"Turbo-supercharging", "turbo-jet", "turboprop", - these terms are firmly included in the lexicon of engineers of the XX century engaged in the design and maintenance of vehicles and stationary electrical installations. They are used even in related areas and advertising, when they want to give the name of the product some hint of special power and efficiency. In aviation, missiles, ships and power plants, a gas turbine is most often used. How is it arranged? Does it work on natural gas (as one might think from the name), and what kind of gas are they at all? How does the turbine differ from other types of internal combustion engine? What are its advantages and disadvantages? An attempt to answer these questions as fully as possible is undertaken in this article.
Russian machine-building leader
Russia, unlike many other independent states formed after the collapse of the USSR, managed to save the machine-building industry to a considerable extent. In particular, the company "Saturn" is engaged in the production of power plants for special purposes. Gas turbines of this company are used in shipbuilding, raw materials and energy. The products are high-tech, it requires a special approach for installation, debugging and operation, as well as special knowledge and expensive equipment for routine maintenance. All these services are available to customers of the company "ODK - Gas Turbines", so today it is called. There are not many such enterprises in the world, although the principle of the device of the main product is at first glance uncomplicated. The accumulated experience is of great importance, allowing to take into account many technological subtleties, without which it is impossible to achieve long-term and reliable operation of the unit. Here is just a part of the range of products of the UDK: gas turbines, power plants, gas pumping units. Among the customers are Rosatom, Gazprom and other whales of the chemical industry and energy.
The manufacture of such complex machines requires in each case an individual approach. The calculation of the gas turbine is now fully automated, but materials and features of the wiring diagrams in each individual case matter.
And it all began so simply ...
Searches and pairs
The first experiments of transforming the translational energy of the flow into a rotational force were carried out by mankind in ancient times, using a conventional water wheel. Everything is extremely simple, the liquid flows from top to bottom, blades are placed in its stream. The wheel, equipped with them around the perimeter, is spinning. The windmill also works. Then came the age of steam, and the rotation of the wheel accelerated. By the way, the so-called "eolipil", invented by the ancient Greek Geron about 130 years before Christ, was a steam engine, working precisely on this principle. In fact, it was the first gas turbine known to historical science (after all, steam is the gaseous aggregate state of water). Today it is still common to separate these two concepts. To the invention of Heron, Alexandria was then treated with little enthusiasm, albeit with curiosity. Industrial equipment of the turbine type appeared only at the end of the XIX century, after the creation by Swede Gustaf Laval of the world's first active power unit equipped with a nozzle. Approximately in the same direction worked as an engineer Parsons, equipping his car with several functionally connected steps.
The birth of gas turbines
A century ago, a certain brilliant thought occurred to a certain John Barber. Why is it necessary to heat steam first, is it not easier to use directly the exhaust gas produced by the combustion of fuel, and thus eliminate unnecessary mediation in the process of energy conversion? So the first real gas turbine turned out. The patent of 1791 sets out the basic idea of use in a horseless cart, but its elements are now used in modern missile, aviation tank and automobile engines. The beginning of the process of jet propulsion was given in 1930 by Frank Whittle. He came up with the idea of using a turbine to propel an airplane. In the future, it found development in numerous turboprop and turbojet projects.
Nikola Tesla gas turbine
The famous scientist-inventor always approached the questions studied non-standard. For all, it seemed obvious that the wheels with blades or blades "catch" the motion of the environment better than flat objects. Tesla, in his characteristic manner, proved that if we assemble the rotor system from the disks, arrange them on the axis in succession, then by catching the boundary layers with the gas flow, it will rotate no worse, and in some cases even better than the multi-bladed propeller. True, the direction of the mobile environment must be tangential, which in modern units is not always possible or desirable, but the design is much simpler - it does not need blades at all. Gas turbine in the Tesla scheme is not yet being built, but perhaps the idea is only waiting for its time.
