Experimental proof of Zel'dovich cycle efficiency gain over cycle with constant pressure combustion for hydrogen–oxygen fuel mixture

• We conduct experiments with two prototypes of hydrogen–oxygen rocket engine operating in detonation and combustion modes.
• We vary mass flow rates of fuel components and measure engine thrust to obtain the specific impulse.
• Specific impulse of engines operating in detonation mode was proved to be 6–8% higher than in combustion mode.

The objective of work outlined in this paper was to prove experimentally the energy efficiency of Zel'dovich thermodynamic cycle (cycle with detonative combustion of fuel) by direct comparison of thrust performances of liquid-propellant rocket engine (LRE) prototypes operating in continuous-detonation and continuous-combustion modes using gaseous hydrogen as fuel and gaseous oxygen as oxidizer. For this purpose, a test rig and two LRE prototypes were designed and fabricated. It has been proved experimentally that Zel'dovich thermodynamic cycle with continuous-detonation combustion of hydrogen–oxygen mixture in two different LRE prototypes is more energy efficient than the cycle with continuous constant-pressure combustion of the same mixture, other conditions being equal. Thus, at predetermined limitations on supply pressures of fuel components and at a fixed mass flow rate of fuel mixture the specific impulse of the LRE prototypes operating in the continuous-detonation mode appeared to be 6–8% higher than the specific impulse of the same LRE prototypes operating in the continuous-combustion mode.