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).
Tests of a pump and regulator, analysing air consumption against petrol delivery and leakage.
| Identifier | ExFiles\Box 61\3\ scan0280 | |
| Date | 30th October 1931 | |
| -2- Hs{Lord Ernest Hives - Chair}/Aln. 8/KT.30.10.31.contd There appeared to be no object in making separate tests on the pump and regulator, but a test scheme as shown attached was arranged. Petrol flow was measured by the time required to fill beakers of known volume and air leakage by the time required to displace the contents of an inverted beaker filled with petrol. Exhaust air was measured in a similar manner using an inverted jar in a water tank. The curves herewith show the total air consumption against petrol delivery for various air pressures. It will be noted that the air consumption is very approximately proportional to the petrol delivery and also that it is practically independent of the air supply pressure. The leakage air which is included in the consumption shown, we found was rather uncertain quantity, but on the average amounted to about 5% of the total. The volume ratio of petrol flow to free air used in pumping it is round about 1:3 being a minimum of 1:2.78 at about 220 pints per hour, that is, the pump behaves as though operating on air at upwards of 41 lbs.per sq.in. without cut-off. This seems rather large and is not all accounted for by air leakage. The swept volume of the pump is about 11.25 cu.ins. per cycle and we found that it described on the average 4.4 cycles per pint, thus operating for instance at 14.7 cycles per minute for a flow of 200 pints per hour. These figures represent a volumetric efficiency of 70% from which we deduce that not much over twice the volume of free air used to that of petrol pumped can be accounted for. Possibly there is a considerable direct escape of air each time the trip valve operates but we have not investigated the point further. All the foregoing is for petrol pressures varying from about 2.0 lbs. to 6.0 lbs.per.sq.in. delivery being adjusted by the cock A.{Mr Adams} in the diagram while the cock B. remained wide open. The flow through a fixed orifice under these conditions is somewhat jerky in the absence of any smoothing device. As the petrol pressure remains within the same range for varying air supply pressures, it is to be inferred that the flow through a given orifice would be independent of the latter quantity. To represent a lift head, the cock B. was partially closed and a series of readings taken at 60 lbs.sq.in. air pressure. Owing to the irregular petrol flow this did not correspond to a fixed head, but varied on either side of 6.0 lbs.per.sq.in. (or a head of nearly 19 ft.) by a few lbs. We found that the flow through a given orifice at the cock A.{Mr Adams} was practically unaffected by the addition of resistance at the cock B. the air consumption | ||