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 construct turbines

TURBINE Nika TURBINE Nika (poet; committed suicide (jumped out of a window) on May 11, 2002 at the age of 28; buried at the Vagankovskoye cemetery in Moscow). Turbina became famous in the mid-80s, when her poems began to be published in all Soviet media. At the age of 12 Nika

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

The history of technology is full of examples where inventors from different countries worked independently to solve a common problem. A striking example of such “international cooperation” is the creation of a steam turbine.

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 (1845-1913).

He was French by origin, but his ancestors date back to the 16th century. left France for Sweden to escape religious persecution. Thanks to his sharp mind and extraordinary abilities, Laval brilliantly defended his doctoral dissertation immediately after graduating from Uppsala University in 1872. His first inventions were improvements in chemical and mining technologies. For these inventions, the engineer received several dozen patents. In 1878, Laval designed a milk separator (lat. separator - “separator”). The principle of operation of the device is simple. The milk container must rotate at a speed of more than 100 rpm. Centrifugal force will throw water towards the walls of the container, lighter fat will collect in the center, as a result, the cream and skim milk will separate. But how do you get the speed you need? In search of an answer to this question, the scientist invented a steam turbine. It was built in 1889.

The Laval steam turbine is a wheel with blades. A stream of steam generated in the boiler escapes from the pipe (nozzle), presses on the blades and spins the wheel. Experimenting with different tubes for supplying steam, the designer came to the conclusion that they should have a cone shape. This is how the Laval nozzle, which is still used today, appeared (patent 1889). The inventor made this important discovery rather intuitively; it took several more decades for theorists to prove that a nozzle of this particular shape gives the best effect.

The next step in the development of turbines was made by the English inventor Charles Algernon Parsons (1854-1931).

When Laval was already working on the creation of a turbine, Parsons was still studying at Cambridge University. He, as befits a representative of an aristocratic family (his father Lord Ross was a famous astronomer and public figure), received a diverse education. He began working on turbines in 1881, and three years later he was given a patent for his own design; Parsons connected a steam turbine with an electrical energy generator. With the help of a turbine it became possible to generate electricity, and this immediately increased public interest in steam turbines.

As a result of 15 years of research, Parsons created the most advanced multi-stage jet turbine at that time. He made several inventions that increased the efficiency of this device (he improved the design of the seals, methods of fastening the blades in the wheel, and the speed control system).

Soon, the French scientist Oposte Rato (1863-1930), summarizing the existing experience, created a comprehensive theory of turbomachines.

He developed an original multi-stage turbine, which was successfully demonstrated at the World Exhibition held in the capital of France in 1900. For each stage of the turbine, Rato calculated the optimal pressure drop, which ensured a high overall coefficient useful action cars.

Since 1900, the famous company "West Inhouse" began producing turbines new system American inventor Glenn Curtis (1879-1954). In his machine, the turbine rotation speed was lower, and the steam energy was used more fully. Therefore, Curtis turbines were smaller and more reliable in design.

One of the main areas of application of steam turbines is ship propulsion systems. The first ship with a steam turbine engine, the Turbinia, built by Parsons in 1894, reached speeds of up to 32 knots (about 59 km/h).

Since 1900, turbines began to be installed on destroyers, and after 1906, all large warships were equipped with turbine engines. In the same year, 1906, two large passenger transatlantic liners with turbine units were launched - the Lusitania and the Mauretania.

It was not for nothing that the nineteenth century was called the age of steam. With the invention of the steam engine, a real revolution took place in industry, energy, and transport. It became possible to mechanize work that previously required too many human hands. Railways dramatically expanded the possibilities of transporting goods by land. Huge ships took to the sea, capable of moving against the wind and guaranteeing the timely delivery of goods. Expansion of volumes industrial production set the energy industry the task of increasing engine power in every possible way. However, initially it was not high power that brought the steam turbine to life...

The hydraulic turbine as a device for converting the potential energy of water into the kinetic energy of a rotating shaft has been known since ancient times. The steam turbine has an equally long history, as one of the first designs is known as the “Heronian turbine” and dates back to the first century BC. However, let us immediately note that until the 19th century, turbines driven by steam were more likely technical curiosities, toys, than real industrially applicable devices.

And only with the beginning of the industrial revolution in Europe, after the widespread practical introduction of D. Watt’s steam engine, inventors began to take a closer look at the steam turbine, so to speak, “closely.” The creation of a steam turbine required deep knowledge physical properties of steam and the laws of its flow. Its manufacture became possible only with a sufficiently high level of technology for working with metals, since the required manufacturing accuracy individual parts and the strength of the elements were significantly higher than in the case of a steam engine.

