What are single-acting cylinders and double-acting cylinders?

The single-acting cylinder only acts on one end of the piston, and the double-acting cylinder acts on one end of the piston.

Single-acting cylinders are usually used in internal combustion engines, such as automobile engines, which rely on an element (including a spring or an external load) to push the piston in another direction, thus generating motion. Single-acting cylinders are sometimes used in pumps and hydraulic cylinders to help complete heavy-duty operations, such as lifting heavy objects.

Double-acting cylinders work at both ends of the piston, with one element for the outer stroke and the other element for the inner stroke. Although single-acting pistons are often used in internal combustion engines, double-acting pistons can also be found in machines such as steam engines, which are called external engines. This is because the double-acting cylinder generates force from both ends of the piston.

Cylinder origin:

The cylinder principle originated from the cannon.

1680, inspired by the principle of artillery, Dutch scientist Hoorns thought that it would be no good to use the powerful power of artillery shells to propel other machinery. At first, he still used gunpowder as a burning explosive, replaced the shell with a "piston", used the barrel as a "cylinder" and opened a one-way valve. He injected gunpowder into the cylinder. After the powder is ignited, it explodes and burns violently, pushing the piston to move upwards and generating power.

At the same time, the huge pressure of the explosive gas also pushes open the one-way valve and discharges the waste gas. Then, the residual exhaust gas in the cylinder gradually becomes cold and the air pressure becomes low. The atmospheric pressure outside the cylinder pushes the piston downward to prepare for the next explosion. Of course, due to the long distance and low efficiency, he didn't succeed in the end.

However, it was Hoorns who first put forward the idea of "internal combustion engine", and later generations invented automobile engines on this basis.