Engine unstable working state dynamic stress measuring device and method

Abstract

The application belongs to the technical field of engine measuring device, and proposes an engine unstable working state dynamic stress measuring device and method, wherein the measuring device comprises an experimental platform, an engine is fixedly installed on the experimental platform, a helicopter air inlet of the engine is communicated with an air source through a pipeline, and an electromagnetic valve and an electric valve are sequentially arranged on the pipeline from the air source to the engine; a compressor is arranged in the engine, a strain gauge is installed on an impeller of the compressor, the strain gauge is electrically connected with a dynamic stress measuring device, the dynamic stress measuring device is installed on the experimental platform and located at the outer side of the engine; the engine is connected with the air source from the helicopter air inlet, high-pressure air is sprayed into a combustion chamber through the helicopter air inlet, the pressure before a gas turbine guide vane is increased, the engine enters an unstable working state, and then the strain force of the impeller under the unstable working state is conveniently measured.

Description

Technical Field

[0001] This application belongs to the technical field of engine measurement devices, and specifically relates to a dynamic stress measurement device and method for an engine in unstable operating conditions. Background Technology

[0002] As the power source for helicopters, turboshaft engines require dynamic stress measurement tests on their compressor blades during development to verify whether the blades meet design strength requirements under load during operation. In actual use, turboshaft engines encounter various states and scenarios, such as surge, a relatively common unstable operating condition. During surge, the airflow oscillates axially at low frequencies in the compressor channel, subjecting the compressor blades to low-frequency and high-amplitude pressure impacts, and even reverse impacts, resulting in significant instantaneous impacts on the suction surface (non-design load-bearing surface) of the blades. Therefore, obtaining the dynamic stress distribution of the compressor blades under unstable conditions is crucial for their strength design.

[0003] The existing technology describes the test method for measuring the dynamic stress of compressor blades under steady-state conditions of a turboshaft engine, but does not describe the test method and test equipment layout for measuring dynamic stress under unstable operating conditions of a turboshaft engine.

[0004] Therefore, there is a need for equipment and methods to measure the dynamic stress of compressor blades under unstable operating conditions of turboshaft engines. Summary of the Invention

[0005] To address the aforementioned problems, this application proposes a dynamic stress measurement device for unstable engine operation, comprising an experimental platform on which an engine is fixedly mounted. The engine's helicopter air intake is connected to an air source via a pipeline, with a solenoid valve and an electric valve sequentially installed on the pipeline from the air source to the engine. An air compressor is installed in the engine, and strain gauges are installed on the compressor impeller. The strain gauges are electrically connected to the dynamic stress measurement device, which is mounted on the experimental platform and located outside the engine.

[0006] Furthermore, a pressure sensor is installed on the pipeline, located between the solenoid valve and the gas source.

[0007] Furthermore, the dynamic stress measurement device includes a data acquisition system, which is electrically connected to the strain gauge.

[0008] Furthermore, the dynamic stress measurement device also includes a lubrication and cooling system, a slip ring actuator is installed on the engine, the strain gauge wires are electrically connected to the data acquisition system through the slip ring actuator, and the lubrication pipeline of the lubrication and cooling system is connected to the lubrication pipeline of the slip ring actuator.

[0009] A method for measuring dynamic stress in an engine operating under unstable conditions, using the aforementioned apparatus, includes the following steps:

[0010] Install the strain gauge on the engine impeller and electrically connect the strain gauge to the dynamic stress measuring device; connect the engine's helicopter air bleed port to the air source through a pipeline;

[0011] Start the engine and bring it to idle position on the ground for a specified period of time. ;

[0012] Push the engine up to idle slow position, dwell time To complete the engine's warm-up operation;

[0013] Obtain the vibration scan rate, and use the vibration scan rate to push the engine to its maximum operating state and remain there for a specified period of time. To obtain data across the entire speed range;

[0014] Based on data from the entire speed range, the resonance speed is obtained, and the engine is controlled to enter the resonance speed state and remain there for a specified period of time. Get the time period The pressure ratio of the engine;

[0015] In time period In the process of gas entering the engine's combustion chamber from the gas source, if the gas pressure in the gas source is greater than the bleed air pressure of the turboshaft engine, the engine enters an unstable operating region, which persists for a period of time. ;

[0016] The dynamic stress measurement device obtains time intervals through strain gauges. Dynamic stress test data of the intermediate impeller; execute engine shutdown procedure;

[0017] Furthermore, it also includes the following steps, for time periods The experimental data were processed to obtain the variation law of dynamic stress at different blade positions with pressure ratio under unstable engine operating conditions.

