“Turbocharging”, “turbojet”, “turboprop” - these terms are firmly included in the lexicon of the engineers of the XX century, engaged in the design and maintenance of vehicles and fixed electrical installations. They are even used in related fields and advertising, when they want to give the product name some hint of special power and efficiency. In aviation, rockets, ships and power plants, gas turbines are most commonly used. How is it arranged? Does it work on natural gas (as the name suggests), and what kind of gas are they? What makes a turbine different from other types of internal combustion engines? What are its advantages and disadvantages? An attempt to answer these questions as fully as possible is made in this article.
Russian Engineering Leader
Russia, unlike many other independent states that were formed after the collapse of the USSR, managed to largely maintain the engineering industry. In particular, the company "Saturn" is engaged in the production of special purpose power plants. Gas turbines of this company are used in shipbuilding, raw materials and energy. The products are high-tech, it requires a special approach during installation, debugging and operation, as well as special knowledge and costly equipment for scheduled maintenance. All these services are available to customers of the company "ODK - Gas Turbines", so today it is called. There are not so many such enterprises in the world, although at first glance the principle of organizing the main products is simple. The accumulated experience is of great importance, which allows to take into account many technological details, without which it is impossible to achieve durable and reliable operation of the unit. Here are just a part of the UEC product range: gas turbines, power plants, gas transfer units. Among the customers are Rosatom, Gazprom and other “whales” of the chemical industry and power industry.
The manufacture of such complex machines requires in each case an individual approach. The calculation of the gas turbine is currently fully automated, but the materials and features of the wiring diagrams in each individual case matter.
It all began so simply ...
Searches and couples
The first experiments of transforming the translational energy of a stream into a rotational force were carried out by mankind in ancient times, using a conventional water wheel. Everything is very simple, the liquid flows from the top down, the blades are placed in its flow. The wheel, equipped with them around the perimeter, is spinning. The windmill works the same way. 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 Heron about 130 years before Christ, was a steam engine operating according to this principle. In essence, it was the first gas turbine known to historical science (after all, steam is a gaseous aggregate state of water). Today, it is still customary to separate these two concepts. The invention of Heron then in Alexandria reacted without much enthusiasm, albeit with curiosity. Turbine-type industrial equipment appeared only at the end of the 19th century, after the creation of the Swede by Gustaf Laval, the world's first active power unit equipped with a nozzle. Approximately in the same direction, engineer Parsons worked, supplying his car with several functionally connected steps.
The birth of gas turbines
A century earlier, a certain brilliant idea occurred to a certain John Barber. Why do we need to heat the steam first, is it not easier to use the exhaust gas generated during the combustion of the fuel directly and thereby eliminate unnecessary intermediation in the process of energy conversion? So the first real gas turbine turned out. The patent of 1791 sets forth the basic idea of using it in a horseless carriage, but its elements are now used in modern rocket, aircraft tank and car engines. The beginning of the process of jet engine building was given in 1930 by Frank Whittle. He got the idea to use a turbine to propel the plane. Later, it was developed in numerous turboprop and turbojet projects.
Nikola Tesla gas turbine
The famous scientist-inventor always approached the issues under study outside the box. It seemed obvious to everyone that the wheels with blades or blades “catch” the movement of the medium better than flat objects. Tesla, in his usual manner, proved that if the rotor system is assembled from disks, arranged on an axis in series, then due to catching the boundary layers with a gas flow, it will rotate no worse and in some cases even better than a multi-blade propeller. True, the orientation of the mobile environment must be tangential, which is not always possible or desirable in modern units, but the design is significantly simplified — it does not need blades at all. A gas turbine according to the Tesla scheme has not yet been built, but perhaps the idea is just waiting for its time.
Now about the basic device of the machine. It is a set of rotating system, mounted on the axis (rotor) and the fixed part (stator). A disk with working blades forming a concentric grid is placed on the shaft; they are affected by gas supplied under pressure through special nozzles. Then the expanded gas enters the impeller, also equipped with paddles, called workers. For the intake of air-fuel mixture and exhaust (exhaust) are special connections. Also in the general scheme involved a compressor. It can be performed according to a different principle, depending on the required working pressure. For his work from the axis of the energy is taken, going to compress air. The gas turbine operates due to the combustion process of the air-fuel mixture, accompanied by a significant increase in volume. The shaft rotates, its energy can be used useful. This scheme is called single-circuit, but if it repeats, then it is considered multi-stage.
The merits of aviation turbines
Gas turbine engines have disadvantages
The gas turbine heats up during operation and transfers heat to the surrounding construction elements. This is especially critical, again, in aviation, when using a redrawn layout involving the jet washing of the lower part of the tail assembly. And the engine case itself requires special thermal insulation and the use of special refractory materials that can withstand high temperatures.
Cooling gas turbines is a complex technical challenge. It’s no joke, they are working in the mode of a virtually permanent explosion occurring in the hull. Efficiency in some modes is lower than that of carburetor engines, however, when using a dual-circuit scheme, this disadvantage is eliminated, although the design is complicated, as in the case of including “boosting” compressors in the circuit. Turbine acceleration and operating mode take some time. The more often the unit starts and stops, the faster it wears out.
Well, no system is without flaws. It is important to find such an application for each of them, in which its merits will more clearly manifest. For example, tanks, such as the American "Abrams", the basis of the power plant which - a gas turbine. It can be refueled with everything that burns, from high-octane gasoline to whiskey, and it delivers more power. The example may not be very successful, since experience in Iraq and Afghanistan has shown the vulnerability of compressor blades to sand. Repair of gas turbines has to be made in the United States, at the factory. Take the tank there, then back, and the cost of the service itself, plus components ...
Helicopters, Russian, American and other countries, as well as powerful speedboats, are less affected by blockages. In liquid rockets can not do without them.
Modern warships and civilian ships also have gas turbine engines. And also energy.
Trigenerator power plants
The problems faced by aircraft manufacturers, not so worried about those who produce industrial equipment for the production of electricity. Weight in this case is not so important, and you can focus on parameters such as efficiency and overall efficiency. Generator gas turbine units have a massive frame, reliable bed and thicker blades. It is quite possible to dispose of the heat produced, using for a variety of needs, from secondary recycling in the system itself to heating of residential premises and thermal power supply of absorption-type refrigeration units. This approach is called trigenerator, and the efficiency in this mode approaches 90%.
Nuclear power plants
For a gas turbine, there is no fundamental difference what the source of the heated medium gives its energy to its blades. This may be a burnt air-fuel mixture, or simply superheated steam (not necessarily water), as long as it provides uninterrupted power. 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 steam turbine (GTU). Safety and environmental issues dictate the closed loop of the primary 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 near-reactor zone, flowing around the fuel elements in a circle. The working medium is heated in subsequent circuits, and the vaporized carbon dioxide, helium, or nitrogen rotates the turbine wheel.
Complex and large installations are almost always unique, their production is carried out in small batches or single copies are made at all. Most often, units produced in large quantities are used in peaceful sectors of the economy, for example, for pumping hydrocarbons through pipelines. These are the ones manufactured by ODK under the brand name "Saturn". Gas turbines of pumping stations fully correspond to their name. They really pump natural gas, using his own energy for their work.