Parameters Of Detonation Waves Research Articles

The interplay of casing material and detonation wave shock parameters in steel witness plate dent formation

This study uses both experimentation and simulation to investigate how varying casing material around cylindrical Composition-B charges affects witness plate response and diagnoses the cause of the differences in the dents produced. Through experimentation, it was found that consistent dents are produced from repeated tests and characteristically different dents are produced by charges with different casing material. Charges cased in viscoelastic materials produced shallower dents than those without casing. Simulation was validated against the experimental dents, and the detonation wave parameters were measured for 25 differently cased charges: 15 metals and 10 polymers. Regression fit relationships were derived relating dent parameters to casing density, casing impedance, casing tensile strength, detonation pressure, detonation velocity, impulse, and time of arrival. Specifically, it was found that the dent volume was negatively correlated with the detonation velocity and the impulse of the detonation wave was negatively correlated with dent depths across the charge. The density of the casing material was shown to be linked to the width of the witness dents. Additional dent tests were simulated for trinitrotoluene (TNT) charges cased in a single polymer and a single metal. The relationships derived for Composition-B were adjusted to fit TNT using TNT equivalency and calculated the measured detonation wave values to within 10% accuracy. Finally, it was concluded that the measurable distinctions observed in the witness dents were not a result of the casing material itself, but of the changes in the detonation wave caused by its interaction with the casing material.

Анализ параметров ударных волн на стенке взрывной полости при преломлении детонационных волн через воздушную и водную среду

Анализ параметров ударных волн на стенке взрывной полости при преломлении детонационных волн через воздушную и водную среду

Effect of Combustor Outlet Geometry on Operating Characteristics of Disk-Shaped Rotating Detonation Engine

A disk-shaped rotating detonation engine with H2/air mixture was tested to identify the impact of combustor outlet geometry on the engine’s operating characteristics. Three combustor outlet diameters and five outlet lengths are employed in the experiments. Results show that with the increase of combustor convergent ratio, the propagation stability of the rotating detonation wave decreases, and the propagation velocity and pressure peak decrease slightly. When the convergent ratio increases to a certain value (1.70 in this study), a “platform zone” with a lower pressure value appears before the sharp rise of the dynamic pressure curve. The propagation mode varies with the increase of mass flow rate at different convergent ratios. As the mass flow rate increases, the wave head number in the combustor increases. But the change rule of propagation mode with mass flow rate is greatly affected by convergent ratio. Increasing the convergent ratio is conducive to the formation of multi-wave modes, and the critical mass flow rate for mode transition drops sharply. When the convergent ratio increases to 1.70, the unstable asymmetric dual-wave mode is obtained. With the increase in the convergent ratio, the engine’s operating range and operating stability decrease significantly. Finally, changing the combustor outlet length has little influence on the engine’s operating characteristics and detonation-wave parameters.

The Algorithm and Computer Code for Predicting Detonation Wave Parameters of Aluminized Explosives

In this work, the algorithm and computer code, named DETO, used to calculate the detonation wave parameters (i.e., the velocity of detonation and the detonation pressure) of aluminized explosives, based on the chemical equilibrium theory of detonation products, the hydrodynamic theory of detonation process, and the Becker - Kistiakowsky - Wilson (BKW) equation of state. The aluminum (Al) content reacting with detonation products on the detonation wavefront can be changed according to the user's assumptions. Compared to experimental data for several aluminized explosive types, the results calculated by DETO have the same, even higher accuracy than those calculated by other computer codes previously published. Specifically, the mean absolute deviation from experimental data is about 2% for the velocity of detonation (VOD) and about 8% for the pressure on the detonation wavefront. In addition, the study also confirmed that about 50% of Al powders participate in the reaction on the detonation wavefront.

