Direct numerical simulation of premixed autoignition in non-linear subsonic and sonic compressible turbulence

Abstract

The autoignition of reactants is a fundamental aspect of the reliability and sustainability of high-speed combustion systems, such as in scramjet engines. High-speed combustion processes are characterized by large Karlovitz numbers such that the reactants may be well mixed and turbulence-chemistry interactions take place at spatial scales where the turbulence is both approximately isotropic and compressible (i.e., where turbulent velocity fluctuations directly generate thermoacoustic effects). In this study, we investigate the effects of strong dilatation, including eddy shocklets, on the ignition time and spatial scaling of autoignition kernels in new direct numerical simulations (DNS) of three-dimensional, homogeneous isotropic turbulence with reduced-order premixed hydrogen-air chemistry. The DNS is solenoidally-forced to turbulence Mach numbers corresponding to the thermodynamic, non-linear subsonic, and sonic compressibility regimes on with Taylor microscale Reynolds numbers Ret ≈ 150. It was found that increasing compressibility lead to increased intermittency and small-scale intensity of reaction rates.

Colin Towery
Colin Towery
Postdoctoral Research Associate

Colin is a former research associate in the Paul M. Rady Department of Mechanical Engineering at the University of Colorado Boulder and also a former student in the Turbulence and Energy Systems Laboratory, earned his PhD in May 2018.

Peter Hamlington
Peter Hamlington
Associate Professor

Peter is an associate professor in the Paul M. Rady Department of Mechanical Engineering at the University of Colorado Boulder and the principal investigator of the Turbulence and Energy Systems Laboratory.