Adjustment and testing of steam turbines. Method for testing turbines and stand for its implementation. Basic rules for the installation of turbines

Thermal testing of steam turbines
and turbine equipment

In recent years, in the line of energy saving, attention has increased to fuel consumption standards for enterprises generating heat and electricity, therefore, for generating enterprises, the actual efficiency indicators of heat and power equipment are becoming important.

At the same time, it is known that the actual efficiency indicators under operating conditions differ from the calculated (factory), therefore, in order to objectively standardize fuel consumption for the generation of heat and electricity, it is advisable to test the equipment.

On the basis of equipment test materials, normative energy characteristics and a layout (order, algorithm) for calculating the norms are developed unit costs fuel in accordance with RD 34.09.155-93 "Guidelines for compiling and maintaining the energy characteristics of equipment for thermal power plants" and RD 153-34.0-09.154-99 "Regulations on the regulation of fuel consumption at power plants".

Of particular importance is the testing of heat and power equipment for facilities operating equipment put into operation before the 70s and where modernization and reconstruction of boilers, turbines, auxiliary equipment was carried out. Without testing, normalization of fuel consumption according to the calculated data will lead to significant errors not in favor of generating enterprises. Therefore, the costs of thermal testing are negligible compared to the benefits.

The objectives of thermal testing of steam turbines and turbine equipment: determination of actual efficiency; obtaining thermal characteristics; comparison with manufacturer's warranties; obtaining data for standardization, control, analysis and optimization of turbine equipment operation; obtaining materials for the development of energy characteristics; development of measures to improve efficiency

The objectives of express testing of steam turbines: determination of the feasibility and scope of repairs; assessment of the quality and effectiveness of the repair or modernization; assessment of the current change in the efficiency of the turbine during operation.

Modern technologies and the level of engineering knowledge make it possible to economically upgrade units, improve their performance and increase their service life.

The main goals of modernization are:

reduction of power consumption of the compressor unit;

increase in compressor performance;

increasing the power and efficiency of the process turbine;

reduction of natural gas consumption;

increasing the operational stability of equipment;

reducing the number of parts by increasing the pressure of compressors and operating turbines at a smaller number of stages while maintaining and even increasing the efficiency of the power plant.

The improvement of the given energy and economic indicators of the turbine unit is carried out through the use of modernized design methods (solution of the direct and inverse problems). They are related:

with the inclusion of more correct models of turbulent viscosity in the calculation scheme,

taking into account the profile and end blockage by the boundary layer,

elimination of separation phenomena with an increase in the diffuseness of the interblade channels and a change in the degree of reactivity (pronounced non-stationarity of the flow before the occurrence of surge),

the possibility of identifying an object using mathematical models with genetic parameter optimization.

The ultimate goal of modernization is always to increase the production of the final product and minimize costs.

An integrated approach to the modernization of turbine equipment

When carrying out modernization, Astronit usually uses an integrated approach, in which the following components of the technological turbine unit are reconstructed (modernized):

compressor;

• centrifugal compressor-supercharger;

  intercoolers;

  multiplier;

  Lubrication system;

  air cleaning system;

  automatic control and protection system.

Modernization of compressor equipment

The main areas of modernization practiced by Astronit specialists:

replacement of flow parts with new ones (the so-called replaceable flow parts, including impellers and vaned diffusers), with improved characteristics, but in the dimensions of existing housings;

reduction in the number of stages due to the improvement of the flow path based on three-dimensional analysis in modern software products;

application of easy-to-work coatings and reduction of radial clearances;

replacement of seals with more efficient ones;

replacement of compressor oil bearings with "dry" bearings using magnetic suspension. This eliminates the use of oil and improves the operating conditions of the compressor.

Implementation of modern control and protection systems

To improve operational reliability and efficiency, modern instrumentation, digital automatic control and protection systems (both individual parts and the entire technological complex as a whole), diagnostic systems and communication systems are being introduced.

