Until the second half of the XVIII century, people have used for the needs of the production of water in the main engines. So how to transfer the mechanical motion of the water wheel for long distances is not possible, all the factories had to be built on the banks of rivers, which was not always convenient. In addition, for the efficient operation of such an engine is often required costly preparatory work (ponds, construction of dams and the like). They were at the water wheels and other drawbacks: they had little power, their work is dependent on the time of year and be difficult to adjust. Gradually became acutely felt the need for a fundamentally new engine: a powerful, low-cost, stand-alone and easily manageable. It is in this engine a century has become for man the steam engine.
The idea of the steam engine was partly prompted by its inventors to design the piston water pump, which was known in ancient times.
It works very simple: when the rise of the piston sucks up water into the cylinder through a valve in the bottom of it. Lateral valve connecting the cylinder with the pump string at this time has been closed, since the water in this pipe also sought to enter into the cylinder and thereby closed the valve. When lowering the piston, he began to put pressure on the water in the cylinder, so that the bottom valve closed and opened the side. At this time, water was fed from the cylinder up the pump string. The piston pump operation received from the outside, was spent on the promotion of fluid through the pump cylinder. The inventors of the steam engine tried to use the same design, but only in the opposite direction. Cylinder with piston underlies all steam piston engines. The first steam engines, however, were not so much the engine as steam pumps used for pumping water from deep mines. Their operating principle is based on the fact that the water after its cooling and condensing steam space occupied in 170 times less than in the heated state. If displace air from the heated steam vessel, close it, and then cool the steam, the pressure will be much less within the vessel than outside. The external pressure will compress this vessel and if it put the piston, it will move into the more strongly, the more his area.
The first model of this machine was proposed in 1690 Papen. In 1702 he created his pump Severi. But the most widely used in the first half of the XVIII century, Newcomen steam engine, created in 1711.
The steam cylinder was placed in Newcomen on the steam boiler. A piston rod (rod connected to the piston) is connected with a flexible coupling end of the balancer. It was connected to the pump shaft at the other end of the balance. The piston was raised to its upper position under the action of a counterweight attached to the opposite end of the rocker. In addition, the movement of the piston up helping couples to be run at this time in the cylinder. When the piston is in the uppermost position, close the valve, to let steam from the boiler to the cylinder, and inject into the cylinder water. Under the action of the water vapor in the cylinder rapidly cooled, condensed, and the in-cylinder pressure dropped. As a result of a difference of pressure inside and outside the cylinder, air pressure force the piston to move down, while performing useful work - resulted in the movement of the rocker, who moved the pump rod. Thus, useful work is only carried out when the piston moves down. Then run steam in the cylinder again. The piston is raised up again, and the entire cylinder was filled with steam. Once again inject water, steam was condensed again, whereupon a new piston made useful move down and so forth. In fact, the machine work is done Newcomen atmospheric pressure and the vapor served only to create rarefied space.
In the further development of the steam engine it became clear Newcomen main drawback of machines - the working cylinder it was at the same time, and a condenser. Because of this, it had to alternately cool, then heat the cylinder, and fuel costs are very high. There have been cases when the machine is 50 horses, barely had time to bring up the necessary fuel. Efficiency (efficiency) of this machine barely exceeds 1%. In other words, 99% of the calorific value of the energy is lost fruitlessly. Nevertheless, the machine was in England spread, especially in the mines, where coal was cheap. Further, the inventors have made several improvements to the Newcomen pump. In particular, in 1718 Beighton invented automatic distribution mechanism that automatically enable or disable the steam and let in water. He added steam boiler safety valve.
But the concept of the machine Newcomen remained unchanged for 50 years, until it is not engaged in the improvement of the University of Glasgow mechanic James Watt. In 1763-1764 years he had to repair the sample belonging to the university Newcomen machine. Watt has made her a small model and began to study its effect. However, he could use some of the instruments belonging to the University, and the advice of professors. All this has allowed him to look at the wider problem than looking at it, many mechanics to him, and he was able to create a much more advanced steam engine.
Working with the model, Watt found that when zapuskaniya vapor in the cooled cylinder it is a significant amount of condensed on its walls. Watt immediately became clear that a more efficient operation of the engine it is more expedient to keep the cylinder constantly hot. But in this case the condensed steam? A few weeks later, he was thinking, how to solve this problem, and finally realized that the cooling of the steam must be in a separate cylinder is connected to the main pipe stub. Watt himself recalled that once during an evening walk, he passed the laundry and then at the sight of clouds of steam escaping from the window, he realized that the steam being an elastic body, must aspire to the rarefied space. It was then that he got the idea that the Newcomen machine must be supplemented by a separate vessel for steam condensation. Simple pump driven by the machine could be removed from the air and water of the condenser, so that at each stroke of the machine there could be created a space unloaded.
