1990-09-01

Comparison of Analytical and Experimental Investigations of a Hydraulic Multi-Circuit Sequential Apportioning System 901553

In conventional hydraulic systems, a fixed or variable displacement pump is used to supply a number of separate branches of a circuit, each with potentially different flow rate and pressure requirements which can vary widely with time. Conventional approaches to distributing the flow to the individual branches generally involve valves controlling the flow to each individual branch. This can lead to significant energy losses from valve throttling, depending upon the actual flow and pressure requirements of each part of the circuit.In the system discussed in this paper, the entire output of the pump is quickly and sequentially directed to each individual branch of the circuit. The average speed of the actuator is controlled by the proportion of time that the pump flow is being directed to that branch. A small accumulator is incorporated in each branch of the circuit to smooth the velocity of the actuator. This concept essentially eliminates throttling losses at the valves used to control actuator speed in conventional systems.This multi-circuit, sequential apportioning system has been investigated both analytically and experimentally. Computer simulations investigating system efficiency, accumulator performance, hydraulic shock, and overall system dynamic performance have been conducted. The system's calculated efficiency was compared to that of a conventional system operating with the same load and speed conditions. The sequential apportioning system shows the largest efficiency improvement in systems which have demands of high flow with low pressure in one branch and, simultaneously, low flow with high pressure in the other branch or branches. The actual improvement in efficiency is highly dependent upon the specific flow and pressure requirements.Both detailed and simplified models have been developed, and show good correlation when compared with experimental work. Both simulation and experimental results verify that the system is applicable, and especially attractive for applications where efficiency is very important and the response and accuracy requirements are less stringent.

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