Static test design method and device for tail thrust propeller central piece

Abstract

The application belongs to the technical field of helicopter strength, and particularly relates to a static force test design method and device for a tail thrust propeller central part. The application comprises test load formulation, test load application steps, debugging methods and other aspects. The test method in the application can effectively check and verify the static strength of the tail thrust propeller central part by designing reasonable test load and load application method to perform static force test on the tail thrust propeller central part. The static strength of the tail thrust propeller central part under the centrifugal load twice the maximum centrifugal force generated by the thrust propeller when rotating in the limited use range and the static strength of the tail thrust propeller central part under the influence of the main rotor aerodynamic load of the helicopter can be checked at the same time. The tail thrust propeller central part adjustment test can be used to solve the accuracy of the application of the flapping bending moment and the pendulum bending moment affected by the centrifugal force unloading, and avoid repeated load adjustment to cause structural damage and affect the accuracy of the test results.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of helicopter strength, and particularly relates to a static force test design method and device for a tail thrust propeller central part. BACKGROUND

[0002] The cruising speed of a conventional single-rotor tail propeller helicopter is generally not more than 300 Km / h due to the limitation of the configuration (front propeller wave). In order to solve the problems of slow flight speed, low flight height and poor maneuverability of the conventional configuration helicopter, a high-speed helicopter emerges as the times require. At present, the high-speed helicopter technology has become a technical commanding point of a new generation of helicopter equipment and products. The coaxial high-speed helicopter adopts a coaxial rigid counter-rotating double-rotor tail thrust propeller configuration, can realize 400 Km / h high-speed cruising, and is one of the mainstream configurations of modern high-speed helicopters.

[0003] The tail thrust propeller provides forward thrust for the coaxial high-speed helicopter in medium and high-speed flight, so as to break through the speed limit and realize high-speed flight, and is an important component of the coaxial high-speed helicopter. The tail thrust propeller central part is located at the center of the tail thrust propeller and is a key component of the entire tail thrust propeller. Whether the strength of the tail thrust propeller central part can meet the requirements is one of important signs of whether the design of the tail thrust propeller is successful. At present, the method for verifying whether the important structure strength of a helicopter is qualified is still mainly test. Therefore, it is essential to test and examine the tail thrust propeller central part in the engineering design stage to ensure the safe use of the helicopter.

[0004] In order to verify whether the static strength of the tail thrust propeller central part is qualified, the key lies in adopting a reasonable test examination method. The tail thrust propeller is a propeller configuration, and compared with the helicopter rotor, has its special provisions: the tail thrust propeller central part, as a propeller hub and a propeller blade fixing device of a detachable propeller blade, must withstand the centrifugal load twice the maximum centrifugal force generated by the propeller when rotating within the limited use range of the propeller. Meanwhile, the tail thrust propeller also bears the influence of the aerodynamic load of the main rotor of the helicopter, and the structure bearing environment becomes more complex than that of the ordinary propeller. In this case, the static strength of the tail thrust propeller central part must be separately examined and verified, and the test method needs to be specially designed.

[0005] The test method in the scheme can effectively examine and verify the static strength of the tail thrust propeller central part by designing a reasonable test load and a load application method to perform the static force test of the tail thrust propeller central part. SUMMARY

[0006] The application aims to provide a static force test design method for a tail thrust propeller central part of a high-speed helicopter, which includes the aspects of test load formulation, test load application steps and debugging method.

[0007] The application provides a static force test design method and device for a tail thrust propeller central part,

[0008] In all loading conditions of static test, the loading sequence is to add centrifugal force first, then add the edgewise and flapwise bending moments, and the smaller value of the edgewise and flapwise bending moments reaches the required proportion to be loaded to the position; the unloading sequence is to unload the edgewise and flapwise bending moments first, and then unload the centrifugal force.

[0009] Considering the influence of centrifugal force unloading, an adjustment test is designed when the edgewise and flapwise bending moments are applied.

[0010] The first step is to adjust the test, gradually load to the limit load centrifugal force first, then apply 15%-25% of the limit load edgewise and flapwise bending moments at the butt joint surface of the tail push blade, record the size of the edgewise force and the flapwise force at this time; increase the edgewise and flapwise bending moments at the butt joint surface of the tail push blade by 5%-10% of the limit load proportion, record the size of the edgewise force and the flapwise force at this time, and so on; observe and record the size of the edgewise force and the flapwise force adjustment proportion within the range of not more than 40% of the limit load.

