RU2830072C1 - Method for forced destruction of rotor shaft during tests of gas turbine engine - Google Patents

Abstract

FIELD: testing.

SUBSTANCE: invention relates to testing equipment, in particular to devices for disengagement of shafts when checking efficiency of protection system against spinning of turbine rotor in case of emergency destruction of turbine rotor shaft. Novelty in the invention is that a wear-resistant element is installed on the forced action element on the shaft of the shaft forced destruction device, which is in contact with the shaft surface at the moment of the engine operation in the mode required for the experiment, wherein shaft destruction is performed by its local heating, which reduces strength properties of shaft material at the point of friction of wear-resistant element of shaft forced destruction device with shaft surface. In order to reduce the time required for the shaft heating by the proposed method to its destruction temperature, before the tests, the shaft is weakened to the minimum acceptable strength margins by means of its mechanical reworking in the planned place of destruction.

EFFECT: allows to eliminate uncertainty with respect to operating mode of turbine (engine), and moment of time, at which it is required to ensure destruction of shaft.

2 cl, 1 dwg

Description

The invention relates to testing equipment, in particular to devices for disconnecting shafts when checking the effectiveness of a system for protecting against the spinning of a turbine rotor in the event of an emergency failure of the turbine rotor shaft.

The verification and confirmation of the main design and technical solutions, the verification of the reliability of the operability of systems and units, the determination of altitude-speed, operational and strength characteristics are carried out on a specially manufactured demonstrator engine. Based on the results of engine testing, if necessary, individual parameters of its units and parts are adjusted by introducing changes to the design, after which the tests are repeated.

In the event of an emergency failure of the shaft connecting the low-pressure compressor to the low-pressure turbine in a dual-circuit turbojet engine, the work performed by the low-pressure turbine and, accordingly, the power developed by the low-pressure turbine can no longer be transmitted to the low-pressure compressor, which will cause an increase in the rotational speed of the low-pressure turbine rotor. In this case, the rotational speed of the turbine rotor may reach a value that is the ultimate strength of one of its disks, as a result of which this disk will fail. The scattering of high-energy parts of the failed disk, as a rule, leads to non-localized damage to the engine, which is unacceptable. Therefore, based on safety requirements, the engine design must exclude the possibility of failure of the turbine disks in the event of failure of its rotor shaft, for which, after the failure of the shaft, the initial failure of the working blades of this turbine and the fastest possible cessation of fuel supply to the combustion chamber must be ensured. This will prevent the destruction of the disk, since the initial destruction of the working blades will limit the possibility of transferring gas energy to the rotation of the rotor, and, consequently, limit the possibility of further increasing its rotation frequency (spin-up), which will also ensure the possibility of timely shutdown of the engine.

Based on the above, the present invention is based on the task of developing a method for the forced destruction of a low-pressure turbine rotor shaft, which makes it possible to simulate an emergency situation during engine operation.

During engine tests related to the operability check of the low-pressure turbine rotor overspeed protection system, the shaft of this rotor is simulated to be destroyed. The most probable place for the shaft of the low-pressure turbine rotor to be destroyed is the area located behind the splined connection of this shaft with the shaft of the low-pressure compressor.

A method is known for cutting and deforming processing of a shaft (patent for invention No. 12693889, filing date 03/14/1985, published 12/20/1995, IPC B24B 39/04) containing cutting and deforming elements.

The disadvantage of this device is that it cannot be used in the design of a gas turbine engine to destroy (disconnect) the rotor shafts during testing due to the lack of the ability to ensure the necessary rigidity of the cutting attachment units and the units for feeding them to the shaft, as well as due to the large dimensions of the device.

A method for disconnecting a fan is known (patent for invention No. 2681392, F01D 21/04, application date 17.06.2015, published 25.07.2018, bulletin No. 21), containing a device that includes a structural element of the “weak link” type, which is destroyed if the maximum value of the torque transmitted through it is exceeded.

The disadvantage of the known device is that the disconnection is an event provided as a reaction to the excess of a certain moment of resistance acting from the gearbox on the turbine shaft. This means that there is a high degree of uncertainty regarding the turbine operating mode at which the device will be triggered during testing, which is due to the difficulty of accurately ensuring specific strength properties of the "weak link" of the device.

