Laval reversible turbine Steam turbines owed their development as ship engines entirely to the persistent, persistent and long-term work of Parsons. Already in 1894, Parsons, after long and careful experiments, managed to design turbines

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In Pierre Laval Solzhenitsyn's behavior and political concepts are surprisingly similar to the behavior and views of the traitor to the French people, Pierre Laval. Both, in the name of “getting rid of” the “evil” existing in the state, advocated for the defeat of the nation. Both are apologists

A turbine is an engine in which the energy of water, steam and gas is converted into mechanical work through the rotating movement of the rotor. In a turbine, a jet of water or steam acts on special elements - blades - and sets them in motion. The blades are located along the entire circumference of the rotor.

Depending on the direction of the flow of water, steam or gas through the turbine, they are divided into axial - when the flow moves parallel to the axis of the turbine, and radial - the flow moves perpendicular to the axis.

The turbine is used in land, air and sea transport as an integral part of the engine, which increases its power. The turbine can also be used in power plants, where it serves as a drive for an electric generator.

Since ancient times, numerous attempts have been made to create various options turbines A description of a steam turbine designed by Heron of Alexandria in the 1st century AD has even survived to this day. But it was only at the end of the 19th century, when the level of thermodynamics, metallurgy and mechanical engineering had reached the necessary heights, that Charles Parsons and Gustaf Laval independently invented the first steam turbines suitable for production.

Below, in chronological order, is a brief history of the creation of various types of turbines.

The 1st century AD is the earliest surviving documentary evidence of the creation of a steam turbine by Heron of Alexandria. Unfortunately, this invention was considered a toy for a long time and the full potential of this turbine was never fully explored.

1500 - Leonardo da Vinci considered in his drawings the so-called “smoke umbrella”, the principle of which was as follows: the fire heated the air, which then rose through blades connected to each other. These blades rotated a regular roasting spit.

1551 - Taghi al-Din constructed a steam turbine, used as a power source for a self-rotating spit.

1629 - Italian engineer Giovanni Branca created a mill that worked due to the fact that a strong jet of steam rotated the turbine and the rotational motion was transmitted from the turbine to the gear - the driven mechanism.

1678 - Flemish scientist Ferdinand Verbiest developed the first self-propelled vehicle based on a steam engine. However, there is no evidence to prove that it was actually built.

1791 - Englishman John Barber developed a real gas turbine to drive a horseless carriage and received a patent for his invention.

1872 - Hungarian inventor Franz Stolz created the first gas turbine engine.

1890 - Swedish engineer and inventor Gustaf de Laval invented a nozzle that was intended to supply steam to a turbine. Subsequently it received his name and is used to this day for the same purpose.

1894 - Englishman Charles Parsons received a patent for the idea of ​​a ship - a steamship driven by a steam turbine. This principle of traction is still widely used today.

1895 - Three four-ton, 100 kW Parsons radial flux generators were installed at the Cambridge Power Station, which were used to provide electric lighting for city streets.

1903 - Norwegian Egidius Elling built the first gas turbine, capable of generating even more energy than was necessary for its operation. At that time, this was considered a serious achievement, because at that time they had no idea about thermodynamics. This gas turbine produced 11 hp. using rotating compressors.

1913 - Nikola Tesla received a patent for his Tesla turbine, based on the boundary layer effect.

1918 - General Electric, currently one of the leading turbine manufacturers, launched its own production for further sales gas turbines.

1920 - English engineer Alan Arnold Griffith changed the theory of gas flow into the theory of gas flow along an aerodynamic surface, which was more formalized and applicable to turbines.

1930 - English design engineer Frank Whittle received a patent for a universal gas turbine designed for jet propulsion. An engine with such a turbine was first used in April 1937.

1934 - Argentine engineer Raul Pateras Pescara patented a new invention - a piston engine, which is a generator for a gas turbine.

1936 - German designers Max Hahn and Hans von Ohain developed and patented their own new engine with a jet turbine in Germany. They were developing it at the same time as Frank Whittle in the UK.

Towards the end of the last century, the industrial revolution reached a turning point in its development. A century and a half earlier, steam engines had significantly improved - they could run on any type of fuel and drive a wide variety of mechanisms. A technical achievement such as the invention of the dynamo, which made it possible to obtain electricity in large quantities, had a great influence on the improvement of the design of steam engines. As human energy needs grew, so did the size of steam engines, until their dimensions were constrained by limitations on mechanical strength. For the further development of industry, a new method of obtaining mechanical energy was required.

This method appeared in 1884, when an Englishman (1854-1931) invented the first turbogenerator suitable for industrial use. Ten years later, Parsons began studying the possibility of using his invention for vehicles. Several years of hard work were crowned with success: the steamer Turbinia, equipped with a turbine, reached a speed of 35 knots - more than any ship in the Royal Navy. Compared to piston steam engines that use reciprocating piston motion, turbines are more compact and simpler in design. Therefore, over time, when power and efficiency. turbines have increased significantly; they have replaced engines of previous designs. Currently, all over the world, steam turbines are used in thermal power plants as drives for electric current generators. As for the use steam turbines as engines for passenger ships, their undivided dominance here came to an end in the first half of our century, when diesel engines became widespread. The modern steam turbine has inherited many of the features of the first machine invented by Parsons.

Reactive and active principles underlying the operation of a steam turbine. The first of them was used in the “aeolipil” (a) device, invented by Heron of Alexandria: the sphere in which the steam is located rotates due to the action of reaction forces arising when the steam leaves hollow tubes. In the second case (b), the steam jet directed at the blades is deflected and, as a result, the wheel rotates. The turbine blades (c) also deflect the steam jet; in addition, passing between the blades, the steam expands and accelerates, and the resulting reaction forces push the blades.

