Method for assessing the life of a turbine engine component
By combining the wear-over-time relationship of turbine components with stress, the component life can be accurately assessed, solving the problems of high maintenance costs and premature component failure caused by wear in the prior art, and realizing a more effective maintenance strategy.
Patent Information
- Application Number
- CN202180078277.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2020-10-26
- Filing Date
- 2021-10-25
- Publication Date
- 2026-02-06
- Estimated Expiration
- 2041-10-25
AI Technical Summary
Existing technologies cannot accurately assess the lifespan of turbine components because they do not consider the geometric changes caused by component wear over time, which affect the applied stress, leading to high maintenance costs and premature component failure.
By representing the stress applied to the component as a function of component wear, and combining the relationship between wear and time, the average damage of the component is determined, and the component's life is calculated by integration, taking into account the damage of the component during failure.
This enables more accurate assessment of turbine component lifespan, reduces unnecessary maintenance and replacement, lowers maintenance costs, and improves component utilization.
Smart Images
Figure CN116648610B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to the field of turbomachines. In particular, the present invention aims at assessing the lifetime of a turbomachine component taking into account the wear development over the turbomachine operating time. BACKGROUND
[0002] During the operation of a turbomachine, the components of the turbomachine are subjected to forces, friction and mechanical stresses. As a result, the components gradually wear over the turbomachine operating time. The operating time of a turbomachine equipped with components is usually measured in the number of turbomachine operating cycles.
[0003] The wear easily modifies the geometry of the component, i.e. the outer surface of the component, for example, when the wear appears as friction marks that indent the component over a certain depth and / or when the wear appears as surface irregularities.
[0004] A new component, which has not yet undergone any turbomachine operating cycle, is zero-worn. The wear of the component increases over the operation of the turbomachine until it leads to the failure of the component.
[0005] The damage of a component is a value that represents the wear of the component. The damage varies between zero damage for a non-worn component and the damage of the component at the time of failure.
[0006] First, the component undergoes an initial damage, i.e. a damage that does not modify the geometry of the component, which has a geometry identical to the geometry at the time of its manufacture. Second, the component undergoes a propagation damage, i.e. a damage once the geometry of the component is modified, for example, the appearance of the friction mark features of the wear.
[0007] The lifetime of a component is equal to the number of turbomachine operating cycles that the component can withstand before failure, i.e. the number of turbomachine operating cycles that the component can withstand before its damage reaches the damage at the time of failure.
[0008] By assessing the lifetime of a turbomachine component, it is possible to define maintenance criteria to bring the component back to flight status or, on the contrary, to stop using the component for maintenance or replacement purposes.
[0009] Currently, the lifetime of a turbomachine component is assessed based on the stresses and temperatures to which the component is subjected, assuming that the geometry of the component remains unchanged during the operation of the turbomachine. Thus, in this approach, the lifetime of the component is determined for a given geometry without taking into account any possible development of the wear of the component and thus of the geometry of the component during the subsequent operation of the turbomachine. The stresses applied to the component, i.e. the stresses inside the component, are assessed for this determined component geometry. Thus, the stresses applied to the component are constant over the turbomachine operating time.
[0010] Moreover, another hypothesis is that the average damage of a component over each turbine operating cycle is constant, i.e. that the cumulative damage of a component varies linearly with the turbine operating time until the component fails.
[0011] Thus, the current method simply evaluates the lifetime of a component for a given geometry without taking into account the possible evolution of the wear of the component and thus of its geometry over time.
[0012] However, the geometry of certain components of a turbine can be affected by an evolution of wear over the turbine operating time. For example, the wear of a small number of passes in a low-pressure compressor disc is an evolving wear which modifies the geometry of the component.
[0013] The stresses applied to a component depend on the geometry of the component, the lifetime of which is evaluated according to these stresses. Thus, the lifetime of a component depends on the evolution of the geometry of the component over the turbine operating time and thus on the evolution of the wear of the component over the turbine operating time.
