The measurement of unsteady total temperature is of great interest for the examination of loss mechanisms in turbomachinery with respect to the improvement of the efficiency. Since conventional thermocouples are limited in frequency response, several fast-response total temperature probes have been developed over the past years. To improve the spatial resolution compared to these existing probes and maintaining a high temporal resolution, a new fast-response total temperature probe has been developed at the Institute of Aircraft Propulsion Systems (ILA), Stuttgart, Germany in cooperation with Berns Engineers, Gilching, Germany. The design of the probe allows a sensitive measuring surface below 1 mm2. A detailed insight into the design of the probe, the measurement principle, the calibration process, and an estimation of the measurement uncertainty is given in the present paper. Furthermore, to prove the functionality of the probe, first experimental results of a simple test bed and of area traverses downstream of the first rotor of a two-stage low pressure turbine are presented. It is shown, that the new probe is capable of detecting rotor characteristic effects as well as rotor-stator-interactions. In addition, a hot-spot is investigated downstream of the first rotor of the turbine, and the findings are compared to the effects known from the literature.
Computational fluid dynamics have become important in turbine design, because experimental tests can easily become very expensive and time consuming. The industrially used two-equation turbulence models have weaknesses in predicting the Reynolds stress anisotropy in complex flows. The free stream Reynolds stresses influence transition and separation on turbine airfoils and vice versa. Higher-order models are supposed to improve numerical prediction quality. For development and validation of these models, a good understanding of the Reynolds stress distribution is required. Therefore the full Reynolds stress tensor and its anisotropy are experimentally investigated in a two-stage low pressure axial turbine. The Reynolds stresses are resolved from 3D hot-film probe area traverses downstream of the first vane at three Reynolds numbers from 40,000 to 180,000, related to vane 1. Surface thin film gauge measurements on the suction side of the vane are used to determine transition and separation. The size of the separation bubble on the late suction side and the progress of transition vary with Reynolds number. This influences the Reynolds stress elements to different extents and thus the Reynolds stress anisotropy downstream of the vane.
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