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 the annulus area for low-speed carburetter jets on 20HP & 40/50HP chassis.
| Identifier | ExFiles\Box 66a\1\ scan0172 | |
| Date | 22th February 1927 | |
| To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} X8080 BY/CS3/DB.{Donald Bastow - Suspensions}22.2.27. Re 20HP & 40/50HP Chassis - Carburetter. Sec:5080. Low Speed Jets. The increase in the area of annulus between the jet and the cone of the valve is not constant per revolution of the operating nut, but varies according to the following expression which will give part of a sine curve if valve lift is plotted against effective area. Let D = Dia of Jet. x = Width of annulus normal to cone per rev: of nut. α = Angle between cone and axis of valve. then effective area ("A") A = π Dx - π Cosαx² x varies directly as No.of turns of nut Thus the amount of increase of the annulus for one turn of the operating nut depends on the normal position of the valve. Below are given the different constants for both 40/50HP and 20HP. 40/50HP 20HP Lift of valve per rev: of nut .0416 .0833 Angle of cone with Axis (α) 3°-48' 1°-26' Width of annulus normal to cone for one rev: of nut. (x). .00276 .00203 Dia: of Jet. (D). .2187 .125 BY/CS | ||