[0014] Thus, the damage of a component, in particular the propagation damage after the appearance of wear, does not vary linearly with time. In particular, the more wear a component exhibits, the greater the stresses applied to the component (stress concentration effect) and thus the greater the damage of the component over each turbine operating cycle. Thus, the curve representing the propagation damage as a function of time is increasing, convex and non-linear.
[0015] Thus, the current method does not make it possible to accurately evaluate the lifetime of a component since the wear evolves over the turbine operating time and the stresses applied to the component depend on the wear of the component.
[0016] Thus, in order to avoid the risk of easy failure of the components, these components must be retired early without performing the optimal number of flight hours. The components must be repaired or replaced very often. The number of unavailable components is quite significant, the maintenance costs are high and the maintenance is very heavy since it must be performed very frequently. SUMMARY
[0017] One object of the application is to provide a method for evaluating the lifetime of a turbine component which makes it possible to more accurately evaluate the lifetime of a component by taking into account the evolution of the wear of the component as a function of the turbine operating time compared to the prior art.
[0018] Another object of the application is to provide a method for evaluating the lifetime of a turbine component which makes it possible to develop improved maintenance criteria.
[0019] The application relates to a method for evaluating the lifetime of a turbine component, the method comprising the following steps:
[0020] S1 : determining the average damage of the component as a function of time, based on a relation expressing the stresses applied to the component as a function of the wear of the component and a relation expressing the wear of the component as a function of time;
[0021] S2: determining the damage of the component at failure;
[0022] S3: determining the cumulative damage of the component corresponding to the damage of the component at failure, said cumulative damage corresponding to the integral of the average damage as a function of time between an initial time and a final time: and
[0023] S4: deriving therefrom the lifetime of the component, said lifetime corresponding to said final time.
[0024] Certain preferred but non-limiting features of the above method are as follows, used alone or in combination:
[0025] The step S1 of determining the average damage of the component as a function of time comprises a step S11 defining several different wears of the component, and step S11 comprises, for each defined wear of the component, the following steps performed:
[0026] - S12: determining the geometry of the component, based on the wear defined in step S11, in order to determine a relation expressing the geometry of the component as a function of the wear;
[0027] - S13: determining the stresses applied to the component, based on the geometry of the component determined in step S12, in order to determine a relation expressing the stresses applied to the component as a function of the wear;
[0028] - S14: determining the lifetime of the component at constant wear, based on the stresses applied to the component determined in step S13, in order to determine a relation expressing the lifetime of the component at constant wear as a function of the wear;
[0029] - S15: determining the average damage of the component, based on the lifetime of the component at constant wear determined in step S14, in order to determine a relation expressing the average damage of the component as a function of the wear.
[0030] The step S1 of determining the average damage of the component as a function of time also comprises a step S16. Step S16 comprises determining the average damage of the component as a function of time, based on a relation expressing the average damage of the component as a function of the wear and a relation expressing the wear as a function of time.
[0031] The relation expressing the average damage of the component as a function of the wear is equal to the inverse of the relation expressing the lifetime of the component at constant wear as a function of the wear.
[0032] The method is implemented to assess the lifetime of a low-pressure compressor disc.
[0033] The relationship expressing the wear of the component as a function of time is the relationship expressing the wear depth as a function of time.
[0034] The damage of the component at failure is equal to 1. BRIEF DESCRIPTION OF DRAWINGS
[0035] Other characteristics, objects and advantages of the application will become apparent from the following detailed description, given by way of non-restrictive example, to be read with reference to the accompanying drawings:
[0036] Figure 1 is a block diagram representing the steps of the method according to an embodiment of the application.
[0037] Figure 2 is a block diagram representing the steps of determining the average damage as a function of time according to an embodiment of the application.
[0038] Figure 3 is a graph showing the evolution of the lifetime of a component as a function of the wear of the component for a wear assumed constant over time, where the lifetime is assessed in the method according to an embodiment of the application.