[0011] The second step is a pre-test, and the pre-test load is selected as 40% of the limit load condition 2. The limit load condition 2 selects the limit load with an additional safety margin coefficient;

[0012] The third step is a limit load condition test, which is gradually coordinated to the limit load based on the first step by not more than 5%-10% of the limit load increment at each level, and deformation observation should be carried out under each test load. When loaded to the limit load, the test begins. When the limit load condition is developed, the maximum edgewise bending moment, the maximum flapwise bending moment, and the maximum centrifugal force in the load spectrum are selected as the limit load condition.

[0013] The fourth step is a limit load condition 1 test, which is gradually coordinated to the limit load condition 1 by not more than 10% of the limit load condition 1 increment at each level. Deformation observation should be carried out under each test load. When loaded to the limit load condition 1, the test begins. The limit load condition 1 applies a load of twice the maximum centrifugal force in the load spectrum.

[0014] The fifth step is a limit load condition 2 test, which is gradually coordinated to the limit load by not more than 10% of the limit load condition 2 increment at each level. When the limit load is exceeded, it is gradually coordinated to the limit load condition 2 by not more than 5% of the limit load condition 2 increment at each level. Deformation observation should be carried out under each test load. When coordinated to not less than 100% of the limit load condition 2, the test begins.

[0015] The sixth step is a static strength margin test. After loaded to 100% of the limit load condition 2, the centrifugal force remains unchanged, and the edgewise and flapwise bending moments are gradually coordinated by not more than 5% of the limit load condition 2 increment at each level. The test begins until the test piece is destroyed, and the test ends.

[0016] Further, the tail push propeller is a rigid rotor structure, and centrifugal force, flapping bending moment and edgewise bending moment at the butt joint surface of the tail propeller blade are selected as test loads. The static test needs to verify whether the limit load condition and the ultimate load condition meet the strength requirement, so the limit load condition and the ultimate load condition need to be reasonably designed.

[0017] Further, when the limit load condition is formulated, the maximum flapping bending moment, the maximum edgewise bending moment and the maximum centrifugal force in the load spectrum are selected as the limit load condition.

[0018] Further, when the ultimate load condition is formulated, the method of respectively examining the ultimate load of the centrifugal force and the flapping and edgewise bending moment is adopted, and the ultimate load condition is divided into two types: the ultimate load condition 1 applies a load of twice the maximum centrifugal force in the load spectrum to examine the ultimate condition of the centrifugal force; and the ultimate load condition 2 selects a limit load with an additional safety margin coefficient to examine the ultimate condition of the flapping and edgewise bending moment at the rated speed.

[0019] Further, when the flapping and edgewise bending moment of the tail push propeller central part is loaded, the flapping shear force and the edgewise shear force on the blade dummy part are used for loading, and the loading points are determined according to the ratio of the flapping force to the flapping bending moment and the ratio of the edgewise force to the edgewise bending moment at the butt joint surface of the tail propeller blade.

[0020] Further, the transverse shear force is applied at the loading point through an actuator, and the load at the butt joint surface of the tail propeller blade is calculated by interpolation of more than two strain gauges, so as to control the test load.

[0021] Further, the tail push propeller central part test is a multi-branch loading, and the test equipment includes a load control and strain measurement system, a loading actuator, a force sensor and a data acquisition system. The tail push propeller central part is fixed on a test bench, and a tail propeller blade dummy part is installed at each branch butt joint surface of the tail push propeller central part. More than two strain gauges are attached to appropriate positions on the dummy part to measure the test load. A centrifugal force actuator, a flapping force actuator and an edgewise force actuator are sequentially installed, a data acquisition system acquires data, and a loading system adjusts the force value to form a complete test system.

[0022] Further, the test criterion is that: after the limit load condition test is completed, the test part should not have harmful permanent deformation; after the ultimate load condition 1 test and the ultimate load condition 2 test are completed, the test part should not be damaged; and the test after 100% of the ultimate load condition 2 is a static strength margin test.

[0023] The beneficial effects of the present application are:

[0024] (1) The static test method of the tail pusher central part is established, which can simultaneously examine the static strength of the tail pusher central part under the influence of the centrifugal load twice the maximum centrifugal force generated by the pusher within the limited use range and the aerodynamic load of the main rotor of the helicopter;

[0025] (2) The tail pusher central part adjustment test designed by the application can be used to solve the accuracy of the application of the flapping bending moment and the pendulum bending moment affected by the centrifugal force unloading, and avoid the structural damage caused by repeated load adjustment to affect the accuracy of the test results.

