Power units - drives of electric generators for autonomous small thermal power plants can be diesel, gas piston, microturbine and gas turbine engines.
A large number of discussion and polemical articles have been written about the advantages of certain generating plants and technologies. As a rule, in disputes in the pen, either one or the other often remains in disgrace. Let's try to figure out why.
The determining criteria for choosing power units for the construction of autonomous power plants are the issues of fuel consumption, the level of operating costs, as well as the payback period for power plant equipment.
Ease of operation, level of maintenance and repair, and where to repair the power units are important factors in choosing power units. These issues are primarily related to the costs and problems that the owner of an autonomous power plant may subsequently have.
In this article, the author does not have a selfish goal to prioritize piston or turbine technologies. The types of power plants of power plants are more correct, it is best to select directly for the project, based on the individual conditions and technical specifications of the customer.
When choosing power equipment for the construction of an autonomous gas-fired CHP plant, it is advisable to consult with independent specialists from engineering companies that are already building turnkey power plants. An engineering company must have completed projects that can be viewed and visited with a tour. One should also take into account such a factor as the weakness and underdevelopment of the generating equipment market in Russia, where real sales volumes, in comparison with developed countries, are small and leave much to be desired - this, first of all, is reflected in the volume and quality of offers.
Gas piston units vs. gas turbine engines - operating costs
Is it true that the operating costs of a mini-CHP with reciprocating machines are lower than the operating costs of a power plant with gas turbines?
The cost of a major overhaul of a gas piston engine can be 30–350% of the initial cost of the power unit itself, and not of the entire power plant - during the overhaul, the piston group is replaced. Gas reciprocating units can be repaired on site without complex diagnostic equipment once every 7-8 years.
The cost of repairing a gas turbine plant is 30–50% of the initial investment. As you can see, the costs are about the same. Real, honest prices for gas turbine and piston units of comparable power and quality are also similar.
Capital repairs of the gas turbine plant due to its complexity are not carried out on site. The supplier must take away the spent unit and bring a replacement gas turbine unit. The old unit can only be restored to factory conditions.
You should always take into account compliance with the maintenance schedule, the nature of the loads and the operating modes of the power plant, regardless of the type of installed power units.
The question, which is often exaggerated, about the finickyness of the turbine to operating conditions, is associated with outdated information from forty years ago. Then "on the ground", in the drive of power plants, aircraft turbines "removed from the wing" of the aircraft were used. Such turbines with minimal changes adapted to work as the main power units for power plants.
Today, modern autonomous power plants use turbines of industrial, industrial design, designed for continuous operation with various loads.
The lower limit of the minimum electrical load, officially declared by manufacturers for industrial turbines, is 3–5%, but in this mode, fuel consumption increases by 40%. The maximum load of a gas turbine plant, in limited time intervals, can reach 110-120%.
Modern gas-piston installations have phenomenal efficiency, based on a high level of electrical efficiency. The “problems” associated with the operation of gas piston units at low loads are resolved positively even at the design stage. Design must be of high quality.
Compliance with the operating mode recommended by the manufacturer will extend the life of engine parts, thus saving money to the owner of an autonomous power plant. Sometimes, in order to bring the gas-piston machines to the nominal mode at partial loads, one or two electric boilers are included in the project of the thermal scheme of the station, which make it possible to provide the desired 50% load.
For power plants based on gas piston units and gas turbines, it is important to comply with the N + 1 rule - the number of operating units plus one more for the reserve. “N + 1” is a convenient, rational number of installations for the operating personnel. This is due to the fact that for power plants of any types and types it is necessary to carry out routine and repair work.
A company connected to the network can install only one unit and use its own electricity at cost, and during maintenance, be powered by the public electricity network, paying according to the meter. This is cheaper than "+1", but, unfortunately, is not always feasible. This is due, as a rule, to the lack of an electrical network in general, or to the incredible high cost of technical conditions for the connection itself.
Unscrupulous dealers of gas piston units and gas turbines, before selling the equipment to the buyer, as a rule, provide only prospectuses - commercial literature of a general plan and very rarely - accurate information about the full operating costs and technical regulations produced.
On powerful gas piston units, the oil does not need to be changed. With constant work, it is simply produced, not having time to age. Oil on such installations is constantly topped up. Such operating modes are provided for by a special design of powerful gas piston engines and are recommended by the manufacturer.
Engine oil waste is 0.25-0.45 grams per kilowatt produced per hour. Loss is always higher when the load is reduced. As a rule, a gas piston engine kit includes a special reservoir for continuous oil topping up, and a mini-laboratory for checking its quality and determining the replacement period.
Accordingly, oil filters or cartridges in them must also be replaced.
