RU2602644C1 - Method for protection of dual-frow turbojet engine against low pressure turbine spin-up - Google Patents

Abstract

FIELD: engines.

SUBSTANCE: invention relates to gas turbine engine building, namely to systems for automatic protection of gas turbine engine against turbine spin-up at its disconnection from the compressor shaft. For determining technical state of engine is additionally determined initial S_beg and current S_cur values of rotor sliding using formulas:

and

. Note here that n_{re beg} - frequency of turbocompressor rotation before change of sliding, rev/min; n_{r beg} - frequency of rotation of low pressure turbine before change of sliding, rev/min; n_{re cur} - frequency of turbocompressor rotation through a time interval Δt, rev/min; n_{r cur} - frequency of low pressure turbine through a time interval Δt, rev/min. Calculate value ΔS = S_cur-S_beg and compared it with preset initially value A₁. Calculate value Δn_r= n_{r beg}-n_{r cur} and compared it with preset initially value A₂. In case if at the same time satisfied the condition under which ΔS > A₁ and Δn_r> A₂, then carry out decrease or the complete cessation of supply of fuel in the engine and giving of a signal on opening of valves of restart-up of air in the compressor.

EFFECT: declared invention will allow to increase reliability of determination of faults and reliability of protection system of bypass turbojet engine low-pressure turbine spin-up.

1 cl, 1 dwg

Description

The invention relates to the field of gas turbine engine manufacturing, and in particular to systems for the automatic protection of a gas turbine engine from spinning a turbine when it is disconnected from the compressor shaft.

A known method of automatic protection of a gas turbine engine, the essence of which is that with the help of the engine protection unit measure the speed n of the engine turbine, compare the measured value with a predetermined limit value, and when the speed n of the turbine increases above the predetermined value, a control signal is generated on stopping the supply of fuel to the combustion chamber of a gas turbine engine (patent RU No. 2493393, IPC F02C 9/46, publ. 09/20/2013).

The disadvantage of this method is the lack of speed of the system, as well as the need to create and use an autonomous protection unit, which increases the cost of the engine and complicates its design, because such autonomous units are usually equipped with a separate set of speed sensors that are not used in a standard automatic control system or engine diagnostic system.

по времени частоты вращения ротора турбины (патент US №6176074, МПК F01D 21/04, 21/06, F02C 9/46).Known methods for the automatic protection of a gas turbine engine from spin-up, in which to increase the speed of the system in terms of detecting the fact of spin-up of the turbine, an additional definition of the first derivative is provided

the time frequency of rotation of the turbine rotor (US patent No. 6176074, IPC F01D 21/04, 21/06, F02C 9/46).

возможны ложные срабатывания системы, например, из-за кратковременных сбоев системы измерения частоты вращения n, вызванных переменным контактом в электропроводке датчика частоты вращения. Для устранения этого недостатка в подобных системах защиты желательно иметь два и более независимых параметра, сбой которых одновременно из-за отказов электропроводки следует оценивать как практически невероятное событие.The disadvantage of this method is that when using the parameter of the speed n and its derivative

possible false alarms of the system, for example, due to short-term malfunctions of the speed measurement system n caused by an alternating contact in the wiring of the speed sensor. To eliminate this drawback in such protection systems, it is desirable to have two or more independent parameters, the failure of which at the same time due to electrical wiring failures should be assessed as an almost unbelievable event.

Closest to the claimed is a method of protecting a dual-circuit turbojet engine from the spin of a low pressure turbine, including measuring the speed of the turbocompressor, the speed of the low pressure turbine driving the fan into rotation, determining the technical condition of the engine based on the measured parameters, reducing or completely stopping fuel supply to the engine in case of detection of disconnection of the low pressure turbine from the fan shaft of the gas turbine engine (patent RU No. 2376487, M To F02C 9/46, publ. 20.12.2009). The system that implements the known method contains magnetic induction speed sensors in the systems for monitoring the technical condition and engine control, as well as a pressure sensor for the torque measuring system. The moment of violation of the integrity of the transmission is diagnosed simultaneously by the speed sensors of the opposite rotors of the engine. Unlike rotor speed sensors are standardly equipped (standard) sensors for the speed of a free turbine and the speed of a turbocompressor, and are used in an electronic engine control system. In this case, if the limit value of the rotor speed of the power turbine is exceeded, the protection system issues a command to the actuator of the pump regulator to reduce the fuel supply G _t to the engine. In case of exceeding the critical value of the limit speed of the power turbine, the electronic control system generates a command to completely stop the fuel supply to the engine (G _t = 0).

