Numerical Study of Pulse Detonation Engine with One-step Overall Reaction Model

This paper presents an insight for 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 1-D and 2-D axisymmetric tubes are considered for the investigation. The flow conditions inside the detonation tube are estimated as a function of time and distance. Studies are also performed with different grid sizes which influence the prediction of Von-Neumann spike, CJ Pressure and detonation velocity. The simulation result from the single-cycle 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. Finally, the results from the present study were compared and validated using NASA CEA.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 265-271, DOI: http://dx.doi.org/10.14429/dsj.65.873

Effect of Initial Disturbance on The Detonation Front Structure of a Narrow Duct

The effect of an initial disturbance on the detonation front structure in a narrow duct is studied by three-dimensional numerical simulation. The numerical method used includes a high resolution fifth-order weighted essentially non-oscillatory scheme for spatial discretization, coupled with a third order total variation diminishing Runge-Kutta time stepping method. Two types of disturbances are used for the initial perturbation. One is a random disturbance which is imposed on the whole area of the detonation front, and the other is a symmetrical disturbance imposed within a band along the diagonal direction on the front. The results show that the two types of disturbances lead to different processes. For the random disturbance, the detonation front evolves into a stable spinning detonation. For the symmetrical diagonal disturbance, the detonation front displays a diagonal pattern at an early stage, but this pattern is unstable. It breaks down after a short while and it finally evolves into a spinning detonation. The spinning detonation structure ultimately formed due to the two types of disturbances is the same. This means that spinning detonation is the most stable mode for the simulated narrow duct. Therefore, in a narrow duct, triggering a spinning detonation can be an effective way to produce a stable detonation as well as to speed up the deflagration to detonation transition process.Comment: 30 pages and 11 figure

Development of a Chemically Reacting Flow Solver on the Graphic Processing Units

The focus of the current research is to develop a numerical framework on the Graphic Processing Units (GPU) capable of modeling chemically reacting flow. The framework incorporates a high-order finite volume method coupled with an implicit solver for the chemical kinetics. Both the fluid solver and the kinetics solver are designed to take advantage of the GPU architecture to achieve high performance. The structure of the numerical framework is shown, detailing different aspects of the optimization implemented on the solver. The mathematical formulation of the core algorithms is presented along with a series of standard test cases, including both nonreactive and reactive flows, in order to validate the capability of the numerical solver. The performance results obtained with the current framework show the parallelization efficiency of the solver and emphasize the capability of the GPU in performing scientific calculations. Distribution A: Approved for public release; distribution unlimited. PA #1117

A Computational Study of Thermo-Fluid Dynamics of Pulse Detonation Engines

The purpose of this thesis is to use a transient Computational Fluid Dynamics computer code written in FORTRAN 90 for full reaction kinetics, to perform an analysis of the physical processes and chemical phenomena occurring on a single cycle of an ideal Pulse Detonation Engine (PDE) using a stoichiometric mixture of H2 and O2. A small zone of high pressure and temperature is used to initiate the detonation wave in the PDE. A simple case with no chemical reactions and the same PDE geometry and “computational spark” is also tested. The speed of the wave relative to the reactants and a comparison with the simple case with no chemical reactions are used to verify the existence of a detonation wave being driven by the combustion of the reactants. The results and behavior of the detonation wave as it propagates through and out of the PDE are compared to those of similar numerical and experimental PDE cases in the literature, to verify the accuracy of the results. The results show that the basic physics and chemical phenomena occurring in the PDE can be modeled using a first order accurate computational code with non-equilibrium kinetics. In future works the accuracy of the code will be increased to six-order in the spatial dimension to be able to model highly structured phenomena such as Deflagration to Detonation Transition (DDT) and fuel injection in supersonic flow for PDE applications

NOVEL SIDE-VENT-CHANNEL BASED BLAST MITIGATION CONCEPT FOR LIGHT TACTICAL VEHICLES

A new concept solution for improving survivability of the light tactical military vehicles to blast-loads resulting from a shallow-buried mine detonated underneath such vehicles is proposed and critically assessed using computational engineering methods and tools. The solution is inspired by the principle of operation of the rocket-engine nozzles, in general and the so called \u27pulse detonation\u27 rocket engines, in particular, and is an extension of the recently introduced so-called \u27blast chimney\u27 concept (essentially a vertical channel connecting the bottom and the roof and passing through the cabin of a light tactical vehicle). Relative to the blast-chimney concept, the new solution offers benefits since it does not compromise the cabin space or the ability of the vehicle occupants to scout the environment and, is not expected to, degrade the vehicle\u27s off-road structural durability/reliability. The proposed concept utilizes properly sized and shaped side-vent channels attached to the V-shaped vehicle underbody. The utility and the blast-mitigation capacity of this concept is examined in the present work using different (i.e. coupled Eulerian/Lagrangian and coupled finite-element/discrete-particle) computational methods and tools. To maximize the blast-mitigation potential of the proposed solution, standard engineering optimization methods and tools are employed for the design of side-vent-channels. It is shown that, by proper shaping and sizing of the side-vent-channels, venting of ejected soil and supersonically-expanding gaseous detonation products can be promoted, resulting in an increase in the downward thrust on the targeted vehicle. Furthermore, it is found that optimization of the geometry and size of the side-vent-channel solution for the maximum blast-mitigation performance, requires consideration of a tradeoff between the maximum reductions in the detonation-induced total momentum transferred to, and the acceleration acquired by, the target vehicle. The results obtained farther confirmed theblast-mitigation effects of the side-vent-channels, although the extent of these effects is relatively small (3-4%)

Numerical Simulation of Pulse Detonation Engine Phenomena

This paper describes one- and two-dimensional numerical simulations, with simplified as well as full reaction kinetics, of a single cycle pulse detonation engine (PDE). The present studies explore the ignition energies associated with the initiation of a detonation in the PDE tube, and quantify reactive flow phenomena, performance parameters, and noise generation associated with full and simplified kinetics simulations of the PDE. Comparison of these parameters is made with available experimental data. The present simulations demonstrate the ability to predict PDE reactive flow phenomena and associated performance and noise characteristics, and hence have promise as a predictive tool for the evolution of future PDE designs