Method for simulating continuous rotation test state under condition of blade loss of turboprop engine

Abstract

The present invention discloses a method for simulating a continuous rotation test state under blade loss conditions for a turboshaft engine. The method determines the free rotation of the main rotor and the survival of rotor blades after blades are lost at different locations on the main rotor through structural design analysis. Based on this, the blade loss location at which the initial damage to the mounting joint is greatest and the blade loss location at which the unbalanced load on the mounting joint is greatest during continuous rotation are determined. This method can simulate an engine state in which the initial damage to the mounting joint is greatest and the unbalanced load on the mounting joint is greatest during continuous rotation. This method rigorously simulates the engine state during a continuous rotation test under blade loss conditions. A single test verifies that continued rotation after blade loss at any location will not cause unintentional disengagement of the engine from the aircraft's mounting joint. Furthermore, the method considers the influence of atmospheric temperature on the main rotor speed, improving the accuracy and reliability of the continuous rotation test.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous rotation testing, and in particular to a method for simulating a continuous rotation test state under a condition where a turboshaft engine blade is lost. Background Art

[0002] Continuous rotation means that after the engine stops in mid-air, at least one of the engine's main rotors continues to rotate. The cause of the continuous rotation may be a windmill effect or a mechanical effect, or a combination of the two. Currently, most rotorcraft are equipped with an overrunning clutch, that is, the clutch will disengage immediately after a single engine stops, so generally only the continuous rotation caused by the windmill effect is considered. According to the requirements of the airworthiness clause, any non-hazardous failure that causes the engine to stop in mid-air must not further develop into a hazardous engine consequence. Among them, hazardous engine consequences applicable to the continuous rotation process include: unintentional disconnection of the engine and the aircraft mounting joint, uncontained high-energy debris, the concentration of toxic substances in the cabin engine bleed air is sufficient to disable the crew or passengers, uncontrollable fire (lubricating oil leakage reaches a certain dangerous amount), etc. For general turboshaft engines, the flight speed is relatively low. Under the action of windmilling, the main rotor continuously rotates at a low speed, generally not exceeding 7% of the rated speed. At this time, the lower centrifugal load will not produce uncontained high-energy debris; the lower compressor outlet pressure causes the cabin engine bleed air to be unable to enter the rotorcraft's air system, and it is impossible for the crew or passengers to lose their abilities; the lubricating oil pump is driven by the main rotor, and the lower operating speed of the lubricating oil pump causes the loss of lubricating oil supply capacity. In addition, the lubricating oil system is equipped with a one-way valve, which only allows oil supply at a certain pressure to pass through, and lubricating oil leakage is impossible.

[0003] However, during engine operation, individual blades may develop weak spots and break due to factors such as manufacturing variations or damage from foreign objects, resulting in blade loss. When a blade is lost, it creates a significant unbalanced load on the engine mounting joint, including unbalanced forces and moments, which in turn causes a certain amount of initial damage and potentially affects the mounting joint's load-bearing capacity. During subsequent continuous rotation, the engine rotor will experience an imbalance exceeding normal levels due to incomplete blades, continuing to exert unbalanced loads on the mounting joint. Although the load may be small, it can still cause cumulative fatigue damage to the mounting joint over the continuous rotation period (generally over two hours), easily leading to further damage and potentially unintentional disconnection of the engine from the aircraft mounting joint. Existing methods for simulating the continuous rotation test state of a turboshaft engine include two: one is the high-altitude platform test method, which simulates the inlet Mach number by adjusting the engine inlet and outlet pressures to create a pressure differential between the engine inlet and outlet; the other is the motor-driven engine test method, which determines the relationship between the engine inlet and outlet conditions and the continuous rotation speed, and then uses the motor to drive the engine to the target continuous rotation speed. Therefore, existing simulation methods all assume that the engine is in normal condition and conduct continuous rotation tests. However, the engine condition after blade loss is obviously different from the normal engine condition, so existing simulation methods cannot simulate the state of continuous rotation of the engine under blade loss conditions. Summary of the Invention

[0004] The present invention provides a method for simulating the continuous rotation test state of a turboshaft engine under blade loss conditions. The method can simulate the engine state in the continuous rotation test under blade loss conditions, and can verify through a single test that continuous rotation after blade loss at any position will not cause unintentional disengagement of the engine and the aircraft mounting node. The method also takes into account the influence of atmospheric temperature on the main rotor speed, thereby improving the accuracy and reliability of the continuous rotation test.

[0005] According to one aspect of the present invention, a method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions is provided, comprising the following steps:

[0006] Conduct continuous rotation tests on turboshaft engines to determine the atmospheric temperature conditions for maximum continuous rotation speed;

[0007] Conduct structural design analysis to determine whether the engine's main rotor can rotate freely and the survival of rotor blades after blades in different parts of the main rotor are lost;

[0008] Identify the blade loss location that caused the greatest initial damage to the installation node;

[0009] Identify the blade loss location that causes the greatest unbalanced load on the mounting section during continuous rotation;

[0010] Conduct blade loss tests based on the blade loss location that causes the greatest initial damage to the installation node;

[0011] After the blade loss test, the engine is disassembled and the main rotor blades are supplemented and removed based on the blade loss location that causes the largest unbalanced load on the installation section during continuous rotation, and the engine is reassembled;

[0012] A continuous rotation test is carried out on the reassembled engine based on the determined atmospheric temperature conditions.