The operation of a steam turbine is based on two principles of creating a circumferential force on the rotor, known since ancient times - reactive and active. As early as 130 BC. Heron of Alexandria invented a device called the aeolipile. It was a hollow sphere filled with steam with two L-shaped nozzles located on opposite sides and directed towards different sides. Steam flowed out of the nozzles at high speed, and due to the resulting reaction forces, the sphere began to rotate.

The second principle is based on the conversion of the potential energy of steam into kinetic energy, which makes useful work. It can be illustrated by the example of Giovanni Branca's machine, built in 1629. In this machine, a jet of steam drove a wheel with blades, reminiscent of a water mill wheel.

The steam turbine uses both of these principles. A jet of high-pressure steam is directed onto curved blades (similar to fan blades) mounted on a disk. When flowing around the blades, the jet is deflected, and the disk with the blades begins to rotate. Between the blades, the steam expands and accelerates its movement: as a result, the steam pressure energy is converted into kinetic energy.

The first turbines, like Branca's machine, could not develop sufficient power because steam boilers were not capable of creating high pressure. The first operating steam engines of Thomas Savery, Thomas Newcomen and others did not require high pressure steam. Low pressure steam displaced the air under the piston and condensed, creating a vacuum. The piston lowered under the influence of atmospheric pressure, producing useful work. Experience in the construction and use of steam boilers for these so-called atmospheric engines gradually led engineers to design boilers capable of generating and withstanding pressures far in excess of atmospheric pressure.

With the advent of the opportunity to produce high-pressure steam, inventors again turned to the turbine. Various design options have been tried. In 1815, engineer Richard Trevithick tried to install two nozzles on the wheel rim of a steam locomotive engine and pass steam from the boiler through them. Trevithick's idea failed. A sawmill built in 1837 by William Avery in Syracuse (New York) was based on a similar principle. In England alone, in the 100 years from 1784 to 1884, 200 inventions related to turbines were patented, and more than half of these inventions were registered in the twenty-year period from 1864 to 1884.

None of these attempts resulted in the creation of an industrially suitable machine. These failures were partly due to ignorance of the physical laws governing the expansion of steam. The density of steam is much less than the density of water, and its “elasticity” is much greater, so the speed of the steam jet in steam turbines is much greater than the speed of water in the water turbines with which the inventors had to deal. It was found that the efficiency the turbine becomes maximum when the speed of the blades is approximately equal to half the speed of the steam; Therefore, the first turbines had very high rotation speeds.

The high number of revolutions was the cause of a number of undesirable effects, not least of which was the danger of destruction of rotating parts under the influence of centrifugal forces. The rotation speed of the turbine could be reduced by increasing the diameter of the disk on which the blades were mounted. However, this was impossible. The steam flow in early devices could not be large, which means that the cross-section of the outlet opening could not be large. Due to this reason, the first experimental turbines had a small diameter and short blades.

Another problem related to the properties of steam caused even more difficulties. The speed of steam passing through the nozzle varies proportionally to the ratio of the inlet pressure to the outlet pressure. Maximum value velocity in a convergent nozzle is achieved, however, at a pressure ratio of approximately two; a further increase in the pressure drop no longer affects the increase in jet speed. Thus, designers could not take full advantage of the power of high-pressure steam: there was a limit to the amount of energy stored in high-pressure steam that could be converted into kinetic energy and transferred to the blades. In 1889, the Swedish engineer Carl Gustav de Laval used a nozzle that expanded at the outlet. Such a nozzle made it possible to obtain much higher steam velocities, and as a result, the rotor speed in the Laval turbine increased significantly.

Parsons created a fundamentally new turbine design. It was distinguished by a lower rotation speed, and at the same time it made maximum use of steam energy. This was achieved due to the fact that in the Parsons turbine the steam expanded gradually as it passed through 15 stages, each of which was a pair of blade rims: one fixed (with guide blades attached to the turbine body), the other movable (with working blades). on a disk mounted on a rotating shaft). The blades of the fixed and movable rims were oriented in opposite directions, i.e. so that if both crowns were movable, then the steam would make them rotate in different directions.

The turbine blade rims were copper rings with blades fixed in slots at an angle of 45°. The movable rims were fixed on the shaft, the fixed ones consisted of two halves, rigidly connected to the body (the upper half of the body was removed).

Alternating movable and fixed rims of blades (a) set the direction of steam movement. Passing between the fixed blades, the steam expanded, accelerated and was directed to the movable blades. Here the steam also expanded, creating a force that pushed the blades. The direction of steam movement is shown on one of the 15 pairs of rims (b).

The steam directed to the fixed blades expanded in the interblade channels, its speed increased, and it was deflected so that it fell on the movable blades and forced them to rotate. In the interblade channels of the movable blades, the steam also expanded, an accelerated jet was created at the outlet, and the resulting reactive force pushed the blades.

With many movable and stationary blade rims, high rotation speeds have become unnecessary. At each of the 30 rims of the multi-stage Parsons turbine, the steam expanded slightly, losing some of its kinetic energy. At each stage (pair of rims) the pressure dropped by only 10%, and the maximum steam speed as a result turned out to be equal to 1/5 of the jet speed in a turbine with one stage. Parsons believed that with such small pressure differences, steam could be considered a low-compressibility liquid similar to water. This assumption enabled him to make calculations of steam speed and efficiency with a high degree of accuracy. turbines and blade shapes. The idea of ​​stepwise expansion of steam, which underlies the design of modern turbines, was only one of many original ideas embodied by Parsons.

