RU2566806C1 - Method for aircraft engine start by electric starter - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: according to an aircraft engine start method, period of its start is divided into two time intervals. During the first time interval, start is performed by formation of synchronous sequence of voltage half-waves from similar phases of an independent AC source till 10÷20% of rated frequency of the starter-generator is achieved. During the second start time interval, when the value of feed voltage exceeds the value of counter EMF of the starter-generator and mainly in the zone of its amplitude there is shaped asynchronous sequence of discrete current pulses. Amplitude of those pulses shall not exceed maximum allowable current value of the starter-generator, and number of pulses is determined depending on the specified acceleration speed of the rotor of the aircraft engine.

EFFECT: providing high power engineering and acceleration of an aircraft engine till revolutions corresponding to or exceeding synchronous frequency of the starter-generator.

1 dwg

Description

The proposal relates to electrical engineering, in particular to methods for the electric start-up of mid-flight aircraft engines, the output of which are installed alternators for power consumers.

Known methods for the electric start of aircraft engines, the alternating current generator of which is installed at the output of the aircraft engine and is used for inverse motor mode as an electric starter, article "GTU electric start system in operation", authors: Levin A.V., Laptev N.N. in the journal "Gas Turbine Technologies", 2009. The power of such starter-generators is provided from an alternating current network (for example, from an auxiliary power unit) through a semiconductor voltage converter.

The disadvantages of this method of starting an aircraft engine are the design complexity and high overall dimensions of the device for its implementation, since the converters are essentially either a “classic” inverter or, which is almost the same in mass, a valve converter designed for the full power of the starter start.

It should be borne in mind that the electric start-up of a mid-range mid-flight aircraft engine requires approximately 120 ÷ 150 kW of electric power with a start time of 1.5 ÷ 2 minutes, and with an accelerated start, with a start time of 10 ÷ 15 seconds, the required power increases significantly.

There are also known methods of controlling the starter-generator system, which include starting the aircraft engine from an AC power source by putting the generator in the motor (starter) mode using a converter built on the basis of alternating current keys with symmetrical conductivity included in each phase of the starter generator, published application No. 2012125281 of 06/19/2012 for the invention "A method for controlling an alternating current starter-generator system and a device for its implementation", publ. 12/27/2013, bull. Number 36.

The disadvantage of this method of control is its complexity and the difficulty of starting the starter (spin the aircraft engine) to revolutions corresponding to more than 30% of the nominal frequency of the generator. In addition, this starting method provides a pulse-phase control mode of the converter throughout the period of the counter-EMF of the starter-generator, which leads to a deterioration in the energy performance of the starting system as a whole.

The proposed method for the electric start of an aircraft engine is devoid of these drawbacks and allows you to start the marching aircraft engine not only in a simplified way, but also at a higher energy level, including through more efficient use of the power source, and also allows you to spin the aircraft engine to revolutions corresponding to or exceeding the synchronous frequency of the starter generator (for example, in tracking mode).

The purpose of the invention is to simplify the method and increase the efficiency of electric start-up of a mid-flight aircraft engine.

The goal is achieved in the method of electric start of an aircraft engine, the shaft of which is connected with the shaft of the alternating current starter-generator, namely, that the mode of electric starting is provided by supplying to the phase windings of the starter-generator a synchronous sequence of half-waves of voltage from the same phases of an independent alternating current source. The start-up period of an aircraft engine is divided into two time intervals, during the first time interval, the start is carried out by forming a synchronous sequence of half-waves of voltage from the same phases of an independent AC source until 10 ÷ 20% of the rated frequency of the starter-generator is reached, and during the second start-up time interval, at times when the value of the supply voltage exceeds the value of the counter-EMF of the starter generator and mainly in the zone of its amplitude, an asynchronous sequence is formed discrete current pulses. The amplitude of these pulses should not exceed the maximum permissible current value of the starter-generator, and the number of pulses is determined depending on the set acceleration speed of the rotor of the aircraft engine.

In FIG. 1 is a functional diagram of a device illustrating the implementation of the proposed method, where:

1 - driven aircraft engine,

2 - starter generator,

3 - block current sensors,

4 - block keys bilateral conductivity,

5 - independent AC power source,

6 - consumers of AC electricity when the generator is in stationary mode,

7 - a system for generating a synchronous pulse train of control unit 4,

8 - a system for generating an asynchronous (discrete) sequence of control pulses of a unit 4,

9 - node switching frequency control modes,

10 - block allocation of zones in the vicinity of which the control pulses of blocks 7 and 8 are formed,

11, 12 - converters (nodes selection of the first harmonic, respectively, voltage and current in the power supply circuits of the generator 2),

13 - calculator of electromagnetic moment,

14 - programmer (node for setting the current parameters, the frequency of the keys and switching modes, start time, etc. depending on the set acceleration rate of the aircraft engine),

15, 16 - comparison nodes,

17 - frequency sensor,

18 is a control system of the aircraft engine,

19, 20 - power contactor blocks.

