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).
Page detailing the methodology for testing supercharger performance, including torque and air measurement, and efficiency estimation.
| Identifier | ExFiles\Box 42\3\ Scan050 | |
| Date | 1st December 1926 guessed | |
| contd :- -5- reaction on the supercharger casing, which is swung on ball bearings similar to a Froude brake. For torque measurements the pointer 'P' on the torque arm is always brought to a fixed point by means of the screw adjustment above the scale pan. This point corresponds to the position occupied by the pointer when the supercharger is stationary. There is therefore no error due to the displacement of the centre of gravity of the swinging mass. To approximate as close as possible to altitude conditions, the supercharger is arranged to draw air from a low pressure reservoir, and compress it to approximately atmospheric pressure. For this purpose the carburetter intakes take the form of large drums with variable orifices, which give a supply of relatively still air at low pressure. Air measurement is by a venturi calibrated at the R.A.E. The outlet pressure from the supercharger is slightly above atmospheric due to the restriction of the venturi. We think that for the same ratio of compression the efficiencies obtained on the rig will be sensibly equal to those obtained under altitude conditions on the engine, where the outlet pressure is slightly below ground level atmospheric pressure. Estimation of efficiencies. Both adiabatic and total efficiencies are based on the ratio of compression in the supercharger. We give two sets of efficiency figures; in the first case (A) the ratio of compression is taken to be contd :- | ||