Bleed air pressure evaluation method and system

Abstract

The invention provides a bleed air pressure evaluation method, which is used for evaluating the bleed air pressure of a bleed air position of an intermediate casing outlet of a gas compressor, and comprises the following steps: acquiring the average total pressure and the reduced flow of the bleed air position, determining the wall surface static pressure of the bleed air position through a static pressure determination formula, and then evaluating the bleed air pressure by assisting the determined wall surface static pressure. The invention also provides a bleed air pressure evaluation system for realizing the bleed air pressure evaluation method. According to the bleed pressure evaluation method, the bleed pressure of the bleed position of the outlet of the middle casing of the gas compressor can be quickly evaluated.

Description

Technical Field

[0001] The invention relates to a bleed air pressure assessment method and also to a bleed air pressure assessment system. Background Art

[0002] In the design of the engine air system, it is often necessary to draw out some high-pressure gas from the compressor outlet wall for cooling and sealing the engine's bearing pivots and turbine components. The static pressure at the bleed position directly affects the bleed effect of the air system, thereby affecting the cooling and sealing effect of the bearing pivots or turbine components. The air system is evaluated through parameters such as pressure and temperature provided by the compressor, turbine and other professionals. If the bleed pressure is insufficient, the overall performance and the compressor and other professionals will be coordinated to readjust the design. The iteration time between the air system and the overall performance, compressor, turbine and other professionals directly affects the engine design cycle.

[0003] Therefore, it is necessary to provide a method for quickly evaluating the bleed air pressure. Summary of the invention

[0004] The object of the present invention is to provide a bleed air pressure evaluation method, which can quickly evaluate the bleed air pressure at the bleed air position of the intermediate casing outlet of the compressor.

[0005] The invention provides a bleed air pressure evaluation method for evaluating the bleed air pressure at a bleed air position at an intermediate casing outlet of a compressor.

[0006] Step S1, obtaining the average total pressure and equivalent flow rate of the air inlet position. Step S2, determining the wall static pressure of the air inlet position by the following static pressure determination formula:

[0007] P s_hub / P s_Ave =f(m 25_cor )

[0008] Among them, P s_hub is the wall static pressure that needs to be determined, P s_Ave 、m 25_cor are the average total pressure and the equivalent flow rate obtained in step S1, respectively, f(m 25_cor ) represents m 25_cor A unary function of .

[0009] Step S3: Evaluate the bleed air pressure with the aid of the wall static pressure determined in step S2.

[0010] In one embodiment, the univariate function is an n-th power function, where n≥2.

[0011] In one embodiment, f(m 25_cor) are determined by the following coefficient determination steps: step S41, obtaining corresponding parameters under n+1 representative operating points, wherein the corresponding parameters are the wall static pressure, average total pressure and equivalent flow rate at the air bleed position; step S42, substituting the corresponding parameters under the n+1 representative operating points into the static pressure determination formula one by one, and solving to obtain the n+1 coefficients.

[0012] In one embodiment, f(m 25_cor ) is determined by the following power determination steps: Step S50, obtaining corresponding parameters under the reference operating point, wherein the corresponding parameters are the wall static pressure, average total pressure and reduced flow rate at the bleed air position; Step S51, initializing f(m 25_cor ) to a power of n = 2; Step S52, determine f(m 25_cor ) to obtain the static pressure determination formula; step S53, substitute the average total pressure and the reduced flow rate in the corresponding parameters obtained in step S50 into the static pressure determination formula obtained in step S52 to determine the wall static pressure; step S54, determine whether the difference between the wall static pressure determined in step S53 and the wall static pressure in the corresponding parameters obtained in step S50 is within a predetermined range; step S55, in response to the difference in step S54 not being within the predetermined range, make n=n+1, and repeat steps S52 to S54; step S56, in response to the difference in step S54 being within the predetermined range, determine n at this time as f(m 25_cor ) to the power of .

[0013] In one embodiment, the corresponding parameters under the n+1 representative operating points are obtained by simulation.

[0014] In one embodiment, the simulation method uses a two-dimensional streamline curvature method.

[0015] In one embodiment, n=2.

[0016] In one embodiment, f(m 25_cor ) varies with the shape of the flow channel at the root of the intermediate casing outlet.

