Lewis number and Markstein length effects on turbulent expanding flames in a spherical vessel

• Three lean air–fuel mixtures were selected, with same unstretched laminar flame speed.
• Their stretch sensitivity, characterized by Markstein lengths, is different.
• Turbulent combustion in a spherical vessel has been investigated by using laser tomography.
• The importance of the stretch sensitivity has been demonstrated.

The turbulent combustion of three different lean fuel–air mixtures has been investigated in a spherical vessel running at different turbulent intensities. Those mixtures were selected to present almost the same unstretched laminar flame speed but various Markstein lengths and Lewis numbers which are relevant parameters to describe flame-stretch interactions. Mie-scattering tomography has been used to measure a global flame stretch and an equivalent flame propagation speed. Results prove that mixtures have same ranking in terms of flame stretch sensitivity as in laminar regime and show the importance of taking into account this parameter in modeling and to evaluate fuel performance in terms of burning speed in Spark-Ignition engine. Flame wrinkling and curvature measurement were also carried out and the wrinkling effect on the flame propagation has been identified.