RU2316665C1 - Method to protect gas-turbine plant from overspeeding of power turbine - Google Patents

Abstract

FIELD: mechanical engineering; gas-turbine plants.

SUBSTANCE: invention relates to control systems of gas-turbine plants, namely, to protection systems of gas-turbine plants used for mechanical drive and drive of electric generator to protect them against dangerous overspeeding of free power turbine. According to proposed method of protection of gas-turbine plant from overspeeding of power turbine at abrupt drop of load including measurement of speed

of power turbine, determining its first time derivative

and gas generator speed

reduced to air temperature

at plant input, forming of limiting values

and comparing them with

,

,

, respectively, at

and

bypassing of gas into atmosphere after gas generator turbine is provided. At fulfilling of condition

and

, bypassing of gas after gas generator turbine into atmosphere is provided bypassing power turbine by means of gas bypass valves. Thanks to it reduction of energy supply to power turbine and counteraction of overspeeding

is provided. Moreover, value

is found from formula

where

is setting value of power turbine speed and

where

is static error of power turbine speed control of gas-turbine plant. Value

is obtained experimentally at changing over of gas-turbine plant loads comparable with power in supply networks at operation in parallel with "infinite" power network. Setting value of speed

of gas-turbine plant is required to maintain said power. Constant

providing required reserve for preventing false operation should be 5-7 times greater than static error of speed

of power turbine of gas-turbine plant being approximately 60-100 rpm.

EFFECT: improved reliability, increased service life and safety of gas-turbine plant.

1 dwg

Description

The invention relates to control systems for gas turbine units, and in particular to systems for protecting gas turbine units for a mechanical drive and drive an electric generator from dangerous overruns of the rotational speed (spin) of a free power turbine.

There is a one-parameter method for protecting a gas turbine installation (GTU) from spinning a power turbine according to the physical value of the rotation speed of a power turbine n _st , which consists in measuring the value of n _st , forming the first and second frequency limit values n _st , comparing n _st with the first limit value and when exceeding n _{article of the} first limit value to give the operator an informational warning signal for taking measures to eliminate the casting. Then compares the n _article with a second limit value and completely stops the supply of fuel to the combustion chamber gas turbine (emergency stop, G _t = 0) when exceeding n _st second limit frequency values n _v [ "Functional fuel management module Series 5 centrifugal and axial compressors ", Document UM5421 (0.2.0), Compressor Control Corporation, USA, 2000, p. 95 ... 96].

The disadvantage of this method is the possibility of unjustified shutdown of the gas turbine, for example, during load shedding and short-term throwing n _st , which leads to interruptions in the generation of electricity, the need to switch gas turbines to other energy sources.

, уменьшение расхода топлива G_т в камеру сгорания ГТУ или кратковременный останов подачи топлива в зависимости от мощности, снимаемой с вала силовой турбины, или по наличию упреждающего сигнала о внезапном сбросе нагрузки [Патент США №5609465, F01D 17/06, 1997 г. Патент РФ №2225945, 7 F02С 9/46, 2002].There are also known methods of preventing the promotion of a GTU power turbine, which include measuring the speed of a power turbine n _st and determining the first time derivative

, a decrease in fuel consumption G _t in the gas turbine combustion chamber or a short-term shutdown of the fuel supply depending on the power taken from the shaft of the power turbine, or by the presence of a pre-emptive signal about the sudden load shedding [US Patent No. 5609465, F01D 17/06, 1997 Patent RF №2225945, 7 F02С 9/46, 2002].

However, these protection methods with an unfavorable combination of operational factors and design features of a gas turbine may not provide timely and reliable protection of a power turbine from spinning in a situation where the rotational speeds of a power turbine n _st and a gas turbine of a gas turbine generator n _g have maximum values and a relatively “high-speed” design is used free power turbine (n _st ≥5000 ... 7000 rpm or more, instead of typical 3000 rpm). In this case, a sudden complete disconnection of the load from the shaft of the power turbine occurs, and there is no pre-emptive signal about the load shedding.

Negative consequences of possible casting _item n can be automatic shutdown of the electric consumer or mechanical failure of the power turbine and gas turbine nonlocalized breakage, and as a result, damage to expensive equipment.

Another known method for controlling a gas turbine engine takes into account the operating mode and the dynamic state of its parameters and provides for measuring the rotational speed of the rotating engine assembly (rotor speed of the gas generator), generating a first threshold value that varies depending on the first derivative of the rotational speed of the assembly in a certain range. Moreover, if the actual speed exceeds not only the first, but also the second threshold value, which is greater than the first, they conclude that there is a “cast” of the rotational speed of the gas generator rotor. After detecting a frequency overshoot, the fuel consumption G _t in the engine is reduced by changing the electric current in the fuel valve actuator according to an analogous circuit [US Patent No. 6321525 B1, F02C 9/28, 2001].

