Principle of Conforming Water-Fuel Ratio for Metal Matrix Fuel Water-Ramjet Engine
When water-ramjet engine working, its water-fuel ratio is needed to conform. Taking magnesium-based fuel for example, thermodynamic parameter of different formulation fuel under different water-fuel ratio was calculated with the free energy minimization method. It was found that the effective specific impulse of water-ramjet engine increased first and then decreased with the increasing of water-fuel ratio, so there was the maximum value of it, named optimum specific impulse. The corresponding water-fuel ratio was the best one, and then the performance ability of water-ramjet engine was the maximum one. The temperature of nozzle exit gradually decreased with the increasing of water-fuel ratio. When the temperature was lower than local vaporization temperature, water steam coagulated and it would cause the thrust force to decline. Therefore, when the water-ramjet engine is designed, the value of water-fuel ratio can't exceed the best water-fuel ratio by the premise of guarantee of the temperature of nozzle exit as high as possible.
Daizhong Su, Qingbin Zhang and Shifan Zhu
Y. Gao et al., "Principle of Conforming Water-Fuel Ratio for Metal Matrix Fuel Water-Ramjet Engine", Key Engineering Materials, Vol. 450, pp. 474-477, 2011