A method and system for predicting an auxiliary power unit load compressor outlet temperature

Abstract

This invention belongs to the field of aero-engine technology and discloses a method and system for predicting the outlet temperature of an auxiliary power unit's load compressor. The method includes: acquiring the inlet total temperature, inlet static pressure, and outlet bleed air total pressure of the load compressor; calculating the pressure ratio between the outlet bleed air total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, and the relative equivalent rotational speed based on these parameters; and determining the load compressor outlet temperature based on the pressure ratio between the outlet bleed air total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent rotational speed, and the inlet total temperature. This invention uses multi-round engine test data for model building, ensuring reliable data sources. Compared with existing modeling methods, it considers the influence of the outlet bleed air total pressure on the bleed air temperature, resulting in an advanced modeling method, accurate prediction results, and simple implementation.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine technology, and specifically relates to a method and system for predicting the outlet temperature of an auxiliary power unit load compressor. Background Technology

[0002] The auxiliary power unit (APU) is a gas turbine engine with a load compressor, which is coaxial with the gas turbine engine and driven by the engine. When the main engine starts, the load compressor outlet produces compressed air to supply the downstream air turbine starter (ATS) for starting the main engine; when the main engine enters the bleed air control mode, the load compressor supplies compressed air to the cabin air conditioning system.

[0003] When supplying air to the air conditioner under environmental control, the air conditioning system needs to obtain the bleed air temperature T3 (°C) of the load compressor as an input parameter for calculating the bleed air flow rate. At the same time, because the engine's piping structure cannot be modified and temperature sensors cannot be directly installed, it is necessary to obtain the predicted value of the load compressor outlet bleed air temperature under the existing test parameters.

[0004] There are two main existing technologies for obtaining the outlet bleed air temperature of the load compressor: 1. Directly install a temperature sensor for measurement; 2. Obtain the relationship between T3 and T2, P2 by combining the total inlet temperature T2 and inlet static pressure P2 of the load compressor with engine bench test data, and make a two-dimensional interpolation table.

[0005] The disadvantages of the above-mentioned existing technologies are: 1. Directly installing the temperature sensor increases the complexity of the bleed air pipeline of the load compressor; 2. The fitting method of measuring the total inlet temperature T2 and static inlet pressure P2 of the load compressor does not consider the influence of the load compressor bleed air pressure change on the bleed air temperature, resulting in a large error. Through analysis of flight test data, the prediction error of this method is generally above 10℃, and the maximum prediction error can reach above 20℃.

[0006] In summary, the existing method for obtaining the outlet temperature of the load compressor requires additional measuring points, resulting in complex pipeline structures and insufficient prediction accuracy. Summary of the Invention

[0007] To address the above problems, this invention provides a method for predicting the outlet temperature of an auxiliary power unit's load compressor, comprising the following steps: Obtain the total inlet temperature, static inlet pressure, and total outlet bleed pressure of the load compressor; Based on the total inlet temperature, static inlet pressure, and total outlet bleed pressure of the load compressor, calculate the pressure ratio between the total outlet bleed pressure and the static inlet pressure, the temperature ratio between the total outlet temperature and the total inlet temperature, and the relative equivalent speed of the load compressor. The outlet temperature of the load compressor is determined based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature.

[0008] Further, obtaining the inlet total temperature, inlet static pressure, and outlet bleed gas total pressure of the loaded compressor includes the following steps: The total inlet temperature of the load compressor is measured upstream of the inlet guide vane, the static inlet pressure of the load compressor is measured upstream of the inlet guide vane, and the total outlet bleed pressure of the load compressor is measured downstream of the exhaust volute.