The technical result that the invention is aimed at achieving consists in creating a method for forced destruction of a rotor shaft during testing of a gas turbine engine, which makes it possible to eliminate uncertainty regarding the operating mode of the turbine (engine) and the moment in time at which it is necessary to ensure destruction of the shaft.

The technical result is achieved in that the method for forced destruction of the rotor shaft during testing of a gas turbine engine contains a device for forced destruction of the shaft.

What is new in the invention is that a wear-resistant element is installed on the element of forced action on the shaft of the device for forced destruction of the shaft, which contacts the surface of the shaft at the moment of engine operation in the mode required for the experiment, while the destruction of the shaft is carried out by its local heating, leading to a decrease in the strength properties of the shaft material at the point of friction of the wear-resistant element of the device for forced destruction of the shaft with the surface of the shaft.

In order to reduce the time required to heat the shaft using the proposed method to its destruction temperature, before testing, the shaft is weakened to the minimum acceptable strength margins by mechanically finishing it at the planned destruction point.

The proposed method is illustrated by an image of a device for forced destruction of a rotor shaft during testing of a gas turbine engine.

The positions in figure 1 indicate:

1 - device for forced shaft destruction;

2 - rotor shaft;

3 - element of forced influence;

4 - wear-resistant element.

The method of forced destruction of the rotor shaft during testing of a gas turbine engine works as follows.

When assembling the engine for testing, the device 1 for forced destruction of the rotor shaft 2 is mounted inside the intermediate casing of the engine.

During normal operation of the engine, the element of forced action 3 of the device 1 for forced destruction of the shaft 2 on the shaft is maximally displaced in the direction from the engine axis, while the wear-resistant element 4 does not touch the surface of the shaft 2 of the low-pressure turbine rotor.

During engine operation in the mode required for the experiment, element 3 of forced action on shaft 2 is pressed with force by wear-resistant element 4 against the wall of shaft 2 of the low-pressure turbine rotor.

In the friction zone of wear-resistant element 4 and the surface of shaft 2, the temperature increases, which causes a decrease in the strength properties of shaft 2, as a result of which shaft 2 is destroyed. Shaft 2 is destroyed when the temperature in the friction zone reaches a value higher than the limit value of structural strength under specified loads.

Before testing, it is possible to perform mechanical reworking of the planned fracture site to weaken the shaft. Mechanical reworking reduces the shaft cross-section at the planned fracture site. This is done to reduce the time required to heat the shaft to its fracture temperature using the proposed method.

In this case, the strength limit of the material from temperature is determined by the formula:

Where

- material strength limit depending on temperature;

M _kr - torque;

W _кp - moment of resistance to torsion.

Example of implementation of the method.

Tests were carried out on a shaft made of VKS-180 material with an internal diameter d _int = 69.5 mm and an external diameter d _nar = 81 mm.

low-pressure turbines under conditions corresponding to the takeoff mode. The operating temperature of the shaft material during engine operation was 150°C, the shaft temperature in the friction zone during testing was 500°C.

At the same time, the strength limit of the VKS-180 material decreases sharply when the temperature reaches above 350°C.

The anti-spin system was triggered 2 minutes after the wear-resistant element was pressed against the wall of the low-pressure turbine rotor shaft.

Thus, the proposed method of forced destruction of the rotor shaft during testing of a gas turbine engine allows for forced destruction of the rotor shaft during testing of a gas turbine engine, which allows for eliminating uncertainty regarding the moment of shaft destruction.

Claims (2)

1. A method for the forced destruction of a rotor shaft during testing of a gas turbine engine, comprising a forced destruction device for the shaft, characterized in that a wear-resistant element is installed on the element of forced action on the shaft of the forced destruction device, which contacts the surface of the shaft at the time of engine operation in the mode required for the experiment, and the destruction of the shaft is carried out by local heating thereof, leading to a decrease in the strength properties of the shaft material at the point of friction of the wear-resistant element of the forced destruction device with the surface of the shaft. 2. The method according to paragraph 1, characterized in that before conducting the tests, the shaft is weakened by mechanical processing at the planned location of destruction.

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