Remaining life evaluation method for compressor impellers

Abstract

To provide a remaining lifetime evaluation method for a compressor impeller capable of accurately evaluating the remaining lifetime of the compressor impeller by effectively utilizing operation data relating to a supercharger.SOLUTION: The present invention relates to a remaining lifetime evaluation method for a compressor impeller for evaluating the remaining lifetime of the compressor impeller that a supercharger comprises. The remaining lifetime evaluation method includes: a rotation speed acquiring step of acquiring a rotation speed of the supercharger; a stress calculating step of calculating a stress generated in the compressor impeller from the rotation speed of the supercharger acquired in the rotation speed acquiring step; an outlet temperature acquiring step of acquiring an outlet temperature of the compressor impeller; a metal temperature calculating step of calculating a metal temperature of the compressor impeller from the outlet temperature of the compressor impeller acquired in the outlet temperature acquiring step; and a remaining lifetime evaluating step of evaluating the remaining lifetime of the compressor impeller from the stress calculated in the stress calculating step and the metal temperature calculated in the metal temperature calculating step by utilizing a previously acquired relationship of the stress, the metal temperature and the lifetime in the compressor impeller.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for evaluating the remaining life of a compressor impeller of a turbocharger. [Background technology]

[0002] Conventionally, the lifespan of a compressor impeller in a turbocharger has not been accurately known, and the compressor impeller has been replaced based on a predetermined replacement interval. Therefore, when the replacement interval has come, the compressor impeller has been replaced even if there is still some life left in the compressor impeller.

[0003] As described above, if the life of the compressor impeller cannot be accurately determined, the appropriate replacement time for the compressor impeller cannot be determined, which poses a problem that the compressor impeller cannot be used to its limit. In order to determine the appropriate replacement time for the compressor impeller, it is desirable to accurately evaluate the remaining life of the compressor impeller. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4589751 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, since the life of the compressor impeller cannot be accurately determined, there has been a problem in that the compressor impeller cannot be used to its limit.

[0006] Several methods for assessing the remaining life of a compressor impeller have been proposed, but none have been put to practical use. For example, Patent Document 1 discloses a turbocharger life determination device equipped with a creep monitoring algorithm that monitors compressor wheel creep. This creep monitoring algorithm monitors creep by monitoring the amount of time the device operates under different combinations of detected compressor inlet temperatures and calculated compressor pressure ratios. The combinations include a creep score that represents the stress on the compressor wheel caused by a specific combination. The product of the amount of time under a specific combination and the creep score is the creep stress damage caused by the specific combination, and the sum of the creep stress damage is the monitored creep.

[0007] In view of the above-described circumstances, an object of at least one embodiment of the present disclosure is to provide a method for assessing the remaining life of a compressor impeller that can accurately assess the remaining life of a compressor impeller by utilizing operational data related to a turbocharger. [Means for solving the problem]

[0008] A method for assessing the remaining life of a compressor impeller according to an embodiment of the present disclosure includes: A method for evaluating the remaining life of a compressor impeller of a turbocharger, comprising: a rotation speed acquisition step of acquiring a rotation speed of the supercharger; a stress calculation step of calculating stress generated in the compressor impeller from the rotation speed of the turbocharger acquired in the rotation speed acquisition step; an outlet temperature acquisition step of acquiring an outlet temperature of the compressor impeller; a metal temperature calculation step of calculating a metal temperature of the compressor impeller from the outlet temperature of the compressor impeller acquired in the outlet temperature acquisition step; and a remaining life evaluation step of evaluating the remaining life of the compressor impeller from the stress calculated in the stress calculation step and the metal temperature calculated in the metal temperature calculation step, by utilizing a relationship between the stress, metal temperature, and life of the compressor impeller that has been obtained in advance. [Effects of the Invention]

[0009] According to at least one embodiment of the present disclosure, a method for assessing the remaining life of a compressor impeller is provided that can accurately assess the remaining life of a compressor impeller by utilizing operational data related to a turbocharger. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating the configuration of an engine system equipped with a compressor impeller that is the subject of evaluation by a method for evaluating the remaining life of a compressor impeller according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a flow diagram of a method for assessing the remaining life of a compressor impeller according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is an explanatory diagram for explaining the relationship between stress in a compressor impeller and the Larson-Miller parameter. [Figure 4] FIG. 10 is a flow diagram of a remaining life assessment step according to an embodiment of the present disclosure. [Figure 5] FIG. 10 is a flow diagram of a remaining life assessment step according to an embodiment of the present disclosure. [Figure 6] FIG. 10 is an explanatory diagram for explaining a method for calculating a cumulative damage degree. [Figure 7] FIG. 10 is a flow diagram of a rotation speed acquisition step according to an embodiment of the present disclosure. [Figure 8] 1 is an explanatory diagram for explaining a method of correcting the remaining life of a compressor impeller, showing the transition of the remaining life with respect to the actual operating time of the compressor impeller. FIG. [Figure 9] FIG. 10 is a diagram showing the relationship (crystal grain size relationship information) between the crystal grain size of the material structure on the surface of the compressor impeller and the remaining life of the compressor impeller. [Figure 10] FIG. 4 is a diagram showing the relationship between the distortion of the compressor impeller and the remaining life of the compressor impeller (distortion relationship information). [Figure 11] 10 is a diagram showing the relationship between the hardness of a compressor impeller and the remaining life of the compressor impeller (hardness relationship information). FIG. [Figure 12] FIG. 10 is a diagram showing the relationship between the thickness of an oxide film formed on the surface of a compressor impeller and the remaining life of the compressor impeller (film thickness relationship information). [Figure 13] FIG. 10 is a diagram showing the relationship between the electrical resistance of a compressor impeller and the remaining life of the compressor impeller (electrical resistance relationship information). [Figure 14] FIG. 10 is a diagram showing the relationship between the size of an internal defect in a compressor wheel and the remaining life of the compressor wheel (internal defect size relationship information). DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," or "have" one element are not exclusive expressions that exclude the presence of other elements. Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

[0012] 1 is a schematic diagram illustrating the configuration of an engine system equipped with a compressor impeller that is the subject of an evaluation method for evaluating the remaining life of a compressor impeller according to an embodiment of the present disclosure. The method 1 for evaluating the remaining life of a compressor impeller according to some embodiments of the present disclosure is for evaluating the remaining life of a compressor impeller 4 of a turbocharger 3. The turbocharger 3 is installed in an engine system 2 that includes an engine 5 as shown in FIG. 1.

[0013] (Engine System) 1 , the engine system 2 includes an engine (engine main body) 5 configured to generate power by burning fuel therein, a combustion gas supply line 6 for compressing and supplying combustion gas (for example, air) to be used for combustion inside the engine 5, a turbocharger 3 having a compressor impeller 4 provided in the combustion gas supply line 6, and an economizer 7 provided on the combustion gas supply line 6 downstream of the compressor impeller 4. The economizer 7 is made of a heat exchanger configured to cool the combustion gas passing through the economizer 7.

[0014] 1, the engine system 2 further includes an exhaust gas discharge line 8 for guiding exhaust gas discharged from the engine 5, a fuel injection valve 9 configured to inject fuel into the engine 5, and a control device 11. The control device 11 is made up of an engine control unit for controlling the operation of each device in the engine system 2 (such as the engine 5 and the fuel injection valve 9).

[0015] The engine 5 includes at least one cylinder 51 and at least one piston 52 accommodated in the at least one cylinder 51 so as to be capable of reciprocating axially. The engine 5 has a combustion chamber 53 therein defined by the cylinder 51 and the piston 52. The combustion chamber 53 is connected to a combustion gas supply line 6 downstream of the intercooler 7 so as to allow gas to flow therethrough. The combustion gas supply line 6 is a flow path for guiding combustion gas from the compressor 32 to the combustion chamber 53. The combustion chamber 53 is connected to an exhaust gas discharge line 8 so as to allow gas to flow therethrough. The exhaust gas discharge line 8 is a flow path for circulating exhaust gas discharged from the combustion chamber 53 to the turbine 33.

[0016] The fuel injected from the fuel injection valve 9 into the combustion chamber 53 or the combustion gas supply line 6 is mixed with the combustion gas sent to the combustion chamber 53 through the combustion gas supply line 6, and then combusted in the combustion chamber 53. The exhaust gas after combustion in the combustion chamber 53 passes through the exhaust gas discharge line 8 and is discharged to the outside of the engine system 2.

