Starting system for gas turbine units. Engine starting system for land-based gas turbine units
To start independent work The gas turbine turbocharger must be given a certain rotation speed. This is achieved using some kind of starting motor that accelerates the turbocharger rotor. During the startup process, at 2700-2900 rpm, the fuel supply is turned on and at 2900-3200 rpm, the fuel is ignited. After the fuel has ignited, the ignition is turned off and combustion in the chambers is maintained continuously. As the gas temperature rises and the speed increases, the power generated by the turbine increases, and accordingly the power of the starting engine decreases. Upon reaching approximately 5600 rpm, the starter is turned off and the turbocharger operates independently, in which the turbine power completely provides the power consumed by the compressor.
Asynchronous three-phase AC motors have an unfavorable torque characteristic as a function of speed, so their installed power must be higher than the power consumed by the turbocharger during the start-up period. AC motors with phase rings have the best starting characteristics. Reducing the power of an asynchronous electric motor can be achieved by using a continuously variable transmission between the engine and the turbocharger. Continuously variable transmission can be hydraulic or with positive displacement pumps and hydraulic motors, or with fluid couplings and hydrodynamic transformers.
In very large gas turbines with heavy rotors, the power and dimensions of AC starting motors reach unacceptable values, as a result of which DC electric motors with more favorable characteristics have to be used for starting. As a rule, stations do not have high-power DC sources, so in such cases the starting system includes a separate generator-propulsion unit that converts alternating current into direct current. An additional advantage of such a system is the possibility of long-term running-in of turbochargers at any speed within the permissible power of the electrical system, which is very valuable when setting up the prototype unit and when listening to turbo units after repairs.
To reduce the size of starting electric motors, they are usually significantly overloaded. Therefore, in order to avoid unacceptable overheating of the starting motors, the number of sequential starts in case of unsuccessful starts is usually limited to three; Before subsequent switching on, it is necessary to cool them for 20-30 minutes.
The operating speed of the starting electric motor corresponds to the number of revolutions of the compressor shaft at the moment the gas turbine unit begins to operate independently, therefore, in order to avoid unacceptable excess of the starting motor speed, overrunning clutches are installed between it and the gas turbine unit.
The electric start is powered from an alternating current network of 380 V, 50 Hz. An asynchronous motor with constant speed or a synchronous motor BDPT-1966 is used.
Systems servicing the operation of a gas turbine unit mean a set of technical means with the help of which all operating modes of the installation can be carried out.
The operation of the ship's gas turbine unit is ensured by the following systems:
fuel system;
starting system;
Lubrication system;
prompting system;
reverse system;
cooling system for gas turbine units;
regulation, control and protection system - RUZ GTD;
air intake and gas exhaust devices.
Fuel system
The fuel system of a gas turbine engine is designed to supply fuel to the injectors of combustion chambers in an amount that provides a given engine power, as well as for the preliminary preparation of fuel in gas turbine plants operating on heavy grades of fuel.
Marine gas turbines can use the same types of fuel as diesel power plants:
diesel fuels according to GOST 305-82 grades L− summer, Z− winter, A− arctic;
diesel fuels according to GOST 4749-73 grades DS And DL;
motor fuels according to GOST 1667-68 grades DT(regular and highest quality category) and DM;
gas turbine fuels according to GOST 10433-75 grades TG– normal quality category and TGVK– highest quality category;
naval fuel oils according to GOST 10585-99 grades F-5 And F-12.
In the fuel systems of light ramjet engines, exclusively light distillate fuels are used. The use of cheap low-grade fuels forces one to take into account the consequences associated with their high ash content and impurity content, which can cause corrosion processes in the flow parts of the gas turbine, and contamination of parts of the flow part with ash and resinous substances. Therefore, gas turbine engines operating on heavy grades of fuel have a separate system for preliminary fuel preparation and additive input as part of the fuel system. The operation of gas turbine units using relatively expensive distillate fuels is not associated with any difficulties and does not require special measures to ensure their combustion in the compressor station.
Fuel systems of ship gas turbines must provide the following conditions for engine operation:
the required fuel pressure for high-quality atomization in the nozzles of the combustion chambers;
Fuel viscosity in front of the injectors is no more than 1.2 - 1.5 O E(degrees of viscosity) to obtain proper spray quality;
absence of water content, which reduces the calorific value of the fuel, causes corrosion of fuel equipment and leads to the failure of the flame in the compressor station;
absence of mechanical impurities that clog and wear out injectors, fuel pumps and filters;
receiving fuel into main supply tanks from coastal and floating tank farms.
Fuel systems of gas turbine plants operating on heavy grades of fuel must, in addition to the above, provide:
the possibility of pre-treatment of fuel on the ship;
preheating of heavy fuel to a temperature of 120 ÷ 130 O WITH to reduce its viscosity;
thorough multi-stage fuel filtration and ensuring reliable fuel intake by the main fuel pump;
the possibility of using light starting fuel to facilitate the start-up of gas turbine units;
flushing injectors with light fuel during scheduled stops or blowing them with compressed air during emergency stops to prevent heavy fuel from solidifying in the injectors and ensuring reliable subsequent starts of the gas turbine unit.
Rice. 67. Scheme and composition of the fuel system of a gas turbine unit operating on heavy fuel.
main fuel system fresh flush water
starting fuel system fuel preparation system
DB– a tank with a demulsifier (polyglycol ether of phenol OP-7); SC– mixing tank; DN– dosing pump; NPV– rinsing water pump; ZTC– spare fuel tank; TPN– fuel transfer pump; PT– fuel heater; P– detergent solution heater; – a tank with a solution of magnesium sulfate; CM– mixer; ABOUT– settling tanks; Sep– separators; alkaline phosphate– slot filters; SF– mesh filters; RCTT– heavy fuel consumable tank; RCLT– light fuel consumable tank; NLT– light fuel pump;
IN– compressed air cylinder; OF– main nozzles; PF– starting nozzle; BN– booster pump; GTN– main fuel pump; BC– bypass valve; K1, K2– taps; SK- emergency brake; ART– automatic fuel distributor; DK– throttle valve.
WITH
A diagram of the fuel system of a gas turbine unit operating on heavy fuel is shown in Fig. 67. Gas turbine engines operating on heavy grades of fuel have two parallel fuel systems: launcher And main.From the tank DB the demulsifier is sent to the mixing tank SC where fresh water is supplied. From the mixing tank, water mixed with a demulsifier (50% OP-7 solution), dosing pump DN 1 is directed to the suction of the flush water pump NPV in an amount of 0.4 ÷ 0.5% of fuel consumption. After heating the wash water with demulsifier in the heater P water in an amount of 5 ÷ 8% of fuel consumption is supplied to the mixing device CM, where it is mixed with fuel supplied by the fuel transfer pump TPN from the reserve fuel tank through the fuel heater. Part of the water is sent to a tank where crystalline magnesium sulfate is loaded MgSO 4 , soluble up to 25% concentration. Addition of solution MgSO 4 in fuel increases the melting point of vanadium pentoxide V 2 O 5 up to about 1100 O WITH (V 2 O 5 contained in heavy fractions of oil and causes severe corrosion in the molten state, called high-temperature vanadium corrosion). The magnesium sulfate solution obtained in the tank is supplied by a dosing pump DN2 into the heavy fuel supply tank, or into the fuel line in front of the injectors. Mixed with rinse water in a mixer CM fuel is sent to settling tanks ABOUT, where purified fuel is separated from water with salts dissolved in it. From the tanks, the fuel enters separators, where it is finally separated from the remaining water.