[0039] Figure 4 is a graph showing the evolution of the average damage of a component as a function of the wear for a wear assumed constant over time, where the average damage is determined in the method according to an embodiment of the application.
[0040] Figure 5 is a graph showing the evolution of the average damage of a component as a function of time, where the average damage is determined in the method according to an embodiment of the application.
[0041] Figure 6a and Figure 6b is a side view of a component of a turbomachine compressor comprising said component, the lifetime of which can be assessed by the assessment method according to an embodiment of the application. DETAILED DESCRIPTION
[0042] The method for assessing the lifetime DDV of a turbomachine component, shown by way of non-restrictive example in Figure 1 , comprises the following steps:
[0043] S1 : determining the average damage E moy(t) of the component as a function of time, based on a relationship σ(u) expressing the stress applied to the component as a function of the wear of the component and a relationship u(t) expressing the wear of said component as a function of time;
[0044] S2: determining the damage E rupt of the component at failure;
[0045] S3: determining a cumulative damage E_cum of the component corresponding to a damage E_rupt of the component at failure, wherein said cumulative damage E_cum corresponds to an integral of an average damage E_moy(t) as a function of time between an initial time t_0 and a final time t_rupt:
[0046] and
[0047] S4: deriving therefrom a lifetime DDV of the component, wherein said lifetime DDV corresponds to the final time t_rupt.
[0048] Thus, the average damage E_moy(t) of the component as a function of time used to determine the lifetime DDV of the component is determined based on a relation σ(u) representing the stress applied to the component as a function of the wear of the component and a relation u(t) representing the wear of the component as a function of time.
[0049] Thus, the described method makes it possible to evaluate the lifetime DDV of the component taking into account the development of the wear of the component during the operation of the turbomachine. The method can be applied to any turbomachine component, in particular to any component whose wear develops with the operating time of the turbomachine. In particular, the method can determine the damage of the component at propagation and at incipient when the wear of the component modifies its geometry.
[0050] The described method can take into account the fact that the development of the wear of the component leads to a modification of the geometry of the component, which leads to a modification of the stress applied to the component, which leads to a modification of the lifetime of the component. In particular, the greater the wear of the component, the greater the stress within the component (stress concentration effect) and therefore the greater the damage of the component for each turbomachine operating cycle.
[0051] Thus, the described method can more accurately evaluate the lifetime of the component compared to the models of the prior art. Thus, the flight time of the component before it is stopped for repair or replacement purposes can be increased. In other variants or in addition, the manufacturing margin of the component can be reduced. The number of components available in a given time increases. Thus, the method can develop more efficient maintenance criteria, reduce maintenance costs and space out the maintenance operations of the affected components further apart.
[0052] Preliminary concept
[0053] The wear of the component corresponds to a change of the component related to long-term wear during the operation of the turbomachine. In particular, the wear can be a mechanical wear resulting from external forces, friction and / or stresses undergone by the component during the operation of the turbomachine.
[0054] Wear changes the geometry of the component, i.e. the outer surface of the component. For example, wear can appear in the form of one or more friction marks that locally indent the component and / or wear can appear in the form of irregularities of the outer surface.
[0055] Wear can be defined by a dimension of the wear. For example, wear can be defined by a wear depth, i.e. a dimension of the wear in a direction perpendicular to a plane tangent to the outer surface of the component at the wear. The component can have several wear regions with different wear depths, then the wear depth represents the maximum among the wear depths of the several wear regions of the component. In other variants or additionally, wear can be defined by a wear length and / or a wear width. Wear can thus be defined by any combination of wear dimensions in any direction combination.
[0056] The running time can represent the number of operating cycles performed by the turbomachine equipped with the component. The unit of time thus represents a turbomachine operating cycle. For example, an operating cycle can comprise a takeoff, a mission and a landing, and an operating cycle corresponds to a certain number of flight hours. In one variant, the running time can represent the number of flight hours performed by the turbomachine equipped with the component. The unit of time then represents one flight hour.
