Speed Control and Kill Tap
............ How do you stop a Stirling Engine?
Whilst the Hot Cap is hot, it wants to run. You can't stop heat flowing.
Usually when a boating trip is over, we turn the burner off, tie the boat to its moorings, leave the engine running - and the propeller turning - until the heat is used up.
It can take three or four minutes for the engine to stop.
How have others tackled this problem?
Philips, with their cruiser "Jan de Witt" vented the Helium to a buffer tank. With less pressure, the engine produces less power. But then the pressure inside the engine has to be rebuilt.
The UK boating group are using a far simpler solution.
A pipe is fitted to connect the gas volume above the piston, with the gas volume beneath the piston. A tap in this pipe can connect, or isolate, the two volumes. With the tap fully open, the pressure above and below the piston equalises. The engine stops. With the tap part open, the engine speed can be controlled. A needle valve is needed to give the needed fine control.
There is no loss of pressure (or Helium) and power can be restored immediately.
There is also another benefit. What happens if the load on the engine on the engine is suddenly removed?