GB644955A - Improvements in or relating to elastic fluid compressors - Google Patents

Abstract

644,955. Axial-flow and centrifugal compressors. POWER JETS (RESEARCH & DEVELOPMENT), Ltd. July 6, 1948, No. 18173. [Class 110(i)] In a multi-stage dynamic compressor having an intercooler, surging at low output is prevented by varying the degree of cooling in accordance with the load so that the ratio of the densities of the compressed fluid after and before cooling is increased when the load decreases and is decreased when the load increases. The temperature of the compressed fluid could be sub-atmospheric at part load, but preferably it is arranged to be approximately atmospheric at the lowest load and progressively higher at greater loads. In the embodiment shown, in which an intercooler 4 is interposed between two axialflow stages 1 and 2 mounted on a common shaft 3, the flow of coolant is controlled by a valve 8 in accordance with the speed of the shaft by means of a centrifugal or other speed governor 5. The governor may be linked to the valve by electrical, hydraulic or mechanical servo mechanism. In a modification, the valve 8 is operated by a capsule responsive to the pressure at the outlet of the low pressure stage 1. As a further alternative. the control may be responsive to mass flow. Instead of the valve 8, the pump supplying the coolant may be controlled. The compressor stages may be on separate shafts, the relative speed of which may be varied. The invention is applicable to centrifugal compressors. According to the Provisional Specification, the control may be in accordance with any two of the above-mentioned variable factors.