[0057] The lifetime DDV of the component corresponds to the time elapsed before failure of the component. The lifetime DDV thus represents the number of units of time, for example the number of turbomachine operating cycles, that the component can withstand before failure.
[0058] The failure of the component can be a physical failure of the component due to wear of excessive dimension, or can be a wear of dimension such that the component no longer functions, and the failure of the component results in a degradation that exceeds a certain performance threshold of the turbomachine.
[0059] The damage of the component is determined on the basis of the wear of the component, which depends on the running time, the damage representing the wear of the component.
[0060] The average damage of the component corresponds to the damage of the component per unit of time.
[0061] The cumulative damage of the component at time t corresponds to the damage of the component after t units of time. The cumulative damage of the component varies between the new component damage E_neuf and the failure damage E_rupt.
[0062] The new component damage E_neuf corresponds to the damage of a non-worn component, for example the damage of a component that has not yet undergone any operating cycle. The geometry of the non-worn component thus corresponds to the component geometry at delivery. The new component damage E_neuf is determined at the initial running time t_0 of the turbomachine, which can be equal to 0. Where applicable, the new component damage E_neuf can be equal to 0.
[0063] The failure damage E_rupt corresponds to the damage of the component at the time of a component failure. Thus, the failure damage E_rupt corresponds to the maximum damage of the component at the time of turbine failure time t_rupt, which is equal to the lifetime DDV of the component. Where applicable, the failure damage E_rupt of the component can be equal to 1.
[0064] The relationship representing the wear as a function of time
[0065] The relationship representing the wear as a function of time u(t) corresponds to the wear kinematics of the component. The relationship representing the wear as a function of time u(t) represents the development of the wear of the component over time, i.e. the development of the wear size over the turbine running time. Thus, the relationship representing the wear as a function of time u(t) links the size of the wear, typically the depth of the wear, to the number of unit time, in particular the number of turbine running cycles. Specifically, the longer the turbine equipped with the component is running, the greater the wear of the component.
[0066] In the following, the application will be described more particularly for the case where the relationship representing the wear of the component as a function of time u(t) is a relationship representing the wear depth as a function of time. However, this is not limiting, as the relationship representing the wear as a function of time u(t) can be a relationship representing any combination of wear sizes in any combination of directions, as specified above.
[0067] The relationship representing the wear of the component as a function of time u(t) can be determined on the basis of a database compiled, for example, from tests performed on the component and / or on the basis of a database compiled from data collected on a stock of components assembled in a turbine in operation. Where applicable, the relationship representing the wear of the component as a function of time u(t) can take into account the statistical dispersion of the wear.
[0068] Determining the average damage of the component as a function of time
[0069] As illustrated by way of non-limiting example in Figure 2 The step S1 of determining the average damage of the component as a function of time E_moy(t) can comprise a step S11, as illustrated by way of non-limiting example in
[0070] S12: determining the component geometry on the basis of the wear u defined in step S11, so as to determine a relationship geom(u) representing the component geometry as a function of the wear;
[0071] S13: determining, based on the component geometry determined in step S12, the stress applied to the component, so as to determine a relationship σ(u) representing the stress to be applied to the component as a function of the wear;
[0072] S14: determining, based on the stress applied to the component determined in step S13, the lifetime of the component at constant wear, so as to determine a relationship DDV(u) representing the lifetime of the component at constant wear as a function of the wear; and
[0073] S15: determining, based on the lifetime of the component at constant wear determined in step S14, the average damage of the component, for example, so as to determine a relationship E_moy(u) representing the average damage of the component as a function of the wear.
[0074] The steps S12 to S15 for determining the geometry of the component, the stress of the component, the lifetime of the component at constant wear and the average damage of the component are repeated for each of the defined wears u, so as to obtain the corresponding relationships as a function of the wear.
