Model of the nucleus of a multifront gas detonation

The effect of polydispersity on formation of heterogeneous cellular detonation in gas suspensions of aluminum particles in oxygen is studied by means of numerical simulations and an acoustic analysis. The influence of the suspension composition on the character and size of the cellular structures being formed is found. Partial (and sometimes complete) degeneration of cellular detonation in bidisperse suspensions into a plane detonation wave is observed. Numerical predictions agree with the results of the acoustic analysis of steady detonation structures in bidisperse suspensions. A similar analysis performed for mixtures containing three and five fractions predicts difficulties in formation of cellular detonation in the case of a large scatter in the particle size.

Section: Estimation Of the Size Of Cellular-type Structures By Means mentioning

confidence: 93%

Formation and degeneration of cellular detonation in bidisperse gas suspensions of aluminum particles

Федоров

Khmel

2008

“…For most practically important cases where inequalities (4) are valid, it is possible to show that the proportionality coefficients ahead of the derivative dD dt are negative. In conclusion, we note that except for the practical importance noted in [7,8], the gradient relations obtained in this work can be used in engineering calculations to estimate the values of the derivatives ∂y ∂r * from changes in the velocity of shock or detonation fronts recorded in experiments. In addition, they can be used to construct difference schemes of numerical algorithms near a moving boundary of the type of a shock (detonation) front.…”

Section: Prokhorovmentioning

confidence: 94%

“…For one-dimensional adiabatic flow of a perfect gas, such gradient relations at the shockwave front are given in [5,6]. These relations can be used to develop numerical and analytical approximate methods for solving gas-dynamic problems and establishing asymptotic laws of attenuation of shock waves [7,8]. Here it is also pertinent to note a paper on a related topic [9], in which spatial derivatives were obtained for gas-dynamic functions behind a curved stationary shock wave subjected to an oncoming uniform supersonic flow.…”

mentioning

confidence: 99%

Gradient relations at the front of shock and detonation waves

Prokhorov

2009

A natural assumption on the form of the calorific equations of state (internal energy) for one-dimensional motion was used to obtain the so-called gradient relations that give a one-to-one correspondence between the first partial spatial derivatives of the pressure, density, mass velocity (gradients of parameters) at shock and detonation fronts and the time derivative (acceleration) of the front. The assumption is based on the fact that, taking into account the thermal equation of state, the total internal energy, including both the thermodynamic part and potential chemical energy, can be represented as a function of pressure and density. This holds for both inert media and reaction products in the state of chemical equilibrium.Key words: shock wave, detonation wave, gradients of parameters, acceleration of the front.The strong-discontinuity relations, which are often called the laws of conservation of mass, momentum, and energy at the shock front, are well-known [1,2]. With the thermal effect of chemical reactions taken into account, these laws of conservation are also applicable to a detonation front (a strong discontinuity with heat release) [3,4]. If the motion of the medium behind the front is described by a smooth one-dimensional solution and the parameters ahead of the front are constant, it is possible to give a one-to-one correspondence between the partial spatial derivative (gradient) of any parameter and the time derivative of the velocity (acceleration) of the front. For one-dimensional adiabatic flow of a perfect gas, such gradient relations at the shockwave front are given in [5,6]. These relations can be used to develop numerical and analytical approximate methods for solving gas-dynamic problems and establishing asymptotic laws of attenuation of shock waves [7,8]. Here it is also pertinent to note a paper on a related topic [9], in which spatial derivatives were obtained for gas-dynamic functions behind a curved stationary shock wave subjected to an oncoming uniform supersonic flow. These results were further developed in a study [10] of the behavior of the vortex velocity 1 Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090; prokh@hydro.nsc.ru.vector behind strong-discontinuity surfaces. However, in the cited papers [9, 10], the effect of acceleration of the front on parameter gradients was not considered. The range of application of the gradient relations at the shock front presented in [5, 6] is appreciably limited by the conditions of the perfect gas model [11]; for polyatomic gas and mixtures of various chemically inert gases, this model is approximately valid only in a narrow range of temperatures. Therefore, the previously obtained gradient relations cannot be used for practically important cases such as: 1) gas motion behind strong shock waves, where excitation of additional degrees of freedom and dissociation of molecules are possible; 2) equilibrium flow of reacting gases behind a detonation front propagating in a chemically active m...

“…The losses due to friction and heat transfer to the tube walls are ignored. The latter is caused by the fact that the Vasil'ev-Nikolaev model for calculating the detonationcell size [8,[37][38][39], which is used below, involves the wave parameters without losses on the walls.…”

Section: Detonation-wave Parameters and Cell Size In Gas Mixtures Witmentioning

confidence: 99%

“…According to the model developed in [8,[37][38][39], the longitudinal size of the gas-detonation cell b p depends on the wave velocity and gas parameters (pressure and temperature) behind the leading shock front as…”

Section: Detonation-wave Parameters and Cell Size In Gas Mixtures Witmentioning

confidence: 99%

Effect of chemically inert particles on parameters and suppression of detonation in gases

Fomin

Chen

2009

An algorithm for calculating the parameters of a steady one-dimensional detonation wave in mixtures of a gas with chemically inert particles and estimating the detonation-cell size in such mixtures is proposed. The calculated detonation parameters and cell size in stoichiometric hydrogen-oxygen mixtures with W, Al 2 O 3 , and SiO 2 particles are used to analyze the method of suppression of multifront gas detonation by injecting chemically inert particles ahead of the leading wave front. The ratio between the channel diameter and the detonation-cell size is used to estimate the limit of heterogeneous detonation in the mixtures considered. The minimum mass of particles and the characteristic cloud size necessary for detonation suppression are calculated. The effect of thermodynamic parameters of particles on the detonation suppression process is analyzed for the first time. Particles with a high specific heat and (if melting occurs) a high phase-transition heat are found to exert the most pronounced effect.