The T4 Stalker tube, a free-piston reflected shock tunnel, was commissioned in 1987. By June 2014, it had been fired over 11500 times. An important design objective for T4 was for it to be capable of producing test flows suitable for scramjet testing. A large proportion of the shots in T4 have been for research into scramjets and scramjet subsystems.
The compression tube of T4 is 26 m long and has a bore of 229 mm. A steel piston of 92 kg mass has been used almost exclusively. A small number of tests have been performed with an aluminium piston of one-third of the mass. The driver gas is usually either helium or argon or a mixture of the two gasses.
Ray Stalker designed and oversaw an upgrade of the air reservoir that drives the piston in 2000. This provided a larger volume and higher pressure capability than the original reservoir for the tunnel when it was first commissioned. The upgraded reservoir wraps concentrically around the compression tube. The compression tube can slide within the reservoir and the relative motion between the two tubes is controlled by a set of springs and shock absorbers. The reservoir has an internal volume of 1.2 m3 and a maximum working pressure of 14 MPa. This was the last major shock tunnell design activity undertaken by Stalker and the change resulted in an important upgrade of the capcabilities of T4. Unscored mild-steel primary diaphragms of thicknesses between 1 mm and 6 mm spearate the compression tube from the shock tube before diaphragm rupture.
The shock tube is 10 m long and has a bore of 76 mm. The tunnel is routinely run at nozzle-supply pressures up to 50 MPa but this can be increased to 90 MPa when required. The nozzle-supply enthalpies routinely used range from 2.5 to 12 MJ/kg. At higher enthalpies than this, for the tunnel in its present configuration, early contamination of the test gas by the driver gas compromises the duration of steady, uncontaminated test flows.
Contoured, axisymmetric nozzles for exit Mach numbers of nominally 4, 6, 7, 8 and 10 are available for T4. The nozzles are designed for a particular nozzle-supply condition (enthalpy and pressure) and the Mach number at exit of the nozzle varies, particularly with nozzle-supply enthalpy due to high-temperature effects on the gas. For example, the mean exit Mach number in the test core of the Mach 6 nozzle decreases from 6.7 at 3 MJ/kg to 5.5 at 12 MJ/kg.
In the paper, a review of the T4 stalker tube will be presented. This will be followed by example results from experiments performed in the tunnel, from its commissioning in 1987 until the present, that demonstrate the capabilities of the tunnel and some of the important results obtained from it.
