RU2221157C1 - Method of and device for starting aircraft high-by-pass ratio turbojet engine - Google Patents

Abstract

FIELD: aircraft industry. SUBSTANCE: invention relates to aircraft engines, namely, to double-flow turbojet engines with high-by-pass ratio at tail wind. According to proposed method, prior to starting the engine, fan speed is measured and result obtained is compared with reference value, passage part of engine is closed by reverser assembly and when fan speed is less than preset reference value, engine starting system is switched on. Engine starting system contains logic unit which compares value of reverse speed with reference value and generates control signals according to logic algorithm and fan measuring unit and fan sense of rotation detection unit, these units being connected with air-craft computer. When engine starting reaches final phase, after delivery of starting fuel, reverser assembly is set into cruise position. Proposed method of starting of aircraft double- flow turbojet engine with high-by-pass ratio at tail wind and device for implementing the method make it possible to remove limitations as two rear wind and exclude delays of flights and ahead-of-schedule removals of engine from aircraft caused by gas- dynamic instability at engine starting. EFFECT: prevention of abnormal operation of engine at starting. 3 dwg, 2 dwg

Description

 The invention relates to the field of aircraft engine manufacturing.

 The problem of starting engines when the rear wind is relevant for all types of turbofan engines with a large degree of bypass, especially twin-shaft. This is due to the fact that during the start-up process under these conditions there is often a violation of the gas-dynamic stability of the engine, causing an increase in the temperature of the gases in front of the turbine and, as a result, stopping the launch, delaying the flight, and often early removal of the engine from the aircraft.

 This problem is due to the fact that when the wind behind the fan starts to work like a turbine and spins the low pressure rotor in the opposite direction to the calculated direction of rotation. The frequency of the opposite rotation is determined by the wind speed.

 In the opposite rotation, the low-pressure turbine (LPH) operates in the compressor mode (Proceedings of the American Society of Mechanical Engineers, "Energy Machines and Installations", Vol. 100, 1, 1978, pp. 26-34, Bammert, Zener, "Experimental Determination of Air turbines at positive and negative speeds of rotation (in four quadrants) "). The high pressure pump sucks in air from the nozzle and pumps it into the combustion chamber. This leads to the appearance of a "reverse" pressure drop across the turbine of the gas generator. Therefore, when starting the engine in wind conditions from behind, the actual starting line after ignition of the combustion chamber flows above the calculated one. Stocks of stable operation are reduced and, at a certain critical value of the wind speed, they completely disappear from behind - a violation of gas-dynamic stability occurs.

 An increase in the stability reserves of the high-pressure compressor (HPC) in the start-up modes by reprofiling the compressor blades, additional air exhaust from the intermediate stages of the HPC or additional regulation with the help of rotary blades of the HPC guide vanes, as well as an increase in the available power of the starting device, do not solve this problem. Therefore, when operating engines on an airplane, restrictions are imposed on the magnitude of the wind speed blowing from behind, at which engine start is allowed.

The "Manual on the technical operation of the engine PS-90A, 94-00-807 OM, 1990, book 1, section 072.00.00, paragraph 5.31.2, p. 38" is known, which gives instructions that the engine is allowed to start, if the associated wind component does not exceed 5 m / s, and engine operation in place is allowed at a wind speed not exceeding the values:
lateral component - 15 m / s
associated component - 5 m / s
Therefore, when the wind exceeds these limits, engine operation is not allowed, since a fan can breakdown, which becomes a surge, and failure to comply with these restrictions leads to a violation of the gas-dynamic stability of the engines and, as a rule, early removal of them from the aircraft.

 The closest technical solution chosen for the prototype is the "Aircraft engine abnormal warning system", US patent 4.908.618 of March 13, 1990, class. 340/945, which warns the crew of the aircraft about abnormal engine operation in the area below idle. The system is based on the use of parameters characterizing the operation of aircraft engines: gas temperature behind the turbine, rotor speed, air temperature, reduced air speed relative to the aircraft.

 The disadvantage of this system is that it registers abnormal engine operation as an accomplished fact and informs the aircraft crew about it.

 The objective of the proposed technical solution is to eliminate the conditions for the occurrence of abnormal engine operation at startup.

 The technical result is achieved by the fact that in the method of starting an aircraft dual-circuit turbojet engine (turbofan engine) with a large bypass ratio, in which the engine starting system is turned on, before starting the engine with a wind blowing from behind, the fan speed and the direction of rotation are determined, compared with control values , block the engine’s flow part with a reverse device and, when the fan speed reaches an acceptable value, turn on the engine start system, and when the engine speed has reached the final phase after the starting fuel has been supplied, the reverse device is moved to the marching position, and also because the device for starting an aircraft dual-circuit turbojet engine (TRDD) with a large bypass ratio, containing an engine starting system, is equipped with a logic unit and a frequency determination unit and the direction of rotation of the fan, while the unit for determining the frequency and direction of rotation of the fan contains a first driver of single pulses, a second driver of unity ary pulses, the first counter pulse sequence, the second counter pulse sequence of high frequency pulse generator, a comparison unit and a block relationship, and logical unit and determining the frequency and direction of rotation of the fan connected with the onboard computer.

