Experimental study of pyrolysis-combustion coupling in a regeneratively cooled combustor: System dynamics analysis

Scramjets are suitable for hypersonic flight, but their use requires the ability to ensure their thermal protection. In this context, a remotely controlled fuel-cooled combustor, suitable for the experimental analysis of the pyrolysis-combustion coupling characterizing a regeneratively cooled combustion chamber when a hydrocarbon propellant is used, has been designed. Similitude rules were used. Ethylene is used as fuel, air as oxidizer, with an equivalence ratio between 1.0 and 1.5 and a fuel injection pressure between 1 and 10 bar. Experiments are realized by varying operating conditions, to determine their impact on combustor heat transfer dynamics. Previous numerical results have been confirmed. A hysteresis effect has been demonstrated. It has been observed that system response time to fuel mass flow rate increases is lower (of about 40 to 50%) than system response time to fuel mass flow rate decreases and that a rise in equivalence ratio from 1.0 to 1.25 produces an increase in system response intensity that is, following the operating conditions, in the range from 90% to 170%. It has also been seen that an increase in equivalence ratio from 1.0 to 1.5 produces a raise of the temperature of the fuel-coolant (of about 40 to 50%), due to the increase in the emissivity of the flame.