The disadvantage of this method, adopted as a prototype, is the need to use a special system for measuring torque, including pressure sensor. In general, this leads to a complication of the design of the engine and to a decrease in its reliability, as well as to an increase in the cost of the engine, including increase in operating costs. Also, the complexity of the algorithm for determining the fact of the disengagement of the shafts by changing the amplitude-frequency characteristics of the signals. When disconnecting the turbine shaft and the compressor shaft, damage to the speed sensor of the power turbine may occur, which leads to inoperability of the protection system. In addition, in the case of the use of magnetic induction sensors such as DTA, ДДВ - 2500 during the spin-up and displacement of a free turbine (low-pressure turbine), the required mounting gap between the sensor and inductor changes, as a result, a significant measurement error n occurs, which makes the protection system against Promotion is also inoperative.

The technical result of the claimed invention is to increase the reliability of the determination of faults and increase the reliability of the protection system of a bypass turbojet engine from the promotion of a low pressure turbine.

The specified technical result is achieved by the fact that in the method of protecting a double-circuit turbojet engine from the spin of a low pressure turbine, including measuring a rotational speed of a turbocompressor, a rotational speed of a low pressure turbine driving a fan, determining a technical condition of the engine based on the measured parameters, reducing or completely stopping the flow fuel to the engine in case of detachment of the low pressure turbine from the fan shaft, according to the invention for definiteness technical condition of the engine further comprising determining an initial _{beginning of} S and current value of S _tech rotor slip by the formulas:

и

, где

and

where

S _beg - the amount of slip at the initial time before the change;

S _tech - the amount of slip through the time interval Δt;

n _{vd nach} - turbocharger rotation speed before the slip change, rpm;

n _{in the beginning} is the rotational speed of the low pressure turbine before changing the slip, rpm

n _{vd tech} - turbocharger speed through a time interval Δt, rpm;

n _{in tech} - frequency of the low-pressure turbine at a time interval Δt, rev / min, calculated value ΔS = S -S _{tech beginning} and compared with the originally predetermined value A ₁ was calculated _in the magnitude Δn = n _{in the beginning} - n and compared _{in tech} it with the initially set value of A ₂ , in this case, if the condition is satisfied at the same time, under which ΔS> A ₁ and Δn _in > A ₂ , then the fuel supply to the engine is reduced or completely stopped and a signal is sent to open the air bypass valves in the compressor .

Implementation of the above operations of the claimed method allows to exclude measurement errors, false alarms of the engine protection system due to short-term malfunctions in the measurement of parameters and the occurrence of malfunctions of the protection system, which increases the reliability of the determination of malfunctions and the reliability of the protection system of a double-circuit turbojet engine from spinning a low pressure turbine. Also, the proposed method allows to simplify the algorithm for determining the separation of the shafts of the turbine and compressor, to increase speed and reduce the cost of creating and operating a protection system by eliminating additional measuring devices.

The claimed method can be implemented using a device whose structural diagram is shown in the drawing.

Using block 1, measure the rotational speed n _vd (n _{vd nach} , n _{vd tech} ) of the high-pressure rotor (turbocharger). By means of block 2, the rotational speed n is measured _in (n _{in the beginning} , n _{in the tech} ) of the low pressure turbine, which drives the engine fan. The sensors used to measure the rotational speed of the high-pressure rotor and low-pressure turbine are similar to those used in the prototype and are standardly equipped (standard) sensors. However, unlike the prototype, to implement the inventive method, a sensor inductor for measuring the rotational speed of a low pressure turbine is located on the fan shaft, and the sensor itself is located near the fan blades. This arrangement eliminates the breakdown of the sensor during the destruction of the low pressure turbine.

By means of block 3, the slip S of both rotors is determined as the ratio of rotational frequencies n _in / n _in , i.e. determine the initial S _{beginning the} magnitude of the slip of the rotors at the time before the start of the change in slip and the current S _tech slip value of the rotors after a fixed time interval Δt (Δt = 0.2 s) in accordance with the following formulas:

и

, где

and

where

n _{vd nach} - turbocharger rotation speed before the slip change, rpm;

n _{in the beginning} is the rotational speed of the low pressure turbine before changing the slip, rpm

n _{vd tech} - turbocharger speed through a time interval Δt, rpm;

n _{in tech} - the frequency of the low-pressure turbine through the time interval Δt, rpm

по времени параметра частоты вращения n_в турбины низкого давления (n_{в нач}, n_{в тек}).Using block 4 determine the first derivative

in time of the parameter of the rotational speed n _{to the} low pressure turbine (n _{at the beginning} , n _{at the tech} ).