[0017] In one embodiment, in step S3, the wall static pressure is used as the bleed air pressure.

[0018] The present invention also provides a bleed air pressure assessment system, comprising a memory and a processor, which are respectively used to store a program and execute the program. When the processor executes the program, the above-mentioned bleed air pressure assessment method is implemented.

[0019] In the above bleed air pressure evaluation method and system, by using the static pressure determination formula, only the average total pressure and the reduced flow rate of the bleed air position at the intermediate casing outlet of the compressor need to be input to obtain the wall static pressure at the bleed air position, thereby evaluating the bleed air pressure. Therefore, the bleed air pressure at the bleed air position at the intermediate casing outlet of the compressor can be quickly and conveniently evaluated.

[0020] Furthermore, after the univariate function in the static pressure determination formula is set to a power function, the coefficient of the power function can be determined by simulating several representative operating points, which can further simplify the entire process of obtaining the static pressure determination formula.

[0021] Furthermore, by increasing the power of the power function step by step, a static pressure determination formula with an accuracy that meets expectations can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0023] Figure 1 is a schematic diagram exemplarily showing a fan / boost stage in a compressor.

[0024] Figure 2 is an exemplary flow chart of a bleed air assessment method using a quadratic power function as an example.

[0025] Figure 3 is an exemplary flow chart of a bleed air assessment method when power determination is required. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific implementation methods and accompanying drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from this description. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific implementation method.

[0027] For example, a first feature described later in the specification as being formed above or on a second feature may include an embodiment in which the first feature and the second feature are formed by direct connection, and may also include an embodiment in which an additional feature is formed between the first feature and the second feature, so that the first feature and the second feature may not be directly connected. Further, when a first element is described as being connected or combined with a second element, the description includes an embodiment in which the first element and the second element are directly connected or combined with each other, and also includes an embodiment in which one or more other intervening elements are added to indirectly connect or combine the first element and the second element.

[0028] Figure 1 An example configuration of a full-scale fan / boost stage component in a compressor is shown. In a compressor, after the airflow passes through the fan 1, it is divided into two ducts, the outer duct is discharged through the outlet guide vane (also known as OGV) 3, and the inner duct enters the core engine through the boost stage 2 and the intermediate casing 4. The bleed position 5 is located at the outlet of the intermediate casing 4, usually at the root of the outlet of the intermediate casing 4 after the boost stage 2. The air system usually has a wall opening at the bleed position 5 for bleed air.

[0029] Therefore, the wall static pressure is the main input parameter that the fan / boost stage designer needs to provide to the air system designer. The conventional way to obtain the wall static pressure is to determine the S2 parameter positive problem or to determine it through three-dimensional CFD simulation. The conventional method consumes a lot of time and energy, and the more operating points the air system needs to determine, the longer it takes. It usually takes a week to complete a round of air system input determination, which means that the iteration time between the air system and the overall performance, compressor and other disciplines is long, and the design rework will lead to a waste of manpower and time costs.

[0030] The present invention provides a bleed air pressure assessment method for assessing the bleed air pressure at a bleed air position 5 at an outlet of an intermediate casing 4 of a compressor.

[0031] like Figure 2 As shown, the bleed air pressure assessment method includes step S1, step S2 and step S3. It should be understood that the drawings are only for illustration and are not drawn in proportion, and should not be used to limit the actual protection scope of the present invention.

[0032] Step S1, obtaining the average total pressure P at the air inlet position 5 s_Ave and the equivalent flow rate m 25_cor .

[0033] For example, for the fan\boost stage, the average total pressure P s_Ave and the equivalent flow rate m 25_cor Can be provided by Total Performance Professional.

[0034] Step S2: determine the wall static pressure Ps_hub at the air intake position 5 by the following static pressure determination formula.

[0035] P s_hub / P s_Ave =f(m 25_cor )

[0036] As mentioned above, P s_hub The static pressure of the wall mentioned above needs to be determined. s_Ave 、m 25_cor are the average total pressure and equivalent flow rate obtained in step S1. 25_cor ) represents m 25_corA unary function of .

[0037] In other words, the wall static pressure P s_hub With the average total pressure P s_Ave The ratio is only related to the reduced flow rate m 25_cor Related.