[0009] Further, based on the pressure ratio of the outlet bleed gas total pressure to the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature of the load compressor, the outlet temperature of the load compressor is determined, including the following steps: Determine the first functional relationship between the pressure correction factor and the relative reduced speed of the load compressor, and calculate the pressure correction factor based on the first functional relationship; Determine the second functional relationship between the total outlet bleed pressure and the inlet static pressure of the load compressor, the pressure correction factor, and the normalized pressure ratio; The normalized pressure ratio is determined based on the second functional relationship, and the normalized temperature ratio is determined based on the normalized pressure ratio. Determine the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor, and calculate the temperature correction factor based on the third functional relationship; Determine the fourth functional relationship between the outlet total temperature and the inlet total temperature of the load compressor, the normalized temperature ratio, and the temperature correction coefficient, and calculate the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor based on the fourth functional relationship. The outlet temperature of the load compressor is calculated based on the total inlet temperature of the load compressor and the temperature ratio between the total outlet temperature and the total inlet temperature.

[0010] Further, determining the first functional relationship between the pressure correction factor and the relative reduced speed of the loaded compressor includes the following steps: The first functional relationship is determined by fitting the pressure correction coefficients obtained from multiple calculations with the relative equivalent speed of the load compressor.

[0011] Further, the normalized temperature ratio is determined based on the normalized pressure ratio, including: Based on the experimental data, a two-dimensional interpolation table of normalized pressure ratio and normalized temperature ratio was fitted, and the normalized temperature ratio was determined based on the normalized pressure ratio and the two-dimensional interpolation table.

[0012] Further, the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor is determined, including the following steps: The third functional relationship is determined by fitting the temperature correction coefficients obtained from multiple calculations with the relative reduced speed of the load compressor.

[0013] Further, based on the pressure ratio of the outlet bleed gas total pressure to the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature of the load compressor, the outlet temperature of the load compressor is determined, including the following steps: The temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor, the pressure ratio between the outlet bleed air total pressure and the inlet static pressure, the relative equivalent speed, and the inlet total temperature are obtained through multiple calculations. A two-dimensional interpolation table is then obtained by linear interpolation. Based on the total inlet temperature of the load compressor, the pressure ratio between the total outlet bleed air pressure and the static inlet pressure, and the two-dimensional interpolation table, determine the temperature ratio between the total outlet temperature and the total inlet temperature of the load compressor. The outlet temperature of the load compressor is determined based on the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor, as well as the inlet total temperature.

[0014] Furthermore, the relative equivalent speed of the load compressor is calculated based on the inlet static pressure of the load compressor.

[0015] The present invention also provides an auxiliary power unit load compressor outlet temperature prediction system, comprising: The first calculation module is used to obtain the inlet total temperature, inlet static pressure and outlet bleed total pressure of the load compressor; The second calculation module is used to calculate the pressure ratio between the outlet bleed total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, and the relative equivalent speed of the load compressor based on the inlet total temperature, inlet static pressure, and outlet bleed total pressure of the load compressor. The third calculation module is used to determine the outlet temperature of the load compressor based on the pressure ratio between the outlet bleed total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature.

[0016] Furthermore, the third module is specifically used for: Determine the first functional relationship between the pressure correction factor and the relative reduced speed of the load compressor, and calculate the pressure correction factor based on the first functional relationship; Determine the second functional relationship between the total outlet bleed pressure and the inlet static pressure of the load compressor, the pressure correction factor, and the normalized pressure ratio; The normalized pressure ratio is determined based on the second functional relationship, and the normalized temperature ratio is determined based on the normalized pressure ratio. Determine the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor, and calculate the temperature correction factor based on the third functional relationship; Determine the fourth functional relationship between the outlet total temperature and the inlet total temperature of the load compressor, the normalized temperature ratio, and the temperature correction coefficient, and calculate the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor based on the fourth functional relationship. The outlet temperature of the load compressor is calculated based on the total inlet temperature of the load compressor and the temperature ratio between the total outlet temperature and the total inlet temperature.

[0017] The beneficial effects of this invention are: 1. This invention uses inlet total temperature, inlet static pressure, and outlet bleed air total pressure obtained from multiple rounds of engine test data to build a model, ensuring reliable data sources. Compared with existing modeling methods, this method is advanced, considering the influence of outlet bleed air total pressure PT on bleed air temperature T3. The prediction results of this invention are accurate; after comparison with experimental data, the prediction error of bleed air temperature T3 can be controlled within 7℃, which is 8℃ more accurate than current methods.

