Detailed Chemical Kinetics Based Simulation of Detonation-Containing Flows

Abstract

Reliable and robust simulations of detonations in inhomogeneous and turbulent environments are of direct importance in the design of rotating detonation engines (RDEs). In particular, computational models will be especially useful in designing and optimizing discrete injectors that introduce fuel and air separately into the detonation chamber, but ensure appropriate level of mixing to sustain detonations but minimize backflow of detonation products and pressure waves into the feed plenums. Since the structure of detonations itself is non-ideal, models have to include a detailed description of this reacting flow in order to be predictive in nature. Here, a highly-scalable open source based solver has been developed for complex detonating flows such that a) the detonation processes are described using detailed chemical kinetics, b) the method is computationally efficient through the introduction of adaptive mesh refinement, and c) the solver can handle complex geometries of relevance to RDE design. Grid convergence of key metrics for detonations is evaluated using canonical flows. Further, the importance of the use of detailed chemical kinetics is illustrated by extracting the composition structure behind a two-dimensional detonation front. Finally, simulations of a practical RDE configuration are used to demonstrate the applicability of this solver to analyzing geometries. The simulation captures the general trends of the experiment well. It is found that the detonation occurs under partially-premixed conditions. Propagation of pressure waves to the injection system is observed which could influence flow behavior in the oxidizer plenum.

Numerical and boundary condition effects on the prediction of detonation engine behavior using detailed numerical simulations

“…A fractional time-stepping method is used to integrate the chemical source terms, where the convection terms are advanced in two half-steps, with the chemical source term advanced in between these half-steps. The solver has been extensively tested for detonation-containing flows, and numerical convergence for a variety of flow configurations has been studied (Sato et al, 2018b;Sato and Raman 2020;Sato et al, 2021a;Sato et al, 2021b;Prakash et al, 2020). A brief examination of the effects of numerics and interpolation methods on the RDE simulation results shown in this study is provided in the Supplementary Material.…”

“…However, this boundary condition cannot be applied to the full RDE system due to flashback of the burnt gases. There are two possible choices for the inlet boundary conditions, the total pressure boundary (Sato et al, 2018b;Sato and Raman 2020) and the constant mass flow boundary (Cocks et al, 2016;Sato et al, 2021b;Sato et al, 2021a). It is known that both of the boundary conditions successfully sustain detonation waves in the chamber.…”

Effects of fluctuations in concentration on detonation propagation

“…Sizes of 0.7-2 mm were also obtained in previous studies using at least four mechanisms. 32,38,41,42 Shimizu 41 ha argued that the size of the detonation cell significantly depends on the pressure-dependent reaction. Even so, the largest cell size (~2 mm) with such a mechanism is comparable to our results.…”

A Neural Network Inspired Formulation of Chemical Kinetics

“…The 1-D detonation simulations were conducted with the OpenFOAM-based solver UMdetFOAM [36][37][38], which solves the governing equations of fluid flow consisting of mass, momentum, energy, and species conservation equations. UMdetFOAM is a compressible flow solver which contains shock-capturing numerics using the Monotonic Upwind Scheme for Conservation Laws (MUSCL)-based Harten-Lax-van Leer-Contact (HLLC) scheme [37,39], a second-order Runge-Kutta temporal discretization with minimal dissipation [40], and the Kurganov, Noelle, and Petrova (KNP) scheme [41] for diffusion terms. For chemical reactions, the package Cantera [42] is utilized in the purely CPU-based solver, whereas the GPU-offloaded UMdetFOAM uses the methodology outlined in Sec.…”

“…2 implemented in the CUDA and cuBLAS environments. This code has been extensively validated using experiments of detonation-containing flows [36][37][38][39].…”