An approximate theory of gun tunnel behaviour

Abstract

Approximate methods are used in a theoretical investigation of piston acceleration, peak pressure and piston oscillations in a gun tunnel. Behaviour in all these respects, at a given ratio of initial driver and test gas pressures, is related to the value of a ‘gun tunnel parameter’, Λ, and the ratio of the speeds of sound in driver and test gases. It is shown that large values of Λ must be combined with an enhanced speed of sound in the driver if high performance is to be achieved with manageable peak pressures. With air as test gas, using values of Λ achieved in current practice and a suitable driver gas, the analysis indicates that piston speeds approaching four times the speed of sound in air may be obtained.

An Experimental Evaluation of Transient Flows in Supersonic Gun Tunnel

“…The piston comes to rest with equal pressure on its two sides, and the heated and compressed driven gas ruptures a diaphragm and flows through the nozzle. As the piston travels through the driven section it overshoots its equilibrium position, causing a pressure peak (Stalker, 1965). This transient rapidly disappears, and the pressure of the driven gas essentially remains constant until the gas is exhausted or until an expansion wave from the driver section reaches the piston.…”