Bypass piston tube, a new device for generating high temperatures and pressures in gases.

Abstract

A new device, the bypass piston tube (BPP tube), for the laboratory production of temperatures exceeding 10 4°K and pressures above 10 3 atm in gases is presented. In principle, the device is essentially a shock tube and a ballistic piston compressor linked in tandem by a bypass channel. With this device a gas can be heated under considerable entropy increase, and the volumetric compression ratio can be kept desirably small. A simple theory for the kinematics and thermo-gasdynamics of the BPP tube, and the anticipated over-all performance are given. Experiments conducted in argon with a small BPP tube are described. The measured temperatures and pressures were of the order T = 1.0 X 10 4°K and p = 0.3 X 10 3 atm, which generally agree with the theory. The BPP tube principle advantageously could be used for high-performance shock-tube drivers (shock speed u s > 12 km/sec, initial pressure pi > 1 mm Hg), for launching of hypervelocity projectiles (projectile speed u p > 10 km/sec), and for producing hypervelocity, high-enthalpy flows in nozzles.Nomenclature a = speed of sound A -BPP tube cross-sectional area D -diameter of compression tube E -= internal energy k = Boltzmann's constant L Bp = length occupied by preheated driver gas before bypass L D = fictitious length defined by total entropy production in •••compression, tube Lk -compression tube length ra = mass of gas particle M -mass of free piston Ms = shock Mach number N = total number of bypassing gas particles p -pressure (p) = average pressure defined by Eq. (2) p -dimensionless pressure p/po q = dimensionless energy loss parameter Q ....= .. total energy loss R = gas constant k/m s -specific entropy t = time t = dimensionless time t/.r T = temperature f = dimensionless temperature T/T Q W = pressure work x = piston distance to end wall x = dimensionless distance X/XQ y = specific heat ratio A£ = duration of bypass process £ = dimensionless filling parameter denned by Eq. (6) p = density T = characteristic time for piston bounce, T = (Mxo/Apo) llz Subscripts f -"final" gas condition in piston bounce fill = ideal, homogeneous gas condition after "filling" of compression tube r = condition of driver gas behind reflected shock wave 0 = reference gas condition for isentropic bounce 1 = initial driver-gas condition 2 = condition of driver gas behind incident shock wave 4 = initial condition of accelerating gas 5 = condition of driver gas before bypass 6 = condition of driver gas after passage of unsteady expansion wave in bypass process

Theoretical and experimental study of piston gas-heating with laminar energy losses

“…(1) dp/dt (2) Here, the gas density is denoted p, the pressure p (spatially uniform), the temperature T, the enthalpy h, and the thermal conductivity X. The coordinate perpendicular to the wall is denoted y, and the gas velocity v, is positive in the y direction.…”

Simulation study on modeling for design parameters analysis of free-piston tunnels

“…So, the operation condition in free-piston shock tunnel was first tuned by Stalker 2 by assuming a constant driver gas condition after the diaphragm rupture. Different large scale facilities with a massive piston operating at high speed, such as T5 facility, 3 RHYEL, GASL facility, 4 HIRST facility, 5 PGU facility, 6 HEG facility, 7,8 Stella's BPP tube facility, 9 X2 and X3 facilities 10,11 were developed to overcome the overdriving and to achieve soft landing at the same time.…”