RU2767663C1 - Aircraft gas turbine engine capacitive ignition system control device - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to ignition of combustible mixtures using an electric spark, in particular to capacitive ignition units, and can be used to control ignition systems installed on aircraft engines. Aircraft gas turbine engine capacitive ignition system control device, comprising a storage capacitor discharge current sensor, first univibrator, time interval meter, control signal generator, in which time interval meter output is connected to control signal generator first output, circuit additionally includes an activator capacitor discharge current sensor, a second univibrator, a counter, wherein the activator capacitor discharge current sensor is connected to the activator capacitor circuit, storage capacitor discharge current sensor output is connected to the first univibrator input, the first univibrator output is connected to the time interval meter input and to the counter reset input, output of the capacitor discharge current sensor is connected to the input of the second univibrator, the output of the second univibrator is connected to the counting input of the counter, the output of the counter is connected to the second input of the control signal generator.

EFFECT: increased depth of control of technical condition of capacitive ignition systems of gas turbine engines of aircraft in order to ensure operation of spark plugs according to technical condition and reduced costs for ensuring the life cycle of the engine at the operation stage and the downtime of the aircraft by replacing the spark plugs before the onset of their failure state.

1 cl, 2 dwg

Description

The invention relates to the technique of igniting combustible mixtures using an electric spark, in particular to capacitive ignition units, and can be used to control ignition systems installed on aircraft engines.

A control device for the capacitive ignition system of jet engines is known [RF Patent No. 2338080, February 21, 2006], containing an ionization current sensor, electrodes located on both sides of the spark gap of the spark plug at a normalized distance, and an ionization current recorder. The conclusion about the performance of the spark plug is carried out according to the results of the evaluation of the parameters of the ionization current (amplitude, duration, shape) and comparison with reference values.

The disadvantages of this control device include the impossibility of its use to control capacitive ignition systems installed on the engine. Also, this method of control does not allow to control the frequency of the pulses of the discharge current - the frequency of sparking on the spark plugs.

A decrease in the repetition rate of spark discharges below the minimum allowable value in some cases leads to delays in the ignition of the air-fuel mixture in the combustion chambers, engine starts with a significant torch behind the nozzle (emission of a burning cloud of the air-fuel mixture behind the nozzle) during ground launches, to the so-called "gun" launches [H.V. Kesaev, R.S. Trofimov Reliability of aircraft. - M .: Mashinostroenie, 1982] with a surge of pressure in the combustion chamber, which, due to impact, can damage engine elements and elements of automatic control systems. When using ignition systems in conjunction with a starting igniter, a decrease in the frequency of repetition of spark discharges on a candle can lead to a decrease in the ignition range of the engine combustion chamber [V.A. Sosunov, Yu.A. Litvinov. Unsteady modes of operation of aircraft gas turbine engines, M.: Mashinostroenie, 1975, 216 p. (see p. 147)], [A.N. Lefevre. Processes in the combustion chambers of gas turbine engines: Per. from English. - M.: Mir, 1986. - 566 p. (see p. 245)].

In addition, with a reduced sparking frequency on the spark plugs during a restart (ignition of the air-fuel mixture) after cutting off the fuel supply during the operation of the engine anti-surge system (anti-surge start) [PS-90A aircraft engine: A.A. Inozemtsev, E.A. Konyaev, V.V. Medvedev, A.V. Neradko, A.E. Resov / Ed. A.A. Inozemtseva. M.: Libra-K, 2007, 320 p. (see p. 134)] ignition delay leads to an increase in the time for the engine to recover from surging and restore its operating mode: the re-ignition of the combustion chamber occurs at lower turbine speeds, respectively, the time to restore the existing engine operating mode increases. A later ignition of the air-fuel mixture in some cases can lead to a failure of the anti-surge start of the engine and turn it off in flight.

This reduces the reliability of operation of aircraft gas turbine engines.

