Numerical Investigation On Simulation Of Gaseous Detonation With Detailed Chemical Kinetics Model

Recently, the frequent occurrence of industrial explosion disasters bring a serious threat to the people’s life and property safety, thus the prevention and control of industrial explosion have become an urgent problem to be solved at present. On the other hand, with the development of the pulse detonation engine, the rotating detonation engine and the oblique detonation engine, it is urgent to study the propagation mechanism of the gas detonation. Therefore, the study of gas detonation is very important to the industrial explosion disasters prevention as well as the detonation propulsion. Gas detonations contain a series of complex physical mechanism, which is not only a fluid dynamic process, but also a complicated chemical reaction. It is a strong coupling of physical flows and chemical reactions. This paper has following main research and innovations:(1) Based on 8 species 20 steps detailed chemical kinetics model of hydrogen and oxygen, the multi-species reactive Euler equations are established to describing the hydrogen and oxygen detonation. Using third-order Additive Runge-Kutta schemes in time discretization, and using fifth-order weighted essentially non oscillatory(WENO) scheme in spatial discretization, a high solution large scale program is developed. The Additive Runge-Kutta schemes can be used to solve stiff source term caused by multispecies chemical reaction, and the superiority of Runge-Kutta Additive scheme is verified by using the convection reaction equation.The numerical simulation of 1D detonation wave propagation process is carried out by using the high accuracy program and the influence of grid size on the numerical simulation results is studied. The characteristic parameters of detonation wave flow field and the concentration variation of species in detonation process are given. The propagation of 2D detonation wave in straight channel is simulated. The detailed detonation wave structure and the species concentration distribution at the detonation wave front are given, which further proves the feasibility and superiority of this program in the detonation simulation.(2) The numerical simulation of detonation with concentration gradients is investigated. The results show that the detonation wave propagation through several mixtures with different kinds of concentration gradients. The propagationmechanism of detonation wave with different concentration gradients is analyzed,which shows that the concentration gradients have a significant effect on the detonation propagation mechanism. For the lower concentration gradients, the propagation mechanism of detonation wave is the same with propagation mechanism of detonation wave in uniform mixture, which is sustained by collision of triple point structure. With increasing of the concentration gradients, the propagation mechanism of detonation wave is changed which is sustained by the combined action of Mach stem and transverse wave. When the concentration gradients increase to a certain value, the propagation of the detonation wave is sustained by the over driven detonation wave which is formed by Mach reflection. In addition, it is also found that the channel width has an important influence on the detonation wave propagation mechanism under concentration gradients. When the width is not more than 36 mm, the detonation wave in the concentration gradient can only exist two types of interaction, which one is no reflection at the wall and the flow state after the wave changes the shape of the detonation wave front and the other type is that the Mach reflection of the detonation wave occurs at the wall. When the channel width is not less than 72 mm, there are three types of interaction. In addition to the above two types, there is a type of regular reflection at the wall when the angle of the detonation wave is large enough.(3) The numerical simulation of detonation initiation by the convergence of shock waves is investigated. The results show the detonation initiation by shock wave focusing at hemispherical concave cavity, semi-ellipsoidal concave cavity and conical concave cavity. The results show that the three types of concave cavity all achieve the detonation initiation in the central axis, which the shock wave focusing in semi-ellipsoidal concave cavity is the most obvious. The three types of concave cavity achieve the detonation initiation at different time, which the conical concave cavity is the earliest and the semi-ellipsoidal concave cavity is last. The three types of concave cavity all achieve the cycle detonation, which the conical concave cavity has the highest frequency and the semi-ellipsoidal concave cavity has the lowest frequency. The results provide reliable data for the structural design of concave cavity in pulse detonation engine.(4) The numerical simulation of three dimensional detonation is carried out with highresolution parallel program based on detailed chemical kinetics model. The explicit implicit Runge-Kutta Additive method is firstly applied to numerical simulation of the 3D detonation. The 3D detonation simulation not only increases the computational domain but also need smaller mesh grid than 2D detonation simulation to describe the global characteristics of the 3D detonation flow field and the structure of detonation wave front. It is found that 3D detonation exhibits different propagation modes under different disturbance modes. For the three different width channels, the detonation wave is propagated in the rectangular mode under the transverse cosine disturbance, and the beat wave structure is formed on the wall surface. With the pipe width doubled, the number of three wave lines on the detonation wave front is doubled.