Since engine oil still burns out, piston units have a slightly higher level of harmful emissions into the atmosphere than gas turbine units. But since the gas burns completely and is one of the cleanest types of fuel, then talking about serious atmospheric pollution is just “stupid checkers”. A couple of old Hungarian Ikarus buses cause much more serious harm to the environment. To meet environmental requirements, when using reciprocating machines, it is necessary to build higher chimneys, taking into account the already existing MPC level in the environment.
Waste oil from gas piston units cannot simply be dumped on the ground - it requires disposal - this is an "expense" for the owners of the power plant. But you can earn money on this - specialized organizations buy used motor oil.
Many of us use engine oil in our piston engines. If the engine is serviceable, properly operated and refueled with normal fuel, then no financial cataclysms associated with its consumption occur.
The same is true for reciprocating power plants: - there is no need to be afraid of engine oil consumption, it will not ruin you, during the normal operation of modern high-quality gas piston installations, the costs for this article are only 2-3 (!) kopecks per 1 kW of generated electricity.
In modern gas turbine installations, oil is used only in the gearbox. Its volume can be considered insignificant. The replacement of gear oil in gas turbines is carried out on average once every 3-5 years, and its topping up is not required.
To carry out the service in full, a beam crane must be included in the set of a powerful gas piston installation. With the help of a beam crane, heavy parts of piston engines are removed. The use of a beam crane requires high ceilings in the machine rooms of the reciprocating power plant. For the repair of gas-piston installations of small and medium power, simpler lifting mechanisms can be dispensed with.
Gas piston power plants upon delivery can be equipped with various repair tools and devices. Its presence implies that even all critical operations can be carried out by qualified personnel on site. Virtually all repair work on gas turbines can be carried out either at the manufacturing plant or with the direct assistance of factory specialists.
Once every 3-4 months, the spark plugs need to be replaced. Replacing candles is only 1-2 (!) kopecks in the cost of 1 kW / h of own electricity.
Piston units, in contrast to gas turbine units, are liquid-cooled, respectively, the personnel of an autonomous power plant must constantly monitor the level of the coolant and carry out periodic replacement, and if it is water, then it is necessary to carry out its chemical preparation.
The above features of the operation of reciprocating units are absent in gas turbine plants. Gas turbine plants do not use such consumables and components as:
- engine oil,
- spark plug,
- oil filters,
- coolant,
- sets of high voltage wires.
But gas turbines cannot be repaired on site, and much higher gas consumption cannot be compared with the costs of operation and consumables for reciprocating units.
What to choose? Gas piston or gas turbine installations?
How do the power of power units of power plants and the ambient temperature correlate?
With a significant increase in ambient temperature, the power of the gas turbine installation decreases. But with a decrease in temperature, the electric power of a gas turbine, on the contrary, increases. Electrical power parameters, according to existing ISO standards, are measured at t +15 °C.
Sometimes an important point is the fact that a gas turbine plant is capable of delivering 1.5 times more free thermal energy than a piston unit of similar power. When using a powerful (from 50 MW) autonomous CHP in public utilities, for example, this can be of decisive importance when choosing the type of power units, especially with a large and uniform consumption of thermal energy.
On the contrary, where heat is not required in large quantities, but an emphasis is needed on the production of electrical energy, it will be more economically feasible to use gas piston plants.
The high temperature at the outlet of gas turbine plants makes it possible to use a steam turbine as part of a power plant. This equipment is in demand if the consumer needs to receive the maximum amount of electrical energy with the same volume of gas fuel spent, and thus achieve high electrical efficiency - up to 59%. An energy complex of this configuration is more difficult to operate and costs 30-40% more than usual.
Power plants with steam turbines in their structure, as a rule, are designed for a fairly large power - from 50 MW and above.
Let's talk about the most important thing: gas piston units versus gas turbine power units - efficiency
The efficiency of the power plant is more than relevant - because it affects fuel consumption. The average specific consumption of gas fuel per 1 generated kWh is much less for a gas-piston plant, and for any load mode (although long-term loads of less than 25% are contraindicated for piston engines).
The electrical efficiency of reciprocating machines is 40–44%, and that of gas turbines is 23–33% (in a steam-gas cycle, a turbine is capable of delivering an efficiency of up to 59%).
The steam-gas cycle is used at high power plants - from 50-70 MW.
If you need to manufacture a locomotive, an aircraft or a sea vessel, then one of the determining indicators is the efficiency factor (COP) of the power plant. The heat that is obtained during the operation of the engine of a locomotive, aircraft (or vessel) is not used and is released into the atmosphere.
