Transient measurement method and system for surface heat transfer coefficient in rotating disc cavity

Abstract

The invention relates to a transient measurement method and system for a surface heat transfer coefficient in a rotating disc cavity, and belongs to an aero-engine air system technology. The method comprises the steps that the disc cavity gap ratio of the rotor-stator disc cavity structure is designed, the rotor-stator disc cavity structure with the increased disc cavity gap is obtained, and the flow characteristic in a disc cavity of the structure conforms to the flow characteristic of a free disc; a pressure measuring point and a temperature measuring point are arranged on the rotor-stator disc cavity structure with the increased disc cavity gap; working conditions conforming to free disc flow heat exchange characteristics are calculated; performing a transient heat exchange experiment based on the calculated working condition; and calculating the heat transfer temperature in the rotating disc cavity based on the data acquired by the measuring points in the experiment, and obtaining the surface heat transfer coefficient in the rotating disc cavity according to a surface heat transfer coefficient transient measurement method. According to the invention, the accuracy verification problem of the transient measurement method for the surface heat transfer coefficient in the rotating disc cavity is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation engine air systems, and in particular relates to a method and system for transient measurement of surface heat transfer coefficient in a rotating disk cavity. Background Art

[0002] The surface heat transfer coefficient and Nusselt number distribution of structures such as rotating disks in aircraft engine turbine components have always been the research focus of domestic and foreign technicians. The measurement technology of the surface heat transfer coefficient of the rotating disk of the aircraft engine rotating disk cavity is one of the current technical bottlenecks in the thermal analysis and refinement of the rotating disk cavity.

[0003] At present, the transient method is mostly used to measure the heat transfer coefficient of the turntable surface in the heat exchange experiment of the rotating disk cavity. The specific process of the transient method in the heat exchange experiment is to suddenly reduce or increase the inlet airflow temperature of the test piece under the conditions of ensuring the stability of the airflow field and the speed of the test piece and reaching thermal equilibrium, so as to achieve heat exchange between the airflow and the rotor; during the experiment, the turntable wall temperature and the heat exchange temperature are measured, and the surface heat transfer coefficient is obtained by analyzing the temperature change rate over time. However, the existing transient method accuracy verification technology only stays in the heat exchange experiment of flat plate heat exchange and heat exchange experiments such as turntable heat exchange, and the verification of the measurement method of the transient heat transfer coefficient of the rotating disk cavity is still insufficient.

[0004] Therefore, the present invention proposes a large cavity width structure rotating static disk cavity test bench and verification method. The main contents are: under applicable conditions, in the large cavity width structure rotating static disk cavity flow heat transfer experiment, the free disk flow heat transfer characteristics are simulated, and the accuracy of the rotating disk cavity transient measurement technology is verified by the free disk heat transfer theory. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a method and system for transient measurement of surface heat transfer coefficient in a rotating disk cavity. The large cavity width rotating-static disk cavity structure is designed to approximately simulate the free disk flow heat exchange characteristics, that is, the disk cavity gap ratio G in the rotating-static disk cavity structure is increased, so that the flow state in the disk cavity is approximately consistent with the free disk flow state at the same rotation speed, and the accuracy of the transient measurement method of surface heat transfer coefficient in the experiment is evaluated by the empirical correlation formula of the Nusselt number of the free disk. The present invention solves the problem of accuracy verification of the transient measurement method of surface heat transfer coefficient in a rotating disk cavity.

[0007] The technical solution of the present invention is: a method for transient measurement of surface heat transfer coefficient in a rotating disk cavity, the specific steps are as follows:

[0008] Design the disc cavity gap ratio of the rotor-stator disc cavity structure, and obtain a rotor-stator disc cavity structure with a larger disc cavity gap. The flow characteristics in the disc cavity of this structure conform to the flow characteristics of the free disc.

[0009] Arranging pressure measuring points and temperature measuring points on the rotor-stationary disc cavity structure that increases the disc cavity gap;

[0010] Calculate the working conditions that meet the free disk flow heat transfer characteristics;

[0011] Conduct transient heat transfer experiments based on the calculated operating conditions;

[0012] Based on the data collected at the measuring points in the experiment, the heat transfer temperature in the rotating disk cavity is calculated, and the surface heat transfer coefficient in the rotating disk cavity is obtained according to the transient measurement method of the surface heat transfer coefficient.

[0013] A further technical solution of the present invention is that the disc cavity gap ratio G is designed to be 1.34.

[0014] A further technical solution of the present invention is: the rotating and stationary disc cavity structure for increasing the disc cavity gap includes an air intake casing, a cylindrical casing for increasing the disc cavity gap, and an air outlet casing which are coaxially installed in sequence, and the rotating disc is connected to the disc cavity through a coaxial rotation of a rotating shaft.