STEAM TURBINES

Nozzles and blades.

Thermal cycles.

Rankine cycle.

Reheat cycle.

Cycle with intermediate extraction and utilization of exhaust steam heat.

Turbine structures.

Application.

OTHER TURBINES

Hydraulic turbines.

gas turbines.

Scroll upScroll down

Also on topic

AIRCRAFT POWER PLANTS

ELECTRIC ENERGY

SHIP POWER PLANTS AND PROPULSIONS

HYDROPOWER

TURBINE

TURBINE, prime mover with rotational movement of the working body for converting the kinetic energy of the flow of a liquid or gaseous working fluid into mechanical energy on the shaft. The turbine consists of a rotor with blades (bladed impeller) and a casing with nozzles. Branch pipes bring in and divert the flow of the working fluid. Turbines, depending on the working fluid used, are hydraulic, steam and gas. Depending on the average direction of flow through the turbine, they are divided into axial, in which the flow is parallel to the axis of the turbine, and radial, in which the flow is directed from the periphery to the center.

STEAM TURBINES

The main elements of a steam turbine are the casing, nozzles and rotor blades. Steam from an external source is supplied to the turbine through pipelines. In the nozzles, the potential energy of the steam is converted into the kinetic energy of the jet. The steam escaping from the nozzles is directed to curved (specially profiled) working blades located along the periphery of the rotor. Under the action of a jet of steam, a tangential (circumferential) force appears, causing the rotor to rotate.

Nozzles and blades.

Steam under pressure enters one or more fixed nozzles, in which it expands and from where it flows out at high speed. The flow exits the nozzles at an angle to the plane of rotation of the rotor blades. In some designs, the nozzles are formed by a series of fixed blades (nozzle apparatus). The vanes of the impeller are curved in the direction of flow and arranged radially. In an active turbine (Fig. 1, a) the flow channel of the impeller has a constant cross section, i.e. the speed in relative motion in the impeller does not change in absolute value. The steam pressure in front of the impeller and behind it is the same. In a jet turbine (Fig. 1, b) flow channels of the impeller have a variable cross section. The flow channels of a jet turbine are designed so that the flow rate in them increases, and the pressure decreases accordingly.

R1; c - blading the impeller. V1 is the steam velocity at the outlet of the nozzle; V2 is the speed of steam behind the impeller in a fixed coordinate system; U1 – peripheral speed of the blade; R1 is the speed of steam at the impeller inlet in relative motion; R2 is the speed of steam at the outlet of the impeller in relative motion. 1 - bandage; 2 - scapula; 3 – rotor." title="(!LANG:Fig. 1. TURBINE BLADES. a - active impeller, R1 = R2; b - jet impeller, R2 > R1; c - impeller blades. V1 - steam speed at the nozzle outlet; V2 is the steam velocity behind the impeller in a fixed coordinate system; U1 is the circumferential velocity of the blade; R1 is the steam velocity at the impeller inlet in relative motion; R2 is the steam velocity at the impeller outlet in relative motion. 1 - bandage; 2 - blade; 3 - rotor.">Рис. 1. РАБОЧИЕ ЛОПАТКИ ТУРБИНЫ. а – активное рабочее колесо, R1 = R2; б – реактивное рабочее колесо, R2 > R1; в – облопачивание рабочего колеса. V1 – скорость пара на выходе из сопла; V2 – скорость пара за рабочим колесом в неподвижной системе координат; U1 – окружная скорость лопатки; R1 – скорость пара на входе в рабочее колесо в относительном движении; R2 – скорость пара на выходе из рабочего колеса в относительном движении. 1 – бандаж; 2 – лопатка; 3 – ротор.!}

Turbines are usually designed to be on the same shaft as the device that consumes their energy. The speed of rotation of the impeller is limited by the tensile strength of the materials from which the disk and blades are made. For the most complete and efficient conversion of steam energy, turbines are made multi-stage.