Another invention was new type bearing designed specifically for a rapidly rotating shaft. Although Parsons managed to reduce the rotation speed of the turbine, it still remained ten times higher than that of other engines. Therefore, the inventor had to deal with a phenomenon known as “shaft runout.” Already at that time it was known that each shaft has its own characteristic critical rotation speed, at which even a small imbalance creates a significant bending force. It turned out that the critical rotation speed is related to the natural frequency of the transverse vibrations of the shaft (at this frequency the shaft begins to resonate and collapse). Parsons and de Laval independently discovered that at speeds above the critical speed, the shaft rotates steadily. Despite this, a slight imbalance still led to the deviation of the shaft from the equilibrium position. Therefore, in order to avoid damage to the shaft, it should be installed in bearings that would allow its small lateral displacements.

Parsons first tried using a regular bearing mounted on springs, but found that this design only increased the vibration. He eventually came up with a bearing consisting of a series of rings. Parsons used two sizes of rings: one that fit snugly against the bearing's inner shell (through which the shaft passed) but did not touch the housing; they alternated with other rings that fit snugly to the body without touching the liner. The entire system of rings was compressed in the longitudinal direction by a spring. This design allowed for small lateral movements of the shaft and at the same time suppressed vibration due to friction between the two types of washers.

The bearing on the shaft allowed small lateral displacements of the shaft, but damped vibrations. It consisted of alternating rings: some tightly covered the liner (within which the shaft passed) without touching the turbine body, others were pressed tightly against the body without touching the liner. The entire set of rings was pressed by a spring. The screw pump (on the left) drove oil ( yellow) into the bearing.

This design worked successfully, and those who saw the turbine example displayed at the Inventors' Exhibition in London in 1885 noted how smooth it was compared to other steam engines of the time. The latter shook the foundation so much that the vibration was felt even at a considerable distance from the car.

The Parsons turbine generator, built in 1884, was the first steam tube to be used industrially. High-pressure steam entered the turbine through a rectangular hole located near the middle of the shaft. Here it was divided and directed to opposite ends of the shaft, passing through the crowns of the blades. The expanding steam rotated movable (working) rings tightly seated on the central shaft. Between the movable rings there were rims of fixed blades mounted on inner surface turbine housings. Fixed blades directed steam to the blades of movable wheels.
In the inter-blade space of each wheel, the steam expanded. The principle of multi-stage steam expansion allowed Parsons to take full advantage of the energy of the high-pressure steam and avoid high numbers of revolutions. The shaft turned a dynamo, or electric generator (right).

In the Parsons turbine, steam was supplied through a control valve to the middle part of the shaft. Here the steam flow was divided and passed through two channels: one steam flowed to the left end of the shaft, the other to the right end. The volume of steam in both channels was the same. Each jet passed through the blade rims in the turbine.

One of the advantages that splitting the flow provided was that the longitudinal (axial) forces created by the steam pressure on the turbine blades were exactly balanced. Thus, there was no need for a thrust (axial) bearing. The described design is used in many modern steam turbines.

And yet, Parsons’s first multi-stage turbine developed a high speed - 18,000 rpm. At such speeds, the centrifugal force acting on the turbine blades was 13 thousand times greater than the force of gravity. To reduce the risk of rotating parts breaking, Parsons developed a very simple design: each disc was made from a solid copper ring; the grooves into which the blades fit were located around the circumference of the disk and were slots oriented at an angle of 45°. The movable disks were mounted on the shaft and fixed on its protrusion. The fixed rims consisted of two half-rings, which were attached to the top and bottom of the turbine housing. An increase in the volume of steam during its stepwise expansion required that the length of the blades along the steam flow be successively increased three times - from 5 to 7 mm. The edges of the blades have been beveled to improve the jet characteristics.

The problem of reducing the speed of rotation of the shaft gave rise to other inventions. The speeds were so high that it was impossible to solve this problem using the transmission mechanisms that existed at that time (such as gears). It was also impossible to use a simple centrifugal regulator, which was used on steam engines of earlier designs: the regulator balls would simply be torn off by centrifugal force. Parsons developed a completely new type of regulator. On the turbine shaft he placed a centrifugal fan connected to a system of tubes containing air. A rotating fan sucked air from the tubes, creating a vacuum in them. This vacuum was responded to by a leather diaphragm located on the other side of the tube system and connected to a control valve that controlled the supply of steam to the turbine. If the turbine rotation speed increased, the air vacuum in the tubes increased and the diaphragm bent more; as a result, the valve connected to the diaphragm reduced the supply of steam to the turbine and its rotation slowed down.

The regulator worked well, but was not very sensitive. The Parsons turbine drove a dynamo (electric generator). At the time Parsons built his turbine, one incandescent light bulb cost as much as a quarter ton of coal. To ensure that the lamps did not burn out during sudden changes in electric current (which often happened if steam engines were used), the dynamo had to ensure a constant voltage with an accuracy of 1-2%. For this purpose, Parsons equipped his turbine with a special precision adjustment mechanism that responded directly to changes in voltage on the dynamo.

The voltage on the dynamo winding is proportional to the strength of the magnetic field created at the poles. Parsons made a rocker arm from soft iron and fixed it over the poles of the dynamo, attaching a spring to it. The rocker, overcoming the resistance of the spring, sought to turn in the direction of the magnetic field; the angle of rotation depended directly on the field strength, which in turn was related to the voltage on the dynamo windings. A copper valve turned together with the rocker. Depending on its position, it more or less covered the hole of the tube included in the regulator system with a centrifugal fan,

If the magnetic field strength increased, the valve began to gradually block the opening of the tube. This reduced the access of air into the regulator system and increased the vacuum created by the centrifugal fan. At the same time, the leather diaphragm bent and the control valve reduced the steam supply to the turbine. Thus, the turbine rotation speed depended on the voltage on the dynamo windings. Parsons' fine adjustment mechanism was one of the first servos - feedback devices that control flow large quantity energy, consuming a small part of it.

