Detonation of propane-air mixtures under injection of hot detonation products

The tube for spontaneous detonation (Institute of Technical Physics, Russian Federal Nuclear Center, Snezhinsk) was used to study the initiation and development of detonation in propane-air mixtures under injection of hot detonation products into them. The full picture of this phenomenon was recorded: the injection of hot detonation products into the main tube of the facility with the formation of a mixture of the starting propane-air composition with the hot products; the initiation of a local explosion in this mixture and the subsequent development of a detonation in it; detonation transfer to the region of the cold starting reactants (or detonation failure at the interface). The detonation was found to exist for an initial volume concentration of propane of 3.3 to 5%. The following critical (by the moment of the local explosion) parameters were determined: a mass fraction of hot detonation products of 6–9%, an energy input density due to product injection of 145–195 J/g, and an input energy power of 70–50 J/(g · msec). __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 3, pp. 100–109, May–June, 2006.     

Combustion and detonation of propane–air compositions in large-scale experiments

This paper presents the results of two large-scale tests performed to clarify the conditions for the detonation of propane–air compositions in model surface clouds in the absence and in the presence of confining rigid walls. Model clouds with dimensions of 15 × 6 × 4.2 and 15 × 6 × 2 m were confined by plastic tents. A mixture of the starting reagents in the cloud was ignited by hot detonation products propagating along a perforated ø0.82 × 23 m tube passing through the space of the tent. Hot detonation products were injected from the tube through holes of 20 and 40 mm diameters. Detonation of the propane-air mixture in the tube was initiated by explosion of an explosive charge placed at the tube end. Detonation occurred in the propane–air cloud bounded on one side by a rigid vertical wall, and no detonation was observed in the cloud with similar injection of hot products without a rigid wall. It is concluded that the divergence or convergence of the flows of hot detonation products plays a key role in the process, being responsible for the presence or absence of detonation, respectively, in the mixing region.     

Comparison between the shock wave and chemical initiation in detonation of acetylene—oxygen mixtures

Detonation of different compositions of acetylene-oxygen mixtures by both chlorine gas injection and a shock wave as initiators is studied in this research. The chlorine gas is injected into the detonation tube through a reticular plate nozzle at the moment when a thin aluminum foil separating the injection system from the detonation tube is torn by a pressurized nitrogen gas. The results of experiments show that chemical initiation may be as effective as direct initiation of detonation and, therefore, replace more complicated methods of initiation. The best results are obtained in acetylene— oxygen mixtures with the molar ratio of 1: 1.     

The Equation of State of Detonation Products obtained from cylinder expansion test

The equation of state of detonation products is essential to the explosive application. The study of this paper is set up with the following procedures: (1) cylinder expansion test is performed in a detonation test chamber, and the radial expansion, varied with time, of copper tube which is filled with Composition B, is recorded by Hamamatsu streak camera, (2) the JWL parameters are obtained by means of a simple mathematical analysis, and (3) the 2DL Code has been modified using JWL equation of state instead of HOM equation of state to study the behavior of the detonation gases. The results show that the JWL parameters of this study are in close agreement with the LLNL's approach and the JWL equation of state can more accurately predict the behavior of detonation products than the HOM.     

Realization and modeling of continuous spin detonation of a hydrogen-oxygen mixture in flow-type combustors. 2. Combustors with expansion of the annular channel

Results of a comprehensive numerical and experimental study of continuous spin detonation of an H₂-O₂ mixture in flow-type annular combustors with channel expansion are presented. In these experiments, oxygen is supplied as a continuous flow through an annular slot, and hydrogen is injected through injectors. Combustion of hydrogen-oxygen mixtures in continuously rotating (spinning) and pulsed detonation waves with exhaustion of the products into an evacuated tank with increasing counterpressure and into the atmosphere was realized and studied in such combustors for the first time. The domain of realization of continuous detonation is determined. Verification of the mathematical model is performed on the basis of experimental results, and reasonable agreement is reached for the basic detonation parameters: structure of transverse detonation waves, their velocity, and pressures in the combustor and in the injection system.     

