Propagation And Self-sustaining Mechanism Of Detonation Wave Influenced By Lateral Expansion

In all kinds of advanced propulsion machinery, detonation engine stands out byvirtue of its higher thermodynamic cycle efficiency. In order to optimize RDE design, itis essential that propagation and self-sustaining mechanism of detonation waveinfluenced by lateral expansion be well understood. This paper makes an analyticalstudy on flow field structures, effects and self-sustaining mechanisms of detonationinfluenced by lateral expansion by the means of theoretical analysis, experimentalobservation and numerical simulation.Two sets of experimental schemes have been designed to research the propagationof detonation influenced by equivalence ratios, diluted inert gaseous concentration,initial pressure, inert gaseous species or chnannel configurations in detail.It was found that there exist three propagating modes of detonation waveinfluenced by lateral expansion: self-sustaining mode, quenching mode and criticalmode. Due to the effect of lateral expansion, the detonation velocity woud deficit andthe detonation front would be distorted. Detonation cellular structures can be dividedinto three regions with different cellular pattern characteristics, constituted of normalcellular structure, disappearing cellular structure and recovery cellular structure. Thedetonation wave influenced by lateral expansion was attenuated by the rarefaction wavealong the unsteady line.By studing propagation characteristics of the detonation influenced by equivalenceratios, we could be convinced that if the sensitivity of the premixed gas is higher, thenthe velocity deficit is smaller and the detonation front is more regular. The generation ofnew transverse wave is vitally important to self-sustain the detonation wave, which isrequired to cope with the attenation by lateral expansion. The self-sustaining range ofargon as the diluted inert gas is wider than nitrogen. The detonation front is moreregular, and the velocity deficit is smaller. The premixed gas height has been changedby filled with different size blocks. It has been observered that the ability of thedetonation wave is stronger to resist the attenuation by lateral expansion if the height ofthe premixed gas is higher.Combined with Fay’s flow divergence theory, Dabora’s lateral expansion theoryand ZND model, propagation characteristics of the detonation wave influenced bylateral expansion have been predicted successfully such as velocity deficits, obliqueshock angle and interface angle. The velocity deficit of detonation wave is proportionalto the length of the reaction zone. It is the growth of the reaction zone in thickness thatcauses the area divergence increased. The detonation wave would fail when the velocitydeficit reaches a certain value. The velocity deficits of detonation wave present the “U”trend with increasing equivalence ratio.The theoretical values are in good agreement with the experimental values. As is observered, the self-sustaining range of equivalenceratio diluted with nitrogen is0.8to2.0, but the detonation wave diluted with argondoesn’t fail when the equivalence ratio reaches0.6and2.5. In addition, it is found thatif the velocity deficits exceed7.0～11.0%, then the detonation would quench dilutedwith nitrogen.