A comparison of the emission and impingement heat transfer of LPG-H ₂ and CH ₄-H ₂ premixed flames

Experiments were performed to add hydrogen to liquefied petroleum gas (LPG) and methane (CH ₄) to compare the emission and impingement heat transfer behaviors of the resultant LPG-H ₂-air and CH ₄-H ₂-air flames. Results show that as the mole fraction of hydrogen in the fuel mixture was increased from 0% to 50% at equivalence ratio of 1 and Reynolds number of 1500 for both flames, there is an increase in the laminar burning speed, flame temperature and NO _x emission as well as a decrease in the CO emission. Also, as a result of the hydrogen addition and increased flame temperature, impingement heat transfer is enhanced. Comparison shows a more significant change in the laminar burning speed, temperature and CO/NO _x emissions in the CH ₄ flames, indicating a stronger effect of hydrogen addition on a lighter hydrocarbon fuel. Comparison also shows that the CH ₄ flame at α = 0% has even better heat transfer than the LPG flame at α = 50%, because the longer CH ₄ flame configures a wider wall jet layer, which significantly increases the integrated heat transfer rate.