[0018] 2. The implementation of the present invention is simple, simplifying the calculation of the controller. The final functional relationship is transformed into a two-dimensional interpolation table output between the temperature ratio TR and T2,PR. The controller can quickly obtain the calculation results through linear interpolation.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the auxiliary power unit according to an embodiment of the present invention is shown; Figure 2 A flowchart illustrating a method for predicting the outlet temperature of an auxiliary power unit load compressor according to an embodiment of the present invention is shown. Figure 3 A schematic flowchart illustrating the calculation of the outlet temperature of the load compressor according to an embodiment of the present invention is shown; Figure 4 A schematic diagram of an auxiliary power unit load compressor outlet temperature prediction system according to an embodiment of the present invention is shown. Figure 5A schematic diagram showing the comparison between the predicted load compressor outlet temperature and engine test data according to an embodiment of the present invention is presented.

[0022] In the diagram: 1. Load compressor; 2. Inlet guide vane; 3. Compressor impeller; 4. Compressor diffuser; 5. Exhaust volute; 6. Load control valve; 7. Anti-surge control valve; 8. First measurement position; 9. Second measurement position. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein.

[0025] This invention provides a method and system for predicting the outlet temperature of the load compressor in an auxiliary power unit. Based on existing engine test parameters, the method calculates the outlet bleed air temperature of the load compressor under the engine's environmental control bleed air condition. This eliminates the need to add measuring points, simplifies the pipeline structure, and the calculation method is easy to implement with high prediction accuracy.

[0026] like Figure 1 As shown, the auxiliary power unit (APU) includes a load compressor 1, which includes an inlet guide vane 2, a compressor impeller 3, a compressor diffuser 4, and an exhaust volute 5 arranged coaxially along the airflow direction.

[0027] The exhaust end of the exhaust housing 5 is equipped with a load control valve 6 (LCV) and an anti-surge control valve 7 (SCV). The load control valve 6 is used to dredge the exhaust gas from the exhaust housing 5 to the aircraft cabin.

[0028] First, let me briefly introduce the environmental control operating mode of the Auxiliary Power Unit (APU): In the environmental control operating mode, the APU operates at 100% physical speed and has the ability to generate electricity. It can drive the reducer through the engine rotating shaft to achieve power output. At the same time, the anti-surge control valve 7 is closed, the load control valve 6 is open, and the inlet guide vane 2 is fixed at a certain angle θ to compress the air flowing into the load compressor 1. The compressed air is then sent into the aircraft cabin as the compressed air source for air conditioning.

[0029] like Figure 2 As shown, a method for predicting the outlet temperature of an auxiliary power unit load compressor 1 includes the following steps: S1. Obtain the inlet total temperature, inlet static pressure and outlet bleed total pressure of the load compressor 1.

[0030] For example, at the upstream position of the inlet guide vane 2 ( Figure 1 The first measurement position 8) measures the total inlet temperature T2 (unit: °C) of the loaded compressor 1; at the upstream position of the inlet guide vane 2 ( Figure 1 The first measurement position 8) measures the inlet static pressure P2 (unit: Pa) of the loaded compressor 1 at a position downstream of the exhaust volute 5. Figure 1 The total outlet bleed air pressure PT (unit: Pa) of the loaded compressor 1 is measured at the second measurement position 9. All the above test parameters are existing test parameters of the engine and no new measurement points are required.

[0031] In the data analysis of this embodiment of the invention, dimensionless parameters characterizing the compressor's properties are required. These dimensionless parameters include the pressure ratio of the outlet bleed gas total pressure to the inlet static pressure of the loaded compressor 1, the temperature ratio of the outlet total temperature to the inlet total temperature of the loaded compressor 1, and the relative reduced rotational speed of the loaded compressor 1. All of these dimensionless parameters can be calculated from the test parameters T2, P2, and PT.

[0032] It should be noted that all temperature units in the embodiments of this invention are °C, and all pressure units are absolute pressures in Pa.

