An expansion-Ludwieg tube for accelerating combustible gas mixtures to superdetonative speeds

Abstract
Stoichiometric methane/air and ethylene/air gas mixtures had been successfully accelerated to superdetonative speeds using the classical expansion tube with buffer tube developed at ISL. Hydrogen/air gas mixtures could not be accelerated by this principle. For this purpose a special set-up consisting of an expansion tube using an additional Ludwieg tube as hydrogen reservoir was developed and tested at the ISL Shock Tube Laboratory. With this set-up hydrogen/air gas mixtures can be successfully accelerated to a flow having a superdetonative speed with static pressures up to 215 kPa at 305 K. The experiments in the expansion tube are canied out for basic research purposes on ram-accelerator-related combustion phenomena and also for supporting and optimising the operation of the 30 mm and 90 mm ram accelerator facilities at ISL. We shall discuss problems encountered while using the expansion tube and some preliminary experiments performed with this new facility to prove the homogeneity of the flow.