Method for monitoring pitch diameter vibration of turbine disc of liquid rocket engine

Abstract

The invention relates to a liquid rocket engine turbine disc pitch diameter vibration monitoring method, and belongs to the technical field of liquid rocket engine testing. According to the invention, high-frequency speed pressure sensors are additionally arranged at front and rear cavity parts at two sides of the turbine disc, and high-frequency pressure pulsation of fluid near the turbine disc is measured in real time, so that the pitch diameter vibration inherent frequency and the vibration magnitude of front and rear traveling wave frequencies of the monitored turbine disc in the high-temperature and high-rotating-speed operation process are obtained; therefore, a basis is provided for health judgment of the working state of the turbine pump after test run. The method can accurately reflect the pitch diameter vibration level of the thermal test rocket engine turbine disc, has high sensitivity, and solves the problem that the local vibration frequency of the rotor turbine disc is not easy to monitor during the vibration of a traditional turbine pump shell.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid rocket engine testing and relates to a method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk. Background Art

[0002] In liquid rocket engines, the turbine rotates and generates power, driven by combustion gases, to power the pump. Most turbine blades operate under extremely harsh conditions of high temperature, high pressure, and high speed. As engine performance improves, increasingly stringent requirements are placed on the turbine blade structure, leading to increasingly prominent vibration issues, seriously impacting the structural integrity and reliability of the blades and, ultimately, the engine as a whole. In open-cycle liquid rocket engines, to minimize the mass flow of the driving fluid and simplify the structure, the turbine pressure drop ratio is typically between 10 and 25, resulting in high flow velocities within the turbine blade cascade, typically operating under supersonic conditions. In hydrogen-oxygen rocket engines, the turbine driving fluid is typically hydrogen-rich fuel gas, with a gas constant R approximately eight times that of hot air, resulting in greater power generation. Even with Mach numbers exceeding Mach 2 within the turbine flow path, there is a risk of turbine disc pitch vibration.

[0003] Directly measuring dynamic parameters such as turbine disk vibration and strain is extremely difficult due to the limited space and harsh temperature environment within a turbopump. No relevant reports have been reported domestically or internationally. Turbine disk pitch vibration is a localized, self-limiting vibration of the rotor, with weak energy transfer. During this energy transfer, it is gradually blocked by bearings, elastic supports, and dampers, further significantly attenuating the vibration signal. Traditional casing vibration measurements during hot runs are difficult to measure turbine disk pitch vibration. If it is detected, the magnitude is often significant, and the rotor structure cannot withstand the significant dynamic stress, leading to emergency shutdowns or deflagrations. Summary of the Invention

[0004] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and propose a method for monitoring the pitch diameter vibration of a liquid rocket engine turbine disk.

[0005] The technical solution of the present invention is: a method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk, the specific steps of which are as follows:

[0006] A high-frequency velocity and pressure sensor is installed in the engine turbine disc cavity to ensure that it can directly contact the high-temperature gas mainstream area;

[0007] The turbine disc generates local pitch vibration, which is transmitted to the gas flow vibration in the front and rear cavities of the turbine disc cavity. The high-frequency pulsation pressure value of the gas is measured by a high-speed pressure sensor.

[0008] The signal feature extraction and processing of the measured high-frequency pulsation pressure value of the gas is performed to obtain the frequency and amplitude of the fluid pressure pulsation in the turbine disc cavity. Combined with the structural parameters of the turbine disc, the vibration amplitude and frequency of the turbine disc pitch diameter are obtained.

[0009] The pitch vibration magnitude of the turbine disk is obtained based on the pitch vibration amplitude and frequency of the turbine disk. The working status of the turbine disk is monitored in real time based on the vibration magnitude, and the health status of the turbine disk structure after the test run is evaluated.

[0010] Furthermore, there are at least two high-frequency velocity and pressure sensors, which are installed in the front cavity of the turbine disk and the rear cavity of the turbine disk respectively.

