Numerical Investigation of Hydrogen Role on Detonation of CH4/H2/air Mixtures

Abstract

ABSTRACT Steady one-dimensional Zeldovich-von Neumann-Dӧring (ZND) calculation and thermo-chemical analysis are performed to investigate the hydrogen role on ZND detonation of CH4/H2/air mixtures. Different hydrogen blend ratios (i.e. Hbr) ranging from 0% to 100% are selected in this paper. The results show that hydrogen blend ratio has a significant impact on the ZND detonation reaction pathway of stoichiometric CH4-air mixtures. When Hbr ≤ 20%, CH4 is converted to CO2 by route 1: CH4 => CH3 => C2H6 => … => CO2 and route 2: CH4 => CH3 => CH3O => CH2O => HCO => CO => CO2. When Hbr ≥ 50%, CH3 in route 2 is directly converted to CH2O through R97 (CH3 + O <=> CH2O + H). This causes different ZND detonation structures. The induction length decreases with hydrogen addition. This is because R0 (H + O2 <=> O + OH) governs the heat release during the induction stage, enhancing the energy absorption in induction stage and the molecular thermal decomposition after leading shock wave. Finally, the effect of hydrogen blend ratio on the detonation cell size is explored, and a prediction model of detonation cell size incorporated with detonation stability parameter and induction length is developed for CH4/H2/air mixtures.