The laminar and turbulent flame speed of methanol/ammonia/air, ethyl-acetate/ammonia/air, and dimethoxymethane/ammonia/air under atmospheric and elevated pressures

Experiments of the laminar and turbulent flame speed of typical E-fuels blended with ammonia: methanol/ammonia/(CH 3 OH/NH 3 )/air, ethyl-acetate/ammonia/(EA/NH 3 )/air, and dimethoxymethane/ammonia/(DMM/NH 3 )/air under atmospheric and elevated pressures (1 and 3 atm) are conducted in a fan-stirred constant volume combustion chamber , with initial temperature of 373 K. The results show that turbulent flame speed ( S T ) follow the same ranking order as laminar flame speed ( S L ) at fuel-lean side from high to low as: DMM, CH 3 OH, and EA; while with ammonia addition, CH 3 OH/NH 3 and EA/NH 3 have similar S L and S T values; and at fuel-rich side, DMM and EA show increasing S T and S T / S L values than at fuel-lean side Meanwhile, the measured Markstein length ( L b ) is decreasing towards the fuel-rich side and even becomes negative for EA. Ammonia addition enhances the turbulent flame wrinkling and deformation from the morphology analyses, and this leads to E-fuel/NH 3 blends always having higher normalized turbulent flame speed ( S T / S L ) than pure E-fuel. Next, we test several different turbulent flame speed correlations composed of ( u' / S L ) and ( l T / l F ), it is found that the power exponents of ( u' / S L ) and ( l T / l F ) do not necessarily have to be equal; they change as the turbulent regime varies in different zones. S T / S L / Ka = a ( Da / Le ) b performs best among all correlation types with 0.5 ≤ b ≤ 1 corresponding to the Damköhler's two limits. Comparing three types of Lewis number, it is found that volume based Le V has the best fitting goodness in the correlation of S T / S L / Ka = a ( Da / Le ) b . Taking into account the developing flame brush thickness, wrinkling ratio and integral length scale as a function of radius, the flame radius based Da R correlations are proposed: S T / S L / γ = a ( Da R / Le ) b where 0.5 ≤ b ≤ 1 which can unify present experimental data with Lewis number larger than unity and previous data with Lewis number less than unity.