RU2394165C1 - Method of fuel feed control on starting gas turbine engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed method consists in that, on starting engine and up to rpm feedback closing, gas generator rotor rpm and combustion product temperatures are measured and control signal for actuator fuel feed control valve is generated. Control signal magnitude is defined from programmed relationship and cored in operation according to combustion product temperature. Note here that, on approaching maximum combustion product temperature, correction factor varies smoothly from unity, at temperature below limiting setting minus braking zone, to threshold non-zero value at temperature above limiting setting in compliance with claimed relationship.

EFFECT: higher reliability of starting gas turbine engine, shorter start-up time and longer life.

4 cl, 5 dwg

Description

The invention relates to the field of launch control of gas turbine engines used as power units in the gas and energy industries.

A known method of dispensing fuel in the process of accelerating a gas turbine engine by measuring the air pressure behind the compressor and the rotational speed of the engine rotor, forming a fuel consumption control program in accordance with the measured parameters and moving the metering element in proportion to the deviation of the current fuel consumption from the set program [Lyubomudrov Yu.V. . Application of the theory of similarity in the design of control systems for gas turbine engines. M .: Mechanical Engineering, 1971, p.96].

The specified method does not provide an acceptable acceleration time, does not exclude the problem of hovering during acceleration, allows the temperature to be exceeded during acceleration.

There is a known method of starting (NK-12ST Engine (Series 02). Operation and maintenance instructions. Kuibyshev, 1984, p.95, 312), where the fuel is supplied according to a predetermined dependence, and when the limit temperature is reached at the start, the achieved at the time of exceeding the maximum temperature of fuel consumption. In the fuel control program, to achieve this, the variable t _ign in the function f (t _ign ) is simply fixed. Due to the fact that the engine is in acceleration mode, despite the fixation of fuel consumption, a further increase in the engine speed occurs, as a result, the air flow through the engine increases and the temperature of the combustion products decreases, after which the start resumes in the previous mode.

The disadvantage of this method is the low starting reliability of gas turbine engines with so-called "low-emission" combustion chambers, which are characterized by a low content of harmful emissions and a high degree of fuel combustion, which have recently become more widespread.

, дозирование топлива для поддержания величины

, соответствующей данной зависимости

, и ограничение дозирования топлива по программной зависимости G_t=f(n_ВД, Т_ВХ), где дополнительно формируют пороговое и программное значение величины ускорения

и

, фактическую величину

сравнивают с

при

<

формируют разрешающий сигнал на коррекцию программной зависимости G₁=f(n_ВД, Т_ВХ) с заданной скоростью изменения коэффициента коррекции K(^dK/_dt), сравнивают фактическую величину

с

, и при

≥

разрешающий сигнал снимают и продолжают ограничение дозирования топлива по откорректированной программной зависимости G^, _t=f(n_ВД, Т_ВХ)·K, а повторные запуски осуществляют с учетом измененной величины коэффициента К.A known method of dispensing fuel at the start of a gas turbine engine (patent RU No. 2316664 C1, F02 C9 / 26, 2008), which consists in measuring the rotational speed of the rotor of the gas generator n _vd , determining the magnitude of the acceleration

dosing fuel to maintain value

corresponding to this dependence

, and the restriction of fuel dosing according to the software dependence G _t = f (n _VD , T _VX ), where the threshold and program value of the acceleration value are additionally formed

and

actual value

compare with

at

<

form an enable signal for the correction of the software dependence G ₁ = f (n _VD , T _VX ) with a given rate of change of the correction coefficient K ( ^dK / _dt ), compare the actual value

from

, and when

≥

the enable signal is removed and the fuel dosage is limited by the adjusted software dependence G ^, _t = f (n _VD , T _VX ) · K, and repeated starts are carried out taking into account the changed value of the coefficient K.

=f(n_ВД) является отсутствие механизма обратной коррекции ограничивающей зависимости G^' _t=f(n_ВД, Т_ВХ)·К, так как точная зависимость между оптимальным темпом запуска и Т_ВХ неизвестна и, кроме того, она может изменяться по мере износа двигателя. Таким образом, значение коэффициента К, определенное для одного Т_ВХ, может оказаться необоснованно заниженным для других значений Т_ВХ и привести к увеличению времени запуска и времени нахождения двигателя в опасной зоне резонансных частот вращения.The disadvantage of this method in addition to the difficulty of determining the numerical value of the dependence

= f (n _VD ) is the lack of a backward correction mechanism for the limiting dependence G ^' _t = f (n _VD , T _VX ) · K, since the exact relationship between the optimal trigger rate and T _{VX is} unknown and, moreover, it can change as engine wear. Thus, the value of the coefficient K, determined for one T _BX , may turn out to be unreasonably underestimated for other values of T _BX and lead to an increase in the start time and the residence time of the engine in the danger zone of the resonant rotational speeds.