[0017] (Turbocharger) In the illustrated embodiment, the turbocharger 3 includes a turbine 33 driven by the energy of exhaust gas (exhaust gas) discharged from the engine 5, a compressor 32 that compresses combustion gas (e.g., air) to be supplied to the engine 5, and a rotating shaft 31. The compressor 32 includes a compressor impeller 4 provided in the above-mentioned combustion gas supply line 6 and a compressor housing 34 that rotatably houses the compressor impeller 4. The compressor impeller 4 is mechanically connected to one side of the rotating shaft 31. The turbine 33 includes turbine blades 35 provided in the above-mentioned exhaust gas discharge line 8 and a turbine housing 36 that rotatably houses the turbine blades 35. The turbine blades 35 are mechanically connected to the other side of the rotating shaft 31.

[0018] The combustion gas that has passed through the compressor impeller 4 of the compressor 32 is introduced into the combustion chamber 53 of the engine 5 through a combustion gas supply line 6, and is used for combustion in the combustion chamber 53. The exhaust gas generated by the combustion in the combustion chamber 53 is introduced into the turbine blades 35 of the turbine 33 through an exhaust gas discharge line 8. The turbocharger 3 is configured to rotate the turbine blades 35 by the energy of the exhaust gas discharged from the engine 5. The compressor impeller 4 is mechanically connected to the turbine blades 35 via the rotating shaft 31, and therefore rotates in conjunction with the rotation of the turbine blades 35. The turbocharger 3 is configured to compress the combustion gas passing through the compressor impeller 4 by the rotation of the compressor impeller 4, increase the density of the combustion gas, and send it to the engine 5.

[0019] (Measuring equipment installed in engine systems) In the engine system 2, measurements are generally made of the inlet pressure Ps of the compressor impeller 4, the pressure Pd of the combustion gas (working fluid of the compressor impeller 4) downstream of the economizer 7 in the combustion gas supply line 6, the inlet temperature Ts of the compressor impeller 4, the temperature Td of the combustion gas (working fluid of the compressor impeller 4) downstream of the economizer 7 in the combustion gas supply line 6, and the rotation speed N of the turbocharger 3. Here, the inlet pressure Ps of the compressor impeller 4 is the pressure of the combustion gas (working fluid of the compressor impeller 4) upstream of the compressor impeller 4 in the combustion gas supply line 6. The inlet temperature Ts of the compressor impeller 4 is the temperature of the combustion gas (working fluid of the compressor impeller 4) upstream of the compressor impeller 4 in the combustion gas supply line 6.

[0020] As shown in FIG. 1 , the engine system 2 includes a first pressure measuring device (in the illustrated example, a pressure sensor) 21 configured to measure the inlet pressure Ps of the compressor impeller 4, a second pressure measuring device (in the illustrated example, a pressure sensor) 22 configured to measure the pressure Pd of the working fluid of the compressor impeller 4, a first temperature measuring device (in the illustrated example, a temperature sensor) 23 configured to measure the inlet temperature Ts of the compressor impeller 4, a second temperature measuring device (in the illustrated example, a temperature sensor) 24 configured to measure the temperature Td of the working fluid of the compressor impeller 4, and a first rotation speed measuring device (in the illustrated example, a rotation speed sensor) 25 configured to measure the rotation speed N of the turbocharger 3.

[0021] The above-mentioned control device 11 is configured to receive measurement results from each of the first pressure measuring device 21, the second pressure measuring device 22, the first temperature measuring device 23, the second temperature measuring device 24 and the first rotation speed measuring device 25.

[0022] (Method for assessing remaining life of compressor impellers) FIG. 2 is a flow diagram of a method for assessing the remaining life of a compressor impeller according to one embodiment of the present disclosure. As shown in Fig. 2, a method 1 for assessing remaining life of a compressor impeller according to some embodiments includes a rotation speed acquisition step S1, a stress calculation step S2, an outlet temperature acquisition step S3, a metal temperature calculation step S4, and a remaining life assessment step S5. In the illustrated embodiment, some steps in the remaining life assessment method 1 (such as the stress calculation step S2, the metal temperature calculation step S4, and the remaining life assessment step S5) are performed by a control device 11. In other words, the control device 11 is configured to be able to execute the stress calculation step S2, the metal temperature calculation step S4, and the remaining life assessment step S5, and is configured to perform these steps. Note that some steps in the remaining life assessment method 1 may be performed by a device or equipment other than the control device 11, or may be performed manually.

[0023] In one embodiment, a remaining life assessment device, which is a device different from the control device 11, is configured to be able to execute some steps (such as the stress calculation step S2, the metal temperature calculation step S4, and the remaining life assessment step S5) in the remaining life assessment method 1 in place of the control device 11, and performs the steps. Measurement data from the engine system 2 (measurement results from the first pressure measuring device 21, the second pressure measuring device 22, the first temperature measuring device 23, the second temperature measuring device 24, and the first rotation speed measuring device 25) are sent to the remaining life assessment device. The remaining life assessment device may be located in a remote location away from the control device 11. Specifically, when the engine system 2 including the control device 11 is installed on a ship, the remaining life assessment device may be located at the installation location of the control device 11 on the ship, or may be located at a location different from the installation location of the control device 11 on the ship. The remaining life assessment device may also be located in a facility on land away from the ship. According to the remaining life assessment device, the remaining life of the compressor impeller 4 can be assessed even in a remote location away from the engine system 2 including the control device 11.

[0024] In the rotation speed acquisition step S1, the rotation speed N of the turbocharger 3 is acquired. In the illustrated embodiment, in the rotation speed acquisition step S1, the measured value of the rotation speed of the turbocharger 3 measured by the first rotation speed measurement device 25 is acquired as the rotation speed N of the turbocharger 3.

[0025] In the stress calculation step S2, the stress (centrifugal stress) σ generated in the compressor impeller 4 is calculated from the rotation speed N of the turbocharger 3 acquired in the rotation speed acquisition step S1. Specifically, prior to the stress calculation step S2, first relationship information R1 indicating the relationship between the stress σ generated in the compressor impeller 4 and the rotation speed N of the turbocharger 3 is acquired. In the stress calculation step S2, the stress σ is calculated from the rotation speed N based on the first relationship information R1 acquired in advance.

[0026] The first relationship information R1 indicates a correspondence relationship between the stress σ generated in the compressor impeller 4 and the rotation speed N of the turbocharger 3, and may be any information that can acquire the stress σ corresponding to the rotation speed N as input information when the rotation speed N is input information. The first relationship information R1 includes a list, table, map, function, machine learning model, etc. that indicates the correspondence relationship between the input information and the output information. The first relationship information R1 may be created based on steady-state test data, or may be created based on past performance values, experimental values, numerical analysis results, etc. other than steady-state test data.

[0027] The stress σ generated in the compressor impeller 4 is proportional to the square of the rotation speed N of the turbocharger 3. Therefore, the stress σ increases as the rotation speed N increases. From the above, it can be said that there is a correlation between the stress σ and the rotation speed N. The first relationship information R1 includes the above correlation between the stress σ and the rotation speed N.

[0028] In the outlet temperature acquisition step S3, an outlet temperature Te of the compressor impeller 4 is acquired. The outlet temperature Te of the compressor impeller 4 is the temperature of the combustion gas (working fluid of the compressor impeller 4) on the downstream side of the compressor impeller 4 and upstream side of the economizer 7 in the combustion gas supply line 6. Since the combustion gas is cooled by the economizer 7, the temperature Td of the combustion gas downstream of the economizer 7 is lower than the outlet temperature Te of the compressor impeller 4.

[0029] In the illustrated embodiment, in the outlet temperature acquisition step S3, the temperature Td measured by the second temperature measurement device 24 plus the temperature drop ΔT caused by the intercooler 7 is added to acquire the outlet temperature Te. The temperature drop ΔT is set in advance based on the specifications of the intercooler 7 before the outlet temperature acquisition step S3.

[0030] In metal temperature calculation step S4, a metal temperature Tm of the compressor impeller 4 is calculated from the outlet temperature Te of the compressor impeller 4 acquired in outlet temperature acquisition step S3. Specifically, prior to metal temperature calculation step S4, second relationship information R2 indicating the relationship between the outlet temperature Te and the metal temperature Tm is acquired. In metal temperature calculation step S4, the metal temperature Tm is calculated from the outlet temperature Te based on the second relationship information R2 acquired in advance.

[0031] The second relationship information R2 indicates the correspondence relationship between the outlet temperature Te of the compressor impeller 4 and the metal temperature Tm of the compressor impeller 4, and may be any information that, when the outlet temperature Te is input information, enables the metal temperature Tm corresponding to the input information, outlet temperature Te, to be acquired as output information. The second relationship information R2 includes a list, table, map, function, machine learning model, or the like, that indicates the correspondence relationship between the input information and the output information. The second relationship information R2 may be created based on steady-state test data, or may be created based on past actual values, experimental values, numerical analysis results, or the like other than steady-state test data.

