A four-stroke engine (or four-cycle engine) is an internal combustion engine in which the working chamber completes four separate strokes which constitute a single thermodynamic cycle. A stroke refers to a full expansion or compression of the working chamber.
(c) Zephyris - Own Work / CC-BY-SA-3.0
(c) Zephyris - Own Work / CC-BY-SA-3.0 / Needs to be corrected for 4 different phases
It is also possible to use the crankless design for a two-stoke engine. A main advantage of the two-stoke engine is its excellent power-to-weight ratio, which usually comes at the expense of a suboptimal themodynamic efficiency. However, the power-to-weight ratio of a crankless four-stoke engine is already signifcantly better than in the cranshaft design. Therefore, the crankless four-stroke engine combines the advantages of the traditional four- and two-stroke designs: low weight AND excellent efficiency. To further reduce weight, and achieve maximum power-to-weight ratio at a thermodynamic cost, the crankless design can however equally be used for a two-stroke engine.
The main advantages of the crankless internal combustion engine compared to the traditional crankshaft engine are:
|Better technology||Tangible advantages|
|4 combustion chambers rotate in one toroid, compared to a separate cylinder for each combustion chamber in the traditional design. Common configuration requires only one toroid vs 4 cylinders in the traditional design.||
|Much less moving parts: no valves, no camshaft or hydraulic lifting mechanism, ...||
|No pressure loss over the intake or exhaust, as there are no valves.||
|No back and forth linear movements of pistons.||
|Higher revolution speeds possible as all components are rotating and the intake and exhaust flows are very fast through large conducts.||
|Only one injector or ignition for four working chambers, compared to 4 injectors or ignition systems in classic 4-cylinder design.||
|Combustion chamber rotates constantly, leading to turbulence in the combustion chamber. High turbulence results in faster and more complete combustion of the air-fuel mix. Less need for complicated cylinder head engineering (CFD).||
Possible applications include:
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