Strong Detonation Wave Research Articles

Experimental investigation of deflagration to detonation transition in hydrocarbon-air gaseous mixtures

The paper presents the results of investigation of deflagration to detonation transition in gas mixtures with exothermic chemical reaction using the experimental method of nonintrusive diagnostics of the process. Schlieren photochronography in the optical sections in different places of the tube is performed using the laser as a source of light. Experimental results of visualization of the transition process in hydrocarbon-air gas mixtures show several different flow patterns: (1) The detonation wave originates in the flame zone. (2) The detonation wave originates between the flame zone and primary shock wave. (3) The secondary combustion zone originates between primary shock and the flame and causes the detonation. (4) Spontaneous flame occurs that leads to the combustion to detonation transition. The influence of the flame zone on the originating strong detonation wave is noticed.

The Riemann problem for scalar CJ-combustion model without convexity

The Riemann problem for scalar Chapman-Jouguet combustion modelis considered. The entropy conditions are extended from convex case tononconvex one. The existence and uniqueness of the corresponding entropysolutions are obtained constructively.The solutions consist of thegeneralized Chapman-Jouguet detonation and deflagration waves and strongdetonation waves as well as noncombustion waves.

Mechanism of carbon release during detonation decomposition of substances

On the basis of data obtained by the method of ‘labelled’ atoms it is assumed that in strong shock and detonation waves the initial decomposition stages of a condensed substance containing carbon and hydrogen occur primarily with the release of carbon in the diamond phase and methane. Then there is oxidation of methane hydrogen and the release of carbon in a nondiamond phase. The distribution of an isotope label for the condensed products of TH and TO in known experiments is explained on the basis of a hypothesis of complete mixing of the components of fine-grained explosive in the chemical reaction zone.

Harten solution for one-dimensional unsteady equation

In order to use the second-order 5-point difference scheme mentioned to compute the solution of one dimension unsteady equations of the direct reflection of the strong plane detonation wave meeting a solid wall barrier, in this paper, we technically construct the difference schemes of the boundary and sub-boundary of the problem, and deduce the auto-analogue analytic solutions of the initial value problem, and at the same time, we present a method for the singular property of the initial value problem, from which we can get a satisfactory computation result of this difficult problem.

Origination of detonation during multistage self-ignition

The analysis performed shows that multistage self-ignition under known conditions can display the reason for strong shock and detonation wave generation. The wave excitation mechanism is associated with flame self-acceleration as, during the transition of combustion into detonation in tubes and consists of self-consistent motion of pressure and ignition waves. Realization of such a mechanism is quite probable in application to detonations in engines. The high-speed photography of a detonation explosion in an engine [11] actually, discloses the existence of self-ignition waves and records shock generation in local volumes of unburned parts of the charge.

Numerical studies of a detonation analogue

Abstract As an aid to deciding a computational strategy for problems involving strong detonation waves, we have applied a variety of numerical techniques to a mathematical problem devised by Fickett, which exhibits many of the essential computational difficulties and possesses analytical solution corresponding to overdriven and underdriven reacting flows. Classical shock capturing methods such as those of MacCormack and Godunov, do not produce acceptable solutions. Better solutions can be provided by Flux Difference Methods (Roe's method) and by Random Choice Methods (still in one dimension), especially by using a new variant that yields second order accuracy. Adaptive gridding techniques for these methods are currently being investigated with encouraging preliminary results.

Application of Front Tracking to Two-Dimensional Curved Detonation Fronts

This is the first of a series of papers describing a program which has a potential for achieving a significant improvement in the numerical modeling of detonation waves. In this paper, we establish the convergence of the front tracking method for two-dimensional detonation problems. The Chapman–Jouguet (CJ) thin flame model is used. An iterative method for the solution to these model equations, and for which we prove convergence, is described. We then take as a test problem a cylindrically symmetric expanding strong detonation wave. The solution to the model equations in this geometry by the random choice method with operator splitting computed on a fine grid is taken to be exact. The convergence of the front tracking solution to this solution is discussed and convergence rates are established. The methods described above use planar detonation wave speeds. Corrections due to curvature are needed especially for unsupported diverging detonations. This issue will be addressed in the next paper in this series.

Diffraction of a planar strong detonation wave by a moving three-dimensional thin body

An analytic solution is obtained for the diffraction of a planar strong detonation wave by a three-dimensional thin body moving in the opposite direction. The planform and the thickness distribution of the body can be arbitrary and the speed of the body can be either supersonic or subsonic relative to the undisturbed stream ahead of the wave or to that behind the wave. The solution is a generalization of the previous solution of Ting and Gunzburger for the shock diffraction.