But we are building not a locomotive, but a power plant, and when choosing the type of power units for an autonomous power plant, the approach is somewhat different - here it is necessary to talk about the completeness of the use of combustible fuel - the fuel utilization factor (FU).
Burning, the fuel does the main work - it rotates the generator of the power plant. The rest of the fuel combustion energy is heat that can and should be used. In this case, the so-called "overall efficiency", or rather, the fuel utilization factor (FUE) of the power plant will be about 80-90%.
If the consumer expects to use the thermal energy of an autonomous power plant in full, which is usually unlikely, then the coefficient of performance (COP) of an autonomous power plant is of no practical importance.
When the load is reduced to 50%, the electrical efficiency of the gas turbine decreases.
In addition, turbines require high gas inlet pressure, and for this, compressors (piston) are necessarily installed, and they also increase fuel consumption.
Comparison of gas turbine plants and gas piston engines as part of a mini-CHP shows that the installation of gas turbines is expedient at facilities that have uniform electrical and thermal needs at a power of more than 30-40 MW.
From the foregoing, it follows that the electrical efficiency of power units of various types has a direct projection on fuel consumption.
Gas piston units consume a quarter or even a third less fuel than gas turbine units - this is the main cost item!
Accordingly, with a similar or equal cost of the equipment itself, cheaper electrical energy is obtained from gas piston plants. Gas is the main expense item in the operation of an autonomous power plant!
Gas piston units vs. gas turbine engines - inlet gas pressure
Is it always necessary to have a high pressure gas pipeline when using gas turbines?
For all types of modern power units of power plants, the pressure of the supplied gas is of no practical importance, since a gas compressor is always included in the set of a gas turbine plant, which is included in the cost of the energy complex.
The compressor provides the required pressure performance of the gaseous fuel. Modern compressors are extremely reliable and low maintenance units. In the world of modern technologies, both for gas piston engines and gas turbines, it is only important to have the proper amount of gas fuel to ensure the normal operation of an autonomous power plant.
However, one should not forget that the booster compressor also requires considerable energy, consumables and maintenance. Paradoxically, reciprocating compressors are often used for powerful turbines.
Gas piston engines vs. gas turbine units - dual-fuel installations
It is often written and said that dual-fuel installations can only be piston. Is it true?
This is not true. All well-known manufacturers of gas turbines have dual-fuel units in their range. The main feature of the dual-fuel installation is its ability to work on both natural gas and diesel fuel. Due to the use of two types of fuel in a dual-fuel plant, a number of its advantages can be noted compared to mono-fuel plants:
- in the absence of natural gas, the unit automatically switches to diesel fuel;
- during transients, the unit automatically switches to diesel operation.
When entering the operating mode, the reverse process of switching to operation on natural gas and diesel fuel is carried out;
Do not forget about the fact that the first turbines were originally designed to operate on liquid fuel - kerosene.
Dual-fuel installations are still of limited use and are not needed for most autonomous CHP plants - there are simpler engineering solutions for this.
Gas piston units vs. gas turbine units - number of starts
What can be the number of starts of gas piston units?
Number of starts: a gas piston engine can start and stop an unlimited number of times, and this does not affect its engine life. But frequent starts-stops of gas-piston units, with loss of auxiliary power, can lead to wear of the most loaded units (turbocharger bearings, valves, etc.).
Due to the sharp changes in thermal stresses that occur in the most critical components and parts of the gas turbine hot duct during quick starts of the unit from a cold state, it is preferable to use a gas turbine plant for constant, continuous operation.
Gas piston engines of power plants against gas turbine plants - a resource before overhaul
What can be the resource of the installation before the overhaul?
The resource before overhaul is 40,000–60,000 working hours for a gas turbine. With proper operation and timely maintenance of a gas piston engine, this figure is also equal to 40,000–60,000 operating hours. However, there are other situations when overhaul occurs much earlier.
Gas piston units vs. gas turbine engines - capital investments and prices
What capital investments (investments) will be required in the construction of the power plant? What is the cost of building an autonomous power complex on a turnkey basis?
Calculations show that investments (dollar/kWh) in the construction of a thermal power plant with gas piston engines are approximately equal to gas turbine plants. The Finnish thermal power plant WARTSILA with a capacity of 9 MW will cost the customer approximately 14 million euros. A similar gas turbine thermal power plant based on first-class units will cost $15.3 million.
Gas piston engines against gas turbine plants - ecology
How are environmental requirements met?
It should be noted that gas piston units are inferior to gas turbine units in terms of NO x emissions. Since engine oil burns out, piston units have a slightly higher level of harmful emissions into the atmosphere than gas turbine units.