Thermal cycles.

Rankine cycle.

In a turbine operating according to the Rankine cycle (Fig. 2, a), steam comes from an external steam source; there is no additional steam heating between the turbine stages, there are only natural heat losses.

Reheat cycle.

In this cycle (Fig. 2, b) steam after the first stages is sent to the heat exchanger for additional heating (overheating). Then it returns to the turbine again, where its final expansion takes place in subsequent stages. Increasing the temperature of the working fluid allows you to increase the efficiency of the turbine.

Rice. 2. TURBINES WITH DIFFERENT HEAT CYCLES. a – simple Rankine cycle; b – cycle with intermediate steam heating; c - cycle with intermediate steam extraction and heat recovery.

Cycle with intermediate extraction and utilization of exhaust steam heat.

The steam at the outlet of the turbine still has significant thermal energy, which is usually dissipated in the condenser. Part of the energy can be taken from the condensation of the exhaust steam. Some part of the steam can be taken from the intermediate stages of the turbine (Fig. 2, in) and is used for preheating, for example, feed water or for any technological processes.

Turbine structures.

The working medium expands in the turbine, so the last stages (low pressure) must have a larger diameter in order to pass the increased volume flow. The increase in diameter is limited by the allowable maximum stresses due to centrifugal loads at elevated temperatures. In split-flow turbines (Figure 3), the steam passes through different turbines or different turbine stages.

Rice. 3. TURBINES WITH FLOW BRANCHING. a - double parallel turbine; b – double turbine of parallel action with oppositely directed flows; c – turbine with flow branching after several stages of high pressure; d - compound turbine.

Application.

To ensure high efficiency, the turbine must rotate with high speed, however, the number of revolutions is limited by the strength of the materials of the turbine and the equipment that is on the same shaft with it. Electric generators in thermal power plants are rated at 1800 or 3600 rpm and are usually installed on the same shaft as the turbine. Centrifugal superchargers and pumps, fans and centrifuges can be installed on the same shaft with the turbine.

The low speed equipment is coupled to the high speed turbine via a reduction gear, such as in marine engines where the propeller must rotate at 60 to 400 rpm.

OTHER TURBINES

Hydraulic turbines.

In modern hydraulic turbines, the impeller rotates in a special housing with a volute (radial turbine) or has a guide vane at the inlet to ensure the desired flow direction. The appropriate equipment is usually installed on the shaft of a hydroturbine (an electric generator at a hydroelectric power station).

gas turbines.

The gas turbine uses the energy of gaseous combustion products from an external source. Gas turbines are similar in design and principle of operation to steam turbines and are widely used in engineering. see also AIRCRAFT POWER PLANTS; ELECTRIC ENERGY; SHIP POWER PLANTS AND PROPULSIONS; HYDROPOWER.

Literature

Uvarov V.V. Gas turbines and gas turbine plants. M., 1970
Verete A.G., Delving A.K. Marine steam power plants and gas turbines. M., 1982 equipment: basic (boiler plants and steam turbines) and auxiliary. For powerful turbines(And it's about...

Thermal trial gas turbine plant

Laboratory work>> Physics

UPI "Department" Turbines and engines "Laboratory work No. 1" Thermal trial gas turbine plant" Option ... as part of the complex equipment the test stand was turned on ... the launcher was applied steam turbine built on the basis...

Choice of diaphragm blade welding method steam turbines (2)

Coursework >> Industry, production

Melting using thermal energy (arc, ... details steam turbines. shoulder blades steam turbines subdivided... – manufacturability, – availability of the necessary equipment, – availability of qualified personnel, – ... with relevant trials. Thereafter...

thermal power unit scheme

Diploma work >> Physics

... test; ... equipment thermal power plants. – M.: Energoatomizdat, 1995. Ryzhkin V.Ya. Thermal... power stations. – M.: Energoatomizdat, 1987. Shklover G.G., Milman O.O. Research and calculation of condensing devices steam turbines ...

