Simulation Of Detonation Research Articles

Almost All Carbon/Oxygen White Dwarfs Can Host Double Detonations

Double detonations of sub-Chandrasekhar-mass white dwarfs (WDs) in unstably mass-transferring double WD binaries have become one of the leading contenders to explain most Type Ia supernovae. However, past theoretical studies of the explosion process have assumed relatively ad hoc initial conditions for the helium shells in which the double detonations begin. In this work, we construct realistic C/O WDs to use as the starting points for multidimensional double detonation simulations. We supplement these with simplified one-dimensional detonation calculations to gain a physical understanding of the conditions under which shell detonations can propagate successfully. We find that C/O WDs ≲1.0 M ⊙, which make up the majority of C/O WDs, are born with structures that can support double detonations. More massive C/O WDs require ∼10−3 M ⊙ of accretion before detonations can successfully propagate in their shells, but such accretion may be common in the double WD binaries that host massive WDs. Our findings strongly suggest that if the direct impact accretion stream reaches high enough temperatures and densities during mass transfer from one WD to another, the accreting WD will undergo a double detonation. Furthermore, if the companion is also a C/O WD ≲1.0 M ⊙, it will undergo its own double detonation when impacted by the ejecta from the first explosion. Exceptions to this outcome may explain the newly discovered class of hypervelocity supernova survivors.

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.

A dynamic droplet breakup model for Eulerian-Lagrangian simulation of liquid-fueled detonation

This study proposes a dynamic model to reflect the physical image of the droplet breakup process in two-phase detonation flows. This breakup model is implemented in a two-phase detonation solver developed based on an open-source computational fluid dynamic platform, OpenFOAM, and compared with three prevalent models (TAB, PilchErdman, and ReitzKH-RT model) under different droplet diameters (30–70 μm) in one- and two-dimensional detonation problems. The simulating results show that the present breakup model well predicts experimentally determined detonation parameters such as detonation velocities and post-wave temperature. In addition, the present model has the advantage of being free of the KH breakup time parameter, which the ReitzKH-RT model needs to fit the experimental data. The one-dimensional detonation simulations indicate that different breakup models slightly impact the detonation wave velocity because the droplet breakup process does not significantly affect the total heat release as long as it is sufficiently fast to sustain the detonation. However, the two-dimensional detonation simulations show that the breakup model and the droplet initial diameter significantly affect the detonation cell size due to the different droplet distributions predicted by various models. The breakup length, which is the distance from the shock wave to the location at which sufficiently small child droplets appear, affects the chemical reaction zone thickness and then the detonation cell size. A longer breakup length will result in a larger detonation cell size.

Sensitivity of Simulations of Double-detonation Type Ia Supernovae to Integration Methodology

We study the coupling of hydrodynamics and reactions in simulations of the double-detonation model for Type Ia supernovae. When assessing the convergence of simulations, the focus is usually on spatial resolution; however, the method of coupling the physics together as well as the tolerances used in integrating a reaction network also play an important role. In this paper, we explore how the choices made in both coupling and integrating the reaction portion of a simulation (operator/Strang splitting versus the simplified spectral deferred corrections method we introduced previously) influences the accuracy, efficiency, and nucleosynthesis of simulations of double detonations. We find no need to limit reaction rates or reduce the simulation time step to the reaction timescale. The entire simulation methodology used here is GPU-accelerated and made freely available as part of the Castro simulation code.

Semi-confined blast loading: experiments and simulations of internal detonations

AbstractFar-field blast loading has been studied extensively for decades. Close-in, confined, and semi-confined detonations less so, partly because it is difficult to obtain good experimental data. The increase in computational power in recent years has made it possible to conduct studies of this kind numerically, but the results of such simulations ultimately depend on experimental validation and verification. This work thus aims at using reliable experiments to validate and verify numerical models developed to represent blast loading in general. Test rigs consisting of massive steel cylinders with pressure sensors were used to measure the pressure profiles of semi-confined detonations with different charge sizes. The experimental data set was then used to assess numerical models appropriate for simulating blast loading. In general, the numerical results were in excellent agreement with the experimental data, in both qualitative and quantitative terms. These results may in turn be used to analyse structures exposed to internal blast loads, which constitutes the next phase of this research project.