But this is not critical: the SES asks for the background level according to the MPC at the location of the mini-CHP. After that, the dispersion is calculated so that the “additive” of harmful substances from the mini-CHP added to the background does not lead to exceeding the MPC. Through several iterations, the minimum height of the chimney is selected, at which the requirements of SanPiN are met. The addition from the plant of 16 MW in terms of NO x emissions is not so significant: at a chimney height of 30 m - 0.2 MPC, at 50 m - 0.1 MPC.
The level of harmful emissions from most modern gas turbine plants does not exceed 20-30 ppm, and in some projects this may have a certain value.
Piston installations during operation have vibrations and low-frequency noise. Bringing noise to standard values is possible, appropriate engineering solutions are simply needed. In addition to the dispersion calculation, when developing the “Environmental Protection” section of the project documentation, an acoustic calculation is made and it is checked whether the selected design solutions and the materials used meet the requirements of SanPiN in terms of noise.
Any equipment emits noise in a certain frequency spectrum. Gas turbine installations this bowl has not passed.
Gas piston units vs. gas turbine engines - conclusions
With linear loads and compliance with the N + 1 rule, the use of gas piston engines as the main source of power supply is possible. As part of such a power plant, backup units and tanks are needed to store the second type of fuel - diesel.
In the power range up to 40-50 MW, the use of reciprocating motors at mini-CHPs is considered absolutely justified.
In the case of using gas piston units, the consumer can completely get away from external power supply, but only with a deliberate and balanced approach.
Piston installations can also be used as backup or emergency sources of electricity.
A certain alternative to piston installations is gas microturbines. True, the prices for microturbines “bite” a lot and amount to ~ $ 2500-4000 per 1 kW of installed power!
A comparison of gas turbine plants and gas piston engines as part of a mini-CHP shows that the installation of gas turbines is possible at any facilities that have electrical loads of more than 14-15 MW, but due to the high gas consumption, turbines are recommended for power plants of much larger capacity - 50-70 MW.
For many modern generating plants, 200,000 hours of operation is not a critical value, and subject to the scheduled maintenance schedule and the phased replacement of turbine parts subject to wear: bearings, injectors, various auxiliary equipment (pumps, fans), further operation of the gas turbine plant remains economically feasible. High-quality gas piston units today also successfully overcome 200,000 hours of operation.
This is confirmed by the modern practice of operating gas turbine / gas piston units around the world.
When choosing the power units of an autonomous power plant, expert advice is needed!
Expert advice and supervision are also necessary in the construction of autonomous power plants. To solve the problem, we need an engineering company with experience and completed projects.
Engineering allows you to competently, unbiasedly and objectively determine the choice of the main and auxiliary equipment for the selection of the optimal configuration - the configuration of your future power plant.
Qualified engineering allows you to save significant money for the customer, and this is 10-40% of the total cost. Engineering from professionals in the power industry avoids costly mistakes in the design and selection of equipment suppliers.
Every now and then in the news they say that, for example, at such and such a state district power station, the construction of a CCGT unit of 400 MW is in full swing, and at another CHPP-2, a GTP installation of so many MW is put into operation. Such events are written about, they are covered, since the inclusion of such powerful and efficient units is not only a “tick” in the implementation of the state program, but also a real increase in the efficiency of power plants, the regional energy system and even the unified energy system.
But I would like to bring to your attention not about the implementation of state programs or forecast indicators, but about CCGT and GTU. In these two terms, not only the layman, but also the novice power engineer can get confused.
Let's start with the easier one.
GTU - gas turbine plant - is a gas turbine and an electric generator combined in one building. It is advantageous to install it at a thermal power plant. This is effective, and many CHP reconstructions are aimed at installing just such turbines.
Here is a simplified cycle of operation of a thermal plant:
Gas (fuel) enters the boiler, where it burns and transfers heat to water, which leaves the boiler in the form of steam and turns the steam turbine. The steam turbine turns the generator. We get electricity from the generator, and we take steam for industrial needs (heating, heating) from the turbine if necessary.
And in a gas turbine plant, the gas burns out and turns the gas turbine, which generates electricity, and the outgoing gases turn water into steam in the waste heat boiler, i.e. gas works with a double benefit: first it burns and turns the turbine, then it heats the water in the boiler.
And if the gas turbine plant itself is shown in even more detail, it will look like this:
This video clearly shows what processes take place in a gas turbine plant.
But it will be even more useful if the resulting steam is made to work - put it into a steam turbine so that another generator works! Then our GTU will become a STEAM-GAS UNIT (CCGT).
As a result, PSU is a broader concept. This plant is an independent power unit where fuel is used once and electricity is generated twice: in a gas turbine plant and in a steam turbine. This cycle is very efficient, and has an efficiency of about 57%! This is a very good result, which allows you to significantly reduce fuel consumption for obtaining a kilowatt-hour of electricity!
