This study investigates the use of a non-pre-mixed resonance igniter for liquid propellant rocket engines, using oxygen and methane. Resonance heating at varying nozzle gap spacing for both oxygen and nitrogen is investigated both experimentally and numerically. High frequency microphone data is used to experimentally determine the operating mode of the igniter. Temperature measured on the outside of the resonator tip is used to evaluate heating performance at specific set points. The Open Source CFD software SU2 is used to create a numerical model, capable of accurately predicting the switch in igniter operating point, as well as the operational parameters leading to the highest rates of thermo-acoustic heating. Ignition attempts show that the separate injection of methane into the combustion chamber causes severe disruption of resonance heating, preventing the mixture from igniting.