Method for determining cavitation bubble separation point of runner blade through external characteristic indexes

Abstract

The invention discloses a method for determining a cavitation bubble separation point of a runner blade through an external characteristic index. According to the characteristics that an energy fluctuation signal at a tail water taper pipe of a hydraulic mechanical model is basically not changed along with the change of a cavitation coefficient before cavitation bubble separation of a hydraulic mechanical runner blade occurs, and the energy fluctuation signal at the tail water taper pipe of the hydraulic mechanical model is suddenly increased along with the reduction of the cavitation coefficient after the cavitation bubble separation occurs, mathematical statistical analysis on the energy fluctuation signal is carried out at the tail water taper pipe of the hydraulic mechanical model, the dispersion change of the energy fluctuation signal sequence at the tail water taper pipe of the hydraulic mechanical model under different cavitation coefficients is evaluated by a method for calculating the random uncertainty of the energy fluctuation signal at the tail water taper pipe of the hydraulic mechanical model, and the monotonicity change of the energy fluctuation at the tail water taper pipe of the hydraulic mechanical model is added, the corresponding criterion provided by the invention can be used for judging whether the cavitation bubble separation phenomenon of the hydraulic mechanical runner blade occurs or not, so that a basis is provided for predicting the service life of the runner blade.

Description

technical field [0001] The invention relates to a method for determining the separation point of cavitation bubbles of runner blades through external characteristic indexes. Background technique [0002] With the gradual improvement of users' requirements for the stability of hydraulic machinery, ensuring the safe and stable operation of hydraulic machinery in the state of no runner blade cavitation, especially without serious cavitation has become the key to assess the operating state of the unit and predict the failure of the runner blades. an important indicator. [0003] Runner blade cavitation is the process of formation, development and collapse of vapor or gas cavities (bubbles) inside the fluid or on the fluid-solid interface when the local pressure in the fluid decreases. It is a phase change process between fluid and gas, including There are three stages of vacuole formation, development and collapse. The cavitation stage will be accompanied by a substantial incr...

AI Technical Summary

Problems solved by technology

[0006] At the current level of technology, it is impossible to observe and confirm whether there are cavitation bubbles on the runner blades and whether the cavitation bubbles have detached from the attachment of the blade surface on the prototype machine. Observe the cavitation bubbles on the runner blades through the transparent tailwater cone section under the source, and use this as a basis to infer the cavitation of the prototype under the same cavitation coefficient

Since the state of cavitation bubbles in the model test process is completely carried out by manual visual inspection, there is no uniform and quantifiable standard. As a result, the determination of whether the cavitation bubbles on the runner blades have detached from the attachment on the blade surface depends on the observer and the observation position. There are great differences due to different factors, which will affect the accuracy of the evaluation of the cavitation degree of the runner blades, and will most likely cause unpredictable negative effects on the safe and stable operation of hydraulic machinery.

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