In recent years, in the line of energy saving, attention has increased to fuel consumption standards for enterprises generating heat and electricity, therefore, for generating enterprises, the actual efficiency indicators of heat and power equipment are becoming important.
At the same time, it is known that the actual efficiency indicators under operating conditions differ from the calculated (factory), therefore, in order to objectively standardize fuel consumption for the generation of heat and electricity, it is advisable to test the equipment.
On the basis of equipment test materials, normative energy characteristics and a layout (order, algorithm) for calculating the norms of specific fuel consumption are developed in accordance with RD 34.09.155-93 "Guidelines for the compilation and maintenance of energy characteristics of thermal power plant equipment" and RD 153-34.0-09.154 -99 "Regulations on the regulation of fuel consumption at power plants."
Of particular importance is the testing of heat and power equipment for facilities operating equipment put into operation before the 70s and on which modernization and reconstruction of boilers, turbines, auxiliary equipment. Without testing, normalization of fuel consumption according to the calculated data will lead to significant errors not in favor of generating enterprises. Therefore, the costs of thermal testing are negligible compared to the benefits.

The objectives of thermal testing of steam turbines and turbine equipment: determination of actual economy; obtaining thermal characteristics; comparison with manufacturer's warranties; obtaining data for standardization, control, analysis and optimization of turbine equipment operation; obtaining materials for the development of energy characteristics; development of measures to improve efficiency

The objectives of express testing of steam turbines: determination of the feasibility and scope of repairs; assessment of the quality and effectiveness of the repair or modernization; assessment of the current change in the efficiency of the turbine during operation.

Modern technologies and the level of engineering knowledge make it possible to economically upgrade units, improve their performance and increase their service life.

The main goals of modernization are:

reduction of power consumption of the compressor unit;
increase in compressor performance;
increasing the power and efficiency of the process turbine;
reduction of natural gas consumption;
increasing the operational stability of equipment;
reducing the number of parts by increasing the pressure of compressors and operating turbines at a smaller number of stages while maintaining and even increasing the efficiency of the power plant.

Improvement of the reduced energy and economic indicators turbine unit is produced by using modernized design methods (solution of direct and inverse problems). They are related:

with the inclusion of more correct models of turbulent viscosity in the calculation scheme,
taking into account the profile and end blockage by the boundary layer,
elimination of separation phenomena with an increase in the diffuseness of the interblade channels and a change in the degree of reactivity (pronounced non-stationarity of the flow before the occurrence of surge),
the possibility of identifying an object using mathematical models with genetic optimization of parameters.

The ultimate goal of modernization is always to increase the production of the final product and minimize costs.

An integrated approach to the modernization of turbine equipment

When carrying out modernization, Astronit usually uses an integrated approach, in which the following components of the technological turbine unit are reconstructed (modernized):

compressor;
turbine;
supports;
centrifugal compressor-supercharger;
intercoolers;
multiplier;
Lubrication system;
air cleaning system;
automatic control and protection system.

Modernization of compressor equipment

The main areas of modernization practiced by Astronit specialists:

replacement of flow parts with new ones (the so-called replaceable flow parts, including impellers and vaned diffusers), with improved characteristics, but in the dimensions of existing housings;
reduction in the number of stages due to the improvement of the flow path based on three-dimensional analysis in modern software products;
application of easy-to-work coatings and reduction of radial clearances;
replacement of seals with more efficient ones;
replacement of compressor oil bearings with "dry" bearings using magnetic suspension. This eliminates the use of oil and improves the operating conditions of the compressor.

Implementation of modern control and protection systems

To improve operational reliability and efficiency, modern instrumentation, digital automatic control and protection systems are being introduced (both individual parts and the entire technological complex in general), diagnostic systems and communication systems.