[0032] When the combustion gas is compressed by the compressor impeller 4, the outlet temperature Te of the compressor impeller 4 rises due to the temperature rise that accompanies the compression of the combustion gas. In addition, the metal temperature Tm of the compressor impeller 4 rises due to heat input from the compressed combustion gas. Therefore, the higher the outlet temperature Te, the higher the metal temperature Tm. From the above, it can be said that there is a correlation between the outlet temperature Te and the metal temperature Tm. The second relationship information R2 includes the above correlation between the outlet temperature Te and the metal temperature Tm.

[0033] In remaining life evaluation step S5, the relationship between the stress σ, metal temperature Tm, and lifespan of the compressor impeller 4 that has been acquired in advance is used to evaluate the remaining lifespan of the compressor impeller 4 from the stress σ calculated in stress calculation step S2 and the metal temperature Tm calculated in metal temperature calculation step S4.

[0034] Damage (such as creep damage) occurs and progresses in the compressor impeller 4 according to the history up to the present of the stress σ and metal temperature Tm in the compressor impeller 4. According to compressor impeller remaining life evaluation method 1, by utilizing the relationship between the stress σ, metal temperature Tm, and life of the compressor impeller 4 in remaining life evaluation step S5, it is possible to calculate the remaining life taking into account the damage to the compressor impeller 4 up to the present from the stress σ calculated in stress calculation step S2 and the metal temperature Tm calculated in metal temperature calculation step S4, and therefore the remaining life of the compressor impeller 4 can be evaluated with high accuracy.

[0035] (Permissible operating time of compressor impeller) 2 , the remaining life assessment step S5 includes a Larson-Miller parameter calculation step S51 for calculating the Larson-Miller parameter LMP from the stress σ calculated in the stress calculation step S2 by using the previously acquired relationship (third relationship information R3) between the stress σ in the compressor impeller 4 and the Larson-Miller parameter LMP, and an allowable operating time calculation step S52 for calculating the allowable operating time tr of the compressor impeller 4 from the Larson-Miller parameter LMP calculated in the Larson-Miller parameter calculation step S51 and the metal temperature Tm calculated in the metal temperature calculation step S4. The allowable operating time tr of the compressor impeller 4 indicates the time until the compressor impeller 4 breaks when it is subjected to a constant stress σ at a constant metal temperature Tm.

[0036] Prior to the Larson-Miller parameter calculation step S51, third relationship information R3 is acquired. The third relationship information R3 indicates the correspondence between the stress σ in the compressor impeller 4 and the Larson-Miller parameter LMP. When the stress σ is input information, the Larson-Miller parameter LMP corresponding to the input information, the stress σ, can be acquired as output information. The third relationship information R3 includes a list, table, map, function, machine learning model, or the like indicating the correspondence between the input information and the output information. The third relationship information R3 may be created based on steady-state test data, or may be created based on past performance values, experimental values, numerical analysis results, or the like other than steady-state test data.

[0037] FIG. 3 is an explanatory diagram illustrating the relationship between stress in a compressor impeller and the Larson-Miller parameter. FIG. 3 shows a graph with the stress σ in the compressor impeller 4 on the vertical axis and the Larson-Miller parameter LMP on the horizontal axis. FIG. 3 also shows a master curve M1 that indicates the relationship between the stress σ and the Larson-Miller parameter LMP. The master curve M1 is obtained, for example, from the results of creep rupture tests at several levels of stress σ and metal temperature Tm. The third relationship information R3 includes the master curve M1. In one embodiment, in the Larson-Miller parameter calculation step S51, the Larson-Miller parameter LMP corresponding to the stress σ calculated in the stress calculation step S2 is calculated based on the master curve M1.

[0038] In the allowable operating time calculation step S52, the allowable operating time tr of the compressor impeller 4 is calculated based on the Larson-Miller parameter LMP calculated in the Larson-Miller parameter calculation step S51 and the metal temperature Tm calculated in the metal temperature calculation step S4, based on the following equation (1). LMP=Tm×(C+log(tr))······(1) Here, LMP is the Larson-Miller parameter, Tm is the metal temperature of the compressor impeller 4, C is a material constant, and tr is the allowable operating time of the compressor impeller 4. In this embodiment, the material constant C=20.

[0039] According to the above method, by using the Larson-Miller parameter LMP, it is possible to calculate the permissible operating time tr of the compressor impeller 4, taking into account the creep damage to the compressor impeller 4 up to the present time, from the stress σ calculated in the stress calculation step S2 and the metal temperature Tm calculated in the metal temperature calculation step S4. The permissible operating time tr of the compressor impeller 4 calculated in the remaining life evaluation step S5 (S51 and S52) allows the remaining life of the compressor impeller 4 to be evaluated with high accuracy.

[0040] In some of the above-described embodiments, the Larson-Miller parameter LMP is used to determine the allowable operating time tr of the compressor impeller 4 from the stress σ and the metal temperature Tm, but the allowable operating time tr of the compressor impeller 4 may also be determined from the stress σ and the metal temperature Tm using other known extrapolation methods.

[0041] (Damage to compressor impeller) FIG. 4 is a flow diagram of a remaining life assessment step according to one embodiment of the present disclosure. 4, the remaining life assessment step S5 includes the Larson-Miller parameter calculation step S51, the allowable operating time calculation step S52, and the damage calculation step S53. In the damage calculation step S53, the actual operating time ta of the compressor impeller 4 is divided by the allowable operating time tr of the compressor impeller 4 calculated in the allowable operating time calculation step S52 to calculate the damage degree D of the compressor impeller 4.

[0042] As shown in FIG. 4, in the remaining life evaluation step S5 described above, the compressor impeller 4 is evaluated using the damage level D of the compressor impeller 4 calculated in the damage level calculation step S53 (compressor impeller evaluation step S54).

[0043] According to the above method, in damage degree calculation step S53, the damage degree D of the compressor impeller 4 can be calculated from the actual operation time ta of the compressor impeller 4 and the allowable operation time tr of the compressor impeller 4. The damage degree D of the compressor impeller 4 calculated in damage degree calculation step S53 makes it possible to grasp the degree of damage to the compressor impeller 4, and therefore the remaining life of the compressor impeller 4 can be evaluated with high accuracy.

[0044] (Cumulative damage to compressor impeller) FIG. 5 is a flow diagram of a remaining life assessment step according to one embodiment of the present disclosure. In some embodiments, as shown in FIG. 5, the remaining life assessment step S5 includes the Larson-Miller parameter calculation step S51, the allowable operating time calculation step S52, the differential damage calculation step S55, and the cumulative damage calculation step S56.

[0045] In the classified damage degree calculation step S55, for each unit period, the actual operation time ta of the compressor impeller 4 in the unit period is divided by the allowable operation time tr of the compressor impeller 4 calculated in the allowable operation time calculation step S52 to calculate a classified damage degree Di, which is the damage degree for each unit period of the compressor impeller 4. In the accumulated damage degree calculation step S56, a cumulative damage degree Dc, which is the sum of the classified damage degrees Di up to the present, is calculated.

[0046] FIG. 6 is an explanatory diagram for explaining a method for calculating the cumulative damage degree. FIG. 6 shows a graph in which the horizontal axis represents the time t from the start of operation t0 of the compressor impeller 4 and the vertical axis represents the cumulative damage degree Dc. It is assumed that the compressor impeller 4 will break when the cumulative damage degree Dc reaches 1, and the period from the start of operation t0 until the cumulative damage degree Dc reaches 1 is defined as the total lifespan L of the compressor impeller 4. In the classified damage degree calculation step S55, as shown in FIG. 6, classified damage degrees Di (i is a natural number equal to or greater than 1, D1, D2, D3 in the figure) are calculated for each unit period ti (i is a natural number equal to or greater than 1, t1, t2, t3 in the figure). The cumulative damage degree Dc calculated in the cumulative damage degree calculation step S56 is the sum of the classified damage degrees Di up to the present, i.e., up until the cumulative damage degree Dc is calculated, and is calculated using the following equation (2): Dc = ΣDi (i is a natural number greater than or equal to 2) (2)

[0047] 5, in the remaining life evaluation step S5 described above, the compressor impeller 4 is evaluated using the cumulative damage degree Dc of the compressor impeller 4 calculated in the cumulative damage degree calculation step S56 (compressor impeller evaluation step S57). Specifically, the difference between the cumulative damage degree Dc up to now and 1 is calculated, and the remaining life of the compressor impeller 4 for each future load pattern of the compressor impeller 4 can be calculated from this difference. Alternatively, the cumulative damage degree Dc may be directly used to evaluate the remaining life of the compressor impeller 4. In other words, the compressor impeller 4 may be replaced when the cumulative damage degree Dc reaches 1.

