Influence of airflow velocity on friction ignition behavior of Ti3Al-based alloy

Abstract

The ignition behavior of Ti3Al-based alloy in 220-380 m/s gas flow environment was studied by using friction ignition method. Combined with numerical calculations, the influence of airflow velocity on surface oxygen concentration and oxidation control step was analyzed, and then the influence of airflow velocity on ignition behavior was discussed. The results show that the Ti3Al-based alloy begins to ignite when the airflow velocity reaches 240 m/s.When the airflow velocity reaches 360 m/s, the Ti3Al-based alloy no longer ignites.Under low airflow velocity conditions, the surface oxygen concentration at high temperature is lower than the critical value, and the oxidation reaction control step changes from the chemical kinetics process at low temperature to the diffusion process of oxygen to the alloy surface at high temperature. As the airflow velocity increases, although the convective heat dissipation rate increases, the increase rate of the oxidation heat generation rate caused by the increase of the surface oxygen concentration is greater than that of convective heat dissipation rate, which increases the heating rate and promotes the ignition of Ti3Al-based alloy.Under high airflow velocity conditions, the surface oxygen concentration at high temperature is still higher than the critical value, and the control step of the oxidation reaction is always the chemical kinetics process. At this time, with the increase of airflow velocity, the increase rate of oxidation heat generation rate at high temperature is smaller than that of convective heat dissipation rate, resulting in a decrease in heating rate, which is not conducive to the ignition of Ti3Al-based alloy.

Keywords

• ti3al-based alloy
• airflow velocity
• friction ignition
• mechanism
• titanium fire