Uncertainty propagation of chemical kinetics parameters and binary diffusion coefficients in predicting extinction limits of hydrogen/oxygen/nitrogen non-premixed flames

Abstract

A comprehensive investigation of the uncertainties associated with the experimental and numerical evaluation of the extinction strain rate in hydrogen/oxygen/nitrogen non-premixed flames is presented in this work. The reported new experimental uncertainties of the extinction strain rate include several sources of uncertainties that typically affect the characterisation of velocity and boundary conditions of counterflow flames via particle image velocimetry. The uncertainties associated with the numerical determination of the extinction strain rate not only depend upon the selected chemical kinetics parameters but also on the binary diffusion coefficients. In order to identify the major sources of uncertainties in the chemical and diffusion models, a Monte Carlo based high-dimensional model representation analysis of the extinction curve was performed. Independent and simultaneous perturbations of relevant chemical kinetics and diffusion parameters have shown that the uncertainties associated with the binary diffusion coefficients are about a factor of 10 smaller than the uncertainty due to chemical kinetics parameters. Since the experimentally well known binary diffusion coefficient for hydrogen and nitrogen, , accounts for most of the propagated uncertainty of the diffusion model, it is shown here that only a reduction of the uncertainty of chemical kinetics parameters will have a significant impact in improving the accuracy of the extinction strain rate predictions.

Keywords:

• uncertainty analysis
• extinction strain rate
• hydrogen
• diffusion coefficients
• chemical kinetics parameters

Acknowledgments

[Acknowledgments] This research was sponsored by the National Center for Hypersonic Combined Cycle Propulsion grant AFOSR/NASA FA 9550-09-1-0611 supported jointly by AFOSR and NASA.