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).
Fuel distribution challenges in twin volute superchargers and the decision to focus on a single volute design.
| Identifier | ExFiles\Box 140\1\ scan0148 | |
| Date | 3rd April 1935 | |
| To E.{Mr Elliott - Chief Engineer} +109 E/PSN.1/MN.3.4.35. Copy to Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} -------------- Centrifugal Superchargers for Car Engines. We have been considering further the twin volute supercharger and have come to the conclusion that it will be difficult to obtain even distribution of fuel between the two volutes under all conditions of speed and load, unless some means is obtained of ensuring even fuel distribution over the eye of the rotor. A fuel particle which enters the eye of the rotor at a point A will, at any particular speed, always follow the same path through the rotor and enter the same volute. This means that if the region around the point A is rich, due possibly to throttle bias, the rich mixture will flow through the rotor to some corresponding part of its periphery, and hence into one of the volutes. The particular volute which the rich mixture enters will vary with speed. Even distribution between the two volutes could also be obtained if the mixture strength was the same at all points diametrically opposite in the eye of the rotor. This might be done by using a twin choke carburetter in which the throttles were parallel and opened in opposite directions. The Americans have recently been following along similar lines with their four-choke carburetters in which each choke communicates directly with one quarter of the rotor eye, thus giving a more even mixture distribution around the periphery of the diffuser, and hence also better distribution to the cylinders which are fed direct from the belt surrounding the diffuser. As the possible advantages to be obtained from the twin volute supercharger would not appear to warrant the added cost and complication of a special twin carburetter, we are concentrating on the design of the single volute supercharger unless we receive instructions from you to the contrary. E/PSN. | ||