It should be said that the idea of using steam as power has a long history, and the most famous one is Hilong, the genius of Alexandria. As early as the second century BC, he used hot air and steam as power to start mechanical toys. Only because the social productive forces at that time had no urgent demand for this kind of artificial power source, Hilong's experiment was just to let people play for a while.
17 and 18 centuries, with the development of social productive forces, the demand for artificial power is gradually prominent.
At that time, Britain had to solve the problems of coal mining and ironmaking, and coal mining needed strong power to discharge mine water. It is said that a mine used 500 horses to do this work, which greatly affected the profit of the mine owner. As a result, people began to design and manufacture various steam engines. The first one to succeed was newcomen.
Newcomen is a Dartmouth metal dealer. He is familiar with mines in Devon and Cornwall. He knows that pumping water in the mine is a difficult problem, and he is determined to solve this problem. Later, he spent 10 years doing experiments. Finally, in 1705, he developed the first water pump with a piston driven by steam. Its working principle is that the steam engine has a vertical cylinder with an open top, the piston rod is connected to one end of a pivoting beam by a chain, and the sucker rod is connected to the other end of the beam by a chain. When the sucker rod descends, its weight lifts the piston from the cylinder. At the same time, a valve opens, allowing steam to be injected from the boiler into the cylinder under the piston. When the piston reaches the peak, the steam supply is blocked, another valve is opened and cold water is sprayed. The condensation of steam creates a vacuum in the cylinder, and the atmospheric pressure at the upper end of the piston pushes the piston down. This power stroke lifts the sucker rod, thus pumping water out of the mine. The birth of this steam engine is a major breakthrough in artificial power. However, due to the large coal consumption, it was difficult to apply it in places far away from coal mines and could not meet the needs at that time.
It was Watt who fundamentally changed newcomen's steam engine. Watt 19, the son of an English businessman, went to London as an apprentice and studied instrument manufacturing. At the age of 2/kloc-0, he repaired and manufactured instruments at Glasgow university. Watt often talks with some teachers about improving the steam engine, which adds a lot of scientific knowledge. 176 1 year and 1762, he did some experiments to improve the steam engine, but no progress was made.
1764, the school handed over a newcomen steam engine to Watt for repair. Watt began to discuss the working principle of steam engine after his efforts to reduce steam consumption failed. He found that one of the reasons why newcomen's steam engine was inefficient was that it consumed a lot of heat to heat the cylinder itself. It occurred to him that if cooling is carried out in another container outside the cylinder, it will not only help to reduce the cooling temperature, but also help to maintain the temperature inside the cylinder. After the experiment, his idea was confirmed.
1765, 29-year-old Watt invented a steam engine with an independent condenser. Because the cylinder is connected with another condenser, the used steam condenses into water in the condenser, which can keep the cylinder at a certain temperature all the time during operation, thus greatly saving fuel. Four years later, Watt obtained the patent right and was called "the king of patents".
Watt is not satisfied with this. With the cooperation and support of Bolton, the owner of Birmingham Machinery Factory, he continued his experiment. Later, he invented the steam valve of the steam engine and the mechanism that can change the reciprocating motion of the steam engine into rotary motion. In this way, the main aspects of the steam engine are similar to today.
After the invention of the steam engine, Watt was thinking about how to express the efficiency of this machine. Before that, people used horses as power, so people had a habitual estimate of their strength. Watt thinks it is best to compare the efficiency of machines with that of Malays. So he borrowed some horses from a brewery to do the experiment. He tied a long rope with a 100 kg weight system, put the heavy object into a deep well, and then pulled it with a pulley. As a result, the horse can walk 220 feet per minute and do 22,000 feet of work per minute under the weight of 100 pounds. Considering that the friction of the pulley will consume some energy, the watt is increased by 50% from 220 feet to 330 feet. The work of doing this is equivalent to 33,000 foot pounds per minute, or 550 foot pounds per second. He called this figure horsepower. This is how the unit "horsepower" came from.