Detonation Process Research Articles

Numerical study on flow and combustion properties of oblique detonation engine in a wide speed range

Ensuring safe flight is a fundamental prerequisite for developing hypersonic propulsion systems. A comprehensive investigation of the steady boundary associated with oblique detonation wave in a wide speed range was conducted, with the aim of exploring the feasibility of oblique detonation engine across a diverse array of flight conditions. In this study, the wedge angle applicable in a wide-speed range was acquired via the analysis of oblique detonation wave polar curve. The configuration of the internal injection oblique detonation engine was subsequently designed and established, considering the effect of fuel-air inhomogeneity and complex wave system interactions within a confined combustor. The compressible Euler equations coupled with a 9-species and 19-step chemical reaction mechanism are employed to simulate the oblique detonation process. Ultimately, the safe flight envelope of an air-breathing vehicle equipped with the internal injection oblique detonation engine is mapped across a broad range of Mach numbers, demonstrating the engine’s capability to operate within the Mach 8 to 12 range. Furthermore, the findings reveal that decreasing either the flight Mach number or altitude results in unsteady oblique detonation wave within the internal injection oblique detonation engine combustor, however, reducing the equivalence ratio can stabilize the oblique detonation wave once again. This study provides valuable guidance for the design and wide-speed-range operation of an internal injection oblique detonation engine.

Study on concentration distribution and detonation characteristics of typical multiphase fuel in orthogonal flow field

The fuel concentration distribution and detonation characteristics are important for performance evaluation. In order to meet the needs of airdrop, launcher and missile, the transient flow and detonation process of multiphase fuel in orthogonal flow field are analyzed by experiments and numerical simulations. The dynamic detonation model of ethyl ether (EE), propylene oxide (PO) and tetrahydro dicyclopentadiene (JP-10) is built. The flow process, concentration distribution, overpressure, temperature and detonation wave structure of the three fuels are obtained. The results show that the falling velocity has obvious influence on the detonation process of fuel droplets. The falling velocity of 0.5 Ma makes the fuel concentration distribution more uniform and the energy output is better. The peak overpressure of EE, PO and JP-10 is 2.88 MPa, 3.21 MPa and 2.96 MPa respectively. The peak temperature is 2885 K, 3230 K and 2955 K respectively. The burn out rate increases by 8.5%, 8.1% and 13.7% respectively. JP-10 has higher sensitivity to falling velocity, and there are obvious secondary peaks of overpressure in low-speed state. PO has higher stability for falling velocity, and the scaled length of high temperature/pressure after detonation wave is 0.145 m·kg-1/3.

Deflagration-to-detonation transition and detonation propagation in supersonic flows with hydrogen injection and downstream ignition

This study investigates the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in supersonic flows using transverse hydrogen injection and downstream ignition. Utilizing the graphics processing unit accelerated adaptive mesh refinement approach, we examine the influence of downstream ignition jet pressure on DDT through high-resolution computational simulations. Our results indicate that the transverse injection of hydrogen into the supersonic mainstream generates strong turbulence and numerous vortices due to Kelvin–Helmholtz instability, enhancing fuel mixing efficiency along the flow but deviating from the ideal premixed state. Following the injection of the downstream ignition jet into the supersonic main flow, initial flame acceleration is less effective than in the premixed state due to the non-uniformity of the incoming flow. However, within the boundary layer, the flame remains stable, and the intense turbulence fosters shock–flame interactions. The convergence of multiple compression waves into a shock wave facilitates energy deposition, coupling with the flame to trigger local detonation via the reactive gradient mechanism. The detonation wave exhibits complex wavefront structures, including vertical and oblique fronts induced by boundary layer interactions. Ignition jet pressure significantly impacts the DDT process and detonation wave characteristics, reducing ignition time and affecting the detonation temperature, pressure, and propagation speed. This study provides valuable insights into the dynamics of flame acceleration and DDT in supersonic flows with non-uniform fuel distribution and downstream jet ignition. The findings highlight the critical role of ignition jet pressure in optimizing ignition and detonation processes, offering new perspectives for achieving low-energy, rapid detonation initiation within the tube.