In Belarus, to increase the efficiency of power plants, gas turbines are used as a “superstructure” to the existing CHP scheme, and CCGTs are being built at state district power plants as independent power units. Working at power plants, these gas turbines not only increase the "forecast technical and economic indicators", but also improve the management of generation, as they have high maneuverability: speed of start-up and power gain.
That's how useful these gas turbines are!
The article describes how the efficiency of the simplest gas turbine is calculated, tables of different gas turbines and combined cycle plants are given to compare their efficiency and other characteristics.
In the field of industrial use of gas turbine and steam-gas technologies, Russia has lagged far behind the advanced countries of the world.
World leaders in the production of high-capacity gas and combined-cycle power plants: GE, Siemens Wistinghouse, ABB - achieved values of unit power of gas turbine plants of 280-320 MW and an efficiency of over 40%, with a utilizing steam-power superstructure in a combined-cycle cycle (also called binary) - capacities of 430- 480 MW with efficiency up to 60%. If you have questions about the reliability of CCGT - then read the article.
These impressive figures serve as benchmarks in determining the development paths for the power engineering industry in Russia.
How is the efficiency of a gas turbine determined?
Here are a couple of simple formulas to show what the efficiency of a gas turbine plant is:
Turbine internal power:
- Nt = Gex * Lt, where Lt is the operation of the turbine, Gex is the flow rate of exhaust gases;
GTU internal power:
- Ni gtu \u003d Nt - Nk, where Nk is the internal power of the air compressor;
GTU effective power:
- Nef \u003d Ni gtu * Efficiency mech, efficiency mech - efficiency associated with mechanical losses in bearings, can be taken 0.99
Electric power:
- Nel \u003d Ne * efficiency eg, where efficiency eg is the efficiency associated with losses in the electric generator, we can take 0.985
Available heat of fuel:
- Qsp = Gtop * Qrn, where Gref - fuel consumption, Qrn - the lowest working calorific value of the fuel
Absolute electrical efficiency of a gas turbine plant:
- Efficiency \u003d Nel / Q dist
CCGT efficiency is higher than GTU efficiency since the combined-cycle plant uses the heat of the exhaust gases of the gas turbine. A waste heat boiler is installed behind the gas turbine, in which the heat from the exhaust gases of the gas turbine is transferred to the working fluid (feed water), the generated steam is sent to the steam turbine to generate electricity and heat.
Read also: How to choose a gas turbine plant for a CCGT plant
The CCGT efficiency is usually represented by the ratio:
- PGU efficiency \u003d GTU efficiency * B + (1-GTU efficiency * B) * PSU efficiency
B is the degree of binarity of the cycle
Efficiency PSU - Efficiency of a steam power plant
- B = Qks/(Qks+Qku)
Qks is the heat of fuel burned in the combustion chamber of a gas turbine
Qku - heat of additional fuel burned in the waste heat boiler
At the same time, it is noted that if Qku = 0, then B = 1, i.e., the installation is completely binary.
Influence of the degree of binarity on the CCGT efficiency
| B | GTU efficiency | PSU efficiency | CCGT efficiency |
| 1 | 0,32 | 0,3 | 0,524 |
| 1 | 0,36 | 0,32 | 0,565 |
| 1 | 0,36 | 0,36 | 0,590 |
| 1 | 0,38 | 0,38 | 0,612 |
| 0,3 | 0,32 | 0,41 | 0,47 |
| 0,4 | 0,32 | 0,41 | 0,486 |
| 0,3 | 0,36 | 0,41 | 0,474 |
| 0,4 | 0,36 | 0,41 | 0,495 |
| 0,3 | 0,36 | 0,45 | 0,51 |
| 0,4 | 0,36 | 0,45 | 0,529 |
Let's sequentially present the tables with the characteristics of the efficiency of gas turbines and after them the indicators of the CCGT with these gas engines, and compare the efficiency of a separate gas turbine and the efficiency of the CCGT.