The separated fuel enters the supply tank RCTT, the capacity of which is determined by the fuel supply for approximately 8 hours of gas turbine operation (two watches). From RCTT washed fuel containing additives is taken through slot filters by a booster pump BN and through strainers it is directed to the suction to the main fuel pump GTN. GTN directs fuel through the next stage of filters to the fuel heater, in which the heating temperature is changed by a regulator that controls the bypass valve BC. Fuel flow to the injectors is regulated by a throttle valve DK, controlled from the control panel and draining part of the fuel back into RCTT. After filtration, the heated fuel is sent to an automatic fuel distributor ART with automatic start, controlling the fuel supply to the main engine injectors OF.
During scheduled stops, the fuel system is flushed with light distillate fuel supplied by the light fuel pump from the light fuel tank through strainers. When flushing with a tap K2 the supply of the main fuel is cut off, which is completely sent to be drained into RCTT through the throttle valve DK. Into the fuel line behind the tap K2 light fuel is supplied, on which the gas turbine unit, previously switched to idle mode, operates for 3–5 minutes, after which the fuel supply is completely stopped, and the fuel line from the tap K2 remains filled with light fuel to the injectors. This ensures easy and reliable subsequent start-up of the gas turbine unit.
During emergency stops, the fuel supply to the injectors is cut off by a stop valve SK, to which pulses from the system are supplied RUZ GTD. In this case, fuel from the pressure line is transferred to drain into RCTT, and the section of the fuel line after the stop valve SK, including ART and injectors OF, blown with compressed air from a cylinder IN.
The light fuel fuel system is also used during start-up when the fuel is out of RCLT fuel pump through tap K1 supplied to the starting injector PF. In the period preceding start-up, the fuel system warms up with the pumps running BN And GTN and fuel heater. In this case, the throttle valve DK is completely closed and all fuel is directed to be discharged into the tank using a stop valve RCTT.
For gas turbine engines that use only light distillate fuel for operation, the system is significantly simplified. In this case, the part of the fuel system intended for flushing and adding additives, as well as part of the light fuel system, is completely eliminated. For such engines, the fuel system contains: consumable tank,filters in front of and behind the gas turbine engine, emergency brake,ART And injectors. In this case, the fuel transfer pump supplies fuel from the reserve tank directly to the supply tank.
Starting system
The gas turbine start-up system is designed to put the installation into operation. This operation requires an external power source (starting motor), which is the main element of the starting system.
In general, the gas turbine starting system contains the following components:
starting motor;
ignition device;
overrunning clutch.
Starting motor designed for the initial spin-up of the turbocompressor unit and at the time of start-up it is attached to the turbocharger rotor. By rotating the turbocharger rotor, the starting engine replaces the still idle gas turbine, providing air supply to the combustion chambers.
The following can be used as starting motors in gas turbine engines:
electric motors direct and alternating current ( electric starters);
turbo starters, which are autonomous low-power gas turbine engines with a free power turbine. In this case, the gas turbine engine is started in two stages: in the first stage, the turbostarter is started with its starting electric motor (usually DC powered by a battery), and in the second, the turbocharger of the main installation is started. This starting pattern is typically used for turbojet and turboprop aircraft engines;
steam turbines (turboexpanders), usually used on ships that have auxiliary steam boilers as part of their auxiliary installation;
pneumatic turbines, operating from the starting compressed air system.
Ignition device designed to ensure flame ignition in combustion chambers and consists of a starting fuel injector and an electric spark plug.
The high-voltage spark plug produces a constant spark discharge throughout the entire period of operation of the starting unit and ignites the fuel of the starting injector. The starting injector flame is directed in such a way as to ensure stable ignition of the main injector fuel. After the main injector fuel is ignited through the flame transfer pipes, the fuel is ignited in the injectors of the remaining combustion chambers. The starting ignition device, having completed its function, is automatically turned off along with the starting fuel system.
Overrunning clutch used to connect the starting motor to the turbocharger, ensure its spin-up and automatically disconnect the starting motor from the gas turbine engine shaft when the turbocharger reaches a given rotation speed.
The gas turbine engine startup process consists of the following periods (Fig. 68):
Period 1 – cold acceleration. The starting engine is connected using an overrunning clutch to the rotor of the turbocompressor unit, which contains a starting combustion chamber with an ignition device. The compressor rotated by the starting engine begins to pump air into the gas-air path of the installation, as a result of which an air flow is created from the compressor through the combustion chambers, turbine flow parts, heat exchangers into the exhaust gas outlet, and its release into the atmosphere. After the air flow supplied by the compressor to the combustion chamber is sufficient to oxidize a minimum amount of fuel, fuel from the starting fuel system begins to be supplied into the combustion chamber through the starting nozzle, which is ignited by the ignition device.
2nd period – support mode . After the fuel is ignited in the combustion chambers, hot air mixed with combustion products begins to enter the gas turbine, which leads to the appearance of increased torque on the turbine shaft, which is added to the torque of the starting engine. From this moment, the acceleration of the turbocharger rotor becomes more intense due to the joint operation of the starting engine and the gas turbine, increasing the air flow in the compressor. At the same time, the consumption of fuel supplied to the combustion chambers increases. With a further increase in the rotation speed of the turbocharger, the turbine takes on the entire compressor load caused by air compression and energy losses due to friction in the bearings. When the compressor rotation speed exceeds the starting motor speed, the overrunning clutch disconnects the starting motor from the turbocharger rotor.
3rd period – hot acceleration . After the starting motor is turned off, further acceleration of the turbocharger rotor is carried out due to the difference in torque created by the gas on the turbine shaft and the air on the compressor shaft (taking into account friction in the bearings). Acceleration continues until the mentioned torque difference becomes equal to zero, which corresponds to the achievement of an equilibrium steady state operation of the turbocharger. Equilibrium can occur at any flow rate of fuel supplied to the combustion chamber exceeding a certain minimum value, below which a steady-state operating mode of the turbocompressor cannot be obtained.
Rice. 68. GTE start-up periods.
PD– starting motor; M– overrunning clutch; Tl– fuel supply; M PD– starting motor torque; M GT– gas turbine torque.