The method of electric start of an aircraft engine is as follows. The electric start of an aircraft engine is carried out through the alternating current starter-generator installed on it, by putting it at start-up in the engine starter mode powered by an independent alternating current source, for example, APU (auxiliary power unit) or from a ground-based alternating current source. At the same time, the electric start of an aircraft engine is divided into two intervals in time. In the first time interval of the launch, the aircraft engine is unwound (approximately up to 20 ÷ 25% of the nominal revolutions), for this a synchronous sequence of pulses is created representing a set of half-waves of the supply voltage, depending on the set speed of the aircraft engine spin determined by the software device.

The current in the phases of the generator is regulated by the usual pulse-phase method by changing the turning angles of the power symmetric keys, for example, thyristors.

With such a smooth initial spin of the aircraft engine, the backlash of the power unit box (KSA) of the aircraft engine is selected, and, therefore, a “blow” to the transmission of the aircraft engine is prevented.

The second interval of the aircraft engine start-up time is fundamentally different from the first interval in that instead of a synchronous sequence of current pulses in the phases of the starter-generator, an asynchronous sequence is formed, the peculiarity of which is the formation of discrete current pulses, the amplitude of which is limited almost exclusively by the internal resistance of the phase of the starter-generator, pulse-phase regulation of symmetrically conductive keys can be excluded, and the speed of the aircraft engine spin is determined only number of discrete pulses. Moreover, as indicated above, the amplitude of the discrete current pulses is commensurate with the maximum permissible current of the starter-generator, which usually should be at least three times the rated load current of the starter-generator.

The device of FIG. 1, shown to illustrate the operation of the proposed method for electric start of an aircraft engine, operates as follows.

Aircraft marching engine 1 drives the starter-generator 2 of alternating current, to the output of which consumers of electricity are connected through the block of power contactors 19. If necessary, the starter-start of the aircraft engine 1 from an independent source of electricity 5, which can be the APU on board an aircraft the power source when starting on the ground, the power contactors 19 disconnect the load, and the starter-generator 2 is connected through the block of power contactors 20, the block of current sensors 3, bl ok, keys of two-sided conductivity 4 to the power source 5. At the same time, the signal from the aircraft engine control system 18 receives signals, in particular, corresponding to the moment of inertia and the moment of load, to the programmer 14, which sets the start time, the frequency of operation of the block of keys of two-sided conductivity 4, phase current, etc., receiving real information about the value of the system parameters from the calculator 13, to the input of which information is provided on the magnitude of the current, EMF and frequency of the starter-generator, and signals are generated at the output of the calculator 13 about the real value of the electromagnetic moment of the starter generator.

Moreover, given the large degree of distortion of the current and voltage in the phases of the starter generator 2, the calculation of all necessary parameters is carried out according to the main harmonics of the current and voltage, for which the output of the current sensor blocks 3 and the output of the starter generator 2 are connected to the voltage converters 11 and current 12 at the output of which signals are generated proportional to the first harmonics of the voltage and active current, respectively, fed to the input of the calculator of electromagnetic moment 13.

At the same time, the signals from the voltage converter 11 and the current converter 12 are fed to one input of the comparison node 15, and the signal from the programmer 14 is received at the other input of this node. The output of the comparison node 15 is connected to the inputs of the formation systems 7 and 8, which form a synchronous and asynchronous sequence, respectively pulses of control of keys of two-sided conductivity of block 4. The output of voltage converter 11 is additionally connected with the block for identifying zones for switching on power switches of block 4, and if the value exceeds If an independent power source is 5, the counter-EMF value of the starter-generator 2, block 10 generates enable signals, respectively, to the formation systems 7 and 8. The formation of the switching signals of the operating modes of the formation systems 7 and 8 in time is determined by the programmer 14 using the mode switching unit 9, and the frequency itself the arrival of pulses to the keys of block 4 is determined by the comparison node 16, on one input of which a signal in frequency from the corresponding frequency sensor 17 of the starter-generator is received, and on the other - output in frequencies e of the programmer 14, which determines the magnitude and rate of change of the frequency of starting the aircraft engine, for which the output of the comparison node 16 is associated with the inputs of the formation systems 7 and 8, respectively.

Thus, by dividing the start-up period of the aircraft engine into two time intervals, the electric launch engine is launched in a more simplified manner, and its launch efficiency is significantly increased.

Claims (1)

The method of electric start-up of an aircraft engine, the shaft of which is connected with the shaft of an alternating current starter-generator, which means that the electric-start mode is provided by applying to the phase windings of the starter-generator a synchronous sequence of half-waves of voltage from the same phases of an independent alternating current source, characterized in that the starting period of the aircraft engine is divided into two time intervals, during the first time interval, the launch is carried out by forming a synchronous a sequence of half-waves of voltage from the same phases of an independent source of alternating current until 10 ÷ 20% of the rated frequency of the starter-generator is reached, and during the second start-up time interval, when the magnitude of the supply voltage exceeds the value of the counter-emf of the starter-generator and mainly in the zone of its amplitude, asynchronous sequence of discrete current pulses, and the amplitude of these pulses should not exceed the maximum permissible current value of the starter-generator, and the number of pulses is determined elyaetsya depending on the target acceleration speed rotor aircraft engine.