Effects of ignition condition on the initiation characteristics of rotating detonation wave in plane-radial structure

The ignition experiments of the plane-radial rotating detonation engine have been tested to identify the impact of ignition methods and ignition positions on the initiation characteristics of rotating detonation wave. The low-energy spark plug, high-energy spark plug and H2/O2 pre-detonation tube are used to ignite the engine. Results show that, for different ignition methods, the initiation process undergoes five stages: ignition, disordered deflagration, circumferential flame-wave propagation, unstable rotating detonation and stable rotating detonation. As the ignition energy increases, the circumferential flame wave is more easily obtained in combustor, and the initiation time of rotating detonation wave is shortened with better consistency. In this paper, the shortest initiation time is obtained by the H2/O2 pre-detonation tube. For the low-energy spark plug, as the mass flow rate increases, the average initiation time shows a downward trend with local fluctuation. When the rotating detonation engine is ignited close to the injection surface, the initiation time is shortened and fluctuates more slightly, and the optimal ignition position is obtained in the plane-radial combustor. Under specific operating conditions, changing the ignition position may affect the propagation mode of rotating detonation wave in the initial stage, and igniting close to the combustor center is more likely to obtain the multi-head rotating detonation wave. But changing the ignition method or ignition position has little effect on the propagation process and detonation-wave parameters in stable stage.

Parameters of Continuous Detonation of Methane/Hydrogen–Air Mixtures with Addition of Air to Combustion Products

Results of experimental investigations in a flow-type annular cylindrical combustor with an outer diameter of 503 mm are reported. The influence of air addition to products of continuous spin detonation of CH4/ $$m$$ H2–air mixtures on the parameters of detonation waves, the pressure in the combustor, and the specific impulse is considered. It is demonstrated that air injection into detonation products increases the velocity of continuous spin detonation, the pressure in the combustor, and the thrust, whereas the specific flow rate of the fuel decreases.

Effect of Inert Micro- and Nanoparticles on the Parameters of Detonation Waves in Silane/Hydrogen–Air Mixtures

Physicomathematical modeling of interaction of detonation waves in silane/hydrogen composite mixtures with clouds of inert micro- and nanoparticles ranging from 10 nm to 100 µm is performed. The normalized detonation velocity is calculated as a function of the volume concentration of particles. It is found that the efficiency of detonation suppression increases only as the particle diameter decreases to 1 µm. The influence of the thermodynamic parameters of particles on the detonation suppression efficiency is identified. The concentration limits of detonation are determined. It is demonstrated that a certain equilibrium asymptotic level of the concentration limits of detonation is reached as the particle diameter decreases below 1 µm. An approximation of the concentration limits of detonation is obtained in the form of an analytical dependence of the limiting volume concentration of particles on their diameter and fuel concentration in a composite two-fuel mixture of silane, hydrogen, and air.

Столкновение детонационных волн в пузырьковых средах

AbstractThe oncoming collisions of detonation waves, generated in bubbly media, is studied in the present paper while determining the critical conditions of collisions initiated in bubbly media, as well as the structure and parameters of detonation waves. The structure and properties of post-detonation waves, which are wave perturbations arising upon collisions of bubbly detonation waves, are also examined.

Effects of the pore size on hydrogen–air detonation propagation in the channel with porous walls

We considered the problem of detonation suppression and weakening of the blast wave effects occurring during the combustion of hydrogen–air mixtures in the confined spaces. Detonation decay in hydrogen–air mixture was experimentally investigated in rectangular cross-section channels with four types of foam polyurethane with a number of pores per inch ranging from 10 to 80. Shock wave pressure dynamics inside the section with porous coating were studied using pressure sensors. For all mixtures, the detonation wave was formed before entering the section with porous coating. The number of pores per inch was found to significantly affect the detonation wave parameters. Non-monotonic evolution of the shock wave pressure and velocity was discovered while using porous materials with bigger pores. By the end of the porous section, the shock wave pressure in porous material with 10 pores per inch was 100% higher compared to polyurethane with 80 pores per inch. The evolution of the shock wave pressure and velocity along the porous section for different types of porous material is presented.

ОБОБЩЕННАЯ КИНЕТИКА ДЕТОНАЦИОННОГО СГОРАНИЯ ГАЗООБРАЗНЫХ УГЛЕВОДОРОДОВ

A two-step generalized model of chemical kinetics of detonation combustion of propylene is presented. The model is consistent with the second law of thermodynamics and Le Chatelier’s principle. Constants of the models have a clear physical meaning. Owing to the simplicity (it includes only one ordinary differential equation) and high accuracy, the model can be used in multi-dimensional numerical calculations of detonation wave parameters and multi-front cellular structure.