[0011] Furthermore, the pulsation measurement frequency of the high-frequency velocity pressure sensor is 0 to 50,000 Hz and is adapted to a working environment temperature of 900K.

[0012] Furthermore, the high-frequency velocity and pressure sensor is fixed on the turbine housing through a mounting structure.

[0013] Furthermore, the mounting structure includes a base, a sleeve, and a sealing gasket; the base is fixed on the turbine casing; the high-frequency velocity pressure sensor is extended into the base and fixed, a sealing gasket is arranged between the bottom and the base, and the head is extended to directly contact the gas medium; the sleeve is located between the high-frequency velocity pressure sensor and the base, the outer side of the sleeve is connected to the base, the inner side of the sleeve presses the high-frequency velocity pressure sensor, and the sleeve and the base are anti-loosening treated.

[0014] Furthermore, the sealing gasket is a metal gasket and is loaded by torque.

[0015] Furthermore, the anti-loosening treatment is to apply glue between the base and the sleeve and set a fuse.

[0016] Furthermore, short-time Fourier transform is used to extract the signal features of the measured high-frequency pulsation pressure value of the gas to obtain the turbine disk cavity fluid pressure pulsation frequency f and amplitude A, and combined with the turbine disk structural parameters, the turbine disk pitch diameter vibration frequency and vibration amplitude A' are obtained.

[0017] Furthermore, the pitch vibration frequency of the turbine disk includes the natural frequency f0, the forward wave frequency f1, and the backward wave frequency f2 measured from the front and rear cavities.

[0018] Furthermore, the turbine disk pitch diameter vibration amplitude A' includes the front cavity vibration amplitude A'1 and the rear cavity vibration amplitude A'2. When both exceed the threshold value of 0.01 MPa, the turbine disk pitch diameter vibration magnitude is quantitatively determined.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] (1) The present invention monitors the gas pressure pulsation in real time by installing high-frequency velocity and pressure sensors in the actual space in front and rear cavities of the turbine disc, which can accurately reflect the pitch vibration level of the hot test and has high sensitivity, thus overcoming the difficulty of measuring the local vibration frequency of the rotor turbine disc due to the vibration of the traditional turbine pump housing.

[0021] (2) The present invention adopts a miniaturized high-speed pressure sensor and a special fixing structure, which can be flexibly installed according to the actual allowable space and working environment inside the turbine pump, and is adaptable to ultra-low temperature and ultra-high temperature working environments, and can accurately, quantitatively and in real time reflect the actual vibration state of the turbine disk. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the turbine disk pitch diameter vibration monitoring method;

[0023] Figure 2 This is a schematic diagram of the installation of a high-frequency speed and pressure sensor;

[0024] Figure 3 Schematic diagram of turbine disk pitch diameter detection. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] The present invention discloses a method for detecting pitch diameter vibration of a liquid rocket engine turbine disk, which can monitor the high-temperature gas pressure pulsation on both sides of the turbine disk of a turbopump in real time. A high-frequency pressure sensor is used to measure the gas pressure pulsation to obtain the pitch diameter vibration level of the turbine disk, which can accurately reflect the pitch diameter vibration magnitude of the hot test. It has high sensitivity and overcomes the problem that the traditional turbine pump housing vibration measurement cannot measure the local vibration frequency of the rotor turbine disk. It monitors, diagnoses and evaluates the real-time working status of important components of the turbopump. The specific steps are as follows: Figure 1 As shown:

[0027] a. Install high-frequency speed and pressure sensors in the front and rear cavities of the engine turbine disc

[0028] High-frequency velocity and pressure sensors are common measurement devices in this field and can be selected based on monitoring requirements. In this solution, a high-frequency velocity and pressure sensor with a pulsation measurement frequency of 0 to 50,000 Hz and adapted to high-temperature operating environments of 900 Kelvin is selected. This sensor fully covers the measurement requirements for turbine disk structure vibration.

