Experimental measurements of laminar burning velocity of premixed propane-air flames at higher pressure and temperature conditions

Abstract

This paper presents laminar burning velocity (LBV) measurements of premixed propane-air flames simultaneously at higher mixture pressure (1-5 atm) and temperature (350-630 K) conditions over mixture conditions (ϕ = 0.7-1.3) utilizing the externally heated diverging channel (EHDC) method. The maximum LBV was observed at ϕ = 1.1 for all pressure and temperature conditions. The non-monotonic behavior of the temperature exponents was noted with the minima at ϕ = 1.1. The pressure exponent (β) variation was observed to be parabolic with the maxima at ϕ = 1.0. The current measurements are then compared with the literature results, and the detailed kinetic model predictions of Qin mech, San Diego mech, and USC mech II. The present LBV measurements are in a better match with the mechanism predictions of San Diego mech at the majority of mixture and pressure conditions. The current measurement suggests the variation of temperature exponent (α) as a function of pressure ratio, and pressure exponent (β) as a function of temperature ratio for different mixture conditions (ϕ). A revised power-law correlation for α and β variations is also suggested as, Su=Su0TuTu0∝0+∝11-PuPu0PuPu0β0+β11-TuTu0. The sensitivity analysis reveals a significant increase (≈ 45%) in negative sensitivity for the chain termination reaction H + CH3 (+M) ↔ CH4 (+M) (R56), with a rise in pressure and temperature at all mixture conditions. The reaction pathway analysis indicates a maximum increment in elemental flux (≈ 305 %) in the formation of ethane (C2H6) from its predecessor methyl radical (CH3), due to enhanced pressure and temperature conditions.