[0026] For the configuration of the high-speed helicopter pusher, a static test method of the tail pusher central part is designed; the application establishes a limited load condition, a limit load condition 1 and a limit load condition 2, which can examine the static strength of the tail pusher central part under the influence of the aerodynamic load of the main rotor of the helicopter on the basis of meeting the requirement that the tail pusher central part as the pusher hub and the blade fixing device of the detachable blade must withstand the centrifugal load twice the maximum centrifugal force generated by the pusher within the limited use range; the application establishes the static test sequence and test steps of the tail pusher central part; the application designs the tail pusher central part adjustment test, which can be used to solve the accuracy of the application of the flapping bending moment and the pendulum bending moment affected by the centrifugal force unloading; the application establishes the static strength margin test of the tail pusher central part, which can be used to cope with the influence caused by the adjustment of the structural design load spectrum. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of the overall system of the test;

[0028] Figure 2 is a schematic diagram of the test loading of the tail pusher single arm;

[0029] Figure 3 is a test flowchart. DETAILED DESCRIPTION

[0030] Figure 1is the schematic diagram of the overall system of the test: the tail thrust propeller central piece test is a coordinated loading of multiple arms. The load control and strain measurement system of the computer controls the centrifugal force actuator cylinder, the flapping force actuator cylinder and the oscillation force actuator cylinder to respectively apply centrifugal force, flapping force and oscillation force (the load size is judged by the computer through sensor feedback). The centrifugal force is applied to the tail propeller blade dummy through a steel wire rope and a loading joint. The flapping force is applied to the tail propeller blade dummy through a loading joint. The oscillation force is applied to the tail propeller blade dummy through a connecting rod and a loading joint (the load on the dummy is fed back to the computer through strain gauges to judge the load size). The load is transmitted to the tail thrust propeller central piece through the tail propeller blade dummy (the load on the tail thrust propeller central piece is fed back to the computer through strain gauges to judge the load size). The load and strain of each step are output by the computer to obtain test data.

[0031] Figure 2 is the schematic diagram of the single arm test loading of the tail thrust propeller: the tail thrust propeller central piece is fixed on the test bench. Taking a single arm as an example, tail propeller blade dummies are installed on the butt joint surface of each arm. Two or more groups of strain gauges are attached to appropriate positions on the dummies to measure the test load. The centrifugal force actuator cylinder, the flapping force actuator cylinder and the oscillation force actuator cylinder are installed in sequence. The data acquisition system collects data, and the coordinated loading system adjusts the load force value, thus forming a complete test cycle system.

[0032] Figure 3 is the test flowchart. The steps of the entire test are as follows: first, an adjustment test is performed to obtain the flapping force and oscillation force size adjustment ratio; second, a pre-test is performed to check whether the entire test system and the measurement system meet the test technical requirements and to tighten the test piece to eliminate the gap; third, a limit load working condition test is performed to verify the limit load static strength under the influence of the main rotor aerodynamics; fourth, a limit load working condition 1 test is performed to verify the special requirements of the propeller specification for the propeller root fixing device; fifth, a limit load working condition 2 test is performed to verify the limit load static strength under the influence of the main rotor aerodynamics; and finally, a static strength margin test is performed to further explore the static strength margin potential of the central piece to cope with the load spectrum adjustment impact.

[0033] Test principle

[0034] The tail thrust propeller not only bears the aerodynamic load transmitted from the propeller blade, but also is affected by the aerodynamics generated by the main rotor rotation. The central piece structure bears more complex and severe loads than ordinary propeller central pieces. Therefore, when selecting the test load for the tail thrust propeller central piece static test, the centrifugal force, flapping moment and oscillation moment cannot be ignored, and their influence on the tail thrust propeller central piece must be considered.

[0035] The tail pusher is a rigid rotor structure, and the centrifugal force, flapping bending moment and edgewise bending moment at the tail pusher blade butt joint surface are selected as the test load. The static test needs to verify whether the limit load case and the ultimate load case meet the strength requirements, so the limit load case and the ultimate load case need to be reasonably designed.

[0036] When the limit load case is determined, the maximum flapping bending moment, the maximum edgewise bending moment and the maximum centrifugal force in the load spectrum are selected as the limit load case. When the ultimate load case is determined, the method of respectively checking the ultimate load of the centrifugal force, the flapping bending moment and the edgewise bending moment is adopted, and the ultimate load case is divided into two types: the ultimate load case 1 applies twice the load of the maximum centrifugal force in the load spectrum to check the ultimate condition of the centrifugal force; the ultimate load case 2 selects the limit load with an additional safety margin coefficient to check the ultimate condition of the flapping bending moment and the edgewise bending moment at the rated speed.

