Flow thermal coupling calculation method in starting process of partial air inlet type turbine

Abstract

The invention discloses a flow thermal coupling calculation method in the starting process of a partial air inlet type turbine. The flow thermal coupling calculation method comprises the following steps: S1, establishing a three-dimensional model in which a fluid domain and a solid domain of an underwater turbine are conjugated; s2, performing grid division on the three-dimensional model; s3, establishing a numerical simulation calculation method, setting an initial condition of a fluid domain and a simulation calculation time step length, and forming a numerical simulation model; s4, establishing a combustion chamber model and an aircraft power system dynamic model by adopting a user-defined function; and S5, embedding the self-defined function into the model in the S3 to obtain the output torque of the turbine under a time step, substituting the output torque into the model in the S4 to obtain turbine parameters, updating boundary conditions, and carrying out calculation of a next time step until simulation time is met, so as to obtain temperature distribution of the turbine disc in the starting process. According to the flow-heat coupling calculation method, the problem of inaccurate flow-heat coupling simulation caused by quick change coupling of a plurality of physical quantities in the starting process of the underwater part air inlet type turbine is solved.

Description

Technical Field

[0001] This invention belongs to the field of engineering thermodynamics, specifically involving a flow-thermal coupling calculation method for the start-up process of a partially inlet turbine. Background Technology

[0002] Underwater torpedo propulsion systems are developing towards higher energy density and faster response. Partial-intake turbines, due to their compact structure and stable power output, have become core components of next-generation torpedo thermal propulsion systems. Unlike conventional full-circumferential intake turbines, some intake turbines only have inlet channels within a circumferential range of 30°-120°. While this design reduces rotational inertia and shortens start-up time, it also leads to severe asymmetry and intermittency in the working fluid flow. During start-up, high-temperature combustion gases rush into the flow channel at millisecond speeds, causing a sharp increase in transient heat flux density on the turbine blade surface. This results in unsteady heat transfer coupled with structural heat conduction, forming a complex fluid-thermal coupling process.

[0003] The start-up process of a turbine propulsion system can be divided into three stages: solid propellant combustion (0-2s), propellant-propellant mixed combustion (2-4s), and propellant-only combustion (after 4s). After the power unit ignites, the solid propellant combustion in the combustion chamber produces a large amount of gas, causing the temperature and pressure in the combustion chamber to rise rapidly. Simultaneously, the gas drives the turbine to rotate, powering the seawater pump and fuel pump. Seawater can displace fuel, allowing the fuel pump to better deliver liquid fuel to the combustion chamber. Successful ignition of the fuel depends on the temperature and pressure within the combustion chamber. Excessive temperature and pressure pose a risk of barrel explosion, while excessively low temperatures and pressures lead to ignition failure. After the liquid fuel enters the combustion chamber, it enters the propellant-propellant mixed combustion stage. At the end of solid propellant combustion, the gas produced suddenly disappears, significantly affecting the temperature and pressure within the combustion chamber. If the temperature and pressure drop too rapidly, it may cause the fuel to extinguish. Furthermore, the solid propellant occupies over 90% of the combustion chamber space. The increased gas filling space due to propellant combustion also impacts pressure and temperature, making these conditions more unpredictable. During startup, multiple physical quantities change rapidly and couple with each other, easily leading to startup failure. During the solid propellant combustion stage, the turbine speed is relatively slow, and the high-temperature gas (greater than 1800K) directly scours the blades, generating high thermal stress. After liquid fuel enters the combustion chamber, the gas temperature decreases, but the gas temperature generated by liquid fuel combustion still reaches as high as 1500K, exceeding the limits of the turbine materials. In experiments, changes in blade geometry and even breakage occurred, severely affecting turbine efficiency and safety. Therefore, it is crucial to analyze the hydrothermal coupling process of the turbine during startup. Since conducting turbine experiments with high-speed rotation, high-temperature and high-pressure environments, and supersonic flow is extremely difficult, simulation methods become an indispensable research tool.

[0004] Currently, numerous studies have been conducted in the field of turbomachinery both domestically and internationally on the flow and heat transfer characteristics of turbine blades based on the fluid-thermal coupling method. These studies primarily focus on fully circumferential inlet turbines, and are mostly conducted under stable operating conditions. Unlike fully circumferential inlet turbines operating under stable conditions, underwater turbines with partial inlet structures exhibit strong transient flow characteristics during startup. Furthermore, the temperature and pressure of the combustion gas are constantly changing and coupled with the turbine speed and output torque. Accurately predicting the turbine disk temperature using simulation methods requires considering the coupling of multiple physical quantities in the calculation. Existing fluid-thermal coupling simulation methods are not suitable for solving the startup process of underwater partially inlet turbines, as their calculation results do not involve the coupling of multiple physical quantities, leading to significant deviations from actual operating conditions. The accuracy of the temperature field solution for partially inlet turbines during startup directly affects whether the turbine can start successfully. Therefore, a high-precision, low-computational-cost numerical simulation method is needed to simulate the fluid-thermal coupling process during the startup of partially inlet turbines to obtain their startup characteristics. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the flow-thermal coupling during the startup process of a partially inlet turbine, which solves the problem of inaccurate flow-thermal coupling simulation caused by the rapid changes and coupling of multiple physical quantities during the startup process of an underwater partially inlet turbine.