[0033] S2. Based on the total inlet temperature, static inlet pressure, and total outlet bleed pressure of the load compressor 1, calculate the pressure ratio between the total outlet bleed pressure and the static inlet pressure, the temperature ratio between the total outlet temperature and the total inlet temperature, and the relative equivalent speed of the load compressor 1.

[0034] The pressure ratio of the outlet bleed air total pressure to the inlet static pressure of the load compressor 1 is calculated as follows:

[0035] In the formula, PR represents the pressure ratio of the total outlet bleed pressure of the load compressor 1 to the inlet static pressure.

[0036] Specifically, the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor 1 is calculated as follows:

[0037] In the formula, TR represents the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor 1.

[0038] The relative equivalent speed of the load compressor 1 is calculated based on the inlet static pressure of the load compressor 1, as follows: n_cor=

[0039] In the formula, n_cor represents the relative reduced speed of the load compressor 1.

[0040] S3. Determine the outlet temperature of the load compressor 1 based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature.

[0041] like Figure 3 As shown, for example, the outlet temperature of the load compressor 1 is calculated based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature, including the following steps: S31. Determine the first functional relationship between the pressure correction coefficient and the relative reduced speed of the load compressor 1, and calculate the pressure correction coefficient based on the first functional relationship, as follows: PR_fix=f1(n_cor) In the formula, PR_fix represents the pressure correction coefficient, and f1 represents the first function.

[0042] The determination of the first functional relationship between the pressure correction coefficient and the relative reduced speed of the load compressor 1 includes the following steps: data fitting is performed between the pressure correction coefficients obtained from multiple calculations and the relative reduced speed of the load compressor 1 to determine the first functional relationship.

[0043] S32. Determine the second functional relationship between the total outlet bleed air pressure and the inlet static pressure of the load compressor 1, the pressure correction coefficient, and the normalized pressure ratio, as follows: PR_nom = PR_fix × PR In the formula, PR_nom represents the normalized pressure ratio, and PR represents the pressure ratio of the total outlet bleed pressure to the inlet static pressure of the load compressor 1.

[0044] S33. Determine the normalized pressure ratio based on the second functional relationship, and then determine the normalized temperature ratio based on the normalized pressure ratio. Specifically, determining the normalized temperature ratio based on the normalized pressure ratio includes: fitting a two-dimensional interpolation table of the normalized pressure ratio PR_nom and the normalized temperature ratio TR_nom based on the experimental data, and then determining the normalized temperature ratio based on the normalized pressure ratio and the two-dimensional interpolation table. The two-dimensional interpolation table is shown in Table 1.

[0045] Table 1

[0046] S34. Determine the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor, and calculate the temperature correction factor based on the third functional relationship, as follows: TR_fix=f2(n_cor) In the formula, TR_fix represents the temperature correction coefficient, and f2 represents the third function.

[0047] The process of determining the third functional relationship between the temperature correction coefficient and the relative reduced speed of the load compressor 1 includes the following steps: data fitting between the temperature correction coefficients obtained from multiple calculations and the relative reduced speed of the load compressor 1 to determine the third functional relationship.

[0048] S35. Determine the fourth functional relationship between the outlet total temperature and the inlet total temperature of the load compressor 1, the normalized temperature ratio, and the temperature correction coefficient, and calculate the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor 1 based on the fourth functional relationship, as follows: TR = TR_fix × TR_nom In the formula, TR_nom represents the normalized temperature ratio.

[0049] S36. Based on the total inlet temperature of the load compressor 1 and the temperature ratio between the total outlet temperature and the total inlet temperature, calculate the outlet temperature of the load compressor 1 as follows: T3 = (T2 + 273.15) TR-273.15 In the formula, T3 represents the outlet temperature of the load compressor 1.

[0050] Because functions f1(n_cor) and f2(n_cor) involve advanced operations such as exponentiation and logarithm during parameter fitting, existing controllers cannot guarantee accuracy for such operations.

