Abstract
In the context of improving energy efficiency and fuel consumption of mobile hydraulic equipment, it is important to analyze all the sources of power loss occurring within the hydraulic systems. While plenty of analyses have been performed on the working implements and the main transmission systems, very little attention has been paid to low-pressure (LP) systems until recently. LP systems are required on closed-circuit hydraulic systems to replenish losses, provide cooling flow, and maintain a pilot pressure necessary to operate hydraulic control valves and variable displacement units. It is shown that these circuits, which are often thought to have minimal impact on power consumption, actually cause significant, continuous power loss. A new method of power savings in these circuits is investigated through management of charge pump flow by application of an accumulator-sense pump-unloading (ASPU) valve. This work further proposes the combination of a split LP architecture with an ASPU valve. Three systems are simulated using Simcenter Amesim® and MATLAB/Simulink®. Using realistic duty cycles and unit loss models on a circuit for mobile off-road hydraulic equipment, it is shown that a standard LP system can consume about 5 kW of power. Power savings of up to 65% over a standard LP system are demonstrated by the proposed architecture.
Highlights
Hydrostatic transmissions are powerful, flexible means of power distribution
In the pursuit of minimizing fuel consumption and emissions while maximizing efficiency, attention must be paid to all power consumption in hydraulic systems
LP circuits can contribute to continuous power losses because they are often implemented with a fixed displacement pump, providing constant flow, while excess is normally returned to the tank over a relief valve at system pressure
Summary
Hydrostatic transmissions are powerful, flexible means of power distribution. current state-of-the-art technologies have many opportunities for improvement on overall energy efficiency. Low-pressure systems are a necessary part of closed-circuit hydraulic systems These circuits are required in closed-circuit applications to provide cooling flow and make-up flow to replenish unit losses in the circuit. LP circuits can contribute to continuous power losses because they are often implemented with a fixed displacement pump, providing constant flow, while excess is normally returned to the tank over a relief valve at system pressure. These systems can be viewed as a type of constant-pressure system, given their requirements for maintaining a reference pressure level within the main transmission system
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