Exploring limonene combustion through laminar burning velocity measurements and Markstein length for next-generation SAFs

Sustainable aviation fuels (SAFs) are a critical pathway for reducing carbon dioxide (CO 2 ) emissions from the aviation sector, yet the deployment of new SAF candidates requires a robust understanding of their fundamental combustion behavior. Limonene, a renewable terpene derived from pine and citrus biomass, has emerged as a promising candidate due to its favorable energy content and bulk properties relative to conventional Jet A-1. However, despite increasing interest, fundamental premixed combustion data for limonene—particularly laminar burning velocity and flame stability parameters—remain limited. The aim of this study is to address this gap through an experimental investigation of the premixed combustion characteristics of limonene. Laminar burning velocity measurements were performed in spherical and cylindrical constant-volume reactors at atmospheric pressure and unburned-gas temperatures of 358, 398, and 438 K using Schlieren imaging. Experiments were conducted for pure limonene, the Jet A-1 surrogate fuel MURI-1, and a 70/30 (vol./vol.) MURI-1–limonene blend over equivalence ratios from 0.7 to 1.4. The results show that pure limonene exhibits high laminar burning velocities, reaching peak values of approximately 70 cm s⁻ 1 , exceeding those of conventional kerosene surrogates. Flame stability analysis reveals that limonene flames become increasingly sensitive to stretch under fuel-rich conditions, as indicated by decreasing Markstein length and Lewis number. Blending limonene with MURI-1 yields intermediate burning velocities and improves flame stability through increased Markstein length, despite a modest reduction in flame thickness, with enhancements of up to 8% observed under rich conditions. These findings provide new fundamental combustion data for limonene and demonstrate combustion trends consistent with other SAF candidates, supporting its potential as a viable component for future ASTM-certified sustainable aviation fuel formulations and for the development of validated chemical-kinetic models.