Cooled Pressure Probes Design Methodology for Harsh Environment Applications

In an effort to extend the knowledge around combustion instabilities while supporting the development of more performant combustion control systems, the availability of fast-response pressure measurement devices able to operate in the harsh environment of gas turbine combustors is fundamental. The severe heat load at which they are submitted forces the adoption of a cooling layout in order to keep the probe material well below its maximum operating temperature. This constraint becomes even more critical when the fragile sensing element of conventional off-the-shelf piezo-resistive fast-response pressure transducers is considered.

The present paper discusses in detail the concept and design of a water-cooled fast-response wall-static pressure probe intended for measurements in the combustion chamber of gas turbines.

The proposed design approach is structured upon three main steps. In the first step, different reduced order correlations for convective and radiative heat transfer are used to derive the heat load at which the measurement device is submitted. In the second part, a quasi-2D conjugate heat transfer model is developed and operated through the application of the boundary conditions computed in the previous step. The model is based on empirical correlations and computes representative global cooling performance parameters for different cooling layouts and coolant mass flow rates. In the final step, the obtained design candidate is further validated by means of state-of-the-art fully 3D conjugate heat transfer numerical simulations performed on a probe geometry characterized by an increased degree of complexity. At its final extent, the present paper describes and validates a complete and robust methodology for the design of cooled fast-response pressure probes.