Diesel Progress North American

HYDRAULIC HORIZONS This hydraulic silencer prototype — one of several developed by the CCEFP research team — was designed with a low component count and microvoided polymer lining, which is intended to help to keep the cost to manufacture and maintain low.

systems could require additional components. The addition of such components could potentially cause too many difficulties in packaging them into working systems, thus eliminating them as an option.

There are several techniques that can be used to reduce fluid pressure fluctuations or pressure ripples. In its research, the CCEFP determined that passive noise control is the best option, as it focuses on engineered, functionally graded materials and improved design based on modeling of these materials and their effects.

Most of the CCEFP team’s effort thus far has focused on using a hydraulic silencer to control pressure fluctuations, which involves the use and design of a microvoided polymer lining. The silencer presents several advantages over currently employed nitrogen-bladder silencers in that it offers relative ease of construction and was designed with a low component count, which helps to keep the cost to manufacture and maintain low, Cunefare said. Additionally, because the silencer is porous, it can reduce static pressure loss across the silencer compared to the standard bladder unit.

The project, which Earnhart said began in fall 2006, is currently in the prototype stage. According to Cunefare, the team has been conducting testing to determine the ability of the silencers to control pressure fluctuations by install-ing them on a test rig located at the Georgia Institute of Technology. As the team goes forward, it said its goal is to focus on engineering structural materials for passive noise control that will be implemented on other new components being developed by the CCEFP. Examples will include the HCCI free-piston engine and the high-speed rotary valve.

“I see the application of this technology becoming more and more significant in coming years as hydraulic hybrids themselves penetrate the market more,” said Cunefare. “This will then create a need for reduced noise and vibration signatures in those vehicles.” dp