 Figure 1 shows a diagram of a device for starting an aircraft dual-circuit turbojet engine (turbofan) with a large degree of dual-circuit when the wind blowing from behind, and the algorithm for generating commands.

 In FIG. 2 shows a block diagram for determining the frequency and direction of rotation of the fan.

The device for starting an aircraft dual-circuit turbojet engine (TRDD) with a large bypass ratio when the wind blows from behind, and the algorithm for generating commands in figure 1 consists of a unit 1 for determining the frequency and direction of rotation of the fan and a logical unit 2, which compares the value of the frequency of the reverse direction of rotation of the fan with a control value and generates control signals in accordance with the embedded logical algorithm:
- if the direction of rotation of the fan is calculated or the value of the frequency of rotation of the fan in the opposite direction is less than the specified control value, the logic unit 2 generates a control signal to turn on the engine start system;
- if the value of the fan speed in the opposite direction is greater than the specified control value, the logic unit 2 generates a control signal for setting the reversing device to the operating position;
- if the reverse device is installed in the working position and the fan speed in the opposite direction is less than the specified control value, the logic unit 2 generates a control signal to turn on the engine start system;
- if the reverse device is installed in the operating position and the engine start has reached the final phase after the starting fuel has been supplied, the logic unit 2 generates a control signal for shifting the reverse device to the marching position.

 Block 1 for determining the frequency and direction of rotation of the fan in figure 2 contains the first driver 3 unit pulses, the second driver 4 unit pulses, the first counter 5 pulses of high frequency, the second counter 6 pulses of high frequency, generator 7 pulses of high frequency, block 8 comparison, block 8, block 9 relationships.

At the same time, the unit 3 and 4 unit pulses are located on the fan so that the pulse generated by the second unit 4 pulses is formed when, in the calculated direction of rotation, the fan rotates by an angle of less than 180 ^o after the pulse generated by the first unit 3 pulses. The first driver 3 unit pulses includes two counters 5 and 6 pulses, the inputs of which are fed a continuous sequence of pulses from the generator 7 of the high frequency. The second driver 4 unit pulses turns off the second counter 6 pulses. A repeated pulse from the first driver 3 unit pulses turns off the first counter 5 pulses. After turning off both counters 5 and 6 pulses, the resulting value of the number of pulses from counter 5 is supplied to the comparison unit 8 and to the ratio unit 9, and the resulting value of the number of pulses from the counter 6 is supplied to the ratio unit 9. Block 8 comparison compares the frequency value of the opposite direction with the control value. The ratio unit 9 divides the number of pulses registered by the counter 6 by the number of pulses registered by the counter 5. A signal ratio of less than 0.5 indicates the calculated direction of rotation of the fan, and more than 0.5 indicates the opposite direction of rotation of the fan. The signals from the comparison unit 8 and the relationship unit 9 are then fed to a logic unit 2, which compares the reciprocal of the fan speed with a control value and generates control signals in accordance with the embedded logic algorithm.

 The method of starting an aircraft dual-circuit turbojet engine (turbofan) with a large degree of dual-circuit when the wind blowing from behind, is as follows.

 First, the frequency and direction of rotation of the fan caused by the wind is determined, then the reverse part of the engine is blocked by the reverse device, thus, the reverse device prevents the opposite direction of rotation of the fan and the appearance of a “reverse” drop on the gas generator turbine in any direction of wind. After the fan speed in the direction opposite to the operational direction of rotation, becomes less than the specified reference value, the engine is started. And when the engine start has reached the final phase, after supplying the starting fuel, the reversal device is shifted to the marching position.

 Thus, the proposed method of starting an aircraft dual-circuit turbojet engine (turbofan) with a large degree of dual-circuit when the wind blowing from behind, and a device for its implementation can remove restrictions on the amount of wind blowing from behind, eliminate flight delays and early removal of engines from the aircraft due to gas-dynamic instability when starting engines.

Claims (3)

1. The method of starting an aircraft dual-circuit turbojet engine (turbojet engine) with a large bypass ratio, which include starting the engine, characterized in that before starting the engine with a wind blowing from behind, determine the fan speed and direction of rotation, compare with control values, they block the engine’s flow part with a reverse device, and when the fan speed reaches an acceptable value, the engine start system is turned on, and when the engine starts to reach The advanced phase, after supplying starting fuel, the reversing device is moved to the marching position. 2. A device for starting an aircraft dual-circuit turbojet engine (turbofan engine) with a large bypass ratio, comprising an engine starting system, characterized in that it is equipped with a logic unit and a unit for determining the frequency and direction of rotation of the fan, while the unit for determining the frequency and direction of rotation of the fan contains the first single pulse shaper, second single pulse shaper, first pulse train counter, second pulse train counter, gene high frequency pulse generator, comparison unit and ratio unit. 3. The device according to claim 2, characterized in that the logic unit and the unit for determining the frequency and direction of rotation of the fan are connected to the on-board computer.

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