Consider an ideal ramjet engine flying at an altitude of 10,000 m (see local atmospheric conditions in appendix III of the textbook). The jet fuel used has a heat of combustion of 43,000 kJ/kg, and a stoichiometric fuel to air ratio of0.06. The maximum temperature of the ramjet is 2600 K. Assume the specific heat ratio up to the combustion chamber is 1.4, and that the specific heat ratio through the rest of the engine (including the combustor) is 1.33. The specific heat at constant pressure for the gases in the combustor can be calculated using the following equation:
Cp= (y/y-1)R where R is assumed to be 0.287 kJ/kgK throughout the engine. Calculate the specific thrust and TSFC as a function of flight Mach number from a range of 1 to 6. Note that the fuel to air ratio can not be above the stoichiometric value (i. e. we can't burn more fuel than that at an equivalence ratio of unity). Some operating points may require a higher value of f than the stoichiometric value to reach the temperature limit. Under this condition, f should be set to the stoichiometric value, and the combustor exit temperature To4 should be calculated from the energy equation. Otherwise, the maximum temperature is used and f is calculated from the energy equation.