Initial Measurements during the commissioning phase of the High Enthalpy Shock Tunnel Goettingen (HEG)

Abstract

During the commissioning phase initial measurements have been performed at 50, 100, 150 MPa and 200MPa. Comparisons of experiment with a computer code for modelling the driver section has proviede excellent agreement for the 50 and 100 MPa conditions and good agreement for the 150 MPa conditions. In the latter case and perhaps for the 200 MPa burst condition, an improved model of the air pressure behind the may be ncessary. This is probably due to a variation in the air sound speed and ratio of specific heats at high pressures. Further consideration may also need to be given to the ratio of specific heats for the driver gas at high pressures. At all conditions so far a holding time has been achieved in the range from 1.3 to 2 ms. The pressure recovered in the reservoir in the entrance to the nozzle has been, in all cases where a significant holding time exists, approcimately equal to the diaphragmburst pressure. For a driver compression ratio of 60 and operation attailored conditions, a stagnation enthalpy of some 18-20 MJ/kg has been achieved. With these input conditions a test time of some 1 ms with a useful core of about 500 mm has been established for the 100 MPa and 150 MPa condition. Note that no measurement of helium contamination has yet been made. While a range of densities of been achieved in the facility, the free-stream velocity has remained approcimately constant throughout. To obtain higher enthalpies while maintaining tailored conditions, it is necessary to increase the compression ratio of the facility.Correspondigly, the enthalpy can be reduced by decreasing the compression ratio or more easily by introducing a small percentage of argon into the driver gas. Here care needs to be taken to adjust the driver conditions so that facility operatures safely and the holding time is maintained.