Study on CL-20 Initiated by Flyer Driven by Copper Azide

Abstract A simulation model of copper azide microcharge driving flyer initiation microscale CL-20 explosive was established, and the action process of copper azide detonation driven flyer initiation microscale CL-20 explosive was numerically simulated by ANSYS/LS-DYNA fluid-structure interaction algorithm. The internal pressure and velocity changes of the flyer during the detonation of copper azide and the internal pressure change of the CL-20 explosive during the detonation were studied. The results show that the error between the experimental and numerical simulation results of the average speed of the flyer is within 10%. This provides a feasible solution for the study of the micro-explosion detonation mechanism by simultaneously analyzing the explosion process of the multi-physical field change law. The numerical simulation results are consistent with the experimental results, indicating that the established simulation model can be used to simulate the detonation process of CL-20 initiated by a flyer driven by copper azide. The copper azide charge, with a diameter of 1 mm and a charge thickness of 0.6 mm, successfully initiates the detonation of the CL-20 explosive.

Simulation of Exploding Foil Initiator Flyers Driving Detonation

Abstract Flyers are the key components that determine the detonation ability of Exploding Foil Initiators (EFI). The incident attitude and velocity of the flyer are the decisive factors affecting the initiation of explosives. This work utilizes a new simulation method to simulate the impact detonation process of flyers. Here we simulate the process of flyers being cut and accelerated, impacting explosives and explosives being detonated. It is possible to obtain the orientation and dynamic velocity changes of the flyer during its motion and the propagation process of detonation waves in explosives. The results provide detailed flyer morphology during the operation of the EFI and pressure changes in explosives. The results indicate that during the formation process of 10 μm and 20 μm flyers, the flip will occur. Additionally, 20 μm and 25 μm flyers can detonate HNS-IV, while 10 μm and 30 μm flyers can not detonate HNS-IV.

The effect of spatial non-uniformity on multiple transient modes of detonation onset in a three-dimensional channel

The study of the transient combustion modes is one of the key topics when considering the safety of space flights. Control of detonation onset has a dual application. First, the search for ways to prevent detonation modes in case of accidental fuel releases for fire safety issues of launch systems and the avoidance of accidents with rocket engines at a launch site and in near-Earth space. Second, the study of detonation and the possibility of using it to create propulsion systems based on detonation combustion of fuel. The paper shows the effect of the presence of spatial non-uniformities on the promotion of detonation in the chamber. Various geometries with and without obstacles and cavities are considered. It is demonstrated that the presence of obstacles accelerates the transition to the detonation process on the one hand, but on the other hand the presence of obstacles in combustion chamber could be the cause of incidental uncontrolled ignition, which ruins stable operation of an engine. The results of theoretical studies of the working cycle of the combustion chamber of a pulsed detonation engine are presented. Theoretical estimates for thrust characteristics are obtained.

Pressure Characteristics and Secondary Ignition Effects of Gas Produced in RDE Using Lignite and Anthracite/CH4 Fuel.

This study aims to address the energy efficiency release and environmental impact of coal dust in rotating detonation engines (RDEs) by monitoring the detonation characteristics of lignite and anthracite in methane gas-solid mixtures using high-precision sensor technology. Experimental results indicate that the peak detonation pressure of anthracite is 1.4% higher than that of lignite, and its detonation wave propagation speed is at least 5.5% faster, suggesting that anthracite exhibits more stable and efficient fuel energy release characteristics during detonation. Additionally, the sensor technology enabled detailed recording of pressure fluctuations and gas composition changes during the detonation process, providing accurate data for assessing and controlling emissions of harmful gases such as carbon monoxide and carbon dioxide. These data are crucial for designing more efficient and environmentally friendly coal dust detonation systems, enhancing mine safety and environmental protection. The outcomes of this research not only advance technological progress in the field of energy science but also address efficiency and environmental issues in industrial applications, offering significant support for achieving safer and more sustainable energy production methods.