Detonation structure in the presence of mixture stratification using reaction-resolved simulations

Many investigations of detonation-based combustors have identified reactant mixture inhomogeneity as having a leading-order impact on wave dynamics and combustion efficiency. To examine this phenomenon in a simplified context, an array of two- and three-dimensional channel detonation simulations are conducted in the present work. The reactant mixture consists of stratified fuel and air, wherein the randomly distributed equivalence ratio field features a characteristic stratification length scale. Detailed chemical kinetics are implemented in an adaptive mesh refinement solution framework where the region near the shock front is resolved with O(100) cells per representative ZND induction length. The results show that in comparison to baseline cases with uniform reactant mixtures, reactant stratification has a marked impact on the detonation structure. Increasing the stratification length scale increases the size and irregularity of the detonation cells, yielding larger variations in wave speed. Triple point collisions in fuel-rich regions lead to local wave speeds above the notional mean CJ speed, but wave passage through inert regions causes the local wave speed and strength to diminish. Conditional statistics show that increasing the stratification length scale increases the variance in pressure and temperature in the primary reaction zone, as well as the variance in heat release over a range of mixture conditions. In addition to the reactant mixture, the impact of the boundary condition behind the detonation is also investigated. The results show that an inflow boundary condition acts to over-drive the wave, leading to higher peak pressures, smaller detonation cells, and increased reactant consumption. On the other hand, cases with a wall behind the wave exhibit weaker waves with lower peak pressures and heat release rates, as well as greater variance in conditional quantities. Comparisons between complementary two- and three-dimensional simulations show reasonable qualitative agreement in wave structure, speed, and conditional statistics.Novelty and significance statement: The present work considers two- and three-dimensional simulations of detonations propagating through stratified reactant mixtures using detailed chemical kinetics with O(100) cells per representative ZND induction length. To the authors’ knowledge, it is the first study to analyze this type of configuration at this resolution and detail, as well as the first to compare two- and three-dimensional simulations of this configuration. The results have implications for the detonation wave behavior observed in practical propulsion and power-generating applications, such as rotating detonation engines.

Statistics of detonation confinement: 1D, 2D and 3D simulations in hydrogen–oxygen

Statistical analysis of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) detonation simulations is performed to understand the role of confinement on detonation frontal velocity and thermodynamic states. Simulations considered include a 2D wide channel (5 detonation cells across), a 2D narrow channel (1.5 cells across), a 3D square channel (10 cells around perimeter), and a 3D round tube (6 cells around perimeter), with identical mixture conditions of stoichiometric hydrogen–oxygen with 3000 parts per million by volume (PPMv) ozone at 300 K and 15 kPa. 1D and 2D simulations with the same mixture without ozone are also considered. All simulations solve the compressible Navier–Stokes equations with detailed chemistry and exhibit good agreement with macroscopic characteristics of experiments (e.g., cell size). Results show that the frontal velocity in 3D simulations is more irregular as compared to the 2D simulations, which are more irregular compared to the 1D simulations. The irregularity in frontal velocity leads to broader distributions of shock velocities and shock decay behavior. The 3D simulations also exhibit a wider and more extreme set of thermodynamic states as compared to the 2D simulations immediately behind the shock wave, within the induction zone, and throughout the rest of the domain. Increasing relative boundary losses leads to quantitative differences in both thermodynamic state and frontal velocity, consistent with 1D steady models of detonation with losses. The conclusions drawn in this work are not sensitive to numerical grid resolution.

Numerical investigation of detonation initiation in a modeled rotating detonation engine

In experimental studies, single-wave mode and two counter-rotating wave mode are often observed in rotating detonation combustors. To investigate the mechanism behind different propagation modes, high-resolution numerical simulations of two-dimensional detonation in hydrogen/air mixtures are conducted by solving the reactive Navier–Stokes equations with a detailed chemical mechanism. The numerical results show that the occurrence of the dual-wave detonation propagation mode is positively influenced by an increase in both the channel width and the initial pressure. The dual-wave modes are observed when increasing the channel width, and it is found that the dual-wave modes are caused by increasing the residual premixed gas height near the inner wall. When increasing the initial pressure, the initial peak detonation heat release increases, which leads to the increase in the hot spot intensity formed, and it is found that the dual-wave modes are mainly caused by the interactions between the initial detonation wave and the inner wall. However, the initial equivalent ratio appears to have a relatively minor impact on the detonation propagation mode due to a relatively narrow range variation of physical properties. The peak heat release rate exerts a greater influence on the change of the propagation mode than the induction time does through a wider range test on rotating detonation engines' working condition. Moreover, the velocities and the cell sizes of detonation waves propagating in different directions with different channel widths are also analyzed, revealing that the characteristics of the detonation waves propagating in different directions are nearly the same.