The content of the article

STEAM TURBINES
Nozzles and blades.
Thermal cycles.
Rankine cycle.
Reheat cycle.
Cycle with intermediate extraction and utilization of exhaust steam heat.
Turbine structures.
Application.
OTHER TURBINES
Hydraulic turbines.
gas turbines.

scroll up scroll down
Also on topic

AIRCRAFT POWER PLANTS
ELECTRIC ENERGY
SHIP POWER PLANTS AND PROPULSIONS
HYDROPOWER

TURBINE

TURBINE, prime mover with rotational movement working body for converting the kinetic energy of the flow of a liquid or gaseous working fluid into mechanical energy on the shaft. The turbine consists of a rotor with blades (bladed impeller) and a casing with nozzles. Branch pipes bring in and divert the flow of the working fluid. Turbines, depending on the working fluid used, are hydraulic, steam and gas. Depending on the average direction of flow through the turbine, they are divided into axial, in which the flow is parallel to the axis of the turbine, and radial, in which the flow is directed from the periphery to the center.
etc.................

During autonomous testing of turbines, the main tasks are to obtain their characteristics in a wide range of determining parameters, as well as to study the strength and thermal state of blades and disks.

The implementation of turbine operating conditions on an autonomous stand is a very difficult problem. Air is supplied to such stands (Fig. 8.5) from the compressor station through pipeline 3, gas is heated in combustion chamber 4. Turbine power is absorbed by hydraulic brake 1 (it is possible to use electric generators and compressors for this purpose). In contrast to tests in the engine system, when the turbine characteristic can be obtained practically only along the line of operating modes (see Chap. 5), the entire field of characteristics is realized on an autonomous bench, since in this case any values ​​of the input parameters can be set, and regulate the turbine speed by loading the hydraulic brake.

When simulating terrestrial engine operation modes or modes corresponding to high flight speeds, the gas pressure values ​​in front of the turbine and behind it will exceed atmospheric ones, and after leaving the turbine, the gas can be released into the atmosphere (operation with pressurization in an open circuit).

Rice. 8.5. Scheme of the stand for testing turbines in natural conditions:

1 - hydraulic brake; 2 - water supply; 3 - compressed air supply: 4 - combustion chamber; 5 - turbine; 6 - exhaust pipeline

Supercharged operation is characterized by the greatest technical difficulties, since it requires a lot of energy to drive compressors and high-power braking devices.

For testing the turbine in conditions close to high-altitude, suction benches are designed. The scheme of such a stand is shown in fig. 8.6. The air in the flow part of the stand comes directly from the atmosphere through the inlet 1, a vacuum is created behind the turbine using an exhauster or an ejector.

The power of the turbine 4 is absorbed by the hydraulic brake 3. Tests can be carried out both at elevated and at low inlet temperatures. Test modes are selected taking into account the principles of the theory of similarity discussed above.

Permeation tests can be considered as model tests for modes in which the pressure at the turbine inlet must be greater than atmospheric pressure. The characteristics obtained in this case will correspond well enough to natural conditions if the Re numbers are in the self-similar region.

Tests at low pressures and temperatures can significantly reduce the energy consumption for the exhauster drive and reduce the required power of the hydraulic brake, which greatly simplifies testing.

To an even greater extent, the noted difficulties are eliminated if models reduced by two or three times, as well as special working bodies, are used. In the latter case, the tests should be carried out in a closed circuit in the same way as was considered for compressors (see Section 8.2).

When determining the characteristics of turbines, measurements of gas flow rate G g, flow parameters in front of the turbine and behind it T * g, T * t, p * g, p * t, rotational speed n, power developed by the turbine, N t, as well as the exit angle flow from the turbine a t. The same measurement methods are used as when testing compressors. In particular, the value of N t is determined, as a rule, from the measured values ​​of n and the torque M cr, and to measure the latter, hydraulic brakes with a oscillating body installation are used (see Ch. 4).

