SPRAY & LIQUID LENGTH CHARACTERISTICS OF TETRADECANE AS A SURROGATE IN COMPARISON TO JP-8

Extensive studies have been completed for diesel engine high pressure injection on spray and combustion characteristics with diesel fuel. However the US military’s objective is to use JP-8 as a replacement to diesel fuel, which has limited spray and combustion information available. The differences between JP-8 and diesel in terms of fuel properties translate to differing spray and combustion characteristics. To fulfill the Single-Fuel Concept of the military and incorporate JP-8 fuels, knowledge of the fuels spray, vaporization, and combustion behavior is imperative for determining fuel impact on performance. This work quantifies vaporizing spray characteristics of vapor penetration and vaporizing liquid length using high speed imaging methods of combined Mie-scatter and Schlieren in a constant volume combustion vessel. Studies are undertaken at a constant injection pressure of 700 bar, at temperatures of 800, 946, and 1150 K at a density of 24.1 kg/m³. Tetradecane is used as a vaporizing single component surrogate for JP-8, with results compared to spray characteristics of JP-8 and diesel available in the literature. Tetradecane is chosen as a surrogate since prior experimental work using heptamethylonone (HMN) as a surrogate showed HMN does not match JP-8 liquid length trends, especially at low density conditions. Although the boiling point of HMN (240°C) matches the 90% distillation point of JP-8, a higher boiling point fuel (tetradecane at 252°C) may provide a better match to vaporization characteristics of JP-8. Results from this study provide an understanding of spray and vaporization characteristics of tetradecane as a surrogate for JP-8.