Preliminary Study On Deposition Of Thermal Oxidation And Thermal Cracking Of Hydrocarbon Fuel

Simulating engine system in the hypersonic aircraft, a set of continuous flow reactor was set up to evaluate coke formation from thermal cracking of endothemic fuel in supercritical conditions. Methods were also set up to determine coke amount and depositing rate. Suitable reacting conditions were confirmed by a set of tests. With n-dodecane, RP-3 and surrogate JP-7, thermal cracking experiments were carried on in 304 stainless steel tube. Analyzing curves of coke amount and depositing rate, deposition character of each fuel and three global kinetics equations were got.Thermal oxidation deposition of n-dodecane and RP-3 was invertigated. The thermal oxidation deposition of n-dodecane and RP-3 increase slowly when temperature rises, and reach the maximum when dissolving oxygen (exposed in air about 70ppm) was exhaisted. Then it reduces gradually with increase of temperature, and becomes stable at a value in the transition region. The apparent activation energy of RP-3 is 80.15kJ/mol and it is higher than that of n-dodecane 36.91kJ/mol, indicating a better performance of RP-3 in thermal stability.There are two kinds of deposition formed in supercritical thermal cracing: amorphous carbon and filamentous carbon. Filamentous carbon formed by the metal catalysis is the main source of the deposition in the thermal cracking regime. By the annlysis of total deposition, apparent activation energy of n-dodecane, RP-3 and surrogate JP-7 were 260kJ/mol, 285kJ/mol and 399kJ/mol, demonstrating an order of the thermal stabily from high to low: surrogate JP-7, RP-3, n-dodecane. The apparent activation energys obtained by the similar analysis in filamentous carbon deposition are 371 kJ/mol, 402 kJ/mol and 550 kJ/mol. Comparison of the two sets of apparent activation energies shows that filamentous carbon was formed at a higher temperature.