectively, referred to as FP20 and FBU20. Based on the constant volume combustion chamber (CVCC), the spray characteristics and combustion characteristics of diesel, F-T diesel, FP20 and FBU20 under high ambient temperature and pressure are studied by using high-speed photography combined with Matlab image processing technology. Results show that the steady-state liquid spray tip penetration and spray projection area of FP20 and FBU20 are smaller than those of F-T diesel due to their good evaporation. Combustion characteristics studies show that compared to D100, the ignition delay and flame lift-off length of FT100 decrease by 22.9% and 43.6%, respectively. Compared to FT100, the flame lift-off length of FP20 and FBU20 increases by 36.8% and 44.1%, respectively. Due to the addition of high cetane number and high oxygen content PODE, the ignition delay of FP20 is shortened by 3.7%, and the ignition delay of FBU20 is prolonged by 40.1% due to the effect of high latent heat of vaporization and low cetane number of n-butanol. Compared to D100, the peak flame area of FT100 increases by 8.5%, while the peak flame luminosity decreases by 18.2%. Because PODE and n-butanol can improve evaporation and increase the oxygen content of fuel and then reduce the formation of soot, compared to FT100, the peak of flame area and flame luminosity of FP20 and FBU20 are decreased. The results of two-color method show that after adding PODE and n-butanol into F-T diesel fuel, the generation of soot and combustion temperature of the mixed fuel are reduced. Moreover, FP20 has higher oxygen content and better atomization characteristics, so the effect of reducing soot is better than that of FBU20.