[0018] Furthermore, the vibration scanning rate ranges from 50 r / min / s to 200 r / min / s.

[0019] Furthermore, the data for the entire speed range includes the impeller's resonant frequency, amplitude, order, and resonant speed.

[0020] Furthermore, in the time period In the process where gas from the air supply enters the engine's combustion chamber, and the gas pressure in the air supply exceeds the engine's bleed air inlet pressure, the engine enters an unstable operating region, which persists for a period of time. Includes the following steps:

[0021] In time period In the middle, the solenoid valve is opened and the electric valve is slowly opened to allow high-pressure gas to enter the combustion chamber, and the pressure of the high-pressure gas is greater than the bleed air port pressure of the turboshaft engine.

[0022] Adjust the opening of the electric valve to bring the engine into an unstable operating range, deviating from the target normal operating state, and maintain this position for a specified period. Record the changes in the compressor pressure ratio.

[0023] Furthermore, the formula for calculating the compressor pressure ratio is as follows:

[0024] π = p2 / p1, where π represents the compressor pressure ratio, p1 represents the compressor inlet pressure, and p2 represents the compressor outlet pressure.

[0025] Beneficial effects of this invention:

[0026] 1. The dynamic stress measuring device for unstable engine operating state of the present invention includes an experimental platform on which an engine is fixedly installed. The engine's helicopter bleed air inlet is connected to a gas source through a pipeline. A strain gauge is installed on the engine impeller and is electrically connected to the dynamic stress measuring device. The dynamic stress measuring device is installed on the experimental platform and located outside the engine. The engine is connected to a gas source through the helicopter bleed air inlet, and high-pressure air is injected into the combustion chamber through the helicopter bleed air inlet to increase the pressure in front of the gas turbine guide vanes, causing the engine to enter an unstable operating state, thereby facilitating the measurement of the impeller strain force under unstable operating state.

[0027] 2. The dynamic stress measurement method for unstable engine operating state of the present invention includes the following steps: obtaining the vibration scanning rate, pushing the engine to the maximum operating state using the vibration scanning rate and holding it there for a period of time. Acquire data across the entire speed range; based on the data across the entire speed range, determine the resonance speed, and control the engine to enter the resonance speed state and remain there for a specified period. Record time period The pressure ratio of the engine; in the time period In the process of gas entering the engine's combustion chamber from the gas source, if the gas pressure in the gas source is greater than the bleed air pressure of the turboshaft engine, the engine enters an unstable operating region, which persists for a period of time. Get time period The experimental data in the data, for a time period The experimental data were processed to obtain the variation law of dynamic stress at different blade positions with pressure ratio under unstable engine operating conditions. This method can obtain the dynamic stress distribution law of compressor blades under unstable operating conditions, providing data support for its strength design, and filling the gap in this type of test method.

[0028] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description and the accompanying drawings. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram of the dynamic stress measurement device for unstable engine operating conditions is shown in an embodiment of this application.

[0031] Figure 2 A schematic diagram of the dynamic stress measuring device in an embodiment of this application is shown.

[0032] Figure 3 A flowchart illustrating the dynamic stress measurement method for unstable engine operating conditions in an embodiment of this application is shown.

[0033] Figure 4 A flowchart illustrating the variation of dynamic stress with pressure ratio at different blade positions in embodiments of this application is shown.

[0034] Explanation of reference numerals in the attached drawings: 10, Exhaust ejector system; 20, Experimental platform; 30, Power absorption and measurement device; 40, Engine; 50, Dynamic stress measurement device; 51, Impeller; 52, Strain gauge; 53, Slip ring actuator; 54, Lubrication and cooling system; 55, Data acquisition system; 60, Protective plate; 71, Air source; 72, Pressure sensor; 73, Solenoid valve; 74, Electric valve. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] Example 1

[0037] refer to Figure 1A dynamic stress measuring device for unstable engine operation includes an experimental platform 20, on which an engine 40 is fixedly mounted. The helicopter air bleed port of the engine 40 is connected to an air source 71 via a pipe. The air source 71 is a high-pressure air source. An air compressor is installed in the engine 40, and strain gauges 52 are mounted on the impeller 51 of the air compressor. The strain gauges 52 are electrically connected to the dynamic stress measuring device 50, which is mounted on the experimental platform 20 and located outside the engine 40. The exhaust port of the engine 40 is connected to the inlet of an exhaust ejector system 10, and the output shaft of the engine 40 is drive-connected to a power absorption and measurement device 30.

