Detailed structure of gaseous detonations informed by ultrafast laser diagnostics

Iowa State University, Ames IA

Investigators

Abstract

Combustible gas mixtures in confined spaces may sometimes detonate, releasing energy rapidly, and creating a supersonic reacting wave driven at thousands of meters per second. Understanding how and why this detonation occurs is essential for safety in mining and industrial settings where large scale gas leaks may occur. In addition, harnessing this energy may open new avenues for energy-efficient power generation and vehicle propulsion. This project provides laser-based measurements to resolve the detail of the detonation wave and inform the theory of detonation to better understand when detonation occurs and how the energy release may be harnessed in engineering systems. Advanced ultra-fast laser techniques are used to provide measurements of the structure of the detonation wave and provide experimental measurements necessary to test accurate models of gaseous combustion detonation. This project characterizes experimentally the detailed non-equilibrium structure of gas-phase detonation waves and inform the role of the coupled compression and reaction wave structure for both steadily propagating and accelerating detonation waves with advanced laser diagnostic tools. Detailed structural information is determined through temperature and species time-histories using recent developments in ultrafast laser Raman spectroscopy and time-resolved fluorescence imaging. An accessible and repeatable high repetition-rate micro-scale detonation tube is studied as well. Detailed information on the structure of the wave includes the translational, rotational, and vibrational energy partitioning as well as species profiles through the wave. Detailed mapping of the detonation wave structure to define the local thermodynamic state as well as the simultaneous pressure and species profiles enable the development of accurate predictive models taking into account non-equilibrium processes which are critical to predicting the detonation wave structure during steady propagation, acceleration, and failure. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.