Unlike a steam engine, which performs work by using the potential energy of steam and, in particular, its elasticity, a steam turbine uses the kinetic energy of a steam jet, converting it into rotational energy of the shaft. The most important feature of water vapor is its high rate of flow from one medium to another, even with a relatively small pressure difference. Thus, at a pressure of 5 kgf/m2, the steam jet flowing from the vessel into the atmosphere has a speed of about 450 m/s. In the 50s of the last century, it was found that in order to effectively use the kinetic energy of steam, the peripheral speed of the turbine blades at the periphery must be at least half the speed of the blowing jet; therefore, with a turbine blade radius of 1 m, it is necessary to maintain a rotation speed of about 4300 rpm . The technology of the first half of the 19th century did not know bearings capable of withstanding such speeds for a long time. Relying on your own practical experience, D. Watt considered such high speeds of movement of machine elements unattainable in principle, and in response to a warning about the threat that a turbine could create for the steam engine he invented, he answered: “What kind of competition can we talk about if, without the help of God, it is impossible to force the workers parts move at 1000 feet per second?”

However, time passed, technology improved, and the hour for the practical use of the steam turbine struck. Primitive steam turbines were first used in sawmills in the eastern United States in 1883-1885. for drive circular saws. Steam was supplied through the axis and then, expanding, was directed through pipes in the radial direction. Each of the pipes ended with a curved tip. Thus, in design, the described device was very close to the Heron turbine, had extremely low efficiency, but was more suitable for driving high-speed saws than a steam engine with its reciprocating piston movement. In addition, to heat the steam, according to the concepts of that time, waste fuel was used - sawmill waste.

However, these first American steam turbines were not widely used. Their influence on the further history of technology is practically absent. The same cannot be said about the inventions of the Swede of French origin, de Laval, whose name is known to any engine specialist today.

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Carl Gustav Patrick de Laval

De Laval's ancestors were Huguenots who were forced to emigrate to Sweden in late XVI centuries due to persecution in their homeland. Carl Gustav Patrick (“the main name” was still considered Gustav) was born in 1845 and received an excellent education, graduating from the Institute of Technology and University in Uppsala. In 1872, de Laval began working as a chemical and metallurgical engineer, but soon became interested in the problem of creating an effective milk separator. In 1878, he managed to develop a successful version of the separator design, which became widespread; Gustav used the proceeds to expand work on a steam turbine. It was the separator that gave the impetus to work on the new device, since it needed a mechanical drive capable of providing a rotation speed of at least 6000 rpm.

In order to avoid the use of any kind of multipliers, de Laval proposed placing the separator drum on the same shaft with a simple jet-type turbine. In 1883, an English patent was taken out for this design. De Laval then moved on to develop a single-stage active turbine, and already in 1889 he received a patent for an expanding nozzle (and today the term “Laval nozzle” is in common use), which allows reducing the steam pressure and increasing its speed to supersonic. Soon after, Gustav was able to overcome other problems that arose in the production of a functional active turbine. So, he proposed using a flexible shaft and a disk of equal resistance and developed a method for securing the blades in the disk.

At the International Exhibition in Chicago, held in 1893, a small de Laval turbine with a power of 5 hp was presented. with a rotation speed of 30,000 rpm! The enormous rotation speed was an important technical achievement, but at the same time it became the Achilles heel of such a turbine, since for practical use it required the inclusion of a reduction gear in the power plant. At that time, gearboxes were manufactured mainly as single-stage gearboxes, so the diameter of a large gear was often several times greater than the size of the turbine itself. The need to use bulky gear reduction gears prevented the widespread adoption of de Laval turbines. The largest single-stage turbine with a power of 500 hp. had a steam consumption of 6...7 kg/hp h.

An interesting feature of Laval’s work can be considered his “naked empiricism”: he created completely workable designs, the theory of which was later developed by others. Thus, the theory of a flexible shaft was subsequently deeply studied by the Czech scientist A. Stodola, who also systematized the main issues of calculating the strength of turbine disks of equal resistance. It was the lack of a good theory that did not allow de Laval to achieve great success; moreover, he was an enthusiastic person and easily switched from one topic to another. Neglecting the financial side of the matter, this talented experimenter, not having time to implement his next invention, quickly lost interest in it, being carried away by the new idea. A different kind of person was the Englishman Charles Parsons, son of Lord Ross.