Unsteady conjugate heat transfer simulation of wall heat loads for rotating detonation combustor

Rotating detonation engines (RDEs) are the most promising pressure-gain combustion devices, but their long-duration operations are hindered by the harsh thermal environment inside the chamber. This study analyzes the instantaneous and average heat loads on chamber walls of RDEs based on the newly developed unsteady conjugate heat transfer (CHT) OpenFOAM solver named multiRegionBYRFoam. To enhance accuracy in predicting heat transfer characteristics compared to decoupled simulations focusing solely on fluid or solid behavior, three-dimensional CHT simulations are conducted for a premixed H2/air annular RDE coupling the detonation simulation with heat conduction in both inner and outer chamber walls. The transient time evolutions of wall heat flux in RDEs are numerically captured for the first time and agree well with experiments. The calculated peak wall heat flux is 1.98 MW/m2 at the inner wall and 2.63 MW/m2 at the outer wall when a single detonation wave propagates with a mass flow rate of 0.227 kg/s. By investigating the influence of inlet flow conditions and detonation modes, valuable guidelines on designing efficient thermal management systems for RDEs are obtained: larger mass flow rates and multi-wave modes result in higher average wall heat flux; the heat flux at the outer wall exceeds that at the inner wall while both walls require effective cooling for gas turbine engines with a rotating detonation combustor. Furthermore, a novel heat transfer model for RDEs is proposed based on a thermal operation map depicting total heat transfer rates to describe the nonlinear impact of mass flow rate and number of detonation waves, which can be employed to predict total wall heat loads under specific operation conditions of RDE.

Effects of activation energy on irregular detonation structures in supersonic flow

In this work, high-precision numerical simulations of detonations in supersonic hydrogen–oxygen premixed gases with different activation energies are carried out. The open-source program Adaptive Mesh Refinement in Object-Oriented C++ is adopted, and the monotone upstream–centered scheme for conservation laws total variation diminishing numerical scheme is utilized to solve the Euler equations coupled with a one-step, two-component reaction model. The wave structure characteristics of the irregular cellular detonation process are obtained, and its initiation and propagation characteristics under different activation energies are analyzed in depth. The results show that, unlike a regular detonation wave structure, the Mach stem of an irregular detonation wave is prone to bifurcation in a supersonic mixture with high activation energy. In addition to the incident shock wave and the Mach stem structure, a hybrid shock wave structure also appears between the two due to the random generation of weak triple points. Moreover, the leading shock wave intensity of the irregular detonation weakens, resulting in the generation of many unburned jets whose sizes and shapes depend on the triple point type. Although the oscillation amplitude of the irregular detonation is large and its regularity is weak, the detonation wave can achieve approximate dynamic stability in the channel.

On the Optimal Choice of Type of Combustion Chamber for the Initiation of Gas Detonation

A numerical simulation of continuous gas detonation in the combustion chamber based on the Navier-Stokes equations, taking into account turbulence and diffusion of substances, is carried out. A comparative analysis of the efficiency of detonation combustion of fuel depending on the geometric parameters of the chambers is performed. Three possible camera types are considered. Fuel and oxidizer were fed separately into the chambers through nozzles at a certain angle to the chamber surface. The detonation process was largely determined by the intensity of the turbulent mixing of reagents (hydrogen and oxygen). Calculations show that the type of camera with a flat radial geometry is the most optimal to establish a stable detonation regime.

Simulation of Gaseous Detonation of Hydrocarbon Fuel under Oxygen Lack

Simulation of Gaseous Detonation of Hydrocarbon Fuel under Oxygen Lack

A hybrid lattice Boltzmann method for gaseous detonations

This article is dedicated to the construction of a robust and accurate numerical scheme based on the lattice Boltzmann method (LBM) for simulations of gaseous detonations. This objective is achieved through careful construction of a fully conservative hybrid lattice Boltzmann scheme tailored for multi-species reactive flows. The core concept is to retain LBM low dissipation properties for acoustic and vortical modes by using the collide and stream algorithm for the particle distribution function, while transporting entropic and species modes via a specifically designed finite-volume scheme. The proposed method is first evaluated on common academic cases, demonstrating its ability to accurately simulate multi-species compressible and reactive flows with discontinuities: the convection of inert species, a Sod shock tube with two ideal gases and a steady one-dimensional inviscid detonation wave. Subsequently, the potential of this novel approach is demonstrated in one- and two-dimensional inviscid unsteady gaseous detonations, highlighting its ability to accurately recover detonation structures and associated instabilities for high activation energies. To the authors' knowledge, this study is the first successful simulation of detonation cellular structures capitalizing on the LBM collide and stream algorithm.

Deep Potential Molecular Dynamics Study of Chapman-Jouguet Detonation Events of Energetic Materials.

