Patent attributes
A pressure sensor (52) for a harsh environment such as the combustion chamber (58) of a gas turbine engine (50). The pressure sensor includes an acoustic waveguide (60) having a sensing portion (66) exposed to the combustion gas in the combustion chamber. Modulations in an acoustic signal passing through the acoustic waveguide are sensed and correlated to pressure fluctuations in the combustion gas. The sensing portion of the waveguide includes a core acoustic waveguide element (42) covered by a coating material (44). The coating material not only protects the core from the harsh environment, but it also improves the efficiency of the transfer of energy from the combustion gas into the waveguide because it provides a stepped transition from the acoustic impedance of the gas to the acoustic impedance of the core material. The protective coating may have a plurality of layers (46, 48) and/or it may include a graded material (78, 80) having an acoustic impedance value that varies across its depth.
