Gas
expands when heated, and contracts when cooled. Stirling engines move the
gas from the hot side of the engine, where it expands, to the cold side,
where it contracts.
DISPLACER PISTON
When there is a temperature difference between upper
displacer space and lower displacer space, the engine pressure is changed
by the movement of the displacer. The pressure increases when the displacer
is located in the upper part of the cylinder (and most of the air is on
the hot lower side). The pressure decreases when the displacer is moved
to the lower part of the cylinder. The displacer only moves the air back
and forth from the hot side to the cold side. It does not operate the crankshaft
and the engine. In other words, the connecting rod to the displacer could
be a string in this engine and it would still work.
POWER PISTON
When the engine pressure reaches its maximum because
of the motion of the displacer, a power piston is pushed by the expanding
gas adding energy to the crankshaft. The power piston should ideally be
90 degrees out of phase with the displacer piston. The displacer type Stirling
engine is operated by the power of the power piston. |