Atomic Layer Thermopile Film for Heat Flux Measurement in High Speed and High Temperature Flows
thesisposted on 03.01.2019 by Lakshya Bhatnagar
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
This work seeks to apply the novel heat flux sensor called as the Atomic Layer Thermopile to measure high frequency heat flux in high speed and high temperature flows found in Gas Turbine combustors. To achieve this the sensor must be able to survive the harsh environment of high temperature and high pressure. To have any confidence in our measurement, it is also imperative that there are tools available for precise estimation of the measurement uncertainty. This works strives to achieve these objectives by developing calibration techniques for uncertainty estimation using both exposure to radiation and in convective environments by calibrating against power input in steady state flow and transient heat flux calculated using wall temperature measurement. The response of the sensor is then investigated in high speed flows by measuring the heat flux inside a supersonic nozzle when exposed to shock waves. The shock waves are generated using a fast throttle valve located at the entrance of the supersonic nozzle by generating sudden rise in pressure. Lastly a numerical study is carried out to design a cooling system that will allow the sensor to survive in high temperature conditions of 1000°C while the sensor film is maintained at 50°C. A one-dimensional model is used to provide initial design parameters and then a two-dimensional axisymmetric conjugate CFD analysis is carried out to obtain the desired geometry that can meet the design conditions. A static structural analysis is also carried out on this geometry to ensure that it will be able to survive and avoid distortion under the operational pressure required for providing the desired coolant mass flow.