[0038] Furthermore, the engine 40 is equipped with a combustion chamber and a compressor, and a helicopter air vent is provided on the outer casing between the combustion chamber and the compressor. The helicopter air vent is connected to the air source 71 through a pipe.

[0039] Specifically, the layout of the test equipment is as follows: Figure 1 As shown, a signal line from the modified component at the intake end of engine 40 is electrically connected to the dynamic stress measuring device 50. Since engine 40 cannot be fitted with its own protective mesh, a protective plate 60 is installed at the intake front end of engine 40 in a position that does not affect intake conditions. The protective plate 60 is fixedly installed on the upper surface of the experimental platform 20. To actively create an unstable operating state for engine 40, disturbances need to be introduced. In this embodiment, engine 40 is connected to an air source 71 from the helicopter bleed air inlet, and high-pressure air is injected into the combustion chamber through the helicopter bleed air inlet, increasing the pressure in front of the gas turbine guide vanes, causing engine 40 to enter an unstable operating state.

[0040] Furthermore, a pressure sensor 72, a solenoid valve 73, and an electric valve 74 are sequentially installed on the pipeline from the air source 71 to the engine 40. The pressure sensor 72 is used to measure the pressure of the gas exiting the air source 71. Specifically, the output pipeline of the air source 71 connects to the engine 40 after passing through the pressure sensor 72, the solenoid valve 73, and the electric valve 74. The air source pressure must be greater than the bleed air pressure of the engine 40 under the target condition and be able to continuously output high-pressure air for a certain period of time. The solenoid valve 73 can open and close the pipeline in a timely manner. When the solenoid valve 73 is open, the electric valve 74 controls the air pressure and flow rate entering the bleed air port by adjusting the opening degree of the electric valve 74, so that the pressure ratio of the engine 40 increases while the compressor speed remains constant, deviating from the common operating line and entering an unstable operating state.

[0041] refer to Figure 2 The dynamic stress measurement device 50 includes a data acquisition system 55, which is electrically connected to the strain gauge 52. The data acquisition system 55 acquires the test data of the strain gauge 52, thereby facilitating subsequent data processing and analysis.

[0042] refer to Figure 2The dynamic stress measuring device 50 also includes a lubrication and cooling system 54. A slip ring actuator 53 is installed on the engine 40. The wires of the strain gauge 52 are electrically connected to the data acquisition system 55 through the slip ring actuator 53. The lubrication pipeline of the lubrication and cooling system 54 is connected to the lubrication pipeline of the slip ring actuator 53.

[0043] Specifically, the lubrication and cooling system 54 provides lubricating oil to the slip ring actuator 53, thereby lubricating the slip ring actuator 53 and cooling it, thus reducing its temperature.

[0044] Example 2

[0045] refer to Figure 3 A method for measuring dynamic stress in an engine operating under unstable conditions, using the apparatus of Example 1, includes the following steps:

[0046] S1, adjust the working environment (temperature, speed, oil mist, etc.).

[0047] S2, install the strain gauge 52 on the impeller 51 of the engine 40, and electrically connect the strain gauge 52 to the dynamic stress measuring device 50; connect the helicopter air vent of the engine 40 to the air source 71 through a pipe.

[0048] Specifically, in S21, the vibration characteristics of the impeller 51 are calculated and experimentally analyzed to determine the possible vibration order of the impeller 51 under its operating state. Based on the mode shape, the stress distribution trend of the impeller 51 blades is determined, and the position and orientation of the strain gauge 52 for dynamic stress measurement, as well as the stress sensitivity (ratio of the stress at the measuring point to the maximum peak stress) at each measuring point, are determined. For the blade vibration characteristic calculation and analysis, an overall impeller 51 analysis model is used, and a sensitivity judgment criterion is introduced to calculate and experimentally analyze the vibration characteristics of the impeller 51, determining the possible vibration order of the impeller 51 under its operating state.