[0048] According to the above method, the cumulative damage level Dc can be calculated in the remaining life assessment step S5 (S55, S56). The cumulative damage level Dc of the compressor impeller 4 calculated in the remaining life assessment step S5 makes it possible to grasp the current degree of damage to the compressor impeller 4, and therefore the remaining life of the compressor impeller 4 can be assessed with high accuracy.

[0049] In some embodiments, as shown in FIG. 2 , in the above-described outlet temperature acquisition step S3, the temperature drop ΔT caused by the economizer 7 is added to the temperature Td of the working fluid in the compressor impeller 4 measured downstream of the economizer 7, and the result is acquired as the outlet temperature Te.

[0050] According to the above method, in the outlet temperature acquisition step S3, the outlet temperature Te of the compressor impeller 4 can be accurately estimated by adding the temperature drop ΔT caused by the economizer 7 to the temperature Td of the working fluid of the compressor impeller 4 downstream of the economizer 7. This makes it possible to accurately evaluate the remaining life of the compressor impeller 4 in the remaining life assessment step S5. Furthermore, according to the above method, the outlet temperature Te of the compressor impeller 4 can be acquired using the temperature Td of the working fluid of the compressor impeller 4 downstream of the economizer 7, which is generally measured in the engine system 2 including the turbocharger 3. According to the above method, even if the engine system 2 is not provided with a temperature measuring device that measures the outlet temperature Te of the compressor impeller 4, it is possible to execute the remaining life assessment method 1 of the compressor impeller 4. Note that the estimation of the outlet temperature Te of the compressor impeller 4 in the outlet temperature acquisition step S3 may be performed by the control device 11 or the remaining life assessment device described above.

[0051] In some other embodiments, in the above-mentioned outlet temperature acquisition step S3, the outlet temperature Te of the compressor impeller 4 is estimated from the inlet temperature Ts of the compressor impeller 4 measured by the first temperature measuring device 23 based on relationship information (e.g., a performance index of the compressor 32) indicating the relationship between the inlet temperature Ts and the outlet temperature Te of the compressor impeller 4.

[0052] (Turbocharger rotation speed) FIG. 7 is a flow diagram of a rotation speed acquisition step according to an embodiment of the present disclosure. When the engine system 2 described above does not include the first rotation speed measurement device 25 configured to measure the rotation speed N of the turbocharger 3, it is necessary to determine the rotation speed N of the turbocharger 3. In some embodiments, as shown in Fig. 7, the rotation speed acquisition step S1 described above includes a pressure ratio acquisition step S11, a flow rate acquisition step S12, and a rotation speed calculation step S13.

[0053] In the pressure ratio acquisition step S11, the pressure ratio Pr of the compressor impeller 4 is acquired. In the illustrated embodiment, the pressure ratio acquisition step S11 includes an inlet pressure measurement step S14 of measuring the inlet pressure Ps of the compressor impeller 4, an outlet pressure acquisition step S15 of acquiring the outlet pressure Pe of the compressor impeller 4, and a pressure ratio calculation step S16 of calculating the pressure ratio Pr of the compressor impeller 4 from the inlet pressure Ps of the compressor impeller 4 measured in the inlet pressure measurement step S14 and the outlet pressure Pe of the compressor impeller 4 acquired in the outlet pressure acquisition step S15.

[0054] In the flow rate acquisition step S12, the flow rate Fr of the compressor impeller 4 is acquired. In the flow rate acquisition step S12, the flow rate Fr of the compressor impeller 4 is estimated by a known method using the engine specifications and parameters that are generally measured in the engine system 2.

[0055] In the rotation speed calculation step S13, the relationship between the pressure ratio Pr of the compressor impeller 4, the flow rate Fr, and the rotation speed N of the turbocharger 3 that has been acquired in advance (fourth relationship information R4) is used to calculate the rotation speed N of the turbocharger 3 from the pressure ratio Pr acquired in the pressure ratio acquisition step S11 and the flow rate Fr acquired in the flow rate acquisition step S12.

[0056] Prior to the rotation speed calculation step S13, fourth relationship information R4 is acquired. The fourth relationship information R4 indicates a correspondence relationship between the pressure ratio Pr and flow rate Fr of the compressor impeller 4 and the rotation speed N of the turbocharger 3, and may be any information that can acquire the rotation speed N corresponding to the input information, that is, the pressure ratio Pr and the flow rate Fr, as output information when the pressure ratio Pr and the flow rate Fr are input information. The fourth relationship information R4 includes a list, a table, a map, a function, a machine learning model, or the like, that indicates the correspondence relationship between the input information and the output information. The fourth relationship information R4 may be created based on steady-state test data, or may be created based on past actual values, experimental values, numerical analysis results, or the like other than steady-state test data.

[0057] According to the above method, by utilizing the relationship between the pressure ratio Pr and flow rate Fr of the compressor impeller 4 and the rotation speed N of the turbocharger 3, it is possible to calculate the rotation speed N of the turbocharger 3 from the pressure ratio Pr acquired in the pressure ratio acquisition step S11 and the flow rate Fr acquired in the flow rate acquisition step S12. According to the above method, even if the engine system 2 is not provided with a rotation speed measuring device that measures the rotation speed N of the turbocharger 3, it becomes possible to execute the remaining life evaluation method 1 for the compressor impeller 4.

[0058] In some embodiments, as shown in FIG. 7, the pressure ratio acquisition step S11 described above includes the inlet pressure measurement step S14 described above, the outlet pressure acquisition step S15 described above, and the pressure ratio calculation step S16 described above.

[0059] According to the above method, the pressure ratio Pr of the compressor impeller 4 can be calculated from the inlet pressure Ps of the compressor impeller 4 measured in the inlet pressure measuring step S14 and the outlet pressure Pe of the compressor impeller 4 acquired in the outlet pressure acquiring step S15. According to the above method, even if the engine system 2 is not provided with a pressure ratio measuring device that measures the pressure ratio Pr of the compressor impeller 4, the remaining life evaluation method 1 of the compressor impeller 4 can be performed.

[0060] 7 , the rotation speed acquisition step S1 described above includes a pressure ratio acquisition step S11, a flow rate acquisition step S12, and a rotation speed calculation step S13, and the pressure ratio acquisition step S11 described above includes the inlet pressure measurement step S14, the outlet pressure acquisition step S15, and the pressure ratio calculation step S16. In the outlet pressure acquisition step S15 described above, the pressure Pd of the working fluid in the compressor impeller 4 measured downstream of the economizer 7 plus the pressure loss ΔP caused by the economizer 7 is acquired as the outlet pressure Pe.

[0061] In outlet pressure acquisition step S15, the outlet pressure Pe of the compressor impeller 4 is acquired. The outlet pressure Pe of the compressor impeller 4 is the pressure of the combustion gas (working fluid of the compressor impeller 4) on the combustion gas supply line 6 downstream of the compressor impeller 4 and upstream of the economizer 7. Due to the pressure loss ΔP in the economizer 7, the pressure Pd of the combustion gas downstream of the economizer 7 is lower than the outlet pressure Pe of the compressor impeller 4.

[0062] In the illustrated embodiment, in outlet pressure obtaining step S15, the pressure Pd measured by the second pressure measuring device 22 plus the pressure loss ΔP caused by the intercooler 7 is obtained as the outlet pressure Pe. The pressure loss ΔP is set in advance based on the specifications of the intercooler 7 before the outlet pressure obtaining step S15.

[0063] According to the above method, in outlet pressure acquisition step S15, the outlet pressure Pe of the compressor impeller 4 can be accurately estimated by adding the pressure loss ΔP caused by the economizer 7 to the pressure Pd of the working fluid of the compressor impeller 4 downstream of the economizer 7. This makes it possible to accurately estimate the pressure ratio Pr of the compressor impeller 4 in pressure ratio calculation step S16. Furthermore, according to the above method, the pressure ratio Pr of the compressor impeller 4 can be estimated using the pressure Pd of the working fluid of the compressor impeller 4 downstream of the economizer 7 and the inlet pressure Ps of the compressor impeller 4, which are generally measured in the engine system 2 including the turbocharger 3. According to the above method, even if the engine system 2 is not provided with a pressure measuring device that measures the outlet pressure Pe of the compressor impeller 4 or a pressure ratio measuring device that measures the pressure ratio Pr of the compressor impeller 4, the remaining life evaluation method 1 of the compressor impeller 4 can be performed. The estimation of the outlet pressure Pe in the pressure ratio acquisition step S11, the pressure ratio calculation step S16, the flow rate acquisition step S12, and the rotation speed calculation step S13 may be performed by the control device 11 or the remaining life evaluation device described above.