Many-Body Expansion-Based Quantum Mechanical Force Field for Cyclotrimethylene Trinitramine under High Pressure.

RDX undergoes pressures of approximately 30-50 GPa during detonation, leading to significant changes in intermolecular interactions. Accurately describing these interactions is crucial for understanding the energy transfer in the detonation process. To address this, this work introduces a many-body expansion-based quantum mechanical force field (MB-QMFF) to accurately describe RDX's intermolecular interactions under high pressures. Using MB-QMFF, we evaluated various density functionals and found that the M062X functional with GD3 dispersion correction provided the highest accuracy. Regarding intermolecular forces, two-body interactions were the most significant, with three-body interactions being negligible. Additionally, we investigated intermolecular energy variations at different densities (or pressures). The results clearly demonstrate an accurate description of intermolecular interactions by the MB-QMFF scheme. Therefore, we believe that the MB-QMFF scheme can serve as a foundation for the development of RDX-specific force fields and pave the way for future studies on the detonation process of RDX.

Experimental study on the evolution of shock waves in the near field of cylindrical charge explosion

Cylindrical charges are frequently used in blasting engineering and military operations, often detonated very close to target structures. Obtaining the characteristics of the flow field distribution in the near field of explosions through experimentation consistently poses challenges. These challenges constrain efforts to elucidate the evolutionary processes of explosive shock waves. Employing the explosive schlieren experimental system yields a clearer depiction of the near field flow than previous studies, thereby facilitating a more comprehensive understanding of the characteristics of cylindrical charge explosions. The overall flow field adopts a droplet shape, with the interface of the detonation products and the shock wave front forming continuous concave shapes. The detonation process in cylindrical charges can be conceptualized as the detonation wave propelling the detonation products at supersonic speeds. The formation of explosive shock waves can be elucidated through the dynamics of oblique shock waves generated by two-dimensional curved surfaces. This mechanism influences the relationship between the deflection angles of detonation products and the shock wave angles resulting from different detonation velocities. Theoretical calculations of shock wave positions align with experimental images. Significant variations in shock wave velocities at different positions within cylindrical charges are observed, identifying patterns of these variations. The research findings clarify the formation mechanisms of explosive shock waves in cylindrical charges and deepen the understanding of shock wave evolution in the near field.

Probabilistic analysis of near-field blast loads considering fireball surface instabilities and stochastic detonator location

High speed video analysis of near-field explosive detonations displays distinct stages of emergent hydrodynamic instabilities in the fireball/shock-air interface. Typically, beyond 10 charge radii, the instabilities experienced large growths giving rise to more chaotic behaviour of the interface and thus an increasing uncertainty in surface velocity. These surface instabilities are suggested as the primary cause of blast parameter variability in the near-field. However, as a deterministic tool, numerical simulation of the detonation process and subsequent blast wave propagation is not able to replicate the stochastic nature of fireball surface instabilities and hence near-field blast parameter variability. Therefore, it is necessary to develop new methods to simulate and characterise the stochastic features of the fireball/shock-air interface. This paper proposes an algorithm to generate an explosive charge element with random shape in finite element model in order to simulate irregularities in the fireball/shock-air interface, and therefore produce variabilities comparable to those from direct observation. The effect of chaotic fireball/shock-air interface on near-field loading is explored through a large number of numerical simulations in order to investigate the statistical distribution of parameters including peak overpressure and impulse. Subsequently, the effect of stochastic detonator location is explored in a similar manner. A computational procedure based on the Monte Carlo Method is proposed to establish a probabilistic model of near-field blast loads, termed PSL-Blast. The reliability of design blast loads calculated using the UFC 3-340-02 design manual is then estimated using PSL-Blast, which suggests that reliability decreases with decreasing scaled distance. Finally, reliability-based safety factors of blast loads are calculated based on different blast settings.

