Metallic structures

HEG piston box

 

This report describes the FE analyses for the assessment of piston box stability for the High Enthalpy Shock Tunnel Göttingen (HEG).

The piston box records the HEG piston box performance data. The aim behind the design of a new piston box is to create additional impoundment volume by reducing the mass from 37.5kg to 24kg.

The piston box is sealed with axial sealing rings, so that a maximal differential pressure of 150 bar should be applied. The operational ambient temperature lies between -100°C and 45°C. Decelerating the flight piston with propellant gas can lead to maximum accelerations of around 7,000g.

It has to be anticipated that the piston will drive into an end restrictor that consists of a copper ring. In this case, an impact speed of 40m/s and a deceleration path of 2mm can be assumed.

Due to the strong dynamic operational stresses and strains, transient FE computations were occasionally used as proof of structural integrity.

Tunnelsimulation

 

Aerodynamic experiments on moving trains, particularly when they are passing through tunnels, are difficult to realize in conventional wind tunnels.

Leichtwerk AG therefore designed a tunnel simulation facility for the DLR in Göttingen. Here, a train model is accelerated through a catapult until it reaches the designated test speed. Various experiments can be set up along the route. The dynamics of the catapult and the towing equipment were determined with the aid of computational simulations.