Method for testing loading capacity of combustion chamber casing

Abstract

The invention aims to provide a combustion chamber casing pressure bearing capacity test method, which comprises the following steps of: obtaining casing pressure resistance and overpressure load of a conformity verification test, obtaining a temperature correction coefficient, obtaining a minimum material performance correction coefficient, and obtaining a most unfavorable geometric dimension correction coefficient, and calculating a final test pressure load according to the product of the case pressure-resistant and overpressure pressure load, the temperature correction coefficient, the minimum material performance correction coefficient and the most unfavorable geometric dimension correction coefficient. Through the test method, the airworthiness conformity of the combustion chamber casing can be verified.

Description

Technical Field

[0001] The invention relates to the field of strength, safety and airworthiness verification of aircraft engines, and in particular to a method for testing the pressure bearing capacity of a combustion chamber casing. Background Art

[0002] The combustion chamber casing is one of the main force transmission components of an aircraft engine. It is part of the core high-pressure casing of an aircraft engine and contains high-speed flowing gas with the highest temperature and pressure in an aircraft engine. In addition, the combustion chamber casing also bears the axial force and torque transmitted by the gas load. Once the combustion chamber casing is ruptured, the combustion pressure, temperature and oil-gas matching in the combustion chamber will change dramatically, and may even cause explosive combustion, directly threatening the safety of the aircraft engine.

[0003] Therefore, the combustion chamber casing, which bears high temperature, high pressure and other important static loads, must have a high safety margin to ensure that the engine does not suffer catastrophic damage. To this end, the airworthiness regulations CCAR33.64 stipulate that the combustion chamber casing cannot fail under extreme loads, and the safety of the combustion chamber casing must be demonstrated through tests or verified analysis methods.

[0004] Casing pressure test is one of the main means to verify the airworthiness compliance of the combustion chamber casing under pressure. It is urgent to develop a test verification method that can better simulate the launch limit state and produce more conservative and reliable results to demonstrate the airworthiness compliance of the combustion chamber casing. Summary of the invention

[0005] The object of the present invention is to provide a method for testing the pressure bearing capacity of a combustion chamber casing, which can verify the airworthiness compliance of the combustion chamber casing.

[0006] A method for testing the pressure bearing capacity of a combustion chamber casing to achieve the above-mentioned purpose comprises the following steps:

[0007] Obtain casing pressure resistance and overpressure loads for compliance verification tests;

[0008] The temperature correction coefficient X1 is obtained by the following formula (1):

[0009]

[0010] The minimum material performance correction factor X2 is obtained by the following formula (2):

[0011]

[0012] The most unfavorable geometric dimension correction factor X3 is obtained by the following formula (3):

[0013]

[0014] The final test pressure load is calculated based on the product of the casing pressure resistance and overpressure loads, the temperature correction factor, the minimum material property correction factor and the most unfavorable geometric dimension correction factor.

[0015] In one or more embodiments, the method further comprises:

[0016] Obtain other static load influence factors X4, including:

[0017] Calculate the stress and strain distribution of the casing under the action of cavity pressure load and cavity pressure, axial force and torque load respectively;

[0018] Select multiple locations with high stress concentration to determine the impact of axial force and torque load on casing stress; and

[0019] The influence coefficient is calculated according to the proportional relationship between the stress of the casing after the cavity pressure load is applied alone and the stress of the casing after the pressure, axial force and torque load are applied. If the influence coefficients of the selected key positions are all less than 1, the pressure load is not corrected. If the influence coefficient is greater than 1, the maximum value is selected as the other static load influence coefficient to correct the final test pressure load.

[0020] In one or more embodiments, an actuator is used to apply axial force and torque to the casing during testing.

[0021] In one or more embodiments, the method further comprises:

[0022] Considering the influence ratio of the test piece plug cover design on the casing stress, the first load magnification factor is obtained;

[0023] The final test pressure load is corrected using the first load magnification factor.

[0024] In one or more embodiments, the first load magnification factor is obtained by finite element simulation, comprising the following steps:

[0025] Calculate the stress and strain distribution of the real engine structure under high temperature working environment load conditions;

[0026] Calculate the stress and strain distribution of the casing pressure test piece with test plug and cover under the same high temperature working environment load condition;

[0027] Compare the stress values ​​of the two calculation models at the same position of the casing structure. The positions to be compared include all stress concentration positions near the plug and cover.

[0028] The stress ratios at these positions are calculated, and the maximum stress ratio is selected as the first load magnification factor.