[0006] The technical solution adopted in this invention is a flow-thermal coupling calculation method for the start-up process of a partially inlet turbine, comprising the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; S2. Mesh the 3D model; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met, and obtain the temperature distribution of the turbine disk during the startup process.

[0007] The invention is further characterized by: The specific process of S1 is as follows: Based on the parameters of the three-dimensional model of the underwater turbine in the actual project, the solid geometry is constructed using three-dimensional modeling software to obtain the solid domain solid model, and the fluid domain solid model is obtained by inverse solving, forming a three-dimensional model of the underwater turbine with conjugate fluid and solid domains.

[0008] The fluid domain in S1 includes the nozzle flow channel domain, rotor blade cascade domain, blade tip clearance domain, and axial clearance domain. The nozzle flow channel domain and axial clearance domain are both densified with O-type grids, the rotor blade cascade domain is densified with H-type blocks, and the nozzle flow domain is densified along the flow direction near the throat.

[0009] The specific process of S2 is as follows: the three-dimensional model is meshed using the multi-block structured mesh method.

[0010] The initial conditions in S3 include initial temperature, pressure, and initial temperature of the solid domain.

[0011] The specific process of S3 is as follows: Computational fluid dynamics simulation software is used to perform conjugate heat transfer simulations of the fluid and solid domains of a partial inlet turbine. The fluid and solid domains are solved simultaneously. The turbulence equations are solved in the fluid domain, and the three-dimensional, transient, constant-property, heat conduction equations without internal heat sources are solved in the solid domain. The density, specific heat, and thermal conductivity of the solid domain material were obtained from the material handbook. Radiation heat transfer was not considered, but convective heat transfer existed between the turbine disk and the flow channel. The inlet of the computational domain was a pressure inlet, and the total temperature and pressure were the actual inlet total temperature and pressure. Initial values ​​were set before the simulation and then provided by a user-defined function in S4 after the simulation started. The outlet was a pressure outlet, and the static pressure was the actual outlet static pressure. A 3D unsteady pressure-based solver with double precision was used, employing the SIMPLEC algorithm. The combustion gas was an ideal compressible gas, and the k-ωSST model was used for the turbulence model. The walls coupling the fluid and solid domains were set as coupled boundaries. Initial wall temperatures were set and the walls were set as moving walls. A sliding mesh method was used, and the rotational speed was provided by a user-defined function in S4. No-slip adiabatic boundary conditions were set for other walls. The initial temperature and pressure of the fluid domain were set to the actual outlet temperature and pressure, and the temperature of the solid domain was set to the actual outlet temperature.

[0012] The specific process of S4: S4.1 Using the macros in the user-defined function manual of the computational fluid dynamics simulation software, set the user-defined function to work after each calculation time step, establish the combustion chamber model according to the actual working process of the combustion chamber, and calculate the combustion chamber pressure through formulas (1)-(6): (1); (2); (3); (4); (5); (6); In the formula, The amount of gas produced per unit time. The density of the solid propellant column. This represents the surface area of ​​the solid propellant grain. The combustion rate of the solid propellant column. For the gearbox ratio, For fuel pump displacement, Let k be the turbine speed at time k. This refers to the gas consumption per unit time. This represents the area of ​​the nozzle throat. For specific heat ratio, The gas constant is The combustion chamber temperature, Let K be the combustion chamber pressure at time k. This represents the change in gas mass flow rate. Let the mass of the gas at time k+1 be... Let K be the mass of the gas at time k. The time step for numerical simulation calculations. Let K be the free volume of the combustion chamber at time k+1. For startup duration, Let K be the free volume of the combustion chamber at time k. The volume of the combustion chamber. Let K be the combustion chamber pressure at time k+1; S4.2 Establish the dynamic model of the aircraft's propulsion system, use the functions in the user-defined function manual to obtain the turbine output torque in the numerical simulation calculation, and calculate the turbine speed through formulas (7)-(14): (7); (8); (9); (10); (11); (12); (13); (14); In the formula, To absorb torque for the aircraft's propulsion system, It is a positive constant. To absorb torque for the seawater pump, It is a positive constant. To absorb torque for the lubricating oil pump, It is a positive constant. To absorb torque for the generator, It is a positive constant. To absorb torque for the fuel pump, It is a positive constant. The pressure difference across the fuel pump. The swashplate angle of the fuel pump. This is to compensate for the pressure displaced by the fuel tank. For the resistance torque of the power system, Let k+1 be the turbine speed. To provide torque for the turbine output, The reduced moment of inertia of the underwater vehicle's propulsion system; S4.3 Utilize the macro definitions in the manual to perform numerical simulation calculations, including the total temperature and pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region.

