Numerical Simulation of Autoignition Characteristics of Lean Hydrogen-Air Mixtures

Simulations of autoignition and combustion processes in lean and ultra-lean hydrogen-air mixtures are performed in relation to safety aspects of nuclear power plants. Ignition delay times tau and laminar burning velocities S-L are evaluated. Comparisons between simulation results obtained for temperatures ranging from 800 to 1700 K at initial pressures of 1 and 6 bar show that both the value of tau and the temperature-dependent behavior of autoignition characteristics vary weakly with hydrogen concentration in air. The largest difference between the values of tau predicted by different detailed kinetic mechanisms (DKMs) is observed at temperatures of 900 and 1100 K for pressures of 1 and 6 bar, respectively. The time to reach peak heat release significantly exceeds tau at initial temperatures above 1250 K. Simulations based on the different DKMs yield similar values of S-L. It is concluded that each of the DKMs employed can provide satisfactory accuracy of simulations of autoignition and combustion processes in lean and ultra-lean hydrogen-air mixtures at pressures below 6 bar.

Automated summary

Simulations of autoignition and combustion processes in lean and ultra-lean hydrogen-air mixtures show that temperature has a significant effect on the autoignition characteristics, while hydrogen concentration has a weak influence. Different detailed kinetic mechanisms provide satisfactory accuracy in simulating these processes at pressures below 6 bar.