[0029] In one or more embodiments, the method further comprises:

[0030] Considering the influence ratio of the front and rear transition sections on the casing stress, the second load amplification factor is obtained;

[0031] The final test pressure load is corrected using the second load magnification factor.

[0032] In one or more embodiments, the second load magnification factor is obtained by finite element simulation, comprising the following steps:

[0033] Calculate the stress and strain distribution of the real engine structure under high temperature working environment load conditions;

[0034] Calculate the stress and strain distribution of the casing pressure test piece with front and rear transition sections under the same high temperature working environment load conditions;

[0035] Compare the stress values ​​of the two calculation models at the same position of the casing structure. The positions to be compared include all stress concentration positions near the front and rear transition section installation edges, the installation seat and the hole edge.

[0036] The stress ratios at these positions are calculated, and the maximum stress ratio is selected as the second load magnification factor.

[0037] In one or more embodiments, the casing pressure resistance and overpressure loads are obtained with reference to airworthiness provisions.

[0038] The beneficial effects of the present invention are:

[0039] This combustion chamber casing pressure bearing capacity test method takes into account the dispersion of various data, uses the ratio of the actual material mechanical properties of the test casing with the furnace to the minimum material mechanical properties to correct the test pressure load, and uses the ratio of the maximum wall thickness caused by the tolerance of the test piece to the minimum wall thickness caused by the tolerance of the test piece as the correction coefficient of the casing pressure load to ensure that the individual casing test can correctly verify that the casing structure can meet the airworthiness requirements and the engine combustion chamber casing is reliable. At the same time, this method proposes a casing airworthiness compliance verification method that simulates the high temperature environment of the engine through load correction at room temperature, which greatly reduces the difficulty of high temperature casing pressure testing, avoids the need for heaters, and can reduce test costs.

[0040] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0042] Figure 1 A schematic diagram of a flow chart according to an embodiment of a method for testing the pressure bearing capacity of a combustion chamber casing is shown;

[0043] Figure 2 as well as Figure 3 A schematic diagram of a combustion chamber casing according to an embodiment is shown. DETAILED DESCRIPTION

[0044] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0046] According to the requirements of airworthiness clauses, the casing pressure test needs to develop a correct and relatively conservative load spectrum, consider the equivalence of high-temperature working environment and normal temperature test, consider the influence of other static loads (axial force, torque), consider the test adapter fixture, and the influence of sealing structure on casing stiffness. In addition, airworthiness compliance verification must consider the dispersion of various types of data to characterize the minimum safety margin of the structure to meet the requirements. Therefore, when using a single casing for testing, it is necessary to consider the most adverse effects of machining dimensional errors and the effects of the dispersion of mechanical properties of casing preparation materials to ensure that individual casing tests can correctly verify that the casing structure can meet airworthiness requirements and that the engine combustion chamber casing is reliable.

[0047] Based on the above factors, according to some embodiments of the present application, a method for testing the pressure bearing capacity of a combustion chamber casing is provided, which can more reasonably demonstrate the safety of the combustion chamber casing.

[0048] Figure 1 The flow chart of one embodiment of the combustion chamber casing pressure bearing capacity test method is shown. The combustion chamber casing pressure bearing capacity test method comprises the following steps:

[0049] Step S1: Obtain the casing pressure resistance and overpressure load P0 for the compliance verification test. In a specific embodiment, the selection is made with reference to CCAR33.64. The requirements of CCAR33.64 are listed in the following table. In this embodiment, the casing pressure resistance and overpressure load P0 for the test can be selected according to a) in the following table.

[0050]

[0051] Step S2: Obtain the temperature correction coefficient X1 by the following formula (1):

[0052]

[0053] In order to reduce the difficulty, cost and safety risks of the test, the casing pressure test is carried out at room temperature. However, the material strength of the casing in the high-temperature working environment is lower than that of the material at room temperature. If the casing is subjected to pressure test at room temperature, the attenuation of the casing material strength caused by the high working temperature can be equivalent to the damage caused by increasing the test pressure at room temperature. The increase in test pressure can be achieved by correcting the casing pressure resistance and overpressure load P0 through the temperature correction coefficient X1 obtained by formula (1), so that the test can be carried out at room temperature, and the influence of the equivalent high-temperature environment on the casing is corrected by the pressure load. No heating equipment is required, which reduces the difficulty and safety risks of the test.