[0051] For example, the outlet temperature of the load compressor 1 is determined based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature, including the following steps: The temperature ratio TR between the outlet total temperature and the inlet total temperature of the load compressor 1, the pressure ratio PR between the outlet bleed air total pressure and the inlet static pressure, the relative equivalent speed, and the inlet total temperature T2 obtained through multiple calculations are used to obtain a two-dimensional interpolation table, as shown in Table 2.

[0052] Table 2

[0053] Using Table 2, based on the total inlet temperature T2 of the load compressor 1, the pressure ratio PR between the total outlet bleed air pressure and the inlet static pressure, and the two-dimensional interpolation table, the temperature ratio TR between the total outlet temperature and the total inlet temperature of the load compressor 1 is determined. Based on the temperature ratio TR between the total outlet temperature and the total inlet temperature of the load compressor 1, and the total inlet temperature, the outlet temperature T3 of the load compressor 1 is determined. That is, by substituting TR into the above relationship between the total outlet temperature, the total inlet temperature, and the temperature ratio, T3 is obtained.

[0054] The modeling method for calculating the outlet bleed air temperature T3 of the load compressor 1 in this embodiment of the invention is based on the model established from multiple rounds of engine test data, and the data source is reliable.

[0055] The outlet temperature prediction method of this invention takes into account the influence of bleed air pressure PT on bleed air temperature T3.

[0056] The outlet temperature prediction method of this invention is simple to implement and ultimately outputs a two-dimensional interpolation table. The controller can quickly obtain the calculation results through linear interpolation.

[0057] Based on the above-mentioned method for predicting the outlet temperature of the auxiliary power unit load compressor 1, such as Figure 4 As shown, this embodiment of the invention also provides an auxiliary power unit load compressor 1 outlet temperature prediction system, including a first calculation module, a second calculation module and a third calculation module.

[0058] The first calculation module is used to obtain the inlet total temperature, inlet static pressure, and outlet bleed total pressure of the load compressor 1. The second calculation module is used to calculate the pressure ratio between the outlet bleed total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, and the relative equivalent speed of the load compressor 1 based on the inlet total temperature, inlet static pressure, and outlet bleed total pressure of the load compressor 1.

[0059] The third calculation module is used to determine the outlet temperature of the load compressor 1 based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature.

[0060] The outlet temperature prediction method of this invention provides accurate prediction results, such as... Figure 5 As shown, by comparing with existing engine bench test data, the prediction error of bleed air temperature T3 can be controlled within 7℃, which is a significant improvement in prediction accuracy compared to the 20℃ error of existing methods.

[0061] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for assisted power plant load compressor outlet temperature prediction, characterized by, Includes the following steps: Obtain the total inlet temperature, static inlet pressure, and total outlet bleed pressure of the load compressor; Based on the total inlet temperature, static inlet pressure, and total outlet bleed pressure of the load compressor, calculate the pressure ratio between the total outlet bleed pressure and the static inlet pressure, the temperature ratio between the total outlet temperature and the total inlet temperature, and the relative equivalent speed of the load compressor. The outlet temperature of the load compressor is determined based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature.

2. The auxiliary power unit load compressor outlet temperature prediction method of claim 1, wherein, Obtaining the inlet total temperature, inlet static pressure, and outlet bleed gas total pressure of the loaded compressor includes the following steps: The total inlet temperature of the load compressor is measured upstream of the inlet guide vane, the static inlet pressure of the load compressor is measured upstream of the inlet guide vane, and the total outlet bleed pressure of the load compressor is measured downstream of the exhaust volute.

3. The auxiliary power unit load compressor outlet temperature prediction method of claim 1, wherein, The outlet temperature of the load compressor is determined based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature. This involves the following steps: Determine the first functional relationship between the pressure correction factor and the relative reduced speed of the load compressor, and calculate the pressure correction factor based on the first functional relationship; Determine the second functional relationship between the total outlet bleed pressure and the inlet static pressure of the load compressor, the pressure correction factor, and the normalized pressure ratio; The normalized pressure ratio is determined based on the second functional relationship, and the normalized temperature ratio is determined based on the normalized pressure ratio. Determine the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor, and calculate the temperature correction factor based on the third functional relationship; Determine the fourth functional relationship between the outlet total temperature and the inlet total temperature of the load compressor, the normalized temperature ratio, and the temperature correction coefficient, and calculate the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor based on the fourth functional relationship. The outlet temperature of the load compressor is calculated based on the total inlet temperature of the load compressor and the temperature ratio between the total outlet temperature and the total inlet temperature.

