From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical description of the operation of a boost control system for an engine.
| Identifier | ExFiles\Box 179\2\ img152 | |
| Date | 11th January 1932 | |
| -2- The piston valve then uncovers the edges of the ports, which allow the suction of the supercharger to be exerted on the front end of the relay piston, and the rear end, due to the arrangement of the changeover cock is open to atmospheric pressure. By reason of the pressure difference between the suction, and atmospheric pressure, the relay is firmly held, to enable positive operation of the throttles, by the pilots operating lever. As the pilots lever is moved forward, the throttles will positively open until the rated boost pressure is obtained in the pressure side of the supercharger. At this point the changeover cock closes the atmospheric port and the boost pressure is then utilised as the pressure medium for the relay. The aneroid is set for the rated boost pressure, and therefore at this stage is in a state of balance, i.e. the piston valve ports are closed. Further pilots lever movement, or conditions tending to increase the boost causes the aneroid to rise and lift the piston valve and so open the ports to give suction to the rear of the relay piston, and the atmospheric side of the changeover cock being closed, the boost pressure is exerted on the front end of the piston, which allows the relay piston to move out-wards; and absorb the pilots lever movement, without operating the throttles. When the relay piston has travelled the length of its stroke and still maintaining the boost pressure, the pilots control will have traversed approximately 85% of the total movement of the quadrant. This position on the pilots quadrant will constitute the gate position, and the remaining 15% movement is utilised to obtain the take off boost. To obtain the take off boost, the pilots lever is operated beyond the gate, and the throttle operating levers will override the relay, which is now fully extended, the throttles being positively operated to the end of the pilots lever movement, at which position the boost pressure should be at maximum permissible for the take off, with the corresponding engine R.P.M. This position is adjustable for correct boost, by an adjustment provided on the operating lever, on the engine controls. After the take off, the pilot returns his control lever to the gate position to resume rated boost, and as the aneroid is in a state of balance at the rated boost pressure, the change of atmospheric pressure with altitude will tend to decrease the boost pressure, which being exerted on the aneroid will cause it to raise the piston valve, and allow suction to the front, and pressure to the | ||