To construct the characteristics of the turbine, the parameters arising from the theory of similarity are used. In particular, they can be represented as dependencies

Rice. 8.6. Scheme of the stand for testing turbines for suction:

1 - input device; 2 - air heater; 3 - hydraulic brake; 4 - turbine; 5 - control damper; 6 - air duct to exhauster or ejector

Here p* t =p* g /p* t is the degree of pressure reduction in the turbine; - relative reduced speed; - relative parameter of gas flow through the turbine; h* t =L t /L* t S - turbine efficiency; L t =N t /G t - the actual operation of the turbine; - isentropic operation of the turbine.

When determining the characteristics, the specified value of n is maintained by changing the hydraulic brake load, and the change in G g and p * t is produced by changing the operating mode of the exhauster or compressor and the throttle position.

Thermal testing steam turbines
and turbine equipment

AT last years In the line of energy saving, attention has increased to the fuel consumption standards for enterprises generating heat and electricity, therefore, for generating enterprises, the actual efficiency indicators of heat and power equipment are becoming important.

At the same time, it is known that the actual efficiency indicators under operating conditions differ from the calculated (factory), therefore, in order to objectively standardize fuel consumption for the generation of heat and electricity, it is advisable to test the equipment.

On the basis of equipment test materials, normative energy characteristics and a layout (order, algorithm) for calculating the norms of specific fuel consumption are developed in accordance with RD 34.09.155-93 "Guidelines for the compilation and maintenance of energy characteristics of thermal power plant equipment" and RD 153-34.0-09.154 -99 "Regulations on the regulation of fuel consumption at power plants."

Of particular importance is the testing of heat and power equipment for facilities operating equipment put into operation before the 70s and where modernization and reconstruction of boilers, turbines, auxiliary equipment was carried out. Without testing, normalization of fuel consumption according to the calculated data will lead to significant errors not in favor of generating enterprises. Therefore, the costs of thermal testing are negligible compared to the benefits.

The objectives of thermal testing of steam turbines and turbine equipment: determination of actual efficiency; obtaining thermal characteristics; comparison with manufacturer's warranties; obtaining data for standardization, control, analysis and optimization of turbine equipment operation; obtaining materials for the development of energy characteristics; development of measures to improve efficiency

The objectives of express testing of steam turbines: determination of the feasibility and scope of repairs; assessment of the quality and effectiveness of the repair or modernization; assessment of the current change in the efficiency of the turbine during operation.

Modern technologies and the level of engineering knowledge make it possible to economically upgrade units, improve their performance and increase their service life.

The main goals of modernization are:

• reduction of power consumption of the compressor unit;
• increase in compressor performance;
• increasing the power and efficiency of the process turbine;
• reduction of natural gas consumption;
• increasing the operational stability of equipment;
• reducing the number of parts by increasing the pressure of compressors and operating turbines at a smaller number of stages while maintaining and even increasing the efficiency of the power plant.

The improvement of the given energy and economic indicators of the turbine unit is carried out through the use of modernized design methods (solution of the direct and inverse problems). They are related:

• with the inclusion of more correct models of turbulent viscosity in the calculation scheme,
• taking into account the profile and end blockage by the boundary layer,
• elimination of separation phenomena with an increase in the diffuseness of the interblade channels and a change in the degree of reactivity (pronounced non-stationarity of the flow before the occurrence of surge),
• the possibility of identifying an object using mathematical models with genetic optimization of parameters.

The ultimate goal of modernization is always to increase the production of the final product and minimize costs.

An integrated approach to the modernization of turbine equipment

When carrying out modernization, Astronit usually uses an integrated approach, in which the following components of the technological turbine unit are reconstructed (modernized):

• compressor;
• turbine;
• supports;
• centrifugal compressor-supercharger;
• intercoolers;
• multiplier;
• Lubrication system;
• air cleaning system;
• automatic control and protection system.