[0064] (Remaining life correction) 8, at least one parameter Qi of the compressor impeller 4 may be measured during regular inspection of the turbocharger 3, and the measured at least one parameter Qi of the compressor impeller 4 may be used to correct the evaluation result of the remaining life of the compressor impeller 4 in the remaining life evaluation step S5 described above. Here, the at least one parameter Qi used to correct the remaining life will be described in detail later, and may include at least one of a parameter acquired from a replica of the compressor impeller 4, distortion of the compressor impeller 4, hardness of the compressor impeller 4, thickness of an oxide film formed on the surface of the compressor impeller 4, electrical resistance of the compressor impeller 4, and size of an internal defect in the compressor impeller 4.

[0065] In the example shown in FIG. 8, the horizontal axis represents the actual operating time of the compressor impeller 4 since its start of operation (the cumulative operating time of the compressor impeller 4 since it was new), and the vertical axis represents the remaining life of the compressor impeller 4.

[0066] 8, the reference value (initial value) of at least one parameter Qi is measured before the compressor impeller 4 starts operating (when the compressor impeller 4 is brand new). However, depending on the type of parameter Qi, measuring this reference value is not essential.

[0067] During the period E1 from the start of operation of the compressor impeller 4 to the first regular inspection of the turbocharger 3, the remaining life of the compressor impeller 4 calculated in the remaining life evaluation step S5 (the remaining life calculated using the history of the stress σ and metal temperature Tm in the compressor impeller 4) is evaluated as the remaining life of the compressor impeller 4 as is.

[0068] Then, in the first periodic inspection, the casing of the turbocharger 3 is opened and the at least one parameter Qi of the compressor impeller 4 is measured.

[0069] During a period E2 from the first regular inspection to the second regular inspection of the turbocharger 3, the evaluation result of the remaining life of the compressor impeller 4 in the remaining life evaluation step S5 (the remaining life calculated using the history of the stress σ and the metal temperature Tm in the compressor impeller 4) is corrected using the at least one parameter Qi measured during the first regular inspection. For example, a change in the at least one parameter Qi during the period E1 may be calculated from a reference value of the at least one parameter Qi measured before the compressor impeller 4 starts operating and the at least one parameter Qi measured during the first regular inspection, and the evaluation result of the remaining life of the compressor impeller 4 in the remaining life evaluation step S5 may be corrected based on the calculated change in the at least one parameter Qi during the period E1.

[0070] Furthermore, for example, the remaining life of the compressor impeller 4 calculated using at least one of the parameters Qi measured in the first regular inspection (for example, the remaining life of the compressor impeller 4 calculated based on the change in the at least one parameter Qi in the period E1) may be used as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 in the period from the first regular inspection to the second regular inspection (the remaining life of the compressor impeller 4 at the time of the first regular inspection).

[0071] In this way, during the period from the nth (n is an integer equal to or greater than 1) regular inspection of the turbocharger 3 to the (n+1)th regular inspection, the evaluation result of the remaining life of the compressor impeller 4 (the remaining life calculated using the history of the stress σ and the metal temperature Tm in the compressor impeller 4) in the above-mentioned remaining life evaluation step S5 may be corrected using at least one parameter Qi measured in the nth regular inspection. In this case, during the period from the nth regular inspection to the (n+1)th regular inspection of the turbocharger 3, a change in the parameter Qi from before the start of operation of the compressor impeller 4 to the nth regular inspection may be calculated from a reference value of the parameter Qi measured before the start of operation of the compressor impeller 4 and the parameter Qi measured in the nth regular inspection, and the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 may be corrected based on the calculated change in the parameter Qi.

[0072] The correction of the remaining life here may be a correction in which the remaining life of the compressor impeller 4 calculated using at least one parameter Qi measured in the nth periodic inspection is set as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th periodic inspection. The correction of the remaining life here may be, for example, a correction of the permissible operating time tr calculated in S52 shown in Fig. 2, 4 or 5, a correction of the damage degree D calculated in S53 shown in Fig. 4, or a correction of the cumulative damage degree Dc calculated in S56 shown in Fig. 5.

[0073] In the example shown in FIG. 8, the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 is corrected to be extended (corrected by changing the solid line in the figure to a dashed dotted line) based on the measurement results of at least one of the parameters Qi measured in the first regular inspection during the period E2, and is corrected to be shortened (corrected by changing the dashed dotted line in the figure to a dashed two-dotted line) based on the measurement results of at least one of the parameters Qi measured in the second regular inspection during the period from the second regular inspection to the third regular inspection.

[0074] As described above, the remaining life depending on the history of the stress σ and the metal temperature Tm in the compressor impeller 4 is evaluated in the remaining life evaluation step S5, and the evaluation result is corrected using at least one parameter Qi of the compressor impeller 4 measured in the periodic inspection of the turbocharger 3, thereby improving the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to further extend the replacement interval of the compressor impeller 4.

[0075] Next, specific examples of the at least one parameter Qi measured in periodic inspection and some examples of methods for correcting the remaining life of the compressor impeller 4 using the parameter Qi will be described.

[0076] In some embodiments, the at least one parameter Qi used to correct the remaining life of the compressor impeller 4 may include a parameter acquired from a replica taken from the surface of the compressor impeller 4 during periodic inspection of the turbocharger 3. In this case, for example, a replica of the material structure of the surface of the compressor impeller 4 may be taken by a replica method, and the evaluation result of the remaining life of the compressor impeller 4 in the remaining life evaluation step S5 described above may be corrected based on the remaining life of the compressor impeller 4 evaluated based on changes in the structure (for example, changes in crystal grains, changes in micro defects (cracks) on the surface, or a history of breakage and regeneration of an oxide film).

[0077] For example, the at least one parameter Qi may include the grain size Q1 (average grain size) of crystal grains contained in the material structure of the surface of the compressor impeller 4. In this case, grain size relationship information R5 (see FIG. 9 ) indicating the relationship between the grain size of the material structure of the surface of the compressor impeller 4 and the remaining life of the compressor impeller 4 is obtained in advance by testing or the like, and the remaining life of the compressor impeller 4 is evaluated based on the grain size relationship information R5 and the grain size Q1 of the material structure of the surface of the compressor impeller 4 measured during periodic inspection of the turbocharger 3. Then, based on the evaluation result, the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 is corrected.

[0078] In this case, for example, the remaining life of the compressor impeller 4 evaluated based on the crystal grain size Q1 of the material structure of the surface of the compressor impeller 4 measured in the nth regular inspection and the crystal grain size relationship information R5 may be used as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th inspection. Note that the relationship between the crystal grain size of the material structure of the surface of the compressor impeller 4 and the remaining life of the compressor impeller 4 illustrated in Fig. 9 indicates that the larger the crystal grain size of the material structure of the surface of the compressor impeller 4, the shorter the remaining life of the compressor impeller 4 (the crystal grain size of the material structure of the surface of the compressor impeller 4 becomes as time passes).

[0079] In this way, by correcting the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 (the remaining life depending on the history of the stress σ and the metal temperature Tm in the compressor impeller 4) using the parameters acquired from the replica of the compressor impeller 4 during the periodic inspection of the turbocharger 3, it is possible to improve the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to further extend the replacement interval of the compressor impeller 4.

[0080] In some embodiments, the at least one parameter Qi used to correct the remaining life of the compressor impeller 4 may include the strain Q2 (deformation amount) of the compressor impeller 4. The strain is a value indicating how much a material point in an object is displaced per unit length from the reference state (initial state) of the object.

[0081] In this case, strain relationship information R6 (see FIG. 10) indicating the relationship between the strain of the compressor impeller 4 and the remaining life of the compressor impeller 4 is obtained in advance by testing or the like, and the remaining life of the compressor impeller 4 is evaluated based on the strain relationship information R6 and the strain Q2 of the compressor impeller 4 measured during periodic inspection of the turbocharger 3. Then, based on the evaluation result, the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 is corrected.

[0082] In this case, for example, the remaining life of the compressor impeller 4 evaluated based on the strain Q2 of the compressor impeller 4 measured in the nth regular inspection and the strain relationship information R6 may be set as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th inspection. Note that the relationship between the strain of the compressor impeller 4 and the remaining life of the compressor impeller 4 illustrated in Fig. 10 indicates that the remaining life of the compressor impeller 4 becomes shorter as the strain of the compressor impeller 4 increases (the strain of the compressor impeller 4 increases as time passes).

[0083] In this way, by correcting the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 (the remaining life according to the history of the stress σ and the metal temperature Tm in the compressor impeller 4) using the strain of the compressor impeller 4 measured in the periodic inspection of the turbocharger 3, it is possible to improve the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to extend the replacement interval of the compressor impeller 4.