[0075] The defined wears u correspond to a grid with respect to the wear of the component. The defined number of wears u sets the fineness of the grid. Thus, the greater the number of defined wears u, the more the average damage determined for a large number of defined wears u, and thus the more precise the definition of the relationship E_moy(u) representing the average damage of the component as a function of the wear.
[0076] For example, the wears u defined in step Sll can correspond to several defined wear depths. For each of the following defined wear depths u: 0 millimeters, 0.2 millimeters, 0.5 millimeters, 0.8 millimeters and 1 millimeter, the average damage of the component can be determined.
[0077] The relationship geom(u) representing the geometry of the component as a function of the wear, determined by repeating step S12 for each defined wear u, characterizes the variation of the geometry of the component as a function of the wear.
[0078] In particular, the wear of the component modifies the geometry of the component, i.e. the outer surface of the component. For example, friction traces having more or less large dimensions appear. The greater the wear, the more the geometry of the component deviates from the geometry of the component as it left the factory. Thus, the defined wears u have a defined geometry of the component corresponding thereto.
[0079] The relationship σ(u) representing the stress applied to the component as a function of the wear, determined by repeating step S13 for each defined wear u, characterizes the variation of the stress applied to the component (i.e. the stress inside the component) as a function of the wear of the component.
[0080] In particular, the stresses applied to the component vary as a function of the component geometry, i.e. of the outer surface of the component, and therefore also as a function of the component wear. In particular, when the wear dimension increases, the stresses applied to the component increase. Therefore, a worn component is subjected to greater stresses than a new component.
[0081] For a defined wear u, and therefore for a defined component geometry, a set of stresses applied to the component is determined. The set of stresses applied to the component for a defined wear u can correspond to a stress field, and the set of stresses can be calculated by a finite element model modelling the component geometry.
[0082] The step S1 of determining the average damage E_moy(t) of the component as a function of time can also comprise a step of determining the stresses applied to the component as a function of wear.
[0083] For each defined wear u, the stresses applied to the component are determined on the basis of the pressure applied to the component, and, where applicable, the stresses applied to the component are determined as a function of the temperature of the internal component per unit of time. Therefore, a relationship can be determined expressing the stresses applied to the component as a function of wear.
[0084] The relationship DDV(u) determined in step S14 for each defined wear u expressing the life of the component at constant wear as a function of wear characterizes the variation of the life of the component at constant wear as a function of the wear of the component.
[0085] For a defined wear u, the life of the component at constant wear corresponds to the number of units of time that the component can perform while being subjected to the determined stresses corresponding to the defined wear u before the component failure occurs. In other words, for a defined wear u, the life of the component at constant wear corresponds to the number of units of time, in particular the number of operating cycles, before the component failure.
[0086] The life of the component at constant wear is evaluated for a defined wear u of the component, which is constant and does not develop over time. In other words, the evaluation of the life of the component at constant wear does not take into account the development of the component wear over the turbomachine operating time, and therefore the development of the component geometry over the turbomachine operating time, and therefore also the development of the stresses applied to the component over the turbomachine operating time.
[0087] For the defined wear u, the lifetime of the component at constant wear is evaluated on the basis of the thermomechanical stresses (stresses and temperatures) corresponding to the defined wear u. The lifetime of the component at constant wear can be determined on the basis of a propagation model of the wear and / or on the basis of a database, in particular a material testing database, which establishes a correspondence between the thermomechanical stresses applied to the component and the lifetime of the component at constant wear.
[0088] The relationship E_moy(u) representing the average damage of the component as a function of the wear, determined for each defined wear u, characterizes the development of the average damage of the part as a function of the wear.
[0089] For the defined wear u, the average damage of the component corresponds to the average damage of the component per unit of time, in particular the average damage of the component over the operating period of the turbomachine.
