Turbine casing air casing type cooling structure and design method thereof

Abstract

The application provides a turbine casing air casing type cooling structure design method, comprising the following steps: step one, determining the design constraints and design targets of the turbine casing air casing type cooling structure; step two, establishing a heat balance equation according to a heat transfer model composed of the air casing type cooling structure, the turbine casing and the rotor, and evaluating the heat required to be taken away by the air casing type cooling structure for cooling the turbine casing; step three, obtaining key parameters of the air casing type cooling structure according to the design targets, the heat required to be taken away for cooling and the design constraints, wherein the key parameters comprise an air casing height and an air bleed amount; step four, evaluating the engine performance loss under the key parameters; step five, taking the flow demand of the turbine casing air casing type cooling structure as a target, taking the aerodynamic parameters of the air bleed and exhaust of the air casing type cooling structure as boundaries, and designing an air bleed flow path of the air casing type cooling structure under the premise of satisfying the flow resistance loss to obtain the air bleed flow path of the air casing type cooling structure; and step six, evaluating whether the air bleed flow path can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of turbine casing structure design, and particularly relates to a turbine casing air casing type cooling structure and a design method thereof. BACKGROUND

[0002] The turbine casing assembly of an aero-engine is an important component of the engine, and is mainly used for supporting the turbine of the engine and blocking high-temperature combustion gas and low-temperature bearings. The position and function of the turbine casing determine that the casing has the characteristics of high temperature and complex structure, so the turbine casing usually needs a cooling structure.

[0003] A common external cooling method for the turbine is to introduce a cold gas on the surface of the turbine casing to cool the turbine casing. The design process of the turbine casing air casing cooling structure is as follows: given a design condition, the temperature, pressure and other parameters of the cooling gas are preliminarily assumed based on experience, the temperature distribution of the turbine casing under this condition is obtained through numerical simulation or test verification, and the related parameters of the cooling gas are iteratively corrected, so as to complete the scheme design. However, this design method requires high experience of the designer, if the initial assumption parameters are unreasonable, multiple rounds of iterative tests or calculations are needed, and when the parameters change greatly, even a new design is needed, which exists a lot of repeated work and has low design efficiency. SUMMARY

[0004] The application aims to provide a turbine casing air casing type cooling structure and a design method thereof, so as to solve or alleviate at least one problem in the background art.

[0005] In one aspect, the application provides a turbine casing air casing type cooling structure design method, which comprises:

[0006] Step one, determining the design constraints and design targets of the turbine casing air casing type cooling structure;

[0007] Step two, establishing a heat balance equation according to a heat transfer model composed of the turbine casing air casing type cooling structure, the turbine casing and the rotor, and evaluating the heat required to be taken away by the air casing type cooling structure for cooling the turbine casing;

[0008] Step three, performing heat transfer design on the turbine casing air casing type cooling structure, obtaining the key parameters of the turbine casing air casing type cooling structure according to the design targets, the heat required to be taken away for cooling and the turbine casing structure design constraints, wherein the key parameters include the air casing height and the air quantity;

[0009] Step four, evaluating the engine performance loss under the key parameters, if the evaluation result meets the requirement, the next step is performed, if the evaluation result does not meet the requirement, the step one is returned;

[0010] Step 5: With the goal of meeting the flow requirements of the turbine casing air-shell cooling structure, and taking the aerodynamic parameters of the exhaust and intake air of the turbine casing air-shell cooling structure as the boundary, the exhaust airflow path is designed to obtain the exhaust airflow path of the turbine casing air-shell cooling structure under the premise of meeting the flow resistance loss.

[0011] Step 6: Evaluate whether the airflow path can be implemented. If there are difficulties in implementing the pipeline layout, return to Step 1 and redesign until the requirements are met.

[0012] Furthermore, the basic profile of the gas casing cooling structure is determined based on the main structure of the turbine casing, thereby determining the design constraints of the turbine casing gas casing cooling structure. The annular radius of the turbine casing gas casing cooling structure is larger than the outer radius of the turbine casing, and the length of the turbine casing gas casing cooling structure along the engine axis depends on the location of the casing cooling and heat dissipation requirements.

[0013] Furthermore, in step one, the design objectives are determined based on the long-term temperature requirements of the casing material, the temperature requirements for engine strength life, the temperature requirements for engine deformation, and the temperature limits of the engine outer wall.

[0014] Furthermore, in step one, the turbine casing gas shell cooling structure draws air from the compressor blade tip. The compressor blade tip pressure at the air drawing position is higher than the exhaust pressure of the gas shell cooling structure, and the compressor blade tip temperature at the air drawing position is lower than the average surface temperature of the turbine casing.

