## 3 LBV of Conventional Aviation Fuel
### The Effect of Additives on Aviation Fuel LBV  
As a species with significant radiative properties, water's influence on combustion radiation directly impacts the operational state of aviation engines under harsh conditions. But currently, most research is focused on the effect of water on the LBV of simple fuel systems, such as syngas mixtures, propane-air mixtures, and oxygen-enriched methane [45; 46; 47]. [PERSON] et al. demonstrated that radiation reabsorption of water in polluted air significantly affects the accurate prediction of aviation fuels' LBV [48]. In high-enthalpy vitiated air with mole fractions of 21% O\({}_{2}\), 12% H\({}_{2}\)O, and 67% N\({}_{2}\), PR-3's LBV increases initially with increasing equivalence ratio, peaking at \(\Phi\) = 1.15, with S\({}_{\rm Lmax,ADI}\) = 67.30 cm/s and S\({}_{\rm Lmax,SNB}\) = 70.03 cm/s (420 K, ADI = adiabatic model, SNB = statistical narrow-band model). With increasing equivalence ratio, the relative difference between SNB and ADI simulation results decreases initially, then increases at atmospheric pressure. At lean conditions (\(\Phi\) = 0.7), the maximum relative difference of (S\({}_{\rm L,SNB}\)-S\({}_{\rm L,ADI}\))/S\({}_{\rm L,ADI}\) = 12.60%. According to simulation results and sensitivity analyses, the influence of radiation reabsorption on LBV stems primarily from chemical rather than physical factors, such as optical thickness and the absorption coefficient. The key elementary reaction enhancing LBV is CH\({}_{2}\)OH + H = CH\({}_{3}\) + OH, with radiation reabsorption inhibiting this reaction'seffect on LBV simulation results initially increasing then decreasing with an increasing equivalence ratio. Considering pressure variations within the 1-10 atm range, the reaction H + O\({}_{2}\) = O + OH, dominated by OH radicals' sensitivity to radiation reabsorption, becomes predominant, enhancing the impact of radiation reabsorption on LBV simulation result differences with increasing pressure. Conversely, slight increases in LBV simulation result differences between 10 and 15 atm are controlled by direct radiation effects. At 15 atm pressure, radiation reabsorption's influence on LBV simulation result differences reaches 12.41%. Liquefied natural gas (LNG) is considered a promising aviation alternative fuel due to its abundant resources, low cost, and low greenhouse gas (GHG) emissions. However, its direct application necessitates changes in the design of fuel tanks and fuel delivery systems due to LNG's low-temperature liquid state. Moreover, the low energy density and slow combustion rate of methane pose new requirements for engine and combustion chamber design. Therefore, blending LNG with traditional aviation fuels appears to be a method to reduce GHG emissions in the aviation industry without altering existing aircraft and engine structures [49]. [PERSON] et al. investigated the fundamental combustion characteristics of CH\({}_{4}\)/RP-3/air mixtures in a constant-volume combustion bomb, finding that LBV_max occurs at an equivalence ratio of 1.1, independent of initial temperature, pressure, and methane mixture ratio [50]. LBV increases with higher initial temperatures and lower initial pressures, following a similar trend as pure RP-3 and pure CH\({}_{4}\). Increasing the methane mixture ratio reduces the LBV of the blend fuel, with a significant decrease observed after the methane mixture ratio exceeds 0.8. Sensitivity analysis indicates that highly reactive components strongly correlated with LBV, such as H and OH, exhibit reduced peak molar fractions with increasing methane mixture ratio, leading to decreased LBV. Additionally, the addition of methane reduces the Arrhenius factor of the blend fuel, exp (T\({}_{a}\)/2 T\({}_{ad}\)), which significantly impacts LBV, particularly when the methane mixture ratio exceeds 0.8, explaining the observed LBV trend. Some differences exist between [PERSON] et al. 's study and previous research [51].