[0038] Step S3: Using the wall static pressure P determined in step S2 s_hub , assess the bleed air pressure.

[0039] In one embodiment, in step S3, the wall static pressure P s_hub as bleed air pressure.

[0040] The above static pressure determination formula gives the wall static pressure P at the bleed air position 5 at the outlet of the intermediate casing 4: s_hub With the average total pressure P s_Ave , equivalent flow rate m 25_cor Therefore, in the design, the wall static pressure P of the bleed air position 5 can be quickly given according to the overall performance parameters. s_hub Specifically, in the above-mentioned bleed air pressure evaluation method, by obtaining the average total pressure P at the bleed air position 5 s_Ave and the equivalent flow rate m 25_cor Substituting these two parameters into the above static pressure determination formula can determine the wall static pressure P s_hub , and then evaluate the bleed air pressure.

[0041] The above-mentioned bleed air pressure assessment method is simple to implement and can quickly provide the wall static pressure of different working conditions of the boost stage as an input for pressure assessment of the air system.

[0042] The above static pressure determination formula is derived by the inventor through empirical assumptions and theories. The specific derivation process will be described in detail below.

[0043] The inventors analyzed that the airflow at the outlet of the intermediate casing has no tangential velocity, and selected a fluid micro-group at the outlet of the intermediate casing as the research object, and obtained the following from the radial balance equation:

[0044]

[0045] In formula (1), V is the velocity, ρ is the density of the fluid micro-group, D is the streamline curvature radius (equivalent to the flow channel curvature radius on the wall), is the radial gradient of static pressure. Further, according to the Mach number, the formula is defined as The derivation is as follows:

[0046]

[0047] In formula (2), ρ represents gas density, T represents gas static temperature, and k is gas state parameter. According to the ideal gas state equation P = ρRT, substituting into formula (2), we get:

[0048]

[0049] P s represents the static pressure of gas. According to the relationship between total pressure, static pressure and Ma, we can get:

[0050]

[0051]

[0052] From formula (5), we know that the ratio of the static pressure gradient to the total pressure Pt is related to the streamline curvature radius D and the local Mach number Ma.

[0053] According to the static pressure radial balance and design experience, the spanwise distribution of static pressure at the outlet of the intermediate casing is approximately linear, that is, the static pressure gradient is a constant, we can further get the following formula:

[0054]

[0055]

[0056]

[0057] In the above formula, P s_hub where represents the wall static pressure at the bleed air position 5 of the intermediate casing outlet, and Dr represents the geometric factor related to the geometry. From formula (8), we know that the ratio of the wall static pressure to the total pressure is only related to Ma and the geometric factor. Further inference for the geometrically determined intermediate casing is:

[0058]

[0059]

[0060] In the above formula, P t_Ave is the average total pressure at the outlet of the intermediate casing, Ma Ave is the average Mach number at the intermediate casing outlet, m cor represents the outlet equivalent flow, m represents the outlet physical flow, T tAve is the average total temperature at the outlet of the intermediate casing. It can be seen from formula (9) that for the intermediate casing with a certain geometry, the ratio of the static pressure on the wall at the outlet root to the average total pressure of the cross section is a function of the outlet reduced flow rate.

[0061] Therefore, in the above-mentioned bleed air pressure assessment method, by obtaining the average total pressure P at the bleed air position 5 s_Ave and the equivalent flow rate m 25_cor These two parameters can determine the wall static pressure P s_hub . Equivalent flow rate m 25_corIt can also be called converted flow or implicit flow.

[0062] The aforementioned univariate function may be an nth power function, where n≥2. That is, the ratio of the wall static pressure to the average total pressure is set as a power function of the converted flow rate, which is particularly suitable for practical engineering applications. Figure 2 In the embodiment shown, n=2.

[0063] Furthermore, f(m 25_cor ) is determined by a coefficient determination step. The coefficient determination step includes step S41 and step S42.

[0064] Step S41, obtaining corresponding parameters under n+1 representative operating points.