, дозирование топлива для поддержания величины

, соответствующей данной зависимости

=f(n_ВД), где дополнительно измеряют температуру воздуха на входе в двигатель Т_ВХ и температуру продуктов сгорания топлива Т_ПР, формируют пороговое значение по

зависимости

=f(Т_ВХ), сравнивают Т_ПР с

, и при Т_ПР>

изменяют дозирование топлива для снижения величины

до величины

=

·К_кор, где К_кор - коэффициент коррекции, определяемый зависимостью К_кор=f(Т_ВХ), а при Т_ПР<

восстанавливают величину

в соответствии с заданной зависимостью

=f(n_ВД).Closest to the proposed is a method of dispensing fuel at the start of a gas turbine engine (patent RU 2316663 C1, F02C 9/26, 2008), including measuring the rotational speed of the rotor of the gas generator n _VD , determining the magnitude of the acceleration

dosing fuel to maintain value

corresponding to this dependence

= f (n _VD ), where the air temperature at the engine inlet T _BX and the temperature of the fuel combustion products T _PR are additionally measured, a threshold value is generated for

addictions

= f (T _BX ), compare T _PR with

, and at T _PR >

change the dosage of fuel to reduce the value

up to

=

· To _Kor , where K _Kor - correction coefficient, determined by the dependence of K _Kor = f (T _BX ), and at T _PR <

restore the value

according to the given dependence

= f (n _VD ).

=f(n_ВД). Для обеспечения надежного запуска в различных условиях окружающей среды необходимы обширные знания о статических характеристиках двигателя, а также об изменении статических зависимостей двигателя по мере его износа. При некорректно определенной зависимости

=f(n_ВД) возможно либо «зависание» двигателя на запуске (при заниженных значениях

=f(n_ВД)), либо помпаж компрессора двигателя (при завышенных значениях

=f(n_ВД)).The disadvantage of this method is the difficulty of determining the dependence

= f (n _VD ). To ensure reliable starting in various environmental conditions, extensive knowledge of the static characteristics of the engine, as well as the change in the static dependences of the engine as it deteriorates, is required. With an incorrectly defined dependency

= f (n _VD ) it is possible either to “freeze” the engine at start-up (at low values

= f (n _VD )), or surging motor compressor (at high values

= f (n _VD )).

The technical result obtained by the implementation or use of a tool embodying the invention is expressed in increasing the reliability of starting a gas turbine engine by lowering the temperature of the combustion products, reducing the time spent by the engine in the zone of resonant rotational speeds, decreasing the starting time, and increasing the engine life. The solution to all of the above problems is achieved by optimizing the supply of fuel to the combustion chamber during the start of the gas turbine engine. The essence of the invention is to establish a relationship between the rate of increase in fuel consumption at the start and the temperature of the combustion products and / or its rate of rise, at which the probability of the extinction of the combustion chamber at the start is reduced and the time spent by the engine in the zone of resonant rotational speeds during start-up is minimized.

This is achieved by the fact that in the method of controlling the fuel supply at the start of gas turbine engines, which consists in the fact that at the start-up stage until the feedback of the frequency closes, the rotational speed of the gas generator rotor is measured, the temperature of the combustion products and a control action is formed on the actuator - the metering valve fuel supply to the combustion chamber, the magnitude of the control action is determined by the software dependence with its subsequent correction, the correction is carried out according to the product temperature s combustion, wherein at least approaching the limit temperature combustion correction coefficient varies smoothly from unity at a temperature lower than a restrictive set point minus the braking zone, to the threshold of non-zero values at a temperature above the setpoint preamble in accordance with:

Where:

- откорректированная скорость нарастания расхода топлива;

- adjusted rate of increase in fuel consumption;

- скорость нарастания программной зависимости расхода топлива;

- slew rate of the software dependence of fuel consumption;

t _ign is the on time from the moment of ignition;

Tt is the temperature of the combustion products;

K _cor _ _T (Tt) is the correction coefficient for the temperature of the products of combustion;

k is the coefficient of deceleration of the launch when exceeding the limit Tt (<l);

T _lim - temperature limitation of the combustion products at the start;

T _bound - braking zone.

и скорость роста температуры продуктов сгорания

. В этом случае в качестве коэффициента коррекции выбирается либо один из рассчитанных коэффициентов К_{кор_T}(Tt), K_{кор_T} To determine the correction factor for the temperature of the combustion products, a forecast of the temperature of the combustion products can be used.

and rate of increase in temperature of combustion products

. In this case, either one of the calculated coefficients K _{cor_T} (Tt), K _{cor_T}

) и K_{кор_T}(

), либо минимальное из рассчитанных значений К_{кор_T}.(Tt,

,

)=min(K_{кор_T}(Tt); К_{кор_T}(

); К_{кор_T}(

)), либо комбинация описанных выше способов.(

) and K _{cor_T} (

), or the minimum of the calculated values of K _{cor_T} . (Tt,

,

) = min (K _{cor_T} (Tt); K _{cor_T} (

); To _{box_T} (

)), or a combination of the methods described above.