Detonation of energetic materials (EMs) is of great importance for military applications, while the understanding of detailed events and mechanisms for the detonation process is scarce. In this study, the first deep neural network potential NNP_Shock for molecular dynamics (MD) simulation of shock-induced detonation of EMs was generated based on a deep potential model, providing DFT accuracy but 106 times the computational efficiency. On this basis, we employ our deep potential to perform MD simulations of shock-induced detonation of high-performance EM material 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20, C6H6N12O12) and obtain the theoretical Chapman-Jouguet (C-J) detonation velocities and pressures directly by multiscale shock technique (MSST) for the first time, which are in good agreement with experiment. In addition, the Hugoniot curves and initial reaction mechanisms were successfully obtained. Therefore, the NNP_Shock potential is competent in research of the detonation performance and shock sensitivity of CL-20, and the method can also be transplanted to studies of other EMs.

Implementation of an OpenFOAM solver for shock and detonation simulation at high pressure

The high pressure condition widely used in industry makes it necessary to evaluate the impact of real gas behaviour in numerical simulation, especially for shock and detonation problems. Since most open source solvers are based on ideal or perfect gas assumption, we have developed an OpenFOAM solver for Real gas Shock and Detonation simulation, referred to as RSDFoam. We have considered the nonidealities in the equation of state, thermodynamic functions and mass action law brought about by the interaction between the fluid particles and by their finite volume. Connection between blastFoam and Cantera was built to utilize the CFD capabilities from the former and the efficient chemistry solver and real gas models in Cantera. The new solver has been thoroughly validated against analytical solutions, previous numerical simulation results and experimental data. For non-reactive flow, shock tube and oblique shock problems were solved. For reactive cases, constant volume reactor, steady detonation speed, reaction zone structure, and cellular structure were numerically studied. The satisfactory agreement demonstrates the accuracy and robustness of the solver for real gas based shock and detonation simulation.

Experimental and Numerical Study of Pulse Detonation Engine with Ethylene as a Fuel

This paper presents an insight on the study of transient, compressible, intermittent pulsed detonation engine with one-step overall reaction model to reduce the computational complexity in detonation simulations. Investigations are done on flow field conditions developing inside the tube with the usage of irreversible one-step chemical reactions for detonations. In the present simulations one and two-dimensional axisymmetric tubes are considered for the investigation. Studies are also performed with different grid sizes which influence the prediction of Von-Neumann spike, CJ Pressure and detonation velocity. Numerical studies are conducted using 66mm diameter tube and compared with the literature values. The simulation result from the single-step reaction model agrees well with the previous published literature of multi-step reaction models. The present studies shows that one-step overall reaction model is sufficient to predict the flow properties with reasonable accuracy. Experiments are conducted in a 25mm dia. tube with Ethylene/Air mixtures. The reactants are premixed and injected into the detonation tube using solenoid valves. The equivalence ratio of the fuel/oxidizer mixture and the length of the detonation tube are varied to understand their effects on detonation parameters. Finally the results from the present numerical study are compared and validated using NASA CEA and experiments.

DetonationFoam: An open-source solver for simulation of gaseous detonation based on OpenFOAM

Detonation has promising applications in advanced propulsion systems, and numerical simulation is widely used to gain insights into the complex interaction between the hydrodynamic flow and chemical reactions involved in detonation. In this work, detonationFoam, an open-source solver for accurate and efficient simulation of compressible reactive flow and detonation are developed based on OpenFOAM. detonationFoam can simulate compressible, multi-component, reactive flow and it can accurately evaluate the detailed transport coefficients using the mixture-averaged transport model. Compared to rhoCentralFoam, the improved HLLC-P approximate Riemann solver is used in detonationFoam and it helps to accurately resolve shock waves appearing in detonation. Besides, the adaptive mesh refinement and dynamic load balancing algorithms are used in detonationFoam, which greatly improves the computational efficiency. Validation tests including homogenous ignition, unsteady diffusion, shock tube problem, premixed flame, planar detonation, double Mach reflection, detonation cellular structure and oblique detonation wave are conducted. These tests demonstrate that detonationFoam can be used to accurately and efficiently to simulate the compressible, multi-component reactive flow and detonation processes. Program summaryProgram Title: detonationFoamCPC Library link to program files:https://doi.org/10.17632/x45zh4nz28.1Developer's repository link:https://github.com/JieSun-pku/detonationFoamLicensing provisions: GPLv3Programming language: C++Nature of problem: Gaseous detonation involves different length scales and complicated chemistry. To accurately and efficiently simulate the gaseous detonation, adaptive mesh refinement needs to be conducted and detailed chemistry should be considered. Besides, the severe load imbalance caused by the chemical source term evaluation may greatly reduce the computation efficiency.Solution method: An open-source solver, detonationFoam is developed based on OpenFOAM. The species equations considering detailed chemistry are solved in detonationFoam and thereby detonation in a compressible, multi-component, reactive flow can be simulated. The adaptive mesh refinement technique and the dynamic load balancing algorithm are incorporated into detonationFoam. It is demonstrated that detonationFoam can accurately and efficiently simulate gaseous detonation.

