Power Transfer Units for Aircraft Hydraulic Systems.

摘要

This report presents the results of a program to develop an advanced design hydraulic power transfer unit. The purpose of the program was to select and develop a power transfer unit with performance and stability improvements over that of the conventional rotary-piston type transfer units. The program was conducted in five phases: configuration selection, critical element testing, design, fabrication and prototype testing. The last three phases were repeated to produce two design improvements of the selected configuration. The selected configuration was an oscillating spool type motor -- pump which eliminated the power conversion, from linear to rotary back to linear, of the conventional rotary units. The first unit developed was a two cylinder configuration which exhibited a lockup mode at low flows. A second unit with three cylinders was developed with the design based on analysis accomplished on an analog computer. This unit exhibited three modes of operation as the flow rate increased from zero to maximum. The modes resulted from varying degrees of synchronization between the three pistons. This unit was then modified to provide a mechanical synchronize which resulted in a large improvement in stability at low flows. Minor areas of the basic design need to be explored to provide additional improvements.