After that Watt has made several improvements, with the result that the car took the following form. To both sides of the cylinder tube were summed up: through the bottom of the steam fed into the boiler through the upper discharged into the condenser. The condenser was a two tin tubes standing upright and interconnected at the top of a short horizontal tube with an opening valve overlap. The bottom of these tubes was joined with the third vertical tube, which served as a vent air pump. Tubes formed the refrigerator and air pump were placed in a small cylinder with cold water. Steam tube was connected to the boiler from which the steam produced in the cylinder. When the steam filled cylinder, the steam valve was closed and raised piston air pump capacitor, resulting in the condenser tubes of turned fully discharged space. Steam rushed into the tubes and condenses there, and the piston rises, pulling the load (as measured by effective work of the piston). Then, the discharge valve closed.
In 1768, Watt's big car was built on the basis of this model gornozavodchikov Rebuka mine, an invention which he received in 1769 his first patent. The most fundamental and important in his invention was the division of the steam cylinder and the condenser, so do not spend energy on a constant heating of the cylinder. The machine was more economical. Its efficiency has increased.
The next few years, Watt has been working hard on improving his engine. At the same time he had to overcome many difficulties, both financial and technical nature. He joined the company the owner of metalworking plant Bolton, who provided him with money. There were other problems: the engine demanded tightness and precise adjustment of parts to each other. The piston and the cylinder had to be ideally suited in size to prevent the leakage of steam. This accuracy was new to the engineering of the time, it was not even necessary precision machine tools. Undercut cylinders of large diameter seemed almost unsolvable problem. As a result, the first machines Watt worked satisfactorily: the cylinder was pulled out steam condensers acted badly, steam whistled through the hole in which the moving piston rod seeped between the piston and cylinder walls.
It was necessary to create special tools for boring cylinders. (In general, the creation of the steam engine marked the beginning of a real revolution in machine - to master the production of steam engines, mechanical engineering had to rise to a higher level.) Finally, all difficulties were overcome, and factory production of steam engines began since 1776. The car in 1776, compared with the construction in 1765 several important improvements have been made. A piston housed inside the cylinder, surrounded by a steam jacket (jacket). Due to this was reduced to a minimum of heat loss. Cover the top was closed, while the cylinder - opened. Steam is fed into the cylinder on the side of the boiler tube. The cylinder was connected to the condenser tube provided with a steam valve. This valve is somewhat higher and closer to the second cylinder was placed, the counterbalance valve. When both valves have been opened, the steam discharged from the boiler, filling all the space above and below the piston, forcing the air through the pipe in the condenser. When the valve is closed, the whole system remained in balance. Then the bottom outlet valve opened, the space under the piston separates from the condenser. Steam is directed from the space to the condenser is cooled and condensed. At the same time under the piston unloaded created space and the pressure dropped. On top of the continued pressure steam coming from the boiler. By its action of the piston coming down and performed useful work, which was transmitted by means of the balance of the pump rod. Once the piston fell to its lowest position, opening the top, balancing, valve. Steam again filled the space above and below the piston. Cylinder Pressure counterbalanced. Under the action of a counterweight located at the end of the balance, the piston freely raised up (not performing at the same time useful work). The entire process was continued in the same sequence. Although this machine Watt, as well as the Newcomen engine, remained one-sided, it was already an important difference - if the work is done Newcomen atmospheric pressure, then made her Watt steam. Increasing the vapor pressure, it was possible to increase the engine power and thus affect its operation. However, this does not eliminate the main disadvantage of this type of cars - they made only one working-class movement, worked in spurts, and therefore may only be used as pumps. 66 of these steam engines were built in 1775-1785 years.
To steam engine could drive the other cars, it was necessary that he created a uniform circular motion. The fundamental difference of such a machine was that the piston had to perform two working motion - back and forth. This engine was developed double-action by Watt in 1782. The steam is then produced from the one or the other side of the piston, and the space on the side opposite the inlet steam was connected with the condenser every time. This problem was solved with the help of an ingenious system of drain pipes, closed and opened by means of the spool.
The slide was a latch, which moved in front two holes for vapor transmission. Each course of the valve in one or the other side of the opening one port and closing other, thus changing his path that could take steam. The movement of the slide was a difficult character at each end position, where one hole is open and the other closed, he had to stop for a while to let a portion of the pair, and the average position of the place as quickly as possible. Movement of the spool managed by a special mechanism, located on the shaft. The main part of it was eccentric.
