Numerical simulation of classical and rotating detonation waves in methane mixtures

Abstract

A numerical simulations of a two-dimensional multi-front irregular structure of the detonation wave (DW) in methane-based mixtures at normal initial condition have been conducted. The computations have been performed in a wide range of channel height. From the analysis of the flow structure and the number of primary transverse waves in channel, the dominant size of the detonation cell for studied mixtures has been determined. We have simulated the cellular front structure in stoichiometric methane-air and methane-oxygen mixtures, and in a rich (equivalence ratio φ=1.5) methane-air mixture. Based on the fundamental studies of front structure of the classical propagating DW in methane mixtures, numerical simulation of continuous spin detonation of rich (φ=1.2) methane-oxygen mixture has been carried out in the cylindrical detonation chamber (DC) of the rocket-type engine. We studied the global flow structure in DC, and the detailed structure of the front of the continuous rotating DW. Integral characteristics of the detonation process -the distribution of average values of static and total pressure along the length of the DC, and the value of specific impulse have been obtained. The geometric limit of stable existence of rotating DW has been determined. IntroductionOne of the most important problems in the theory of dynamic systems is the formation and destruction of ordered gas-dynamic structures in a reactive medium. An example of such a self-organizing system is a multi-front (cellular) DW steadily propagating in a reacting gas mixture. The complex threedimensional and time-dependent structure of the front of these waves propagating in constant crosssection channels shows some order, whose geometrical parameter is the size of the elementary cell of the DW − a 0 . Based on this value, it is possible to determine such parameters of detonation as critical conditions of detonation combustion, the critical energy of initiation detonation propagation limits, etc., i.e. to estimate the detonation hazard of gaseous mixture. Depending on the chemical composition of the gas, DW in some mixtures have very regular cellular structure, whereas in other mixtures DW shows very irregular chaotic cell structure. A very regular cellular DW structure in hydrogen-oxygen-argon mixtures was studied in our previous 2D numerical simulation [1]. A good agreement was obtained between the numerical results and experimental data on the size a 0 over a wide range of initial pressures and degrees of mixture dilution by argon. Then we have simulated the irregular detonation structure in stoichiometric methane-air [2] and methane-oxygen [3] mixtures.