Abstract
This paper presents the experimental characterization of the vibroacoustic fields and the evaluation of noise performances of hydraulic pumps. Research on hydraulic pump noise has traditionally focused on the fluid-borne noise sources, and very often the analyses of vibration and noise have been performed focusing on a few local points. This trend results in the lack of investigation on the overall behaviors of vibroacoustic fields of hydraulic pumps, and it has been one of the obstacles to understand the complete mechanisms of noise generation. Moreover, despite the existence of the ISO standards for the determination of noise levels, diverse metrics have been used for the evaluation of noise performances of the pumps, but the adequacy of these metrics has not been carefully examined. In this respect, this paper aims at introducing a way to characterize and interpret the measured vibroacoustic field and providing proper methods which are also capable of applying the ISO standards for the fair assessment of pump noise performances. For the characterization of the vibroacoustic field, operational deflection shapes (ODS) and corresponding radiated sound fields are visualized at harmonics of the pumping frequency by using a spectral analysis. Observations are made regarding the motions of the pump and its mounting plate and the resultant radiated noise, depending on the frequency, as well as their correlation. A numerical analysis using the Rayleigh integral equation is also performed to further investigate the contribution of the mounting plate motion on the noise radiation. For the evaluation of noise performance, two different units are tested at multiple operating conditions, and comparisons are made based on their measured sound power levels (SWLs) and sound pressure levels (SPLs). The results emphasize the importance of SWL measurement for the fair noise performance evaluation, and the two methods are proposed as practices to determine the minimum number of measurement points for practicability and to have reliable sound power determination for hydraulic pumps.
Highlights
Excessive acoustic noise and vibrations are important detrimental aspects for fluid power systems, and positive displacement machines are known to be the dominant source of noise and vibration
Most of the successful solutions are based on the minimization of the flow/pressure ripple at the delivery port, which is often considered as the main source of fluid-borne noise (FBN)
The analysis is accomplished under the assumption that the noise and vibration do not change during the steady-state operation, and the results prove that this assumption is valid
Summary
Excessive acoustic noise and vibrations are important detrimental aspects for fluid power systems, and positive displacement machines (i.e., hydraulic pumps and motors) are known to be the dominant source of noise and vibration. Energies 2020, 13, 6639 an important metric to evaluate the unit performance along with hydraulic efficiencies parameters (i.e., volumetric and mechanical efficiency) This is confirmed by the fact that the noise level is often reported in the specification sheets of hydraulic pumps. As pertains to external gear pumps, similar analyses have been made by proposing different porting grooves [13], alternative gear profiles spamming from standard involute [14,15] to non-involute [15,16,17,18], and considering the effect of fluid compressibility [19,20] From these analyses, the minimization of the pressure ripples at the delivery port has been proved to be effective on the noise reduction in the system level. This was widely discussed by Edge [21], who showed a case where no change in the noise level is observed even with a large reduction in the amplitudes of the pressure ripple
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