Evaluating methane substitution by NH3/H2/C3H8 blends in premixed combustion: Feasibility assessment through laminar burning velocity, flame instability and combustion efficiency

To support the low-carbon transition of energy systems, this study investigates the combustion characteristics of NH₃/H₂/C₃H₈ ternary blends with methane-equivalent calorific value using the spherical expanding flame method. The laminar burning velocity (LBV) can be adjusted to match methane via blend ratio design. As NH₃ volume increases from 0 to 0.712, LBV drops by over 66 %. The chemical and thermal effects were separated, and radiation effects were quantified. Key flame parameters, including Markstein length, expansion ratio, flame thickness, critical Peclet number, Karlovitz number, and dimensionless growth rate, were analyzed to evaluate the influence of fuel composition and equivalence ratio on flame propagation and stability. Higher NH₃ fractions improved flame stability. Methane interchangeability was assessed using the High Wobbe index and LBV. Results show that MECV-based NH₃/H₂/C₃H₈ blends offer good combustion performance and are promising low-carbon methane alternatives.