[0054] Step S3: Obtain the minimum material performance correction factor X2 using the following formula (2):

[0055]

[0056] The airworthiness compliance verification test can be demonstrated through a single casing pressure test. When using a single casing for pressure testing, it is necessary to consider: the individual casing materials have dispersion, whether the casing test results are the results under the most stringent conditions, and whether it can prove that the casing design meets the requirements. By taking the ratio of the material ultimate strength measured by the casing furnace and the minimum performance of the casing material as the correction coefficient of the casing pressure load, as shown in formula (2), the test pressure load is amplified to ensure that the single casing test can represent the minimum safety margin of the structure.

[0057] Step S4: Obtain the most unfavorable geometric dimension correction coefficient X3 through the following formula (3):

[0058]

[0059] The airworthiness compliance verification test can be demonstrated through a single casing pressure test. When a single casing is used for pressure testing, it is also necessary to consider: considering the most adverse impact of machining dimensional errors, whether the test results of this casing are the results under the most stringent conditions, and whether it can prove that the casing design meets the requirements. If the casing wall thickness increases within the tolerance range, the load-bearing capacity will increase, otherwise, the load-bearing capacity will decrease. By using the ratio of the maximum wall thickness of the test piece caused by the tolerance to the minimum wall thickness of the test piece caused by the tolerance as the correction coefficient for the casing pressure load, as shown in formula (3), the test pressure load is amplified to ensure that the single casing test can represent the minimum safety margin of the structure.

[0060] Finally, the final test pressure load P is calculated based on the casing pressure resistance and overpressure load P0, temperature correction factor X1, minimum material performance correction factor X2 and most unfavorable geometric dimension correction factor X3. The calculation method is shown in the following formula (4):

[0061] P=P0*X1*X2*X3(4).

[0062] The casing pressure airworthiness compliance verification test can be carried out based on the determined final test pressure load P.

[0063] This combustion chamber casing pressure bearing capacity test method takes into account the dispersion of various data, uses the ratio of the actual material mechanical properties of the test casing with the furnace to the minimum material mechanical properties to correct the test pressure load, and uses the ratio of the maximum wall thickness caused by the tolerance of the test piece to the minimum wall thickness caused by the tolerance of the test piece as the correction coefficient of the casing pressure load to ensure that the individual casing test can correctly verify that the casing structure can meet the airworthiness requirements and the engine combustion chamber casing is reliable. At the same time, this method proposes a casing airworthiness compliance verification method that simulates the high temperature environment of the engine through load correction at room temperature, which greatly reduces the difficulty of high temperature casing pressure testing, avoids the need for heaters, and can reduce test costs.

[0064] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0065] In an optional embodiment, the combustion chamber casing pressure bearing capacity test method further includes step S5: obtaining other static load influence coefficients X4, which include:

[0066] Calculate the stress and strain distribution of the casing under the action of cavity pressure load and cavity pressure, axial force and torque load respectively;

[0067] Select several locations with high stress concentration to determine the effect of axial force and torque load on casing stress;

[0068] The influence coefficient is calculated according to the proportional relationship between the stress of the casing after the cavity pressure load is applied alone and the stress of the casing after the pressure, axial force and torque load are applied. If the influence coefficients of the selected key positions are all less than 1, no correction is made to the pressure load. If the influence coefficient is greater than 1, the maximum value is selected as the other static load influence coefficient X4 to correct the pressure load.

[0069] It is understood that other static loads referred to herein include axial force and torque.

[0070] In this embodiment, the final test pressure load P is calculated according to the following formula (5):

[0071] P=P0*X1*X2*X3*X4(5).

[0072] In another optional embodiment, an actuator is used to apply axial force and torque to the casing during the test. At this time, a pressure test is carried out because the chamber pressure, axial force and torque loads act synchronously on the test casing. If this loading method is used, there is no need to use other static load influence coefficients X4 to correct the pressure load. In this way, static loads such as axial force and torque of the casing can be equivalent to pressure loads. During the test, only pressure loads need to be applied, which further reduces the difficulty of the test, thereby simplifying the test process. In this embodiment, formula (4) can be used to calculate the final test pressure load P.

[0073] In one or more embodiments, the combustion chamber casing pressure bearing capacity test method further includes step S6: considering the influence ratio of the test piece plug cover design on the casing stress, obtaining the first load magnification factor X5, and correcting the pressure load to eliminate the influence of structural differences.

[0074] In this embodiment, the final test pressure load P is calculated according to the following formula (6):

[0075] P=P0*X1*X2*X3*X4*X5(6).

