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Description
The ESTHER shock tube is a new state-of-the-art facility at Instituto Superior Técnico to support future ESA planetary exploration missions. A high-pressure combustion chamber using a mixture of He:H2:O2 ignited by a high-power Nd:YAG laser acts as the driver. A qualification campaign was carried out with 99 shots and evaluating the effects of air:fuel ratio, filling pressure, inert gas dilution and ignition mode.
Gas filling pressure and helium dilution were the most dominant parameters controlling on the driver performance. The gas mixture peak pressure and acoustic wave amplitude increase with the increased filling pressure. Higher filling pressures required the use of higher dilution factors or leaner mixtures to avoid transitions to detonation, this however slightly decreased the driver performance. Low velocity shots were also tested by replacing helium with nitrogen in the combustion chamber. This drastically lowers the driver gas peak pressure and temperature, which in turn creates slower shockwaves.
The qualification results served as input for numerical performance simulations. The results estimate ESTHER performance envelope. The facility should be capable of creating shock wave velocities in the 4 to 14 km/s range.
Summary
This work presents the main results from ESTHER's driver qualification campaign. Effects of air:fuel ration, filling pressure, helium/nitrogen dilution and laser ignition mode on the peak pressure, acoustic wave amplitude and flame velocity. The expected performance map is the computed using a numerical simulation tool.