[0037] When the flapping bending moment and the edgewise bending moment of the tail pusher central part are loaded, the flapping shear force and the edgewise shear force on the blade dummy part are used for loading, and the loading points are determined according to the ratio of the flapping force to the flapping bending moment and the ratio of the edgewise force to the edgewise bending moment at the tail pusher blade butt joint surface. The transverse shear force is applied at the loading point through the actuator cylinder, and the load at the tail pusher blade butt joint surface is calculated by interpolating two or more strain gauges, so as to control the test load.

[0038] Test equipment and arrangement

[0039] The tail pusher central part test is a multi-branch loading, and the test equipment includes a load control and strain measurement system, a loading actuator cylinder, a force sensor and a data acquisition system.

[0040] The tail pusher central part is fixed on the test bench, and the tail pusher blade dummy part is installed on each branch butt joint surface of the tail pusher central part. Two or more strain gauges are attached to the appropriate position of the dummy part to measure the test load. The centrifugal force actuator cylinder, the flapping force actuator cylinder and the edgewise force actuator cylinder are installed in sequence, the data acquisition system acquires data, and the loading system adjusts the loading force value, thus forming a complete test system.

[0041] Test process

[0042] In all loading cases of the static test, the loading sequence is to add the centrifugal force first, and then add the flapping and edgewise bending moments. When loading, the smaller value of the flapping and edgewise bending moments reaches the required proportion, which is considered as loading in place. The unloading sequence is to unload the flapping and edgewise bending moments first, and then unload the centrifugal force.

[0043] Considering the influence of centrifugal force unloading, an adjustment test is designed when the flapping bending moment and the edgewise bending moment are applied.

[0044] First step: adjustment test, first gradually load to the limit load centrifugal force, then apply 15%-25% limit load of the flap and edgewise bending moment at the butt joint surface of the tail propeller blade, record the size of the flap and edgewise force at this time; increase the flap and edgewise bending moment at the butt joint surface of the tail propeller blade by 5%-10% limit load proportion, record the size of the flap and edgewise force at this time, and so on; observe and record the size of the flap and edgewise force within the range of not more than 40% limit load;

[0045] Second step: pre-test, the pre-test load is selected as 40% of the limit load working condition 2. The limit load working condition 2 is selected as the limit load with an additional safety margin coefficient;

[0046] Third step: limit load working condition test, based on the first step, gradually load to the limit load by not more than 5%-10% limit load increment per stage, deformation observation should be carried out under each test load, start the test when loaded to the limit load, the limit load working condition is selected as the maximum flap bending moment, the maximum edgewise bending moment and the maximum centrifugal force in the load spectrum.

[0047] Fourth step: limit load working condition 1 test, gradually load to the limit load working condition 1 by not more than 10% limit load working condition 1 increment per stage, deformation observation should be carried out under each test load, start the test when loaded to the limit load working condition 1, the limit load working condition 1 is selected as the load twice of the maximum centrifugal force in the load spectrum.

[0048] Fifth step: limit load working condition 2 test, gradually load to the limit load by not more than 10% limit load working condition 2 increment per stage, when exceeding the limit load, gradually load to the limit load working condition 2 by not more than 5% limit load working condition 2 increment per stage, deformation observation should be carried out under each test load, start the test when loaded to not less than 100% limit load working condition 2,

[0049] Sixth step: static strength margin test. After loaded to 100% limit load working condition 2, gradually load the flap and edgewise bending moment by not more than 5% limit load working condition 2 increment per stage with the same centrifugal force, start the test until the test piece is destroyed, and the test is ended.

[0050] Test criteria

[0051] After the limit load working condition test of the test piece is completed, the test piece should not have harmful permanent deformation;

[0052] After the limit load working condition 1 test and the limit load working condition 2 test of the test piece are completed, the test piece should not be destroyed;

[0053] The test after 100% limit load working condition 2 is the static strength margin test.

[0054] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. The specific embodiments described above are provided for purposes of illustration only and are not intended to be limiting, with the true scope being indicated by the following claims, along with their full range of equivalents.