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Charles Algernon Parsons

Charles Parsons was born in 1854 and received a classical English education, graduating from Cambridge University. He chose mechanical engineering as his occupation and since 1976 began working at the Armstrong plant in Newcastle. The designer's talent and ingenuity, combined with the financial capabilities of his parents, allowed Parsons to quickly become the head of his own business. Already in 1883 he was a co-owner of the company Clark, Chapman, Parsons and Co., and in 1889 he became the owner of his own turbine and dynamism plant in Guiton.

Parsons built the first multi-stage jet-type steam turbine in 1884. It was not intended to drive relatively low-power separators, but to work in conjunction with an electric generator. Thus, from the very first step, Parsons correctly foresaw one of the most promising areas of application of steam turbines, and in the future he did not have to look for consumers for his invention. In order to balance the axial force, steam was supplied to the middle of the turbine shaft and then flowed to its ends. Parsons' first steam turbine had a power of only 6 hp. and was subjected to various tests. The main difficulties were the development of a rational design of the blades and methods of attaching them to the disk, as well as ensuring seals. Already in a design dating back to 1887, Parsons used labyrinth seals, which made it possible to move to turbines with unidirectional steam flow. By 1889, the number of turbines built exceeded 300 units; their power had not yet reached 100 hp. at a rotation speed of about 5000 rpm. Such turbines were used primarily to drive electric generators.

The relationship between the partners at Clark, Chapman, Parsons and Co. turned out to be far from cloudless, and Parsons was forced to leave, leaving to his former colleagues part of the copyrights that formally belonged to the company. In this regard, he abandoned the creation of active turbines (protected by a patent) for a long time and moved on to the development of radial multistage turbines. By improving this type, the designer was able to achieve impressive results. Thus, he reduced the specific steam consumption from 44 to 12.7 kg/kWh, but at the same time realized that the previous axial type of turbine was still more promising. Beginning in 1894, having restored the rights to the patent, Parsons again began to work on just such turbines.

At his plant, he tried a variety of materials for turbine blades, but settled on bronze for saturated and moderately superheated steam, pure copper for some high pressure and nickel bronze for highly superheated steam. In addition, in-depth research was carried out to create a rational design for the steam supply regulator. To improve accuracy, Parsons used the intermittent relay principle to reduce friction. At the same time, other improvements were introduced, which together led to a decrease in the specific steam consumption to 9.2 kg/kWh for a 400 kW turbine manufactured in 1896.

Thanks to the work of Charles Parsons and his employees, England was ahead of the rest of the planet: while in other countries they were just looking at steam turbines, in the United Kingdom the total power of turbines built in the same 1896 exceeded 40,000 hp. But even on the continent, advanced engineers realized the importance of the new product for energy purposes. In 1899, on the initiative of one of them, Lindley, who held the position of chief engineer of Frankfurt, it was decided to use two Parsons turbines with a power of 1000 kW each at the Elberfeld power station under construction. German pride was hurt. First of all, industrialists who produced powerful steam engines were dissatisfied. However, the test results of turbines, published in 1900, testified to the undeniable advantages of the units used compared to traditional “steam engines”. Soon, one of the best electrical engineering firms of that time, Brown-Boveri in Baden (near Zurich), acquired a license to produce Parsons turbines.

Then offers to purchase licenses began to grow like a snowball: in addition to the Germans, Italians and Americans (in particular, the Westinghouse company) showed interest. If in 1903 the maximum turbine power was 6500 kW, then in 1909 units with a capacity of 10,000 kW appeared, in 1915 - 20,000 kW, and in 1917 - 30,000 kW! Turbines began to be built in Switzerland, France, and Austria-Hungary. The names of the Frenchman O. Rato and the American C. Curtis appeared in the company of the “founding fathers” of turbine construction. But Parsons went down in the history of technology as a star of the first magnitude: after all, in addition to purely “turbine” problems, he also took upon himself (and successfully solved) the task of introducing a new type of engine into the fleet.

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Marine boiler and turbine plants

IN late XIX century, a new class of warships was formed - destroyers (in the West they correspond to the term “distroyer” - destroyer), the main weapons of which were forward-propelled torpedoes with a powerful warhead capable of sending a huge battleship to the bottom. With a small displacement, the only protection for the destroyer was high speed, since no armor could protect it from a fatal end in the event of a direct hit from a large-caliber projectile. Naturally, the size of the destroyer grew, and at the turn of the century its displacement reached 350...500 tons, and the required power of the power plant was 5000...8000 hp. The mass of mechanisms and fuel on board the ship has increased sharply, therefore, in order to maintain the high combat qualities of the destroyer, an urgent need arose for a more powerful engine with better specific characteristics. And such an engine appeared in the form of a ship turbine.