Figure 1 shows a functional diagram of the implementation of the proposed method.

Figure 2 shows the functioning algorithm in the case of correction for the temperature of the combustion products.

Figure 3 shows a graphical display of the method for calculating the correction coefficient for the temperature of the products of combustion To _{Kor_T} (Tt).

Figure 4 presents the acceleration process of a gas turbine engine in the implementation of the proposed method.

Figure 5 shows a view of a standard software acceleration dependency and a type of dependence changed for the proposed method.

The low-emission combustion chambers of modern gas turbine engines, characterized by a low content of harmful emissions and a high degree of fuel combustion, operate with the so-called “lean mixture”, that is, the ratio of fuel and air supplied to the combustion chamber is significantly less than the ideal stoichiometric fuel-oxidizer ratio. When stopping the increase in fuel consumption during acceleration (which is often used in existing methods for controlling the start of gas turbine engines when the temperature of the combustion products is reached), engines with such combustion chambers often extinguish the combustion chamber and crash the engine, which in some cases (for example, at high ambient temperature) makes starting an engine with a low emission combustion chamber impossible.

To ensure stable start-up of gas turbine engines with low-emission combustion chambers, a method is used in which, when the combustion temperature is reached, it does not stop the increase in fuel consumption, but slows down the flow rate, i.e., the function K _{cor_T} (Tt) has the following form:

where k is the start delay coefficient when the limit Tt (<1) is exceeded, and T _lim is the temperature limit of the combustion products at the start.

This allows, on the one hand, to prevent the extinction of the combustion chamber, on the other hand, to prevent the temperature of the combustion products from starting up above the limit value.

If it is not the temperature value that is limited, but its growth rate, formula (1) takes the following form:

- предельная скорость изменения температуры продуктов сгорания, а

- текущая скорость ее изменения. Это помогает резко снизить вероятность погасания камеры сгорания на запуске, но не исключает его полностью. В связи с тем что вероятность погасания камеры сгорания на запуске тем выше, чем резче снижается темп нарастания расхода топлива, целесообразно учитывать Tt (и/или

,

) не доходя до ограничивающего значения Т_lim(

) - в некоторой зоне T_bound (и/или

), называемой зоной торможения, при таком подходе в ряде случаев удается вообще не допустить достижения T_lim(

). При введении линейного участка перехода от значения 1 до k при значениях Tt в пределах [T_lim-Т_bound; Т_lim] формула (1) приобретает следующий вид:Where

- the maximum rate of change of temperature of the combustion products, and

- the current rate of change. This helps to sharply reduce the likelihood of the extinction of the combustion chamber at startup, but does not completely exclude it. Due to the fact that the probability of extinction of the combustion chamber at startup is higher, the sharper the rate of increase in fuel consumption decreases, it is advisable to take into account Tt (and / or

,

) not reaching the limiting value of T _lim (

) - in some zone T _bound (and / or

), called the braking zone, with this approach, in some cases, it is possible to prevent T _lim (

) With the introduction of a linear section of the transition from a value of 1 to k with values of Tt within [T _lim -T _bound ; T _lim ] formula (1) takes the following form:

The algorithm for functioning in the correction mode for the temperature of the combustion products that implements this expression is presented in figure 2.

можно достичь с помощью применения его расчета не кусочно-линейным способом, а с помощью сплайн-кривой на участке T_lim-Т_bound≤Tt≤Т_lim.Increasing the smoothness of the change in the rate of fuel consumption

can be achieved by applying its calculation not in a piecewise linear way, but using a spline curve in the section T _lim -T _bound ≤Tt≤T _lim .

Graphically, the dependence described in formula (3) is shown in FIG. 3, where the results of calculating the dependence of _{Kcore_T} (Tt) on the temperature of the combustion products are presented; a - applied linear dependence of the correction of the rate of fuel consumption, b - a possible correction using a spline curve.

When limiting not the temperature of the combustion products, but the rate of change, formula (3) takes the following form:

When working on predicting the temperature of combustion products, formula (3) takes the following form:

When limiting simultaneously the temperature of the combustion products, its forecast and its rate of change, the minimum value of k is selected from the results obtained by formulas (3), (4) and (5), that is:

T_lim=660°С, T_bound=80°С и k=0.2A view of the acceleration process when the temperature of the combustion products enters into force is presented in Fig. 4, which shows the results of the operation of the fuel supply control at startup with the following initial data:

T _lim = 660 ° C, T _bound = 80 ° C and k = 0.2

A comparative view of the standard acceleration curve and resulting from the application of the proposed acceleration method are shown in Fig. 5, where the graphical dependences of the fuel gas consumption at the start of the launch are graphically presented.

