Laminar burning characteristics of coal-based naphtha

Coal-based naphtha is a promising alternative fuel as it fits the standards of energy replacement and is technologically mature, safe, and dependable. However, its laminar combustion characteristics have not been well studied. The laminar burning velocities and Markstein lengths of a kind of coal-based naphtha (C6.97142H15.88244) over a range of initial conditions were measured by Particle Imaging Velocimetry (PIV) in spherical explosions. In addition, a 3-component surrogate fuel model (62.4 mol% n-C6H14, 32.5 mol% i-C8H18 and 5.1 mol% i-C7H16) based on the Lawrence Livermore National Laboratory (LLNL) gasoline kinetics was proposed according to the detailed hydrocarbon analysis, and then validated against the measured laminar burning velocities. The proposed model performs reasonably well in simulating the laminar burning velocity of coal-based naphtha fuel. Dimensionless parameters including Markstein number, critical Peclet number, critical Karlovitz number and normalized burning velocity, were presented, from which the correlations between thermal diffusion (TD), Darrieus-Landau (DL), thermo-acoustic instabilities and stretch effects were explored. A negative correlation between the combustion intensity deflagration index and Markstein length also demonstrates that a lower stretch effect is favourable to increasing combustion intensity, hence increasing the heat release rate and efficiency of practical combustors.