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Shaft Engines
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
This type of engine has one or two rows of cylinders arranged in a circle around a centrally located crankcase (Figure 6.6). Each row must have an odd number of cylinders in order to produce smooth operation. Rotary and radial engines look strikingly similar when they are not running and can easily be confused, since both have cylinders arranged radially around a central crankshaft. Unlike the rotary engine, however, radial engines use a conventional rotating crankshaft in a fixed engine block. A radial engine has only one crank throw per row and a relatively small crankcase, resulting in a favorable power-to-weight ratio. Because the cylinder arrangement exposes a large proportion of the engine’s heat-radiating surfaces to the air and tends to cancel reciprocating forces, radials tend to cool evenly and run smoothly. The lower cylinders, which are under the crankcase, may collect oil when the engine has been stopped for an extended period, which can cause hydrostatic lock. In military aircraft designs, the large frontal area of the engine acted as an extra layer of armor for the pilot. However, the large frontal area also resulted in an aircraft with a blunt and aerodynamically inefficient profile.
Engine performance
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
When there is more than one cylinder in a piston engine, as is usually the case, they must be connected together via a certain order. It is often common for piston engines to be classified by the number and alignment of cylinders and also by the total volume of displacement of gas by the pistons moving in the cylinders. A few commonly used variants of piston engines (Figure 4.6) are introduced briefly here. In-line engines: The cylinders of an in-line engine are arranged in a single row parallel to the crankshaft. The cylinders are either upright above the crankshaft or inverted, that is, below the crankshaft. The inverted configuration is generally employed. Rotax 447 is a piston engine with two cylinders, in-line, and two strokes.Vee-type engines: The V-type engine has the cylinders arranged on the crankcase in two rows, forming the letter V, with an angle usually between the rows of 45° and 60°. There is always an even number of cylinders in each row. French FAM-200 is a piston engine with six cylinders, in Vee form, and four strokes.Radial engines: A radial engine has an odd number of cylinders extending radially from the centerline of the crankshaft. The cylinders are arranged evenly in the same circular plane, and all pistons are connected to a 360° crankshaft, thus reducing both the number of working parts and the engine weight. The cylinders are installed around the crankshaft to form a circle; the pistons move in and out of the circle along the radius. PZL K-9 (Poland) is a piston engine with nine cylinders, in radial form, and four strokes.Horizontally opposed or flat engine: The opposed-type engine is usually mounted with the cylinders horizontal and the crankshaft horizontal; however, in some helicopters, installation of the crankshaft is vertical. Teledyne Continental IO-520-L is a piston engine with six cylinders, horizontally opposed, and four strokes.
William Weir: architect of air power? The First World War chapter
Published in The International Journal for the History of Engineering & Technology, 2023
This brilliant work was incorporated into the design of a 14-cylinder, twin row radial engine, the R.A.F.8. Figure 1 shows the general arrangement drawings for this project, which were finalised between September and December 1916, suggesting bench running might have commenced in mid 1917. It was not to be. Disillusioned by the campaign against the Factory, the design team headed by F. M. Green, including Heron, left the R.A.F. in January 1917 to take up roles at the motor vehicle firm Siddeley-Deasy, which was building aeroengines under the leadership of an autocratic former bicycle designer, John Siddeley. In its original form, the R.A.F.8 was never built.