On non-one-dimensional selfsimilar solutions with plane waves in gas dynamics

A set of new exact selfsimilar solutions is obtained, describing non-one-dimensional adiabatic motions of an ideal gas with plane waves. The solutions show a uniform expansion of the gas in planes perpendicular to the direction of the basic motion. The system of equations of gas dynamics is reduced for these solutions to a system of ordinary differential equations /1/. Problems of a short shock and the propagation of a strong detonation wave in a uniformly expanding gas was solved numerically in /2/, where an exact solution was also found for the problem of a short shock for a special value of the adiabatic index.

Self‐Similar Cylindrical Ionizing Shock and Detonation Waves

AbstractSelf similar flow patterns are studied which arise when a cylindrical symmetric strong shock or detonation wave propagates outwards into a gas at rest in which the ambient density varies as the inverse square of the distance from the axis of symmetry along which flows a line current of either zero or finite constant strength. The electrical conductivity of the gas is supposed zero ahead and infinite behind, so that the wave is an ionizing wave. It is shown that self similar solutions exist for both shock and detonation waves for which detailed flow patterns are present.

Transition of plane overdriven detonation wave to the Chapman-Jouguet regime

The asymptotic laws of behavior for plane, cylindrical, and spherical infinitely thin detonation waves were found in [1, 2] for increasing distance from an igniting source in those cases in which the waves changed into Chapman-Jouguet waves as they decayed. It was shown that the plane overdriven detonation wave approaches the Chapman-Jouguet regime asymptotically, while the transition of the cylindrical or spherical strong detonation wave into the Chapman-Jouguet wave may occur at a finite distance from the initiation source.

Cylindrical shock and detonation waves in magnetogasdynamics

Self-similar flow patterns are studied which arise when a cylindrically symmetric strong shock or detonation wave propagates outwards into a gas at rest in which the ambient density varies as the inverse square of the distance from the axis of symmetry along which flows a line current of either zero or finite constant strength. The electrical conductivity of the gas on either side of the wave is supposed perfect and the discontinuities discussed are either gasdynamic or magnetogas-dynamic in nature. It is shown that self-similar solutions exist for piston driven gasdynamic detonation and shock waves. Whilst no self-similar solutions may occur for magnetogasdynamic detonation waves, it is demonstrated that magnetogasdynamic shock waves do possess such solutions for which detailed flow patterns are presented.

Thermonuclear Detonation Wave Structure

The structure of a very strong detonation wave (a shock wave followed by a thermonuclear reaction zone) propagating through a deuterium-tritium gas mixture is studied. The shock is sufficiently strong so that it heats the gas to a temperature at which thermonuclear reaction probabilities are large. The characteristic times for collisions and reactions are examined to determine when the von Neumann-Zeldovich model (separate shock and reaction zone) of detonation structure is applicable. Appropriate nuclear reaction kinetics equations are developed for the reaction zone and the effect of energy loss due to bremsstrahlung is included in the analysis. A set of wave structure equations is derived and solved numerically for several different cases. The physical effects expected from a laboratory fast-shock experiment are examined briefly.

Interaction between detonation waves and flowfields.

The study of the interaction between detonation waves and flowfields could lead to a better understanding of combustion instability in rocket motors and to possible application to supersonic combustion. Apparatus was designed to measure the relative wave velocity and to photograph the wave profile as a fully developed detonation wave propagated against a flow of stoichiometric mixture of hydrogen-oxygen gases. The Mach number of the flowing unburned gas was varied from 0.14 to 4. The subsonic flow results were in good agreement with the Chapman-Jouguet theory; but the supersonic flow results indicated a strong detonation wave. The schlieren photographs of the wave indicated propagation into the boundary layer, and a convex curvature of the complete wave front was observed in the Mach 4 experiments. Velocity measurements indicated that the detonation wave was steady, but in some experiments disturbances were observed downstream of the detonation wave.

Calculations of the motion of non-uniform shock waves

Problems of the propagation of shock waves and strong detonation waves through ducts of variable cross-section and ducts with porous walls, and the interaction of a rarefaction wave with a shock and a contact surface in one-dimensional unsteady, or two-dimensional steady, flow are solved using a simple rule. Tables enclosed in this paper permit efficient calculation of several problems of non-uniform shock motion.