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).
Analysis of air and oil motion affecting engine power, comparing different inlet port and nozzle configurations.
| Identifier | ExFiles\Box 179b\3\ img214 | |
| Date | 14th February 1933 | |
| -24- best consumptions this relation is critical and easily disturbed and (3) that the air and oil motion is purely relative, it is clear that if, as in C.I.1 a combination of air and oil motion had been arrived at experimentally which gave high performance, then disturbing the air motion and leaving the oil motion unchanged will affect the relative motion and cause a loss of power. Since altering the shape of the inlet valve passages can definitely affect the motion of the air within the cylinder (witness the Packard and Guiberson Radial aircooled Diesel engines) this is almost certainly the cause of the lower power with C.I.2. Conversely, if the air motion is kept constant and the oil motion changed by altering the injection pressure, the size and arrangement of the nozzle holes etc, the balance of air and oil motion, will again be disturbed and loss of power result. This is generally acknowledged to be the case and there is abundance of evidence to support it. It does not appear to generally appreciated that modification of the air motion must have a similar effect. Further, in Tests 2b, 2h, 2j and to a lesser degree 3b, the power was for a short time equivalent to C.I.1. On the above theory the correct relative air and oil motion was obtained for a short time (usually when starting) but changed as the engine settled down. These tests show again how easily the performance is disturbed when the engine is giving a high performance. Hence it appears that to bring the power of C.I.2 up to C.I.1 it is necessary either (1) to modify the shape of the inlet ports to that of C.I.1 or (2) to test a number of nozzles varying in diameter and length of holes, number and arrangement of holes, included angle between holes, injection pressures etc, until a combination is found that produces the same relative air and oil motion as in C.I.1. Method 1 reduces C.I.2 to C.I.1 and hence method 2 is preferable as it offers a chance of improving the performance so that it is better than C.I.1. The time and expense involved, however, might be considerable and is not thought to be justifiable. | ||