Dynamic Characteristics of a Pressure-Compensated Inlet-Metered Pump

Abstract

Pressure-compensated pumps are routinely used for supplying fluid power for hydraulic control systems. These pumps traditionally exhibit significant overshoot and oscillation before reaching a steady-state pressure condition, thus requiring the use of downstream safety valves to prevent over pressurization. In addition to over pressurizing the hydraulic control system, the response of the traditional pressure-compensated pump often induces excessive noise and creates instability for other components within the system. In this paper, a nontraditional pressure-compensated hydraulic pump is studied based upon the paradigm that has been offered by diesel-engine technology. This technology uses an inlet-metered pump to provide pressurized fuel for the high-pressure, fuel-injector rail. The analysis of this paper shows that a system of this type may be used to produce a first-order pressure response with no overshoot and oscillation, and that the characteristic time constant and settling time may be designed by specifying parameters that are identified in this research. The problem of cavitation damage is also discussed based upon preliminary testing done at the University of Missouri, and it is suggested that by using hardened machine parts cavitation damage may be prevented in these machines. In conclusion, this paper shows that continued development of the inlet-metered pump may be warranted for those applications where pressure overshoot and oscillation cannot be tolerated due to safety, noise, or other dynamical considerations.