The device [French Patent No. 2717534, published on March 17, 1994], which contains a detector unit to which the secondary windings of two current sensors are connected, a control unit for the breakdown voltage of the switching device connected to the voltage converter and to the control electrode of the switching device, is partially deprived of these shortcomings.

This control device allows, upon receipt of an external signal, for example, from a special remote control, to reduce the breakdown voltage of the switching device, while controlling the presence of a discharge current through the spark plug. This allows you to control the increase in the breakdown voltage of the spark plug above the control value and, if it is exceeded, replace the spark plug with an increased breakdown voltage.

However, this device also has significant disadvantages.

The spark plugs are removed after their breakdown voltage exceeds the control value, while the spark plugs still have a significant residual life for which it is possible to extend their operation, which leads to economic losses.

Checking the spark plugs is possible only autonomously, without starting the engine, since an attempt to start the engine with a reduced output voltage of the ignition system and the energy accumulated in the ignition unit can lead to engine ignition delays, including the so-called "gun" starts, in which it is possible damage to engine structural elements [H.V. Kesaev, R.S. Trofimov Reliability of aircraft. - M.: Mashinostroenie, 1982] or failure to start the engine due to a breakdown in the ignition of the air-fuel mixture.

In addition, this control device, as well as those described above, does not allow controlling the frequency of the discharge current pulses, which, as indicated above, largely determines the reliability of ignition of the fuel components in the engine.

Known devices for controlling the capacitive ignition system of aircraft engines, described in [Ignition unit SK-44-3B. Manual for technical operation 8G3.246.180 RE], containing a discharge current sensor, a time interval meter (time between successively following discharge current pulses) and a control signal shaper.

This device allows you to monitor the performance of a capacitive ignition system installed directly on the engine, as well as control the frequency of the discharge current pulses.

A disadvantage of the known device is the impossibility of ensuring sufficient testability of the ignition system, because the decision on the operability of the ignition system is made only upon the fact that the actual frequency of repetition of spark discharges on candles exceeds the minimum allowable value. In fact, the control device allows you to control only sudden failures of the ignition unit (breakdown of the storage capacitor, failure of the converter, etc.).

During the operation of the ignition system, there is a gradual wear of the electrode contacts due to electroerosive development [Processes in the combustion chambers of the gas turbine engine, A. Lefebvre, M: Mir, 1986, p. 242]. Each spark discharge leaves a small sink on the electrodes as a result of their electroerosive generation, which leads to an increase in the size of the spark gap of the candle. This, in turn, leads to an increase in the breakdown voltage of the spark plug and to a further increase in the energy released in its spark gap, which leads to a further increase in the electroerosive output of the spark plug electrodes.

With a significant operating time of the spark plug, the limiting state of wear of its electrodes sets in, at which the breakdown voltage of the spark gap of the spark plug becomes close to the output voltage of the ignition unit. This output voltage of the ignition unit is determined by the breakdown voltage of the switching spark gap, to which the activator capacitor is charged: when the activator capacitor is discharged through the primary winding of a high-voltage transformer, a high-voltage pulse is generated on its secondary winding, designed to preliminary breakdown of the spark gap of the candle [V.A. Balagurov. Ignition units, M., Mashinostroenie, 1968 (see p. 250)]. Due to the spread of the breakdown voltage of the switching arrester, the output voltage of the ignition booster also has a spread of values.

During normal operation of the ignition unit, after a breakdown of the switching spark gap, a high-voltage pulse is initially generated on the spark plug, caused by the discharge of the activator capacitor through a high-voltage transformer, which has a short duration, on the order of several tens of nanoseconds, which leads to a breakdown of the spark gap of the spark plug. After that, the main discharge of the storage capacitor to the spark plug occurs.

When approaching or exceeding the value of the breakdown voltage of the spark gap of the output voltage of the spark plug, before the breakdown of the spark gap of the spark plug, separate sparking delays occur. In this case, the activator capacitor is discharged through the primary winding of the high-voltage transformer, generating a high-voltage pulse on its secondary winding. However, the magnitude of the voltage of this pulse due to its spread is not enough for the breakdown of the spark gap. In this case, the discharge of the storage capacitor will not occur, and the switching spark gap will close. After recharging the activator capacitor, the switching gap will open again and another attempt will be made to breakdown the spark gap of the spark plug.

