Patent ID: 7708461

Claim:
A gas or steam turbine comprising: a flow duct; a flow duct wall having inner and outer surfaces, the flow duct wall surrounding and defining the flow duct; and a measurement device, comprising: a transmission/reception unit comprising: a transmitter to transmit an ultrasonic pulse through the outer surface of the flow duct wall which faces the transmission/reception unit, the ultrasonic pulse being transmitted into the flow duct wall; and a receiver to receive a reflected fraction, that was generated from the ultrasonic pulse reflecting from the inner surface of the flow duct wall, the inner surface facing away from the transmission/reception unit; a temperature unit to determine a temperature for the outer surface of the flow duct wall; and an evaluation unit comprising: a determination unit to determine a transit time of the ultrasonic pulse through the flow duct wall; and an assignment unit to assign a temperature to the inner surface of the flow duct wall based on the temperature for the outer surface of the flow duct wall and the transit time, wherein the transmission/reception unit comprises at least one sound transducer, and at least one acoustic waveguide is positioned between the at least one sound transducer and the flow duct wall to separate the transmission/reception unit from the flow duct wall.