Continuous spin detonation of methane/hydrogen-air mixtures with additional injection of air to combustion products

Results of experimental investigations in a flow-type annular cylindrical combustor with an outer diameter dc = 503 mm are reported. The influence of air addition to products of continuous spin detonation of a CH4 + 8H2 - air mixture on detonation wave parameters, pressures in the combustor, and specific impulse is studied. The range of existence of continuous spin detonation in terms of the specific flow rate of the mixture through the combustor cross section is extended to 1360 kg/(s·m2), whereas the equivalence ratio is reduced to φ∑ = 0.4. It is shown that addition of air to detonation products up to the level of the air flow rate in the main injection system increases the velocity of continuous spin detonation, pressure in the combustor, and thrust, whereas the specific flow rate of the fuel decreases.

Мартенситное превращение как аналог детонационного процесса

The paper deals with the wave model of an austenite to martensite transformation in steel, which is an analogue of a shock-wave process like detonation where a wave of transformation of austenite to martensite steel propagates along a steel beam. In Kashchenko’s monograph a wave model has been developed according to which, at least within individual austenite grains, this transformation takes place in the form of waves moving at a supersonic speed. In the present work, according to our estimates, the known criterium of detonation capacity is fulfilled in the process of austenite to martensite tranfromation. Under normal conditions, austenite density equals ρa = 8000 kg/m3 and martensite density ρm = 7750 kg/m3, therefore the transformation of austenite to martensite at constant pressure P = 0.1 MPa and temperature T = 300 K results in an increase of the volume of steel. This releases a latent heat Q(P,T) = 82000 J/kg. Therefore, based on these data one can conclude that if this transformation is implemented in a large steel beam, it would take the form of detonation, that is, a motion at a supersonic velocity of a physical-chemical transformation wave, in this case in the form of a wave of phase transition from austenite to martensite. Parameters of such a process for different ratios between the masses of the austenite and martensite steel in the original beam are estimated. The results of theoretical calculations of the parameters of detonation waves in steel at different weight ratios between austenite and martensite steel in the original beam are presented.

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.

Effect of combustor geometry on continuous spin detonation in syngas–air mixtures

Regimes of continuous detonation burning of syngas–air mixtures in transverse (spinning) detonation waves in a flow-type annular cylindrical combustor are considered. Mixtures of carbon oxide and hydrogen in proportions of 1/1, 1/2, and 1/3 are used. The varied parameters are the combustor geometry and the fuel injection system, as well as the flow rates of air and syngas. The influence of additional supply of air to the products on the detonation wave parameters, pressure in the combustor, and specific impulse is determined. The range of realization of continuous spin detonation of the syngas–air mixture in terms of specific flow rates of the mixture is expanded from 25 to 786 kg/(s ·m2). It is shown that additional supply of air increases the pressure in the combustor, the thrust, and the number of detonation waves, but decreases the detonation wave velocity. The flow structure in the domain of detonation waves is studied. For some values of the combustor expansion coefficient, a chart of detonation regimes in the coordinates of the fuel-to-air equivalence ratio and specific flow rate of air is constructed, and the specific impulse of the thrust force is calculated.

不同岩性条件下孔壁爆炸载荷及透射波比能量计算

为研究不同激发岩性对孔壁爆炸载荷及透射波比能量的影响，基于经典的冲击波理论，建立了岩石介质中柱状装药爆炸时孔壁的初始冲击载荷计算模型，该模型将爆轰波简化为含化学反应的强间断面，弥补了弹性波理论认为孔壁周围岩石内直接产生应力波的不足，成功解释了爆轰波参数的基本关系式；建立了不同激发岩性时柱状装药爆炸的孔壁质点速度和压力随时间变化的计算模型，编程计算得到其随时间变化的函数关系式和透射波比能量的解析解。 To study the impact of explosion load and transmission wave specific energy under the different excitation lithology, based on the classical shock wave theory, the calculation model of initial ex-plosive loading parameters of blasting hole was established, when blasting in columnar charge. The detonation waves were simplified to discontinuous surfaces which contain chemical reactions in the calculation model. It made up the weakness of the elastic wave theory which thought stress wave was produced directly in the wall of blast hole. The basic relationship of the detonation wave parameters was explained successfully. Based on the elastic wave theory, the calculation methods of the velocity and press of blasting hole particle when columnar charge blasting was established for different excitation lithology. The functional relationships and the analytical solutions of the transmitted wave specific energy were got by program.