[0076] Further, in a specific embodiment, the first load magnification factor X5 is obtained by finite element simulation, including the following steps:

[0077] Calculate the stress and strain distribution of the real engine structure under high temperature working environment load conditions;

[0078] Calculate the stress and strain distribution of the casing pressure test piece with test plug and cover under the same high temperature working environment load condition;

[0079] Compare the stress values ​​of the two calculation models at the same position of the casing structure. The positions to be compared include all stress concentration positions near the plug and cover.

[0080] The stress ratios at these locations are calculated, and the maximum stress ratio is selected as the first load magnification factor X5.

[0081] like Figure 2 as well as Figure 3 A schematic diagram of a combustion chamber casing under an embodiment is shown, as Figures 2 to 3 As shown in the figure, there are various mounting seats and opening features on the combustion chamber casing, which are used to install fuel nozzles, ignition nozzles, etc. When conducting casing pressure tests, these locations need to be sealed with plugs and seals. No leakage occurs during the test and the test can proceed normally. Figure 2 As shown in FIG. 1 , the nozzle mounted on the nozzle mounting seat of the engine combustion chamber casing 101 is sealed by a C-type sealing assembly 103 at the nozzle cover plate 102. During the casing pressure test, in order to ensure reliable sealing, the plug cover is usually designed to be an internal plug-in type, and an O-ring 202 is used for radial sealing, such as Figure 3 As shown. The nozzle plugging cover 201 has a large rigidity, and there are differences in structure between the nozzle cover plate 102 and the ignition nozzle cover plate on the actual engine casing. This difference directly causes the local rigidity of the casing to change, and affects the casing stress under external loads. The following table shows the proportional parameters of the plugging cover under an embodiment:

[0082]

[0083] In the embodiment shown in the above table, the opening of the nozzle mounting seat is selected as the first load amplification factor X5.

[0084] In combination with the above table, in a specific embodiment, when considering the influence ratio of the test piece plugging cover design on the casing stress, the first load magnification coefficient X5 is obtained. When the first load magnification coefficient X5 is a positive value, the load magnification is not considered, and the pressure load is not corrected by the first load magnification coefficient X5. When the first load magnification coefficient X5 is a negative value, the pressure load is corrected by the first load magnification coefficient X5, and the negative maximum value of multiple coefficients is selected as the first load magnification coefficient X5. For example, the influence ratio of the plugging cover at the nozzle mounting seat opening is selected in the above table as the first load magnification coefficient X5.

[0085] In one or more embodiments, the combustion chamber casing pressure bearing capacity test method further includes step S7:

[0086] Considering the influence ratio of the front and rear transition sections on the casing stress, the second load amplification factor X6 is obtained, and the pressure load is corrected to eliminate the influence of structural differences. In this embodiment, the final test pressure load P is calculated according to the following formula (7):

[0087] P=P0*X1*X2*X3*X4*X5*X6(7).

[0088] In addition to the sealing structure of the plug and cover, the front and rear transition sections of the casing pressure test may also be different from the compressor and turbine casing structures connected to the front and rear of the engine casing. This difference is also considered from the aspects of manufacturing and processing costs and test costs. Usually, front and rear transition sections with lower material properties, simpler configurations and thicker walls are used. This difference directly affects the stress of the casing installation edge, mounting seat and hole edge. Similarly, in the test, the influence ratio of the front and rear transition sections on the casing stress can be taken into account in the casing pressure test as the second load magnification factor X6.

[0089] Further, in a specific embodiment, the second load magnification factor X6 is obtained by finite element simulation, including the following steps:

[0090] Calculate the stress and strain distribution of the real engine structure under high temperature working environment load conditions;

[0091] Calculate the stress and strain distribution of the casing pressure test piece with front and rear transition sections under the same high temperature working environment load conditions;

[0092] Compare the stress values ​​of the two calculation models at the same position of the casing structure. The positions to be compared include all stress concentration positions near the front and rear transition section installation edges, the installation seat and the hole edge.

[0093] The stress ratios at these locations are calculated, and the maximum stress ratio is selected as the second load magnification factor X6.

[0094] In some specific embodiments, when the second load magnification coefficient X6 is a positive value, load amplification is not considered, and the pressure load is not corrected using the second load magnification coefficient X6; when the second load magnification coefficient X6 is a negative value, the pressure load is corrected using the second load magnification coefficient X6, and the negative maximum value among multiple coefficients is selected as the second load magnification coefficient X6.