[0015] Furthermore, in step two, the heat balance equation is:

[0016]

[0017] In the formula, Q lq The airflow designed for cooling needs to remove heat, Q hjdl To remove heat from the engine environment due to weak convection, Q jxfs Q represents the radiant heat from the casing to the gas shell. zzfs Radiated heat from the main channel rotor to the casing, Q jzdr Q is used to conduct heat to the engine stator blades mounted on the casing. zldl The main body of the strong convection heat to the casing, Q hjfs This refers to the radiated heat from the casing to the infinitely large external space.

[0018] Furthermore, in step five, a fluid grid for the airflow is first established, and the airflow characteristics of the airflow path are simulated through the fluid grid.

[0019] Furthermore, in step five, the fluid mesh includes:

[0020] The first chamber characterizing the bleed-in position at the compressor blade tip;

[0021] The second cavity characterizing the exhaust boundary of the gas-shell cooling structure; and

[0022] At least two third chambers are characterized in the cold air flow at locations with smaller flow interception and larger geometric structure.

[0023] Furthermore, when the outer surface of the turbine casing has grooves, the gas shell layer of the turbine casing gas shell cooling structure does not penetrate deep into the grooves.

[0024] Furthermore, by providing ribs extending into the grooves on the gas shell layer, the airflow path is improved.

[0025] On the other hand, this application provides a turbine casing gas shell cooling structure, which is obtained by adopting any of the turbine casing gas shell cooling structure design methods described above.

[0026] The turbine casing air-shell cooling structure and its design method provided in this application are a systematic design approach. By employing widely used convection and radiation heat transfer models, the method becomes more operational. Several key parameters are proposed during the design process, which can serve as a data basis for adjusting the design and evaluating the design effect. This method can greatly improve design efficiency, shorten the design cycle, and reduce human and material costs. Attached Figure Description

[0027] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0028] Figure 1 This is a flowchart illustrating the design method of the turbine casing air-shell cooling structure of this application.

[0029] Figure 2 This is a schematic diagram of a typical engine structure in this application.

[0030] Figure 3 This is a schematic diagram of the gas shell parameters in this application.

[0031] Figure 4 This is a schematic diagram of the thermal balance of the gas casing, turbine casing, and main channel rotor in this application.

[0032] Figure 5 This is a schematic diagram of the convective heat transfer model that illustrates the principle in this application.

[0033] Figure 6 This is a schematic diagram of a fluid network in one embodiment of this application.

[0034] Figure 7 This is a schematic diagram of the airflow path in one embodiment of this application.

[0035] Figure 8 This is a schematic diagram of the rib plate location in one embodiment of this application. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, the turbine casing air-shell cooling structure design method provided in this application mainly includes two parts: heat transfer design and flow design. The specific steps include:

[0038] Step 1: Define the design objectives and constraints of the turbine casing air-shell cooling structure.

[0039] Design constraints: Determine the basic profile of the gas casing cooling structure (or gas casing) based on the main structure of the turbine casing—such as the inner radius of the annular cavity and the length along the engine axial direction.

[0040] by Figure 2 Taking the typical engine structure shown as an example, position 1 is the compressor location, which constitutes the bleed air source for the coolant. Position 2 is the high-pressure turbine location, where the casing-type cooling structure is located. Based on the turbine casing surface at position 2, the annular radius of the casing is made larger than the outer radius of the turbine casing, and also larger than the minimum dimension for thin-shell processing and installation. Figure 3 As shown in the left figure, the length L of the gas casing along the engine axis depends on the location of the casing cooling requirements, such as... Figure 3 As shown in the figure on the right.

[0041] Design objectives: Determine the engine status and performance parameters for which cooling design will be carried out; determine the cooling design objectives based on factors such as the long-term required temperature limit of the casing material, the temperature requirements for strength and life, the temperature requirements for deformation, and the temperature limits of the engine's external walls (such as environmental requirements such as the temperature limit of the casing on the engine surface).

[0042] Selection of Cooling Air Source: In this application, the tip of a high-pressure compressor blade is generally selected as the bleed air location. The available air source pressure and temperature range are determined based on the bleed air location. For example, in this embodiment of the application, the bleed air location is the tip of the second-stage compressor blade. The pressure, temperature range, and other parameters of the air source are determined based on the location of the second-stage compressor blade tip. It should be noted that the pressure at the cooling bleed air location must be higher than the exhaust pressure of the gas-casing cooling structure, and the temperature must be lower than the average temperature of the turbine casing surface.

[0043] Step 2: Establish a heat transfer model for the air shell and assess the required heat.