[0065] Among them, the above-mentioned corresponding parameter is the wall static pressure P at the above-mentioned air inlet position s_hub , average total pressure P s_Ave and the equivalent flow rate m 25_cor In one embodiment, the corresponding parameters under the above n+1 representative operating points can be obtained by simulation. Further, the simulation can adopt a two-dimensional streamline curvature method, that is, by means of an S2 direct problem.

[0066] Step S42: Substitute the corresponding parameters of the aforementioned n+1 representative operating points into the aforementioned static pressure determination formula one by one, and solve to obtain the aforementioned n+1 coefficients.

[0067] The above coefficient determination steps are particularly suitable for f(m 25_cor ) is a case where the power n of the power function is determined. 25_cor ) can change with the shape of the flow channel at the outlet root of the intermediate casing 4. When the shape of the flow channel at the outlet root of the intermediate casing 4 remains unchanged, the three coefficients A, B and C determined in the above coefficient determination step can remain unchanged without re-determination. Therefore, it can be applicable to different fan boosting stage flow design schemes.

[0068] by Figure 2 As shown in the figure, n = 2 is taken as an example, that is, the wall static pressure P s_hub With the average total pressure P s_Ave The ratio is set to the equivalent flow rate m 25_cor In other words, the static pressure determination formula is as follows (11). Where A, B and C are f(m 25_cor ) of the three coefficients.

[0069] P s_hub / P s_Ave =Am 25_cor 2 +Bm 25_cor +C (11)

[0070] For example, first, the average total pressure, wall static pressure and reduced flow rate at the bleed air position 5 of any three operating points (as examples of n+1 representative operating points) can be determined by the S2 forward problem. Then, the average total pressure, wall static pressure and reduced flow rate of the three operating points determined above are substituted into formula (11), and three quadratic equations about coefficients A, B and C can be obtained. Finally, the specific values ​​of coefficients A, B and C can be solved by these three quadratic equations.

[0071] After the above coefficients are determined, the static pressure of the intermediate casing outlet wall at all other operating points can be determined based on the overall performance design requirements for the fan boost stage and provided to the air system as input for bleed air pressure evaluation.

[0072] exist Figure 3 In the embodiment shown, f(m 25_cor ) is determined by a power determination step. The power determination step includes steps S50, S51, S52, S53, S54, S55 and S56.

[0073] Step S50, obtaining the corresponding parameters under the reference operating point, wherein the corresponding parameters are the wall static pressure P at the aforementioned air bleed position. s_hub , average total pressure P s_Ave and the equivalent flow rate m 25_cor .

[0074] Step S51, initialization f(m 25_cor ) to the power of n=2.

[0075] Step S52: Determine f(m 25_cor )’s n+1 coefficients, we get the aforementioned static pressure determination formula.

[0076] In the illustrated embodiment, f(m 25_cor ) can be determined by the aforementioned coefficient determination step, still using the reference numerals S41 and S42. 25_cor ) can also be obtained through the database.

[0077] Step S53: The average total pressure P in the corresponding parameter obtained in step S50 is s_Ave and the equivalent flow rate m 25_cor Substitute into the above static pressure determination formula obtained in step S52 to determine the wall static pressure P s_hub .

[0078] Step S54: Determine the wall static pressure P determined in step S53. s_hub The wall static pressure P in the corresponding parameter obtained in step S50s_hub Is the difference within the predetermined range?

[0079] Step S55: In response to the difference in step S54 not being within the predetermined range, such that n=n+1, steps S52 to S54 are repeated.

[0080] Step S56: In response to the difference in step S54 being within a predetermined range, n at this time is determined to be f(m 25_cor ) to the power of .

[0081] In practical applications, the higher the power, the higher the accuracy. You can determine how much accuracy you need based on your needs, and thus determine how many power functions you need. For example, in practical applications, when n = 2, the wall static pressure P determined by the above static pressure determination formula is s_hub If the error can be within 200Pa, it is considered that the accuracy can reach an acceptable level in engineering applications. At this time, the quadratic function is sufficient. If higher accuracy is required, a cubic or higher power function can be used.

[0082] It can be understood that the higher the power, the more coefficients need to be solved, and the number of representative operating points that need to be determined in advance also increases accordingly. After the above power and coefficient are determined, the wall static pressure of the bleed air position at the intermediate casing outlet of all other operating points can be determined.

