Microsphere in hollow core photonic crystal fiber as temperature probe for hydrogen combustors.

Hydrogen combustors could provide a carbon neutral way to power our homes and reduce our environmental impact. However, when the combustors operate at high efficiency, the burner flame could arrive in regions not designed to handle high temperature, leading to expensive damage (flashback). The temperature inside the combustor must be measured to provide an early warning for this phenomenon. In this contribution, a microsphere-hollow core photonic crystal fiber temperature measurement system is explored, both theoretically and experimentally. The device is self-calibrating, and features a high spatial resolution, as the position of the microsphere probe can be controlled with micrometric precision through manipulation of the fiber-coupled laser beams. The temperature is obtained by probing the local gas viscosity through analysis of the motion of the microsphere, which is interpreted by monitoring the transmitted light. The system has pressure control provided by a vacuum pump, which allows tuneable temperature sensitivity.