[0090] The average damage of the component is determined for a defined wear u which is constant and does not develop over time. In other words, the evaluation of the average damage of the component does not take into account the wear of the component over the operating time of the turbomachine and therefore does not take into account the geometry of the component over the operating time of the turbomachine, nor the stresses applied to the component over the operating time of the turbomachine, and therefore does not take into account the lifetime of the component over the operating time of the turbomachine.
[0091] For the defined wear u, the average damage of the component is determined on the basis of the lifetime at constant wear determined in step S13.
[0092] The relationship E_moy(u) representing the average damage of the component as a function of the wear has a variation direction opposite to that of the relationship DDV(u) representing the lifetime of the component at constant wear as a function of the wear. In other words, when the lifetime of the component at constant wear decreases, the average damage of the component per unit of time increases.
[0093] In an embodiment, the relationship E_moy(u) representing the average damage of the component as a function of the wear is equal to the inverse DDV(u) of the relationship representing the lifetime of the component at constant wear as a function of the wear. The average damage of the component per unit of time is considered to be constant, i.e. the damage of the component is the same for each operating period of the turbomachine. For the defined wear u, the cumulative damage E_cum of the component varies linearly with the operating time of the turbomachine, i.e. the cumulative damage E_cum of the component varies with the number of units of time.
[0094] In this embodiment, the accumulated new component damage E neuf is equal to 0 at the turbine operating time t 0 equal to 0. The accumulated damage of the component at the failure E rupt is equal to 1 at the turbine operating time t rupt equal to the lifetime of the component.
[0095] The relation expressing the average damage of the component as a function of the wear function is expressed in the following form:
[0096]
[0097] Thus, for a defined wear u, the average damage of the component corresponds to the inverse of the lifetime of the component at constant wear determined for the defined wear u, i.e. the inverse of the number of units of time before failure of the component. The average damage of the component is determined for each defined wear u.
[0098] The step S1 for determining the average damage of the component as a function of time can also comprise a step S16. Said step S16 comprises determining the average damage of the component as a function of time E moy(t) based on the relation E moy(u) expressing the average damage of the component as a function of wear and the relation u(t) expressing the wear as a function of time.
[0099] The step S16 for determining the average damage of the component as a function of time E moy(t) can comprise replacing the wear by the time in the expression E moy(u) of the average damage of the component as a function of wear based on the relation u(t) expressing the wear of the component as a function of time. Thus, said step S16 is similar to a change of variable, the wear variable being expressed as a function of the time variable. Thus, the relation u(t) expressing the wear of the component as a function of time makes it possible to express the average damage as a function of time E moy(t).
[0100] The average damage of the component as a function of time E moy(t) corresponds to the average damage of the component per unit of time, in particular per turbine operating cycle.
[0101] Figure 3 、 Figure 4 and Figure 5 A particular embodiment is shown. The time is expressed in number of turbine operating cycles.
[0102] Figure 3is a graph showing the relation DDV(u) representing the life of a given component at constant wear. The life of the component at constant wear is expressed in number of turbine operating cycles. The wear is characterized by a wear depth expressed in number of units of depth. The defined wears u respectively correspond to 0 unit of depth, 1 unit of depth, 2 units of depth and 3 units of depth. The life of the component at constant wear is evaluated repeatedly for each of the defined wears u under the assumption that the wear remains constant over the turbine operating time. As the wear of the component increases, the life of the component at constant wear decreases. Specifically, the more the component is worn, the more operating cycles it can undergo before reducing the failure of the component.
[0103] The relation DDV(u) representing the life at constant wear is shown by a decreasing convex curve. The life of the component at constant wear is 100000 cycles for a non-worn component, i.e. a component with a wear depth of 0 units. The life of the component at constant wear is 12500 cycles for a wear depth of 3 units.
