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).
Comparison of sleeve valve and poppet valve engines, with a discussion on steel penthouse heads.
Identifier | ExFiles\Box 134\2\ scan0039 | |
Date | 30th May 1935 | |
-4- E/PSN.2/MN.30.5.35. (3) Sleeve and Poppet Valve Engines. Generally speaking it does not appear that the sleeve valve engine has much advantage in port area over the poppet valve engine, but it should gain in orifice coefficient as the flow in the sleeve valve ports is freer than that in a poppet valve port. Comparing the Bristol Poppet and Sleeve Valve engines it will be seen that the Sleeve Valve engines have rather more port area. However, the Pegasus is rather better than the Perseus even at the top speeds and considerably better at the lower speeds. It would appear that the sleeve valve engine should have better breathing, both due to larger valve area and better orifice coefficient and possibly the explanation of why this is not so is that the Perseus engine is still in a development stage. The large port area of the Kestrel Sleeve Valve engine is due to the long duration of opening which is necessary with the type of head which we are at present investigating. With a normal type of head the Kestrel sleeve valve engine would have a very similar port area to that of the Aquila. No figures are available for the maximum port area of the Aquila but it can safely be assumed that the ratio of port area to piston area will be similar to that of the Perseus. The port arrangement of the Exe engine with one inlet port between the exhaust ports is such that the maximum possible port area which can be obtained is considerably greater than with the more usual arrangement used on the Kestrel and Bristol Sleeve Valve engines. However, the limitations imposed by the air cooling limit the port area to .204 of the piston area. With liquid cooling the same limitation does not exist and we are at present designing a liquid cooled cylinder in which the port area has been increased to .235 times the piston area. The first liquid cooled Exe sleeve valve cylinder however, has exactly the same ports as the air cooled cylinder. (4) Steel Penthouse and Ramp Head. It is possible to use larger valves in a steel head than in an aluminium one as no valve inserts are required which accounts for the large valve area of the head. Contd: | ||