[0013] Furthermore, the process of conducting a continuous rotation test on the turboshaft engine to determine the atmospheric temperature condition at which the rotation speed is the highest during the continuous rotation includes the following:

[0014] Under the declared minimum altitude and maximum Mach number conditions, start the engine at different atmospheric temperatures within the declared range in turn, and run it for a preset time in ground slow, air slow, maximum continuous and takeoff states. When the engine oil temperature stabilizes in the takeoff state, stop the engine, record the speed of each rotor of the engine after a period of time, and screen out the atmospheric temperature condition with the highest rotor speed.

[0015] Furthermore, the process of conducting structural design analysis to determine whether the main rotor of the engine can rotate freely after blades at different parts of the main rotor are lost and the survival status of the rotor blades includes the following:

[0016] The path of each blade after loss is analyzed based on the flow path structure to determine whether it will cause further damage and whether the damage will cause the rotor to become stuck. The extent of damage caused to adjacent blades and downstream blades at the same level after the blade is lost is analyzed based on the structure and strength of the blade to ensure that the main rotor can rotate freely.

[0017] Furthermore, when the multi-stage blades or centrifugal stage blades of the compressor are lost, the gas generator rotor cannot rotate, and the power turbine rotor rotates freely with the blades intact; when the first-stage blades or second-stage blades of the gas turbine are lost, the gas generator rotor rotates freely and only a single blade is lost, and the power turbine rotor cannot rotate; when the first-stage blades of the power turbine are lost, the gas generator rotor rotates freely and the blades remain intact, and the power turbine rotor cannot rotate; when the second-stage blades of the power turbine are lost, the gas generator rotor rotates freely and the blades remain intact, and the power turbine rotor rotates freely and the first-stage blades remain intact.

[0018] Furthermore, the process of determining the blade loss location that causes the greatest initial damage to the installation node includes the following:

[0019] Based on whether the main rotor of the engine can rotate freely after the loss of blades in different parts and the survival of the rotor blades, the unbalanced loads on the mounting node under different blade loss conditions are calculated respectively. Among them, the unbalanced load borne by the main mounting node includes unbalanced force and unbalanced moment, and the unbalanced load borne by the auxiliary mounting node is the unbalanced force. The case where the unbalanced load borne by the mounting node is the largest is regarded as the case where the initial damage of the mounting node is the largest, and the corresponding blade loss part is determined to be the second-stage blade of the power turbine rotor.

[0020] Furthermore, the process of determining the blade loss position causing the maximum unbalanced load on the mounting section during continuous rotation includes the following steps:

[0021] Based on whether the engine's main rotor can rotate freely after blades are lost at different locations and the remaining status of the rotor blades, a qualitative analysis of the imbalance during continuous rotation is conducted to determine the imbalance that should be considered for the freely rotating main rotor, thereby determining the blade loss location in the main rotor that causes the maximum unbalance load at the installation section during continuous rotation.

[0022] Furthermore, when multiple-stage blades or centrifugal-stage blades of the compressor are lost, the imbalance of the power turbine rotor is equivalent to a normal level; when the first-stage blades of the gas turbine are lost, the imbalance of the gas generator rotor should consider the imbalance corresponding to a single first-stage blade; when the second-stage blades of the gas turbine are lost, the imbalance of the gas generator rotor should consider the imbalance corresponding to a single second-stage blade; when the first-stage blades of the power turbine are lost, the imbalance of the gas generator rotor is equivalent to a normal level; when the second-stage blades of the power turbine are lost, the imbalance of both the gas generator rotor and the power turbine rotor are equivalent to normal levels.

[0023] Furthermore, the leaf loss test includes the following:

[0024] After pre-fabricating cracks at the root or outermost mortise of the second-stage blades of the power turbine rotor, complete the engine assembly. When conducting the engine test, increase the main rotor speed to the maximum allowable speed. After staying for a preset time, if the second-stage blades of the power turbine rotor do not break, increase the engine speed until the blades break; alternatively, conduct a power turbine blade shedding test.

[0025] Furthermore, the process of conducting a continuous rotation test on the reassembled engine based on the determined atmospheric temperature conditions includes the following:

[0026] Install strain gauges on the mounting joint to obtain the stress level of the mounting joint during continuous rotation. At the declared minimum altitude and determined atmospheric temperature conditions, increase the Mach number so that the engine main rotor continues to rotate under the action of the airflow until the maximum speed requirement is met. When the continuous rotation time reaches 1 / 2 of the engine's maximum flight time, the Mach number is reduced to 0 and the engine main rotor will stop continuous rotation. After the test, check whether the mounting joint is detached.