Eccentric invented Watt consisted of specially shaped plates seated on the shaft, located not in the center of the plate, but at some distance from it. With this mounting axis on one side of the plate it was greater than the other. Sama plate was covered by a ring, which is attached to the thrust, driving the spool. During the rotation of the plate its roundness constantly pressed to a new point within the surface of the ring and its wider side sets it in motion. With each turn of the shaft occurred one turn of the spool. The rotation of the ring (and thus thrust movement) depended on what shape is inserted in the cam plate. By calculation was chosen such form that during one revolution causes the acceleration, deceleration, the stop valve. The introduction of this device Watt did work his car is completely automatic.
For the first time the work of the engine watched worker whose duties include to regulate the flow of steam. If the engine is started to give too much momentum, it is a special flap overlaps several steam distribution pipe and the reduced vapor pressure. Then, this function has been entrusted to a special centrifugal regulator, arranged as follows. The movement of the working shaft pulley handed controller. When the latter began to spin too fast (and therefore excessively increased engine speed), the regulator balloons going up by centrifugal force and drives the valve sleeve and the lever, which limited the amount of steam. By reducing the speed the balls lowered and the valve opens.
In view of all these devices is easy to imagine the general principle of action of the machine. From the steam boiler through the pipe held in the space b, and thence due spool movement directed into the cylinder above the piston then B, then underneath. When couples come into the space above the piston latter fell, and fell under the piston, raised him. The steam pipe valve which was missed, according to need, more or less steam. The position of the valve regulated steam centrifugal regulator f. On the main shaft eccentric sat an e, SS rod which was held on the other side of the machine under the valve box and with a lever is lifted, then lowered the spool. The movement of the piston rod passed B O, which quite firmly held in the cylinder head, and from him - to the mobile rocker. At the opposite end of the beam was part G, which catches the bottom of the main shaft crank K. Thus, every time the ascent and descent of the piston descended one revolution of the shaft and the flywheel seated thereon L. The force transmitted from the main shaft by means of straps or other means to, where it should have been used. At the bottom of the machine is a capacitor. It consisted of a tank filled with water which is constantly renewed by the pump q, and tank D, where condensation occurred. Cold water is not only surrounded by the tank, and inject it through a plurality of small holes. Launched hot water is pumped by a water pump C. warm water to the drawer and a pump siphoned off Mm again in a steam boiler.
Creating a mechanism for transmitting the movement of the piston to the shaft, demanded by Watt tremendous effort. Many of the tasks they are allowed at all were on the border of the technical capabilities of the time. One problem in providing the necessary tightness. In the cylinder with a double effect, as opposed to a single-action cylinder, the two sides were to be closed. However, since the piston should have a connection with external parts, the left cover a circular opening in which a completely tight walked rod (rod) of the piston. Watt invented to invest in the lid tightly screwed thick namaslennoy tow, on which the rod slid without touching the metal cylinder. And the rod because of its smoothness rubbing very little. Another problem was the mechanism of the transformation of motion: as for the transmission of useful work done by the piston as it moves up, it was necessary that the piston rod is rigidly connected to the rocker. On all previous steam engines are connected chain. Now I have to think about how rigidly link the rod to move in a straight line, and the end of the rocker is moved in an arc. Watt has achieved this by creating a special transmission device, which is called a parallelogram Watt.
A rocker arm end is connected is hinged to a thrust ADB point B BC lever point C coupled with any stationary part of the engine. Thus, the entire system has two fixed pivot point: rocker center around which oscillates the rocker, and the C point around which revolved CB lever. Point A on the end of the balance and point B at the end of the lever CB made movement along the arcs described from the center of the balance from the point C. The point D on the ADB-drawn connecting the points A and B, the traffic passes very close to the vertical and straight. This point has been connected to the piston rod. Subsequently Watt perfected this transmitting device, receiving two points, connecting the linear motion. One of them he connected with a piston rod, and the other - with the stem of the auxiliary pump, engine maintenance. The creation of this transfer device required by Watt's so much effort that he considered it his greatest invention. He wrote: "While I do not particularly care about his fame, however, proud of the invention of the parallelogram more than any of my other inventions."
Then the oscillatory motion of the balance converted via the crank in rotation (as a crank mechanism was patented by Picard, in the first machines Watt oscillatory motion of the balance was converted into rotational created using Watt solar-planetary gear as soon as the Picard patent expired, started using the crank transmission). Due to the resulting all these transformations rotational movement of the working shaft of the new motor Watt suited for driving other working machines. This allowed him to play a revolutionary role in the development of large-scale machine industry. During 1785-1795 years, 144 of the steam engine was released, and in 1800 in England already operated 321 Watt steam engine. They are used in virtually all areas of production.
Great creation Watt was appreciated by his contemporaries and descendants. After the death of the inventor in 1819 the English Parliament has honored his memory structure of a marble monument in Westminster Abbey.