[0013] The specific process of S5 is as follows: The user-defined function is compiled and loaded into the numerical simulation model set in the computational fluid dynamics simulation software. The macro written in S4 is set to the corresponding boundary conditions and parameters, including the total temperature and pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region. Conjugate heat transfer numerical calculation is performed. After each calculation time step, the user-defined function program automatically obtains the turbine torque. Based on the combustion chamber model and the dynamic model of the aircraft power system established in S4, the combustion chamber pressure, temperature, and turbine speed are calculated, and the boundary conditions and parameters in the numerical model are updated. The calculation of the next time step is performed until the simulation time is met, and the temperature distribution of the turbine disk during the start-up process of a partial intake turbine is obtained.

[0014] The beneficial effects of this invention are: The present invention provides a flow-thermal coupling calculation method for the startup process of a partially inlet turbine. Based on the simulation results, the performance of the turbine during startup can be obtained. It is applicable to underwater partially inlet axial impulse turbine engines and provides intuitive data support for the startup characteristics of partially inlet turbines. It can effectively solve the impact of rapid changes in multiple physical quantities during startup on the flow-thermal coupling simulation of the turbine, and can also determine the reliability of the turbine disk during startup. Attached Figure Description Figure 1 This is a flowchart of the flow-thermal coupling calculation method for part of the inlet turbine startup process according to the present invention; Figure 2 This is a partial inlet turbine fluid domain model diagram from Embodiment 6 of the present invention; Figure 3 This is a partial solid domain model diagram of an air intake turbine in Embodiment 6 of the present invention.

[0015] In the figure, 1. Gas inlet, 2. Nozzle, 3. Rotor, 4. Blade tip clearance, 5. Axial clearance, 6. Blade, 7. Surrounding belt, 8. Disc surface, 9. Shaft surface, 10. End face. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] Example 1 The flow-thermal coupling calculation method for the startup process of a partially inlet turbine proposed in this embodiment, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; S2. Mesh the 3D model; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met, and obtain the temperature distribution of the turbine disk during the startup process.

[0018] Example 2 The flow-thermal coupling calculation method for the startup process of a partially inlet turbine proposed in this embodiment, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; The specific process is as follows: Based on the three-dimensional model parameters of the underwater turbine in the actual project, the solid geometry is constructed using three-dimensional modeling software to obtain the solid domain solid model, and the fluid domain solid model is solved in reverse to form a three-dimensional model of the underwater turbine with conjugate fluid and solid domains. The fluid domain includes the nozzle flow channel domain, rotor blade cascade domain, blade tip clearance domain, and axial clearance domain. The nozzle flow channel domain and axial clearance domain are both densified with O-type grids, the rotor blade cascade domain is densified with H-type blocks, and the nozzle flow domain is densified along the flow direction near the throat. S2. Mesh the 3D model; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met, and obtain the temperature distribution of the turbine disk during the startup process.

[0019] Example 3 The flow-thermal coupling calculation method for the startup process of a partially inlet turbine proposed in this embodiment, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; The specific process is as follows: Based on the three-dimensional model parameters of the underwater turbine in the actual project, the solid geometry is constructed using three-dimensional modeling software to obtain the solid domain solid model, and the fluid domain solid model is solved in reverse to form a three-dimensional model of the underwater turbine with conjugate fluid and solid domains. The fluid domain includes the nozzle flow channel domain, rotor blade cascade domain, blade tip clearance domain, and axial clearance domain. The nozzle flow channel domain and axial clearance domain are both densified with O-type grids, the rotor blade cascade domain is densified with H-type blocks, and the nozzle flow domain is densified along the flow direction near the throat. S2. Mesh the 3D model; The specific process is as follows: the three-dimensional model is meshed using a multi-block structured meshing method; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; Initial conditions include initial temperature, pressure, and initial temperature of the solid domain; Specific process: Computational fluid dynamics simulation software is used to perform conjugate heat transfer simulations of the fluid and solid domains of a partial inlet turbine. The fluid and solid domains are solved simultaneously. The turbulence equations are solved in the fluid domain, and the three-dimensional, transient, constant-property, heat conduction equations without internal heat sources are solved in the solid domain. The density, specific heat, and thermal conductivity of the solid domain material were obtained from the material handbook. Radiation heat transfer was not considered. Convective heat transfer existed between the turbine disk and the flow channel. The inlet of the computational domain was a pressure inlet, and the total temperature and pressure were the actual inlet total temperature and pressure. Initial values ​​were set before the simulation and then provided by a user-defined function in S4 after the simulation started. The outlet was a pressure outlet, and the static pressure was the actual outlet static pressure. A 3D unsteady pressure-based solver with double precision was used, employing the SIMPLEC algorithm. The combustion gas was an ideal compressible gas, and the k-ωSST model was used for the turbulence model. The walls of the fluid and solid domains were set as coupled boundaries. The initial wall temperatures were set and the walls were set as moving walls. The sliding mesh method was used, and the rotational speed was provided by a user-defined function in S4. No-slip adiabatic boundary conditions were set for other walls. The initial temperature and pressure of the fluid domain were set to the actual outlet temperature and pressure, and the temperature of the solid domain was set to the actual outlet temperature. S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met, and obtain the temperature distribution of the turbine disk during the startup process.

