Experimental measurements and numerical simulations were conducted to examine the effects of varying O-2 concentrations, oxidant velocity (V-o) levels, and bio-oil proportions on the combustion characteristics of the bio-oil/kerosene mixtures. The results indicated that when the O-2 concentration was 30% and the liquid fuel flow rate in the spray combustor was fixed, the flame associated with the spray combustion of pure kerosene decreased in length and increased in luminosity as V-o increased; moreover, the flame temperature increased. When V-o = 5.53 m/s, this phenomenon was more visible when the bio-oil was added to the kerosene. When the bio-oil proportion was 15% and V-o= 3.87 m/s, the flame luminosity increased; however, the flame luminosity decreased when V-o exceeded 3.87 m/s. When the O-2 concentration reached 40%, the length, luminosity, and temperature of the flame increased; nevertheless, when V-o = 5.53 m/s, the flame temperature decreased. The effect of the bio-oil proportion was not apparent. Because the bio-oil contained more volatile substances and O-2 than did the kerosene, the combustion efficiency of the bio-oil-fossil fuel mixtures varied according to the bio-oil proportion and O-2 concentration. (C) 2017 Elsevier Ltd. All rights reserved.