scholarly journals Melting Point of Carbon Particles behind the Gas Detonation Front

2022 ◽  
Vol 16 (2) ◽  
pp. 59-70
Author(s):  
E. S. Prokhorov

A mathematical model of gas detonation of fuel-enriched mixtures of hydrocarbons with oxygen has been formulated, which makes it possible to numerically study the equilibrium flows of detonation products in the presence of free carbon condensation. Reference data for graphite were used to describe the thermodynamic properties of carbon condensate. The calculations are compared with the known results of experimental studies in which, when detonating an acetylene-oxygen mixture in a pipe closed at one end, it is possible to obtain nanoscale particles from a carbon material with special properties. It is assumed that the melting point of such a material is lower than that of graphite and is about 3100 K. Only with such an adjustment of the melting temperature, the best agreement (with an accuracy of about 3 %) was obtained between the calculated and experimental dependence of the detonation front velocity on the molar fraction of acetylene in the mixture.

2019 ◽  
Vol 484 (5) ◽  
pp. 550-553
Author(s):  
E. L. Popov ◽  
A. N. Samsonov ◽  
F. A. Bykovskii ◽  
E. F. Vedernikov

Conversion possibility of the chemical energy of combustion products of a hydrogen–oxygen mixture into electrical energy with the use of continuous spin detonation has been demonstrated for the first time in an MHD system. The specific conductivity of detonation products in the region of rotation of the detonation front was measured to be ~3 · 10–2 Ω–1 m–1. The structure of transverse detonation waves was examined, their velocity was measured (2220 ± 50 m/s), and the flow in their vicinity was studied.


The fundamental physical, chemical and mechanical processes which occur when a detonation wave passes through an explosive were imperfectly understood at the beginning of the recent war. As part of the scientific war effort in the British Common-wealth and in the United States of America, many theoretical and experimental studies were made of detonation processes. Much of the work has recently been declassified and some has been published. Several centres of research in this country and elsewhere are vigorously continuing with these studies. As later papers will show, the quality and general scientific interest of much of this work was considered sufficient to form the basis of a Discussion of the Royal Society. If one neglects the finite width of the zone in the detonation front where chemical reactions occur, a freely running steady plane detonation front can only advance through an explosive with the Chapman-Jouguet velocity defined by D = u + c . Once the explosive products are formed, their subsequent chemical reactions and motion in the detonation front may be considered as adiabatic. Although Chapman (1899) and Jouguet (1901) correctly stated their equation, neither attempted to discuss the reaction zone itself. It was therefore thought necessary that the recent views on the reaction zone should be described in a manner which throws new light on the Chapman-Jouguet equation. Professor J. von Neumann, Dr⋅ S. F. Boys and Dr A. F. Devonshire were the principal contributors on the theoretical side and von Neumann’s theory (1942) will be outlined later.


1984 ◽  
Vol 62 (5) ◽  
pp. 431-434 ◽  
Author(s):  
P. Calvani ◽  
F. De Luca ◽  
B. Maraviglia

T1 has been measured at 4 MHz and 78 K < T < 120 K in mixtures having a Kr molar fraction c up to 0.8. The transition temperature Ts, corresponding to the solidus curve, has been determined for several values of c by observing the large discontinuity in T1 as in pure CH4. In the solid phase, the intermolecular dipolar contribution to the relaxation rate is found to be dominant at T > 80 K, and our data are in agreement with a simple model based on the Torrey–Sholl theory. Above the melting point, T1 becomes independent of c, thus suggesting that relaxation may be driven by intramolecular interactions in the liquid phase.


2015 ◽  
Vol 10 (4) ◽  
pp. 77-84
Author(s):  
Evgeniy Prokhorov

The quasi-one-dimensional model is presented to describe the propagation of detonation wave in a tube filled with an explosive gas mixture, the chemical composition of which varies along the tube axis. This takes into account energy losses chemical equilibrium flow of detonation products for friction and heat removal in the tube wall. Within the limits of this model, it numerically investigated the gas detonation transition through a region with the concentration gradient of chemical agents. It analyzed the possibility of excitation overdriven detonation waves as a result of this transition.


