Hydrogen/PRF skeletal mechanism study based on shock tube experiments and kinetic analysis

In the present work, the experiments of measuring ignition delay times (IDTs) of the hydrogen/n-heptane mixture at high temperature (1130-1485 K) and low pressure (1.25 atm) by a shock tube is implemented. The results show that mixtures with higher hydrogen proportion and lower equivalence ratio present shorter IDT. In the case of high hydrogen proportion, the n-heptane addition causes an obvious inhibition effect on the ignition of the mixture. Whereas, as the hydrogen proportion decreases, such inhibition effect weakens. As the experi-mental values are consistent with the predicted IDTs by NUI (National University of Ireland) mechanism, the NUI mechanism was selected to conduct the kinetic study. The consumption of n-heptane at the initial stage of re-action is earlier than that of hydrogen because the activities of n-heptane's H-abstraction and decomposition reactions are relatively high. With shock tube experimental data as the calibration basis, a skeletal hydrogen/PRF (Primary Reference Fuel) mechanism, was updated from a skeletal PRF mechanism. The skeletal hydrogen/PRF mechanism, consisting of 49 species and 162 reactions had been validated against shock tube experiment of hydrogen, n-heptane, isooctane pure fuel, PRF, and hydrogen/n-heptane mixture.

Automated summary

The present work conducted experiments to measure the ignition delay times of hydrogen/n-heptane mixture at high temperature and low pressure using a shock tube. The results showed that mixtures with higher hydrogen proportion and lower equivalence ratio had shorter ignition delay times. As the hydrogen proportion decreased, the inhibition effect of n-heptane on the mixture's ignition weakened. The NUI mechanism was selected for the kinetic study as it was consistent with the experimental values. A skeletal hydrogen/PRF mechanism was updated from a skeletal PRF mechanism based on the shock tube experimental data, and it was validated against various fuel mixtures.