Typically, the starting system of a ship's gas turbine is entrusted with the task of bringing the installation to a mode in which the turbocompressor operates at a certain steady-state speed, and the power developed by the installation on the propulsion turbine shaft is close to zero. This mode is called idle mode - XX.
Controlling the start of a turbocharger usually comes down to the following operations:
Turning on the overrunning clutch;
Turning on the starting motor;
Turning on the ignition device;
Supplying fuel to the combustion chamber.
Typically, the starting motor and ignition device are turned on simultaneously. The moment when fuel begins to be supplied to the combustion chamber is determined by the fuel pressure necessary to obtain proper atomization and the air flow rate supplied by the compressor, at which the gas temperature in front of the gas turbine will not exceed the limit value, and the possibility of surging of the axial compressor will be eliminated.
Lubrication system
The gas turbine engine lubrication system is designed to supply oil to the bearings of turbines and compressors, gearing and remove heat from them.
The following requirements apply to oils used in marine gas turbine units:
high resistance to the formation of sediments and varnish deposits;
high flash point (operating temperature of bearings of compressors and gas turbines can reach 150 ÷ 250 O WITH);
low volatility (boiling point should be at ~50 O WITH above its maximum operating temperature);
GTU oils should serve as a protective medium when the unit is idle and not cause corrosion in the oil system.
For lubrication and cooling of rolling bearings of gas turbine engines, low-viscosity thermally stable oil for marine gas turbines – GOST 10289-79; and for lubrication of gears - turbine oil 46 And turbine with additive – Tp-46 GOST 9972-74.
In gas turbine plants, where the automatic regulation, control and protection system (RUZ GTE) has hydraulic drives of actuators, low-viscosity oil from the gas turbine engine lubrication system is used as a working medium.
The used schemes of lubrication systems for marine and marine gas turbine engines can be divided into two groups:
pressure systems, characterized by a jet supply of oil to the bearings under pressure through special channels in the bearings or through oil nozzles. These systems are used in gas turbine engines with rolling and sliding bearings.
oil mist lubrication systems.
In its turn pressure systems can be divided:
on forced lubrication systems in which lubricant is supplied to all components from the oil pump (the oil pump is often mounted on the gas turbine engine and receives rotation from the compressor rotor through the drive box);
gravity lubrication systems, in which lubricant is supplied from a tank located at level 10 ÷ 12 m above the gas turbine engine to ensure the required oil pressure. The oil pump in this case only returns oil from the waste tank to the gravity tank. This scheme is acceptable only for transport fleet vessels, where the size of the engine rooms allows the placement of elements of a gravity lubrication system. Gravity lubrication systems are also used as backup lubrication systems. The volume of gravity tanks is selected taking into account the 10 ÷ 15 minute operation of the gas turbine engine, during which malfunctions in the operation of the main lubrication system can be eliminated, or a command can be given to turn off the fuel supply to the combustion chambers for an emergency stop of the gas turbine engine on the rundown.
The lubrication system of a marine gas turbine unit consists of the following main elements (Fig. 69): main And backup oil pumps;filters;heaters And oil coolers;oil tanks(consumable, spare, dirty oil, gravity lubrication systems for gravity lubrication systems); oil separators;oil transfer pump;instrumentation and pipelines.
Rice. 69. Diagram of the oil system of a gas turbine unit (forced and gravity systems).
forced lubrication pipelines;
pipelines related to the gravity system;
drain pipelines.
RMC– consumable oil tank; Gr.C– gravity tank;
TsZM– spare oil tank; CGM– used (dirty) oil tank;
OMN– main oil pump; RMN– backup oil pump;
MF– magnetic filter; GMF– main oil filters; MO– oil cooler; ZF– protective filters; MPN– oil transfer pump; MSep. – separator.
GTE lubrication systems must provide protection against a drop in oil pressure. If the oil pressure drops, the backup oil pump should automatically come into operation, or the system should switch to gravity lubrication. If the pressure in the lubrication system continues to drop (which may indicate a rupture in the oil pressure line), the system sends a signal to the fuel system stop valve, which turns off the fuel supply to the engine injectors.Oil transfer pump designed for pumping used oil from the RMC into the used oil tank, to replenish the loss of oil in the system, or completely replace the oil by pumping it from the CMP to the RMC.
Oil separator used to remove water and mechanical impurities from oil. In the cold season, it is possible to pump the oil with a separator through oil heater(not shown in the diagram). The oil in the RMC can also be heated from a system of coils through which steam from the auxiliary steam boiler is passed.
Prompting system
The venting system is designed to select the oil-air mixture from the oil cavities of gas turbine engine bearings, separate the oil from the air and then return the oil to the gas turbine engine lubrication system.
The breather system includes:
pipelines connecting the oil cavities of the bearings with the settling tank;
settling tank(tank), where oil droplets are released and deposited on the walls; Often the role of a settling tank is played by the waste tank of the oil system;
oil separators (centrifuges), completing the process of separating the oil-air mixture into its component parts; they are driven from a drive box connected to the shaft of the gas turbine engine turbocharger via a gearbox.
Reverse system
The gas turbine engine reverse system is designed to change the direction of rotation of the propulsion shaft to the opposite. On ships and ships with gas turbine engines, the following means can be used to ensure reverse:
special reverse motors. This reverse method is often used on hydrofoil ships - SPK. In this case, the reverse engines have their own independent propulsors, located in the non-displacement position of the SVC above the water surface, and immersed in the water when the vessel moves in the displacement position;
electric transmission. This reverse method is applicable on those ships that use electric propulsion (the gas turbine engine operates on an electric generator that transmits electricity to the propulsion motor);
reverse gear. In this case, the gas turbine engine transmits rotation to a gear, the design of which allows you to change the direction of rotation of the output shaft connected to the propeller, without changing the direction of rotation of the shaft of the gas turbine engine itself. The most commonly used are hydraulic reversible transmissions, which include a fluid coupling and a torque converter, and mechanical transmissions (reversible gearboxes);
reversible propulsors(usually adjustable pitch propellers). Reverse is carried out by shifting the rotating propeller blades from the forward position to the reverse position. In this case, the direction of rotation of the propulsion shaft does not change to the opposite;
reversible gas turbine engines, capable of changing the direction of rotation of the propulsion gas turbine shaft.
The use of reversible ship gas turbine engines is associated with the use of separate turbines(steps) reverse–TZH, or special reversible centripetal turbines.
Reversible axial turbines are performed in two possible options (Fig. 70):
as separate reverse turbine, located on a separate disk, rigidly connected to the rotor of the forward propulsion turbine (Fig. 70. A);
as a combined location on one disk forward and reverse steps(use of two-tier blades - Fig. 70. b).
An important element of the reverse system in reversible axial turbines is gas distribution body, with the help of which gas after the compressor turbine can be directed either into the flow part of the forward turbine or into the flow part of the reverse turbine.