An Improved Simple Method of Deducing JWL Parameters from cylinder expansion test

A simple method which is much simpler than, while retaining the same degree of accuracy, as that of a large computer hydrocode has been developed for deducing the JWL equation of state (EOS) of high explosive detonation products from the cylinder expansion test. The radial expansion history of metal tube, which is recorded by the streak camera, is expressed as an appropriate fitting function with the aid of a nonlinear curve fitting procedure. The measured data with respect to Eulerian coordinate are transformed to that in Lagrangian coordinate so that the p-V relation of detonation products may be obtained from the differentiation of fitting function and equations of conservation law. Metal strength is also taken into consideration to reduce the deviation at the lower pressure region. JWL parameters are acquired through the p-V relations by another nonlinear curve fitting procedure. The computed results for Comp-B, TNT, HMX, PBX-9404 and nitromethane, which are in good agreement with Lawrence Livermore National Laboratory (LLNL) data, are listed for comparison with other procedures in literature which have been in use so far.     

Evaluation of Detonation Energy from EXPLO5 Computer Code Results

The detonation energies of several high explosives are evaluated from the results of chemical-equilibrium computer code named EXPLO5. Two methods of the evaluation of detonation energy are applied: (a) direct evaluation from the internal energy of detonation products at the CJ point and the energy of shock compression of the detonation products, i.e. by equating the detonation energy and the heat of detonation, and (b) evaluation from the expansion isentrope of detonation products, applying the JWL model. These energies are compared to the energies computed from cylinder test derived JWL coefficients. It is found out that the detonation energies obtained directly from the energy of detonation products at the CJ point are uniformly to high (0.9445±0.577 kJ/cm³), while the detonation energies evaluated from the expansion isentrope, are in a considerable agreement (0.2072±0.396 kJ/cm³) with the energies calculated from cylinder test derived JWL coefficients.     

Numerical simulation of detonation initiation in a contoured tube

The effect of the wall contours in an axisymmetric tube on the transition from the shock wave to the detonation wave is studied numerically. Qualitative features and quantitative characteristics of the detonation initiation mechanism realized in a tube with a parabolic segment of the wall contour and conical expansion are found. The calculated results are presented in the form of “detonation curves” (angle of inclination of the contoured segment versus the Mach number of the initial shock wave) for various levels of tube blockage ratio.     

Continuous spin detonation of a coal-air mixture in a flow-type plane-radial combustor

Regimes of continuous spin detonation of coal particles in an air flow in a flow-type plane-radial combustor 500 mm in diameter are studied. The tested substance is fine-grained cannel coal from Kuzbass having a particle size of 1–7 µm and containing 24.7% of volatiles, 14.2% of ashes, and 5.1% of moisture. A certain amount of hydrogen is added for coal transportation into the combustor and promotion of the chemical reaction on the surface of solid particles. To reduce air pressure losses in channels connecting the manifold and the combustor, their cross section is increased to limiting values (25 cm²), whereas the combustor exit diameter is reduced. The angle of the air flow direction and the combustor geometry are also varied. The minimum pressure difference in the air injection channels (16%) is reached with stability of continuous spin detonation in the combustor being retained. The domain of continuous spin detonation regimes in the coordinates of the fuel flow rate and specific flow rate of the mixture is constructed. The results of studying detonation burning of solid fuels can find applications in power engineering, chemical industry, and environmental science, in particular, contamination by combustion products.     

Initiation of detonation of fuel-air mixtures in a flow-type annular combustor

Initiation of detonation in a fuel-air mixture flow formed in an annular cylindrical combustor 306 mm in diameter is studied. The source of detonation initiation is the detonation wave entering the annular channel from a plane-radial vortex chamber, a jet of products, or a low-power heat pulse. It is demonstrated that continuous spin detonation (CSD) can be ensured by all these methods. Its formation is accompanied by a transitional process with a duration up to 10 ms, which is associated with violation of injection of the species (initiation by the detonation wave) or with the time of evolution of tangential instability in CSD (jet or spark initiation). Transfer of detonation to a flow of fuel-air mixtures with low chemical activity (propane-air, methane-air, kerosene-air, and gasoline-air mixtures) by the initiating detonation wave formed within fractions of a millisecond by a low-energy pulse or as a result of self-ignition of the hydrogen-air mixture in the plane-radial vortex chamber is realized. It is found that organization of CSD in these mixtures requires combustors with greater (than 306 mm) diameters. A possibility of CSD in kerosene-air and gasoline-air mixtures with low chemical activity by means of air enrichment by oxygen ahead of the combustor entrance is demonstrated.     

