Abstract
The never ending process to increase the efficiency of turbine stages introduced an idea to create an axial turbine stage test rig as part of closed loop transonic wind tunnel at Vyzkumny a zkusebni letecky ustav (VZLU). Studying of unsteady flow field behaviours in turbine stages is nowadays essential in the development process. Therefore, the test rig was designed with focusing on possibility of detailed studying of unsteady flow fields in turbine stages. New methodologies and new instrumentations were developed at VZLU and successfully integrated to gain valuable information from experiments with turbine stages. Two different turbine stages were tested during the facility introduction process. The measurement of these two models demonstrated how flexible the test rig is. One of them was an enlarged model of small gas turbine stage. The other was scaled-down model of stage of intermediate-pressure steam turbine. The external characteristics of both models were acquired during experiments as well as the detailed unsteady flow field measurement. Turbine stages were tested in various regimes in order to check the capabilities of the facility, methodology and instrumentation together. The paper presents results of unsteady flow field investigation in the enlarged turbine stage with unshrouded rotor. The interaction of structures developed in a stator with the rotor flow field is depicted and the influence of turbine load on evolution of secondary flows in rotor is analysed.
Highlights
Turbomachinery is a traditional field of research at VZLU
The investigation of unsteady flow field in the unshrouded turbine stage demonstrated how complicated in this case the flow field is
The comparison of flow fields in presented regimes showed, that evolution of the flow in the rotor row is essential for the stage behaviours
Summary
Turbomachinery is a traditional field of research at VZLU. It began with experimental research of flow fields in linear cascades, what is basic task in the turbomachinery. Original methodology [4] was arranged for these experiments It is applicable especially for measurement of complicated periodical structures in small channels of turbines. This is extremely interesting for the following work focused on the research of unsteady flow fields in turbine stages. To be able to study the unsteady measurement it is necessary to place the pressure transducer as near the investigation point in flow field as possible For this reason the probes equipped with pressure transducers mounted in their tips were developed [7]. That the traverse plane is quite far from the rotor trailing edges, the structures could be partially mixed
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