[0027] Furthermore, if the main rotor gets stuck during the continuous rotation test, causing the test to be interrupted, it is necessary to conduct component testing on the installation joint based on the measurement data of the strain gauge to ensure that the installation joint bears the load for 1 / 2 of the maximum flight time of the engine.

[0028] The present invention has the following beneficial effects:

[0029] The method of the present invention simulates the continuous rotation test state of a turboshaft engine under blade loss conditions. First, a continuous rotation test is carried out on the turboshaft engine to determine the atmospheric temperature conditions with the highest continuous rotation speed. Then, by carrying out structural design analysis, it is determined whether the main rotor of the engine can rotate freely and the survival status of the rotor blades after the blades at different parts of the main rotor are lost. The blade loss part with the greatest initial damage to the installation node and the blade loss part that causes the greatest unbalanced load on the installation node during continuous rotation are further determined. Then, a blade loss test is carried out based on the blade loss part that causes the greatest initial damage to the installation node, thereby obtaining an engine with the greatest initial damage to the installation node. Then, according to the blade loss part that causes the greatest unbalanced load on the installation node during continuous rotation, the main rotor of the engine with the greatest initial damage to the installation node is supplemented and removed to complete the engine reassembly. Finally, a continuous rotation test is carried out on the reassembled engine. Through structural design analysis, the present invention determines the free rotation of the main rotor and the survival of rotor blades after blades are lost from different locations on the main rotor. Based on this, the present invention further determines the location of blade loss when the initial damage to the mounting joint is greatest and the location of blade loss when the unbalanced load on the mounting joint during continued rotation is greatest. These locations provide standards for subsequent blade loss testing and engine reinstallation. This method simulates an engine state where the initial damage to the mounting joint is greatest and the unbalanced load on the mounting joint during continued rotation is greatest. Conducting a continued rotation test under this engine state rigorously simulates the engine state during a continued rotation test under blade loss conditions. A single test verifies that continued rotation after blade loss at any location will not cause unintentional disengagement of the engine from the aircraft's mounting joint, effectively meeting airworthiness test requirements. Furthermore, by first determining the atmospheric temperature conditions for the highest continued rotation speed and then conducting the continued rotation test based on these determined atmospheric temperature conditions, the influence of atmospheric temperature on the main rotor speed is considered, improving the accuracy and reliability of the continued rotation test.

[0030] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 It is a flow chart of a method for simulating a continuous rotation test state under a condition of blade loss of a turboshaft engine according to a preferred embodiment of the present application.

[0033] Figure 2 It is a schematic diagram of the compressor blades of each stage of the dual-rotor turboshaft engine in the preferred embodiment of the present application.

[0034] Figure 3 It is a schematic diagram of the turbine blades of each stage of the dual-rotor structure turboshaft engine in the preferred embodiment of the present application.

[0035] Figure 4 It is a schematic diagram of the coordinate axis direction of the twin-rotor structure turboshaft engine in the preferred embodiment of the present application.

[0036] Figure 5 It is a schematic diagram of the coordinate axes of the twin-rotor turboshaft engine in the preferred embodiment of the present application.

[0037] Figure 6 It is a schematic diagram of the power turbine rotor blades of the twin-rotor structure turboshaft engine in the preferred embodiment of the present application.

[0038] Figure 7 It is a structural schematic diagram of a power turbine blade shedding test device in a preferred embodiment of the present application.

[0039] Figure 8 It is a test curve chart of the power turbine blade shedding test carried out in the preferred embodiment of the present application.

[0040] Figure 9 It is a test curve chart of a continuous rotation test carried out in a preferred embodiment of the present application. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] Reference Figure 1A preferred embodiment of the present application provides a method for simulating a continuous rotation test state under a blade loss condition of a turboshaft engine, wherein the turboshaft engine has a dual-rotor structure, namely, including a gas generator rotor and a power turbine rotor. The method includes the following:

[0043] Step S1: conducting a continuous rotation test on the turboshaft engine to determine the atmospheric temperature condition at which the continuous rotation speed is the highest;

[0044] Step S2: Conducting a structural design analysis to determine whether the main rotor of the engine can rotate freely after blades at different locations of the main rotor are lost, and the remaining status of the rotor blades;

[0045] Step S3: determining the blade loss location that causes the greatest initial damage to the installation node;

[0046] Step S4: determining the blade loss position that causes the largest unbalanced load on the mounting section during continuous rotation;

[0047] Step S5: performing a blade loss test based on the blade loss location that causes the greatest initial damage to the installation node;

[0048] Step S6: disassembling the engine after the blade loss test, and completing or removing blades from the main rotor according to the blade loss location that causes the largest unbalanced load on the installation section during continuous rotation, and then reassembling the engine;

[0049] Step S7: Performing a continuous rotation test on the reassembled engine based on the determined atmospheric temperature conditions.