Characteristics of modern powerful gas turbines
ABB gas turbines
| Characteristic | GTU model | |
| GT26GTU with reheat | GT24GTU with reheat | |
| ISO power MW | 265 | 183 |
| efficiency % | 38,5 | 38,3 |
| 30 | 30 | |
| 562 | 391 | |
| 1260 | 1260 | |
| 610 | 610 | |
| 50 | 50 | |
Combined-cycle plants with ABB gas turbines
GE gas turbines
| Characteristic | GTU model | |||
| MS7001FA | MS9001FA | MS7001G | MS9001G | |
| ISO power MW | 159 | 226,5 | 240 | 282 |
| efficiency % | 35,9 | 35,7 | 39,5 | 39,5 |
| Compressor pressure ratio | 14,7 | 14,7 | 23,2 | 23,2 |
| Consumption of the working fluid at the exhaust gas turbine kg / s | 418 | 602 | 558 | 685 |
| Initial temperature, in front of the working blades 1 tbsp. FROM | 1288 | 1288 | 1427 | 1427 |
| The temperature of the working fluid at the exhaust C | 589 | 589 | 572 | 583 |
| Generator speed 1/s | 60 | 50 | 60 | 50 |
Read also: Why build Combined Cycle Thermal Power Plants? What are the advantages of combined cycle plants.
Combined-cycle plants with GE gas turbines
| Characteristic | GTU model | |||
| MS7001FA | MS9001FA | MS7001G | MS9001G | |
| The composition of the gas turbine part of the CCGT | 1хMS7001FA | 1хMS9001FA | 1хMS9001G | 1xMS9001H |
| CCGT model | S107FA | S109FA | S109G | S109H |
| CCGT power MW | 259.7 | 376.2 | 420.0 | 480.0 |
| CCGT efficiency % | 55.9 | 56.3 | 58.0 | 60.0 |
Siemens gas turbines
| Characteristic | GTU model | |||
| V64.3A | V84.3A | V94.3A | ||
| ISO power MW | 70 | 170 | 240 | |
| efficiency % | 36,8 | 38 | 38 | |
| Compressor pressure ratio | 16,6 | 16,6 | 16,6 | |
| Consumption of the working fluid at the exhaust gas turbine kg / s | 194 | 454 | 640 | |
| Initial temperature, in front of the working blades 1 tbsp. FROM | 1325 | 1325 | 1325 | |
| The temperature of the working fluid at the exhaust C | 565 | 562 | 562 | |
| Generator speed 1/s | 50/60 | 60 | 50 | |
Combined-cycle plants with Siemens gas turbines
Westinghouse-Mitsubishi-Fiat gas turbines
| Characteristic | GTU model | ||||
| 501F | 501G | 701F | 701G1 | 701G2 | |
| ISO power MW | 167 | 235,2 | 251,1 | 271 | 308 |
| efficiency % | 36,1 | 39 | 37 | 38,7 | 39 |
| Compressor pressure ratio | 14 | 19,2 | 16,2 | 19 | 21 |
| Consumption of the working fluid at the exhaust gas turbine kg / s | 449,4 | 553,4 | 658,9 | 645 | 741 |
| Initial temperature, in front of the working blades 1 tbsp. FROM | 1260 | 1427 | 1260 | 1427 | 1427 |
| The temperature of the working fluid at the exhaust C | 596 | 590 | 569 | 588 | 574 |
| Generator speed 1/s | 60 | 60 | 50 | 50 | 50 |
Gas turbine units (GTUs) are in demand in industry, the transport sector, and are widely used in the energy industry. This equipment is not very complex in design, which has a high efficiency and is economical to use.
Gas turbines are in many ways similar to engines running on diesel or gasoline: as in internal combustion engines, the thermal energy obtained from the combustion of fuel is converted into mechanical energy. At the same time, combustion products are used in open-type installations, in closed systems - gas or ordinary air. Both are equally in demand. In addition to open and closed, there are turbocompressor turbines and installations with free-piston gas generators.
It is easiest to consider the design and operation of a gas turbine in a turbocompressor-type plant that operates at constant pressure.
Gas turbine design
The gas turbine consists of a compressor, an air duct, a combustion chamber, a nozzle, a flow path, fixed and working blades, an exhaust gas pipe, a gearbox, a propeller and a starting engine.
The starting motor is responsible for starting the turbine. It drives the compressor, which spins up to the desired speed. Then:
- the compressor captures air from the atmosphere and compresses it;
- air is sent to the combustion chamber through an air duct;
- fuel enters the same chamber through the nozzle;
- gas and air mix and burn at constant pressure, resulting in the formation of combustion products;
- combustion products are cooled with air, after which they enter the flow path;
- in the fixed blades, the gas mixture expands and accelerates, then it is directed to the working blades and sets them in motion;
- the exhaust mixture exits the turbine through a pipe;
- the turbine transmits kinetic energy to the compressor and propeller through a gearbox.
Thus, the gas mixed with air, when burned, forms a working medium, which, expanding, accelerates and spins the blades, and behind them the propeller. Subsequently, the kinetic energy is converted into electricity or used to propel the ship.
You can save on fuel using the principle of heat recovery. In this case, the air entering the turbine is heated by the exhaust gases. As a result, the plant consumes less fuel and more kinetic energy is produced. The regenerator, where the air is heated, also serves to cool the exhaust gases.
