Data Uncertainty Analysis Of Turbine Testing On The Short-duration Facility

The short-duration facilities have been widely appreciated, due to its advantages compared to traditional facilities, such as lower construction and operating costs, simplicity of operation, lower requirement to human resources and power energy, and so on. Accurate assessment of measurement uncertainty and optimizing of experiment scheme are prerequisite for any experiments. They are also beneficial to promote accuracy and reliability of short-duration turbine tests. In this paper, measurement uncertainty of short-duration turbine test has been studied. Performance test data including isentropic efficiency, inlet mass flow rate are calculated with a proper uncertainty model adopted by ASME. Furthermore, influences of transient-effect and the correlated items in bias uncertainty on the measurement uncertainty of test data have been analyzed. Test parameters influence sequence on the turbine test uncertainty has been studied to search the better experiment scheme to reduce the measurement uncertainty. The main contents of this paper are as follows:1) Quantitative analysis of measurement uncertainty has been performed on the short-duration turbine test. The results show that the short-duration facility can meet the accuracy requirement and the uncertainty caused by transient effect in short-duration facility is less than 1.12% of the total measurement uncertainty. The correlated bias uncertainties of the pressure and temperature have a great influence on the test uncertainty. The inlet Mach has the largest influence on the test uncertainty among the dimensionless parameters.2) Calibration and detailed measurement uncertainty analysis of temperature and pressure have been conducted. The static characteristics of sensors are obtained by traditional calibration schemes. The shock tube is applied to achieving dynamic response characteristics of thermocouples. The influence of the thermocouple dynamic characteristics on the measurement uncertainty of test results has been analyzed. The analysis result shows that the thermocouple in use can meet the requirement of temperature dynamic measurement.3) The question why the turbine inlet Mach has a large influence on the test uncertainty has been analyzed. While the inlet Mach number is very small, the dynamic pressure is extremely small relative to the full scale output of absolute pressure sensors, which would make exact value of the dynamic pressure very difficult to be obtained. Therefore, the test data uncertainty would be larger than estimated. Based on the measurement uncertainty requirement of HB 7081-94, measurement uncertainties of test data on various inlet Mach conditions have been calculated to look for the critical inlet Mach. If the inlet Mach is lower than the critical Mach, an optimized measurement plan should be made.4) An optimized measurement method of mass flow rate and it’s uncertainty analysis are presented. Differential pressure sensors are utilized to measure dynamic pressure. For the operating condition when the inlet Mach number is 0.158, uncertainty analysis results indicate that the values of efficiency and mass flow rate measurement uncertainty are reduced by 58% and 73% respectively, when the optimized experiment scheme is adopted. And the measurement uncertainties used the optimized measurement plan will not increase when the Mach number increases. Further study shows that the optimized plan should be adopted to measure the flow rate when the Mach number is less than 0.158.