This abstract is related to the special session on "Stalker Tubes" organized by Prof. Richard Morgan.
The HEG is a Stalker Tube (free piston driven shock tunnel) which was developed and constructed in the framework of the European HERMES program over the period 1989 – 1991. It was commissioned for use in 1991, at that time being the largest facility of its type worldwide. Since then it was extensively used in a large number of national and international space and hypersonic flight projects. The research activities which were always strongly linked with CFD investigations range from the calibration process of the facility and the study of basic aerodynamic configurations, which are well suited to investigate fundamental aspects of high enthalpy flows, to the investigation of complex entry, re-entry, hypersonic flight and integrated scramjet configurations.
The overall length of HEG is 62 m and it weighs 280 t. Approximately a third of its weight is contributed by an inert mass required to minimize the facility recoil motion. The compression tube is closed by a hydraulic oil system at the main diaphragm station. The shock tube is connected to the nozzle of the tunnel at the downstream closure, which is also driven by oil hydraulics to close and seal the tunnel. The compression tube has a length of 33 m and a diameter of 0.55 m. The shock tube is 17 m long with a diameter of 0.15 m. The HEG was designed to provide a pulse of gas to a hypersonic convergent - divergent nozzle at stagnation pressures of up to 200 MPa, and stagnation enthalpies of up to 23 MJ/kg. Most tests are performed with air as test gas. Additionally, operating conditions using nitrogen and carbon dioxide exist.
Originally, HEG was designed for the investigation of the influence of high temperature effects such as chemical and thermal relaxation on the aerothermodynamics of entry or re-entry space vehicles. In order to correctly model the chemical relaxation occurring behind the bow shock of a re-entry vehicle, the flight binary scaling parameter must be reproduced in ground based testing. Further, for high enthalpy testing an additional driving parameter which must be reproduced is the flow velocity. In addition to the operation at high enthalpies (12 – 23 MJ/kg), the HEG operating range is continuously extended. One emphasis was to generate test section conditions which allow investigating the flow past hypersonic configurations at low altitude for Mach 6 up to Mach 10 flight conditions at approximately 33 km altitude. These low enthalpy conditions cover the range of total specific enthalpies from 1.5 – 6 MJ/kg. The test time for the high enthalpy conditions is up to 1 ms. For the low enthalpy conditions, the test time ranges from 3 – 6 ms.
In order to realise the different operating conditions, a series of different Laval nozzles had to be designed, constructed and implemented in HEG. The exit diameter of the largest nozzle is 880 mm. Further, different pistons are utilised on HEG for generating different operating conditions. In order to allow a large flexibility in tuning new operating conditions, four pistons (without brakes) with different weight (275 kg, 481 kg, 700 kg and 815 kg) are available. One additional 848 kg piston with brakes is utilised. Depending on the chosen operating condition and the angle of attack, model configurations with a typical length between 0.4 m and 1.0 m and a width of up to 0.4 m can be mounted in the test sections. In case where the major emphasis of the tunnel testing is on the investigation of internal flow paths (e.g. scramjet combustors), models of up to 1.5 m length can be used. The weight of the models is typically less than 200 kg.
A gaseous hydrogen injection system was installed at HEG in order to allow the delivery of hydrogen fuel to wind tunnel models for the investigation of scramjet combustion. The fuel system consists of a 12 mm diameter and 38.4 m long Ludwieg tube, and a fast acting solenoid valve. The maximum filling pressure of the Ludwieg tube is 15 MPa and it can deliver a pulse of fuel with constant pressure for up to 50 ms.
The paper will provide the discussion of selected research activities conducted in HEG. The emphasis will be on re-entry flows, hypersonic airbreathing propulsion and hypersonic laminar to turbulent boundary layer transition.
Schematic of the High Enthalpy Shock Tunnel Göttingen (HEG)
Photographic views of the High Enthalpy Shock Tunnel Göttingen (HEG)