Features of gas turbine of closed type
An open-type gas turbine takes air from the atmosphere and exhausts the exhaust gas outside. This is not very effective and dangerous if the unit is in a closed room where people work. In this case, a closed-type gas turbine is used. Such turbines do not release the spent working fluid into the atmosphere, but direct it to the compressor. It does not mix with combustion products. As a result, the working medium circulating in the turbine remains clean, which increases the life of the installation and reduces the number of breakdowns.
However, closed turbines are too large. Gases that do not escape to the outside must be sufficiently effectively cooled. This is only possible in large heat exchangers. Therefore, installations are used on large ships where there is enough space.
Closed gas turbines can also have a nuclear reactor. They use carbon dioxide, helium or nitrogen as a heat carrier. The gas is heated in the reactor and sent to the turbine.
GTP and their differences from steam turbines and internal combustion engines
Gas turbines differ from internal combustion engines in their simpler design and ease of repair. It is also important that they do not provide for a crank mechanism, which makes the internal combustion engine bulky and heavy. The turbine is lighter and less than an engine of similar power by about half. In addition, it can run on low-grade fuel.
Gas turbines differ from steam turbines in their small size and simple start-up. They are easier to maintain than steam plants.
They have turbines and disadvantages: they are not so economical compared to internal combustion engines, they make more noise, they become unusable faster. However, this does not prevent the use of gas turbines in transport, industry and even everyday life. Turbines are installed on sea and river vessels, used in power plants, pumping equipment and many other areas. They are convenient and mobile, so they are used quite often.
"Turbo", "turbojet", "turboprop" - these terms have firmly entered the lexicon of 20th century engineers involved 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, rockets, ships and power plants, the gas turbine is most often used. How is it organized? Does it run on natural gas (as the name might suggest), and what are they like? How is a turbine different from other types of internal combustion engine? What are its advantages and disadvantages? An attempt to answer these questions as fully as possible is made in this article.
Russian machine-building leader UEC
Russia, unlike many other independent states formed after the collapse of the USSR, managed to largely preserve the machine-building industry. In particular, the Saturn company is engaged in the production of special-purpose power plants. The gas turbines of this company are used in shipbuilding, the raw materials industry and energy. The products are high-tech, they require a special approach during installation, debugging and operation, as well as special knowledge and expensive equipment during scheduled maintenance. All these services are available to customers of UEC - Gas Turbines, as it is called today. There are not so many such enterprises in the world, although the principle of arranging the main product is at first glance simple. The accumulated experience is of great importance, which makes it possible to take into account many technological subtleties, without which it is impossible to achieve a durable and reliable operation of the unit. Here is just a part of the UEC product range: 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 an individual approach in each case. The calculation of a gas turbine is currently fully automated, but the materials and features of the wiring diagrams matter in each individual case.
And it all started so easy...
Searches and couples
The first experiments of converting the translational energy of the flow into rotational force were carried out by mankind in ancient times, using an ordinary water wheel. Everything is extremely simple, liquid flows from top to bottom, 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 wheel turned faster. By the way, the so-called "eolipil", invented by the ancient Greek Heron about 130 years before the birth of Christ, was a steam engine that works exactly on this principle. In essence, this was the first gas turbine known to historical science (after all, steam is a gaseous state of aggregation of water). Today, however, it is customary to separate these two concepts. Heron's invention was then treated in Alexandria without much enthusiasm, although with curiosity. Turbine-type industrial equipment appeared only at the end of the 19th century, after the creation of the world's first active power unit equipped with a nozzle by the Swede Gustaf Laval. Approximately in the same direction, engineer Parsons worked, supplying his machine with several functionally connected steps.
The birth of gas turbines
A century earlier, a certain John Barber had a brilliant idea. Why do you need to heat the steam first, is it not easier to use directly the exhaust gas generated during the combustion of fuel, and thereby eliminate unnecessary mediation in the energy conversion process? This is how the first real gas turbine came about. The 1791 patent lays out the basic idea of being used in a horseless carriage, but elements of it are used today in modern rocket, aircraft, tank, and automobile engines. The beginning of the process of jet engine building was given in 1930 by Frank Whittle. He came up with the idea of using a turbine to propel an airplane. Later, she found development in numerous turboprop and turbojet projects.