[0020] Example 4 The flow-thermal coupling calculation method for the startup process of a partially inlet turbine proposed in this embodiment, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; The specific process is as follows: Based on the three-dimensional model parameters of the underwater turbine in the actual project, the solid geometry is constructed using three-dimensional modeling software to obtain the solid domain solid model, and the fluid domain solid model is solved in reverse to form a three-dimensional model of the underwater turbine with conjugate fluid and solid domains. The fluid domain includes the nozzle flow channel domain, rotor blade cascade domain, blade tip clearance domain, and axial clearance domain. The nozzle flow channel domain and axial clearance domain are both densified with O-type grids, the rotor blade cascade domain is densified with H-type blocks, and the nozzle flow domain is densified along the flow direction near the throat. S2. Mesh the 3D model; The specific process is as follows: the three-dimensional model is meshed using a multi-block structured meshing method; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; Initial conditions include initial temperature, pressure, and initial temperature of the solid domain; Specific process: Computational fluid dynamics simulation software is used to perform conjugate heat transfer simulations of the fluid and solid domains of a partial inlet turbine. The fluid and solid domains are solved simultaneously. The turbulence equations are solved in the fluid domain, and the three-dimensional, transient, constant-property, heat conduction equations without internal heat sources are solved in the solid domain. The density, specific heat, and thermal conductivity of the solid domain material were obtained from the material handbook. Radiation heat transfer was not considered. Convective heat transfer existed between the turbine disk and the flow channel. The inlet of the computational domain was a pressure inlet, and the total temperature and pressure were the actual inlet total temperature and pressure. Initial values ​​were set before the simulation and then provided by a user-defined function in S4 after the simulation started. The outlet was a pressure outlet, and the static pressure was the actual outlet static pressure. A 3D unsteady pressure-based solver with double precision was used, employing the SIMPLEC algorithm. The combustion gas was an ideal compressible gas, and the k-ωSST model was used for the turbulence model. The walls of the fluid and solid domains were set as coupled boundaries. The initial wall temperatures were set and the walls were set as moving walls. The sliding mesh method was used, and the rotational speed was provided by a user-defined function in S4. No-slip adiabatic boundary conditions were set for other walls. The initial temperature and pressure of the fluid domain were set to the actual outlet temperature and pressure, and the temperature of the solid domain was set to the actual outlet temperature. S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; Specific process: S4.1 Using the macros in the user-defined function manual of the computational fluid dynamics simulation software, set the user-defined function to work after each calculation time step, establish the combustion chamber model according to the actual working process of the combustion chamber, and calculate the combustion chamber pressure through formulas (1)-(6): (1); (2); (3); (4); (5); (6); In the formula, The amount of gas produced per unit time. The density of the solid propellant column. This represents the surface area of ​​the solid propellant grain. The combustion rate of the solid propellant column. For the gearbox ratio, For fuel pump displacement, Let k be the turbine speed at time k. This refers to the gas consumption per unit time. This represents the area of ​​the nozzle throat. For specific heat ratio, The gas constant is The combustion chamber temperature, Let K be the combustion chamber pressure at time k. This represents the change in gas mass flow rate. Let the mass of the gas at time k+1 be... Let K be the mass of the gas at time k. The time step for numerical simulation calculations. Let K be the free volume of the combustion chamber at time k+1. For startup duration, Let K be the free volume of the combustion chamber at time k. The volume of the combustion chamber. Let K be the combustion chamber pressure at time k+1; S4.2 Establish the dynamic model of the aircraft's propulsion system, use the functions in the user-defined function manual to obtain the turbine output torque in the numerical simulation calculation, and calculate the turbine speed through formulas (7)-(14): (7); (8); (9); (10); (11); (12); (13); (14); In the formula, To absorb torque for the aircraft's propulsion system, It is a positive constant. To absorb torque for the seawater pump, It is a positive constant. To absorb torque for the lubricating oil pump, It is a positive constant. To absorb torque for the generator, It is a positive constant. To absorb torque for the fuel pump, It is a positive constant. The pressure difference across the fuel pump. The swashplate angle of the fuel pump. This is to compensate for the pressure displaced by the fuel tank. For the resistance torque of the power system, Let k+1 be the turbine speed. To provide torque for the turbine output, The reduced moment of inertia of the underwater vehicle's propulsion system; S4.3 Utilize the boundary conditions and parameter settings in the numerical simulation calculations using the macro definitions in the manual, including the total temperature and total pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met, and obtain the temperature distribution of the turbine disk during the startup process.