In 1894, Parsons built a small turbine ship, essentially a boat with a displacement of only 44.5 tons, but the power of its power plant reached 2000 hp. On November 27, Turbinia entered testing and... disappointed its creator. Her speed was only 19.7 knots, and the designer expected to get at least 30. The reason was the so-called propeller slip, later called “cavitation.” Due to the excessive rotation speed of the propellers, the speed of water on the suction side of the blades increased so much that the pressure dropped to critical and the water boiled at normal temperature, turning into steam. In such an environment, the propeller slipped, lost its stop, and its efficiency decreased. fell sharply.

During the year, 9 propellers were replaced on the Turbinia, but its speed never reached the planned value. Then Parson radically redesigned the ship, turning its single-shaft installation into a three-shaft one. Each shaft was powered by high, medium and high turbines connected in series. low pressure. The shafts ended with three propellers located one behind the other. At the first exit, the updated Turbinia showed a speed of 32.8 knots. By 1897, after a number of improvements and increasing the power of the boiler-turbine unit (KTU) to 2400 hp, it was able to accelerate to 34.5 knots! "Turbinia" was the fastest ship in the world.

In order to demonstrate the advantages of a ship's turbine, Parsons decided to take an extraordinary step that bordered on hooliganism. By his order, before the start of the naval parade dedicated to the 60th anniversary of Queen Victoria’s accession to the throne, the Turbinia unauthorizedly raced in front of the English fleet, and not a single fastest British destroyer was able to stop the insolent one. The resonance turned out to be very significant - newspapers wrote about the scandalous incident, even the British Admiralty woke up. To begin with, it ordered two “distroers” with a four-shaft KTU with a power of 11,500 hp each, capable of providing the ship with a contract speed of 31.5 knots. The next step was the cruisers “Amethyst” and “Topaz”, completely the same type, with the exception of power plants. With a displacement of 3050 tons, the maximum power of the Amethyst boiler and turbine unit was 13,000 hp, providing it with a speed of 23.6 knots, while the Topaz boiler and turbine unit developed a maximum power of 9,600 hp, and its speed did not exceed 21.8 knots. And, what is very important, for the Amethyst the specific fuel consumption decreased with increasing speed, while for the Topaz it had a minimum at approximately 14 knots.

Based on the test results, the British made a radical decision: all newly built surface ships of the main classes should be equipped with KTU.

Almost simultaneously, the introduction of steam turbines into shipbuilding began. The first two turbine liners were built in England for Canada, and in 1906 the turbine transatlantic Carmania entered the Liverpool-New York line. According to the terms of the contract, for four months it had to sail with the turbine casings sealed, which precluded their opening not only for repairs, but also for inspection. The KTU of the liner withstood such a tough test, and in 1907 two more turbine ships with a displacement of 38 thousand tons each were put into operation: Lusitania and Mauritania. The latter, during a transatlantic voyage, demonstrated an average speed exceeding 26 knots, and subsequently held the Blue Ribbon of the Atlantic, an honorary award for the fastest liner in the ocean, for 22 years.

In 1913, the destroyer Novik was built at the Putilov plant in St. Petersburg, the three-shaft KTU of which had a total power of 42,000 hp. allowed the ship to set a world speed record of 37.3 knots.

At the same time, impressive achievements could not compensate for the low efficiency of the steam turbine at low loads, which significantly reduced its attractiveness as a marine engine. The speed at which turbine ships gained an advantage over ships with steam engines was 16...18 knots. In this regard, Charles Parsons proposed the idea of ​​a turbomachine installation. For slow speed and reverse, a steam engine was used, and at a speed above a certain critical speed it was turned off and steam was supplied to the turbines. The power plant of the infamous Titanic and the similar Olympic were constructed in a different way. On these ships, the side shafts were driven by steam engines, and the middle one was driven by a turbine, which used steam that had already worked in the cylinders of the machines.

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Triumph of steam turbine energy

In the period between the two great wars, turbine power engineering developed primarily in the direction of using high-pressure steam. One of the first such turbines with a power of 1675 kW was built by the Brown-Boveri plant for a Belgian power plant. The steam pressure was taken to be 50 kgf/cm2, and its temperature reached 440...450 °C. The labyrinth seal turned out to be too complex and unreliable, so the designers placed the first stage of the high-pressure turbine suspended, without a bearing.