When reversing, the propulsion turbine rotor is first braked by gas supplied to the flow part of the reverse turbine, which rotates with the edges of the working blades forward. This mode of engine operation is called “countergas mode”. After the propulsion turbine rotor has completely stopped, the gas distribution body directs the entire gas flow to the reverse turbine.
Rice. 70. Diagrams of the relative arrangement of the flow parts of the TPC and TPC
A– with TZH, performed on a separate disk;
b– with TZH, made in the form of a second tier of blades.
1 – compressor turbine; 2 – forward turbine; 3 – reverse turbine;
4 – gas distribution body; 5 – second tier of TZH blades.
The movements of the gas distribution body must be interconnected with the supply of fuel to the injectors. When reversing a gas turbine engine, the following sequence of operations must be observed:
Reducing the fuel supply to the injectors to idle flow;
Simultaneous relocation of the gas distribution body that transfers gas to the TPH, with a gradual reduction in gas flow to zero supplied to the flow part of the TPH;
Increasing the fuel supply to the injectors to a value corresponding to the specified reverse mode after the gas distribution body has been completely repositioned.
The main disadvantage of the reverse methods described above is the presence of large ventilation losses due to the idle rotation of idle stages (in forward motion the TLC stages rotate idle, in reverse - TPC). The idle rotation of turbine stages in a dense air or gas environment consumes a significant part of the engine energy. These losses for gas turbine units can reach 3 ÷ 4% of the gas turbine engine power for an idle TPC, and an even greater value for an idle TPC. In addition, when the turbine rotates idle, its elements become very hot, which entails additional costs for its cooling. When using double-deck blades, an additional challenge is ensuring the strength of the tall blades at high turbine rotor speeds.
Reversible centripetal turbines
This reverse method is characterized by the fact that when it is used, there are no ventilation losses both in the forward and astern motion of the vessel. This is due to the fact that with a radial arrangement of the blades, the same impeller can be used to operate in both forward and reverse motion. In this case, the reverse is carried out by turning the guide vanes of the nozzle rim (Fig. 71).
Rice. 71. Scheme of a reversible centripetal turbine.
1 – nozzle rim with rotating blades; 2 – impeller with radial blades;
3 – blades in the PH position;
4 – blades in position 3X.
Despite their positive properties, reversible centripetal turbines have not yet become widespread in ship gas turbines due to the difficulty of arranging flow parts consisting of several centripetal turbines located in series and the difficulty of combining centripetal and axial stages in one housing. At the same time, the rational use of reversible centripetal turbines involves a combination of axial turbines as drive turbines for compressors with centripetal propulsion turbines.Cooling systems for gas turbine units
Cooling of gas turbine parts exposed to high temperatures is used to achieve the temperature level and temperature differences that ensure reliable operation of the gas turbine engine in all modes.
Cooling systems for structural elements of gas turbine plants include:
system sea water cooling gas turbine equipment;
system cooling fresh water structural units of gas turbine plants;
system air cooling structural units of gas turbine plants.
Sea water cooling system GTU equipment (Fig. 72) is designed to remove heat from oil coolers, air coolers and a fresh water cooler (in the case of using a fresh water cooling system for the structural components of the GTU). The cooling system is made both with forced water supply - using a centrifugal or axial type pump, and self-flowing. In self-flowing systems, the cooling seawater pump is used only in low speed, stop or reverse modes, when a pressure sufficient to overcome the hydraulic resistance of the cooling path cannot be created in the inlet pipe.
Rice. 72. Diagram of water cooling systems of a gas turbine unit.
RCPV– fresh water supply tank; HE– main pump of the cooling circuit; RN– backup cooling circuit pump; F– filters; 1 – supply of cooling water to the lower part of the housing; 2 – supply of cooling water to the upper part of the housing; 3 – tap hot water from the bottom of the body; 4 – hot water drainage from the top of the housing; OPV– fresh water cooler; MO– oil cooler;
IN– air cooler; EPV– intake of sea water; FZV– sea water filter; CN– sea water circulation pump; SZV– draining sea water;
M- oil; IN- air.
Fresh water cooling system (Fig. 72) is performed only for fixed parts (compressor housings, gas turbines, exhaust and volute pipes, etc.) of a non-direct-flow gas turbine engine.
Air cooling systems turbine housings (Fig. 73) are used in direct-flow engines with axial movement of air and gas, the housing of which has a simple cylindrical shape. Cooling air enters the annular space between the outer casing and the turbine housings, washes the housings and is discharged into the gas duct due to the ejection action of the gas jet. The cooling medium can be used: engine room air, atmospheric air or air taken from one of the compressor stages.
ABOUT 
cooling of flow parts turbines: nozzles, rotor blades and rotor disks, is carried out by air taken from one of the compressor stages.
The most common cooling schemes for flow elements include open outdoor And open internal cooling systems.
Rice. 73. Scheme of air cooling of the gas turbine engine housing.
UPG– recovery steam generator;
IN– cooling air pipeline;
G- gas duct.
Open external cooling systems (partial, screen and jet) reduce the temperature of the metal parts of the flow part by 50 ÷ 70 O WITH. Air through the holes in the rotor is supplied to the gap between the rotor and the guide vane through channels, blowing the top of the guide vane, the root of the rotor blades, and mixes with the gas flow in the flow part of the turbine (Fig. 74. A).With internal air cooling, air enters the working blade through special holes in its root. Depending on the design of the cooled blades, air passes through channels inside the blade (Fig. 74. b-V), or through the gap between the deflector (inner insert) and the outer shell of the blade (Fig. 74. G), and is then thrown into the flow part through holes in the end part or trailing edge, where it is mixed with the gas flow. The use of internal cooling of the blades makes it possible to reduce the metal temperature of the working blades by 150 ÷ 300 O WITH.
Rice. 74. Methods of cooling turbine blades
A– external open system; b, V, G– internal open cooling systems.
Cooling of gas turbine disks and rotors is carried out using cyclic air and can occur in several ways:radial airflow when air is supplied through the holes in the rotor to the root part of the disk and moves to its periphery;
jet cooling, in which streams of air blow directly onto the rim of the disc;
blowing air through the gaps of the blade shanks;
barrier cooling, in which a protective air film is created between the gases and the surface of the disk;
combined method, combining several of the above.
Regulation, control and protection system (RUZ GTD )
During the operation of a ship's gas turbine unit, frequent changes in the vessel's strokes and operation of the installation in variable modes are possible. When operating a gas turbine engine in all operating modes, it is necessary to ensure:
Possibly more economical operation of the installation;
the temperature of the gases in front of the gas turbine, not exceeding what is permissible under the conditions of heat resistance of the materials of the flow part;
stable fuel combustion process without flame failure;
non-surge operating mode of an axial compressor.
The fulfillment of all these conditions during the operation of gas turbine engines is ensured by regulation, control and protection systems - RUZ GTE, which are assigned the following functions:
Implementation and maintenance of all operational, stationary and transient modes of gas turbine plants with a minimum number of impacts on manual controls.