в блоке 2 определяется темп нарастания расхода топлива

, в блоке 3, учитывая определенный ранее темп

, рассчитывается требуемый расход топлива Gt в данный момент времени, в блоке 4, на основании расходной характеристики дозатора газа, а также давления и температуры топливного газа на входе дозатора газа, рассчитывается задание на дозатор газа, то есть осуществляется перевод из требуемого расхода (кг/час) в % (mА) задания на дозатор газа, поскольку во время запуска давление в камере сгорания значительно меньше давления топливного газа (так как в этот момент еще открыты клапана перепуска воздуха) - истечение топлива через дозатор является сверхкритическим и давление воздуха в камере сгорания (за дозатором) не учитывается.A functional diagram of a possible control system that implements the proposed method is presented in figure 1, where block 1, based on the temperature of the combustion products and / or its rate of rise, determines the maximum allowable correction coefficient for the rate of increase in fuel consumption k _lim , based on a certain k _lim and initially set nominal rate of increase in fuel consumption

in block 2, the rate of increase in fuel consumption is determined

, in block 3, given the previously defined pace

, the required fuel consumption Gt at a given time is calculated, in block 4, based on the flow characteristics of the gas meter, as well as the pressure and temperature of the fuel gas at the inlet of the gas meter, the task for the gas meter is calculated, that is, the transfer is made from the required flow rate (kg / hour) in% (mA) of the task for the gas metering device, since during start-up the pressure in the combustion chamber is much less than the pressure of the fuel gas (since at this moment the air bypass valves are still open) - the outflow of fuel through the metering unit is over riticheskim and air pressure in the combustion chamber (for a dispenser) is not considered.

This method is implemented as part of serial automatic control systems for gas pumping units with gas turbine engines ДГ-90, ДН-80, ДУ-80 (ГП НКПГ "Заря-Машпроект") at 19 gas compressor stations of OAO "Gazprom" and has shown its high reliability.

Means of implementing this control scheme can be selected integrated control systems multiprocessor MSKU 5000-01, MSKU-SS 4510 manufactured by NPF Sistema-Service CJSC (St. Petersburg). MSKU-5000 is built on the basis of software and hardware of Siemens Simatic S7. In this system, the computing core is implemented on the basis of the processor CPU 416-2DP. Input-output is carried out through distributed peripherals based on modules of the ET-200S family. For processing fast signals (with a cycle of 0.1 ms or less), the FM-458DP module with an EXM-438 expander is used. Software method is implemented in Simatic S7-SCL language (language of IEC 61131-3 standard). MSKU-SS 4510 is built on the basis of Octagon and Fastwel hardware and proprietary software of NPF Sistema-Service CJSC. The computing core of the system is implemented on the basis of the Octagon 5066 processor module, input-output is carried out through the analog and discrete input-output modules manufactured by Octagon, Fastwel and in-house developed and manufactured by NPF Sistema-Service CJSC.

The proposed method provides an increase in the reliability of starting a gas turbine engine by lowering the temperature of the combustion products, reducing the time spent by the engine in the zone of resonant rotational speeds, decreasing the starting time, and increasing the engine life.

Claims (4)

1. A method of controlling the supply of fuel at the start of a gas turbine engine, which consists in the fact that at the start-up stage until the feedback loop closes on frequency, the rotational speed of the gas generator rotor is measured, the temperature of the combustion products and a control action is formed on the actuator - a valve that dispenses the fuel to the chamber combustion, the magnitude of the control action is determined by the software dependence with its subsequent correction, characterized in that the correction is carried out according to the temperature of the products Rania, wherein at least approaching the limit temperature combustion correction coefficient gradually change from unity at a temperature lower than a restrictive set point minus the braking zone, to the threshold of non-zero values at a temperature above the setpoint preamble in accordance with:

Where

- adjusted rate of increase in fuel consumption;

- slew rate software dependence of fuel consumption;
t _ign is the on time from the moment of ignition;
Tt is the temperature of the combustion products;
K _cor _ _T (Tt) is the correction coefficient for the temperature of the products of combustion;
k is the coefficient of deceleration of the launch when exceeding the limit Tt (<l);
T _lim - temperature limitation of the combustion products at the start;
T _bound - braking zone. 2. The method according to claim 1, characterized in that for the correction using the forecast of the temperature of the products of combustion K _{box_T}

3. The method according to claim 1, characterized in that for the correction using the rate of increase in temperature of the products of combustion To _{Kor_T}

4. The method according to claim 1, characterized in that for correction use the minimum of the correction factors calculated by the methods of claims 1-3.
To _{box_T} .

= min (K _{cor_T} (Tt); K _{cor_T}

To _{box_T}

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