[0050] It can be understood that the method of simulating the continuous rotation test state of a turboshaft engine under blade loss conditions in this embodiment first conducts a continuous rotation test on the turboshaft engine to determine the atmospheric temperature conditions for the highest continuous rotation speed, and then determines whether the main rotor of the engine can rotate freely and the survival status of the rotor blades after the blades at different parts of the main rotor are lost through structural design analysis, and further determines the blade loss part with the greatest initial damage to the installation node and the blade loss part that causes the largest unbalanced load on the installation node during continuous rotation, and then conducts a blade loss test based on the blade loss part that causes the greatest initial damage to the installation node, thereby obtaining the engine with the greatest initial damage to the installation node, and then, based on the blade loss part that causes the largest unbalanced load on the installation node during continuous rotation, the main rotor of the engine with the greatest initial damage to the installation node is supplemented and removed to complete the engine reassembly, and finally, a continuous rotation test is conducted on the reassembled engine. Through structural design analysis, the present invention determines the free rotation of the main rotor and the survival of rotor blades after blades are lost from different locations on the main rotor. Based on this, the present invention further determines the location of blade loss when the initial damage to the mounting joint is greatest and the location of blade loss when the unbalanced load on the mounting joint during continued rotation is greatest. These locations provide standards for subsequent blade loss testing and engine reinstallation. This method simulates an engine state where the initial damage to the mounting joint is greatest and the unbalanced load on the mounting joint during continued rotation is greatest. Conducting a continued rotation test under this engine state rigorously simulates the engine state during a continued rotation test under blade loss conditions. A single test verifies that continued rotation after blade loss at any location will not cause unintentional disengagement of the engine from the aircraft's mounting joint, effectively meeting airworthiness test requirements. Furthermore, by first determining the atmospheric temperature conditions for the highest continued rotation speed and then conducting the continued rotation test based on these determined atmospheric temperature conditions, the influence of atmospheric temperature on the main rotor speed is considered, improving the accuracy and reliability of the continued rotation test.

[0051] It can be understood that in step S1, the process of conducting a continuous rotation test on the turboshaft engine to determine the atmospheric temperature condition at which the rotation speed is the highest during the continuous rotation includes the following:

[0052] Under the declared minimum altitude and maximum Mach number conditions, start the engine at different atmospheric temperatures within the declared range in turn, and run it for a preset time in ground slow, air slow, maximum continuous and takeoff states. When the engine oil temperature stabilizes in the takeoff state, stop the engine, record the speed of each rotor of the engine after a period of time, and screen out the atmospheric temperature condition with the highest rotor speed.

[0053] Specifically, a turboshaft engine is mounted on a high-altitude platform for a continuous rotation test. During the continuous rotation, the mounting section is subjected to unbalanced loads, including unbalanced forces and unbalanced moments. The calculation formulas for the unbalanced forces and unbalanced moments are as follows: Where F represents the unbalanced force, m represents the unbalanced mass, R represents the distance of the unbalanced mass from the center of rotation, N represents the rotational speed, M represents the unbalanced torque, and L represents the lever arm. In continuous rotation tests, the higher the main rotor speed, the greater the unbalanced load. The main rotor speed is primarily affected by the ramjet effect, and the lower the altitude and the higher the Mach number, the stronger the ramjet effect. Furthermore, the present invention also considers that the main rotor speed is also affected by atmospheric temperature and engine oil temperature. Lower atmospheric temperatures increase air density and increase the air flow through the engine, resulting in higher main rotor speeds. However, on cold days, the engine oil temperature is lower, and the main rotor speed will also be low after shutdown. Therefore, it is necessary to conduct tests to determine the atmospheric temperature conditions for the highest continuous rotation speed. The specific test process is: under the declared minimum altitude and maximum Mach number conditions, select different atmospheric temperatures within the declared range to start the engine in turn, and run it for 3 to 10 minutes in the ground slow, air slow, maximum continuous and take-off states. When the engine oil temperature stabilizes in the take-off state, for example, it does not rise by more than 1°C within 1 minute, stop the engine, record the speed of each rotor of the engine after 5 minutes, and filter out the atmospheric temperature conditions with the highest rotor speed. In addition, for multi-main rotor engines, the maximum speed of each main rotor needs to be recorded separately. For example, in a certain embodiment of the present invention, for a dual-rotor turboshaft engine, at the minimum altitude of -610m, Under the condition of maximum Mach number 0.3, choose different Start the engine at atmospheric temperature, slow down on the ground, slow down in the air, and at maximum Run the engine continuously and in takeoff mode for 3 to 10 minutes. Once the engine oil temperature stabilizes in the takeoff mode (i.e., it rises no more than 1°C in 1 minute), stop the engine and record the engine rotor speed after 5 minutes. The test determined that the ambient temperature at which the continuous rotation speed reaches its maximum is 19°C, the maximum speed of the gas generator rotor (main rotor 1) is 6.9% of the rated speed, and the maximum speed of the power turbine (main rotor 2) is 2.8% of the rated speed.