High pressure steam (dark red) is introduced through an opening at the midpoint of the shaft and passes through the blade rims to both ends of the shaft. Exhaust steam (light red) enters two cavities connected by an outlet channel at the bottom of the housing. Even further from the center along the shaft axis there are two other cavities connected by a channel in the upper part of the housing; they maintain a partial vacuum (blue).

The couplings, which are tightly pressed against the inner surface of the housing due to the pressure difference between the cavities with exhaust steam and partial vacuum, do not allow the exhaust steam to escape out through the gaps at the surface of the rotating shaft. Lubrication is supplied by a screw pump (left), which forces oil (yellow) into the bearing on the shaft and to other bearings. The oil reaches the central bearings through a channel inside the dynamo shaft (in the center and on the right). The regulator uses a centrifugal fan (left) to create a vacuum (blue) in a system of tubes. A leather membrane connected to a valve that regulates the supply of steam to the turbine is attracted to them when there is a vacuum in the tubes.

The fine adjustment mechanism is located on top of the dynamo. This mechanism changes the air flow into the tube system depending on the voltage on the dynamo windings. Under the influence of vacuum created in the air tubes, oil from the bearings flows back into the vertical reservoir (left).

The centrifugal fan, which occupies the main place in the Parsons regulator, played important role and in the lubrication system. The high rotation speed of the turbine shaft required absolutely reliable lubrication. At the end of the shaft, Parsons attached a helical spiral, which was immersed in a reservoir of oil and provided lubricant to the bearings on the shaft. Tubes carried oil to the far end of the shaft where the dynamo was located, and a channel inside the dynamo shaft carried oil to the center bearings and cooled the internal parts of the dynamo. Under the influence of gravity, the oil returned to the central unit. The main oil reservoir was connected by a vertical tube to a system of air tubes located directly at the fan. The vacuum created by the fan caused oil to flow from the central unit back into the oil reservoir, so that the oil level was sufficient to operate the screw pump.

Another of Parsons' inventions, also used in modern turbines, was a method to eliminate steam leakage through the gaps between the shaft and the turbine housing. Any attempt to make a coupling that fits tightly to the shaft would be unsuccessful, since at a critical speed of rotation during acceleration, a lot of friction would be created as a result of beating. The coupling designed by Parsons fit the shaft tightly and at the same time allowed for slight displacement. Once operating speed was reached, the coupling acted as a reliable seal, keeping the exhaust steam inside the turbine housing.

As soon as the turbine reached operating speeds, the coupling was pressed tightly against the shaft under the influence of the pressure difference between the outlet pipe and the chamber where a partial vacuum was maintained. The exhaust steam came from two cavities (one at each end of the shaft) through an outlet channel at the bottom of the turbine housing. The other two cavities were located further from the midpoint of the shaft than each of the output cavities. A channel in the upper part of the body connected these outer cavities. Inside each of the two internal cavities, Parsons placed a coupling that tightly encloses the shaft. To maintain a partial vacuum in the outer cavities, Parsons used a steam jet pump. At a small number of turbine revolutions, the couplings rotated freely along with the shaft. Upon reaching operating speed, a pressure difference occurred between internal cavities(where the exhaust steam from the turbine entered) and the outer cavities (where a partial vacuum was maintained). Under the influence of a pressure difference, the couplings were pressed tightly against the turbine body and separated the cavities from each other.

What were the conditions under which Parsons’ talent was formed, thanks to which he was able to overcome the difficulties on the way to creating a turbine? Parsons was the youngest son of a family that received land in Birra, County Offaly, Ireland. His father, the third Earl of Ross, was a talented scientist. He made major contributions to casting and grinding technology large mirrors for telescopes. In 1845, in a workshop on his estate, he built a reflecting telescope, which for several decades remained the largest telescope in the world. Using this telescope, Parsons Sr. discovered a number of spiral nebulae. From 1849 to 1854 he was president of the Royal Society of London. As a member of parliament, in order to attend meetings, he bought a house in London. The whole family lived here for part of the year, hosting receptions to which representatives of the scientific community were invited.

The Parsons did not send their children to school. Their teachers were astronomers, whom the count invited for night observations using telescopes; V daytime these scientists taught children. Children were also strongly encouraged to engage in home workshops. The craft, to which Charles was introduced since childhood, played an extremely important role during the period when he built his turbine.

Charles entered Trinity College in Dublin, and then moved to St. John's College, Cambridge University, from which he graduated in 1877. He studied mathematics under the guidance of Edward E. Root, who at that time was studying the conditions for the conservation of uniform motion, in particular using various mechanical regulators for these purposes.

Up until this time, Parsons enjoyed the benefits of his privileged upbringing. A turning point in his fortunes came when he became an apprentice to George Armstrong, a famous manufacturer of naval guns, and began working at his Elswick factory in Newcastle-upon-Tyne. The reasons that prompted Parsons to make such a decision remained unknown: at that time, children from wealthy families rarely chose a career in engineering.

Parsons gained a reputation as Armstrong's hardest-working student. During his internship, he received permission to work on the latest innovation - a steam engine with rotating cylinders - and between 1877 and 1882. Patented several of his inventions. If these patents are examined, it can be established that he used the idea of ​​pressure lubrication a decade earlier than A. Payne, who is famous for his inventions in this field. Before Parsons, drippers were used to lubricate bearings, so bearings required constant monitoring. The idea of ​​forced lubrication played an exceptional role in the creation of high-speed machines, in particular turbines

The idea of ​​​​creating a turbine came to Parsons, apparently, when he was still a student. Lord Rayleigh recounts the words of one of Parsons' acquaintances at Cambridge, to whom the future inventor showed a toy paper engine: when Parsons blew on the wheels of the toy, they rotated. Parsons said that the rotation speed of this machine would be "ten times more than any other."