[0021] Example 5 The flow-thermal coupling calculation method for the startup process of a partially inlet turbine proposed in this embodiment, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; The specific process is as follows: Based on the three-dimensional model parameters of the underwater turbine in the actual project, the solid geometry is constructed using three-dimensional modeling software to obtain the solid domain solid model, and the fluid domain solid model is solved in reverse to form a three-dimensional model of the underwater turbine with conjugate fluid and solid domains. The fluid domain includes the nozzle flow channel domain, rotor blade cascade domain, blade tip clearance domain, and axial clearance domain. The nozzle flow channel domain and axial clearance domain are both densified with O-type grids, the rotor blade cascade domain is densified with H-type blocks, and the nozzle flow domain is densified along the flow direction near the throat. S2. Mesh the 3D model; The specific process is as follows: the three-dimensional model is meshed using a multi-block structured meshing method; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; Initial conditions include initial temperature, pressure, and initial temperature of the solid domain; Specific process: Computational fluid dynamics simulation software is used to perform conjugate heat transfer simulations of the fluid and solid domains of a partial inlet turbine. The fluid and solid domains are solved simultaneously. The turbulence equations are solved in the fluid domain, and the three-dimensional, transient, constant-property, heat conduction equations without internal heat sources are solved in the solid domain. The density, specific heat, and thermal conductivity of the solid domain material were obtained from the material handbook. Radiation heat transfer was not considered. Convective heat transfer existed between the turbine disk and the flow channel. The inlet of the computational domain was a pressure inlet, and the total temperature and pressure were the actual inlet total temperature and pressure. Initial values ​​were set before the simulation and then provided by a user-defined function in S4 after the simulation started. The outlet was a pressure outlet, and the static pressure was the actual outlet static pressure. A 3D unsteady pressure-based solver with double precision was used, employing the SIMPLEC algorithm. The combustion gas was an ideal compressible gas, and the k-ωSST model was used for the turbulence model. The walls of the fluid and solid domains were set as coupled boundaries. The initial wall temperatures were set and the walls were set as moving walls. The sliding mesh method was used, and the rotational speed was provided by a user-defined function in S4. No-slip adiabatic boundary conditions were set for other walls. The initial temperature and pressure of the fluid domain were set to the actual outlet temperature and pressure, and the temperature of the solid domain was set to the actual outlet temperature. S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; Specific process: S4.1 Using the macros in the user-defined function manual of the computational fluid dynamics simulation software, set the user-defined function to work after each calculation time step, establish the combustion chamber model according to the actual working process of the combustion chamber, and calculate the combustion chamber pressure through formulas (1)-(6): (1); (2); (3); (4); (5); (6); In the formula, The amount of gas produced per unit time. The density of the solid propellant column. This represents the surface area of ​​the solid propellant grain. The combustion rate of the solid propellant column. For the gearbox ratio, For fuel pump displacement, Let k be the turbine speed at time k. This refers to the gas consumption per unit time. This represents the area of ​​the nozzle throat. For specific heat ratio, The gas constant is The combustion chamber temperature, Let K be the combustion chamber pressure at time k. This represents the change in gas mass flow rate. Let the mass of the gas at time k+1 be... Let K be the mass of the gas at time k. The time step for numerical simulation calculations. Let K be the free volume of the combustion chamber at time k+1. For startup duration, Let K be the free volume of the combustion chamber at time k. The volume of the combustion chamber. Let K be the combustion chamber pressure at time k+1; S4.2 Establish the dynamic model of the aircraft's propulsion system, use the functions in the user-defined function manual to obtain the turbine output torque in the numerical simulation calculation, and calculate the turbine speed through formulas (7)-(14): (7); (8); (9); (10); (11); (12); (13); (14); In the formula, To absorb torque for the aircraft's propulsion system, It is a positive constant. To absorb torque for the seawater pump, It is a positive constant. To absorb torque for the lubricating oil pump, It is a positive constant. To absorb torque for the generator, It is a positive constant. To absorb torque for the fuel pump, It is a positive constant. The pressure difference across the fuel pump. The swashplate angle of the fuel pump. This is to compensate for the pressure displaced by the fuel tank. For the resistance torque of the power system, Let k+1 be the turbine speed. To provide torque for the turbine output, The reduced moment of inertia of the underwater vehicle's propulsion system; S4.3 Utilize the boundary conditions and parameter settings in the numerical simulation calculations using the macro definitions in the manual, including the total temperature and total pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met to obtain the temperature distribution of the turbine disk during the startup process. The specific process is as follows: The user-defined function is compiled and loaded into the numerical simulation model set in the computational fluid dynamics simulation software. The macro written in S4 is set to the corresponding boundary conditions and parameters, including the total temperature and pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region. Conjugate heat transfer numerical calculations are performed. After each calculation time step, the user-defined function program automatically obtains the turbine torque. Based on the combustion chamber model and the dynamic model of the aircraft power system established in S4, the combustion chamber pressure, temperature, and turbine speed are calculated, and the boundary conditions and parameters in the numerical model are updated. The calculation for the next time step is then performed until the simulation time is met, and the temperature distribution of the turbine disk during the start-up process of a partial intake turbine is obtained.

