Method for detecting gas generator shaft fracture in gas turbine engines using the ngdot PS3dot / ngdot ratio method

Abstract

The invention relates to a method for detecting shaft fracture by the Ngdot and Ps3dot / Ngdot ratio method in gas turbine engines in fracture cases that cannot be detected via shaft speed data.

Description

[0001] Specification

[0002] METHOD FOR DETECTING GAS GENERATOR SHAFT FRACTURE IN GAS TURBINE ENGINES USING THE NGDOT PS3DOT / NGDOT RATIO METHOD

[0003] Technical Field

[0004] The invention relates to gas turbine engines.

[0005] In particular, the invention relates to detecting gas generator shaft fracture in gas turbine engines using the Ngdot and Ps3dot / Ngdot ratio method in fracture cases that cannot be detected via shaft speed data.

[0006] Background of the Art

[0007] At present, shaft fracture detection in gas turbine engines is performed using speed / RPM (revolutions per minute) data measured from the shaft. Depending on the location of the speed sensor, fracture detection cannot be performed for all shaft fracture locations when the speed sensor remains on the decelerating side.

[0008] Within the scope of CS-E 850, which is one of the gas turbine engine certification requirements, a failure occurring in the engine shaft system must be mitigated within the engine before leading to hazardous effects or disk burst.

[0009] In the existing art, due to the limited ambient temperature range in which speed sensors can operate, there is difficulty in determining a location for adding a second sensor. For a second speed sensor, an accessible location is required in terms of replaceability. When multiple speed sensors are compared, an increase in terminal speed value occurs due to control system delays.

[0010] In the existing art, there are also difficulties related to sensor placement, uncertainties in validation processes / methods, cost impacts, and potential effects on engine control system design.

[0011] In the existing art, the invention numbered US2003131605 (A1) titled “Adaptive acceleration schedules for gas turbine engine control systems” discloses an engine surge avoidance system and method that adapts acceleration schedules (i.e., P2.5bleed valve and NGDOT) to prevent surge events while minimizing decreases in engine response time. The surge avoidance system and method disclosed herein achieves this objective by optimally adapting both NGDOT and P2.5 bleed schedules.

[0012] In the existing art, the invention numbered RU2703581 (C1) titled “Method for Shutting Down an Engine in the Event of Turbine Rotor Fracture” relates to multishaft gas turbine engines (GTE) for aircraft and ground applications. In the method for shutting down the engine in the event of turbine rotor fracture, in which the need to shut down the engine and reduce fuel supply is determined, unlike the prior art, in all engine operating modes, the axial force acting on the ball bearing and the vibration characteristics in the turbine section of the engine are considered and measured; subsequently, during normal engine operation, the axial force on the ball is measured and compared with the previously measured value; if these values do not correspond to reduced fuel supply, as a result, the engine operating mode is reduced to low throttle. Vibration characteristics are measured in the turbine area, compared with previously measured values, and, if exceeded, fuel supply to the combustion chamber is cut off. The technical result aimed to be achieved by the invention is to increase the operational reliability of the GTE by applying the shutdown method in the turbine. In addition to shaft fracture, the application area of this method can be extended to other GTEs.

[0013] In the existing art, the invention numbered CN112443508 (A) titled “Overvoltage detection method for turbofan engine and system” provides a surge detection method for a turbofan engine. In the surge detection method, a representative rotational speed N2R0 of a high-pressure rotor, a first-order time derivative N2dot of the physical rotational speed of the high-pressure rotor, a compressor outlet pressure Ps3 of a high-pressure compressor, a first-order time derivative Ps3dot of the compressor outlet pressure of the high-pressure compressor, and a second-order time derivative Ps3dotdot of the compressor outlet pressure of the high-pressure compressor are obtained; and a surge evaluation index A = SG1 * (v1 + SG2 * (v2 + SG3 * v3 + SG4 * v4)) is calculated in real time, and it is determined that the surge occurs when A is greater than a specified threshold Ath. The invention further provides a surge detection system for implementing the surge detection method. Thesurge detection method can achieve the purpose of detecting surge of the turbofan engine in real time.