[0015] A further technical solution of the present invention is: the temperature measuring points include wall temperature measuring points and relative total temperature measuring points, the wall temperature measuring points are arranged at different radial positions on the inner wall of the disk cavity, and multiple measuring points are evenly distributed in the circumferential direction of each radial position; the relative total temperature measuring point is arranged at 5 mm away from the turntable wall, and the radial position corresponds one-to-one to the radial position of the wall temperature measuring point.

[0016] A further technical solution of the present invention is: the pressure measuring points include a total pressure measuring point and a static pressure measuring point arranged on the stator casing, and the radius position corresponds one-to-one to the radius position of the wall temperature measuring point.

[0017] A further technical solution of the present invention is: the working condition calculation formula that meets the free disk flow heat transfer characteristics is as follows:

[0018]

[0019] In the formula, is the mass flow rate; x = r / b, r is the local radius position of the turntable, and b is the maximum radius of the turntable; is the rotational Reynolds number, ρ is the air flow density, ω is the turntable angular velocity, and μ is the dynamic viscosity.

[0020] A further technical solution of the present invention is: the transient heat exchange experiment sets the moment when the heater is turned on to start heating the airflow as the zero moment of the transient heat exchange. Prior to this, it is necessary to ensure that the flow field in the disk cavity is stable, and adjust the airflow and the rotor domain to reach a thermal equilibrium state.

[0021] A further technical solution of the present invention is: the calculation formula of the heat exchange temperature is as follows:

[0022]

[0023] Where, T aw is the adiabatic wall temperature, i.e. the heat transfer temperature; T rel is the relative total temperature of the airflow; R is the recovery coefficient, and R = Pr 1 / 3 ; ω is the angular velocity of the turntable; r is the local radius position of the turntable; is the circumferential velocity of the airflow at the local position in the disk cavity, obtained from the total pressure and static pressure measurement points; c p is the specific heat at constant pressure.

[0024] A transient measurement system for surface heat transfer coefficient in a rotating disk cavity comprises a rotating and static disk cavity structure for increasing the disk cavity gap and pressure measuring points and temperature measuring points arranged thereon. A heater is arranged at the disk cavity inlet of the rotating and static disk cavity structure.

[0025] A verification method for transient measurement of surface heat transfer coefficient in a rotating disk cavity, the specific steps are as follows:

[0026] Substitute the data obtained from the transient heat transfer experiment into the free disk heat transfer coefficient calculation formula to obtain the theoretical value of the free disk surface heat transfer coefficient; the formula is as follows:

[0027]

[0028] Where λ is the thermal conductivity, ρ is the density, ω is the angular speed of the turntable, r is the local radial position, and μ is the dynamic viscosity;

[0029] The heat transfer coefficient of the rotating disk cavity surface obtained by the transient measurement method of the heat transfer coefficient of the rotating disk cavity surface is compared with the heat transfer coefficient of the free disk surface to verify the accuracy of the measurement method.

[0030] Beneficial Effects

[0031] The beneficial effects of the present invention are as follows: the present invention solves the problem that the accuracy of the surface heat transfer coefficient measurement method cannot be evaluated during the transient heat transfer experiment of the rotating disk cavity. In view of the current situation that there is no recognized Nusselt number empirical relationship in the flow heat transfer characteristics of the rotating-stator disk cavity, a rotating-stator disk cavity structure with a large cavity width is designed. The design based on the disk cavity gap ratio enables the rotating-stator disk cavity structure to simulate the flow heat transfer characteristics of the free disk, providing a comparison benchmark for the surface heat transfer coefficient measurement method. At the same time, numerical calculations and free disk flow heat transfer theory are used to find the corresponding working conditions that meet the free disk flow heat transfer characteristics in the structural model. Subsequently, the surface heat transfer coefficient experimental results under this working condition are compared with the empirical correlation formula of the surface heat transfer coefficient of the free disk to evaluate the accuracy of the transient measurement method of the surface heat transfer coefficient used in the experiment. In summary, the present invention provides a reasonable solution for the accuracy evaluation of the surface heat transfer coefficient measurement method of the rotating disk cavity of an aircraft engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of the transient measurement method of surface heat transfer coefficient and accuracy verification of the present invention;

[0033] Figure 2 Schematic diagram of a rotating-static disk cavity with a large cavity width structure in an embodiment of the present invention;

[0034] Figure 3 This is a diagram showing the arrangement of experimental measurement points in the rotor-stator cavity with a large cavity width according to an embodiment of the present invention;