Now about the fundamental arrangement of the machine. It is a set of rotating system, mounted on the axis (rotor) and fixed part (stator). On the shaft there is a disk with working blades forming a concentric lattice, they are acted upon by gas supplied under pressure through special nozzles. Then the expanded gas enters the impeller, also equipped with blades, called working. For the intake of the air-fuel mixture and exhaust (exhaust), there are special nozzles. The compressor also participates in the general scheme. It can be made according to a different principle, depending on the required working pressure. For its operation, a part of the energy, which goes to compress the air, is taken from the axis. The gas turbine works by the combustion process of an air-fuel mixture, accompanied by a significant increase in volume. The shaft rotates, its energy can be used useful. Such a scheme is called single-loop, if it repeats, then it is considered to be multi-stage.
Advantages of aviation turbines
There are gas turbine engines and disadvantages
The gas turbine, during operation, heats up, and transfers heat to the surrounding elements of the structure. This is especially critical again in aviation, when using a redesigned layout scheme that involves the jetting of the lower part of the tail unit with a jet stream. And the motor housing itself requires special thermal insulation and the use of special refractory materials that withstand high temperatures.
Cooling gas turbines is a complicated technical task. It's no joke, they work in the regime of a virtually permanent explosion occurring in the case. Efficiency in some modes is lower than for carburetor motors, however, when using a two-circuit scheme this defect is eliminated, although the design becomes more complicated, as in the case of the inclusion of "dozhima" in the compressor circuit. Overclocking turbines and accessing the operating mode requires some time. The more often the engine starts and stops, the faster it wears out.
Well, without faults, no system is not complete. It is important to find such an application of each of them, in which its dignity will be more clearly manifested. For example, tanks, such as the American "Abrams", based on a power plant - a gas turbine. It can be filled with everything that burns, from high-octane gasoline to whiskey, and it gives out a lot of power. The example may not be very successful, as the experience in Iraq and Afghanistan has shown the vulnerability of the compressor blades to the impact of sand. Repair of gas turbines has to be done in the USA, at the factory. Take the tank there, then back, and the cost of the service itself plus accessories ...
Helicopters, Russian, American and other countries, as well as powerful high-speed boats suffer less from blockages. Liquid rockets can not do without them.
Modern warships and civil vessels also have gas turbine engines. And energy.
Three-generator power stations
The problems faced by aircraft builders are not so worried about those who manufacture industrial equipment for the production of electricity. Weight in this case is not so important, and you can focus on such parameters as efficiency and overall efficiency. Generator gas turbine units have a massive frame, a reliable frame and thicker blades. The generated heat can be disposed of for a variety of needs, from secondary recycling in the system itself to heating of domestic facilities and thermal supply of refrigeration-type refrigeration units. This approach is called trigenerative, and the efficiency in this mode approaches 90%.
Nuclear power installations
For a gas turbine it does not matter what the source of the heated medium is, giving its energy to its blades. It can be a burned air-fuel mixture, and simply superheated steam (not necessarily a water vapor), the main thing is that it ensures its uninterrupted power supply. At their core, the power plants of all nuclear power plants, submarines, aircraft carriers, icebreakers and some military surface ships (the Peter the Great missile cruiser, for example) are based on a gas turbine (GTU), rotated by steam. Issues of safety and ecology dictate a closed cycle of the first circuit. This means that the primary thermal agent (in the first samples, this role was performed by lead, now it was replaced with paraffin), does not leave the pri-reactor zone, flowing heat-generating elements in a circle. The heating of the working substance takes place in subsequent circuits, and the evaporated carbon dioxide, helium or nitrogen rotates the turbine wheel.
Complex and large installations are almost always unique, their production is carried out in small series or in general single specimens are manufactured. More often, aggregates produced in large quantities find application in peaceful sectors of the economy, for example, for pumping hydrocarbon raw materials through pipelines. It is these that are produced by the company ODC under the brand name "Saturn". Gas turbines of pumping stations fully correspond to their designation. They really pump natural gas, using for its work its own energy.