When this phenomenon occurs, the breakdown of the spark gap of the candle can be carried out after several such attempts, which will lead to a delay in the generation of the spark discharge. Control device [Afegat ignition SK-44-3B. Manual for technical operation 8G3.246.180 OM] will reveal only significant delays in the generation of spark discharges that exceed the control value at which the operation of spark plugs is no longer possible. This will require the immediate replacement of the spark plugs, which can lead to a delay in the departure of the aircraft and financial losses.

Closest to the claimed invention is a device [RF patent No. 2614388, 09/14/2015], selected as a prototype, containing a discharge current sensor, a comparison device, a setpoint of the discharge current amplitude voltage control value, a time interval meter, a control signal generator, and the sensor output of the discharge current is connected to the first input of the comparator, the output of the setter of the control value of the voltage of the amplitude of the discharge current is connected to the second input of the comparator, the output of the time interval meter is connected to the control signal generator, the ambient pressure measuring transducer containing the ambient pressure sensor connected in series, the amplifier, ambient pressure control voltage setter, second comparison device, single vibrator, AND logic device, at that the output of the ambient pressure measuring transducer is connected to the first input of the second comparator device the output of the ambient pressure control voltage setter is connected to the second input of the second comparison device, the output of the comparison device is connected to the input of a single vibrator, the output of which, as well as the output of the second comparison device, is connected to the logic device "AND", the output of the logic device "AND" is connected to input of the time interval meter.

A disadvantage of the known device is the impossibility of ensuring sufficient testability of the ignition system, because the decision on the operability of the ignition system is also made only upon the fact that the actual frequency of repetition of spark discharges on the candles exceeds the minimum allowable value and there is no possibility of identifying the onset of the limiting state of wear of the spark plug. This leads to the need to stop the operation of the spark plug and replace it with a new one long before the onset of its limiting pre-failure state.

The task solved by the claimed invention is to increase the depth of control of the technical condition of the capacitive ignition systems of gas turbine engines of aircraft in order to ensure their operation according to the technical condition and reduce the cost of ensuring the life cycle of the engine during the operation phase.

The task is solved by a control device for the capacitive ignition system of gas turbine engines of aircraft, containing a discharge current sensor of the storage capacitor, the first single vibrator, a time interval meter, a control signal shaper, in which the output of the time interval meter is connected to the first output of the control signal shaper, characterized in that in The circuit additionally includes a discharge current sensor of the activator capacitor, a second one-shot, a counter, and the sensor of the discharge current of the activator capacitor is connected to the circuit of the activator capacitor, the output of the discharge current sensor of the storage capacitor is connected to the input of the first one-shot, the output of the first one-shot is connected to the input of the time interval meter and to the input counter reset, the output of the discharge current sensor of the activator capacitor is connected to the input of the second one-shot, the output of the second one-shot is connected to the counting input of the counter, the output of the counter is connected n to the second input of the control signal shaper.

New according to the claimed invention is that the circuit additionally includes a discharge current sensor of the activator capacitor, a second single vibrator, a counter, and the sensor of the discharge current of the activator capacitor is included in the circuit of the activator capacitor, the output of the discharge current sensor of the storage capacitor is connected to the input of the first one vibrator, the output of the first one vibrator connected to the input of the time interval meter and to the reset input of the counter, the output of the discharge current sensor of the activator capacitor is connected to the input of the second one-shot, the output of the second one-shot is connected to the counting input of the counter, the output of the counter is connected to the second input of the control signal shaper.

When the wear of the spark plugs approaches the limit, the breakdown voltage of its spark gap becomes close to the output voltage of the ignition unit. During normal operation of the spark plug, during the breakdown of the switching spark gap, the discharge current of the activator capacitor and the discharge current of the storage capacitor flow through it. In the absence of a spark plug breakdown, the discharge current of the activator capacitor also flows through the switching spark gap, but there is no discharge current of the storage capacitor.