The diffraction and re-initiation characteristics of gaseous detonations with an irregular cellular structure

Two-dimensional numerical simulations were performed in this study to look at the diffraction and subsequent evolution of an irregular structure detonation in a stoichiometric hydrogen-air mixture, propagating from a small-width pre-detonator (width d) into a larger-width testing channel (width D). By varying the ratio D/d from 1.1 to 5.5, three kinds of propagation modes and the corresponding dynamics of the irregular structure detonation waves are elucidated. The numerical results show that, for an irregular structure detonation wave, the D/d range from 1.0 to 1.1 corresponds to the supercritical mode, the critical mode for D/d ranging from 1.2 to 5.0, and a D/d larger than 5.0 results in the subcritical mode. Compared to the equivalent numerical study for regular structure detonations, the critical width ratios for the supercritical mode and the critical mode are found different for irregular structure detonation. Detonation waves with an irregular structure are more likely to change from the supercritical mode to the critical mode. In the critical mode, the re-initiation process of an irregular structure detonation could originate in two ways, i.e., the Mach reflection of the diffracting lead shock LS to form the main triple point TP1 or self-sustained triple points (the TP2∼TP4) from the diffracting cellular detonation front. On the other hand, the re-initiation process of a regular structure detonation could result solely from the Mach reflection of the LS to form the TP1. By defining the distance between the backward-facing step and the explosion bubble HS formed by the collision of the new triple points as the characteristic distance L (mm), it is shown that the irregular structure detonation requires a longer characteristic distance L than the regular structure detonation to generate the HS at the centerline. The findings of this study offer potential avenues for optimizing pre-detonator and combustion chamber configurations in detonation engines.

VALIDATION OF THE MODEL OF HYBRID DETONATION OF HYDROGEN-AIR MIXTURES WITH ALUMINUM PARTICLES

Verification and validation of the model of the reduced kinetics of hybrid detonation in hydrogen-air mixtures with fine aluminum particles was carried out. The formula of integral heat release is obtained depending on the fuel excess coefficient for poor hydrogenair mixtures. The results are consistent with experimental data on the detonation rate. The constants of the aluminum combustion reactions are determined, which ensure the coordination of the detonation rate in air suspensions of aluminum particles. The processes of gas detonation in hydrogen-air mixtures and hybrid detonation with aluminum particles are numerically modeled. The dependencies of the hybrid detonation rate on the particle concentration are consistent with the known data. The comparison with experiments on cellular gas and hybrid detonation patterns is carried out: the degree of regularity, the size of the cells, the slope of the trajectories of triple points.

120 kHz mid-infrared TDLAS sensor for H2O concentration and temperature measurement in rotating detonation engine exhaust flows

Rotating detonation engines (RDEs) require advanced rapid combustion diagnostic techniques to better understand their complex detonation processes. A fast mid-infrared TDLAS sensor was proposed to simultaneously monitor H2O concentration and temperature at the outlet of an H2/air-fueled RDE annular combustor. An iterative parameter extraction method from transmitted laser intensity was proposed to extract the H2O concentration and temperature of the detonation waves. A measurement rate of 120 kHz enables high-speed and simultaneous quantification of detonation wave combustions. The results show that when RDE operates stably, the detonation frequency, average temperature, and average molar percentage of H2O concentration of the detonation waves are 4.631 kHz, 1572.8 K, and 0.335, respectively. The detonation frequency extracted from H2O concentration and temperature is highly consistent with that extracted from thermal radiation, and the relative frequency error is only 0.022 %. The time-resolved H2O concentration and temperature data measured by the sensor accurately capture the thermal dynamics of the transient detonation waves.

A novel configuration capable of enhancing flame acceleration and detonation

This study proposes a novel design concept that leverages the geometric effects of channels with varying diameters and bends to boost flame acceleration and detonation in microchannels. A quasi-direct numerical simulation with detailed chemical kinetics is used to evaluate the processes of flame acceleration and detonation. A comparative study on the impact of equidistant spiral and converging spiral shapes of detonation channels on flame acceleration is conducted and discussed. The results indicate that in the low-speed and high-speed stages of flame propagation, Fermat's spiral channel exhibits a more significant promoting effect on flame acceleration compared to the Archimedes spiral channel. Fermat's spiral channel has significant advantages in terms of combustion efficiency and can save about 30% of fuel during the detonation process. This study helps to further reduce the scale of the detonation system.