2010 ◽  
Vol 24 (13) ◽  
pp. 1337-1340 ◽  
Author(s):  
CHENG WANG ◽  
TIANBAO MA

In this paper the two-dimensional Euler equations, with a simple chemical reaction model, are used as the governing equations for the detonation problem. The spatial derivatives are evaluated using the fifth-order WENO scheme, and the third-order TVD Runge-Kutta method is employed for the temporal derivative. The characteristics of the two-dimensional detonation in an argon-diluted mixture of hydrogen and oxygen are investigated using Adaptive Mesh Refinement (AMR) method. From computational accuracy point of view, AMR enables the detonation front to be clearer than the method with basic meshes. From the other point of computational time, AMR also saves about half the time as compared with the case of refining the entire field. It is obvious that AMR not only increases the resolution of local field, but also improves the efficiency of numerical simulation.


2021 ◽  
Vol 3 (1(59)) ◽  
pp. 6-15
Author(s):  
Sergii Shlyk

The object of research is the processes of pulse explosive loading in an explicit formulation for simulation of complex nonlinear dynamics of solids, gases, and their interactions. One of the most problematic areas of modern studies of nonlinear dynamic loads of materials using a numerical analysis is that such studies usually do not take into account the characteristic transition of the stationary deformation zone of the loaded material to the unsteady one and the front pressure and shockwave velocity variation by time. The work is aimed at developing a mathematical model of a pulsed load of materials by a shockwave, developing a mathematical apparatus for calculating the parameters of a shockwave, creating analytical dependences of the interaction of a shockwave with a loaded surface. A study of dynamic explosive loading using software based on an explicit method for solving the equations of continuum mechanics is proposed. In this work, the stress-state equation at a point of the material under pulsed load conditions was further developed, methods for determining the principal stresses and the invariant of the stress tensor, taking into account the pulsed nature of the load, were established. The character of the behavior of the shockwave formed as a result of the detonation of the explosive has been established. Analytical dependences of the interaction of a shockwave with a loaded surface are compiled. A mathematical apparatus has been developed for calculating such parameters of the shockwave as the detonation front pressure and its change in time and the velocity of the shockwave at the moment when it reaches the surface. Mathematical dependences have been developed and proposed, which, in contrast to the existing ones, make it possible to determine the current values of stresses and strains passing through the points of the actual stress curve, as well as the intensity of stresses and strains under pulse loading of metals. On the basis of theoretical and experimental studies of the parameters of body material deformation under the action of explosive loading, the mechanisms of destruction of the KrAZ «Shrek» and KrAZ «Fiona» (Ukraine) specialized armored vehicles body were clarified to establish the compliance of the declared landmine resistance of vehicles with the STANAG 4569 standardization agreement.


2017 ◽  
Vol 836 ◽  
pp. 324-351 ◽  
Author(s):  
Xiaodong Cai ◽  
Ralf Deiterding ◽  
Jianhan Liang ◽  
Mingbo Sun ◽  
Yasser Mahmoudi

In the present work, the role of diffusion and mixing in hot jet initiation and detonation propagation in a supersonic combustible hydrogen–oxygen mixture is investigated in a two-dimensional channel. A second-order accurate finite volume method solver combined with an adaptive mesh refinement method is deployed for both the reactive Euler and Navier–Stokes equations in combination with a one-step and two-species reaction model. The results show that the small-scale vortices resulting from the Kelvin–Helmholtz instability enhance the reactant consumption in the inviscid result through the mixing. However, the suppression of the growth of the Kelvin–Helmholtz instability and the subsequent formation of small-scale vortices imposed by the diffusion in the viscous case can result in the reduction of the mixing rate, hence slowing the consumption of the reactant. After full initiation in the whole channel, the mixing becomes insufficient to facilitate the reactant consumption. This applies to both the inviscid and viscous cases and is due to the absence of the unburned reactant far away from the detonation front. Nonetheless, the stronger diffusion effect in the Navier–Stokes results can contribute more significantly to the reactant consumption closely behind the detonation front. However, further downstream the mixing is expected to be stronger, which eventually results in a stronger viscous detonation than the corresponding inviscid one. At high grid resolutions it is vital to correctly consider physical viscosity to suppress intrinsic instabilities in the detonation front, which can also result in the generation of less triple points even with a larger overdrive degree. Numerical viscosity was minimized to such an extent that inviscid results remained intrinsically unstable while asymptotically converged results were only obtained when the Navier–Stokes model was applied, indicating that solving the reactive Navier–Stokes equations is expected to give more correct descriptions of detonations.


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