Conversion and transmission of impulses from manual controls to technical means that control the operating modes of the gas turbine unit and service it.
Elimination of the possibility of incorrect manipulations by maintenance personnel when controlling the installation in all modes.
Taking the installation out of operation or limiting the possibility of its operation without the intervention of maintenance personnel in modes that are accompanied by violations of the normal operating conditions of any structural unit or component of the installation.
Providing maintenance personnel with the information necessary to monitor the operating conditions of the gas turbine engine and installation elements and signaling violations of the normal operating conditions of their operation.
The power received at the gas turbine engine output flange depends on the fuel flow supplied to the combustion chambers, so the control system is usually combined with the fuel system of the engine itself. The power of a gas turbine engine can be changed by influencing the element that controls the fuel supply, and the nature of the effect depends on the type of fuel injectors installed on the engine (adjustable or unregulated) and the method of changing the performance of the adjustable injectors.
Depending on how the regulation process is carried out, there are two main ways to regulate the power of a gas turbine engine: quality And quantitative.
Quality regulation is produced by changing the gas temperature in front of the gas turbine with a small change in the flow of forced air. In this case, to reduce the load, the amount of fuel supplied to the combustion chambers is reduced. At the same time, the excess air coefficient increases and the temperature of the gases in front of the gas turbine decreases, which leads to a decrease in the heat drop generated by the turbine and a decrease in the power of the installation. High-quality regulation is the simplest, but leads to a significant decrease in efficiency when the engine operating mode deviates from the design one.
Quantitative regulation is carried out by changing the compressor rotation speed, which in turn causes a change in air flow and the degree of pressure increase. With this control method, the gas temperatures in front of the gas turbine change sharply, which causes maximum thermal stress in the parts of the flow path.
In real gas turbine plants, it is extremely rare to use any separate method of power control, but usually use mixed regulation , combining both described methods. In all cases, the change in useful power is ultimately achieved by changing the consumption of burned fuel.
Using unregulated nozzles changing the fuel flow into the combustion chambers can be done using a variable-displacement pump, or by changing the drain of part of the fuel from the pressure of the fuel pump into the fuel supply tank. Ways to change fuel consumption in adjustable nozzles will be discussed in the second part of the manual when considering control systems for steam boilers.
In gas turbine plants, the most common way to regulate the fuel flow entering the combustion chambers is the use of multi-stage or multi-channel injectors. The use of multi-channel injectors makes it possible to significantly increase the range of changes in fuel supply with a limited change in fuel pressure behind the fuel pump. The object of regulation in such systems is the throttle valve (Fig. 75).
Rice. 75. Fuel supply control diagram when using multi-channel injectors.
TN– variable displacement fuel pump; Sh– fuel pump washer; T– fuel pump supply rod; RZ– distribution spool (included in ART); P– piston of the distribution valve; F- fuel burner; R– throttle valve control handle – “throttle sector”; DK– throttle valve; 1 TO– fuel supply to the first channel of the injectors; 2K– fuel supply to the second channel of the injectors; 1 – suction pipe of the fuel pump; 2 – pressure pipe of the fuel pump; 3 – drain fuel into the tank.
The amount of fuel supplied to the engine combustion chambers (Fig. 75) is determined by the fuel pressure in the cavity of the distribution valve. With the throttle valve fully open, controlled regulation system, the fuel pressure supplied by the fuel pump is not enough to move the spring-loaded piston. The piston is in the extreme left position and blocks with its body the holes supplying fuel to the first and second channels of the injectors. In this case, all the fuel that enters the spool cavity is drained through the drain line into the fuel supply tank. As the throttle is closed, the pressure in the spool cavity gradually increases, and the piston begins to move to the extreme right position, first opening the fuel supply hole into the first injector channels (shown in the figure), and with further closing of the spool, into the second injector channels. Control of the gas turbine engine in the case under consideration comes down to controlling the position of the throttle valve.
The control systems of gas turbine engines operating on a rotary propeller are more complex. The same power can be obtained big amount various combinations of fuel consumption and rotor blade rotation angle. From these combinations, as a rule, the one that ensures maximum efficiency of the installation is selected (i.e., each angle of rotation of the propeller blades must correspond to a certain fuel consumption).
Typically, the following parameters of gas turbine engine operation are subject to regulation:
The gas turbine engine protection system is designed to limit engine power or ensure its emergency shutdown in the event of emergency situations.
Depending on the degree of influence on engine operation, protective devices are divided into restrictive And limit.
Limiting safety devices are triggered in the case when violations of the normal operating conditions of the gas turbine unit are of a short-term nature and (or) when normal conditions can be restored by influencing special devices that eliminate the cause of the disruption. Restrictive protective devices include:
anti-surge protection, preventing the occurrence of compressor surge by influencing anti-surge devices when operating points approach the boundaries of surge zones;
protection against theft of rotors turbomachines, preventing an increase in rotor speed above the calculated one by reducing the fuel consumption supplied to the combustion chambers; This type of protection limits the rotation speed of turbomachines in the range of 100 ÷ 110% compared to the rated load mode. With a further increase in rotation speed, a limiting protective device is activated, completely stopping the supply of fuel to the combustion chambers;
Limit protective devices are used in cases where violations of the normal operating conditions of a gas turbine unit are of a long-term nature and when these violations can lead to plant accidents. For ultimate protection use:
rotor speed protectionpropulsion turbine(rotor theft protection);
compressor rotor speed protection;
oil pressure reduction protection in the gas turbine engine lubrication system.
All limiting protective devices generate an impulse to the stop valve of the fuel system (see Fig. 67), which instantly turns off the fuel supply to the engine injectors.
Air intake and gas exhaust devices
Air intake devices Marine gas turbine engines are designed to supply air to engines, protect gas turbine engines from foreign objects, exhaust gases, splashes and salts of sea water, erosively hazardous particles and protect compressor inlet devices from icing.
On displacement vessels, the most common above-deck air intake devices are shaft type, which may include the following elements (Fig. 76):
intake pipe(P), designed to take air from the atmosphere and form an air flow. The inlet pipes are located in that part of the vessel where the least amount of salts and splashes can enter the air flow sea water, exhaust gases, dust and other foreign objects;
filters(F), providing cleaning of the air entering the compressor suction;
mine(Sh). In order to reduce noise levels, the inside of the shaft is often lined with a sound-absorbing coating ( Salary);
noise suppression device(GSh), designed to reduce the noise level of the air flow; The main source of noise in a gas turbine engine is the suction part of the compressor, in which noise occurs when the air flow interacts with a stationary inlet guide vane and the subsequent rapidly rotating first row of rotor blades;
Rice. 76. Mine diagram
air intake
GTE devices.
cochlea, designed to shape the air flow entering the compressor.
Above-deck air intake devices are sometimes used to supply air to the engine room, from where it is taken by one or more gas turbine engines.