[0084] In some embodiments, the at least one parameter Qi used to correct the remaining life of the compressor impeller 4 may include the hardness Q3 of the compressor impeller 4. In this case, hardness relationship information R7 (see FIG. 11 ) indicating the relationship between the hardness of the compressor impeller 4 and the remaining life of the compressor impeller 4 is obtained in advance by testing or the like, and the remaining life of the compressor impeller 4 is evaluated based on the hardness relationship information R7 and the hardness Q3 of the compressor impeller 4 measured during periodic inspection of the turbocharger 3. Then, based on the evaluation result, the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 is corrected.

[0085] In this case, for example, the remaining life of the compressor impeller 4 evaluated based on the hardness Q3 of the compressor impeller 4 measured in the nth regular inspection and the hardness relationship information R7 may be used as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th inspection. Note that the relationship between the hardness of the compressor impeller 4 and the remaining life of the compressor impeller 4 illustrated in Fig. 11 indicates that the lower the hardness of the compressor impeller 4, the shorter the remaining life of the compressor impeller 4 (the hardness of the compressor impeller 4 decreases as time passes).

[0086] In this way, by correcting the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 (the remaining life depending on the history of the stress σ and the metal temperature Tm in the compressor impeller 4) using the hardness of the compressor impeller 4 measured in the periodic inspection of the turbocharger 3, it is possible to improve the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to extend the replacement interval of the compressor impeller 4.

[0087] In some embodiments, the at least one parameter Qi used to correct the remaining life of the compressor impeller 4 may include a thickness Q4 of an oxide film formed on the surface of the compressor impeller 4. In this case, coating thickness relationship information R8 (see FIG. 12 ) indicating the relationship between the thickness of the oxide film formed on the surface of the compressor impeller 4 and the remaining life of the compressor impeller 4 is obtained in advance by testing or the like, and the remaining life of the compressor impeller 4 is evaluated based on the coating thickness relationship information R8 and the thickness Q4 of the oxide film measured during periodic inspection of the turbocharger 3. Then, based on the evaluation result, the remaining life of the compressor impeller 4 evaluated in the above-mentioned remaining life evaluation step S5 is corrected.

[0088] In this case, for example, the remaining life of the compressor impeller 4 evaluated based on the thickness Q4 of the oxide film measured in the nth periodic inspection and the coating thickness relationship information R8 may be used as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th inspection. Note that the relationship between the thickness of the oxide film formed on the surface of the compressor impeller 4 and the remaining life of the compressor impeller 4 illustrated in FIG. 12 indicates that the smaller the thickness of the oxide film, the shorter the remaining life of the compressor impeller 4 (the oxide film thickness decreases with the passage of time). Furthermore, the thickness Q4 of the oxide film formed on the surface of the compressor impeller 4 may be measured by a non-destructive test such as ultrasonic testing (UT).

[0089] In this way, by correcting the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 (the remaining life depending on the history of the stress σ and the metal temperature Tm in the compressor impeller 4) using the thickness Q4 of the oxide film measured in the periodic inspection of the turbocharger 3, it is possible to improve the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to extend the replacement interval of the compressor impeller 4.

[0090] In some embodiments, the at least one parameter Qi used to correct the remaining life of the compressor impeller 4 may include the electrical resistance Q5 of the compressor impeller 4. In this case, electrical resistance relationship information R9 (see FIG. 13 ) indicating the relationship between the electrical resistance of the compressor impeller 4 and the remaining life of the compressor impeller 4 is obtained in advance by testing or the like, and the remaining life of the compressor impeller 4 is evaluated based on the electrical resistance relationship information R9 and the electrical resistance Q5 of the compressor impeller 4 measured during periodic inspection of the turbocharger 3. Then, based on the evaluation result, the remaining life of the compressor impeller 4 evaluated in the above-mentioned remaining life evaluation step S5 is corrected.

[0091] In this case, for example, the remaining life of the compressor impeller 4 evaluated based on the electrical resistance Q5 of the compressor impeller 4 measured in the nth regular inspection and the electrical resistance relationship information R9 may be used as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th inspection. Note that the relationship between the electrical resistance of the compressor impeller 4 and the remaining life of the compressor impeller 4 illustrated in Fig. 13 indicates that as the electrical resistance of the compressor impeller 4 decreases due to changes in the material structure and dimensions of the compressor impeller 4, the remaining life of the compressor impeller 4 becomes shorter (the electrical resistance of the compressor impeller 4 decreases as time passes).

[0092] In this way, by correcting the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 (the remaining life depending on the history of the stress σ and the metal temperature Tm in the compressor impeller 4) using the electrical resistance Q5 of the compressor impeller 4 measured in the periodic inspection of the turbocharger 3, it is possible to improve the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to extend the replacement interval of the compressor impeller 4.

[0093] In some embodiments, the at least one parameter Qi used to correct the remaining life of the compressor impeller 4 may include a size Q6 of an internal defect of the compressor impeller 4. In this case, internal defect size relationship information R10 (see FIG. 14 ) indicating the relationship between the size of the internal defect of the compressor impeller 4 and the remaining life of the compressor impeller 4 is obtained in advance by a test or the like, and the remaining life of the compressor impeller 4 is evaluated based on the internal defect size relationship information R10 and the size Q6 of the internal defect of the compressor impeller 4 measured during periodic inspection of the turbocharger 3. Then, based on the evaluation result, the remaining life of the compressor impeller 4 evaluated in the above-mentioned remaining life evaluation step S5 is corrected.

[0094] In this case, for example, the size Q6 of the internal defect of the compressor impeller 4 measured in the nth regular inspection and the remaining life of the compressor impeller 4 evaluated based on the internal defect size relationship information R10 may be used as the initial value of the remaining life of the compressor impeller 4 evaluated in the remaining life evaluation step S5 for the period from the nth to the (n+1)th inspection. Note that the relationship between the size of the internal defect of the compressor impeller 4 and the remaining life of the compressor impeller 4 illustrated in Fig. 14 indicates that the remaining life of the compressor impeller 4 becomes shorter as the size of the internal defect of the compressor impeller 4 becomes larger (the size of the internal defect becomes larger as time passes). Furthermore, the size Q6 of the internal defect of the compressor impeller 4 may be measured by non-destructive testing such as ultrasonic flaw detection.

[0095] In this way, by correcting the evaluation result of the remaining life of the compressor impeller 4 in the above-mentioned remaining life evaluation step S5 (the remaining life according to the history of the stress σ and the metal temperature Tm in the compressor impeller 4) using the size Q6 of the internal defect in the compressor impeller 4 measured in the periodic inspection of the turbocharger 3, it is possible to improve the accuracy of the evaluation of the remaining life of the compressor impeller 4. This makes it possible to extend the replacement interval of the compressor impeller 4.

[0096] The present disclosure is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and appropriate combinations of these embodiments. For example, the remaining life assessment result of the compressor impeller 4 in the remaining life assessment step S5 may be corrected using two or more parameters selected from the following: a parameter Q1 obtained from a replica taken from the compressor impeller 4, a distortion Q2 of the compressor impeller 4, a hardness Q3 of the compressor impeller 4, a thickness Q4 of an oxide film formed on the surface of the compressor impeller 4, an electrical resistance Q5 of the compressor impeller 4, and a size Q6 of an internal defect in the compressor impeller 4.

[0097] The contents of the above-described embodiments can be understood, for example, as follows.

[0098] 1) A method (1) for assessing the remaining life of a compressor impeller according to at least one embodiment of the present disclosure includes: A method (1) for evaluating the remaining life of a compressor impeller (4) of a turbocharger (3), comprising: a rotation speed acquisition step (S1) of acquiring a rotation speed (N) of the turbocharger (3); a stress calculation step (S2) of calculating a stress (σ) generated in the compressor impeller (4) from the rotation speed (N) of the turbocharger (3) acquired in the rotation speed acquisition step (S1); an outlet temperature acquisition step (S3) of acquiring an outlet temperature (Te) of the compressor impeller (4); a metal temperature calculation step (S4) of calculating a metal temperature (Tm) of the compressor impeller (4) from the outlet temperature (Te) of the compressor impeller (4) acquired in the outlet temperature acquisition step (S3); and a remaining life evaluation step (S5) of evaluating the remaining life of the compressor impeller (4) from the stress (σ) calculated in the stress calculation step (S2) and the metal temperature (Tm) calculated in the metal temperature calculation step (S4) by utilizing a relationship between the stress (σ), metal temperature (Tm), and life of the compressor impeller (4) obtained in advance.

[0099] Damage (e.g., creep damage) occurs and progresses in the compressor impeller (4) depending on the history of the stress (σ) and metal temperature (Tm) of the compressor impeller (4) up to the present time. According to the method of 1) above, by utilizing the relationship between the stress (σ), metal temperature (Tm), and life of the compressor impeller (4) in the remaining life evaluation step (S5), it is possible to calculate the remaining life taking into account the damage to the compressor impeller (4) up to the present time from the stress (σ) calculated in the stress calculation step (S2) and the metal temperature (Tm) calculated in the metal temperature calculation step (S4), thereby enabling the remaining life of the compressor impeller (4) to be evaluated with high accuracy.