[0044] like Figure 4The thermal balance system consisting of the gas casing 3, turbine casing 4, and main channel rotor 5 is shown. The thermal balance equation is established as follows:

[0045]

[0046] In the formula, Q lq The airflow designed for cooling needs to remove heat, Q hjdl To remove heat from the engine environment due to weak convection, Q jxfs Q represents the radiant heat from the casing to the gas shell. zzfs Radiated heat from the main channel rotor to the casing, Q jzdr Q is used to conduct heat to the engine stator blades mounted on the casing. zldl The main body of the strong convection heat to the casing, Q hjfs This refers to the radiated heat from the casing to the infinitely large external space.

[0047] The heat Qlq required to be removed for cooling is obtained by solving the heat balance equation.

[0048] For example Figure 5 The diagram illustrates the convective heat transfer model, where the convective heat transfer between the casing 4 and the cooling gas q satisfies Newton's law of cooling: Φ 3,q =αA3(T3-T q );

[0049] In the formula, Φ 3,q α is the convective heat transfer between casing 4 and cooling gas q; α is the heat transfer coefficient; A3 is the surface area of ​​casing 4; T3, T q These are the temperatures of casing 4 and cooling gas q, respectively.

[0050] The cooling radiation model can be modeled as a two-surface radiation heat transfer model:

[0051] In the formula, E b3 E bq These are the energy of the casing 4 and the cooling gas q itself; ε3 and ε q These are the emission rates of the casing 4 and the cooling gas q, respectively.

[0052] This leads to the required cooling capacity Q of the cooling gas. lq .

[0053] Step 3: Perform heat transfer design on the air shell to obtain the key parameters of the air shell cooling structure, namely the air shell height h and the air intake M.

[0054] Combining cooling design objectives and the required heat Q for cooling lq and the structural design constraints of the turbine casing,

[0055] For the convective heat transfer model of the airflow inside the casing 3 and the surface of the turbine casing 4, the convective heat transfer can be solved using the following typical empirical formulas:

[0056] The average Nusselt number Nu is obtained by integrating over the entire casing wall surface, and then the average heat transfer coefficient α is obtained:

[0057]

[0058] In the formula, Re and Pr are dimensionless parameters. ρ is density, u is velocity, d is characteristic length of the air shell, μ is dynamic viscosity, and c is density. p λ is the specific heat at constant pressure, A is the area of ​​the casing wall, R is the radius of the outer surface of the casing, and L is the length of the gas shell.

[0059] The solution yields the induced draft volume M and the shell height h.

[0060] Step 4: Performance evaluation.

[0061] Drawing high-pressure cold air from the compressor will result in a loss of overall engine performance. This step assesses the engine performance loss corresponding to the bleed air volume in step three. If the performance loss is beyond the allowable margin, return to step one.

[0062] In this embodiment, the exhaust pressure of the gas casing cavity is low, so there is no need for excessively high pressure of the cooling gas source. The bleed position obtained in step one is at the tip of the second stage blade of the compressor. The engine does less ineffective work, and the performance loss is within the margin range, which can meet the requirements.

[0063] Step 5: Flow design, including the organization of airflow paths and detailed flow design within the gas shell.

[0064] Organize the airflow path: With the goal of meeting the flow requirements, the aerodynamic parameters of the air intake and exhaust are the boundaries, and the principle of minimizing flow resistance loss is to design the airflow path.

[0065] Establish such as Figure 6 The fluid network shown and Figure 7 The diagram shows the airflow path 6. In the fluid network, chamber 1 is the compressor second-stage blade tip, chamber 4 is the casing exhaust boundary chamber, and the remaining chambers are locations with smaller flow cutoffs and larger geometric structures in the cold air flow. The throttling unit YQG consists of four long pipes with two 90° bends. The throttling unit BODY simulates the location within the casing layer where the space is narrower and the flow resistance is relatively high. The flow resistance unit PQG simulates the casing exhaust location.

[0066] Detailed design of flow within the casing: Based on the structural characteristics of the casing, ribs are designed for geometric locations prone to flow separation. The ribs guide the flow, increasing the heat exchange area of ​​the turbine casing and improving the flow rate of cold air on the turbine casing surface. Simultaneously, the turbulence caused by the ribs enhances the convective heat transfer capacity of the cold air, ultimately achieving highly efficient cooling.

[0067] In such Figure 7 In the schematic diagram of the airflow path shown, the turbine casing 4 has a groove 41. Due to its small size and manufacturing limitations, a gas shell layer cannot be built against the wall of the groove 41. The initially designed gas shell layer is enlarged so that it does not extend deep into the groove 41. Figure 8 As shown, in this structure, the airflow flows along streamline L1, which cannot effectively exchange heat with the bottom casing of the groove 41. In this application, a rib 31 is added at this location to improve the flow, allowing the airflow to flow along streamline L2. The added rib 31 improves the convective heat transfer capacity of the cold air, achieving efficient cooling.

