Laminar burning Velocities, Markstein numbers and cellular instability of spherically propagation Ethane/Hydrogen/Air premixed flames at elevated pressures

Laminar flame characteristics of ethane/hydrogen/air (with = 25 %, 50 %, 75 % and 100 % by volume) within an equivalence ratio from 0.7 to 1.3 were determined in a spherical constant volume combustion vessel at elevated pressure up to 0.5 MPa, temperature up to 360 K. Key combustion characteristics such laminar burning velocity, Markstein length/number, flame thickness, effective Lewis number, thermal expansion coefficient and critical conditions at the onset of cellular instability including critical radius and Peclet number, were either measured or calculated. These measurements were compared with the available literature data and with the predictions from chemical kinetics mechanisms, showing perfect fitting with the literature data, although the kinetics were overpredicted at a temperature of 360 K. The dependence of the ethane/hydrogen/air laminar burning velocities on temperature, pressure, and hydrogen ratio was analyzed using a datum empirical expression and blending law, yielding excellent agreement. A general correlation, based on the Peclet number against the Markstein number, has been proposed for various mixtures and conditions, aimed at defining the stable and unstable regimes of flame propagation. This correlation exhibits an value of 0.82, signifying a strong predictive capacity. The findings highlight that, compared with methane, ethane plays a promising role in enhancing the resistance of hydrogen mixtures to cellular flame instability, thereby fostering more stable flame propagation.