Development research of reflection-absorption compound type fluid pulsation attenuator
Based on the disadvantages analysis of the existing fluid pulsation attenuator, two reflection-absorption compound type of fluid pulsation attenuators which are both composed of a chamber and a mass-spring-damping system are developed: in-line reflection-absorption compound type of fluid pulsation attenuators (in-line RAFPA) and side-branch reflection-absorption compound type of fluid pulsation attenuators (side-branch RAFPA). The transfer matrix models of the two attenuators are established as well as expansion chamber attenuator and Helmholtz resonator. Based on the transfer matrix model, the transmission loss of the four attenuators is given out to evaluate their attenuation characteristic. The attenuation characteristic comparisons of in-line RAFPA with expansion chamber attenuator and side-branch RAFPA with Helmholtz resonator are carried out respectively. And the effect of the mass-spring-damping system to in-line RAFPA and side-branch RAFPA is investigated. The simulation reveals the two reflection-absorption compound type of fluid pulsation attenuators have better attenuation characteristic and are more compact than expansion chamber attenuator and Helmholtz resonator.
Reduction of axial piston pump pressure ripple
Abstract The reduction in source flow ripple in hydraulic systems is the most effective method of reducing pump-generated pressure ripple and system noise. This paper describes reductions in axial-piston pump delivery flow ripple achieved using a novel timing mechanism which is inherently speed, flow and pressure sensing. Fixed-speed tests have shown that the mechanism can significantly reduce axial-piston pump delivery flow ripple over a wide range of delivery pressures and pump displacements. Furthermore, the reduction in pressure ripple achieved with the mechanism has been shown to contribute towards reductions in overall air-borne noise levels of up to 6 dB in a simple system. A simulation model has been produced to predict the behaviour of the prototype mechanism. The model has been compared with the measured delivery flow ripple and achieves good agreement.
Design of reinforced concrete lining in pressure tunnels, considering thermal effects and jointed rockmass
Abstract Jaeger's theory (Jaeger, Rock Mechanics and Rock Engineering , Cambridge University Press, 1972) of the design of the lining for a pressure tunnel applies to a tunnel located in an isotropic, homogeneous and elastic medium. The theory is derived from the elasticity equations for the plane stress condition. In this paper, Jaeger's theory is extended to a plane strain situation. Also included is a discussion of the effects of a uniform increase (or decrease) in the lining temperature, jointed rockmass, cracking of the tunnel lining, and cracking of the rockmass around the opening. Tables are presented for the modulus of subgrade reaction for various rockmass conditions and for rock sharing pressures for various lining conditions. The reduction factor to include the effect of joints in rockmass is derived by the analysis of a numerical model of the lined tunnel by the finite-infinite-interface element method.