Detonation of Secondary Explosives in a Vacuum Suspension

The existence of self–sustaining detonation in an evacuated suspension of the particles of a secondary explosive is shown experimentally. The experiments with HMX were performed in a vertical shock tube of diameter 0.07 m and length 7 m in the range of volume–average particle concentrations 0.32—0.9 kg/m³. It is shown that the vacuum–detonation velocity does not almost depend on the volume–average concentration of particles and it is (1750±50) m/sec and that the pressure profile of a vacuum–detonation wave is smooth. The data on the electric conductivity of vacuum–detonation products and the length of the reaction zone are given.     

Axisymmetric expanding heterogeneous detonation in gas suspensions of aluminum particles

A problem of expansion of heterogeneous detonation in a suspension of aluminum particles in gaseous oxygen from a circular tube and its propagation in a semi-bounded or unbounded space is studied by numerical methods. The effects of the particle diameter in monodisperse suspensions and of the composition of bidisperse suspensions on detonation propagation regimes are studied. The calculated results are compared with data on heterogeneous detonation of gas suspensions in a plane channel and on gas detonation. The critical values of the channel width and the tube diameter are found to differ by a factor of 2–2.5, as it is also observed in gas detonation. However, the ratio of the critical diameter to the detonation cell size in the case of heterogeneous detonation can be smaller than that in gas mixtures by an order of magnitude.     

Relationship between brisance of explosives and their molecular-atomic structures

The explosives with various molecular-atomic structures substantially differ by their detonation velocities and brisance but often are similar by the expansion of their detonation products (DP's) which mainly consist of the same molecules. Such explosives referred to as “usual” show the relationship between ϱD and brisance determined by different methods. There are linear correlation relations between the results obtained. This relationship is not observed with the “unusual” explosives which differ from the “usual” ones by the chemistry of detonation processes. These explosives include liquid explosives, explosive-oxidants. CNO- and HNO-explosives and also CHNOF-explosives. Their calculation of thc detonation parameters and brisance from the same criterions which characterize the chemical composition of the explosives and the detonation products, results in some errors. Taking these differences into account it is possible in some cases markedly to increase the accuracy of the detonation parameters. As an example is the calculation of the detonation pressure to within 3% based on the linear correlation relation between the pressure (P_J) and the relative detonation impulse (I_rel) which characterizes the charge ability to do work at the initial stages of thc expansion of the detonation products: The relative impulse, in its turn, may be calculated both for “usual” and “unusual” explosives from the atomic composition of an explosive, its density and the enthalpy of the formation with the error that does not exceed the experimental (2%).     

Problem of detonation suppression by means of blankets and foams

The subject of investigation was the effect of an injection of water vapor on the detonation of fuel-air mixtures. It is shown that the injection of mass into the detonation wave reaction zone leads to a lowering of the velocity and to a disruption of detonation. The possibility of a suppression of detonation with moderate water-mechanical foams density was investigated experimentally.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 116–124, November–December, 1991.     

Detonation combustion of a hydrogen–oxygen mixture in a plane–radial combustor with exhaustion toward the center

Regimes of continuous spin detonation in a plane–radial combustor with an external diameter of 80 mm with peripheral injection of a hydrogen–oxygen mixture in the range of specific flow rates of the mixture 3.6–37.9 kg/(s ·m²) are obtained for the first time. Depending on the diameter of the exit orifice in the combustor (40, 30, or 20 mm), specific flow rate of the mixture, its composition, and counterpressure, one to seven transverse detonation waves with a frequency from 6 to 60 kHz are observed. It is found that the number of detonation waves increases, while their intensity decreases owing to reduction of the exit orifice diameter or to an increase in the counterpressure. The flow structure in the region of detonation waves is analyzed. The domain of detonation regimes in the coordinates of the fuel-to-air equivalence ratio and specific flow rate of the mixture is constructed. A physicomathematical model of continuous spin detonation in a plane–radial combustor is formulated. For parameters of hydrogen and oxygen injection into the combustor identical to experimental conditions, the present simulations predict similar parameters of detonation waves, in particular, the number of waves over the combustor circumference and the wave velocity.     