[0104] Figure 4 is a graph showing the relation E_moy(u) representing the average damage per time unit of the component as a function of the wear depth in this example. For each defined wear u, the average damage per time unit of the component corresponds to the inverse of the life at constant wear obtained for the defined wear u under the assumption that the wear remains constant over the turbine operating time. The average damage of the component increases as the wear depth increases. Specifically, the more the component is worn, the more stress is applied on the component and therefore the more the average damage of the component.
[0105] The relation E_moy(u) representing the average damage of the component as a function of the wear corresponds to the inverse of the relation DDV(u) representing the life of the component at constant wear as a function of the wear and the relation E_moy(u) representing the average damage of the component as a function of the wear is an increasing convex curve. For a wear of 0 units of depth of the component, the average damage of the component per operating cycle is 10 -5 , which corresponds to a life of 100000 cycles at constant wear. For a wear of 3 units of depth of the component, the average damage of the component per operating cycle is 8*10 -5 , which corresponds to a life of 12500 cycles at constant wear.
[0106] Figure 5is a graph showing the relation E moy (t) representing the average damage of the component per unit time as a function of the running time. Based on the relation u(t) representing the wear against time, the average damage E moy (t) of the component per unit time is determined by replacing the wear in the expression E moy (u) of the average damage as a function of the wear by the time.
[0107] The relation u(t) representing the wear against the running time can be a linear relation, the wear increasing by one unit depth for 1000 turbine running cycles. As a variant, the relation u(t) representing the wear against the running time can be a non-linear relation.
[0108] The average damage of the component as a function of the time is an increasing convex function. For a zero working time t 0 (corresponding to a zero wear of the component), the average damage of the component per working cycle is 10 -5 . For a running time of 3000 cycles, the average damage of the component per working cycle is 8*10 -5 .
[0109] Determining the lifetime of the component
[0110] The cumulative damage of the component is determined at a time t, i.e. after t units of time, in particular after t running cycles. The cumulative damage of the component at the time t corresponds to the integral of the average damage as a function of the time between the initial time t 0 and the time t: Thus, after t units of turbine running time, the cumulative damage of the component represents the sum of the average damage of the component per unit time within these t units of time.
[0111] The lifetime DDV of the component corresponds to the turbine running time t rupt at which the component fails. In particular, the lifetime DDV of the component corresponds to the time elapsed between the initial turbine running cycle t 0 for a new component and the final turbine running cycle t rupt at which the component fails.
[0112] The failure of the component occurs when the cumulative damage of the component is equal to the damage E rupt at which the component fails. Thus, the lifetime DDV of the component corresponds to the time value t rupt for which the integral of the average damage of the component per unit time as a function of the time between the initial time t 0 and the failure time t rupt corresponds to the damage of the component at failure:
[0113] In an embodiment, the initial time t 0 is equal to 0 and corresponds to a new component damage E neuf equal to 0, the component not having undergone any running cycle and not having any damage at the initial time t 0. The damage at failure E rupt is equal to 1.
[0114] The number of operating cycles after which the accumulated damage of the component equals 1 corresponds to the lifetime DDV of the component, i.e. to the number of operating cycles before the failure t rupt of the component. The value of the failure time t rupt can be derived from the following equation: Thus, the value of the failure time t rupt can be derived from the relation E moy (t) expressing the average damage as a function of time, the value of the failure time t rupt being equal to the lifetime DDV of the component, i.e. t rupt = DDV.
[0115] For example, the method can be used to assess the lifetime DDV of a low-pressure compressor disc 10. In Figure 6a and 6b Such a low-pressure compressor disc 10 is shown by way of non-limiting example in Figs. 1 to 3. The low-pressure compressor disc 10 is rotationally fixed around a set of low-pressure compressor blades 20 extending radially from the disc along a turbine longitudinal axis. In particular, the low-pressure compressor blade roots 20 can be attached to the low-pressure compressor disc 10 at bolt couplings 40.