However, with a complete load shedding, this protection method may also not provide reliable and timely protection of the power turbine against unwinding due to the insufficient speed characteristic of the analog fuel valve control circuit. So, in control schemes of this type, the time of complete movement of the fuel dispenser from the maximum to the minimum position is Δt = 1 ... 1.5 seconds, which may not be sufficient to counter the casting n _st in a situation where the rate of increase of n _st to limit values n _St significantly exceeds the possible rate of decrease in energy supply (gas generator mode).

, приведенной частоты вращения ротора газогенератора ГТУ n_ггпр, а также сигнала о сбросе нагрузки, формировании соответствующих пороговых значений параметров n_ст,

и n_ггпр, сравнении параметров n_ст,

и n_ггпр с их соответствующими пороговыми значениями, а при одновременном поступлении сигнала о превышении величины параметра n_ггпр над его пороговым значением (признак «высокого» режима работы) и сигнала о сбросе нагрузки, подают команду на отключение (полную отсечку) расхода топлива Gт в двигатель и включение агрегата зажигания на заданное время. После снижения частотных параметров ГТУ ниже соответствующих пороговых значений подают сигнал на включение подачи топлива в камеру сгорания [Патент РФ №2225945, F 02 С 9/46, 2004].Closest to the claimed is a method of preventing the promotion of a power turbine, which consists in measuring the frequency of rotation of the power turbine n _st and the first derivative of the frequency n _st

the reduced rotational speed of the rotor of the gas generator of gas turbine _engine n _ggpr , as well as the signal about load shedding, the formation of the corresponding threshold values of the parameters n _st ,

and n _ggpr , comparing the parameters of n _article ,

and n _ggr with their corresponding threshold values, and when a signal is received simultaneously that the value of the parameter n _ggr exceeds its threshold value (a sign of a "high" mode of operation) and a signal about load shedding, a command is sent to turn off (full cut-off) the fuel consumption GT in the engine and the inclusion of the ignition unit for a given time. After reducing the frequency parameters of the gas turbine below the corresponding threshold values, a signal is sent to turn on the fuel supply to the combustion chamber [RF Patent No. 2225945, F 02 С 9/46, 2004].

However, during the operation of the gas turbine, an unauthorized shutdown of the fuel supply during internal and (or) external accidental influences on the protection device is possible, for example, if there is a regular indication of a “high” mode of operation and a false load shedding signal appears (due to induced electromagnetic interference or input failure node registering the load shedding command).

With a short-term fuel cut-off and the subsequent restoration of the gas turbine operation mode, significant gradients of measuring thermogasdynamic loads on the combustion chamber and gas generator turbine are observed, which results in accelerated generation of gas turbine resource.

The consequences of the above disadvantages are interruptions in the generation of electricity, increased heat transfer on the power turbine and, as a result, low reliability, resource and operational safety of gas turbines.

The technical problem solved by the invention is to increase the reliability, resource and operational safety of a gas turbine installation by reducing heat transfer on a power turbine and eliminating its promotion by timely transfer of part of the gases leaving the gas generator turbine to the atmosphere, bypassing the power turbine, using bypass valves gases.

и приведенной по температуре воздуха на входе установки Т_вх частоты вращения газогенератора n_ггпр, формирование предельных значений n_ггпр ^пред, n_ст ^пред,

и сравнение их с n_ггпр, n_ст,

соответственно, согласно изобретению при n_ггпр>n_ггпр ^пред, n_ст>n_ст ^пред и

>

осуществляют перепуск газа за турбиной газогенератора в атмосферу.The essence of the invention lies in the fact that in a method of protecting a gas turbine installation from spinning a power turbine during a sudden load shedding, including measuring the speed of a power turbine n _st , determining its first time derivative

and given the air temperature at the inlet of the installation T _I gas generator speed n _gpr , the formation of limit values n _gpr ^before , n _st ^before ,

and comparing them with n _ggpr , n _article ,

respectively, according to the invention when n _ggpr> n _ggpr ^before, n _v> n and _v ^prev

>

carry out gas bypassing the gas generator turbine into the atmosphere.

>

осуществляют перепуск газа за турбиной газогенератора в атмосферу, минуя силовую турбину с помощью клапанов перепуска газов. Тем самым обеспечивается уменьшение подвода энергии к силовой турбине и парирование «заброса» n_ст.If the condition is met n _gpr > n _gpr ^before , n _st > n _st ^before and

>

carry out gas bypassing the gas generator turbine into the atmosphere, bypassing the power turbine using gas bypass valves. This ensures a reduction in the supply of energy to the power turbine and parry "cast" n _Art .

