Pelton Turbine Runner Cup Damping via Movable Bodies
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Solution Overview
Problem
Pelton turbine impellers face cyclic loading and resonance issues due to natural vibration and low damping, which can lead to unwanted resonance effects and reduced design safety margins, especially during manufacturing variations.
Innovation Solution
Incorporating cavities in the impeller buckets with damping means, such as movable bodies or high viscosity fluids, to counteract bucket vibrations and increase damping, thereby reducing resonance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the natural frequency of the buckets is set to be sufficiently uncritical during design, then the safety margin against resonance is improved, but manufacturing variations can still cause frequency shifts that reduce this safety margin
Solution Approach 1:
The patent changes the physical parameters of the bucket by introducing cavities filled with damping material or movable bodies. This modifies the vibrational characteristics and damping properties of the bucket, making the system less sensitive to frequency shifts caused by manufacturing variations. The damping material or movable bodies absorb vibrational energy and reduce the amplitude of resonance, thereby maintaining reliability despite manufacturing tolerances.
2Reliability
If damping means are added to the impeller buckets, then the damping effect and resistance to vibration are improved, but the device complexity increases
Solution Approach 1:
The patent utilizes porous or cavity-based structures within the bucket design. These cavities are filled with damping material such as viscoelastic substances, foam, or granular materials. The porous/cavity structure provides effective damping while maintaining a relatively simple overall bucket geometry. The damping material can be easily integrated during manufacturing, avoiding complex mechanical damping mechanisms.
Solution Approach 2:
The damping means in the patent are designed to function automatically without external control or additional components. Movable bodies within the cavities self-adjust based on vibration patterns, and damping materials inherently dissipate vibrational energy through their material properties. This self-service characteristic reduces the need for complex control systems or adjustable mechanisms, thereby limiting the increase in device complexity.
3Reliability
If cavities are introduced in the cup root region, then the damping of cup vibration is improved, but the structural strength of the cup roots may be reduced
Solution Approach 1:
The patent employs composite construction by combining the cavity structure with damping materials that have complementary mechanical properties. The cavity walls maintain structural strength while the filling material provides damping. This composite approach allows the cup root to achieve both high strength and high damping characteristics, as the two materials work together synergistically - the rigid cavity structure carries loads while the damping material dissipates vibrational energy.
Solution Approach 2:
The damping material or movable bodies are nested within the cavities of the cup root structure. This nested configuration allows the damping function to be integrated within the existing structural geometry without significantly altering the external dimensions or load-bearing pathways of the cup root. The cavity walls maintain structural integrity while containing the damping elements, thus preserving strength while adding damping functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively dampens bucket vibrations and reduces resonance amplitudes, enhancing safety margins and structural integrity while maintaining sufficient strength and robustness against defects.
Implementation Method 1
The means in cavity 2 must therefore have a damping effect. The inventor recognized that such means can consist of movable bodies that rub against each other when the cup root deforms, thus providing effective damping.
Implementation Method 2
Additionally, the cavity can be filled with a liquid. The use of a liquid with high viscosity can further enhance the damping.
Implementation Method 3
This cup vibration can be counteracted by integrating a movable body into cavity 2, which, through the jet's intervention, can be set into a periodic motion opposite in phase to the cup vibration.
Data Source
Figure 1~2
AI summary
The invention relates to a runner for a Pelton turbine, comprising a runner hub and a plurality of cups (1) with in each case a cup root, wherein each cup (1) is fastened on the runner hub by means of the cup root, and wherein each cup has a cavity (2) which encloses means which are configured in such a manner that they passively counteract an occurring cup oscillation, wherein the means comprise at least one body which is movable with respect to the cavity (2).