GB720526A - Improvements in booster pumps - Google Patents

Abstract

720,526. Centrifugal pumps. NASH ENGINEERING CO. Sept. 29, 1952 [Nov. 15, 1951], No. 24320/52. Class 110(1). A fuel pump comprises a liquid pump arranged to separate and collect entrained gas and vapour from the entering liquid, a compressor which withdraws the separated gas and vapour from the inlet to the liquid pump and is constructed to recondense the vapour, a common driving shaft for the liquid pump and the compressor, and means capable of being used for combining the outputs of the compressor and the liquid pump. An impeller disc 10, Figs. 1 and 4, carries the blades 8 of the liquid pump and the blades 9 of the compressor, which is of the two-lobe liquid-ring type. Gas and vapour are separated centrifugally from the liquid fuel entering the eye of the pump impeller at 51 and collect in an annular channel 52, from which they are withdrawn through bores 52x and 53 to a channel 54 and thence through ducts 49, 47 and 40 to the compressor. From the volute 57 of the liquid pump, the liquid fuel passes to a discharge conduit 58 by way of a valve 59 comprising a piston 64 which is slidable within a cylinder 73. The pressure of the liquid in the conduit 58 tends to move the piston 64 to the right in opposition to the joint action of a spring 78 and atmospheric pressure acting within a bellows 63. The interior of the bellows is vented to atmosphere through passages 67, 68 and 69, Fig. 4, and 70, 71, 72 and 72x, Fig. 1. The valve 59 reduces the liquid pressure to a substantially constant value irrespective of variations in the speed of the pump, which is driven by the gas turbine or other engine to which the fuel is supplied. An annular sealing groove 11 between the liquid pump and compressor sides of the disc 10 is vented by a bore (not shown) to the chamber of the liquid pump to avoid flooding of the compressor. A bleed passage 79a leading from the conduit 58 back to the pump suction prevents the discharge pressure from becoming excessive when the valve is closed. The gas and vapour discharged by the compressor may be returned to a fuel tank through a pipe connected in place of a closure plug 94 or may alternatively be discharged into the conduit 58. In the latter case, communication between the compressor outlet and the conduit 58 is established by making a bore in a partition 92. The necessity for providing a throttle valve in the liquid pump discharge may be avoided by making the diameter of the blades 9 equal to or greater than that of the blades 8, so that the discharge pressure of the compressor is at least as great as that of the liquid pump. In this case, a throttling valve may be provided at the intake of a main fuel pump which receives the discharge of the fuel pump. In the embodiment shown in Figs. 9 and 10, the liquid pump impeller 161 is of the double-sided type. Gas and vapour are collected in annular channels 195, 197 which open into annular passages 201, 205 respectively. From the passages 201, 205, the gas and vapour pass by way of separate passages (not shown) to the separate inlet passages 233, 231 respectively of the two lobes of the liquid-ring compressor 151. From the compressor outlet 235 the gas and vapour pass to a chamber 237 to join the pumped liquid after the latter has passed through a throttling valve 241 which is similar to the valve 59 in Figs. 1 and 4. A passage 291 in communication with the pump inlet is connected to the liquid pump volute 189 by a by-pass valve 293 which is closed by a spring 305 during normal operation but can open on stoppage of the pump to permit the main fuel pump to draw fuel through the inoperative pump. Specifications 648,546 and 654,853 are referred to.