[0116] A damper 30 can be provided below the blade roots 20, close to the couplings 40 of the blades 20 on the compressor disc 10. The damper 30 can comprise a damping sheet. The damper 30 attenuates the vibrations of the elements in contact with it.
[0117] Due to the contact between the damper 30 and the disc 10 facing the respective blade 20, wear can be induced on the low-pressure compressor disc 10, in particular wear induced by a small number of strokes.
[0118] The more the number of operating cycles the low-pressure compressor disc 10 is subjected to, the more the wear increases. The geometry of the low-pressure compressor disc 10, i.e. its outer surface, is affected by the development of wear. The method described below is used to assess the lifetime DDV of the low-pressure compressor disc 10 taking into account the changes in the geometry of the component 10 due to the development of wear over time.
[0119] In variants, the method can be applied to assess the lifetime DDV of any turbine component for which wear develops over time and for which the stress develops with the development of wear.
Claims
1. A method for evaluating the DDV of a turbine component, comprising the following steps: S1: Based on the relationship (σ(u)) that expresses the stress applied to the component as a function of the wear of the component and the relationship (u(t)) that expresses the wear of the component as a function of time, determine the average damage (E_moy(t)) of the component as a function of time; S2: Determine the damage (E_rupt) to the component in the event of a failure; S3: Determine the cumulative damage (E_cum) of the component corresponding to the damage (E_rupt) of the component at the time of failure, the cumulative damage (E_cum) corresponding to the integral of the average damage (E_moy(t)) as a function of time between the initial time (t_0) and the final time (t_rupt): as well as S4: The lifetime (DDV) of the component is thus derived, which corresponds to the final time (t_rupt).
2. The method for evaluating the DDV of turbine components according to claim 1, wherein, Step S1, which determines the average damage (E_moy(t)) of the component as a function of time, includes step S11, which defines several different wears (u) of the component, and step S1 includes the following steps performed for each defined wear (u) of the component: S12: Based on the wear (u) defined in step S11, determine the component geometry in order to determine the relationship (geom(u)) that represents the component geometry as a function of wear; S13: Based on the component geometry determined in step S12, determine the stress applied to the component in order to determine the relationship (σ(u)) that expresses the stress applied to the component as a function of wear; S14: Based on the stress applied to the component determined in step S13, determine the component's lifespan under constant wear, in order to determine a relationship (DDV(u)) that expresses the component's lifespan under constant wear as a function of wear; and S15: Based on the lifespan of the component under constant wear determined in step S14, determine the average damage of the component in order to determine the relationship (E_moy(u)) that expresses the average damage of the component as a function of wear.
3. The method for evaluating the DDV of turbine components according to claim 2, wherein, Step S1, which determines the average damage (E_moy(t)) of the component as a function of time, further includes step S16, which includes: determining the average damage (E_moy(t)) of the component as a function of wear based on the relationship (E_moy(t)) that expresses the average damage of the component as a function of wear and the relationship (u(t)) that expresses wear as a function of time.
4. The method for evaluating the DDV of a turbine component according to claim 2 or 3, wherein, The relationship that expresses the average damage of the component as a function of wear (E_moy(u)) is equal to the reciprocal of the relationship that expresses the life of the component under constant wear as a function of wear (DDV(u)).
5. The method for evaluating the day-to-life (DDV) of a turbine component according to any one of claims 1 to 3, wherein, The method is implemented to evaluate the life (DDV) of the low-pressure compressor disk (10).
6. The method for evaluating the day-to-life (DDV) of a turbine component according to any one of claims 1 to 3, wherein, The relationship (u(t)) that expresses the wear of the component as a function of time is the same as the relationship that expresses the wear depth as a function of time.
7. The method for evaluating the day-to-life (DDV) of a turbine component according to any one of claims 1 to 3, wherein, The damage (E_rupt) of the component in the event of a failure is equal to 1.
Citation Information
Patent Citations
MECHANICAL PART RELIABILITY ASSESSMENT
FR3087241A1