[0068] Step Six: Assess the feasibility of the piping flow in Step Five. Structurally, it should be possible to draw air from the compressor casing opening and direct the airflow to the surface at position 2 via piping. If there are difficulties in implementing the piping layout, return to Step One, reselect the air source location, and redesign.

[0069] Finally, the above design method can be used to obtain a gas-shell cooling structure for turbine casing cooling.

[0070] Compared to traditional casing cooling design methods, the turbine casing gas shell cooling structure and its design method provided in this application are a systematic design approach. This method employs widely used convection and radiation heat transfer models, making it more practical. Several key parameters are proposed during the design process, which can serve as a data basis for adjusting the design and evaluating its effectiveness. This method can significantly improve design efficiency, shorten the design cycle, and reduce manpower and material costs.

[0071] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A design method for a turbine casing gas shell cooling structure, characterized in that, The method comprises: Step one, determining the design constraints and design targets of the turbine casing air casing cooling structure; Step two, establishing a heat balance equation according to the heat transfer model of the turbine casing air casing cooling structure, the turbine casing and the rotor, and evaluating the heat required to be taken away by the air casing cooling structure for turbine casing cooling; Step three, heat transfer design of the turbine casing air casing cooling structure, according to the design target, the heat required to be taken away and the turbine casing structure design constraints to obtain the key parameters of the turbine casing air casing cooling structure, including the air casing height and the bleed air quantity; Step four, evaluating the engine performance loss under the key parameters, if it meets the requirement, then proceed to the next step, if it does not meet the requirement, then return to step one; Step five, taking the flow demand of the turbine casing air casing cooling structure as the target, taking the aerodynamic parameters of the turbine casing air casing cooling structure bleed air and exhaust air as the boundary, and on the premise of meeting the flow resistance loss, the bleed air flow path of the turbine casing air casing cooling structure is designed; Step six, evaluating whether the bleed air flow path can be realized, if there is difficulty in pipeline arrangement, then return to step one to redesign until the requirement is met.

2. The turbine shroud air-casing cooling structure design method of claim 1, wherein In step one, the basic profile of the air casing cooling structure is determined according to the main structure of the turbine casing, so as to determine the design constraints of the turbine casing air casing cooling structure, wherein the annular radius of the turbine casing air casing cooling structure is greater than the outer radius of the turbine casing, and the length of the turbine casing air casing cooling structure along the engine axis depends on the cooling temperature reduction demand position of the casing.

3. The turbine shroud air-casing cooling structure design method of claim 1, wherein In step one, the design target is determined according to the long-term required temperature limit of the casing material, the temperature demand of the engine strength and service life, the temperature demand of the engine deformation and the temperature limit of the engine outer wall.

4. The turbine shroud air-casing cooling structure design method according to claim 2 or 3, characterized by, In step one, the turbine casing air casing cooling structure takes bleed air from the compressor blade tip, the compressor blade tip pressure at the bleed air position is higher than the exhaust pressure of the air casing cooling structure, and the compressor blade tip temperature at the bleed air position is lower than the average temperature of the turbine casing surface.

5. The turbine shroud air-casing cooling structure design method of claim 1, wherein In step two, the heat balance equation is: where Q lq is the heat carried away by the cooling air flow, hjdl is the heat carried away by the weak convection from the engine environment, jxfs is the heat radiated from the casing to the engine, zzfs is the heat radiated from the rotor to the casing, jzdr is the heat conducted from the engine stator blades mounted on the casing to the casing, zldl is the heat carried away by the strong convection from the main flow to the casing, and hjfs is the heat radiated from the casing to the infinite space.

6. The method of designing a turbine shroud air- casing cooling structure of claim 1, wherein, In step five, a bleed air flow fluid grid is first established to simulate the air flow characteristics of the bleed air flow path through the fluid grid.

7. The turbine shroud air-casing cooling structure design method of claim 6, wherein, In step five, the fluid grid comprises: A first cavity representing the bleed air position of the compressor blade tip; A second cavity representing the exhaust boundary of the air casing cooling structure; and At least two third cavities representing positions with small cross-sections and large geometric structures in the cold air flow path.

8. The turbine shroud air-casing cooling structure design method of claim 1, wherein, When the turbine casing outer surface has a groove, the air casing layer of the turbine casing air casing cooling structure does not enter the groove.

9. The turbine shroud air-casing cooling structure design method of claim 8, wherein, A rib plate is arranged on the air casing layer to extend into the groove to improve the air flow route.

10. A turbine casing air casing cooling structure, characterized by, The turbine casing air casing cooling structure is obtained by using the turbine casing air casing cooling structure design method according to any one of claims 1 to 9.

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