Stirling Engine

The Stirling engine operation is based on the use of volumetric changes of the gas as a result of changes in temperature that this affected. These volumetric changes are due to the displacement of gas between the hot zone and the cold zone in a closed cylinder.

1. If air is enclosed in a cylinder and then heated, the pressure within the cylinder increases. It is assumed that one of the covers of the cylinder is a piston and this is tight, there will be an expansion of gas and increase the volume inside the cylinder until some final position of the plunger.

2. If the same cylinder in its expanded state is quenched pressure decreases, then the volume is contracted and the piston position returns to the initial state.

3. If the process from state 1 is repeated, but now joining the piston to a crankshaft and in turn a wheel, the increased pressure will force the piston move causing the crankshaft and this at the wheel too, with this achieved that the volumetric change is transformed into motion.

4. When the process from state 2 is repeated, the piston return cooling rapidly by movement of the wheel and occurs the pressure decrease and volume.

5. If the processes 3 and 4 meet is a single cylinder engine displacer movement will occur due to expansion of the gas during compression and the piston return to its position due to the energy of the flywheel. With this principle of operation of the Stirling engine are explained.

displacer cylinder

95mm diameter / 235mm height stainless steel cylinder

cooling jacket

150 diameter tin can

8mm nylon tubing

rubber washer

displacer

steel wool and wire mesh

crankshaft

4mm steel rod

flywheel

170 mm diameter metal disk

Diaphragm

thin rubber ballon

Heat source

stirno

wood for structure

Build the water jacket

Made from some large 150 mm diameter tin cans. I spray painted them before assembly to help protect them from the water. To connect the water inlet.outlet I used two 15mm to 8mm brass couplings (ordinary plumbing parts). The 8mm nylon tubing can be fitted securely into these. The brass couplings are perhaps a little to big for this job, 8 mm couplings might have been better, but I couldn't get those at the time.

The displacer

The displacer is made from stainless steel wire wool that is wrapped around a stainless steel mesh. The wool I used is described as fine stainless steel wool, but it's actually quite coarse.

From here add the wire that will attach to the crank shaft

The crankshaft:

It must be perfectly straight and have some fairly tight bends in it. It's made from 4mm steel rod. You need to add the bearings and brass connectors as you make the crankshaft. I made a jig to help with forming the cranks.

The wooden supports

Using a circular saw cut out grooves to support both the pot and the crank shaft

The displacer needs a container to hold it and to allow it to move the air. Use a large pot, using an asparagus cooker will kill two birds as it comes with a strainer which can be used in the displacer. Drill a 7 mm hole in it near the bottom to put the coupling and the nylon tubing.

To make the compression take a rubber balloon and cut it midway down. Take a bolt with a washer and stick it through. Attach another washer and tighten it all down with a nut. Then stretch it over the top of the pot.

Open the stirno and light it beneath the finished product.

https://www.youtube.com/watch?v=U9vPdcW_qTg#action=share