Overall Technologies to Enhance Efficiency Accuracy in Turbines

Transportation and energy production industries strongly rely on improvements in gas turbine performance. The quantification of these improvements is dependent on the accuracy of the measurements performed during testing. An increase of 0.5\% in efficiency is sufficient to secure a new development program worth millions of dollars, but in the case of temperature measurements, uncertainties below 0.5 K are required, which presents a challenge. This work selects heat flux estimation and total temperature measurement uncertainties as major contributors for efficiency uncertainty.

• Heat flux measurements are critical to evaluate the impact on the efficiency. Additionally, thermal fatigue in turbine airfoils defines the life cycle of the engine core. This work performs an estimation of the heat transfer via a simplified numerical model that uses infrared (IR) measurements in the surface of the casing to predict the temperature of the passage wall. The model is validated with real cool-down data of the turbine to yield results within a 10\% of the actual temperature.
• Total temperature measurement suffers from errors due to heat transfer effects in the probe. Two dominant sources of errors are convection and conduction between the thermocouple wires, the probe support, and the flow. These effects can be treated in two different categories: the velocity error, created by a non-isentropic reduction of the flow velocity upstream the thermocouple junction, and the thermal equilibrium effects between the junction and the probe support, involving heat transfer through the wire to the shield and the probe stem due to temperature differences between each component (the so-called \emph{conduction error}). An open jet stand is used to evaluate the effects of velocity error at various Mach numbers. The conduction error is addressed with the design and manufacturing of dual-wire thermocouple probes. The readings from two wires with different length-to-diameter ratios are used to correct for the flow total temperature. This probe yielded a recovery factor of 0.99 +/- 0.01 at Mach 0.6.