Blocks 5 and 6 are threshold devices.

Using block 5, the sliding parameter S is evaluated, i.e. calculate the difference between the current and initial values of the slip ΔS = S _tech -S _beg and compare with the first, initially set value A ₁ (A ₁ = 0,3). If ΔS> A ₁ for a fixed time interval Δt (Δt = 0.2 s), then the output of block 5 generates a logical signal "1".

- вычисляют величину Δn_в=n_{в нач} - n_{в тек}. В случае если величина Δn_в за тот же фиксированный интервал времени Δt (Δt=0,2 с) больше второй, изначально заданной величины А₂ (А₂=500 об/мин), то на выходе блока 6 формируется второй логический сигнал «1».Using block 6, the parameter is evaluated

- calculate the value Δn _in = n _{in the beginning} - n _{in tech} . If the value Δn _in the same fixed time interval Δt (Δt = 0.2 s) is greater than the second, initially set value A ₂ (A ₂ = 500 rpm), then the second logic signal "1 ".

The values of A ₁ and A ₂ are assigned from the condition that, in the case of a low-pressure turbine disengaging from a fan (low-pressure compressor), the spin speed of the turbine rotor will be less than the speed at which the turbine disks break.

If at the same time the condition is satisfied under which ΔS> A ₁ and Δn _in > A ₂ , i.e. with the simultaneous presence of logic signals “1” at the two inputs of block 7, a block 8 command is generated at block 7. Block 8 is a fuel pump-regulator that provides fuel to the engine’s combustion chamber and controls the air bypass valves in the engine compressor. If the signal at the output of block 7 is observed for a fixed time Δt (Δt = 0.2 s), then the metering needle of the pump controller moves at the maximum possible rate to the low gas position, i.e. in the direction of decreasing the fuel flow to the engine G _t (i.e., reduction is carried out in the engine fuel supply). If the signal at the output of block 7 is observed for a time of 0.4 s, then the fuel supply to the engine is reduced or completely stopped and the signal for opening the air bypass valves in the compressor is fed: the protection system generates a signal to completely stop the fuel supply G _t to the combustion chamber engine (G _t = 0) and a signal to open the air bypass valves in the compressor. Opening the air bypass valves from the compressor to the external circuit of the engine at maximum mode leads to re-enrichment of the mixture and the extinction of the low-emission combustion chamber, thus shutting off the fuel supply. In addition, when the bypass valves are opened, the power of the low-pressure turbine drops, which contributes to less damage when the turbine breaks down and localizes the failure.

Used to implement the inventive method, the electronic engine controller is a specialized electronic digital computer operating in real time and equipped with devices for interfacing with sensors, signaling devices, actuators and engine and aircraft systems.

Claims (1)

A method of protecting a double-circuit turbojet engine from spinning a low-pressure turbine, including measuring the speed of the turbocompressor, the speed of the low-pressure turbine that drives the fan, determining the technical condition of the engine based on the measured parameters, reducing or completely cutting off the fuel supply to the engine in the event of a disconnected turbine low pressure from the fan shaft, characterized in that for determining the technical condition of the engine but define the initial and current _nach S S _tech rotor slip value by formulas: S = n _{nach nach tm} / n _{in the beginning} and S = n _{tech tm tech} / n _{in tech,} wherein
S _beg - the amount of slip at the initial time before the change;
S _tech - the amount of slip through the time interval Δt;
n _{vd nach} - turbocharger rotation speed before the slip change, rpm;
n _{in the beginning} is the rotational speed of the low pressure turbine before changing the slip, rpm
n _{vd tech} - turbocharger speed through a time interval Δt, rpm;
n _{in tech} - frequency of the low-pressure turbine at a time interval Δt, rev / min
calculated value ΔS = S _tech - S _beginning and compared with the originally predetermined value A ₁ was calculated value Δn _in = n _{in the beginning} - n _{in tech} and compared with the originally predetermined value A _2, wherein if both the condition, in which ΔS> A ₁ and Δn _in > A ₂ , then reduce or completely stop the fuel supply to the engine and signal to open the air bypass valves in the compressor.

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