Experimental Study on Quenching Distance of Hydrogen–Ammonia Blended Fuel in Air

Hydrogen–ammonia blended fuel has garnered considerable attention as an alternative to traditional fossil fuels. In this study, we experimentally investigated the dependence of the quenching distance of hydrogen–ammonia blended fuel in air on the hydrogen or ammonia fractions. Consequently, the quenching distance increased exponentially with increasing ammonia fraction (X_NH3). The equivalence ratio corresponding to the minimum quenching distance shifted to smaller side with decreasing X_NH3. The burning velocity of blended fuel in air at X_NH3 = 0.6 was comparable to that of methane–air or propane–air premixtures. Furthermore, the Peclet number estimated from the measured quenching distances decreased as the equivalence ratio decreased from unity, regardless of X_NH3. This trend is attributed to the influence of the Lewis number, which enhances flame stretch effects induced by the parallel flanges. It was also found that the quenching distance of hydrogen–ammonia blended fuel can be calculated by the estimated Peclet number by the equivalence ratio even, if it does not maintain a constant value.