[0014] In the existing art, the invention numbered RU2406848 (C1) titled “Connection Between Turbine and Compressor Rotors of a Gas Turbine Engine” discloses a proposed connection comprising compressor and low-pressure turbine shafts that are axially connected via an intermediate shaft and a coupling sleeve mounted inside the intermediate shaft and screwed onto the low-pressure turbine shaft, and radially connected via a splined connection. It also includes a radial thrust bearing whose outer race is mounted on the inner surface of the high-pressure turbine shaft and whose inner race is mounted on the outer surface of the intermediate shaft. A nut contacting the low-pressure compressor rotor, which is connected to the low-pressure compressor shaft via an additional splined joint on the coupling sleeve, is provided. Compressor shaft fracture is localized within the engine, thereby preventing destruction of the engine and the aircraft.

[0015] Summary of the Invention

[0016] An object of the invention is to eliminate the disadvantages of the prior art by detecting gas generator shaft fractures in gas turbine engines using existing engine sensors and ensuring compliance with CS-E 850.

[0017] Another object of the invention is that shaft acceleration (Ngdot) can be obtained via the gas generator shaft speed (Ng) sensor. In the event of shaft fracture, it has been determined that the shaft acceleration behavior can be distinguished from engine shutdown, flameout, and deceleration dynamics, but conditions may occur under which it cannot be distinguished from surge behavior. Compressor outlet pressure time-dependent change (Ps3dot) can be obtained from compressor outlet pressure (Ps3). In the event of shaft fracture, by using, in addition to shaft acceleration, the ratio of Ps3dot to Ngdot (Ps3dot / Ngdot), engine parameters that can be distinguished from engine dynamics such as engine shutdown, flameout, deceleration, and surge can be obtained.Another object of the invention is that, in the event of a shaft fracture where the speed sensor remains on the decelerating side, the speed sensor measures a decreasing value. In shaft fracture detection studies performed using shaft speed value, it has been observed that the fracture condition cannot be distinguished from engine dynamics such as engine shutdown, flameout, deceleration, and surge, and cannot be made independent of platform-dynamics-related variables. The use of the method of the derivative of the speed sensor (Ngdot) and the ratio of the derivative of compressor outlet static pressure to the derivative of the speed sensor (Ps3dot / Ngdot) has shown that shaft fracture is distinguishable from engine dynamics and can be made independent of platform dynamics variables.

[0018] Another object of the invention is to enable detection of shaft fracture through the character of the derivative of the speed sensor (Ngdot) and the ratio of the derivative of compressor outlet static pressure to the derivative of the speed sensor (Ps3dot / Ngdot) without the need for an additional sensor solution.

[0019] Another object of the invention is that no additional sensor requirement is needed since detection is performed using existing engine sensors.

[0020] Another object of the invention is to eliminate mechanical design difficulty since there is no need to prevent shaft fracture from leading to hazardous engine effects through mechanical methods.

[0021] Another object of the invention is to provide an advantage in terms of ease of validation testing.

[0022] Brief Description of the Drawings

[0023] Figure 1 is an algorithm flow diagram of the method subject to the invention, Figure 2 is a view of turbine shaft fracture locations,

[0024] Figure 3 is a deceleration acceleration graph observed during shaft fracture and engine maneuvers,

[0025] Figure 4 is a graph showing that shaft fracture can be distinguished from surge by using the Ps3dot / Ngdot ratio.Description of Reference Numerals

[0026]

[0027] Detailed Description of the Invention

[0028] The invention is a method for detecting gas generator shaft fracture in gas turbine engines using the Ngdot and Ps3dot / Ngdot ratio method in fracture cases that cannot be detected via shaft speed data. Ngdot and Ps3dot / Ngdot are generally terms used in the field of computer science and data analysis. This term refers to a form of notation used in the representation of a particular data structure or algorithm.