Gas exhaust devices Marine gas turbine engines are used to remove exhaust gases from the engine with minimal energy losses and, in addition, allow:
reduce noise level from the exhaust side:
eject cooling air from under the engine casing (Fig. 73);
reduce the gas temperature behind the turbine to the required level;
provide gas supply to heat recovery boilers.
HVUs consist of various (depending on the type and placement of the engine) combinations of the following elements: post-turbine diffuser; cochlear tube; extension pipes; swivel elbow; ejector traction amplifier; jet nozzle; cooling and noise reduction systems.
When the gas turbine engine is placed in close proximity to the upper deck, the gas turbine engines are made in the form of jet nozzles with an exit to the stern of the vessel (for high-speed vessels). In this case, the residual part of the kinetic energy of the gases is converted into additional jet thrust.
When a gas turbine engine is placed in the ship's main building at a considerable distance from the upper deck, the gas turbine engine must contain an exhaust pipe that turns the gas flow by 90 degrees.
The invention relates to the field of energy, in particular to methods for starting and supplying gas pumping units, and can be used when starting up any gas turbine units. The method of starting a power gas turbine installation includes three stages. At the first and second stages, the rigidly connected turbocharger rotors are spun up by an external starting device, for example an expander, rigidly connected through an automatic coupling to the turbocharger shaft. The turbocharger contains a compressor, a turbine and a combustion chamber equipped with a fuel control valve, closed at the first stage of start-up and slightly open at the second. Subsequent disconnection of the rigidly connected compressor and turbine rotors from the starting device when they reach the design speed and bringing them to operating speed in the third stage by increasing the flow rate and pressure of the fuel gas. At the outlet of the axial compressor, a relief valve is installed, connected to the inlet of the combustion chamber. The start-up of the gas turbine unit in the first and second stages is carried out with the relief valve open, and before disconnecting the starting device, the relief valve is closed. The invention is aimed at reducing the power imbalance caused by a drop in the turbine rotor speed and a temperature jump in front of it, at the moment the starting device is turned off when starting a gas turbine unit. 2 ill.
The invention relates to the field of energy, and more precisely to methods for starting and supplying gas turbine units (GTU) using gaseous fuel.
Starting up a gas turbine unit is the most critical stage in organizing the operation of a compressor station. As the rotors of the gas turbine start to move, dynamic loads begin to increase, and thermal stresses arise in the components and parts due to the heating of the gas turbine. An increase in temperature leads to a change in the linear dimensions of the blades and disks, a change in the gaps in the flow part, and thermal expansion of pipelines. When starting the rotor at the first moment, a stable hydraulic wedge in the lubrication system is not ensured. The process of switching the rotors from working pads to installation pads is underway. The gas turbine compressor is close to operating in the surge zone. The supercharger carries out a large flow of gas at a low compression ratio, which leads to high speeds, especially of the recirculation pipelines, which causes their vibration. During the startup process, before reaching the “idle gas” mode, the shaft lines of some types of gas turbine plants pass through revolutions that coincide with the natural frequency of oscillations, i.e. through resonant turns.
The gas turbine unit is started using starting devices. For gas pumping units (GPU), turboexpanders are used, operating mainly on differential pressure natural gas, which is pre-cleaned and reduced to the required pressure. Turboexpanders are installed on most stationary and some aircraft GPUs. Sometimes compressed air is used as a working fluid.
In addition to the turboexpander, electric starters are widely used, which are used on ship GPUs. A number of units are equipped with a hydraulic starting system. The power of starting devices is 0.3-3.0% of the GPU power, depending on the type of GPU - aviation or stationary.
Let's consider a typical algorithm for automatically starting a stationary gas pumping unit. When starting up a gas compressor unit, three stages can be distinguished. At the first stage, spinning up the rotor of the axial compressor and turbine high pressure occurs only due to the operation of the starting device.
At the second stage, the turbocharger rotor is spun up jointly by the turboexpander and the turbine. When the turbocharger speed reaches sufficient to ignite the mixture at 400-1000 rpm, the ignition system is turned on and gas is supplied to the pilot burner. Normal ignition is indicated by a sensor - a photo relay. Approximately 1-2 minutes after the temperature reaches approximately 150-200°C, the first warm-up stage ends, the control valve opens by about 5% and the second warm-up stage begins, which lasts 10 minutes. Then there is a gradual increase in the speed of the high-pressure turbine due to the opening of the gas control valve. When the speed reaches approximately 50% of the nominal value, the turbine enters the “self-propelled” mode. When the turboexpander clutch disengages, the second stage of rotor spin-up ends. At this moment, to avoid a dip in the turbocharger rotor speed, the fuel control valve is sharply opened by 2-3%.
At the third stage, the turbocharger rotor is further accelerated by gradually increasing the gas supply to the combustion chamber. At the same time, the anti-surge valves of the axial compressor are closed, the turbo unit switches to work from the starting pumps to the main ones, which are driven into rotation by the rotors of the unit. (A.N. Kozachenko. Operation of compressor stations of main gas pipelines. - M.: Publishing House "Oil and Gas", 1999, p. 459).
The disadvantages of the known technical solution lie in the jump in the temperature of the combustion products in the turbine upon completion of the second stage of start-up. This leads to significant temperature stresses in the turbine components, to interference of the rotor blades with the sealing elements of the radial clearances and, as a consequence, to a decrease in the power life and efficiency of the gas turbine unit.
There are known methods for starting a gas turbine unit with a free power turbine by spinning up the rotor of the gas turbine compressor using external starting motors (electric motors, steam turbines, pneumatic starters, gas turbine units). (Stationary gas turbine units: Handbook. / Ed. L.V. Arsenyev and V.G. Tyryshkin. - L.: Mashinostroenie, 1989, p. 376-377).
The closest technical solution to the proposed invention is the method of starting and supplying gas to a power plant according to RF patent No. 2186224, which includes spinning up the rigidly coupled rotors of a turbocharger and a fuel gas booster compressor with an external starting engine (first stage).
After the connected rotors of the booster compressor and turbocharger reach starting speed, the fuel gas control valve is opened, fuel gas is supplied to the combustion chamber and ignited with an igniter. The combustion products pass through the gas turbine of the gas turbine, spinning the above-mentioned associated rotors. As the connected rotors spin up and the so-called “self-propelled” mode is reached, the rigidly coupled rotors of the turbocharger and the fuel gas booster compressor are disconnected from the starting engine when they reach the design speed (second stage), and the degree of opening of the fuel gas control valve is increased, which increases the rotor speed turbocharger. Further increase to operating speed is achieved by increasing the flow rate and pressure of fuel gas (third stage).
This technical solution also has the disadvantages described above associated with a temperature jump when the starting device is disconnected.