In addition, the value of n _st ^pre is determined by the formula n _st ^pre = n _st ^mouth + Δ, where n _st ^mouth is the reference value of the rotational speed of the power turbine, and Δ≥ (5-7) δn _st , where δn _st is the static control error frequency of rotation of a power turbine of a gas turbine installation. The value of n _st ^before obtained experimentally when switching loads comparable to the capacity of gas turbine in electrical networks when working in parallel with a network of "infinite" power.

The setpoint value of the rotational speed of a power turbine of a gas turbine unit, n _st., ^Must be maintained to ensure the required power. The constant Δ, which provides the required margin for eliminating false alarms, must be no less than 5 ... 7 times the static error in regulating the speed of a GTU power turbine n _st (δn _st ) and be ≈60 ... 100 rpm.

If Δ <(5-7) δn _st , an oscillatory process can be observed due to a decrease in n _st below n _st ^mouth and the subsequent restoration of n _st to n _st ^mouth in order to maintain a given power.

Improving the reliability and operational safety of a gas turbine is ensured by eliminating the unauthorized promotion of a power turbine and implementing a mode of smooth reduction of heat drop on a power turbine without the “thermal shock” characteristic of the prototype method.

The figure shows a longitudinal section of a gas turbine with a flowchart illustrating the implementation of the proposed method.

Block 1 - a sensor measuring air temperature T _I at the entrance to the gas turbine.

Block 2 - a sensor for measuring the rotational speed of the rotor of the gas generator n _gg .

Induction sensors of the ДЧВ-2500А type or of any other type, providing the measurement accuracy at the level of 0.01 ... 0.1% _, can be used as a measurement sensor n g.

Block 3 - arithmetic device, the input of which receives signals about the value of n _g and T _I. Based on information about the values of n and _gg T _in is calculated in unit 3 reduced rotor speed gasifier GTP:

Block 4 - block forming the limit value of the reduced rotational speed of the rotor of the gas generator GTU n _gpr ^before .

Block 5 - a comparator, in which the comparison n _ngpr with n _gpr ^before .

The functional purpose of the unit is to exclude the opening of the gas bypass valve at the “low” operating modes of the gas turbine generator, when this is not necessary, because the rejection of the casting n _{st is} satisfactorily provided in a known manner by reducing the fuel supply to the combustion chamber of the gas generator. The value of n _ggr ^{pre is} set below n _ggr for the nominal operating mode of the gas turbine. When n _ggpr > n _ggpr ^before the output of the comparator 5, the first high-level logical signal I ₁ = 1 is formed.

Block 6 - a sensor for measuring the rotational speed n _st power turbine GTU. Induction sensors of the ДЧВ-2500А type or of any other type, providing the measurement accuracy at the level of ± 0.1%, can be used as a measurement sensor n _st .

Block 7 is a differentiator in which the first time derivative of the parameter n _st (n _st ) is calculated.

(

). Величина

задается с учетом быстродействия открытия клапанов перепуска газов для газодинамического парирования «заброса» n_ст. В общем случае величина

может быть константой, например

=600...700 об/мин за 1 секунду и более, или функцией режима работы ГТУ, т.е. может зависеть от частоты вращения газогенератора n_гг или величины снижения потребляемой мощности Р.Block 8 - block forming the limit value of the first time derivative

(

) Value

is set taking into account the speed of opening the gas bypass valves for gas-dynamic parry "cast" n _Art . In the general case, the value

may be a constant for example

= 600 ... 700 rpm for 1 second or more, or a function of the operation mode of a gas turbine, i.e. may depend on the speed of the gas generator n _g or the magnitude of the reduction in power consumption R.

с

. При

>

на выходе компаратора формируется второй логический сигнал высокого уровня I₂=1.Block 9 - a comparator in which the comparison is performed

from

. At

>

at the output of the comparator, a second high-level logic signal I ₂ = 1 is formed.

может кратковременно (на Δт=0,01...0,05 с) достигать значений 600...700 об/мин за 1 секунду.Block 10 - block forming the limit value of the rotational speed n _st (n _st ^before ). The functional purpose of the unit is to exclude false alarms during short-term “drops” of the first derivative of the turbine frequency caused by typical load shedding (regular switching in electrical networks), at which the value

can shortly (at Δt = 0.01 ... 0.05 s) reach values of 600 ... 700 rpm in 1 second.

Block 11 is a comparator in which the comparison of n _st with n _st ^before . When n _st > n _st ^before the output of the comparator, a third high-level logic signal I ₃ = 1 is formed.

