Home – Home – Jornals – Combustion, Explosion and Shock Waves 2016 number 6

The processes of ignition and combustion of i -C₈H₁₈-H₂ and n -C₁₀H₂₂-H₂ composite propellants in air are analyzed numerically. It is demonstrated that addition of hydrogen both to standard alkane ( n -C₁₀H₂₂) and to alkane with a branched structure ( i -C₈H₁₈) leads to an increase in the ignition delay time τ_ind if the initial temperature of the mixture T ₀ is lower than a certain value T _l and, vice versa, to a decrease in τ_ind at T ₀ > T _l. The greater than fraction of hydrogen in the mixture, the greater the change in τ_ind . At sufficiently high temperatures ( T ₀ > T_h ), addition of a small amount of alkane (»2-10%) to hydrogen reduces the ignition delay time. The value of T _l depends on the pressure of the fuel-air mixture and, to a smaller extent, on the n -alkane type. The value of T_h depends on the fraction of alkane in the composite propellant. If the initial pressure is sufficiently high (10 atm and more), addition of a small amount of i -C₈H₁₈ or n -C₁₀H₂₂ to the hydrogen-air mixture reduces the value of τ_ind for all values of T ₀. These features are caused by close interaction of the alkane and hydrogen oxidation kinetics. It is demonstrated that composite propellants consisting of hydrogen and n -C₁₀H₂₂ ( i -C₈H₁₈) have a higher velocity of the laminar flame and wider limits of stable combustion than the hydrocarbons themselves. Nevertheless, a noticeable increase in the laminar flame velocity is observed only for the molar fraction of hydrogen in the composite mixture greater than 50%. In this case, it becomes possible to ensure stable combustion with a smaller fraction of NO in combustion products.