Effect of Strain Rate on Diffusion Flame Structure and Relationship in Scalar Fields

Nayak, Guguloth Mahesh and Nikhil, K and Kolhe, Pankaj S. and Balusamy, Saravanan (2021) Effect of Strain Rate on Diffusion Flame Structure and Relationship in Scalar Fields. In: Lecture Notes in Mechanical Engineering, 13 December 2019 - 17 December 2019.

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Abstract

The flow structure of a flickering methane jet diffusion flame is investigated using large eddy simulation employing steady flamelet model to accommodate the strain rate effect. The computed results are processed to obtain a synthetic schlieren image for direct visual comparison with the corresponding experimental schlieren image. Both the experiments and numerical simulations are carried out for jet diameter of 4 mm and Reynolds number of 500. For the accurate scalar field measurements in flames, using optical diagnostic techniques needs a careful investigation of state relationships in refractive index difference and temperature as both are dependent on the local composition. Chemical kinetics and differential diffusion affect the local composition in the flame and hence the scalar field measurements accuracy. It is observed that error in scalar field measurements close to stoichiometric mixture combustion is largest; therefore, modeling the chemical kinetics and species transport of flame is more critical for the scalar field measurements. Therefore, synthetic schlieren image comparison-based validation is employed as the numerical data accounts for strain rate effect on temperature, species concentrations and hence refractive index difference. Additionally, the flame structure is described statistically by mean, root-mean-square (RMS) and probability density function profiles of temperature.

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