Thomas Newcomen’s steam engine was one of the first devices to use the power of steam for mechanical work. It was originally used to pump water form mines. A boiler, encased in brick and sitting over a coal fire, generated steam, which drove the piston in the open top cylinder above the boiler. When the steam built up, the pressure opened a valve allowing the steam to fill the cylinder and push the piston up. When the piston reached the top of the cylinder, the first valve was closed and the second valve opened. This second valve sprayed cold water into the cylinder from a cistern, condensing the steam and creating a vacuum. The air pressure from the open-top cylinder pushed the piston down again, thus pulling the rod down with it. The cycle then repeated itself all over again.
Khi làm dạng bài “Labeling a diagram” các bạn học ielts cần chú ý đến thứ tự của các steps hay parts nhé.