多孔材料对氢气爆轰的抑制作用

为了研究多孔材料对氢气爆轰的抑制作用,在内径80 mm、长6000 mm的爆轰圆管中开展2H₂+O₂+3Ar预混气爆轰传播实验。在距点火头5000 mm处放置不同孔隙密度(10、20、40 ppi)厚度30 mm的Al₂O₃泡沫陶瓷和不同厚度(10、30、50 mm)孔隙密度20 ppi的泡沫铁镍金属,分别使用压力传感器、烟膜记录爆轰波压力、胞格结构,计算爆轰波传播速度。结果表明,速度亏损和胞格尺寸随着孔隙密度或厚度的增加而增大,但是均与初始压力成反比。两种多孔材料的材料特性不同,泡沫铁镍金属具有良好的导热性,因此对爆轰波的抑制效果强于Al₂O₃泡沫陶瓷。     

双层药型罩射流形成的理论建模与分析

为了研究爆轰产物作用下双层药型罩的射流形成过程,应用PER理论拓展建立了双层药型罩成型装药点起爆时射流形成的分析模型.为获得爆轰波与双层药型罩的相互作用关系,通过数值模拟方法,得到了Defourneaux经验常数与爆轰波入射角的关系,并推导了双层药型罩当量密度公式.将射流形成的分析模型结果与数值模拟结果进行对比,验证了分析模型的合理性.使用分析模型研究了双层药型罩结构参数对射流形成的影响规律,为双层药型罩的结构设计提供了理论依据.     

A Discussion of the Kamlet‐Jacobs Formula for the Detonation Pressure

The main features of the Kamlet‐Jacobs formula for the detonation pressure of C H N O explosives are analytically derived from a BKW (Becker‐Kistiakowsky‐Wilson) equation of state of the detonation products. In the derivation, well‐known typical values at the Chapman‐Jouguet state, in particular the nearly constant value of the relative volume of the detonation products, are used.     

Calculation of Detonation Properties of Gaseous Explosives Using Generalized Reduced Gradient Nonlinear Optimization

In this paper, a study on the development of a numerical modeling of the detonation of C H N O‐based gaseous explosives is presented. In accordance with the numerical model, a FORTRAN computer code named GasPX has been developed to compute both the detonation point and the detonation properties on the basis of Chapman–Jouguet (C‐J) theory. The determination of the detonation properties in GasPX is performed in chemical equilibrium and steady‐state conditions. GasPX has two improvements over other thermodynamic equilibrium codes, which predict steady‐state detonation properties of gaseous explosives. First, GasPX employs a nonlinear optimization code based on Generalized Reduced Gradient (GRG) algorithm to compute the equilibrium composition of the detonation products. This optimization code provides a higher level of robustness of the solutions and global optimum determination efficiency. Second, GasPX can calculate the solid carbon formation in the products for gaseous explosives with high carbon content. Detonation properties such as detonation pressure, detonation temperature, detonation energy, mole fractions of species at the detonation point, etc. have been calculated by GasPX for many gaseous explosives. The comparison between the results from this study and those of CEA code by NASA and the experimental studies in the literature are in good agreement.     

Passage of a Bubble-Detonation Wave into a Liquid

The passage of a detonation wave from a chemically active bubble media into a chemically inert medium (liquid) is studied experimentally. The structure of the transmitted wave and the wave reflected from the butt-end of a shock tube (post-detonation waves) is investigated, and the pressures of these waves for different liquids are measured. The evolution of the post-detonation waves is traced, their velocities are measured, and the attenuation constants of these waves are determined. The energy-dissipation mechanisms for post-detonation waves in liquids are analyzed qualitatively.