Noise—it’s an all-too familiar problem to the fluid power industry. Besides negatively affecting hearing and impairing effective communication, excessive noise can increase mechanical fatigue and reduce component life. In short, excessive noise detracts from the attractiveness of existing fluid power products and can be an entry barrier for this technology into new markets and applications.
Solutions are on the horizon, however, based on research aimed at improving noise control in fluid power systems by passive means. A research team led by Georgia Tech Professor Ken Cunefare, with funding provided through the Engineering Research Center for Compact and Efficient Fluid Power (CCEFP), is seeking solutions to the reduction of noise and vibration by integrating engineered compliant materials into existing components and technologies. The use of these materials is also expected to help reduce the size of noise control devices for fluid power. Their work has significant impact for the fluid power industry as it strives to comply with regulatory requirements, answer to designers’ priorities for noise and size reduction, and meet customer expectations.
Fluid-borne noise is generated by numerous components within hydraulic systems, most significantly by pumps, and can couple to structures, causing vibration and air‐borne noise. The high speed of sound in hydraulic fluid, along with the low fundamental frequencies of pumps, results in wavelengths of fluid-borne noise that are much longer than the practical size of common noise control components. The current technology for reducing fluid-borne noise involves both the use of pressurized, gas‐filled bladders for adding compliance to fluid power systems, and integrated design features that address such noise sources as cavitation and structural vibration. Pressurized bladders are used in commercially-available in‐line silencers (one such silencer is used as a benchmark in this research) and in accumulators which act as low‐pass filters. In contrast, the research approach in this project is unique in its application of a voided, engineered, compliant lining to noise control devices for fluid power systems.
Such a lining has already been put to the test. The research team has constructed a prototype silencer that incorporates a voided polymer lining, which has the same basic effect as a pressurized liner. In experimental tests, the prototype silencer exhibits 25 dB of transmission loss from 200‐3000 Hz, and performs comparably to a similarly‐sized commercial bladder-style silencer. The team has also constructed other noise control devices that incorporate this lining: a Helmholtz resonator, a tuning coil, and a Quincke tube. The prototype Helmholtz resonator with the voided lining is two orders of magnitude smaller than an unlined resonator of the same resonance frequency. To facilitate their work, the team has constructed a test rig for measuring the acoustic performance of hydraulic two‐port devices. The test rig has the capability of measuring the transmission loss of two‐port hydraulic components including, but not limited to, silencers, accumulators, hoses, branch resonators, and valves.
Professor Cunefare and his team are interested in working with companies who may have applications in mind for their research findings. For further information, see www.ccefp.org, project 3B.1, or e-mail Dr. Stelson, CCEFP Director (kstelson@umn.edu) or Dr. Cunefare (ken.cunefare@me.gatech.edu).