Claims

1. A static test design method for a central component of a tail thrust propeller, characterized in that, In all loading conditions of the static test, the loading sequence is to first apply centrifugal force, then apply swinging and oscillating bending moments. When the smaller of the swinging and oscillating bending moments reaches the required proportion during loading, the loading is considered complete. The unloading sequence is always to first unload the waving and swinging moments, and then unload the centrifugal force; Considering the effect of centrifugal force unloading, an adjustment test is designed when swinging moment and oscillation moment are applied; Step 1: Adjustment Test. First, gradually load the centrifugal force to the limit load. Then, apply flapping and tessellation moments at the tail thruster blade mating surface at 15%-25% of the limit load and record the magnitudes of the flapping and tessellation forces. Increase the flapping and tessellation moments at the tail thruster blade mating surface by 5%-10% of the limit load and record the magnitudes of the flapping and tessellation forces. Continue this process. Observe and record the adjustment ratios of the flapping and tessellation forces within a range not exceeding 40% of the limit load. Step 2: Pre-test, the pre-test load is selected as 40% of the ultimate load condition 2; the ultimate load condition 2 is selected as the limiting load with an additional safety margin factor; Step 3: Limit load condition test. Based on the results obtained in Step 1, load the load gradually at each level with an increment of no more than 5%-10% of the limit load. Deformation should be observed under each level of test load. When the load reaches the limit load, the test begins. When formulating the limit load condition, the maximum swinging moment, the maximum oscillation moment, and the maximum centrifugal force in the load spectrum are selected as the limit load condition. Step 4: Test under ultimate load condition 1. Gradually load the load to ultimate load condition 1 in increments of no more than 10% per level. Deformation should be observed under each level of test load. When the load reaches ultimate load condition 1, the test begins. Ultimate load condition 1 applies a load twice the maximum centrifugal force in the load spectrum. Step 5: Ultimate Load Condition 2 Test. Gradually increase the load to the limiting load in increments not exceeding 10% of the ultimate load condition 2. After exceeding the limiting load, gradually increase the load to the ultimate load condition 2 in increments not exceeding 5% of the ultimate load condition 2. Observe the deformation under each test load. When the load reaches at least 100% of the ultimate load condition 2, begin the test. Step 6: Static strength margin test; After loading to 100% of the ultimate load condition 2, the centrifugal force remains unchanged. The swing and oscillation bending moments are gradually coordinated and loaded at each level with an increment of no more than 5% of the ultimate load condition 2. The test begins and continues until the test piece fails.

2. The static test design method for the central component of a tail thrust propeller according to claim 1, characterized in that, The tail thruster is a rigid rotor structure. The centrifugal force, flapping moment and oscillation moment at the tail thruster blade mating surface are selected as test loads. The static test needs to verify whether the limiting load condition and the ultimate load condition meet the strength requirements. Therefore, the limiting load condition and the ultimate load condition need to be designed reasonably.

3. The static test design method for the central component of a tail thrust propeller according to claim 2, characterized in that, When determining the limiting load conditions, the maximum swing moment, maximum oscillation moment, and maximum centrifugal force in the load spectrum are selected as the limiting load conditions.

4. The static test design method for the central component of a tail thrust propeller according to claim 3, characterized in that, When determining the ultimate load conditions, the method of separately assessing the ultimate loads of centrifugal force and flapping and swaying bending moments is adopted, which is divided into two types: ultimate load condition 1 and ultimate load condition 2. Ultimate load condition 1 applies a load twice the maximum centrifugal force in the load spectrum to assess the ultimate condition of centrifugal force; ultimate load condition 2 selects a limiting load with an additional safety margin factor to assess the ultimate condition of flapping bending moment and swaying bending moment at rated speed.

5. The static test design method for the central component of a tail thrust propeller according to claim 4, characterized in that, When loading the flapping moment and tessellation moment of the tail thruster's central component, the flapping shear force and tessellation shear force on the blade dummy are applied. The loading point is determined based on the ratio of flapping force to flapping moment and the ratio of tessellation force to tessellation moment at the tail thruster blade mating surface.

6. The static test design method for the central component of a tail thrust propeller according to claim 5, characterized in that, A transverse shear force is applied at the loading point through an actuator, and the load at the tail thruster blade mating surface is calculated by interpolation using two sets of strain gauges, thereby controlling the test load.

7. The static test design method for the central component of a tail thrust propeller according to claim 6, characterized in that, The test of the tail thruster central component involves loading multiple outriggers. The test equipment includes a load control and strain measurement system, loading actuators, force sensors, and a data acquisition system. The tail thruster central component is fixed on the test bench, and tail thruster blade dummy components are installed on the mating surfaces of each outrigger. Two or more sets of strain gauges are attached to appropriate positions on the dummy components to measure the test load. Centrifugal force actuators, flapping force actuators, and oscillation force actuators are installed in sequence. The data acquisition system collects data and coordinates the loading system to adjust the loading force values, forming a complete test system.

8. The static test design method for the central component of a tail thrust propeller according to claim 7, characterized in that, Test criteria: After the test specimen is subjected to the limited load condition test, the test specimen should not exhibit harmful permanent deformation; after the test specimen is subjected to the ultimate load condition 1 test and the ultimate load condition 2 test, the test specimen should not be damaged; the test after the ultimate load condition 2 test at 100% is a static strength margin test.

9. An apparatus employing the method according to any one of claims 1-8.

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