| 摘要 |
<p>1,235,846. Valves. DOWTY FUEL SYSTEMS Ltd. 14 Oct., 1968 [8 Nov., 1967], No.50804/67. Addition to 1,084,871. Heading F2V. [Also in Division F1] A gas turbine fuel supply system with an operating mode similar to that disclosed in Specification 1,084,871 comprises a pump 11 which delivers to line 30 via port 14 controlled by regulating spool 18, passage 25 and variable throttle 23, 24. Spool 18 responds to the pressure drop across the throttle and is biased to an open position by spring 31 with a force which is a function of the position of the movable throttling plug 24. The spool serves to increase the pressure drop across the throttle as the latter increases in area, thereby rendering the change in flow per unit movement of plug 24 more uniform over the whole range of movement. The spool is continually rotated through gearing 36, 37 to overcome friction. In Fig. 2 (not shown), chamber 33 beneath the spool has restricted communication with the upstream and downstream sides of the throttle so that the spool is only subjected to a proportion of the pressure drop across the throttle. A valve in the pump inlet tends to close at low flow rates and thereby reduces the radial depth of the liquid annulus in the pump in known manner. In Fig. 3 (not shown), a positive displacement pump is used and the spool controls a by-pass line. The spring can be machined from a tubular blank.</p> |