[0029] In the implementation of the method subject to the invention, the following process steps are applied:

[0030] • Shaft fracture detection step (100): when a shaft fracture occurs in the engine in which the speed sensor remains on the decelerating side, the speed of the decelerating part is measured by the speed sensor,

[0031] • Definition of engine shutdown threshold value step (200): during shaft fracture, the time-dependent changes of shaft speed and compressor static pressure are defined as a threshold limit value for the engine. This threshold value will be distinguishable from engine and platform dynamics.

[0032] • Controller signal processing and validation step (300): in order to detect that the engine has reached the defined limit value, the controller continuously monitors the Ngdot and Ps3dot / Ngdot values, and when it detects that the threshold limit value has been reached, it processes and validates the signal and transmits a signal for activating the emergency valve,Emergency valve closure step (400): the emergency valve is activated, the fuel supplied to the engine is cut off, and the shaft is decelerated before the engine reaches disk burst speed.

[0033] In Figure 2, turbine shaft fracture locations are shown. If the shaft (1 , 2, 3), which keeps the compressor and turbine structure together on the same plane, fractures at these stations, the speed sensor (4) will remain on the decelerating side. Since the speed sensor (4) remains on the decelerating side, triggering the emergency valve based on the speed value is not possible.

[0034] If the gas generator shaft of the gas turbine engine reaches a pre-defined Ngdot and Ps3dot / Ngdot value, the controller will determine that the shaft has fractured and will shut down the engine by activating the emergency valve. In order to apply this method, the Ngdot and Ps3dot / Ngdot value must be clearly distinguishable from flameout, surge, engine shutdown, and sudden pilot maneuver.

[0035] In Figure 3, the deceleration acceleration that an example engine gas generator shaft can reach during maneuvers under normal operating conditions and during shaft fracture is shown.

[0036] As can be seen in Figure 4, due to the Ps3dot / Ngdot method, shaft fracture can be distinguished from surge. The condition in which the shaft decelerating with an acceleration above the pre-defined deceleration limit value simultaneously reaches a value above the limit value determined for Ps3dot / Ngdot will be detected as shaft fracture.

[0037] Due to high vibrations that may occur after gas generator shaft fracture, reliable information may not be obtained from the Ng speed sensor and Ps3 pressure sensor. It must be verified by tests in order to decide on the applicability of this detection method.

Claims

CLAIMS1. A method for detecting shaft fracture by the Ngdot and Ps3dot / Ngdot ratio method in gas turbine engines in cases where fracture cannot be detected via shaft speed and acceleration data when the shaft (1 , 2, 3) fractures at these stations, characterized in that it comprises:- a shaft fracture detection step (100);- a definition of engine shutdown threshold value step (200);- a controller signal processing and validation step (300);- an emergency valve closure step (400).

2. The shaft fracture detection step (100) according to Claim 1, characterized in that it includes measuring, via the speed sensor (4), the speed of the decelerating part when a shaft fracture occurs in the engine in which the speed sensor (4) remains on the decelerating side.

3. The definition of engine shutdown threshold value step (200) according to Claim 1 , characterized in that it includes defining the Ngdot and Ps3dot / Ngdot ratio as a threshold limit value for the engine during shaft fracture.

4. The controller signal processing and validation step (300) according to Claim 1 , characterized in that, in order to detect that the engine has reached the defined limit value, the controller continuously monitors the Ngdot and Ps3dot / Ngdot value, and when it detects that the threshold limit value has been reached, it processes and validates the signal and transmits a signal for activating the emergency valve.

5. The emergency valve closure step (400) according to Claim 1, characterized in that it includes cutting off the fuel supplied to the engine by activating the emergency valve and decelerating the shaft before the engine reaches disk burst speed.

6. The method according to Claim 1, characterized in that, when the shaft separates from station (1, 2, or 3), the speed sensor (4) remains on the decelerating side.

7. The method according to Claim 6, characterized in that, since the speed sensor (4) remains on the decelerating side, it is not possible to trigger the emergency valve based on the speed value.

Images