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).
Explanation of the 'baffling impingement' principle and the construction and function of an Air-Maze filter.
| Identifier | ExFiles\Box 135\4\ scan0096 | |
| Date | 19th October 1925 guessed | |
| nostrils are oiled or moistened naturally to increase their dust binding effect. To revert to the “baffling impingement” principle: there is a way of applying this principle, which produces maximum results, I mean, uniformity (it’s a great word, where filters are concerned) UNIFORMITY in the distribution of the baffles, in particular. It will be easily seen that each small stream or volume of air, passing through the filter should have exactly the same baffling as every other small stream or volume, if we are to have the greatest impingement effect. In other words, we must arrange our filter media so that it is UNIFORM in density, and UNIFORM in porosity throughout its mass. This is the reason why woven wire screen properly arranged is the best material from which to construct a filter. Now take a good look at the illustration how the screen is arranged in the Air-Maze filter: You will see that it is made up of alternate layers of flat and crimped screen. The crimped layers are essential to any filter employing screen as the filter’s medium; performing three functions of great importance—not to be had without them, viz.: First: They separate the flat layers (which is obvious) and, they provide a very large dust carrying space and surface. Second: They cause the air entering through the flat layers to take a gentle uniform swirling motion, which insures maximum contact of the dust particles with the screen wires. Third: They provide an exit for the collected dust through the open trough end of the crimp, so that the dust on each individual screen is got-ten rid of without such dust having to pass through any of the other screens of the filter, thereby making the Air-Maze very easily cleaned. It is considerable of a puzzle to most everyone when they first look through the Air-Maze filter to understand how it can possibly stop the very fine particles of dust in the air, and the Air-Maze has been condemned without trial by a very few because of its open, porous nature. It is only necessary, however, to see the Air-Maze in actual operation on a motor car to be convinced beyond question that it functions practically 100% on these fine dust particles. In summarizing, take particular note that: First: The whirler cleaners are most efficient in their particular class where the entering air stream is thin, and has a circumferential velocity of around 10,000 feet per minute. Their efficiency at low engine speeds is practically nil. Second: The whirler cleaners reach their maximum efficiency at high engine speed, and with flaky material, but at the same time they impose their greatest resistance at the point of their highest cleaning efficiency. Third: The whirler cleaners are very low in efficiency in handling the very fine dust particles which do the most harm to the motor, and also low in efficiency in handling even larger particles at low engine and car speed. ON THE CONTRARY The filter cleaners are highly efficient as dust collectors at all engine speeds, and particularly as regards the very fine dust particles. | ||