Simultaneous control of the number of discharge pulses of the activator capacitor, designed together with a high-voltage transformer for preliminary breakdown of the spark gap of the spark plug, using the second one-shot and a counter, and control of the time interval between pulses of the discharge current of the storage capacitor using the first one-shot and a time interval meter make it possible to identify the normal operation of the ignition factor and to identify the approach of the spark plug electrode output to the limit, at which the breakdown voltage of the spark gap of the spark plug becomes close to the output voltage of the spark plug. The claimed device allows you to detect this mode of operation of the ignition system and quickly replace the spark plug during the next maintenance of the aircraft without suspending its operation.

In addition, the claimed control device makes it possible to check the condition of the spark plugs in all types of engine start under various conditions in the spark gap zone of the spark plug in terms of pressure and temperature. This provides improved testability of the control device.

In FIG. 1 shows a functional diagram of the configuration of the capacitive ignition system for aircraft engines.

The confole device of the capacitive ignition system contains the first current sensor 9, the second current sensor 7, the first single vibrator 11, the time interval meter 12, the confer signal shaper 13, the second single vibrator 14, the counter 15.

In FIG. 1 also shows the elements of the ignition system: a fan-storing converter 1, a rectifier 2, a storage capacitor 3, a spark gap 4, a galvanic coupling resistor 5, an activator capacitor 6, a high-voltage fan-former 8, and a spark plug 10.

The device works as follows.

During operation of the ignition system, the transistor converter 1 converts the supply voltage into high voltage pulses, which charge the storage capacitor 3 through the rectifier 2 and through the galvanic coupling resistor 5 the activator capacitor 6. When the storage capacitor 3 and the activator capacitor 6 reach a voltage equal to the breakdown voltage of the spark gap 4 , the latter opens, and the process of discharging capacitors begins. Since the capacitance of the activator capacitor 6 is much less than the capacitance of the storage capacitor 3, its discharge occurs much faster, on the order of tens of nanoseconds. When the discharge current of the activator capacitor passes through the primary winding of the high-voltage transformer 8, a high-voltage voltage pulse is generated on its secondary winding, which is added to the storage capacitor voltage. The specified high voltage pulse allows you to initiate the initial breakdown of the spark plug 10, through the charge carrier channel from which the breakdown of the storage capacitor occurs.

When the pulse of the discharge current of the capacitor of the activator 6 passes through the primary winding of the second current sensor 7, a voltage pulse is formed on its secondary winding, upon receipt of which the second one-shot 14 forms a rectangular pulse, which is fed to the counting input of the counter 15, the count of the counter is increased by one.

When the pulse of the discharge current of the storage capacitor 3 passes through the primary winding of the first current sensor 9, a voltage pulse is formed on its secondary winding, upon receipt of which the first one-shot 11 forms a rectangular pulse, which is fed to the input of the time interval meter 12 and the reset input of the counter 15. Interval meter time 12, made, for example, on the basis of an RC circuit, controls not exceeding the time interval between sequential pulses of the discharge current of the control value, which shows the excess of the actual repetition rate of the discharge pulses over the control value.

During normal operation of the ignition system, when the resource of the candles is still far from the limit, the counter reset occurs every time a pulse of the discharge current of the storage capacitor 3 passes, and the counter does not complete the count.

With a significant operating time of the spark plug, its wear limit state (pre-failure state) occurs, at which the breakdown voltage of the spark gap of the spark plug 10 becomes close to the value of the pulse from the high-voltage transformer 8. Due to the fact that the output voltage of the ignition unit has a spread due to the spread of the breakdown voltage of the arrester 4, when the value of the breakdown voltage of the spark gap of the spark plug 10 approaches the value of the pulse from the high-voltage transformer 8, the breakdown can be carried out through several discharge pulses of the capacitor of the activator 6 through the primary winding of the pulse high-voltage transformer 8. In this case, upon receipt of several pulses from the second single vibrator 14 ( depending on the counting module of the selected counter), the counter 15 will complete the counting and will issue a corresponding signal to the control signal generator.

