Measurements of Laminar and Turbulent Burning Velocities of N-Butanol/Air Mixtures at Elevated Temperatures and Pressures

Experimental results of laminar burning velocities ul and the associated flame front turbulent burning velocities utr and utm of premixed n-butanol air mixtures are measured inside a fan stirred combustion vessel, using high-speed Schlieren photography. Measurements were made between equivalence ratios from 0.7 to 1.4 at an initial temperature of 360 K and pressures ranging from 0.1 to 1.0 MPa. For turbulent studies, uniform and isotropic turbulence was created in the combustion vessel by four fans and turbulence rms velocities, u ′ = 0.5 up to 6.0 m/s were obtained. ul, and the associated parameters Lb, Masr, Pecl and the corresponding Kcl associated with the onset of instabilities is presented. ul, increased with <i>ϕ</i> and reduced with increasing pressure while Lb decreased with increasing pressure and <i>ϕ</i>. Masr decreases with pressure and increasing <i>ϕ</i>, with values becoming eventually negative at high pressures and rich mixtures. A satisfactory correlation exists between Kcl and Masr with an R2 value of 0.859. Turbulent burning rates of n-butanol/air mixtures at high initial temperatures and up to 1.0 MPa in a controlled environment are reported for the first time. utr, values increase with increase in both <i>ϕ</i> and u ′. Increase in equivalence ratio and u ′ also enhanced utr. utr of n-butanol/air mixtures are higher than iso-octane/air mixtures which is attributed to lower Masr. Dimensionless values of utm/uk′ decreased with increasing K for a given Masr. However, for a constant K, decrease in Masr lead to increased utm/uk′ values. The utm/uk′ curves from previous studies are extended to a positive Masr of 10 along with the quench regime identified. It is envisaged that the current work facilitates a rich database that can aid in detailed chemical modelling or engine simulations using n-butanol as fuel.