Rotary Diesel Engine

Press, Volume CX, Issue 32393, 4 September 1970, Page 17

Rotary Diesel Engine

A diesel version of the Wankel rotary engine is being developed by RollsRoyce. The development of such an engine will be a major breakthrough in power-unit design. Several experimental units have already been built and run, and a “final” engine is now almost completed. The project, part of a research and development programme on the application of new types of power-unit for use in military vehicles, is sponsored by the British Ministry of Defence. Rotary engines would be ideal for armoured cars and tanks because of their compact dimensions and light weight for a given horse power, according to RollsRoyce engineers. Their use

would allow designers to give fighting crews more room and heavier armour protection. For such applications, diesel oil is preferable to other fuels because it is less flammable, but its use in Wankel engines has until now been difficult because the high compression ratio required to fire it by compression ignition requires a long, slim combustion space, which is far from ideal. Engineers at the RollsRoyce factory at Crewe solved the problem by building a double rotor, using two chambers and rotors of different sizes geared together, one on top of the other. The larger, bottom rotor acts as a compressor and decompressor for the upper unit, in order to

achieve the high pressure necessary for spontaneous burning of the fuel. The fuel injector is in the same position as is the sparking plug in a petrol rotary engine. Working speeds up to 4400 r.p.m. are possible with this design, twice that of conventional diesel engines of equivalent horsepower. For a given power, it is expected that the Rolls-Royce engine will be about one-quarter the size of a piston diesel and half the size of a gas turbine. Because of its power and size advantages, the rotary diesel engine is expected to be of great interest to truck manufacturers, and it may also increase the use of diesel engines in larger cars. *