[0054] It can be understood that in step S2, the process of conducting structural design analysis to determine whether the main rotor of the engine can rotate freely and the remaining status of the rotor blades after the blades at different parts of the main rotor are lost includes the following:

[0055] The path of each blade after loss is analyzed based on the flow path structure to determine whether it will cause further damage and whether the damage will cause the rotor to become stuck. The extent of damage caused to adjacent blades and downstream blades at the same level after the blade is lost is analyzed based on the structure and strength of the blade to ensure that the main rotor can rotate freely.

[0056] Specifically, structural design analysis is carried out in combination with previous engineering experience, and the impact of the loss of blades in different parts of the main rotor is analyzed separately to determine whether the main rotors of the engine can rotate freely after the blades in different parts of the main rotor are lost, and the survival status of the rotor blades. For a dual-rotor turboshaft engine, it includes a gas generator rotor (i.e., main rotor 1) and a power turbine rotor (i.e., main rotor 2), and the gas generator rotor includes two blade parts: the compressor and the gas turbine. First, based on the flow channel structure, analyze the possible path after the blades in a certain part are lost, and analyze whether it will cause further damage and whether the damage will cause the rotor to get stuck. For example Figure 2 As shown, the compressor of the turboshaft engine has the first-stage blades, the second-stage blades, the third-stage blades and the centrifugal-stage blades. Since the centrifugal-stage blades have an axial-to-radial flow channel structure, the debris generated after the upstream blades are lost will cause further damage to the downstream blades under the action of the airflow, and will accumulate at the centrifugal-stage blades, causing the centrifugal-stage rotor to get stuck relative to the stator. Since the centrifugal-stage rotor is stuck, there is no longer centrifugal force and airflow, and the debris cannot enter the downstream part (i.e., the gas turbine and power turbine) radially upward, and thus cannot cause damage to other rotors and blades. At the same time, based on the structure and strength of the blades, the degree of damage caused to the adjacent blades and downstream blades of the same stage after the blades are lost is analyzed, and then it is determined whether each main rotor can rotate freely. As shown in the figure, Figure 3As shown, the gas turbine of a twin-rotor turboshaft engine has first-stage and second-stage blades, and the power turbine has first-stage and second-stage blades. If a first-stage gas turbine blade is lost, it could rapidly fly away from its original position due to centrifugal force and airflow, potentially damaging the upper half of the second-stage gas turbine blades. However, because the first-stage gas turbine blades are hollow, while the second-stage gas turbine blades are solid, damage to the second-stage gas turbine blades is minimal. Losing either the first-stage or second-stage gas turbine blades could damage the upper half of the power turbine blades. Furthermore, because the power turbine blades utilize a shrouded design, damage to a single blade could cause the entire ring of power turbine blades to become unstable and break, preventing the turbine rotor from achieving a windmill-like speed. Losing the first-stage blades of the power turbine also causes the entire ring of power turbine blades to break. However, the second-stage blades of the power turbine, located at the farthest downstream, will break the entire ring of second-stage blades if lost, but the first-stage blades of the power turbine may remain intact and thus still rotate freely. Therefore, the above analysis shows that when multiple or centrifugal blades of the compressor are lost, the gas generator rotor cannot rotate, while the power turbine rotor rotates freely and the blades remain intact. When the first-stage blades or second-stage blades of the gas turbine are lost, the gas generator rotor rotates freely and only a single blade is missing, and the power turbine rotor cannot rotate. When the first-stage blades of the power turbine are lost, the gas generator rotor rotates freely and the blades remain intact, while the power turbine rotor cannot rotate. When the second-stage blades of the power turbine are lost, the gas generator rotor rotates freely and the blades remain intact, while the power turbine rotor rotates freely and the first-stage blades remain intact. Table 1 shows the main rotor rotation and blade retention after blade loss in different rotor locations.

[0057] Table 1 Main rotor rotation and blade retention after blade loss at different rotor locations

[0058]

[0059] It can be understood that in step S3, the process of determining the blade loss location that causes the greatest initial damage to the installation node includes the following:

[0060] Based on whether the main rotor of the engine can rotate freely after the loss of blades in different parts and the survival of the rotor blades, the unbalanced loads on the mounting node under different blade loss conditions are calculated respectively. Among them, the unbalanced load borne by the main mounting node includes unbalanced force and unbalanced moment, and the unbalanced load borne by the auxiliary mounting node is the unbalanced force. The case where the unbalanced load borne by the mounting node is the largest is regarded as the case where the initial damage of the mounting node is the largest, and the corresponding blade loss part is determined to be the second-stage blade of the power turbine rotor.