Modernization of compressor equipment

The main areas of modernization practiced by Astronit specialists:

• replacement of flow parts with new ones (the so-called replaceable flow parts, including impellers and vaned diffusers), with improved characteristics, but in the dimensions of existing housings;
• reduction in the number of stages due to the improvement of the flow path based on three-dimensional analysis in modern software products;
• application of easy-to-work coatings and reduction of radial clearances;
• replacement of seals with more efficient ones;
• replacement of compressor oil bearings with "dry" bearings using magnetic suspension. This eliminates the use of oil and improves the operating conditions of the compressor.

Implementation modern systems control and protection

To improve operational reliability and efficiency, modern instrumentation, digital automatic control and protection systems (both individual parts and the entire technological complex as a whole), diagnostic systems and communication systems are being introduced.

• STEAM TURBINES
• Nozzles and blades.
• Thermal cycles.
• Rankine cycle.
• Turbine structures.
• Application.
• OTHER TURBINES
• Hydraulic turbines.
• gas turbines.

Scroll upScroll down

Also on topic

• AIRCRAFT POWER PLANTS
• ELECTRIC ENERGY
• SHIP POWER PLANTS AND PROPULSIONS
• HYDROPOWER

TURBINE

TURBINE, prime mover with rotational movement of the working body for converting the kinetic energy of the flow of a liquid or gaseous working fluid into mechanical energy on the shaft. The turbine consists of a rotor with blades (bladed impeller) and a casing with nozzles. Branch pipes bring in and divert the flow of the working fluid. Turbines, depending on the working fluid used, are hydraulic, steam and gas. Depending on the average direction of flow through the turbine, they are divided into axial, in which the flow is parallel to the axis of the turbine, and radial, in which the flow is directed from the periphery to the center.

STEAM TURBINES

The main elements of a steam turbine are the casing, nozzles and rotor blades. Steam from an external source is supplied to the turbine through pipelines. In the nozzles, the potential energy of the steam is converted into the kinetic energy of the jet. The steam escaping from the nozzles is directed to curved (specially profiled) working blades located along the periphery of the rotor. Under the action of a jet of steam, a tangential (circumferential) force appears, causing the rotor to rotate.

Nozzles and blades.

Steam under pressure enters one or more fixed nozzles, in which it expands and from where it flows out at high speed. The flow exits the nozzles at an angle to the plane of rotation of the rotor blades. In some designs, the nozzles are formed by a series of fixed blades (nozzle apparatus). The vanes of the impeller are curved in the direction of flow and arranged radially. In an active turbine (Fig. 1, a) the flow channel of the impeller has a constant cross section, i.e. the speed in relative motion in the impeller does not change in absolute value. The steam pressure in front of the impeller and behind it is the same. In a jet turbine (Fig. 1, b) flow channels of the impeller have a variable cross section. The flow channels of a jet turbine are designed so that the flow rate in them increases, and the pressure decreases accordingly.

R1; c - blading the impeller. V1 is the steam velocity at the outlet of the nozzle; V2 is the speed of steam behind the impeller in a fixed coordinate system; U1 – peripheral speed of the blade; R1 is the speed of steam at the impeller inlet in relative motion; R2 is the speed of steam at the outlet of the impeller in relative motion. 1 - bandage; 2 - scapula; 3 – rotor." title="(!LANG:Fig. 1. TURBINE BLADES. a - active impeller, R1 = R2; b - jet impeller, R2 > R1; c - impeller blades. V1 - steam speed at the nozzle outlet; V2 is the steam velocity behind the impeller in a fixed coordinate system; U1 is the circumferential velocity of the blade; R1 is the steam velocity at the impeller inlet in relative motion; R2 is the steam velocity at the impeller outlet in relative motion. 1 - bandage; 2 - blade; 3 - rotor.">Рис. 1. РАБОЧИЕ ЛОПАТКИ ТУРБИНЫ. а – активное рабочее колесо, R1 = R2; б – реактивное рабочее колесо, R2 > R1; в – облопачивание рабочего колеса. V1 – скорость пара на выходе из сопла; V2 – скорость пара за рабочим колесом в неподвижной системе координат; U1 – окружная скорость лопатки; R1 – скорость пара на входе в рабочее колесо в относительном движении; R2 – скорость пара на выходе из рабочего колеса в относительном движении. 1 – бандаж; 2 – лопатка; 3 – ротор.!}