[0029] The location, number, and installation method of the measurement points are determined based on the structural characteristics of the turbine disc's front and rear cavities. In this invention, at least one high-frequency velocity and pressure sensor is installed within the available space within the turbine disc's front and rear cavities. The installation method involves designing a mounting structure compatible with the high-frequency velocity and pressure sensor, securing it with the mounting structure to ensure direct contact with the high-temperature gas mainstream.

[0030] like Figure 2 As shown, the high-frequency velocity pressure sensor mounting structure includes a base 2, sleeve 3, sealing gasket 4, housing 5, and fuse 6. The base 2 is designed based on its structural characteristics, with holes drilled in the housing 5 at the measuring point. The high-frequency velocity pressure sensor base 2 and housing 5 can be connected by welding, a process performed directly during the parts processing. The high-frequency velocity pressure sensor 1 is inserted into the sensor base 2 for fixation, ensuring that the sensor head 1 extends out and directly contacts the gas medium. The high-frequency velocity pressure sensor 1 and base 2 are connected and compressed by the sleeve 3, which is connected to the base 2 via threads and glued to prevent loosening. A sealing gasket 4 is placed between the high-frequency velocity pressure sensor 1 and the base 2 for sealing.

[0031] The high-frequency velocity pressure sensor base 2 consists of a hexagonal structure and a cylinder, which are connected to each other; the cylinder is welded to the shell 5, and the bottom of the high-frequency velocity pressure sensor 1 is pressed and sealed with the end face of the cylinder of the base 2 close to the shell through the sealing gasket 4.

[0032] The sealing gasket 4 is a metal gasket adapted to high temperature environments, which is loaded by torque to achieve sealing under high temperature gas.

[0033] The base 2 and the sleeve 3 are respectively provided with a safety hole and are connected via a fuse 6 .

[0034] The detection object and installation position of the sensor can be flexibly selected according to actual needs, and is suitable for turbine pumps of various structures.

[0035] b. Turbine disc pitch vibration, turbine disc cavity fluid vibration

[0036] like Figure 3 As shown, the high-temperature and high-pressure combustion gas 13 flows through the moving and stationary blades of the turbine disk 14, driving the turbine pump rotor to rotate, so that the pump chamber fluid obtains high-pressure fluid through the impeller to perform work, and enters the thrust chamber for combustion. During the rotation process, the turbine disk 14 may experience modal vibrations such as local pitch diameter, and the vibration is transmitted to the combustion gas in the turbine disk front cavity 15 and the turbine disk rear cavity 10.

[0037] c. Measure high-frequency pressure pulsation parameters through high-speed pressure sensor

[0038] Two high-frequency pressure sensors installed at the high-frequency pressure measuring points 11 in the front cavity 15 and the rear cavity 10 of the turbine housing 12 can measure the high-frequency pressure pulsation signals of the gas in the front and rear cavities in real time and transmit them to the same external terminal through cables for signal processing.

[0039] d. Monitoring and measurement of turbine disk pitch vibration amplitude and frequency

[0040] The high-frequency pressure pulsation parameters measured by the high-frequency pressure sensor are processed through short-time Fourier transform to obtain the turbine disk cavity fluid pressure pulsation frequency f and amplitude A. Two sets of measurement parameters are obtained from the two high-frequency pressure sensors in the front and rear cavities of the turbine disk. Each set of measurement parameters includes the natural frequency f0 of the turbine disk pitch vibration, the forward wave frequency f1, and the backward wave frequency f2.

[0041] Among them, when the pitch diameter vibration of the turbine disk occurs, the natural frequency f0 and vibration amplitude A' of the turbine disk pitch diameter vibration are represented by the turbine disk cavity fluid pressure pulsation frequency f and amplitude A obtained after signal processing; at the same time, the forward wave frequency f1 and the backward wave frequency f2 can be obtained according to the natural frequency f0 combined with structural parameters such as the turbine disk pitch number and speed; and the state of the turbine disk pitch diameter vibration is reflected in real time by real-time monitoring of the parameters of the forward wave and the backward wave.