The control signal generator 13, which, for example, can be made in the form of a decoder on the K176ID3 chip, depending on the receipt of signals from the time interval meter 12 and the counter 15 to the inputs A0 and A1, outputs a code at the output that can be used by the engine control system for identification of the state of the ignition system. A control device using a decoder can generate different control signals depending on the state of the inputs:

- at the inputs A0 and A1, logical zeros, a logical unit at the output Y0 of the decoder: "The frequency of the discharge pulses is less than the control value, there are no repeated discharges of the activator capacitor." In this case, it is necessary to stop the operation of the ignition system, identify the failed component (most likely the ignition unit) and replace it;

- at the input A0, a logical unit, at the input A1, a logical zero, a logical unit at the output Y1 of the decoder: "The frequency of the discharge pulses is less than the control value, repeated discharges of the activator capacitor are detected." Corresponds to the full depletion of the spark plugs, at which, due to the delay in the breakdown of the spark plug, the time interval between successive pulses of the discharge current becomes less than the control value. It is necessary to stop the operation of the ignition system and replace the spark plug;

- at the input A0, a logical zero, at the input A1, a logical unit, a logical unit at the output Y2 of the decoder: "The repetition rate of the discharge pulses meets the requirements, there are no repeated discharges of the activator capacitor." This signal corresponds to the normal operation of the ignition system;

- at the inputs A0 and A1, logical units, a logical unit at the output Y3 of the decoder: "The repetition rate of the discharge pulses meets the requirements, repeated discharges of the activator capacitor are detected." Corresponds to the approach of spark plug electrode wear to the limit, the frequency of the discharge current pulses meets the requirements. It is possible to continue the operation of the spark plug with the need to replace it at the next aircraft maintenance.

Obviously, the described control device can also be used to control the operation of a low-voltage capacitive ignition system that does not contain a high-voltage transformer, for example, to control a low-voltage ignition system with semiconductor spark plugs [V.A. Balagurov. Ignition units, M., Mashinostroenie, 1968 (see p. 263)], shown in Fig. 2.

A specific description of the circuit implementation of the functional units of the control device does not require more detailed explanations, because they can be implemented using various well-known typical hardware-circuit constructions, for example, those described in [V.G. Gusev, Yu.M. Gusev Electronics and microprocessor technology - M .: Higher school, 2005 - 790 p.].

Thus, the use of a control device makes it possible to detect the onset of the limiting state of the contacts of the electrodes of the spark plugs for all types of engine start directly in operating conditions (at various combinations of pressure, temperature in the area of the working end of the spark plug, the intensity of filling their spark gaps with the liquid phase of the fuel), which is beneficial distinguishes the proposed control device from the known analogues and prototype.

The claimed device makes it possible to increase the depth of control of the technical condition of capacitive ignition systems of gas turbine engines of aircraft, which makes it possible to ensure the operation of spark plugs according to their technical condition, to reduce the cost of ensuring the life cycle of the engine at the operating stage, to reduce aircraft downtime by replacing spark plugs before they occur. failure state.

Claims (1)

A control device for the capacitive ignition system of gas turbine engines of aircraft, containing a storage capacitor discharge current sensor, a first single vibrator, a time interval meter, a control signal shaper, in which the output of the time interval meter is connected to the first output of the control signal shaper, characterized in that a discharge current sensor of the activator capacitor, a second one-shot, a counter, wherein the sensor of the discharge current of the activator capacitor is connected to the circuit of the activator capacitor, the output of the discharge current sensor of the storage capacitor is connected to the input of the first one-shot, the output of the first one-shot is connected to the input of the time interval meter and to the reset input of the counter, the output of the discharge current sensor of the activator capacitor is connected to the input of the second single vibrator, the output of the second single vibrator is connected to the counting input of the counter, the output of the counter is connected to the second input of the signal generator drove control.

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