Detonation performance of high-dense BTF charges

New experimental data on detonation wave parameters and explosive performance for benzotrifuroxan are presented. Optical pyrometry was applied in order to measure the temperature and pressure of BTF detonation products. Chapman-Jouguet temperature was obtained as 3990 – 4170 K (charge densities 1.82 – 1.84 g/cc). The heat of explosion and the acceleration ability were measured also. It is also considered the hypothesis of formation of nanodiamond particles in detonation products directly behind the detonation front and influence of these processes on the temperature-time history in detonation products.

Detonation Wave Parameters in a Variable Cross Section Channel in Gas Mixture of Methane with Oxygen and Nitrogen

Detonation Wave Parameters in a Variable Cross Section Channel in Gas Mixture of Methane with Oxygen and Nitrogen

On some conditions for detonation initiation downstream of a perforated plate

An experimental study is presented of the influence of detonation wave parameters and detonation product composition upstream of a perforated plate on the onset of detonation downstream. Experiments were performed in detonation tube 106 mm in diameter, separated into two sections by a perforated plate combined with a diaphragm. The tube was equipped with pressure sensors and a semi-cylindrical smoked foil. Hydrogen–air mixtures with different hydrogen concentrations were used upstream and downstream of the perforated plate. It is shown for mixtures containing 25 and 34 % of hydrogen in air that the onset of detonation downstream depends on detonation parameters upstream of the perforated plate. An increase in the initial pressure upstream of the plate leads to detonation initiation immediately downstream. The variation of mixture composition upstream of a perforated plate does not affect on detonation initiation downstream under the present experimental conditions.

Determination of chemical reaction zone parameters, neumann peak parameters, and the state in the Chapman-Jouguet plane in homogeneous and heterogeneous high explosives

Parameters of detonation waves in homogeneous and heterogeneous high explosives are registered. Dependences of the duration of the chemical reaction zone on the critical diameter are obtained. The transition from a stable to an unstable detonation mode in liquid explosives is studied. In these studies, the regime of normal detonation with a stretched shock wave is observed, and the induction period of the thermal explosion is determined.

Dynamics of the detonation-wave front in solid explosives

The important role of the shape of the front during detonation wave propagation in gas mixtures was substantiated by K. I. Shchelkin during construction of the theory of spinning detonation. Subsequently, a unique relationship between the curvature of the front and detonation wave parameters has been repeatedly confirmed in experiments, including for condensed high explosives (HEs). The existence of this relationship formed the basis of the theory of the dynamics of the detonation front which had been developed by the end of the 20th century. This paper presents the results of a study of detonation front propagation in cylindrical samples of a low-sensitivity HE of different diameters with one-point and plane-wave initiation. A unique relationship between the detonation velocity and the curvature of the detonation wave front has been found. Ordinary differential equations describing two-dimensional steady-state detonation front profiles for HE charges in the form of a plate, a cylinder, and a ring were derived assuming that the detonation velocity depends on the curvature of the front. It was taken into account that the boundary angle between the normal to the front and the HE edge is unique for each combination of HE and liner material. It was found that the same detonation front profile corresponds to several combinations of liner material and the determining size of the charge (plate thickness, radius of the cylinder or the inner radius of the ring). A comparison of experimental front profiles near the edges of HE charges for these combinations provides data on the dependence of detonation velocity on the curvature of the front at low velocities corresponding to shock-induced detonation regimes. Analysis of previously obtained data for detonating ring charges of low-sensitivity HEs shows that as the detonation velocity decreases, the total front curvature tends to a limit of about 0.05 mm−1, i.e., of the order of the inverse critical diameter. The limit of the front curvature allows predicting the critical detonation diameter.