This article is in continuation with our previous article Stirling Engine Project Idea. In this article we will discuss various types of Stirling engines and their working in detail. Sterling engines work on simple principle of  temperature difference where compression and expansion of gases produces useful work. Even after the advancement of Internal Combustion engines, Stirling engines are still used in different industrial applications for they are more efficient. Working model of Stirling engines can easily be made hence it can be very good Mechanical Engineering Project Idea for you.

Types Of Stirling Engine:

Alfa type Stirling engine:-

Alfa stirling engine consists of two cylinders .

One cylinder (expansion cylinder) is kept at high temperature while another (compression cylinder) at low and the passage between the two cylinder contains the regenerative fluid (gas) working of the Alfa type Stirling engine as discussed above that it contains two cylinders one is hot and other cold.

The hot cylinder is fitted inside the high temperature heat exchanger and colder one inside the low temperature heat exchanger. This type of heat engines has a high power to volume ratio though has technical problems because of high temperature of hot piston and durability of its seals. Though there is some additional dead space inside the cylinder to reduce this problem.

1. Shown in the diagram, nearly all the working gas is in contact with the hot cylinder walls. The gas has been heated and therefore expansion takes place which has pushed the hot piston to the bottom. The expansion continues in the other cylinder (cold cylinder), which is 90 degree behind the hot piston in its cycle thus extracting more work from the hot gas.
2. Now in the second diagram, the gas is now at its maximum volume. The hot cylinder begins to push most of the gas into the cold cylinder, where it cools and the pressure drops considerably.
3. As you can see in the third diagram, almost all the gas is in the cold cylinder and cooling continues. The cold piston which is powered by the flywheel momentum compresses the remaining part of the gas.
4. Here in the fourth diagram, you can see the gas reaches its minimum volume and now it will expand in the hot cylinder where it is heated once more thus driving the hot piston in its power stroke.

This completes the whole working of the Alfa type Stirling engine. Now we come to beta type stirling engines.

Beta type stirling engine:–

Beta type stirling engine consists of only one cylinder with hot and cold ends, a loosely fitted displacer which shunts the air (working gas) between hot and cold end and a power piston at the end of the cylinder which drives the flywheel. The flywheel is connected to the piston with help of connecting links.

A cross section of a beta stirling engine design is shown in the diagram. Different parts includes-

1. hot cylinder wall
2. Cold cylinder wall
3. Coolant inlet and outlet pipe
4. Thermal insulation which separates the two cylinder ends
5. Displacer piston
6. A power piston
7. Flywheel
8. Linkages it removes the technical problems of hot moving seals unlike the Alfa type. Displacer and the power piston arranged in the same shaft. The displacer in this case does not extract power from the expanding gas but serves to shuttle the working gas between hot and cold ends.

1. The power piston has compressed the working fluid, the displacer piston has moved so that most of the gas gets closer to the hot heat exchanger.
2. The heated gas increases the pressure inside the cylinder and pushes the power piston to the farthest limit of the power stroke.
3. The displacer now moves and pushes the gas to the cold end of the cylinder.
4. Finally the cooled gas is compressed by the flywheel momentum and it takes less energy as its pressure drops when it is cooled.

As we have discussed earlier that it is a closed cycle process which means the heat driving it must be transmitted from a heat source to the working fluid and eventually to the sink. The heat source for it can come from burning of fuel, waste combustible products, landfill gases etc as it does not comes in contact with internal parts. Other sources can include concentrated solar energy, geothermal energy nuclear energy, waste heat and bio-energy which are in abundance in nature.

Gamma Stirling Engines: 

Gamma Stirling engines are similar to beta engines i.e these are also displacement type but in this, the power piston is mounted in separate cylinder along side displacer piston cylinder but still connected to same flywheel.

This ends our discussion on sterling engines. Check out various Mechanical engineering projects ideas based on Stirling engines. If you want further information on any project, let us know.