Parsons began conducting his first real experiments with turbines while working for Armstrong. From 1881 to 1883, i.e. Immediately after his internship, he collaborated with James Kilson to develop a gas-powered torpedo. Armstrong was largely involved in the naval weapons industry and probably supported efforts to develop a new type of torpedo propulsion. The peculiarity of this propulsion device was that the burning fuel created a jet of high pressure gas. The jet hit the impeller, causing it to rotate. The impeller, in turn, rotated the torpedo propeller.

There is no explicit indication of the design of the impeller in Parsons's notebooks, but some idea of ​​it can be gained by examining a small boat Parsons made from sheet copper. The boat was driven by a three-blade propeller located under the hull. The screw was located inside big ring with 44 spiral slots. The gas escaping in a stream passed through these slots, and due to the force created when the flow was deflected, the ring began to rotate. The propeller rotated along with it, pushing the boat forward.

So, Parsons conducted his early experiments with gas turbines, not steam turbines. He stopped working on them in 1883, although his 1884 patent describes the modern operating cycle of a gas turbine. He subsequently gave an explanation for this.

"Experiments carried out many years ago - he wrote, - and partly with the goal of verifying the reality of the gas turbine, convinced me that with the metals that we had at our disposal... it would be a mistake to use a hot stream of gases - either in pure form or mixed with water - to drive the blades into rotation or ferry."

This was a prescient observation: it was only ten years after Parsons' death that metals were available that were suitable for making gas turbines.

Early in 1884, Parsons became a junior partner in the firm of Clarke Chapman and Company. Settling in Gateshead, he began designing a steam turbine. His notes from experiments on creating a torpedo dating back to August 1883 indicate that at that time he had not yet come to the idea of ​​​​the need to bring the speed of rotation of the blades to the speed of the gas jet. The problem of creating a nozzle with a large pressure ratio at the inlet and outlet did not occupy his attention either. But already in April 1884 he filed two preliminary patents, and in October and November of the same year he gave a full description of the invention.

It was an incredibly productive period for Parsons. He not only had to experiment with high-speed shafts and other turbine parts, but also think about possible ways to use the energy of his machine. With a rotation speed of 18,000 rpm, it could not be used for ordinary purposes. Parsons decided to create a dynamo powered by a turbine at high speeds that few modern electric machines can achieve. Subsequently, Parsons often repeated that this invention was as important as the creation of the turbine itself. To this day, the main application of the steam turbine remains to drive electric generators.

THE EARLY steam turbines were not particularly efficient. Until their power output could match the efficiency of conventional steam engines, they had to be made attractive to buyers through other characteristics. Such attractive features were their small size, stability of electrical voltage, reliable operation in the absence of control and low operating costs. The first turbine had all these features.

In November 1884, when the first turbine was created, the Honorable Charles A. Parsons was only 30 years old. Engineering genius and an instinct for the needs of the market in themselves were not a sufficient condition for his brainchild to successfully enter into life. At a number of stages, Parsons had to invest his own funds so that the work done would not be in vain. During a trial in 1898 to extend the life of some of his patents, it was found that Parsons spent personal money in the amount of 1,107 pounds 13 shillings and 10 pence to create the turbine.

"Turbinia" is the first steamship with a turbine engine. It was launched in 1894.
The steamer developed a record speed of up to 35 knots.
Subsequently, turbines began to be used on large ships.

Invention of steam turbines.

Along with the hydraulic turbines described in one of the previous chapters, the invention and spread of steam turbines was of great importance for energy and electrification. The principle of their operation was similar to hydraulic ones, with the difference, however, that the hydraulic turbine was driven by a stream of water, and the steam turbine was driven by a stream of heated steam. Just as the water turbine represented a new word in the history of water engines, the steam turbine demonstrated new capabilities of the steam engine.

Watt's old car, marked in the third quarter of the XIX century, its centenary, had low efficiency, since the rotational movement was obtained in a complex and irrational way. In fact, as we remember, the steam did not move the rotating wheel itself, but exerted pressure on the piston; from the piston, through the rod, connecting rod and crank, the movement was transmitted to the main shaft. As a result of numerous transfers and transformations, a huge part of the energy obtained from fuel combustion, in the full sense of the word, flew down the drain without any benefit. More than once, inventors tried to design a simpler and more economical machine - a steam turbine, in which a jet of steam would directly rotate the impeller. A simple calculation showed that it should have an efficiency several orders of magnitude higher than Watt's machine. However, there were many obstacles in the way of engineering thought. For a turbine to truly become a highly efficient engine, the impeller had to rotate at very high speeds, making hundreds of revolutions per minute. For a long time they could not achieve this, since they did not know how to impart the proper speed to the steam jet.

The first important step in developing a new technical means, which supplanted the steam engine, was made by the Swedish engineer Carl Gustav Patrick Laval in 1889. The Laval steam turbine is a wheel with blades. The stream of water generated in the boiler escapes from the pipe (nozzle), presses on the blades and spins the wheel. Experimenting with different steam supply tubes, the designer came to the conclusion that they should have a cone shape. This is how the Laval nozzle, used to this day, appeared.

It was only in 1883 that the Swede Gustav Laval managed to overcome many difficulties and create the first working steam turbine. A few years earlier, Laval received a patent for a milk separator. In order to power it, a very high-speed drive was needed. None of the engines that existed at that time met the task. Laval became convinced that only a steam turbine could give him the required rotation speed. He began to work on its design and eventually achieved what he wanted. Laval's turbine was a light wheel, onto the blades of which steam was induced through several nozzles placed at an acute angle. In 1889, Laval significantly improved his invention by adding conical expanders to the nozzles. This significantly increased the efficiency of the hydraulic turbine and turned it into a universal engine.