Turbines are usually designed to be on the same shaft as the device that consumes their energy. The speed of rotation of the impeller is limited by the tensile strength of the materials from which the disk and blades are made. For the most complete and efficient conversion of steam energy, turbines are made multi-stage.

Thermal cycles.

Rankine cycle.

In a turbine operating according to the Rankine cycle (Fig. 2, a), steam comes from an external steam source; there is no additional steam heating between the turbine stages, there are only natural heat losses.

Reheat cycle.

In this cycle (Fig. 2, b) steam after the first stages is sent to the heat exchanger for additional heating (overheating). Then it returns to the turbine again, where its final expansion takes place in subsequent stages. Increasing the temperature of the working fluid allows you to increase the efficiency of the turbine.

Rice. 2. TURBINES WITH DIFFERENT HEAT CYCLES. a – simple Rankine cycle; b – cycle with intermediate steam heating; c - cycle with intermediate steam extraction and heat recovery.

Cycle with intermediate extraction and utilization of exhaust steam heat.

The steam at the outlet of the turbine still has significant thermal energy, which is usually dissipated in the condenser. Part of the energy can be taken from the condensation of the exhaust steam. Some part of the steam can be taken from the intermediate stages of the turbine (Fig. 2, in) and is used for preheating, for example, feed water or for any technological processes.

Turbine structures.

The working medium expands in the turbine, so the last stages (low pressure) must have a larger diameter in order to pass the increased volume flow. The increase in diameter is limited by the allowable maximum stresses due to centrifugal loads at elevated temperatures. In split-flow turbines (Figure 3), the steam passes through different turbines or different turbine stages.

Rice. 3. TURBINES WITH FLOW BRANCHING. a - double parallel turbine; b – double turbine of parallel action with oppositely directed flows; c – turbine with flow branching after several stages of high pressure; d - compound turbine.

Application.

To ensure high efficiency, the turbine must rotate at high speed, but the number of revolutions is limited by the strength of the materials of the turbine and the equipment that is on the same shaft with it. Electric generators in thermal power plants are rated at 1800 or 3600 rpm and are usually installed on the same shaft as the turbine. Centrifugal superchargers and pumps, fans and centrifuges can be installed on the same shaft with the turbine.

The low speed equipment is coupled to the high speed turbine via a reduction gear, such as in marine engines where the propeller must rotate at 60 to 400 rpm.

OTHER TURBINES

Hydraulic turbines.

In modern hydraulic turbines, the impeller rotates in a special housing with a volute (radial turbine) or has a guide vane at the inlet to ensure the desired flow direction. The appropriate equipment is usually installed on the shaft of a hydroturbine (an electric generator at a hydroelectric power station).

gas turbines.

The gas turbine uses the energy of gaseous combustion products from an external source. Gas turbines are similar in design and principle of operation to steam turbines and are widely used in engineering. see also AVIATION POWER PLANT; ELECTRIC ENERGY; SHIP POWER INSTALLATIONS AND ENGINES; HYDROPOWER.

Literature

Uvarov V.V. Gas turbines and gas turbine plants. M., 1970
Verete A.G., Delving A.K. Marine steam power plants and gas turbines. M., 1982
Trubilov M.A. and etc. Steam and gas turbines. M., 1985
Sarantsev K.B. and etc. Atlas of turbine stages. L., 1986
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