## 1 Introduction
### Ammonia Flame Enhancement by Fuel Blending  
Several researchers have successfully investigated neat ammonia as a promising fuel. This research has covered various aspects, including flame propagation speed, chemical kinetics, and its application in internal combustion engines and gas turbines. Consequently, these studies have shown that ammonia has the potential to replace hydrocarbon-based fuel, as mentioned previously [1]. In an effort to overcome the challenges associated with ammonia combustion, such as higher NO\({}_{x}\) production, long ignition delay times, and lower laminar burning velocity (LBV), many researchers have started studying the effects of blending light and heavy fuels with ammonia to enhance combustion characteristics. Additionally, the buoyancy effect, a drawback in ammonia combustion, can be mitigated by increasing oxygen content, raising the initial temperature, or blending ammonia with fuels that have higher LBV. This section demonstrates the effect of fuel blending with ammonia on LBV, highlighting its potential for successful applications of ammonia as a fuel in various contexts.  
Several fundamental studies on LBV enhancement of ammonia, blended with methane [19; 20; 21; 22; 23; 24; 25; 26] and hydrogen [27; 28; 29; 30; 31; 32; 33; 34], have been conducted both experimentally and numerically with additional hydrogen-methane blending [35; 36; 37; 38; 39; 40; 41; 42; 43] to optimize the accurate model prediction of oxidation models. The literature studies continuously show that a small fraction of H\({}_{2}\) blended with NH\({}_{3}\) or CH\({}_{4}\) will increase the flame speed, despite the equivalence ratio and initial conditions. When 4% NH\({}_{3}\) was blended with a CH\({}_{4}\)-air mixture, [PERSON] et al. [23] found that the LBV decreased by 17-23% as the mixture progressed from the lean to the rich side. [PERSON] et al. [21] reported a non-linear decrease in the LBV of the CH\({}_{4}\) NH\({}_{3}\) flames with the NH\({}_{3}\) addition (0-50%) and developed a kinetic model for CH\({}_{4}\)-NH\({}_{3}\) flames. Moreover, they found that stretched LBV decreased as the mixture pressure and NH\({}_{3}\) concentration increased, and the production of OH radicals in CH\({}_{4}\)/NH\({}_{3}\)/air flames resulted in the formation of NH\({}_{2}\) molecules, which greatly increased NO\({}_{x}\) emissions; this blending improves the combustion characteristics of ammonia mixtures and reduces the CO\({}_{2}\) emission as a result of low-carbon fuels with flame speeds higher than that of ammonia [20].  
The blending of hydrogen is a logical attempt to achieve carbon-free flame and LBV enhancement instantly, thereby enhancing the flame. In the case of H\({}_{2}\)/NH\({}_{3}\), hydrogen exhibits higher mass diffusivity compared to ammonia. This makes hydrogen a promising additive for improving performance while minimizing NO\({}_{x}\) and N\({}_{2}\)O emissions in fuel-rich ammonia/air flames. Additionally, an increase in the blend of H2 tends to make the flame more sensitive to stretch. According to [PERSON] et al. [44], the addition of 30-50% H\({}_{2}\) blended with NH\({}_{3}\) exponentially increased the LBV to 84%, thanks to the diffusivity and high reactivity of hydrogen. As a result, the LBV reached a similar order of magnitude as that of a CH\({}_{4}\)/air flame at approximately \(X_{H_{2}}=40\)  
This study examines the use of hydrogen and methane as additives in ammonia-based combustion. It also explores the blending of ammonia with a single fuel. The structure of this study is as follows: Section 1 provides an introduction to the study and includes a literature review on ammonia blending. Section 2 describes the experimental setup, procedure, and data analysis method. Section 3 explains the kinetic models employed in the study. Section 4 presents the experimental results of combustion for ternary blend mixtures. Finally, Section 5 summarizes the future perspectives of ammonia-based combustion and concludes the study.