[0061] Specifically, based on the blade loss conditions in Table 1 above, by comparing the unbalanced loads on the installation node caused by blade loss at different locations, the unbalanced loads on the installation node caused by different blade loss conditions are specifically calculated. When the unbalanced load is the largest, the blade loss location that causes the largest initial damage to the installation node can be determined. Among them, the unbalanced loads caused by blade loss include unbalanced forces and unbalanced moments. The unbalanced force should be equivalent to the unbalanced force caused by the blade breaking at the blade root or the outermost mortise and tenon. The coordinate axis direction of a certain twin-rotor structure turboshaft engine is as follows: Figure 4 As shown, the X-axis is consistent with the flight direction, and the R direction indicates the direction of blade loss, that is, the radial direction of the engine rotor. The engine and rotorcraft installation interface is arranged with a main installation section and two auxiliary installation sections. The main installation section is connected to the rotorcraft through flange edges and bolts and is a fixed support structure. Figure 5 As shown, the main mounting section will bear the unbalanced force and torque caused by the loss of blades; the auxiliary mounting section is connected to the rotorcraft using a connecting rod support structure and only bears the unbalanced force caused by the loss of blades. By calculating the unbalanced load, we can obtain: when blades at different locations are lost, the unbalanced force F borne by the main mounting section is 主，R , unbalanced moment M 主，X , the unbalanced force F borne by the two auxiliary installation sections 辅，1R 、F 辅，2R The calculation formulas for the unbalanced force and unbalanced torque are shown in step S1. The specific calculation process belongs to the prior art and will not be described here. For example, for a twin-rotor turboshaft engine, based on the blade loss conditions in Table 1, the load calculation results of the mounting node are shown in Table 2.

[0062] Table 2. Calculation results of installation section load when blade is lost

[0063]

[0064] According to the calculation results in Table 2, when the second-stage blade of the power turbine is lost, the unbalanced load borne by the installation node is the largest, that is, the initial damage of the installation node is the largest when the second-stage blade of the power turbine is lost.

[0065] It can be understood that in step S4, the process of determining the blade loss position causing the maximum unbalanced load of the mounting section during continuous rotation includes the following:

[0066] Based on whether the engine's main rotor can rotate freely after blades are lost at different locations and the remaining status of the rotor blades, a qualitative analysis of the imbalance during continuous rotation is conducted to determine the imbalance that should be considered for the freely rotating main rotor, thereby determining the blade loss location in the main rotor that causes the maximum unbalance load at the installation section during continuous rotation.

[0067] Specifically, according to the blade loss situation in Table 1, the imbalance amount during the continuous rotation process is calculated. Qualitative analysis can determine the unbalance that should be considered for the freely rotating main rotor, thereby identifying the blade loss location within each rotor that causes the greatest unbalance load on the mounting section during continuous rotation. If the main rotor's unbalance exceeds normal levels, the load on the mounting section during continuous rotation should be calculated using the unbalance force and unbalance torque calculation formulas in step S1, thereby determining the situation where the unbalance load is greatest during continuous rotation. Qualitative analysis reveals that when multiple compressor blades or centrifugal blades are lost, the unbalance of the power turbine rotor is comparable to normal levels. When a first-stage blade of a gas turbine is lost, the gas generator rotor should consider the unbalance corresponding to a single first-stage blade. When a second-stage blade of a gas turbine is lost, the gas generator rotor should consider the unbalance corresponding to a single second-stage blade. When a first-stage blade of a power turbine is lost, the unbalance of the gas generator rotor is comparable to normal levels. When a second-stage blade of a power turbine is lost, the unbalance of both the gas generator and power turbine rotors is comparable to normal levels, as shown in Table 3.

[0068] Table 3. Qualitative analysis of rotor imbalance during continuous rotation

[0069]

[0070] As can be seen from Table 3, for main rotor 1, the imbalance corresponding to a single gas turbine first-stage blade and the imbalance corresponding to a single gas turbine second-stage blade must be considered separately. For main rotor 2, during continuous rotation, if a full circle of first-stage or second-stage blades remains intact, the imbalance is comparable to normal levels. In one embodiment of the present invention, the calculation results of the mounting joint load during continuous rotation are shown in Table 4.

[0071] Table 4. Calculation results of the installation joint load during continuous rotation

[0072]

[0073] It can be seen from Table 4 that the load on the mounting section is the largest during the continuous rotation process after the second-stage blade of the gas turbine is lost.

[0074] It can be understood that in step S5, a blade loss test is carried out according to the blade loss location that causes the greatest initial damage to the installation section determined in step S3, namely, the second-stage blade of the power turbine. For turboshaft engines, there are two ways to conduct blade loss tests. The first is to complete the engine assembly after pre-fabricating cracks at the root or outermost mortise of the second-stage blade of the power turbine rotor. When conducting the engine test, the main rotor speed is increased to the maximum allowable speed. After staying for 5 minutes, if the second-stage blade of the power turbine rotor has not broken, the engine speed is continued to be increased until the blade breaks. The other is to carry out a power turbine blade shedding test, increase the main rotor speed to the blade shedding speed, and cause the blade to break. For turboshaft engines, when the power turbine suddenly loses its load, the power turbine speed will increase rapidly. In order to avoid the wheel from breaking, a weak link will be designed at the root of the blade or the outermost mortise to make the blade fall off first at a high speed, thereby reducing the centrifugal load on the wheel. See the blade shedding design for details. Figure 6 As shown. In order to verify the tolerance of the turbine casing to the falling blades, the power turbine blade shedding test is one of the airworthiness test subjects. Since the speed of the power turbine blade shedding is relatively high, exceeding 130% of the design speed, the unbalanced load on the installation node will be higher than the general blade loss situation. Therefore, conducting a power turbine blade shedding test can more severely simulate the damage caused by the blade loss to the installation node, and there is no need to conduct an additional power turbine blade loss test, saving test costs. Among them, the power turbine blade shedding test device is as follows Figure 7 As shown in the figure, a cutting device is set between the power absorption device and the power turbine output shaft. The cutting device is activated to break the power turbine output shaft. After the power turbine output shaft breaks, the speed of the gas generator rotor (main rotor 1) remains unchanged. The gas pressurized and heated by the gas generator rotor still drives the power turbine, while the power turbine (main rotor 2) loses its load. The speed of the main rotor 2 will increase sharply until the blades fall off. When the blades fall off, the coaxiality between the rotors changes, resulting in friction and wear. The speed of the main rotor 1 also decreases. The test curve is shown in FIG. Figure 8 As shown in Figure 2, the engine with the largest initial damage to the installation section can be obtained through the power turbine blade shedding test.