[0022] Example 6 The flow-thermal coupling calculation method for the startup process of a partially inlet turbine proposed in this embodiment, such as... Figure 1 As shown, it includes the following steps: S1. Establish a three-dimensional model of the conjugate fluid and solid domains of the underwater turbine. The specific process is as follows: Based on the parameters of the three-dimensional model of the underwater turbine in the actual project, construct the solid geometry using three-dimensional modeling software to obtain the solid domain solid model, and then solve the fluid domain solid model to form a three-dimensional model of the conjugate fluid and solid domains of the underwater turbine. For convenience, the fluid domain of the 3D model is divided into the nozzle flow channel domain, rotor blade cascade domain, blade tip clearance domain, and axial clearance domain. The fluid domain model is as follows: Figure 2 As shown, the fluid domain model consists of four parts: nozzle 2, rotor 3, blade tip clearance 4, and axial clearance 5. Axial clearance 5 is the gap between the disk surface 8 and the turbine casing in the solid domain. Axial clearance 5 is caused by gas leakage at the nozzle 2 outlet. Blade tip clearance 4 is the gap between the shroud 7 and the turbine casing in the solid domain. Blade tip clearance 4 is caused by gas leakage entering the rotor 3. The air intake structure of the underwater turbine allows nozzle 2 to be installed on a part of the arc. The front end of nozzle 2 is the gas inlet 1, and the nozzle outlet faces the rotor 3. underwater turbine solid domain model as follows Figure 3 As shown, it includes a wheel disk surface 8, multiple blades 6 are evenly installed on the edge of the wheel disk, multiple blades 6 are wrapped with a shroud 7, and there is a hub in the middle of the rear of the wheel disk. The circumferential surface of the hub is the axial surface 9, and the surface of the hub that needs to be fixed is the end surface 10. Except for the axial surface 9 and the end surface 10, the other surfaces are coupling surfaces of the solid domain. The surfaces in the fluid domain that correspond to the coupling surfaces of the solid domain are coupling surfaces of the fluid domain. S2. The 3D model is meshed using a multi-block structured meshing method. A hexahedral structured mesh is used across the entire computational domain. A boundary layer is required near the wall. O-type meshes are more effective for refining the flow in the rotary flow domain, better capturing flow details near the wall. Therefore, O-type meshes are used for refining the nozzle and axial clearance flow domains, while H-type blocks are used at the rotor blade cascade. To accurately obtain flow information at the throat, refining is applied along the flow direction near the throat. Due to leakage of high-speed gas ejected from the nozzle at the shroud, resulting in tip clearance loss, C-type blocks are used at the shroud to accurately correspond to the toothed seal, achieving accurate refining at the tip clearance. Mesh correspondence between the solid and fluid domains should also be ensured to improve the convergence of coupled calculations. The mesh node error between the solid and fluid domains should be within 0.01 mm. S3. Using computational fluid dynamics simulation software, a numerical simulation method for supersonic flow fields and fluid-solid conjugate heat transfer is established. Initial temperatures and pressures in the fluid domain and initial temperatures in the solid domain of a partially inlet turbine are set, along with the simulation time step. Specifically, conjugate heat transfer simulations are performed on the fluid and solid domains of the partially inlet turbine. Both domains are solved simultaneously. Turbulence equations are solved in the fluid domain, and three-dimensional, transient, constant-property, heat conduction equations without internal heat sources are solved in the solid domain. The density, specific heat, and thermal conductivity of the solid domain material were obtained from the material handbook. Radiation heat transfer was not considered. Convective heat transfer existed between the turbine disk and the flow channel. The inlet of the computational domain was a pressure inlet, and the total temperature and pressure were the actual inlet total temperature and pressure. Initial values ​​were set before the simulation and then provided by a user-defined function in S4 after the simulation started. The outlet was a pressure outlet, and the static pressure was the actual outlet static pressure. A 3D unsteady pressure-based solver with double precision was used, employing the SIMPLEC algorithm. The combustion gas was an ideal compressible gas, and the k-ωSST model was used for the turbulence model. The walls of the fluid and solid domains were set as coupled boundaries. An initial wall temperature was set and the walls were set as moving walls. The sliding mesh method was used, and the rotational speed was provided by a user-defined function in S4. No-slip adiabatic boundary conditions were set for other walls. The initial temperature and pressure of the fluid domain were set to the actual outlet temperature and pressure, and the temperature of the solid domain was set to the actual outlet temperature. S4. Establish the combustion chamber model and the vehicle's propulsion system dynamics model using user-defined functions. The specific process is as follows: Utilize the macros in the user-defined function manual of the computational fluid dynamics simulation software to set the user-defined function to run after each calculation time step. Establish the combustion chamber model based on the actual working process of the combustion chamber, and calculate the combustion chamber pressure using the following formula: (1); (2); (3); (4); (5); (6); In the formula, The amount of gas produced per unit time. The density of the solid propellant column. This represents the surface area of ​​the solid propellant grain. The combustion rate of the solid propellant column. For the gearbox ratio, For fuel pump displacement, Let k be the turbine speed at time k. This refers to the gas consumption per unit time. This represents the area of ​​the nozzle throat. For specific heat ratio, The gas constant is The combustion chamber temperature, Let K be the combustion chamber pressure at time k. This represents the change in gas mass flow rate. Let the mass of the gas at time k+1 be... Let K be the mass of the gas at time k. The time step for numerical simulation calculations. Let K be the free volume of the combustion chamber at time k+1. For startup duration, Let K be the free volume of the combustion chamber at time k. The volume of the combustion chamber. Let K be the combustion chamber pressure at time k+1; A dynamic model of the aircraft's propulsion system is established. The output torque of the turbine in the numerical simulation is obtained using functions from the user-defined function manual. The turbine speed is then calculated using the following formula: (7); (8); (9); (10); (11); (12); (13); (14); In the formula, To absorb torque for the aircraft's propulsion system, It is a positive constant. To absorb torque for the seawater pump, It is a positive constant. To absorb torque for the lubricating oil pump, It is a positive constant. To absorb torque for the generator, It is a positive constant. To absorb torque for the fuel pump, It is a positive constant. The pressure difference across the fuel pump. The swashplate angle of the fuel pump. This is to compensate for the pressure displaced by the fuel tank. For the resistance torque of the power system, Let k+1 be the turbine speed. To provide torque for the turbine output, This is the reduced moment of inertia of the underwater vehicle's propulsion system.

