Direct Experimental Impulse Measurements for Detonations and Deflagrations

Abstract

= pendulum mass P = pressure P env = environment pressure P lip = pressure on lip at exit of tube P TS = pressure on thrust surface in detonation tube interior P 1 = initial pressure of reactants P 2 = Chapman-Jouguet pressure P 3 = pressure of burned gases behind Taylor wave p = pitch of spiral obstacles S = wetted surface area of tube's inner diameter T 1 = initial temperature of reactants t = time U CJ = Chapman-Jouguet detonation velocity V = internal volume of detonation tubē = ratio of N 2 -to-O 2 concentration in initial mixture°= ratio of speci c heats in combustion products 1x = horizontal pendulum displacemenţ = cell size ½ 1 = density of combustible mixture at the initial temperature and pressure ¿ = wall shear stress

Optical and thrust measurement of a pulse detonation combustor with a coaxial rotary valve

“…The PDEs are classified as air-breathing PDEs [19][20][21][22] or pulse detonation rocket engines (PDREs) [23][24][25]. With a simplified PDE setup, that is, when viscosity and heat conduction are neglected and a tube-geometry combustor is fully filled with propellant at ambient pressure and a detonation wave is initiated instantaneously, a PDRE using H 2 -O 2 propellant can achieve a specific impulse of 190 sec and an air-breathing PDE using hydrogen fuel can achieve a specific impulse of 4200 sec, as achieved in experiments by Schuer et al [26], Cooper et al [27] and…”

“…However, Takeuchi et al [44] reported that the specific impulse decreased when the length ratio (l DDT / l p ) between the propellant fill length, l p , and the DDT distance, l DDT , decreased. They varied the initial fill pressure of the H 2 -O 2 stoichiometric mixture and investigated the relation between the DDT distance and the specific impulse by a shingle-shot ballistic pendulum and found that the specific impulse rapidly decreased when the length ratio (l DDT / l p ) was 0.9. Cooper et al [27] also varied the nitrogen-dilution ratio of the mixture and investigated the impact of DDT distance on the specific impulse using a shingle-shot ballistic pendulum. They found that the DDT distance increased as the nitrogen-dilution ratio increased, and the specific impulse decreased compared to a theoretical value.…”

Impulse Correlation for Partially Filled Detonation Tubes

“…2 In other studies, a weakening of bow shocks was observed when heat was added using GDP that formed between the body and the bow shock. 3 The results of these studies demonstrated the potential of the plasma technology in high-speed aerodynamics. The exact nature of plasma-shockwave interaction is not clearly understood.…”

“…The final velocity of the driven mass is determined from the conservation equations and depends on the available chemical energy of the explosive. The impulse corrections applied, measured as a percentage of the measured impulse, are less than 2.3% for Cooper et al, 3 less than 21.3% for Falempin et al, 4 less than 22.3% for Zhdan et al, 2 and less than 25.1% for Zitoun and Desbordes.…”

“…Zhdan et al 2 directly measured the impulse using a ballistic pendulum arrangement of acetyleneoxygen mixtures at standard conditions in a tube with extensions having the same circular cross section. Similarly, Cooper et al 3 and Falempin et al 4 used a ballistic pendulum to measure impulse values of ethylene-oxygen mixtures in detonation tubes with attached extensions having a constant circular cross section and also in extensions of varying dimensions. Li and Kailasanath 5 numerically studied the effect of varying the length filled with the explosive mixture in tubes of constant cross-sectional area on the impulse.…”