[0075] It is understood that in step S6, after completing the blade loss test and determining the initial damage to the mounting section, the engine after the blade loss test is disassembled. The main rotor is then reassembled by replacing and removing blades based on the blade loss location that causes the greatest unbalanced load on the mounting section during continuous rotation. This ensures that the unbalance of the reassembled main rotor matches the maximum unbalanced load on the mounting section during continuous rotation determined in step S4. Furthermore, if the main rotor cannot rotate freely after blade loss, the bearings or bearing seats should be replaced to ensure the rotor can rotate. For example, after a turbine blade loss test on a certain type of twin-rotor turboshaft engine, the gas generator rotor became stuck, while the gas generator rotor blades remained intact. The power turbine blades were all broken, rendering the turbine rotor unable to rotate. Based on the conclusions from step S4, the turbine second-stage blade loss caused the greatest unbalanced load on the mounting section during continuous rotation. Therefore, during disassembly and reassembly, one of the turbine second-stage blades was removed, and the power turbine blades were reinstalled, allowing the turbine to rotate freely.

[0076] It can be understood that in step S7, the process of performing the continuous rotation test on the reassembled engine based on the determined atmospheric temperature condition includes the following:

[0077] Install strain gauges on the mounting joint to obtain the stress level of the mounting joint during continuous rotation. At the declared minimum altitude and determined atmospheric temperature conditions, increase the Mach number so that the engine main rotor continues to rotate under the action of the airflow until the maximum speed requirement is met. When the continuous rotation time reaches 1 / 2 of the engine's maximum flight time, the Mach number is reduced to 0 and the engine main rotor will stop continuous rotation. After the test, check whether the mounting joint is detached.

[0078] Among them, the continuous rotation test is generally carried out in a high-altitude simulation cabin, which can simulate the altitude, Mach number and atmospheric temperature. The installation of the engine on the vehicle should be consistent with the installation form of the engine on the rotorcraft. Before the test, a strain gauge is installed on the installation node to obtain the stress level of the installation node during continuous rotation. Due to the blade loss state, the structural integrity of the engine has been destroyed and it cannot be started and operated. The lubricating oil temperature in the bearing cavity cannot be heated. The engine main rotor speed will be lower than the real continuous rotation process. Therefore, during the test, in order to ensure that the verification is in place, the Mach number should be increased to make the main rotor speed consistent with the highest main rotor speed recorded in step S1. The curve of Mach number and engine rotor speed changing with time is as follows Figure 9As shown. Furthermore, if the required Mach number cannot be achieved due to equipment limitations, the test should be stopped, the lubricating oil heated and injected into the engine oil tank, and the main rotor and oil pump driven by the motor to supply the heated lubricating oil to the bearing cavity, and the test should be repeated. After the test, the engine mounting joint should be inspected. If the mounting joint between the engine and the platform has not disengaged, the test has passed, and safe operation during the continuous rotation process can be guaranteed. If the main rotor becomes stuck during the continuous rotation test, causing the test to be interrupted, a component test of the mounting joint should be conducted based on the strain gauge measurement data to ensure that the mounting joint bears the load for 1 / 2 of the engine's maximum flight time.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It is obvious to those skilled in the art that the present invention may be modified and varied in various ways. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions, characterized in that: Includes the following: Conduct continuous rotation tests on turboshaft engines to determine the atmospheric temperature conditions for maximum continuous rotation speed; Conduct structural design analysis to determine whether the engine's main rotor can rotate freely and the survival of rotor blades after blades in different parts of the main rotor are lost; Identify the blade loss location that caused the greatest initial damage to the installation node; Identify the blade loss location that causes the greatest unbalanced load on the mounting section during continuous rotation; Conduct blade loss tests based on the blade loss location that causes the greatest initial damage to the installation node; After the blade loss test, the engine is disassembled and the main rotor blades are supplemented and removed based on the blade loss location that causes the largest unbalanced load on the installation section during continuous rotation, and the engine is reassembled; A continuous rotation test is carried out on the reassembled engine based on the determined atmospheric temperature conditions.

2. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 1, characterized in that: The process of conducting a continuous rotation test on a turboshaft engine to determine the atmospheric temperature condition with the highest rotation speed during the continuous rotation includes the following: Under the declared minimum altitude and maximum Mach number conditions, start the engine at different atmospheric temperatures within the declared range in turn, and run it for a preset time in ground slow, air slow, maximum continuous and takeoff states. When the engine oil temperature stabilizes in the takeoff state, stop the engine, record the speed of each rotor of the engine after a period of time, and screen out the atmospheric temperature condition with the highest rotor speed.

3. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 1, characterized in that: The process of conducting a structural design analysis to determine whether the engine's main rotor can rotate freely after blades at different locations on the main rotor are lost and the survival of the rotor blades includes the following: Analyze the path of blade loss at each location based on the flow path structure to determine whether it will cause further damage and whether the damage will cause the rotor to seize; Based on the structure and strength of the blades, the extent of damage caused to adjacent blades and downstream blades at the same level after the blade is lost is analyzed to ensure that the main rotor can rotate freely.

4. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 3, characterized in that: When the multi-stage blades or centrifugal stage blades of the compressor are lost, the gas generator rotor cannot rotate, the power turbine rotor rotates freely and the blades remain intact; when the first-stage blades or second-stage blades of the gas turbine are lost, the gas generator rotor rotates freely and only a single blade is lost, and the power turbine rotor cannot rotate; when the first-stage blades of the power turbine are lost, the gas generator rotor rotates freely and the blades remain intact, and the power turbine rotor cannot rotate; when the second-stage blades of the power turbine are lost, the gas generator rotor rotates freely and the blades remain intact, and the power turbine rotor rotates freely and the first-stage blades remain intact.

5. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 4, characterized in that: The process of determining the blade loss location that causes the greatest initial damage to the installation node includes the following: Based on whether the main rotor of the engine can rotate freely after the loss of blades in different parts and the survival of the rotor blades, the unbalanced loads on the mounting node under different blade loss conditions are calculated respectively. Among them, the unbalanced load borne by the main mounting node includes unbalanced force and unbalanced moment, and the unbalanced load borne by the auxiliary mounting node is the unbalanced force. The case where the unbalanced load borne by the mounting node is the largest is regarded as the case where the initial damage of the mounting node is the largest, and the corresponding blade loss part is determined to be the second-stage blade of the power turbine rotor.

6. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 4, characterized in that: The process of determining the blade loss location that causes the maximum unbalanced load on the mounting section during continuous rotation includes the following: Based on whether the engine's main rotor can rotate freely after blades are lost at different locations and the remaining status of the rotor blades, a qualitative analysis of the imbalance during continuous rotation is conducted to determine the imbalance that should be considered for the freely rotating main rotor, thereby determining the blade loss location in the main rotor that causes the maximum unbalance load at the installation section during continuous rotation.

7. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 6, characterized in that: When multiple-stage blades or centrifugal-stage blades of the compressor are lost, the imbalance of the power turbine rotor is equivalent to the normal level; when the first-stage blades of the gas turbine are lost, the imbalance of the gas generator rotor should consider the imbalance corresponding to a single first-stage blade; when the second-stage blades of the gas turbine are lost, the imbalance of the gas generator rotor should consider the imbalance corresponding to a single second-stage blade; when the first-stage blades of the power turbine are lost, the imbalance of the gas generator rotor is equivalent to the normal level; when the second-stage blades of the power turbine are lost, the imbalance of both the gas generator rotor and the power turbine rotor are equivalent to normal levels.

8. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 5, characterized in that: The leaf loss test consists of the following: After pre-fabricating cracks at the root or outermost mortise of the second-stage blades of the power turbine rotor, complete the engine assembly. When conducting the engine test, increase the main rotor speed to the maximum allowable speed. After staying for a preset time, if the second-stage blades of the power turbine rotor do not break, increase the engine speed until the blades break; alternatively, conduct a power turbine blade shedding test.

9. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 1, characterized in that: The process of conducting a continuous rotation test on the reassembled engine based on the determined atmospheric temperature conditions includes the following: Install strain gauges on the mounting joint to obtain the stress level of the mounting joint during continuous rotation. At the declared minimum altitude and determined atmospheric temperature conditions, increase the Mach number so that the engine main rotor continues to rotate under the action of the airflow until the maximum speed requirement is met. When the continuous rotation time reaches 1 / 2 of the engine's maximum flight time, the Mach number is reduced to 0 and the engine main rotor will stop continuous rotation. After the test, check whether the mounting joint is detached.

10. The method for simulating a continuous rotation test state of a turboshaft engine under blade loss conditions according to claim 9, characterized in that: If the main rotor gets stuck during the continuous rotation test and the test is interrupted, it is necessary to conduct component testing on the installation joint based on the measurement data of the strain gauge to ensure that the installation joint bears the load for 1 / 2 of the maximum flight time of the engine.

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