Real-time X-ray diffraction measurement on laser shock-loaded hexanitrostilbene (HNS)

Understanding the lattice evolution of hexanitrostilbene (HNS) is crucial for ensuring its safety and reliability under shock loading. However, the lack of in situ, real-time diagnostics has limited the availability of lattice parameters for shock-loaded explosives. In this study, we utilized dynamic X-ray diffraction technology to obtain the diffraction spectrum of laser shock-loaded HNS and to determine its temporal evolution. Additionally, by improving the laser energy, we initiated HNS and obtained the diffraction spectrum of detonation products during the detonation process. The experimental results showed the presence of a diamond structure in the detonation product, suggesting the existence of either diamond or diamond-like carbon. Our research not only elucidates the crystal structure of shock-loaded HNS and its detonation products but also provides an avenue for laboratory-scale investigations into dynamically loaded explosives, which furnishing an opportunity to unveil the underlying mechanism governing explosive dynamic response behavior.

ЧИСЕЛЬНЕ МОДЕЛЮВАННЯ ПРОЦЕСУ ВПЛИВУ ПРОДУКТІВ ДЕТОНАЦІЇ НА НАДЗВУКОВИЙ ПОТІК ПОВІТРЯ

Currently, there is a large number of control bodies used in modern rocket technol-ogy. Gasdynamic systems are usually used in rocket engines to change the thrust vector, less often - to create asymmetric air flow around the case. But the application of the det-onation process for such scheme can have better energy and dynamic characteristics compared to existing systems. The driving force in such scheme is created not only by the reactive mass force of detonation products ejected from the gas generator, but also by the effect of an intense shock wave on the pattern of supersonic flow around the rocket. Therefore, it is necessary to evaluate the performance and efficiency of the experiment. The purpose of the study is a priori numerical study of the detonation wave effect on the supersonic flow in the nozzle. Modeling was carried out in the Solid Works application software package. The geometric parameters of the model coincide with the experimental model. It is a flat nozzle, one of the walls is longer than the other and imitates the surface of the rocket. Air, accelerating in the nozzle to supersonic speeds with Mach number M=1.3...2, flows around this wall. Setting devices affecting the flow in it, it is possible to investigate their influence and the possibility of creating a lateral (controlling) force. When detonation is used to disturb the flow, an intense shock wave is generated in it, which changes the pres-sure distribution on the wall surface. Some holes for pressure sensors are made in the wall to fix this disturbance over time. A priori numerical modeling was carried out in order to estimate the parameters of the interaction of detonation products with the supersonic air flow. The pressure range and duration of the process have been determined, which allows selection of equipment and planning of the experiment. Patterns of velocity and pressure distribution in the model over time were obtained.

Experimental Study on Effects of Different Factors on Continuous Detonation of Superfine Lignite: Particle Size and Fuel Equivalent Ratio

ABSTRACT The Rotating Detonation Engine (RDE) is garnering attention for its high thermal cycle efficiency. In order to explore the detonation evolution of lignite/gas/oxygen gas-solid two-phase fuel in RDE, self-developed RDE(L:1000 mm) was used to study the detonation characteristics of lignite dust with ultra-fine particle size in methane/oxygen atmosphere, and the effects of ultra-fine particle size and equivalent ratio on detonation characteristics were explored, achieving stable propagation of rodtating detonation waves (RDW) with durations between 0.611 and 0.684s. The results indicate that the introduction of lignite dust significantly enhances the detonation effects compared to pure methane fuel. An increase in the overall equivalence ratio boosts the propagation velocity of RDW in methane-solid fuels, while a larger lignite dust particle size slows it down. Among ultrafine lignite powder sizes, a 1 μm particle size achieved the highest detonation wave speed. In terms of RDW propulsion, the impact of particle size and methane-solid fuel equivalence ratio on thrust mirrors their effect on detonation wave velocity. At a global equivalence ratio (GER) of 1.8, the specific impulse under different particle sizes was about 0.6 times that at a GER of 1.0, suggesting that an excess of fuel can reduce detonation effectiveness. The optimal specific impulse results were obtained with a lignite powder addition rate of 6 g/s, particle size of 1 μm, and GER of 1.0, reaching 4.6 kN·s·kg−1. The research results reveal the detonation process and detonation propagation law of lignite in methane/oxygen, especially for the future application of lignite in detonation energy release engineering.