4. The auxiliary power unit load compressor outlet temperature prediction method of claim 3, wherein, Determining the first functional relationship between the pressure correction factor and the relative reduced speed of the loaded compressor includes the following steps: The first functional relationship is determined by fitting the pressure correction coefficients obtained from multiple calculations with the relative equivalent speed of the load compressor.

5. The auxiliary power unit load compressor outlet temperature prediction method of claim 3, wherein, Determining the normalized temperature ratio based on the normalized pressure ratio includes: Based on the experimental data, a two-dimensional interpolation table of normalized pressure ratio and normalized temperature ratio was fitted, and the normalized temperature ratio was determined based on the normalized pressure ratio and the two-dimensional interpolation table.

6. The auxiliary power unit load compressor outlet temperature prediction method of claim 3, wherein, Determining the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor includes the following steps: The third functional relationship is determined by fitting the temperature correction coefficients obtained from multiple calculations with the relative reduced speed of the load compressor.

7. The method for predicting the outlet temperature of the auxiliary power unit load compressor according to claim 1, characterized in that, The outlet temperature of the load compressor is determined based on the pressure ratio between the outlet bleed gas total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature. This involves the following steps: The temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor, the pressure ratio between the outlet bleed air total pressure and the inlet static pressure, the relative equivalent speed, and the inlet total temperature are obtained through multiple calculations. A two-dimensional interpolation table is then obtained by linear interpolation. Based on the total inlet temperature of the load compressor, the pressure ratio between the total outlet bleed air pressure and the static inlet pressure, and the two-dimensional interpolation table, determine the temperature ratio between the total outlet temperature and the total inlet temperature of the load compressor. The outlet temperature of the load compressor is determined based on the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor, as well as the inlet total temperature.

8. The method of claim 1-7, wherein, The relative equivalent speed of the load compressor is calculated based on the inlet static pressure of the load compressor.

9. An auxiliary power unit load compressor outlet temperature prediction system, characterized by, include: The first calculation module is used to obtain the inlet total temperature, inlet static pressure and outlet bleed total pressure of the load compressor; The second calculation module is used to calculate the pressure ratio between the outlet bleed total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, and the relative equivalent speed of the load compressor based on the inlet total temperature, inlet static pressure, and outlet bleed total pressure of the load compressor. The third calculation module is used to determine the outlet temperature of the load compressor based on the pressure ratio between the outlet bleed total pressure and the inlet static pressure, the temperature ratio between the outlet total temperature and the inlet total temperature, the relative equivalent speed, and the inlet total temperature.

10. The auxiliary power unit load compressor outlet temperature prediction system of Claim 9, wherein, The third module is specifically used for: Determine the first functional relationship between the pressure correction factor and the relative reduced speed of the load compressor, and calculate the pressure correction factor based on the first functional relationship; Determine the second functional relationship between the total outlet bleed pressure and the inlet static pressure of the load compressor, the pressure correction factor, and the normalized pressure ratio; The normalized pressure ratio is determined based on the second functional relationship, and the normalized temperature ratio is determined based on the normalized pressure ratio. Determine the third functional relationship between the temperature correction factor and the relative reduced speed of the load compressor, and calculate the temperature correction factor based on the third functional relationship; Determine the fourth functional relationship between the outlet total temperature and the inlet total temperature of the load compressor, the normalized temperature ratio, and the temperature correction coefficient, and calculate the temperature ratio between the outlet total temperature and the inlet total temperature of the load compressor based on the fourth functional relationship. The outlet temperature of the load compressor is calculated based on the total inlet temperature of the load compressor and the temperature ratio between the total outlet temperature and the total inlet temperature.

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