[0049] S22, the patch position, orientation, patch blade, and number of patches are analyzed and determined. The stress distribution trend of the blade is determined based on the mode shape. The position and orientation of the patch for dynamic stress measurement and the stress sensitivity of each measuring point are determined (the greater the stress gradient, the greater the impact of position error on the test results. The patch position should not be in the region of excessively high strain gradient in order to minimize position sensitivity).

[0050] S23, the lead wire of impeller 51 needs to be adapted to the special structure of the component, and the engine 40 or component needs to be structurally modified to extract the test signal. A hole is machined at the test piece location, a slot is cut in the central tie rod to accommodate the lead wire, and a wire hole is drilled in the bearing positioning sleeve to allow the lead wire to pass through. The lead wire is connected to the test lead wire, and then connected to a signal transmission device (such as slip ring actuator 53) mounted coaxially with the rotor, thereby transmitting the strain signal generated by the high-speed rotation of the test piece to the stationary test equipment. The dynamic stress of the test piece (impeller 51) is obtained through the signal acquisition and analysis system. The dynamic stress measuring device 50 is composed as follows: Figure 2 As shown.

[0051] S3, start the engine and move to idle speed (40 km / h), pause for a specified period of time. .

[0052] S4, push the engine up to 40 to idle slow state, dwell time period To complete the warm-up operation of engine 40.

[0053] S5, acquire the vibration scan rate, and push the engine up to its maximum operating state by 40 based on the vibration scan rate and remain there for a specified period of time. The process involves acquiring data across the entire speed range. Specifically, vibration scanning refers to the process of slowly pushing the engine 40 from its idle slow state to its maximum state to obtain the vibration of the engine 40 at all speeds. The vibration scanning rate is typically between 50 r / min / s and 200 r / min / s. This process obtains the stress distribution across the entire speed range and acquires data for each test part across the entire speed range. The data includes the main resonant frequency, amplitude, order, and resonant speed of the patch measurement points on the impeller 51.

[0054] S6, based on data from the entire speed range, obtains the resonance speed and controls the engine to enter the resonance speed state at 40 and remain there for a specified period. Record time period The pressure ratio of the medium-sized engine is 40.

[0055] S7, during the time period During this process, gas from gas source 71 enters the combustion chamber of engine 40, and the gas pressure in gas source 71 is greater than the bleed air pressure of engine 40. Engine 40 then enters an unstable operating region, which persists for a period of time. The steps include:

[0056] S71, during the time period In the middle, the solenoid valve 73 is opened and the electric valve 74 is slowly opened to allow high-pressure gas to enter the combustion chamber, and the pressure of the high-pressure gas is greater than the bleed port pressure of the turboshaft engine 40.

[0057] S72 adjusts the opening of the electric valve 74 to cause the engine 40 to enter an unstable operating range, deviating from the target state of normal operation (stall, surge, etc.), and maintain this state for a certain period of time. Record the changes in compressor pressure ratio during this process.

[0058] Furthermore, the compressor pressure ratio is calculated using the formula π = p2 / p1, where p1 represents the compressor inlet pressure and p2 represents the compressor outlet pressure. During this process, the rotational speed remains unchanged, effectively simulating the entire process of engine 40 entering an unstable state. The entry of high-pressure gas into the flow channel causes a change in the load on the blades, resulting in deformation changes in strain gauge 52. The new strain signal is extracted via slip ring actuator 53 and transmitted to the data acquisition system 55, completing the measurement of the compressor blade dynamic stress during this process.

[0059] S8, the dynamic stress measuring device 50 obtains the time interval through the strain gauge 52. The dynamic stress test data of the impeller 51 were obtained, and the test results were obtained. The variation law of the dynamic stress of the blade under unstable state with the pressure ratio under the resonant speed of the engine 40 was obtained to confirm the validity of the test. If other states are required, the above steps S5-S8 are repeated at other speeds. After the experiment is completed, the engine 40 shutdown procedure is executed.

[0060] S9, for time periods The experimental data were processed to obtain the variation law of dynamic stress at different blade positions with pressure ratio under the unstable operating state of engine 40.

[0061] Obtain as Figure 4 The comparison curves shown indicate that, during operation at the resonant speed Ng, through experimental step S6, the compressor pressure ratio of the engine's 40 aerodynamic parameters was adjusted from... Change to We obtained the variation law of dynamic stress με at different blade positions with pressure ratio π under the condition that Ng remains constant.