[0100] 2) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to 1) above, The remaining life assessment step (S5) a Larson-Miller parameter calculation step (S51) of calculating a Larson-Miller parameter (LMP) from the stress (σ) calculated in the stress calculation step (S2) by utilizing a relationship between the stress (σ) in the compressor impeller (4) and the Larson-Miller parameter (LMP) obtained in advance; and an allowable operating time calculation step (S52) of calculating an allowable operating time (tr) of the compressor impeller (4) from the Larson-Miller parameter (LMP) calculated in the Larson-Miller parameter calculation step (S51) and the metal temperature (Tm) calculated in the metal temperature calculation step (S2).

[0101] According to the method of 2), by using the Larson-Miller parameter (LMP), the allowable operating time (tr) of the compressor impeller (4) can be calculated, taking into account the creep damage to the compressor impeller (4) up to the present time, from the stress (σ) calculated in the stress calculation step (S2) and the metal temperature (Tm) calculated in the metal temperature calculation step (S4).The allowable operating time (tr) of the compressor impeller (4) calculated in the remaining life evaluation step (S5) can be used to accurately evaluate the remaining life of the compressor impeller (4).

[0102] 3) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to 2) above, The remaining life assessment step (S5) The method includes a damage degree calculation step (S53) of calculating a damage degree (D) of the compressor impeller (4) by dividing the actual operating time (ta) of the compressor impeller (4) by the permissible operating time (tr) of the compressor impeller (4) calculated in the permissible operating time calculation step (S52).

[0103] According to the method 3) above, in the damage degree calculation step (S53), the damage degree (D) of the compressor impeller (4) can be calculated from the actual operating time (ta) of the compressor impeller (4) and the allowable operating time (tr) of the compressor impeller (4). The damage degree (D) of the compressor impeller (4) calculated in the damage degree calculation step (S53) allows the degree of damage to the compressor impeller (4) to be grasped, and therefore the remaining life of the compressor impeller (4) can be evaluated with high accuracy.

[0104] 4) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to 2) above, The remaining life assessment step (S5) a differential damage degree calculation step (S55) of calculating, for each unit period, a differential damage degree (Di) of the compressor impeller (4) which is a damage degree for each unit period by dividing an actual operation time (ta) of the compressor impeller (4) in the unit period by the permissible operation time (tr) of the compressor impeller (4) calculated in the permissible operation time calculation step (S52); and a cumulative damage degree calculation step (S56) of calculating a cumulative damage degree (Dc) which is the sum of the classified damage degrees (Di) up to the present time.

[0105] According to the method 4), the cumulative damage level (Dc) can be calculated in the remaining life evaluation step (S5). The cumulative damage level (Dc) of the compressor impeller (4) calculated in the remaining life evaluation step (S5) allows the current degree of damage to the compressor impeller (4) to be determined, and therefore the remaining life of the compressor impeller (4) can be evaluated with high accuracy.

[0106] 5) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to any one of 1) to 4) above, In the outlet temperature acquisition step (S3), a value obtained by adding a temperature drop (ΔT) caused by the economizer (7) to a temperature (Td) of the working fluid of the compressor impeller (4) measured downstream of the economizer (7) located downstream of the compressor impeller (4) is acquired as the outlet temperature (Te).

[0107] According to the method of 5), in the outlet temperature obtaining step (S3), the outlet temperature (Te) of the compressor impeller (4) can be accurately estimated by adding the temperature drop (ΔT) caused by the economizer (7) to the temperature (Td) of the working fluid of the compressor impeller (4) downstream of the economizer (7). This makes it possible to accurately evaluate the remaining life of the compressor impeller (4) in the remaining life evaluating step (S5). Furthermore, according to the method of 5), the outlet temperature (Te) of the compressor impeller (4) can be estimated using the temperature (Td) of the working fluid of the compressor impeller (4) downstream of the economizer (7), which is generally measured in the engine system (2) including the turbocharger (3). According to the method 5), even if the engine system 2 is not provided with a temperature measuring device for measuring the outlet temperature (Te) of the compressor impeller 4, the remaining life evaluation method 1 for the compressor impeller 4 can be performed.

[0108] 6) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to any one of 1) to 5) above, The rotation speed acquisition step (S1) a pressure ratio acquisition step (S11) of acquiring a pressure ratio (Pr) of the compressor impeller (4); a flow rate acquisition step (S12) of acquiring a flow rate (Fr) of the compressor impeller (4); and a rotation speed calculation step (S13) of calculating the rotation speed (N) of the turbocharger (3) from the pressure ratio (Pr) acquired in the pressure ratio acquisition step (S11) and the flow rate (Fr) acquired in the flow rate acquisition step (S12) by utilizing a relationship between the pressure ratio (Pr), the flow rate (Fr) of the compressor impeller (4), and the rotation speed (N) of the turbocharger (3) acquired in advance.

[0109] According to the method of 6) above, by utilizing the relationship between the pressure ratio (Pr) and flow rate (Fr) of the compressor impeller (4) and the rotation speed (N) of the turbocharger (3), the rotation speed (N) of the turbocharger (3) can be calculated from the pressure ratio (Pr) acquired in the pressure ratio acquisition step (S11) and the flow rate (Fr) acquired in the flow rate acquisition step (S12). According to the method of 6) above, even if the engine system (2) is not provided with a rotation speed measurement device for measuring the rotation speed (N) of the turbocharger (3), the remaining life evaluation method (1) of the compressor impeller (4) can be performed.

[0110] 7) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to 6) above, The pressure ratio acquisition step (S11) an inlet pressure measuring step (S14) of measuring an inlet pressure (Ps) of the compressor impeller (4); an outlet pressure acquisition step (S15) of acquiring an outlet pressure (Pe) of the compressor impeller (4); and a pressure ratio calculation step (S16) of calculating a pressure ratio (Pr) of the compressor impeller (4) from the inlet pressure (Ps) of the compressor impeller (4) measured in the inlet pressure measurement step (S14) and the outlet pressure (Pe) of the compressor impeller (4) acquired in the outlet pressure acquisition step (S15).

[0111] According to the method of 7) above, the pressure ratio (Pr) of the compressor impeller (4) can be calculated from the inlet pressure (Ps) of the compressor impeller (4) measured in the inlet pressure measuring step (S14) and the outlet pressure (Pe) of the compressor impeller (4) acquired in the outlet pressure acquiring step (S15). According to the method of 7) above, even if the engine system (2) is not provided with a pressure ratio measuring device for measuring the pressure ratio (Pr) of the compressor impeller (4), the remaining life evaluation method (1) of the compressor impeller (4) can be performed.

[0112] 8) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to 7) above, In the outlet pressure acquiring step (S15), a value obtained by adding a pressure loss (ΔP) caused by the economizer (7) to a pressure (Pd) of the working fluid of the compressor impeller (4) measured downstream of the economizer (7) located downstream of the compressor impeller (4) is acquired as the outlet pressure (Pe).

[0113] According to the method of 8) above, in the outlet pressure obtaining step (S15), the outlet pressure (Pe) of the compressor impeller (4) can be accurately estimated by adding the pressure loss (ΔP) caused by the economizer (7) to the pressure (Pd) of the working fluid of the compressor impeller (4) downstream of the economizer (7). This makes it possible to accurately estimate the pressure ratio (Pr) of the compressor impeller (4) in the pressure ratio calculating step (S16). Furthermore, according to the method of 8) above, the pressure ratio (Pr) of the compressor impeller (4) can be estimated using the pressure (Pd) of the working fluid of the compressor impeller (4) downstream of the economizer (7), which are generally measured in the engine system (2) including the turbocharger (3), and the inlet pressure (Ps) of the compressor impeller (4). According to the method 8), even if the engine system 2 is not provided with a pressure measuring device for measuring the outlet pressure (Pe) of the compressor impeller 4 or a pressure ratio measuring device for measuring the pressure ratio (Pr) of the compressor impeller 4, the remaining life evaluation method 1 for the compressor impeller 4 can be performed.

[0114] 9) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to any one of 1) to 8) above, At least one parameter of the compressor impeller (4) measured during periodic inspection of the turbocharger (3) is used to correct the remaining life evaluation result of the compressor impeller (4) in the remaining life evaluation step.

[0115] According to the method of 9), the remaining life of the compressor impeller (4) is evaluated based on the history of the stress (σ) and the metal temperature (Tm) from the stress (σ) calculated in the stress calculation step (S2) and the metal temperature (Tm) calculated in the metal temperature calculation step (S4), and the evaluation result is corrected using at least one parameter of the compressor impeller measured in a periodic inspection of the turbocharger (3), thereby improving the accuracy of the evaluation of the remaining life of the compressor impeller (4). This enables the replacement interval of the compressor impeller 4 to be extended.