[0023] The boundary conditions and parameter settings in the numerical simulation calculations using macro definitions in the manual include the total temperature and total pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region. S5. Embedding the user-defined function into the numerical simulation model, performing conjugate heat transfer numerical simulation on the computational domain, obtaining the turbine output torque at one time step, and substituting it into the model established in S4 to obtain the combustion chamber temperature, pressure, and turbine speed. Returning the results to the numerical simulation calculation to update boundary conditions, and continuing the calculation for the next time step until the simulation time is met, yielding the temperature distribution of the turbine disk during the startup process of a partial inlet turbine. Specifically, the user-defined function is compiled and loaded into the numerical simulation model set within the computational fluid dynamics simulation software. The macros written in S4 are set to the corresponding boundary conditions and parameters, including the total temperature and pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region. Conjugate heat transfer numerical calculations are performed. After each calculation time step, the user-defined function program automatically obtains the turbine torque, calculates the combustion chamber pressure, temperature, and turbine speed based on the combustion chamber model and the vehicle propulsion system dynamics model established in S4, updates the boundary conditions and parameters in the numerical model, and continues the calculation for the next time step until the simulation time is met, yielding the temperature distribution of the turbine disk during the startup process of a partial inlet turbine.

[0024] This invention establishes a three-dimensional model of an underwater partially inlet turbine to create a model identical to that of an actual underwater partially inlet turbine. This provides a realistic and effective model to address the impact of rapid changes in various physical quantities during startup on the turbine's fluid-thermal coupling simulation, enabling accurate calculation of the fluid-thermal coupling results during startup. The use of a multi-partition structured mesh method to divide the three-dimensional model aims to solve the governing equations using the finite volume method, accurately determining the temperature distribution at the turbine's fluid-structure interaction surface during fluid-thermal coupling. The establishment of a numerical simulation method for conjugate heat transfer between the fluid and solid domains is intended to better simulate the flow conditions in the fluid domain, the convective heat transfer between the fluid and solid domains, and the thermal conductivity in the solid domain. This allows for accurate calculation of the flow field results in the turbine's fluid domain and solid domain during fluid-thermal coupling. The temperature distribution; using user-defined functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system is to better simulate the actual start-up process of a partially inlet turbine, accurately calculate the changes in various physical quantities, and provide precise boundary conditions and parameter settings for the numerical simulation of conjugate heat transfer during turbine start-up; embedding user-defined functions into the numerical model of conjugate heat transfer during turbine start-up is to better simulate the changes in fluid temperature, pressure, and turbine disk speed during turbine start-up, and accurately solve the flow field and turbine disk temperature distribution in the fluid domain under the rapid coupling of multiple physical quantities during turbine start-up. Thus, the fluid-thermal coupling of the partially inlet turbine start-up process is completed, and the reliability of the turbine disk during start-up can be judged based on the turbine disk temperature distribution at this time.

[0025] Through the above methods, the flow-thermal coupling calculation method for the startup process of a partially inlet turbine of the present invention can obtain the turbine performance during the startup process based on the simulation results data. It is applicable to underwater partially inlet axial impulse turbine engines, provides intuitive data support for the startup characteristics of partially inlet turbines, can better solve the impact of rapid changes in multiple physical quantities during startup on the flow-thermal coupling simulation of turbines, and can determine the reliability of the turbine disk during startup.

Claims

1. A method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine, characterized in that, Includes the following steps: S1. Establish a three-dimensional model of the underwater turbine with conjugate fluid and solid domains; S2. Mesh the 3D model; S3. Establish a numerical simulation calculation method, set the initial conditions of the fluid domain and the simulation calculation time step, and form a numerical simulation model; S4. Use custom functions to establish the combustion chamber model and the dynamic model of the aircraft's propulsion system; S5. Embed the custom function into the S3 model to obtain the turbine output torque at one time step. Substitute it into the S4 model to obtain the turbine parameters, update the boundary conditions, and perform the next time step calculation until the simulation time is met, and obtain the temperature distribution of the turbine disk during the startup process.

2. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The specific process of S1 is as follows: based on the three-dimensional model parameters of the underwater turbine in the actual project, the solid geometry is constructed using three-dimensional modeling software to obtain the solid domain solid model, and the fluid domain solid model is deduced from the inverse solution to form a three-dimensional model of the underwater turbine fluid domain and solid domain conjugate.

3. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The fluid domain described in S1 includes the nozzle flow channel domain, the rotor blade cascade domain, the blade tip clearance domain, and the axial clearance domain. The nozzle flow channel domain and the axial clearance domain are both densified using O-type grids, the rotor blade cascade domain is densified using H-type blocks, and the nozzle flow domain is densified along the flow direction near the throat.

4. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The specific process of S2 is as follows: the three-dimensional model is divided into meshes using a multi-block structured mesh method.

5. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The initial conditions described in S3 include initial temperature, pressure, and initial temperature of the solid domain.

6. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The specific process of S3 is as follows: Computational fluid dynamics simulation software is used to perform conjugate heat transfer simulations of the fluid and solid domains of a partial intake turbine. The fluid and solid domains are solved simultaneously. The turbulence equations are solved in the fluid domain, and the three-dimensional, transient, constant-property, heat conduction equations without internal heat sources are solved in the solid domain. The density, specific heat, and thermal conductivity of the solid domain material were obtained from the material handbook. Radiation heat transfer was not considered, but convective heat transfer existed between the turbine disk and the flow channel. The inlet of the computational domain was a pressure inlet, and the total temperature and pressure were the actual inlet total temperature and pressure. Initial values ​​were set before the simulation and then provided by a user-defined function in S4 after the simulation started. The outlet was a pressure outlet, and the static pressure was the actual outlet static pressure. A 3D unsteady pressure-based solver with double precision was used, employing the SIMPLEC algorithm. The combustion gas was an ideal compressible gas, and the k-ωSST model was used for the turbulence model. The walls coupling the fluid and solid domains were set as coupled boundaries. Initial wall temperatures were set and the walls were set as moving walls. A sliding mesh method was used, and the rotational speed was provided by a user-defined function in S4. No-slip adiabatic boundary conditions were set for other walls. The initial temperature and pressure of the fluid domain were set to the actual outlet temperature and pressure, and the temperature of the solid domain was set to the actual outlet temperature.

7. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The specific process of S4 is as follows: S4.1 Using the macros in the user-defined function manual of the computational fluid dynamics simulation software, set the user-defined function to work after each calculation time step, establish the combustion chamber model according to the actual working process of the combustion chamber, and calculate the combustion chamber pressure through formulas (1)-(6): （1）； （2）； （3）； （4）； （5）； （6）； In the formula, The amount of gas produced per unit time. The density of the solid propellant column. This represents the surface area of ​​the solid propellant grain. The combustion rate of the solid propellant column. For the gearbox ratio, For fuel pump displacement, Let k be the turbine speed at time k. This refers to the gas consumption per unit time. This represents the area of ​​the nozzle throat. For specific heat ratio, The gas constant is The combustion chamber temperature, Let K be the combustion chamber pressure at time k. This represents the change in gas mass flow rate. Let the mass of the gas be at time k+1. Let K be the mass of the gas at time k. The time step for numerical simulation calculations. Let K be the free volume of the combustion chamber at time k+1. For startup duration, Let K be the free volume of the combustion chamber at time k. The volume of the combustion chamber. Let K be the combustion chamber pressure at time k+1; S4.2 Establish the dynamic model of the aircraft's propulsion system, use the functions in the user-defined function manual to obtain the turbine output torque in the numerical simulation calculation, and calculate the turbine speed through formulas (7)-(14): （7）； （8）； （9）； （10）； （11）； （12）； （13）； （14）； In the formula, To absorb torque for the aircraft's propulsion system, It is a positive constant. To absorb torque for the seawater pump, It is a positive constant. To absorb torque for the lubricating oil pump, It is a positive constant. To absorb torque for the generator, It is a positive constant. To absorb torque for the fuel pump, It is a positive constant. The pressure difference across the fuel pump. The swashplate angle of the fuel pump. This is to compensate for the pressure displaced by the fuel tank. For the resistance torque of the power system, Let k+1 be the turbine speed. To provide torque for the turbine output, The reduced moment of inertia of the underwater vehicle's propulsion system; S4.3 Utilize the macro definitions in the manual to perform numerical simulation calculations, including the total temperature and pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region.

8. The method for calculating the flow-thermal coupling during the start-up process of a partially inlet turbine according to claim 1, characterized in that, The specific process of S5 is as follows: The user-defined function is compiled and loaded into the numerical simulation model set in the computational fluid dynamics simulation software. The macro written in S4 is set to the corresponding boundary conditions and parameters, including the total temperature and pressure at the pressure inlet, the rotational speed of the rotating wall, and the rotational speed of the rotating region. Conjugate heat transfer numerical calculation is performed. After each calculation time step, the user-defined function program automatically obtains the turbine torque. Based on the combustion chamber model and the dynamic model of the aircraft power system established in S4, the combustion chamber pressure, temperature, and turbine speed are calculated, and the boundary conditions and parameters in the numerical model are updated. The calculation of the next time step is performed until the simulation time is met, and the temperature distribution of the turbine disk during the start-up process of a partial intake turbine is obtained.

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