[0095] By introducing the first load magnification factor X5 and the second load magnification factor X6, this method fully considers the influence of the test adapter and the sealing structure simulation on the stiffness of the casing itself, the dispersion of the casing preparation materials, and the influence of the process dimensional error, ensuring that the individual casing test can correctly verify that the casing structure can meet the airworthiness requirements, and the test results are reasonable, conservative, and reliable. At the same time, the front and rear transition sections of the casing pressure test, the plugs and covers of the test mounting seat, etc. are different from the configuration of the engine installation state, resulting in changes in stiffness and casing stress distribution. This patent compares the stress analysis of the installed casing and the pressure test piece casing, selects the maximum impact position, and uses this impact coefficient as the test pressure load magnification coefficient, so that the test conditions can represent the worst conditions.

[0096] According to the method proposed in one or more of the aforementioned embodiments, a compliance verification method and a specific implementation method that meet the requirements of a) and b) in the airworthiness clause are effectively realized. This method solves the problem of characterizing the worst case, and at the same time solves how the test simulation component configuration and test conditions can correctly be equivalent to the actual engine casing and actual conditions, and more reasonably demonstrates the safety of the combustion chamber casing.

[0097] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for testing the pressure bearing capacity of a combustion chamber casing, characterized in that: The steps include: Obtain casing pressure resistance and overpressure loads for compliance verification tests; The temperature correction coefficient X1 is obtained by the following formula (1): The minimum material performance correction factor X2 is obtained by the following formula (2): The most unfavorable geometric dimension correction factor X3 is obtained by the following formula (3): The final test pressure load is calculated based on the product of the casing pressure resistance and overpressure loads, the temperature correction factor, the minimum material property correction factor and the most unfavorable geometric dimension correction factor.

2. The combustion chamber casing pressure bearing capacity test method according to claim 1, characterized in that: The method further comprises: Obtain other static load influence factors X4, including: Calculate the stress and strain distribution of the casing under the action of cavity pressure load and cavity pressure, axial force and torque load respectively; Select multiple locations with high stress concentration to determine the impact of axial force and torque load on casing stress; and The influence coefficient is calculated according to the proportional relationship between the stress of the casing after the cavity pressure load is applied alone and the stress of the casing after the pressure, axial force and torque load are applied. If the influence coefficients of the selected key positions are all less than 1, the pressure load is not corrected. If the influence coefficient is greater than 1, the maximum value is selected as the other static load influence coefficient to correct the final test pressure load.

3. The combustion chamber casing pressure bearing capacity testing method according to claim 1, characterized in that: During the test, an actuator is used to apply axial force and torque to the casing.

4. The combustion chamber casing pressure bearing capacity testing method according to claim 1, characterized in that: The method further comprises: Considering the influence ratio of the test piece plug cover design on the casing stress, the first load magnification factor is obtained; The final test pressure load is corrected using the first load magnification factor.

5. The combustion chamber casing pressure bearing capacity testing method according to claim 4, characterized in that: The first load magnification factor is obtained by finite element simulation, comprising the following steps: Calculate the stress and strain distribution of the real engine structure under high temperature working environment load conditions; Calculate the stress and strain distribution of the casing pressure test piece with test plug and cover under the same high temperature working environment load condition; Compare the stress values ​​of the two calculation models at the same position of the casing structure. The positions to be compared include all stress concentration positions near the plug and cover. The stress ratios at these positions are calculated, and the maximum stress ratio is selected as the first load magnification factor.

6. The combustion chamber casing pressure bearing capacity testing method according to claim 1, characterized in that: The method further comprises: Considering the influence ratio of the front and rear transition sections on the casing stress, the second load amplification factor is obtained; The final test pressure load is corrected using the second load magnification factor.

7. The combustion chamber casing pressure bearing capacity testing method according to claim 6, characterized in that: The second load magnification factor is obtained by finite element simulation, comprising the following steps: Calculate the stress and strain distribution of the real engine structure under high temperature working environment load conditions; Calculate the stress and strain distribution of the casing pressure test piece with front and rear transition sections under the same high temperature working environment load conditions; Compare the stress values ​​of the two calculation models at the same position of the casing structure. The positions to be compared include all stress concentration positions near the front and rear transition section installation edges, the installation seat and the hole edge; The stress ratios at these positions are calculated, and the maximum stress ratio is selected as the second load magnification factor.

8. The combustion chamber casing pressure bearing capacity testing method according to claim 1, characterized in that: The casing pressure resistance and overpressure loads are obtained with reference to the airworthiness provisions.

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