[0083] It is understood that specific words are used herein to describe embodiments of the present invention, such as "one embodiment", "another embodiment" and / or "some embodiments" to refer to a certain feature, structure or characteristic associated with at least one embodiment of the present invention. Therefore, it should be emphasized and noted that "one embodiment" or "another embodiment" mentioned twice or more in different locations in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics of one or more embodiments of the present invention may be appropriately combined.

[0084] The present invention also provides a bleed air pressure assessment system. The bleed air pressure assessment system includes a memory and a processor, which are respectively used to store a program and execute the program. When the processor executes the program, the bleed air pressure assessment method is implemented.

[0085] In engineering applications, there are often dozens or even hundreds of operating points that need to be determined. Compared with determining the wall static pressure through S2 parameter forward problem determination or three-dimensional CFD determination, the above bleed air pressure assessment method is faster and more convenient. The work that takes a week to complete using the conventional method can be completed in just one day using the above bleed air pressure assessment method, which can greatly speed up the iteration speed between different disciplines in the engine design process and shorten the entire engine design cycle.

[0086] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A bleed air pressure assessment method for assessing the bleed air pressure at a bleed air position at an intermediate casing outlet of a compressor, characterized in that: include: Step S1, obtaining the average total pressure and equivalent flow rate of the air bleed position; Step S2: Determine the wall static pressure at the air bleed position by the following static pressure determination formula: P s_hub / P s_Ave =f(m 25_cor ) Among them, P s_hub is the wall static pressure that needs to be determined, P s_Ave 、m 25_cor are the average total pressure and the equivalent flow rate obtained in step S1, respectively, f(m 25_cor ) represents m 25_cor A univariate function of ; Step S3: Evaluate the bleed air pressure with the aid of the wall static pressure determined in step S2.

2. The bleed air pressure assessment method according to claim 1, characterized in that: The univariate function is an n-th power function, where n≥2.

3. The bleed air pressure assessment method according to claim 2, characterized in that: f(m 25_cor ) is determined by the following coefficient determination steps: Step S41, obtaining corresponding parameters at n+1 representative operating points, wherein the corresponding parameters are the wall static pressure, average total pressure and reduced flow rate at the air bleed position; Step S42: Substitute the corresponding parameters of the n+1 representative operating points into the static pressure determination formula one by one, and solve to obtain the n+1 coefficients.

4. The bleed air pressure assessment method according to claim 2, characterized in that: f(m 25_cor ) is determined by the following power determination steps: Step S50, obtaining corresponding parameters at a reference operating point, wherein the corresponding parameters are the wall static pressure, average total pressure and reduced flow rate at the bleed air position; Step S51, initialization f(m 25_cor ) to the power of n = 2; Step S52: Determine f(m 25_cor ) to obtain the static pressure determination formula; Step S53, substituting the average total pressure and the reduced flow rate in the corresponding parameters obtained in step S50 into the static pressure determination formula obtained in step S52 to determine the wall static pressure; Step S54, determining whether the difference between the wall static pressure determined in step S53 and the wall static pressure in the corresponding parameter obtained in step S50 is within a predetermined range; Step S55, in response to the difference in step S54 not being within the predetermined range, so that n=n+1, repeating steps S52 to S54; Step S56: In response to the difference in step S54 being within a predetermined range, n at this time is determined to be f(m 25_cor ) to the power of .

5. The bleed air pressure assessment method according to claim 3, characterized in that: The corresponding parameters under the n+1 representative operating points are obtained by simulation means.

6. The bleed air pressure assessment method according to claim 5, characterized in that: The simulation method adopts a two-dimensional streamline curvature method.

7. The bleed air pressure assessment method according to claim 2, characterized in that: n＝2。 8. The bleed air pressure assessment method according to claim 2, characterized in that: in, f(m 25_cor ) varies with the shape of the flow channel at the root of the intermediate casing outlet.

9. The bleed air pressure assessment method according to claim 1, characterized in that: In step S3, the wall static pressure is used as the bleed air pressure.

10. A bleed air pressure assessment system, comprising a memory and a processor, for storing a program and executing the program respectively, characterized in that: When the processor executes the program, the bleed air pressure assessment method according to any one of claims 1 to 9 is implemented.

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