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).
Requesting experiments to determine a basis for comparing fluid flow through orifices and pipes of different cross-sections.
| Identifier | ExFiles\Box 36\1\ scan 006 | |
| Date | 1st January 1917 | |
| R.R. 235 a (400 T) S. C. 536. 15-3-16) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1846. [Handwritten: 1/17] COPY. E1/B30/1/17. To FFC. from E.{Mr Elliott - Chief Engineer} c. to EH. [Handwritten in left margin: R907] RE BASIS OF COMPARISON FOR ORIFICES, &c. In accordance with Mr. Royce's instructions, would you please make some experiments to determine on what basis orifices of different cross sectional areas, and different cross sectional forms should be compared for determining their relative capacity to pass fluids under given heads. Would you also make similar experiments for continuous lengths of pipe of different cross sectional area and form The point is that hitherto for comparing one induction pipe with another, or one valve bend with another, we have always based our relative values on [handwritten formula: (Area of cross sec:)^2 / Perimeter] and for comparing one sudden restriction with another, such as a petrol jet orifice or a valve annulus, we have always thought that the basis of comparison lay between the above expression and just the simple cross sectional area. Recently however, the last thesis has been somewhat overset by two practical examples, which I give as follows:- We found that the Grand Prix Mercedes engine, and the Eagle R.R. gave 100 lbs. per square inch mean effective pressure at identical gas speeds through the valve annulii and carburetter throats, whereas these engines differ greatly in design. An R.R.C.H. variable jet designed at St.{Capt. P. R. Strong} Margaret's to give 20% mixture variation by [handwritten formula: (Area)^2 / Perimeter] and 13% by plain cross sectional area, was reported to give actually 12% variatio (Contd.) | ||