Other Types Of Engine Mechanisms

WANKEL

The Wankel cycle. The shaft turns three times for each rotation of the rotor round the lobe and once for each orbital revolution around the eccentric shaft.

The Wankel locomotive (rotary engine) does not have piston strokes. It operates with the same separation of phases love the four-stroke engine with the phases taking place in segregate locations in the engine. In thermodynamic terms it follows the Otto engine cycle so may be thought of as a four-phase engine. While it is correct that three power strokes typically occur per rotor revolution due to the 3/1 revolution ratio of the rotor to the eccentric shaft only one power stroke per shaft revolution actually occurs; this engine provides three power strokes per revolution per rotor giving it a greater power-to-weight ratio than piston engines. This type of engine is most notably used in the current Mazda RX-8 the earlier RX-7 and other models.

Gas turbines

A gas turbine is a rotary machinery comparable in principle to a steam turbine and it consists of three main components: a compressor a combustion chamber and a turbine. The air behind being compressed in the compressor is heated by burning fuel in it. About two-thirds of the heated air combined with the products of combustion is expanded in a turbine resulting in job output which is used to drive the compressor. The rest (about one-third) is available as useful work output.

JET ENGINE

Jet engines receive a large volume of hot gas from a combustion process (typically a gas turbine except rocket forms of jet propulsion often use solid or liquid propellants and ramjet forms also shortage the gas turbine) and feed it through a nozzle which accelerates the jet to high speed. As the jet accelerates through the nozzle this creates thrust and in turn does useful work.

ENGINE CYCLE

Idealised P/V diagram for two stroke Otto cycle.

SIX-STROKE

First invented in 1883 the six-stroke engine has seen renewed favour through the last 20 or so years.

Four kinds of six-stroke use a regular piston in a regular cylinder (Griffin six-stroke Bajulaz six-stroke Velozeta six-stroke and Crower six-stroke) firing every three crankshaft revolutions. The systems capture the wasted heat of the four-stroke Otto cycle with an injection of air or water.

The Beare Head and piston charger engines operate as opposed-piston engines two pistons in a single cylinder firing every two revolutions rather more like a regular four-stroke.