The technical objective of the proposed invention is to develop a method for starting a gas turbine unit that makes it possible to reduce the power imbalance when the starting device is turned off without increasing fuel consumption when starting the gas turbine unit. This power imbalance manifests itself in a drop in the turbine shaft speed with a simultaneous significant jump in temperature in front of it.
The technical result is achieved due to the fact that in a known device containing an external starting device (turboexpander), rigidly connected through an automatic coupling to the shaft of a turbocharger, including a compressor, a turbine and a combustion chamber equipped with a fuel control valve, which is closed at the first stage of start-up , and at the second - it opens slightly, with an increase in the degree of its opening at the third stage of start-up, changes have been made to change the gas turbine start-up algorithm, namely;
At the outlet of the axial compressor, a relief valve is installed, connected to the inlet of the combustion chamber:
The start-up of the gas turbine unit in the first and second stages is carried out with the relief valve open;
When the “self-propelled” mode is reached, the relief valve is closed before turning off the expander.
As a result of the additional air flow through the turbine, the power imbalance that occurs when the expander is turned off is reduced, while the increase in air flow through the combustion chamber when the fuel control valve (FVR) is blown leads to a significant reduction in the temperature jump in front of the turbo engine.
Figure 1 shows a diagram that implements the proposed method of starting a gas turbine, and figure 2 shows a schedule for starting a gas turbine according to the prototype and according to the proposed invention.
The main elements of the circuit are: 1 - external starting motor (expander); 2 - release clutch; 3 - axial compressor; 4 - fuel gas control valve; 5 - drive gas turbine; 6 - relief valve; 7 - combustion chamber; 8 - power gas turbine; 9 - load; 10 - automatic control system (ACS).
The proposed method of starting a gas turbine is carried out automatically according to ACS commands as follows. An external starting motor 1 spins the rigidly connected shafts of the axial compressor 3 and the drive gas turbine 5 through the release clutch 2. The fuel gas control valve 4 is closed, and the relief valve 6 is open. The air, passing through the combustion chamber 7, enters the drive turbine, spinning the above-mentioned communication shafts due to gas expansion. When the connected rotors reach the starting speed, the fuel control valve 4 is slightly opened, and when the “self-propelled” mode is reached, the relief valve is closed, while the release clutch 2 automatically disconnects the rotor of the starting motor 1 from the connected rotors of the axial compressor 3 and the drive gas turbine 5, and the opening degree the fuel control valve is increased.
The considered starting method can be applied to any gas turbine plant that uses a starting turboexpander.
Figure 2 shows the starting characteristics of the GTK-10 gas turbine unit with the starting algorithm according to the prototype (known) and according to the proposed algorithm.
From the analysis of the graphs in Fig. 2, we can conclude that after turning off the starting turboexpander (at a rotation speed of 2600-2800 rpm - “self-propelled” mode), the dip in the turbocharger rotor speed decreased from 300 rpm to 50 rpm , i.e. 6 times, and the jump in the temperature of combustion products decreased by 50°C, i.e. twice.
Thus, the proposed algorithm for starting a gas turbine allows us to significantly reduce dips in the turbocompressor shaft speed and a jump in the temperature of the combustion products in the turbine, which, in turn, ensures an increase in the service life of the gas turbine and a decrease in fuel consumption.
The implementation of the proposed algorithm for starting a gas turbine unit was carried out in July 2007 on the gas pumping unit (GPU) GTNR-16 and is planned for implementation on the GPU GTK-10.
A method of starting a power gas turbine installation, which includes three stages, and in the first and second stages, the rigidly coupled rotors of the turbocharger are spun up by an external starting device, for example, an expander, rigidly connected through an automatic coupling to the shaft of the turbocharger, including a compressor, a turbine and a combustion chamber equipped with fuel. - a control valve, closed at the first stage of start-up and slightly open at the second, disconnecting the rigidly connected compressor and turbine rotors from the starting device when they reach the design speed and bringing them to operating speed at the third stage by increasing the flow rate and pressure of the fuel gas, characterized in that that at the outlet of the axial compressor, a relief valve is installed, connected to the inlet of the combustion chamber, and the start-up of the gas turbine unit in the first and second stages is carried out with the relief valve open, and before disconnecting the starting device, the relief valve is closed.
Chapter 11 Features of starting a gas turbine unit
Static frequency converter (SFC)
General information
A static frequency converter (SFC) is used to spin the gas turbine shaft by supplying a variable frequency, reduced voltage, and reduced excitation power to the generator.
The gas turbine startup procedure is completely automatic. The generator is used in "motor" mode and during the starting cycle accelerates the shaft to a certain percentage of the rated speed.
Once this certain percentage of the rated speed is reached, the CFC is switched off and the gas turbine then accelerates on its own to 100% of the rated speed.
At 100% of rated speed, the generator is producing rated voltage and is ready to perform the synchronization sequence with the power system.
In addition to the starting function, the VHF is also used to accelerate the unit to a certain speed during the flushing cycle.
Starting system equipment
The starting system equipment is located in a housing, which is usually located adjacent to the generator compartment. The enclosure is suitable for outdoor installation in the specified site climate conditions. Heating, air conditioning, lighting, and auxiliary power outlets are provided to protect equipment located inside the enclosure.
The main equipment components of this system are listed below:
One (1) monitoring and control bay
One (1) DC link reactor
One (1) off-base switch on unit side
· Measuring and protective devices (voltage transformers VT and current transformers CT)
One (1) circuit breaker on the transformer side of the IRF
Basic operating principle
The starting static voltage converter is powered by a voltage conversion transformer.
The starting frequency converter is an indirect frequency converter that operates as an inverter with natural commutation; it consists of three main components:
· One (1) thyristor bridge rectifier (network bridge) powered by a voltage conversion transformer.
· One (1) thyristor inverter bridge (unit bridge) connected to the generator via a disconnect switch.
· One (1) DC link intermediate circuit whose reactor provides isolation between the network and unit bridges.
The proposed system includes a pulse generator for triggering. Asynchronous control is performed entirely by processing the signals taken from the synchronous starting motor using voltage transformers.
When operating in motor mode, the generator rotor winding is supplied with direct current from a system that includes:
Thyristor bridge used to operate in generator mode
· An automatic system that supplies direct current to the rotor field winding using slip rings and brushes. The brushes are pressed against the rings at the beginning of the start sequence or wash cycle and lifted off the rings at the end of the sequence or cycle.
Functions
The starting frequency converter is designed to perform the following functions:
· Starting the turbine: The turning device creates an initial turning moment on the shaft axis; then the HRC accelerates the gas turbine shaft to self-propelled speed.
· Flushing (with compressor disassembly): During this sequence, the CFC rotates the gas turbine at a low, constant speed.
Description and design elements
The complete equipment is installed inside an air-conditioned enclosure suitable for outdoor installation.
Inside the cabinet we can roughly distinguish two different groups of equipment:
· Power equipment
Auxiliary and control equipment
Powerequipment
The smoothing reactor of the DC link and the power thyristor module are the “power” units of the frequency converter.