[0062] The dynamic stress signal analysis measured by this method is mainly based on the raw strain signals acquired by the data acquisition system 55. It analyzes the blade vibration response, the characteristics of blade vibration stress amplitude and vibration frequency changing with rotational speed, and provides order curves, total stress curves, fixed frequency curves, and spectrum curves. Combined with the blade vibration modal stress distribution, the stress at the blade's maximum stress point is calculated for subsequent strength and life calculations.

[0063] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A dynamic stress measuring device for an engine operating under unstable conditions, characterized in that, The experimental platform (20) includes an engine (40) fixedly mounted on it. The helicopter air intake of the engine (40) is connected to the air source (71) through a pipe. A solenoid valve (73) and an electric valve (74) are sequentially arranged on the pipe from the air source (71) to the engine (40). A compressor is installed in the engine (40). A strain gauge (52) is installed on the impeller (51) of the compressor. The strain gauge (52) is electrically connected to a dynamic stress measuring device (50). The dynamic stress measuring device (50) is installed on the experimental platform (20) and located outside the engine (40). The strain gauge (52) is installed on the impeller (51) of the engine (40), and the strain gauge (52) is electrically connected to the dynamic stress measuring device (50); the helicopter air vent of the engine (40) is connected to the air source (71) through a pipe; Start the engine (40) to idle speed on the ground, and stay for a period of time. ; Push the engine (40) up to idle slow state, and stay for a period of time. To complete the thermal operation of the engine (40); Obtain the vibration scan rate, and use the vibration scan rate to push the engine (40) up to the maximum operating state and remain there for a certain period of time. To obtain data across the entire speed range; The resonance speed is obtained based on data from the entire speed range, and the engine (40) is controlled to enter the resonance speed state and remain there for a specified period of time. Get the time period The pressure ratio of the medium engine (40); In time period In the process, gas from the gas source (71) enters the combustion chamber of the engine (40), and the gas pressure in the gas source (71) is greater than the bleed air pressure of the turboshaft engine. The engine (40) enters an unstable operating region and remains unstable for a period of time. This includes the following steps: within a time period In the middle, open the solenoid valve (73) and slowly open the electric valve (74) to allow high-pressure gas to enter the combustion chamber, and the pressure of the high-pressure gas is greater than the bleed air pressure of the turboshaft engine; adjust the opening of the electric valve (74) to make the engine (40) enter the unstable working area to deviate from the target state of normal operation, and maintain this state for a period of time. Record the changes in the compressor pressure ratio; The dynamic stress measuring device (50) obtains the time period through strain gauges (52). Dynamic stress test data of the impeller (51) were used to execute the engine (40) shutdown procedure.

2. The dynamic stress measuring device for unstable engine operating state according to claim 1, characterized in that, A pressure sensor (72) is also installed on the pipeline, and the pressure sensor (72) is located between the solenoid valve (73) and the gas source (71).

3. The dynamic stress measuring device for unstable engine operating state according to claim 1, characterized in that, The dynamic stress measuring device (50) includes a data acquisition system (55), which is electrically connected to the strain gauge (52).

4. The dynamic stress measuring device for unstable engine operating state according to claim 3, characterized in that, The dynamic stress measuring device (50) also includes a lubrication and cooling system (54), a slip ring actuator (53) is installed on the engine (40), and the wires of the strain gauge (52) are electrically connected to the data acquisition system (55) through the slip ring actuator (53); the lubrication pipeline of the lubrication and cooling system (54) is connected to the lubrication pipeline of the slip ring actuator (53).

5. The dynamic stress measuring device for unstable engine operating state according to claim 1, characterized in that, It also includes the following steps, for time periods The experimental data were processed to obtain the variation law of dynamic stress at different blade positions with pressure ratio under unstable working conditions of engine (40).

6. The dynamic stress measuring device for unstable engine operating state according to claim 1, characterized in that, The vibration scanning rate ranges from 50 r / min / s to 200 r / min / s.

7. The dynamic stress measuring device for unstable engine operating state according to claim 1, characterized in that, The data for the full speed range includes the resonant frequency, amplitude, order, and resonant speed of the impeller (51).

8. The dynamic stress measuring device for unstable engine operating state according to claim 1, characterized in that, The formula for calculating the compressor pressure ratio is as follows: π = p2 / p1, where π represents the compressor pressure ratio, p1 represents the compressor inlet pressure, and p2 represents the compressor outlet pressure.

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