Block 12 is a logical device AND has three inputs and one output. The first input of block 12 receives a logical signal I ₁ , the second input - a logical signal I ₂ , and the third - a logical signal I ₃ . With the simultaneous presence of signals I ₁ = 1, I ₂ = 1 and I ₃ = 1 at the three inputs of block 12, a logical signal I ₄ = 1 is generated at the output of block 12, which is fed to the input of block 13 and ensures the opening of gas bypass valves behind the gas generator turbine GTU.

Block 13 - gas bypass valve behind the turbine of the gas turbine generator (a section shows one valve). Each gas bypass valve 13 is connected at the inlet to the flowing part of the annular channel between the gas generator turbine and the free turbine, and at the outlet to the atmosphere.

If there is a signal I ₄ = 0, the bypass valves 13 of the gas turbine unit 14 are in the closed state. When I ₄ = 1 is formed, the gas bypass valves 13 open and provide partial gas bypass from the gas generator turbine exit through the corresponding pipelines to the atmosphere, bypassing the power turbine, providing a reduction in the energy supply to the power turbine and parry reflux n _st .

The method is as follows.

Before and during the start-up of the gas turbine the gas bypass valve 13 behind the gas generator turbine is in the open position. After starting the gas generator, the gas bypass valve 13 is closed in manual or automatic mode.

When the gas turbine generator is operating in “low” modes (n _yyyy <n _yyyyyyy ^pre ), a low-level logic signal I ₁ = 0 is formed at the output of unit 5. Therefore, when n _st > 600 ... 700 rpm for 1 second and n _st > n _st ^before the gas bypass valve 13 behind the gas generator turbine remain in the closed position.

существенно возрастают. При превышении величины

предельного значения

≈600...700 об/мин за 1 секунду, а также при n_ст>n_ст ^пред на всех трех входах блока 12 формируются логические сигналы I_i=1. На выходе блока 12, работающего по логике И, также формируется логический сигнал высокого уровня I₄=1. Сигнал I₄=1 поступает на вход блока 13 и клапана перепуска газов открываются, обеспечивая перепуск газов газогенератора в атмосферу через трубопроводы и выходное устройство, минуя силовую турбину. Исходя из термодинамической схемы ГТУ, теплоперепад на силовой турбине уменьшается и частота вращения силовой турбины n_ст снижается.In the case of a sudden discharge of the entire load during operation of the gas turbine generator at the “high” mode (n _GPR > n _GPR ^before , I ₁ = 1), the parameters n _st and

increase significantly. If the value is exceeded

limit value

≈600 ... 700 rpm for 1 second, as well as for n _st > n _st ^before all three inputs of block 12 are formed logical signals I _i = 1. At the output of block 12, operating according to the AND logic, a high level logic signal I ₄ = 1 is also formed. The signal I ₄ = 1 arrives at the input of block 13 and the gas bypass valve opens, providing gas bypass of the gas generator into the atmosphere through pipelines and an output device, bypassing the power turbine. Based on the thermodynamic scheme of a gas turbine, heat transfer on a power turbine decreases and the speed of the power turbine n _st decreases.

The claimed invention was implemented in a digital electronic automatic control system and verified by testing in the composition of an energy gas turbine with a capacity of 12 MW, made on the basis of the PS-90A aircraft engine and including a free power turbine with a rated speed n _st ≥5000 rpm (GTU-12P) . The results of bench tests fully confirmed the timely and reliable protection of the power turbine from promotion, including the necessary dynamic accuracy of the measurement of parameter n _Art . According to the test results, supplemented by mathematical modeling of the operation of the gas turbine, it was also found that for effective counteraction of the frequency overshoots n _article it is advisable that the total time from the moment of signal formation I ₄ = 1 to the opening of all gas bypass valves does not exceed 0.1 ... 0 , 3 sec.

Claims (3)

1. A method of protecting a gas turbine installation from the promotion of a power turbine during a sudden load shedding, including measuring the speed of a power turbine n _st , determining its first time derivative

and given the air temperature at the inlet of the installation T _I gas generator speed n _gpr , the formation of limit values n _gpr ^before , n _st ^before ,

and comparing them with n _ggpr , n _article ,

, respectively, characterized in that for n _gpr > n _gpr ^before , n _st > n _st ^before and

carry out gas bypassing the gas generator turbine into the atmosphere. 2. The method of protecting a gas turbine installation according to claim 1, characterized in that the value of n _st ^pre is determined by the formula n _st ^pre = n _st ^mouth + Δ, where n _st ^mouth is the reference value of the rotational speed of the power turbine, and Δ≥ (5- 7) δn _st , where δn _st is the static error in regulating the frequency of rotation of the power turbine of a gas turbine installation. 3. The method of protection of a gas turbine installation according to claim 2, characterized in that the Δ value is 60 ... 100 rpm.