The power thyristor module of the network/unit includes the thyristor arms of the bridge, their protective systems, connections and measuring instruments (current transformers, voltage transformers).
The DC link smoothing reactor is usually made with an air-cooled iron core equipped with a sensor maximum temperature. The reactor performs the function of limiting current waves in the intermediate continuous current circuit.
To connect the IF circuit and the generator stator, there is one three-pole disconnect switch with a motor drive. The disconnector is equipped with a grounding device on the HRC side.
Inside the equipment cabinet there is one three-pole circuit breaker installed to connect the IF circuit to the IF transformer.
Auxiliary and control equipment
The control and protection functions of the frequency converter are performed using all the necessary commands, signals, alarms, instruments and auxiliary circuits that are provided in the unit. Auxiliary circuits are made up of converters, relay logic, PLC circuits, and interface boards.
The control system performs the following main functions:
· Line-side constant frequency converter phase shifter
· Phase shifter of the variable frequency converter on the unit side (in two operating modes: pulse mode and natural switching mode)
Speed regulator with internal current regulator loop
Variable frequency converter starting angle control
· Operating logic (PLC)
· Converter interface (pulse generator for opening thyristors, polling signals from voltage and current transformers)
Field winding interface
· Diagnostics and user interface.
Technical characteristics of the frequency converter - general parameters
· Applicable standards: IEC, IEEE
Rated starting power: 2250 kW
· Rectifier:
Quantity: 1
Input voltage at idle: 1550 Volts
· Inverter:
Quantity: 1
Output voltage: 0 – 1450 V
· Smoothing reactor
Quantity: 1
Type: Iron Core Dry Reactor
· Control type: Microprocessor
Installation type: in container
Fuel system. The fuel for marine gas turbines is fuel oil, diesel fuel and kerosene. During start-up and shutdown, light, less viscous fuel is used, which eliminates filter clogging and injector coking. To improve the combustion process of heavy grades of fuel (fuel oil) and eliminate the formation of deposits in the gas path of the turbine, special additives are added to the fuel.
In Fig. Figure 118 shows a schematic diagram of the fuel system of a gas turbine unit. During the startup period, the starting electric pump 17 supplies starting fuel from the tank 1 through the filter rough cleaning 18 to the starting injector 14. Upon achieving stable combustion of the starting injector, the main fuel pump 8 is switched on with valve 6 closed and valve 9 open. The main fuel pump directs the starting fuel to the fuel unit 10 working injectors 13. Before entering the injectors, the fuel passes a strainer 11 and stop valve 12. Fuel transfer pump 16 supplies starting fuel through fuel heater 15 and strainer 7 to the main fuel pump.
At the same time, the main fuel system heats the fuel oil to the required temperature (about 393° K) to reduce its viscosity; at the same time, the recirculation circuit of the main fuel operates: fuel oil from the supply tank2 , having passed through the coarse slot filters 3, the booster pump 4, through the heater 5 and tap 6, returns back to the supply tank. When the fuel oil reaches the required temperature, valve 6 is moved to the position of supplying fuel oil to the working nozzles 13, and valve 9 is closed, and the starting fuel is pumped back to the spare tank1 .
Oil system. The oil system of ship gas turbines, as well as steam turbines, can be circulation or gravity pressure. The lubricating oils of marine gas turbine plants are subject to more stringent requirements than the oils of steam turbine plants. Oils must not only have high lubricating, anti-wear and anti-corrosion properties, but also be resistant to deposit formation and have high temperature flashes, not lower than 473° K, since in some gas turbines the bearing temperature reaches 423-443° K.
Cooling system. The cooling system of gas turbines can be water or air.
In Fig. 119 shows a schematic diagram of the air-water cooling of the gas turbine unit of the Paris Commune ship. The high-pressure turbine housing 2 is cooled with distilled water supplied by a centrifugal pump 5 through a paired filter 6. After cooling the HPT housing, distilled water is supplied through a surface water cooler7 returns to tank 4. Cooling of low pressure turbine disks1 produced by air taken from the intermediate stage of the compressor3 , and the cooling of the high-pressure turbine disk 2 is done by air taken from the last stage of the compressor.
Reversing devices of gas turbine units. Reverse in a gas turbine unit can be carried out using TLC, adjustable pitch propellers (CPC), hydraulic reversing devices, power transmission and reversible planetary gears. However, in tube-compressor gas turbine plants, due to the significant final gas pressure (about 1 bar), and consequently the increase in power losses due to rotation of reverse turbines and the complexity of the design of the switching device, TZH has not found wide application. In a gas turbine unit with LPGG, the gas volumetric flow rate and its temperature in front of the turbine are significantly lower than in turbocompressor gas turbine units, and this reduces the size of the switching elements. To implement reverse in a gas turbine unit with SGNG, TZH is used.
The use of a control propeller increases the maneuverability of the vessel, simplifies the gas turbine unit and improves its operation in off-design modes.
Hydroreversible devices and reversible planetary gears are compact, light weight and have good maneuverability. This type of reversing devices for high-power installations is in the development stage.
Electric transmission, while having good maneuverability, has significant (for ships) weight and dimensions and low efficiency.
Control and protection system . This system is designed: to control a gas turbine unit during startup, maneuvers and shutdown; to prevent emergency conditions of the installation and protect it when the maximum rotation speed or axial displacement of the installation rotors is exceeded, the oil and fresh water pressure in the lubrication and cooling systems drops below the permissible values, changes in the operating temperature of the gas flow (temperature increase, flame failure in the combustion chamber).
The control of the gas turbine unit at startup is carried out by sequentially turning on and off the starting devices, and in operating modes by changing the fuel supply to the combustion chamber, opening the gas bypass valves into the exhaust gas duct and opening the dampers of the compressor anti-surge device. All these operations are controlled remotely from the control panel or from the bridge. If the automatic remote control fails, manual control is provided. The protection system is equipped with an emergency warning and information alarm, when triggered, the lights light up and the sound signal turns on.
In Fig. Figure 120 shows a simplified control diagram for a gas turbine unit with a rotary propeller. To the combustion chamber injectors 2 purified heavy fuel is supplied by the fuel pump 12 through the main regulatory authority 9, which determines the operating mode of the installation. Relocation of the Regulatory Authority 9 carried out from the flywheel rotation control station 5 through the cam 6 and a spring 4. A constant drop in oil pressure across the regulating body is maintained by regulator 3, and its speed of movement is limited by throttle response regulator 11. The supply of starting diesel fuel is carried out by the supply regulator 10. Servomotor 1 and spool 13 provide repositioning of the rotary propeller blades. The angle of rotation of the propeller blades is set by turning the flywheel 5 through selsyn sensor 7 and selsyn receiver 14, which are electrically connected into a tracking system. Emergency rotation of the rotary propeller blades is carried out manually 8.
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