On the mechanism of the deflagration-to-detonation transition in a hydrogen-oxygen mixture
- PDF / 1,812,913 Bytes
- 15 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 221 Views
AL, NONLINEAR, AND SOFT MATTER PHYSICS
On the Mechanism of the DeflagrationtoDetonation Transition in a Hydrogen–Oxygen Mixture M. A. Libermana,b,*, M. F. Ivanovc, A. D. Kiverinc, M. S. Kuznetsovd,**, T. V. Rakhimovab, and A. A. Chukalovskiib aDepartment
of Physics, Uppsala University, SE75121, Uppsala, Sweden Institute of Nuclear Physics, Moscow State University, Moscow, 119992 Russia cJoint Institute for High Temperatures, Russian Academy of Sciences, ul. Izhorskaya 13/19, Moscow, 125412 Russia d Forschungszentrum Karlsruhe, Karlsrue, 76021 Germany *email: [email protected] **email: [email protected] b
Received March 15, 2010
Abstract—The flame acceleration and the physical mechanism underlying the deflagrationtodetonation transition (DDT) have been studied experimentally, theoretically, and using a twodimensional gasdynamic model for a hydrogen–oxygen gas mixture by taking into account the chain chemical reaction kinetics for eight components. A flame accelerating in a tube is shown to generate shock waves that are formed directly at the flame front just before DDT occurred, producing a layer of compressed gas adjacent to the flame front. A mixture with a density higher than that of the initial gas enters the flame front, is heated, and enters into reaction. As a result, a highamplitude pressure peak is formed at the flame front. An increase in pressure and density at the leading edge of the flame front accelerates the chemical reaction, causing amplification of the compression wave and an exponentially rapid growth of the pressure peak, which “drags” the flame behind. A highamplitude compression wave produces a strong shock immediately ahead of the reaction zone, gen erating a detonation wave. The theory and numerical simulations of the flame acceleration and the new phys ical mechanism of DDT are in complete agreement with the experimentally observed flame acceleration, shock formation, and DDT in a hydrogen–oxygen gas mixture. DOI: 10.1134/S1063776110100201
1. INTRODUCTION The wave of a chemical reaction in a gas mixture is one of the most fundamental manifestations of the propagation of an exothermic reaction and holds a central position in the study of combustion processes. Two stationary regimes of combustion wave propaga tion are known [1] to be possible in a gas mixture: slow combustion (deflagration) and a supersonic detona tion wave. The deflagration wave propagates through the diffusion of heat and (or) free radicals from the reaction zone into the fresh mixture ahead of the front, so that its velocity is much lower than the speed of sound and the pressure is almost constant. The other (supersonic) combustion wave propagation mecha nism is associated with shock waves. In the detonation wave, the gas is compressed and heated by a strong leading shock that ignites the gas mixture. It is well known [2–5] that when a flame propagates in a bounded space, for example, in a shock tube, the flame velocity gradually increases and a sudden, very rapid formation of detonation occurs
Data Loading...
