Forward-Running Detonation Drivers for High-Enthalpy Shock Tunnels

Abstract

To improve the quality of driving ows generated with detonation-driven shock tunnels operated in the forwardrunning mode, various detonation drivers with specially designed sections were examined. Four con gurations of the specially designed section, three with different converging angles and one with a cavity ring, were simulated by solving the Euler equations implemented with a pseudo kinetic reaction model. From the rst three cases, it is observed that the re ection of detonation fronts at the converging wall results in an upstream-traveling shock wave that can increase the ow pressure that has decreased due to expansion waves, which leads to improvement of the driving ow. The con guration with a cavity ring is found to be more promising because the upstream-traveling shock wave appears stronger and the detonation front is less overdriven. Although pressure uctuations due to shock wave focusing and shock wave re ection are observable in these detonation-drivers, they attenuate very rapidly to an acceptable level as the detonation wave propagates downstream. Based on the numerical observations, a new detonation-driven shock tunnel with a cavity ring is designed and installed for experimental investigation. Experimental results con rm the conclusion drawn from numerical simulations. The generated driving ow in this shock tunnel could maintain uniformity for as long as 4 ms. Feasibility of the proposed detonation driver for high-enthalpy shock tunnels is well demonstrated. NomenclatureD CJ = Chapman-Jouguet (C-J) detonation velocity e = total energy per mass= molecular weight of the reactant m 2 = molecular weight of the product P CJ = C-J detonation pressure P i = initial pressure in driver section P ignit = ignition pressure P 0 = initial pressure in driven section p = pressure Q = reaction heat per mass S, H = source terms= mass fraction of the reactant Z 2 = mass fraction of the product ®,¯, Adet = tuned constants of reaction model°= effective adiabatic exponent°1 = adiabatic exponent of the reactant°2 = adiabatic exponent of the product 1s = local mesh size

Detonation driver for enhancing shock tube performance

“…This partial reflection serves to trap highpressure gas in a fashion similar to a reflected shock tunnel and serves to alleviate attenuation from the Taylor rarefaction, thereby prolonging the duration of uniform flow within the driven tube. Jiang et al (1999Jiang et al ( , 2002 have further studied this technique of increasing the run time and flow uniformity through the use of "cavity rings." Finally, at the end of a successful run, the end diaphragm is blown away and the entire shock tube is vented.…”

Advances in detonation driving techniques for a shock tube/tunnel

“…It is found that the flow field behind a detonation wave generated by the tube with a cavity ring is more uniform than that by the tube with a 30 • or 45 • converging section. In order to verify the results, a forward-detonation driven shock tube has been manufactured in LHD [18]. The detonation driver consists of a large tube (3.87 m long and 90 mm in Dia.…”

Performance of a detonation driven shock tunnel

“…The data deduction carried out only by pitot pressure measurements is not enough to validate the real flow condition, other measures such as heat-flux measurements and spectrum analysis are necessary to fully detect the flow characteristics, which were already reported in [7]. The amount of transducers consumed during the test is high, few are working normally at last.…”

“…However, due to the Taylor rarefaction wave which follows the detonation front, the primary shock wave is attenuated. Jiang et al [7] and Zhao et al [10] developed some ways to solve these problems. Another problem to solve then was to burst the primary metal diaphragms, which produced fragments at the moment of rupture.…”