The principle of operation of the turbine was extremely simple. Steam, heated to a high temperature, came from the boiler through a steam pipe to the nozzles and burst out. In the nozzles, the steam expanded to atmospheric pressure. Due to the increase in volume that accompanied this expansion, a significant increase in the flow rate was obtained (with an expansion from 5 to 1 atmosphere, the speed of the steam jet reached 770 m/s). In this way, the energy contained in the steam was transferred to the turbine blades. The number of nozzles and steam pressure determined the power of the turbine. When the exhaust steam was not released directly into the air, but was directed, as in steam engines, into a condenser and liquefied under reduced pressure, the turbine power was greatest. Thus, when steam expanded from 5 atmospheres to 1/10 atmosphere, the jet speed reached supersonic values.

Despite its apparent simplicity, the Laval turbine was a real miracle of engineering. It is enough to imagine the loads that the impeller experienced in it to understand how difficult it was for the inventor to get uninterrupted operation from his brainchild. At enormous speeds of the turbine wheel, even a slight shift in the center of gravity caused a strong load on the axle and overloaded the bearings. To avoid this, Laval came up with the idea of ​​putting the wheel on a very thin axle, which could bend slightly when rotating. When unwinding, it automatically came into strict central position, then held at any rotation speed. Thanks to this ingenious solution, the destructive effect on the bearings was reduced to a minimum.

As soon as it appeared, the Laval turbine won universal recognition. It was much more economical than old steam engines, very easy to use, took up little space, and was easy to install and connect. The Laval turbine provided especially great benefits when combined with high-speed machines: saws, separators, centrifugal pumps. It was also successfully used as a drive for an electric generator, but still it had an excessively high speed for it and therefore could only operate through a gearbox (a system of gear wheels that reduced the rotation speed when transmitting motion from the turbine shaft to the generator shaft).

In 1884, the English engineer Parson received a patent for a multi-stage jet turbine, which he invented specifically to drive an electric generator. In 1885, he designed a multi-stage jet turbine, which was later widely used in thermal power plants. It had the following device, reminiscent of a jet hydraulic turbine. A series of rotating wheels with blades was mounted on the central shaft. Between these wheels there were fixed rims (disks) with blades that had the opposite direction. Steam under high pressure was brought to one end of the turbine. The pressure at the other end was small (less than atmospheric). Therefore, the steam tended to pass through the turbine. First, it entered the spaces between the blades of the first crown. These blades directed it to the blades of the first movable wheel. Steam passed between them, causing the wheels to rotate. Then he entered the second crown. The blades of the second crown directed steam between the blades of the second movable wheel, which also began to rotate. From the second movable wheel, steam flowed between the blades of the third rim, and so on. All blades were given such a shape that the cross-section of the interblade channels decreased in the direction of steam flow. The blades seemed to form nozzles mounted on a shaft, from which, expanding, steam flowed out. Both active and reactive power were used here. Rotating, all the wheels rotated the turbine shaft. The outside of the device was enclosed in a strong casing. In 1889, about three hundred of these turbines were already used to generate electricity, and in 1899 the first power station with Parson steam turbines was built in Elberfeld. Meanwhile, Parson tried to expand the scope of his invention. In 1894, he built an experimental ship, the Turbinia, powered by a steam turbine. During testing, it demonstrated a record speed of 60 km/h. After this, steam turbines began to be installed on many high-speed ships.

Let's imagine a closed metal vessel (boiler) partially filled with water. If you light a fire under it, the water will begin to heat up and then boil, turning into steam. The pressure inside the boiler will increase, and if its walls are not strong enough, it may even explode. This shows that the pair has accumulated a reserve of energy, which finally manifests itself in an explosion. Is it possible to force steam to do any useful work? This question has occupied scientists for a very long time. The history of science and technology knows many interesting inventions in which man sought to use steam energy. Some of these inventions were useful, others were just clever toys, but at least two inventions must be called great; they characterize entire eras in the development of science and technology. These great inventions are the steam engine and the steam turbine. The steam engine, which received industrial use in the second half of the 18th century, revolutionized technology. It quickly became the main engine used in industry and transport. But in late XIX and the beginning of the 20th century. the achievable power and speed of the steam engine had already become insufficient.

There is an urgent need for the construction of large power stations, for which a powerful and high-speed engine was needed. Such an engine was the steam turbine, which can be built to produce enormous power at high speeds. The steam turbine quickly replaced the steam engine from power plants and large steamships.

The history of the creation and improvement of the steam turbine, like any major invention, is associated with the names of many people. Moreover, as is usually the case, the basic operating principle of the turbine was known long before the level of science and technology allowed the construction of a turbine.

The principle of operation of a steam engine is to use the elastic properties of steam. Steam periodically enters the cylinder and, expanding, does work by moving the piston. The operating principle of a steam turbine is different. Here the steam expands, and the potential energy accumulated in the boiler is converted into high-speed (kinetic) energy. In turn, the kinetic energy of the steam jet is converted into mechanical energy of rotation of the turbine wheel.

The history of turbine development begins with the ball of Heron of Alexandria and the Branca wheel. The possibility of using steam energy to produce mechanical movement was noted by the famous Greek scientist Heron of Alexandria more than 2000 years ago. He built a device called Heron's ball (Fig. 1).

The ball could rotate freely in two supports made of tubes. Through these supports, steam from the boiler entered the ball and then exited into the atmosphere through two tubes bent at right angles. The ball rotated under the action of reactive forces arising from the flow of steam jets.

Another project is described in the work of the Italian scientist Giovani Branca (1629). IN top part boiler tube is inserted (Fig. 2).

Since the steam pressure inside the boiler is greater than atmospheric pressure air around the boiler, the steam rushes out through the tube.

A stream of steam shoots out from the free end of the tube and hits the wheel blades, causing it to rotate.

Heron's model and Branca's wheel were not engines, but they already indicated possible ways obtaining mechanical movement due to the energy of the driving steam.

