Uncertainty estimation in calibration of instruments of model turbine test facility

Abstract

The experimental testing of the reduced scale model turbine is an important phase to obtain the performance characteristics of the prototype because the characteristics are difficult to obtain from theoretical calculations. A specially designed hydraulic test facility following the guidelines of international standards is generally used to obtain the performance characteristics of model turbine. These characteristics are transposable to the prototype turbines. The model turbine test facility is also used for the research and development work by the designers and scientists. The accuracy of the results obtained is entirely dependent on the instrumentation, calibration and uncertainty estimation. In the present study, the instrumentation and calibration procedure of a model Francis turbine test facility is presented by following the guidelines of international electrotechnical commission. The instruments such as flow meter, inlet and differential pressure transducers, torque sensors, angular position sensors and temperature sensors are calibrated using primary and secondary methods. The calibration curves and uncertainties involved in different instruments are obtained and presented. Both systematic and random uncertainties involved in hydraulic efficiency measurements are also presented. The maximum total uncertainty is ±0.15% in the hydraulic efficiency of model Francis turbine at best efficiency point.