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).
The effects of applying exhaust momentum manifolds to various aircraft.
Identifier | ExFiles\Box 134\1\ scan0046 | |
Date | 26th November 1937 | |
THE EFFECT OF APPLYING EXHAUST MOMENTUM MANIFOLDS TO VARIOUS AIRCRAFT FITTED WITH R.R. ENGINES. Exhaust momentum manifolds have been tried out on various machines having fixed pitch airscrews, and in every case the results have shown greater gains in speed than can be accounted for by momentum effects only. This is explained from the fact that there are three separate factors combining to produce the measured gain, viz :- 1. Momentum - giving maximum possible gain varying from 2 MPH. at a machine speed of 200 MPH. to 5.8 " " " " " 300 " and 12.0 " " " " " 400 " 2. Increased engine R.P.M. and boost pressure (i.e. engine power) with fixed pitch airscrews as a result of the increased forward speed, the effect of which can be assessed by assuming that the speed v ∝ ³√HP. This has been found in practice to give gains varying from 5 MPH. at a machine speed of 350 MPH. to 2½ MPH. at a machine speed of 250 MPH. 3. Smoothing out the air flow over the body due to ejecting the gases backwards at high velocity, thereby suppressing turbulence, and eliminating the interference caused by blowing out the exhaust gas at right angles to the airstream. Constant speed airscrews will be used on all types of aircraft in the future, and in consequence, item 2. above will be eliminated, and there will be a corresponding drop in the measured gain. It is unfortunate that no [text missing] were available when the tests were [text missing] repeat them as [text missing] | ||