There is a difference in the operating principles of Heron's ball and Branca's wheel. Heron's ball, as already mentioned, rotates under the action of reactive forces. These are the same forces that push a rocket. It is known from mechanics that a jet pushed out of a vessel under the influence of pressure, for its part, presses on the vessel in the direction opposite to the direction of outflow. This is obvious based on Newton's third law, according to which the force pushing out the jet must be equal and opposite in direction to the reaction force of the jet on the vessel.

In the Branca turbine, the potential energy of the steam is first converted into the kinetic energy of the jet gushing from the tube. Then, when the jet hits the wheel blade, part of the kinetic energy of the steam is converted into mechanical energy of rotation of the wheel.

If Heron's ball moves by reactive forces, then the Branca turbine uses the so-called active principle, since the wheel draws energy from the active jet.

The greatest shift in the design of the steam turbine and its further development occurred at the end of the century before last, when in Sweden engineer. Gustav Laval and in England Charles Parsons independently began to work on the creation and improvement of the steam turbine. The results they achieved allowed the steam turbine to eventually become the main type of engine for driving electric current generators and to be widely used as an engine for civil and military ships. In the Laval steam turbine, created in 1883, steam enters one or more parallel-connected nozzles, acquires significant speed in them and is directed to working blades located on the rim of a disk sitting on the turbine shaft and forming a lattice of working channels.

The forces caused by the rotation of the steam jet in the channels of the working grid rotate the disk and the turbine shaft associated with it. A distinctive feature of this turbine is that the expansion of steam in the nozzles from initial to final pressure occurs in one stage, which causes very high steam flow rates. The conversion of the kinetic energy of steam into mechanical energy occurs without further expansion of the steam only due to a change in the direction of flow in the blade channels.

Turbines built on this principle, i.e. turbines in which the entire process of steam expansion and associated acceleration of steam flow occurs in stationary nozzles are called active turbines.

During the development of active single-stage turbines, a number of complex issues were resolved, which had an extremely great value for further development of steam turbines. Expanding nozzles were used, which allow a greater degree of steam expansion and allow high steam flow velocities to be achieved (1200-1500 m/sec). To make better use of high steam flow rates, Laval developed a design of an equal-resistance disk that allowed operation at high peripheral speeds (350 m/sec). Finally, in the single-stage active turbine such high speeds were used (up to 32,000 rpm), which far exceeded the speeds of engines common at that time. This led to the invention of a flexible shaft, the frequency of free vibrations of which is less than the frequency of disturbing forces at the operating speed.

Despite a number of new constructive solutions, used in single-stage active turbines, their efficiency was low. In addition, the need to use a gear transmission to reduce the speed of the drive shaft to the level of the speed of the driven machine also hampered the development of single-stage turbines at that time and, in particular, the increase in their power. Therefore, Laval turbines, having received significant distribution at the beginning of the development of turbine construction as low-power units (up to 500 kW), later gave way to other types of turbines.

The steam turbine proposed in 1884 by Parsons is fundamentally different from the Laval turbine. The expansion of steam in it is carried out not in one nozzle group, but in a number of successive stages, each of which consists of stationary guide vanes (nozzle arrays) and rotating blades.

The guide vanes are fixed in the stationary turbine housing, and the rotor blades are arranged in rows on the drum. Each stage of such a turbine experiences a pressure drop that is only a small fraction of the total difference between the fresh steam pressure and the pressure of the steam leaving the turbine. Thus, it was possible to operate with low steam flow velocities in each stage and with lower peripheral speeds of the rotor blades than in the Laval turbine. In addition, the expansion of steam in the stages of a Parsons turbine occurs not only in the nozzle, but also in the working grid. Therefore, forces are transmitted to the working blades, caused not only by a change in the direction of steam flow, but also by the acceleration of steam within the working grid, causing a reactive force on the turbine working blades.

Turbine stages in which steam expansion and the associated acceleration of steam flow in the channels of the working blades are used are called reaction stages. Thus, shown in Fig. 4 turbine was a typical representative of multi-stage jet steam turbines.

The principle of sequential inclusion of stages, each of which uses only part of the available thermal difference, turned out to be very fruitful for the subsequent development of steam turbines. It made it possible to achieve high efficiency in the turbine at moderate speeds of the turbine rotor, allowing direct connection of the turbine shaft with the shaft of the electric current generator. The same principle made it possible to manufacture turbines of very high power, reaching several tens and even hundreds of thousands of kilowatts in one unit.

Multistage jet turbines are now widespread, both in stationary installations and in the fleet.

The development of active steam turbines also followed the path of sequential expansion of steam not in one, but in a number of stages located one after another. In these turbines, a number of disks mounted on a common shaft are separated by partitions called diaphragms, in which fixed nozzle grids are located. In each of the stages constructed in this way, the steam expands within a portion of the total available heat loss. In the working grids, only the conversion of the kinetic energy of the steam flow occurs without additional expansion of the steam in the channels of the working blades. Active multistage turbines are widely used in stationary installations; they are also used as marine engines.

Along with turbines in which steam moves in the direction of the turbine shaft axis (axial), designs of radial turbines were created in which steam flows in a plane perpendicular to the turbine axis. Of the latter, the most interesting is the radial turbine, proposed in 1912 in Sweden by the Ljungström brothers.

Rice.

1,2 - turbine disks; 3 - fresh steam lines; 4, 5 - turbine shafts; 6, 7 - blades of intermediate stages

On the side surfaces of disks 1 and 2, the blades of the jet stages are located in rings of gradually increasing diameter. Steam is supplied to the turbine through pipes 3 and then through holes in disks 1 and 2 to the central chamber. From here it flows to the periphery through the channels of the blades 6 and 7, mounted on both disks. Unlike conventional design There are no fixed nozzle grilles or guide vanes in the Jungström turbine. Both disks rotate in counter directions, so the power developed by the turbine must be transmitted by shafts 4 and 5. The principle of counter-rotation of the rotors allows the turbine to be very compact and economical.

