Fibre Optic Interferometric Heat Transfer Sensors for Transient Flow Wind Tunnels

A new type of heat transfer sensor has been developed in which the sensing element is a short length (∼3mm) of single mode optical fibre acting as a Fabry-Perot interferometer. The reflected light intensity follows a periodic transfer function, and the phase change is proportional to the sensor’s spatially averaged temperature. We present results from three optical fibre sensors embedded as calorimeter gauges in a ceramic nozzle guide vane end wall model exposed to a transient heat flux of ∼100 kWm⁻² in the Isentropic Light Piston Facility at DRA Pyestock Famborough, and validated by comparison with previous data from platinum thin film resistance gauges. The optical sensors exhibit high spatial resolution (∼5μm), high heat transfer resolution (∼1kWm⁻²), and wide temperature measurement bandwidth (100kHz) with intrinsic calibration. No electrical connections to the measurement volume are required and multiplexing is possible.