The earth is surrounded by air, which we call the atmosphere. The atmosphere spreads from the surface to the sky 1000km above the ground (Figure 1-4). 1 standard atmospheric pressure = 1.033kgf/cm2 = 760mmHg = 10000mmH0. Figure 1-5 shows the gas obtained by compressing the atmosphere, which is called compressed air. Compressed air of 0.7MPa (≈7kgf/cm2) is obtained by using an air compressor to compress the atmosphere to 1/8 of its original volume. gas.
After the air is compressed, it becomes compressed air. It stores a certain amount of energy in the compressed state, and this stored energy can be used to perform work on the outside.