Since the early 1990s, the development of steam turbines has proceeded at an exceptionally rapid pace. This development was largely determined by the equally rapid parallel development of electrical machines and the widespread introduction of electrical energy into industry. The efficiency of a steam turbine and its power in one unit have reached high values. The power of the turbines far exceeded the power of all other types of engines without exception. Turbines with a capacity of 500 MW are available, connected to an electric current generator, and the possibility of producing even more powerful units, at least up to 1000 MW, has been proven.

In the development of steam turbine construction, several stages can be noted that affected the design of turbines built in different periods of time.

In the period before the imperialist war of 1914, the level of knowledge in the field of metal work at high temperatures was insufficient for the use of steam at high pressures and temperatures. Therefore, until 1914, steam turbines were built primarily to operate with moderate pressure steam (12 - 16 bar), with temperatures up to 350 °C.

In terms of increasing the power of a single unit, great success was achieved already in the initial period of development of steam turbines.

In 1915, the power of individual turbines already reached 20 MW. In the post-war period, starting from 1918-1919, the trend towards increasing power continues. However, in the future, turbine designers pursued the task of increasing not only the power of the unit, but also the speed of high-power turbines when running them with a single electric current generator.

The most powerful high-speed turbine in the world at one time (1937) was the turbine of the Leningrad Metal Plant, built at 100 MW at 3000 rpm.

In the period before the imperialist war of 1914, turbine factories in most cases produced turbines with a limited number of stages located in one turbine housing. This made it possible to make the turbine very compact and relatively cheap. After the 1914 war, the tension in fuel supply that most countries experienced required a comprehensive increase in the efficiency of turbine units.

It was found that maximum turbine efficiency can be achieved by using small thermal differences in each turbine stage and, accordingly, building turbines with a large number of stages. In connection with this trend, turbine designs arose that, even with moderate fresh steam parameters, had an extremely large number of stages, reaching 50 - 60.

The large number of stages led to the need to create turbines with several casings, even when the turbine was connected to a single electric generator.

Thus, two- and three-casing turbines began to spread, which, while highly economical, were very expensive and bulky.

In the subsequent development of turbine construction, there was also a certain retreat in this matter towards simplifying the design of the turbine and reducing the number of its stages. Turbines with a power of up to 50 MW at 3000 rpm were built only with two casings for quite a long time. The newest condensing turbines of this power, produced by leading factories, are built with single casings.

Simultaneously with the design improvements of moderate pressure turbines (20 - 30 bar), more economical high pressure units, reaching 120 - 170 bar, began to spread in the period from 1920 to 1940.

The use of steam with high parameters, which significantly increases the efficiency of a turbine installation, required new solutions in the field of designing steam turbines. Significant progress has been made in the use of alloy steels, which have a fairly high yield strength and low creep rates at temperatures of 500 - 550 ° C.

Along with the development of condensing turbines, already at the beginning of this century, installations for the combined generation of electrical energy and heat began to be used, which required the construction of turbines with back pressure and intermediate steam extraction. The first turbine with constant pressure control of the extracted steam was built in 1907.

The conditions of a capitalist economy, however, prevent the use of all the advantages of combined heat and electricity generation. In fact, the thermal consumption capacity abroad is in most cases limited to the consumption of the plant where the turbine is installed. Therefore, turbines that allow the use of exhaust steam heat are most often built abroad for small powers (up to 10 - 12 MW) and are designed to provide heat and electrical energy only to individual industrial enterprise. It is characteristic that the largest (25 MW, and then 50 and 100 MW) turbines with steam extraction were built in the Soviet Union, since the planned development of the national economy creates favorable conditions for the combined production of heat and electrical energy.

In the post-war period, all technically developed European countries, as well as the United States, have seen an ever-accelerating development of energy, which leads to an ever-increasing increase in the power of energy units. At the same time, the tendency to use increasingly higher initial steam parameters continues.

Single-shaft condensing turbines reach a power of 500 - 800 MW, and with a two-shaft design, installations with a capacity of 1000 MW have already been built.

As the power increased, it was also advisable to increase the initial steam parameters, which were successively selected at the level of 90, 130, 170, 250 and, finally, 350 bar, while the initial temperatures also increased, which amounted to 500, 535, 565, 590, and in some cases up to 650° C. It should be borne in mind that at temperatures exceeding 565° C, it is necessary to use very expensive and less studied austenitic steels. This led to the fact that lately there is a tendency towards a slight retreat into the temperature range that eliminates the need to use austenitic steels, i.e. temperatures at 540° C.

The successes achieved in 1915-1920 were of great importance for the development of low-power turbines and, in particular, for the development of ship steam turbines. in the field of gearbox construction. Until this time, ship turbines were operated at a number of revolutions equal to the number of revolutions of the propellers, i.e. 300 - 500 rpm, which reduced the efficiency of the installation and led to large dimensions and weights of the turbines.

Since the time when complete reliability and high efficiency were achieved in the operation of gear reducers, ship turbines have been equipped with gear drives and are operated at an increased speed, which corresponds to the most favorable operating conditions of the turbine.

For stationary low-power turbines, it also turned out to be advisable to use a gear transmission between the turbine and the generator. The highest speed possible with direct connection of the turbine shafts and the 50-period alternating current generator is 3000 rpm. At powers below 2.5 MW, this speed is unfavorable for a condensing turbine. With the development of gearbox technology, it became possible to manufacture turbines at higher speeds (5000-10000 rpm), which made it possible to increase the efficiency of low-power turbines, and most importantly, reduce their size and simplify their design.