Accounting for Uncontrolled Variations in Low-Speed Turbine Experiments
Journal of Turbomachinery
American Society of Mechanical Engineers
MetadataShow full item record
Evans, K., & Longley, J. (2017). Accounting for Uncontrolled Variations in Low-Speed Turbine Experiments. Journal of Turbomachinery https://doi.org/10.1115/1.4036342
It is common to assume that the performance of low-speed turbines depend only on the flow coefficient and Reynolds number. However, when the turbine has an atmospheric inlet and uses unconditioned air, variations in ambient pressure, temperature and humidity are introduced. Whilst it is still possible to maintain the required values for the flow coefficient and Reynolds number, the ambient variations affect additional non-dimensional quantities which are related to the blade speed and gas properties. Generally, these additional non-dimensional quantities are uncontrolled and affect the turbine performance. In addition, thermal effects, which are exacerbated by the use of plastic blades, can cause changes in the blade row seal clearance and these also affect the performance. Therefore to obtain measurements with greater accuracy and repeatability, the changes in the uncontrolled non-dimensional quantities must be accounted. This paper contains four parts. Firstly, it is described how suitable data acquisition parameters can be determined to eliminate short time scale facility unsteadiness within the measurements. Secondly, by the analysis of models, the most appropriate forms for the additional non-dimensional quantities are obtained. Since the variations in the uncontrolled non-dimensional quantities affect repeatability the size of the effect on the turbine performance is quantified. Thirdly, a best-fit accounting methodology is described which reduces the effects of the uncontrolled non-dimensional quantities on turbine performance provided sufficient directly related measurements are available. Finally, the observations are generalised to high-speed turbomachines.
turbines, turbochargers, accounting, blades, flow (dynamics), Reynolds number, pressure, temperature, turbomachinery, data acquisition
The authors are grateful to Rolls-Royce plc who supported this work through SAMULET Project 1, in collaboration with the TSB (Ref.: AB265C) and the EPSRC (Ref.: EP/H001395/1), and for their permission to publish.
External DOI: https://doi.org/10.1115/1.4036342
This record's URL: https://www.repository.cam.ac.uk/handle/1810/264098