[0042] The specific pitch vibration level of the turbine disc needs to be quantitatively judged by comprehensively considering the natural frequency f0 and vibration amplitude A' obtained by the front and rear cavities. Usually, the front cavity vibration amplitude A'1 and the rear cavity vibration amplitude A'2 obtained by the front and rear cavities are different. Only when both exceed a certain threshold value of 0.01MPa, the turbine disc pitch vibration level can be quantitatively judged based on the two sets of vibration amplitudes.

[0043] e. Real-time monitoring and diagnostic evaluation of turbo pumps

[0044] The turbine disk pitch vibration frequency, vibration amplitude and other parameters obtained in step d are used to quantitatively reflect the turbine disk pitch vibration level. The operator can monitor the working status in real time based on the vibration level and evaluate the health status of the turbine disk structure after the test run.

[0045] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk, characterized in that: The specific steps are as follows: A high-frequency velocity and pressure sensor is installed in the engine turbine disc cavity to ensure that it can directly contact the high-temperature gas mainstream area; The turbine disc generates local pitch vibration, which is transmitted to the gas flow vibration in the front and rear cavities of the turbine disc cavity. The high-frequency pulsation pressure value of the gas is measured by a high-speed pressure sensor. The signal feature extraction and processing of the measured high-frequency pulsation pressure value of the gas is performed to obtain the frequency and amplitude of the fluid pressure pulsation in the turbine disc cavity. Combined with the structural parameters of the turbine disc, the vibration amplitude and frequency of the turbine disc pitch diameter are obtained. The pitch vibration magnitude of the turbine disk is obtained based on the pitch vibration amplitude and frequency of the turbine disk. The working status of the turbine disk is monitored in real time based on the vibration magnitude, and the health status of the turbine disk structure after the test run is evaluated.

2. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 1, characterized in that: The number of the high-frequency velocity pressure sensors is at least two, and they are respectively installed in the turbine disc front cavity (15) and the turbine disc rear cavity (10).

3. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 2, characterized in that: The pulsation measurement frequency of the high-frequency velocity pressure sensor is 0-50000 Hz and is adapted to a working environment temperature of 900K.

4. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 3, characterized in that: The high-frequency velocity pressure sensor is fixed on the turbine housing (5) via a mounting structure.

5. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 4, characterized in that: The mounting structure comprises a base (2), a sleeve (3), and a sealing gasket (4); the base (2) is fixed on a turbine housing (5); the high-frequency velocity pressure sensor (1) is inserted into the base (2) and fixed, a sealing gasket (4) is arranged between the bottom and the base (2), and the head extends out to directly contact the gas medium; the sleeve (3) is located between the high-frequency velocity pressure sensor (1) and the base (2), the outer side of the sleeve (3) is connected to the base (2), the inner side of the sleeve (3) presses the high-frequency velocity pressure sensor (1), and an anti-loosening treatment is performed between the sleeve (3) and the base (2).

6. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 5, characterized in that: The sealing gasket (4) is a metal gasket and is loaded by torque.

7. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 5, characterized in that: The anti-loosening treatment is to apply glue between the base (2) and the sleeve (3) and set a fuse (6).

8. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 1, characterized in that: The short-time Fourier transform is used to extract the signal features of the measured high-frequency pulsation pressure value of the gas to obtain the turbine disk cavity fluid pressure pulsation frequency f and amplitude A. Combined with the turbine disk structural parameters, the turbine disk pitch diameter vibration frequency and vibration amplitude A' are obtained.

9. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 8, characterized in that: The pitch vibration frequency of the turbine disk includes the natural frequency f0, the forward wave frequency f1, and the backward wave frequency f2 measured from the front and rear cavities.

10. The method for monitoring pitch diameter vibration of a liquid rocket engine turbine disk according to claim 8, characterized in that: The turbine disk pitch diameter vibration amplitude A' includes the front cavity vibration amplitude A'1 and the rear cavity vibration amplitude A'2. When both exceed the threshold value of 0.01 MPa, the turbine disk pitch diameter vibration magnitude is quantitatively determined.

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