Flow-Adaptive Measurement Sequence for Pneumatic Probe Measurements
Published on 1. December 2017
Book
Paperback/Softback
181 pages
978-3-8439-3360-5 (ISBN)
Description
Subject of the work presented here is a flow-adaptive measurement grid algorithm developed for one-dimensional and two-dimensional flow field surveys with pneumatic probes in turbomachinery flows. The algorithm automatically determines the distribution and the amount of measurement points needed for an approximation of the pressure distribution within a predefined accuracy.
All operations of the algorithm are based on transient measurements, which are conducted back and forth in one spatial direction within the measurement domain. The dynamic response of the pressure measuring system is disregarded during the traverses, which serve to detect changes in the pressure field. A correction to take account of the dynamic response of the pressure measuring system is implemented in the algorithm. The dynamic response is compensated by deconvolving the transient measurement data using the information embedded in both transient measurements. By deconvolution of the transient measurement data, the performance of the flow-adaptive algorithm becomes largely independent of the transient traversing speed and the geometry of the pressure measuring system. Knot insertion and removal strategies are incorporated in order to reduce measurement points and increase robustness toward differing flow field conditions. The performance of the algorithm is demonstrated for 1D and 2D flow field surveys with a pneumatic five-hole probe in an annular cascade wind tunnel. The pressure distribution in the measurement domain is approximated within a predefined accuracy, based on the measurement uncertainty of the pressure transducers. The application of the algorithm shows a significant reduction in the number of measurement points. Compared to the uniform measurement grids, approximately 30% fewer measurement points are required for 1D and 20% fewer points for 2D flow field surveys with the identical spatial resolution. Consequently, measurement time is reduced by at least 19% for 1D measurements and by at least 7% for 2D measurements with the same spatial resolution.
All operations of the algorithm are based on transient measurements, which are conducted back and forth in one spatial direction within the measurement domain. The dynamic response of the pressure measuring system is disregarded during the traverses, which serve to detect changes in the pressure field. A correction to take account of the dynamic response of the pressure measuring system is implemented in the algorithm. The dynamic response is compensated by deconvolving the transient measurement data using the information embedded in both transient measurements. By deconvolution of the transient measurement data, the performance of the flow-adaptive algorithm becomes largely independent of the transient traversing speed and the geometry of the pressure measuring system. Knot insertion and removal strategies are incorporated in order to reduce measurement points and increase robustness toward differing flow field conditions. The performance of the algorithm is demonstrated for 1D and 2D flow field surveys with a pneumatic five-hole probe in an annular cascade wind tunnel. The pressure distribution in the measurement domain is approximated within a predefined accuracy, based on the measurement uncertainty of the pressure transducers. The application of the algorithm shows a significant reduction in the number of measurement points. Compared to the uniform measurement grids, approximately 30% fewer measurement points are required for 1D and 20% fewer points for 2D flow field surveys with the identical spatial resolution. Consequently, measurement time is reduced by at least 19% for 1D measurements and by at least 7% for 2D measurements with the same spatial resolution.