Abstract
The pressure signal of oil pulsating flow is a kind of multi-component signal; in order to realise the effective separation of the multi-component pressure signal and extract its vibration characteristics, the pressure signal was decomposed by Variational Mode Decomposition (VMD). The slope criterion of the centre frequency is proposed to determine the number of components of VMD decomposition, and the method to judge the main components of the signal by energy value is proposed. The Hilbert envelope demodulation analysis was performed on the main components obtained. The results show that the proposed center frequency slope criterion method is effective in the VMD decomposition of the pressure signal of oil pulsating flow, which is used to decompose the pressure signal into 9 components. Four major components of the pressure signal are obtained by the correlation between each component and the pressure signal, and the energy value calculation of each component. The main component frequency of the pressure signal is one time, 6 times, 11 times and 14 times the frequency of the system spindle rotation; these are the sum of two cosine signals of close frequency and have the characteristic of beat vibration.
Highlights
The pressure signal of oil pulsating flow is a kind of multi-component signal; in order to realise the effective separation of the multi-component pressure signal and extract its vibration characteristics, the pressure signal was decomposed by Variational Mode Decomposition (VMD)
Under the influence of 19.53 Hz = 28.32 Hz-8.79 Hz between the two dominant frequencies of mode[1], the typical beat vibration characteristics of 314.5 Hz and 335 5 Hz appear in the component of mode[7]
After verifying the central frequency slope criterion to determine the number of components of VMD decomposition, and the method of energy value to determine the main components of the signal, the pressure signal was decomposed and Hilbert envelope demodulation analysis was carried out by using variational mode decomposition
Summary
The pressure signal of oil pulsating flow is a kind of multi-component signal; in order to realise the effective separation of the multi-component pressure signal and extract its vibration characteristics, the pressure signal was decomposed by Variational Mode Decomposition (VMD). The results show that the proposed center frequency slope criterion method is effective in the VMD decomposition of the pressure signal of oil pulsating flow, which is used to decompose the pressure signal into 9 components. Mizusgina et al.[9] reported a comprehensive study of pulsating flow and obtained the phase mean velocity and turbulence intensity of the fluid from the information measured by an electrochemical method, which only covers 20 cycles for the difficulty concerned in the experiment, which limits the convergence of the results. Non-stationary signal analysis methods, such as the short-time Fourier transform (STFT), Hilbert Huang transform and analytical mode decomposition, have their different problems. The VMD transforms the problem of solving the modal bandwidth into a constrained optimization problem and decomposes every mode around a certain central frequency, which may adaptively understand the frequency domain segmentation of the signal and the effective separation of every component
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