Soon, the Brown-Boveri plant produced a turbine with a power of 7000 kW at a steam pressure of 160 kgf/cm2 and a temperature of 430 °C for an electrical station in Mannheim. For the turbine built for the power plant in Langerbrugge, the steam parameters were chosen even higher: the temperature was 450 °C and its pressure was 225 kgf/cm2. In the United States, the General Electric company chose not to take risks, limiting the pressure to 84 kgf/cm2, but it began to vigorously increase the power of a single installation. Thus, the turbine built for the Ford enterprise (2-cylinder, 2-axial) had a power of 110 MegaW at a shaft rotation speed of 1800 rpm. In the early thirties, huge power steam turbine plants with a unit capacity of 160 and even 208 MegaW came into operation in the United States.

The Europeans limited themselves to significantly lower unit power values ​​of industrial steam turbines. One of the coolest was considered the installation in Vitkovice, which had two turbines, one with a capacity of 30 MegaW, and the second with a capacity of 18 MegaW. The rotation speed of these units was chosen to be 3000 rpm, which was determined by the AC frequency accepted in Europe (50 Hz). It should be noted that in the United States, steam turbines typically had a rotation speed of 1800 or 3600 rpm due to the “American” alternating current frequency of 60 Hz.

The convenience of “coupling” with an electric generator without the use of any intermediate gears turned out to be an extremely important advantage of the steam turbine. In addition, the turbine easily withstood overloads, practically did not oil the steam (unlike a steam engine), and was easily regulated in terms of rotation speed. Combined with higher efficiency. turbines, especially when heavy loads, all these advantages relatively quickly led to the widespread “decline” of the era of the steam engine in the energy sector and shipbuilding.

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 couple had accumulated a reserve of energy, which finally manifested 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 at the end of the 19th and beginning of the 20th centuries. the achievable power and speed of the steam engine had already become insufficient.

There was a need for the construction of large power plants, which required a powerful and high-speed engine. 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). A tube is inserted into the upper part of the boiler (Fig. 2).

Since the steam pressure inside the boiler is greater than the atmospheric pressure of the 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 to obtain mechanical motion using 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 were of extremely great importance for the 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 a 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 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 that 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 continued. 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 efficiency turbines 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.

Steam application 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 combined heat and power generation.

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 speed equal to the number propeller revolutions, 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.

- this is a heat engine, thermal energy steam in which is converted into mechanical work. Together with hydraulic turbines great importance For the development of world energy, steam turbines were invented and widely used, which are the main engine of thermal power plants (CHP) and nuclear power plants (NPP). The principle of operation of steam turbines is similar to hydraulic ones, the only difference is that in the first case the turbine was driven by a jet of heated steam, in the second by a jet of water. The steam turbine turned out to be simpler, more economical and more convenient than Watt's steam engine. Inventors have long tried to create a machine (steam turbine), where a jet of steam would directly rotate the impeller. At the same time, the rotation speed of the wheel must be very high due to the high speed of the steam jet.

In 1883, Laval managed to create the first steam engine, which was a light wheel with blades. Through nozzles placed at an angle, steam was directed onto the blades, which pressed on them and spun the wheel. In 1889 Laval improved the design, using a nozzle that expanded at the outlet. Due to this, the steam speed and, accordingly, the rotor rotation speed increased. The resulting jet was directed onto one row of blades, which were mounted on a disk. Steam pressure and the number of nozzles determined the power of the turbine operating according to active principle. If the exhaust steam did not enter the air, but was sent to a condenser, where it was liquefied at reduced pressure, then the turbine power would be at its highest. The Laval turbine received universal recognition; it provided great benefits when combined with machines having high speed(separators, saws, centrifugal pumps). It was also used as a drive for an electric generator, although only through a gearbox (due to its high speed).

In 1884, the English inventor Parsons patented a multi-stage jet turbine, specially created by him to drive action of an electric generator. At a lower rotation speed, the energy of the steam was used to the maximum due to the fact that the steam, passing through 15 stages, expanded gradually. Each stage had a pair of blade crowns. One crown with guide blades, which were attached to the turbine housing, was stationary. The second is movable with working blades on a disk, which was mounted on a rotating shaft. The blades of the crowns (fixed and movable) are oriented in opposite directions. This was the first steam turbine to be successfully used in industry.

In 1889, 300 turbines were already used to generate electricity; in 1899, the first power plant with Parsons turbines appeared. In 1894, the first steamship, the Turbinia, was launched, powered by a steam turbine. Soon, steam turbines began to be installed on high-speed ships. The French scientist Rato derived a comprehensive theory of turbomachines based on existing experience. Over time, the Parsons turbine gave way to compact active-reaction turbines. Although today steam turbines have largely retained the features of the Parsons turbine.