Abstract
The motivation of this paper is the continual development of the blades for the last stage of the steam turbine. The biggest problem is the slenderness of such blades and the extreme sensitivity to aeroelastic vibrations (flutter) caused by the instabilities present in the flow. This experimental research is dealing with the aeroelastic binding of the moving blades located in the blade grid with the flow field and vice versa. A parallelogram is used to ensure one order of freedom of the blade. The grid has five blades in total, three of them are driven by force control using three shakers. The deviation as well as force response is measured by strain gauges and dynamometers. The flow field statistical as well as dynamical characteristics are measured by optical method Particle Image Velocimetry. The grid is connected to the blow-down wind tunnel with velocity range up to 40 m/s. The aeroelastic binding is investigated in dependency on used actuation frequency and maximal amplitude (the intensity of force actuation) and on different Reynolds numbers. The flow field and the wake behind each individual blade are studied and the maximal interaction is examined for individual inter-blade phase angle of the grid.
Highlights
This work was established as a responce to a necessary need to further improve the efficiency of the steam energy conversion in the last stages of the steam turbine
The experimental or numerical investigation of the flutter in low pressure turbine (LPT) blades is in the center of interest for many research groups which have been still dealing with turbomachinery blade dynamic stability
The blade cascade was tested during four different tunnel outlet velocities, the main focus is set to 40 m/s in this article
Summary
This work was established as a responce to a necessary need to further improve the efficiency of the steam energy conversion in the last stages of the steam turbine. The experimental or numerical investigation of the flutter in low pressure turbine (LPT) blades is in the center of interest for many research groups which have been still dealing with turbomachinery blade dynamic stability. Nowinski’s work [3] is based on unsteady pressure measurement made along the test section outer wall with the goal to eliminate flutter in LPT blades. Tsymbalyuk et al [2] has investigated the blade dynamic stability His experiment is based on selfexcited vibrations of the airfoil cascade using the airfoil suspension system which has two degrees of freedom – the displacement and the rotation. Results of ref. [4] revealed that the flow is mainly affected by the changing wing angle and the effect of displacement is rather small
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