Nikola Tesla gas turbine
The famous scientist-inventor has always approached the issues under study in a non-standard way. It seemed obvious to everyone that wheels with paddles or blades "catch" the movement of the medium better than flat objects. Tesla, in his characteristic manner, proved that if you assemble a rotor system from discs arranged in series on the axis, then by picking up the boundary layers with a gas flow, it will rotate no worse, and in some cases even better, than a multi-bladed propeller. True, the direction of the moving medium should be tangential, which is not always possible or desirable in modern units, but the design is greatly simplified - it does not need blades at all. A gas turbine according to the Tesla scheme is not being built yet, but perhaps the idea is just waiting for its time.
circuit diagram
Now about the fundamental device of the machine. It is a combination of a rotating system mounted on an axis (rotor) and a fixed part (stator). On the shaft there is a disk with working blades forming a concentric lattice, they are affected by gas supplied under pressure through special nozzles. Then the expanded gas enters the impeller, also equipped with blades, called workers. For the inlet of the air-fuel mixture and the outlet (exhaust), special pipes are used. The compressor is also involved in the overall scheme. It can be made according to a different principle, depending on the required working pressure. For its operation, a part of the energy is taken from the axis, which is used to compress the air. The gas turbine works by means of the process of combustion of the air-fuel mixture, accompanied by a significant increase in volume. The shaft rotates, its energy can be used usefully. Such a scheme is called single-circuit, but if it is repeated, then it is considered multi-stage.
Advantages of aircraft turbines
Since about the mid-fifties, a new generation of aircraft has appeared, including passenger ones (in the USSR these are Il-18, An-24, An-10, Tu-104, Tu-114, Tu-124, etc.), in designs of which aircraft piston engines were finally and irrevocably supplanted by turbine ones. This indicates a greater efficiency of this type of power plant. The characteristics of a gas turbine are superior to those of carbureted engines in many ways, in particular, in terms of power / weight, which is of paramount importance for aviation, as well as in equally important indicators of reliability. Lower fuel consumption, fewer moving parts, better environmental performance, reduced noise and vibration. Turbines are less critical to fuel quality (which cannot be said about fuel systems), they are easier to maintain, they require less lubricating oil. In general, at first glance it seems that they do not consist of metal, but of solid virtues. Alas, it is not.
There are disadvantages of gas turbine engines
The gas turbine heats up during operation and transfers heat to the surrounding structural elements. This is especially critical, again in aviation, when using a redan layout scheme that involves washing the lower part of the tail unit with a jet stream. And the engine housing 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 work in the mode of a virtually permanent explosion occurring in the body. The efficiency in some modes is lower than that of carburetor engines, however, when using a two-circuit scheme, this disadvantage is eliminated, although the design becomes more complicated, as in the case of including “booster” compressors in the scheme. Acceleration of turbines and reaching the operating mode requires some time. The more often the unit starts and stops, the faster it wears out.
Correct Application
Well, no system is without flaws. It is important to find such an application of each of them, in which its advantages will be more clearly manifested. For example, tanks such as the American Abrams, which is powered by a gas turbine. It can be filled with anything that burns, from high-octane gasoline to whiskey, and it puts out a lot of power. This may not be a very good example, as experience in Iraq and Afghanistan has shown the vulnerability of compressor blades to sand. Repair of gas turbines has to be done in the USA, at the manufacturing plant. Take the tank there, then back, and the cost of the maintenance itself, plus accessories ...
Helicopters, Russian, American and other countries, as well as powerful speedboats, are less affected by clogging. In liquid rockets, they are indispensable.
Modern warships and civilian ships also have gas turbine engines. And also energy.
Trigenerator power plants
The problems faced by aircraft manufacturers are not as worrying for those who make industrial equipment for generating electricity. Weight in this case is no longer so important, and you can focus on parameters such as efficiency and overall efficiency. Gas turbine generator units have a massive frame, a reliable frame and thicker blades. It is quite possible to utilize the generated heat, using it for a variety of needs, from secondary recycling in the system itself, to heating domestic premises and thermal 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, it makes no fundamental difference what is the source of the heated medium that gives its energy to its blades. It can be a burnt air-fuel mixture, or simply superheated steam (not necessarily water), the main thing is that it ensures its uninterrupted power supply. At its 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. Safety and environmental issues dictate a closed primary loop. This means that the primary heat agent (in the first samples this role was played by lead, now it has been replaced by paraffin) does not leave the near-reactor zone, flowing around the fuel elements in a circle. The heating of the working substance is carried out in subsequent circuits, and the evaporated carbon dioxide, helium or nitrogen rotates the turbine wheel.
Wide application
Complex and large installations are almost always unique, their production is carried out in small batches or in general single copies are made. Most often, units produced in large quantities are used in peaceful sectors of the economy, for example, for pumping hydrocarbon raw materials through pipelines. It is these that are produced by the UEC company under the Saturn brand. Gas turbines of pumping stations are fully consistent with their name. They really pump natural gas, using its own energy for their work.