Numerical simulation on the bomb case effects of non‐ideal aluminized explosive

AbstractThe detonation process of non‐ideal explosives is influenced by the casing of the bomb. Non‐ideal charges in the process of the explosion of live ammunition energy output mechanism and distribution ratio, the impact of the case on the explosion flow field, and other issues cannot be obtained through the existing theoretical analysis and testing techniques to obtain specific values. This paper establishes a “detonation+afterburning” energy output model to characterize the energy release characteristics of non‐ideal charges, using step‐by‐step numerical simulation of the near and middle, and far fields of the explosion, and verify simulation results through experiments, quantitative analysis the case of a type of earth penetrator on the normal particle size (4 μm) and two times the normal particle size (8 μm) of non‐ideal charges of aluminum powder explosion process. The results indicate that the presence of the casing enhances the energy output of aluminum powder with 4 μm by ≈5 %. When the particle size of aluminum powder is doubled, the maximum reaction rate and the peak of the shock wave are merely around 35 % and 75 %, respectively, compared to those of normal particle size. The detonation products, case fragments, and air constitute 49 %, 48 %, and 3 % of the overall explosion energy, respectively. The proportional equation of the conversion between the chemical energy of the explosion and the kinetic energy of the case fragments is obtained. These conclusions can provide data support for the design of non‐ideal charge warheads, lethality assessment, and establishment of engineering protection standards.

Nonlinear Approach to Jouguet Detonation in Perpendicular Magnetic Fields

The focus of this paper was Jouguet detonation in an ideal gas flow in a magnetic field. A modified Hugoniot detonation equation has been obtained, taking into account the influence of the magnetic field on the detonation process and the parameters of the detonation wave. It was shown that, under the influence of a magnetic field, combustion products move away from the detonation front at supersonic speed. As the magnetic field strength increases, the speed of the detonation products also increases. A dependence has been obtained that allows us to evaluate the influence of heat release on detonation parameters.

Вплив детонаційної хвилі на перерозширений надзвуковий потік газу в со-плі

This paper proposes to use the detonation process to solve the problem of controlling highly maneuverable flying vehicles. The goal of the work is to study a new way of the thrust vector control of a rocket engine using the effect of a detonation shock wave on the gas flow in the nozzle. It is known that the method of thrust vector control by gas injection into the supersonic nozzle area of a rocket engine features one of the lowest losses of specific momentum and a high response speed and produces a significant lateral force. However, for the current level of rocket technology, there is a need to improve these characteristics. Detonation is considered as a method to intensify processes that affect the main gas flow and produce a lateral force. Its features make it possible to develop a system for pulse trajectory correction. In order to study the features of such a system, experimental studies of the detonation wave effect on a supersonic nozzle flow were conducted. A nozzle model and a gas generator for initiating a detonation wave interacting with the main supersonic air flow were developed and made. In the course of experiments, the effect of separation of the main flow from the nozzle wall by the detonation wave during the nozzle operation in the overexpansion mode was revealed. The duration of this effect was much longer than that of the detonation product effect on the main air flow in the nozzle, thus allowing it to be used in the development of a new thrust vector control method. To better understand the experimental results, a numerical simulation of the detonation wave propagation in a supersonic flow was carried out for the test conditions. The simulation was carried out in a non-stationary 2D formulation using the Solid Works software package. The goal of the simulation was to estimate the flow structure and the value of the relative lateral force produced by the change of this structure during detonation product injection into the supersonic nozzle area. The time evolution of the pressure field was obtained. The relative lateral force produced by detonation product injection into the supersonic air flow in the nozzle was determined. The presented features and method of jet engine thrust vector control may be used in unmanned systems operating in a wide range of speeds.