[0116] 10) In some embodiments, the method (1) for evaluating the remaining life of a compressor impeller according to 9) above, When n is an integer equal to or greater than 1, during a period from the nth regular inspection of the turbocharger (3) to the (n+1)th regular inspection, the evaluation result of the remaining life of the compressor impeller (4) in the remaining life evaluation step is corrected using the at least one parameter measured in the nth regular inspection of the turbocharger (3).

[0117] According to the method of 10), the remaining life evaluation result of the compressor impeller (4) in the remaining life evaluation step can be corrected using at least one parameter measured for the compressor impeller (4) in the most recent periodic inspection, thereby improving the accuracy of the remaining life evaluation of the compressor impeller (4). This allows the replacement interval of the compressor impeller 4 to be extended.

[0118] 11) In some embodiments, the method (1) for assessing the remaining life of a compressor impeller according to 9) above, The at least one parameter measured during the periodic inspection includes at least one of a parameter obtained from a replica taken from the compressor impeller (4), distortion of the compressor impeller (4), hardness of the compressor impeller (4), thickness of an oxide film formed on the surface of the compressor impeller (4), electrical resistance of the compressor impeller (4), and size of an internal defect in the compressor impeller (4).

[0119] According to the method of 11), the remaining life evaluated according to the history of the stress (σ) and the metal temperature (Tm) of the compressor impeller (4) can be corrected using at least one of the parameters (Q1) obtained from a replica taken from the compressor impeller (4), the distortion (Q2) of the compressor impeller (4), the hardness (Q3) of the compressor impeller (4), the thickness (Q4) of an oxide film formed on the surface of the compressor impeller (4), the electrical resistance (Q5) of the compressor impeller (4), and the size (Q6) of an internal defect in the compressor impeller (4). This improves the accuracy of the evaluation of the remaining life of the compressor impeller (4), and extends the replacement interval of the compressor impeller 4. [Explanation of symbols]

[0120] 1. Method for assessing remaining life of compressor impellers 2 Engine System 3. Turbocharger 4 Compressor impeller 5 Engine 6 Combustion gas supply line 7 Intercooler 8 Exhaust gas discharge line 9 Fuel injection valve 11 Control device 21 First pressure measuring device 22 Second pressure measuring device 23 First temperature measuring device 24 Second temperature measuring device 25 First rotation speed measuring device 31 Rotating shaft 32 Compressor 33 Turbine 34 Compressor housing 35 Turbine blades 36 Turbine housing 51 cylinders 52 Piston 53 Combustion chamber C material constant D Damage degree Dc cumulative damage degree Di classification damage degree E1,E2 period Fr flow rate L Total life LMP Larson-Miller parameters M1 Master Curve N rotation speed Pd pressure Pe outlet pressure Pr Pressure ratio Ps inlet pressure Qi parameters Q1 Grain size Q2 strain Q3 Hardness Q4 Oxide film thickness Q5 Electrical resistance Q6 Internal defect size R1,R2,R3,R4,R5,R6,R7,R8,R9,R10 Relationship information S1 RPM acquisition step S2 Stress calculation step S3 Outlet temperature acquisition step S4 Metal temperature calculation step S5 Remaining life assessment step S11 Pressure ratio acquisition step S12 Flow rate acquisition step S13 RPM calculation step S14 Inlet pressure measurement step S15 Outlet pressure acquisition step S16 Pressure ratio calculation step S51 Larson-Miller parameter calculation step S52 Allowable operating time calculation step S53 Damage calculation step Td temperature Te outlet temperature Tm Metal temperature Ts inlet temperature ta Actual operating time tr Allowable operating time

Claims

1. A method for evaluating the remaining life of a compressor impeller of a turbocharger, comprising: a rotation speed acquisition step of acquiring a rotation speed of the supercharger; a stress calculation step of calculating stress generated in the compressor impeller from the rotation speed of the turbocharger acquired in the rotation speed acquisition step; an outlet temperature acquisition step of acquiring an outlet temperature of the compressor impeller; a metal temperature calculation step of calculating a metal temperature of the compressor impeller from the outlet temperature of the compressor impeller acquired in the outlet temperature acquisition step; a remaining life evaluation step of evaluating a remaining life of the compressor impeller from the stress calculated in the stress calculation step and the metal temperature calculated in the metal temperature calculation step, using a relationship between the stress, metal temperature, and life of the compressor impeller that has been obtained in advance; A method for evaluating the remaining life of a compressor impeller comprising:

2. The remaining life assessment step includes: a Larson-Miller parameter calculation step of calculating a Larson-Miller parameter from the stress calculated in the stress calculation step by utilizing a relationship between the stress in the compressor impeller and a Larson-Miller parameter obtained in advance; an allowable operating time calculation step of calculating an allowable operating time of the compressor impeller from the Larson-Miller parameters calculated in the Larson-Miller parameter calculation step and the metal temperature calculated in the metal temperature calculation step, The method for evaluating the remaining life of a compressor impeller according to claim 1.

3. The remaining life assessment step includes: a damage degree calculation step of calculating a damage degree of the compressor impeller by dividing an actual operation time of the compressor impeller by the allowable operation time of the compressor impeller calculated in the allowable operation time calculation step, The method for evaluating the remaining life of a compressor impeller according to claim 2.

4. The remaining life assessment step includes: a fractional damage degree calculation step of calculating, for each unit period, a fractional damage degree, which is a damage degree of the compressor impeller for each unit period, by dividing an actual operation time of the compressor impeller in the unit period by the permissible operation time of the compressor impeller calculated in the permissible operation time calculation step; A cumulative damage degree calculation step of calculating a cumulative damage degree which is the sum of the classified damage degrees up to the present, The method for evaluating the remaining life of a compressor impeller according to claim 2.

5. In the outlet temperature acquisition step, a value obtained by adding a temperature drop caused by the economizer to a temperature of the working fluid of the compressor impeller measured downstream of a economizer located downstream of the compressor impeller is acquired as the outlet temperature. The method for evaluating the remaining life of a compressor impeller according to claim 1.

6. The rotation speed acquisition step a pressure ratio acquisition step of acquiring a pressure ratio of the compressor impeller; a flow rate acquiring step of acquiring a flow rate of the compressor impeller; a rotation speed calculation step of calculating a rotation speed of the turbocharger from the pressure ratio acquired in the pressure ratio acquisition step and the flow rate acquired in the flow rate acquisition step by utilizing a relationship between the pressure ratio of the compressor impeller, a flow rate, and a rotation speed of the turbocharger that has been acquired in advance. The method for evaluating the remaining life of a compressor impeller according to claim 1.

7. The pressure ratio acquisition step an inlet pressure measuring step of measuring an inlet pressure of the compressor impeller; an outlet pressure acquisition step of acquiring an outlet pressure of the compressor impeller; a pressure ratio calculation step of calculating a pressure ratio of the compressor impeller from the inlet pressure of the compressor impeller measured in the inlet pressure measurement step and the outlet pressure of the compressor impeller acquired in the outlet pressure acquisition step, The method for evaluating the remaining life of a compressor impeller according to claim 6.

8. In the outlet pressure acquiring step, a sum of a pressure of the working fluid of the compressor impeller measured downstream of an economizer located downstream of the compressor impeller and a pressure loss caused by the economizer is added to the pressure of the working fluid of the compressor impeller measured downstream of an economizer located downstream of the compressor impeller, and the resulting pressure is acquired as the outlet pressure. The method for evaluating the remaining life of a compressor impeller according to claim 7.

9. 9. The method for evaluating a remaining life of a compressor impeller according to claim 1, further comprising correcting an evaluation result of the remaining life of the compressor impeller in the remaining life evaluation step, using at least one parameter of the compressor impeller measured in a periodic inspection of the turbocharger.

10. 10. The method for evaluating a remaining life of a compressor impeller according to claim 9, wherein, where n is an integer equal to or greater than 1, an evaluation result of the remaining life of the compressor impeller in the remaining life evaluation step is corrected using the at least one parameter measured in an n-th regular inspection of the turbocharger during a period from an n-th regular inspection to an (n+1)-th regular inspection of the turbocharger.

11. 10. The method for evaluating a remaining life of a compressor impeller according to claim 9, wherein the at least one parameter measured during the periodic inspection includes at least one of a parameter acquired from a replica taken from the compressor impeller, distortion of the compressor impeller, hardness of the compressor impeller, a thickness of an oxide film formed on a surface of the compressor impeller, an electrical resistance of the compressor impeller, and a size of an internal defect in the compressor impeller.

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