Combustion characterization of a CH₄/O₂ rapid mixed swirl torch igniter for hybrid rocket motors

Combustion characteristics of a rapid mixed swirl torch igniter of CH₄/O₂ for hybrid rocket motors has been experimentally investigated. The igniter torch consists of four tangential slits circumferentially equispaced on the internal micro-combustion chamber allows tangential injection of O₂ gas, meanwhile the CH₄ flows into the main channel and interacts with four tangential O₂ injections flow to generate a swirl mixing of CH₄ and O₂. The ignitability of this swirl torch igniter was verified by large number of experiments in variation of equivalence ratio and total flowrate of CH₄/O₂. The flame structure of the igniter and effect of main oxidizer injection acting as a cross flow on the flame has been investigated by using OH* and CH* chemiluminescences techniques. It is found that the torch igniter can reliably ignite instantaneously in the range of equivalence ratio 0.2∼1.4 and the effect of main oxidizer injection on the flame is tiny and can be neglected. In addition, the performance of this rapid mixed swirl flame has been investigated by using a lab scaled hybrid rocket motor and compared with the same hybrid rocket motor ignited by catalytic bed. The performance of this igniter and its comparison with catalytic bed ignition will be discussed and analyzed in detail.