System modeling and simulation of flyer acceleration and explosive detonation in exploding foil initiator

In this theoretical study on an exploding foil initiator (EFI), the sequential events in an EFI system were numerically modeled and investigated from metallic bridge burst by ohmic heating and flyer acceleration by plasma expansion to explosive detonation by high-speed flyer impact. The EFI system modeling employed mass, momentum, and energy conservation coupled with the resistance–inductance–capacitance circuit equation of the initiation circuit and plasma property calculations of highly dense metallic plasma as well as a semi-empirical detonation model. The aim was to predict transient bridge behavior, flyer velocity, and detonation initiation threshold. Through comparisons and verifications with measured data from several existing EFI firing tests, the present system model was shown to predict bridge burst and flyer velocity very well. The numerical results indicated two different thresholds of charging voltage for flyer creation out of plastic film and impact detonation of explosive charge to be quite consistent with the measurements. The system behaviors in three different ranges of charging voltage were discussed in terms of discrete nature of this high-voltage explosive charge initiator.

On the feasibility and performance of the ammonia/hydrogen/air rotating detonation engines

A series of numerical simulations were performed to investigate the feasibility and performance of the premixed ammonia/hydrogen/air rotating detonation engines. A 19 species and 80 reactions ammonia/hydrogen/air mechanism is adopted and validated for detonation simulations. The effects of injection total temperatures (T0) and ammonia/hydrogen equivalence ratios (φNH3 and φH2) are analyzed under a fixed global equivalence ratio of 1. The propagation map of rotating detonation waves is numerically outlined. The result indicates that a higher injection total temperature and a lower ammonia equivalence ratio are beneficial to the successful propagation of rotating detonation waves. The maximum φNH3 with successful propagation of rotating detonation waves reaches 0.6, achieved at T0 = 1000 K. High total temperatures and ammonia equivalence ratios can lead to lower detonation wave speeds. The detonation height is found to account for around 20%–36% of the engine axial length. The critical accommodated detonation cell number for successful propagation of rotating detonation waves is 5.9, below which the rotating detonation wave will have difficulty maintaining propagation. Mass-flow-averaged and area-averaged methods are adopted to evaluate the pressure gain performance of NH3/H2/air RDE. The results of the two methods both indicate that the total pressure gain is significantly affected by the injection total temperature but less affected by the equivalence ratio of NH3. In addition, it is found that NOx emission is dominated by NO. The NOx emission increases with increased injection total temperatures and ammonia equivalence ratios. Negligible NOx emission is produced in pure hydrogen-fueled RDE while it reaches the maximum (0.037) at φNH3 = 0.6 and T0 = 1000 K.

A modified Lotka–Volterra oscillating chemical scheme for detonation simulation

Modified Lotka–Volterra chemical schemes were developed with the goal of performing numerical simulation of detonation driven by single- and multi-stage heat release profiles. An initiation reaction was added to the original Lotka–Volterra model to create an induction zone, which is an important characteristic of combustion process. The kinetics parameters of the reaction rates were adjusted, so that up to eight peaks of heat release could be generated in the steady detonation reaction zone. The structure of steady detonations driven by modified Lotka–Volterra models were examined in detail. Interestingly, the stability criteria typically employed to characterize detonations, i.e., the reduced activation energy and the χ parameter, do not seem to be applicable for Lotka–Volterra schemes exhibiting multi-stage heat release profiles. The applicability of these multi-step chemical models to unsteady detonation simulation was verified through preliminary results obtained for one- and two-dimensional numerical simulations. Under super-critical detonation initiation by a point-energy source, some Lotka–Volterra schemes led to an unusual behavior with large velocity oscillations at large over-drive but a rather steady propagation at near Chapman–Jouguet velocity. Two-dimensional cellular detonation driven by Lotka–Volterra scheme with two stages of heat release and a high activation energy of the initiation step demonstrates some features which are characteristic of a double cellular structure. The present work constitutes a first step toward the understanding of the features and dynamics of detonation driven by Lotka–Volterra schemes as further work is needed to fully grasp the complex responses induced by multiple stages of heat release on detonation dynamics.