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).
Description of the Claudel-Hobson air-driven petrol pump and its operation.
| Identifier | ExFiles\Box 61\3\ scan0279 | |
| Date | 30th October 1931 | |
| X4038b. To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Aln. c.c. to WOP. c. to Mr. H.S. c. to Mr. W. Plaques. Hs{Lord Ernest Hives - Chair}/Aln.8/KT.30.10.31. CLAUDEL-HOBSON AIR DRIVEN PETROL PUMP. This apparatus comprises essentially a long cylinder containing two pistons joined by a rod. Air is admitted on the outer sides of the pistons alternately, being controlled by a trip valve which operates at the end of each stroke, while petrol is picked up and delivered on the inner sides of the pistons, the action being purely reciprocating. A sectional drawing of the pump is attached. The object of this form of pump is to enable the pump to be placed near the petrol tank on an aeroplane, which may be at a low level and to deliver petrol under pressure instead of using suction which is liable to cause gas locks in the lift line. In conjunction with the pump, a regulator valve, of which a drawing is also attached is installed close to the carburetter. This is fitted with a diaphragm of impregnated fabric which is subject to the petrol pressure and is connected to a needle valve which controls the flow of air to the pump, cutting it off as the petrol pressure rises. Since the air is applied to the same piston which propels the petrol, the pressure of the two fluids at the pump must be equal, and since the regulator cuts off the air above a certain petrol pressure, it tends to throttle the air at all times down to this working pressure. Actually, owing to slight time lag, it periodically admits small gusts of air and then cuts off completely, allowing it to expand somewhat in the manner of a Parsons steam turbine governor. The maximum air pressure however, is usually about 3.0 lbs/sq.in. with low lift heads, falling to about 2.0 lbs/sq.in. before the valve again opens. If a head of petrol intervenes between the pump and the regulator valve, the consequent fall of pressure at the valve after a certain expansion has taken place allows it to open earlier and thus to continue working without stalling, a correspondingly larger amount of air being consumed. In this case, the pressure fluctuations are apt to be greater or at least more noticeable, even at the regulator valve itself, owing we think, to the compression of air bubbles which leak past the pump pistons into the petrol system. The pressures at the pump are of course, greater. The maximum pressure available in the event of any obstruction in the delivery line or of any stiffness in the action of the pump is equal to that of the air supply. The scheme thus provides considerable automatic reserve without excessive air consumption under normal conditions. | ||