[0035] Explanation of the reference numerals: 1. Air intake casing, 2. Cylindrical casing for increasing the clearance of the disc cavity, 3. Air outlet casing, 4. Disc cavity inlet, 5. Turntable, 6. Rotating shaft. DETAILED DESCRIPTION

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] Based on the problem that the accuracy of the surface heat transfer coefficient measurement method cannot be evaluated in the current rotating disk cavity transient heat exchange experiment, the present invention proposes a method for transient measurement of the surface heat transfer coefficient in a rotating disk cavity, and the specific steps are as follows:

[0039] Step 1: Design the disc cavity gap ratio of the rotor-stator disc cavity structure to obtain a rotor-stator disc cavity structure with an increased disc cavity gap, and the flow characteristics in the disc cavity of the structure conform to the flow characteristics of the free disc;

[0040] Step 2: Arranging pressure measuring points and temperature measuring points on the rotor-stationary disc cavity structure with the enlarged disc cavity gap;

[0041] Step 3: Calculate the operating conditions that meet the free disk flow heat transfer characteristics;

[0042] Step 4: Conduct transient heat transfer experiments based on the calculated operating conditions;

[0043] Step 5: Based on the data collected from the measuring points in the experiment, the heat transfer temperature in the rotating disk cavity is calculated, and the surface heat transfer coefficient in the rotating disk cavity is obtained according to the transient measurement method of the surface heat transfer coefficient.

[0044] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0045] Reference Figure 1 As shown, in this embodiment, a transient measurement method and verification of the surface heat transfer coefficient in a rotating disk cavity is provided, and the operation steps are as follows:

[0046] Step 1: Design a large cavity width rotating disk cavity test bench. Figure 2 As shown, the test bench includes a turntable, a cylindrical casing, an air intake casing, a rotating shaft, a heater, etc. The specific dimensions have been marked in the figure, and the gap ratio G corresponding to the rotating and stator cavity is 1.34.

[0047] The rotor-stator disc cavity structure designed in this embodiment is an improvement on the typical closed rotor-stator disc cavity structure. The specific structure includes: an air intake casing, a rotating shaft, a rotating disc, an air outlet casing, and a cylindrical casing for increasing the disc cavity gap. Compared with the closed rotor-stator disc cavity structure, the crown used for sealing on the outer edge of the rotating disc is removed to reduce the obstruction of the radial outflow of the airflow at the high radius position; at the same time, the disc cavity gap is increased to expand the flow range of the airflow in the disc cavity and weaken the swirl effect caused by the rotating disc; based on the above two points, under specific experimental conditions, the flow characteristics in the disc cavity under this structure can be achieved to be approximately consistent with the flow characteristics of the free disc, so as to use the relevant theories of the free disc to verify the accuracy of the surface heat transfer coefficient measurement method.

[0048] The conventional rotor-stator disc cavity gap ratio is usually less than 0.5. In order to make the flow structure in the rotor-stator disc cavity approximately conform to the flow structure of the free disc model, the present invention greatly increases the disc cavity gap ratio, and the currently selected gap ratio G is 1.34.

[0049] Step 2: Arrange temperature and pressure measuring points. Figure 3 As shown in the figure, the measuring points of the test bench are arranged as follows: the wall temperature measuring points are arranged at five different radius positions, and two measuring points are evenly arranged in the circumferential direction at each radius position, totaling 10 wall temperature measuring points; relative total temperature: the relative total temperature measuring point is arranged at 5 mm away from the turntable wall, and the radius position corresponds one-to-one with the radius position of the wall temperature measuring point, totaling 10 relative total temperature measuring points; pressure measuring points: the total pressure and static pressure measuring points are arranged on the stator casing, and the radius position corresponds one-to-one with the radius position of the wall temperature measuring point, totaling 10 total pressure measuring points and 10 static pressure measuring points.

[0050] In this embodiment, a thermocouple and a temperature scanning valve are used to measure the airflow temperature, a pressure lead pipe and a pressure scanning valve are used to measure the airflow pressure, and a thermocouple and a data recorder are used to measure the turntable wall temperature.

[0051] Step 3: Determine the experimental working conditions and use numerical calculation to find the specific working conditions when the rotor-stator disk cavity model conforms to the free disk flow and heat transfer law. The airflow inlet mass used in the numerical calculation is obtained through the theoretical relationship of the free disk suction flow.

[0052] Free coil suction flow formula:

[0053]

[0054] In the formula, is the mass flow rate; x = r / b, r is the radius of the turntable at the local position, and b is the maximum radius of the turntable; is the rotational Reynolds number, ρ is the airflow density, ω is the turntable angular speed, and μ is the dynamic viscosity.

[0055] Step 4: Start the transient heat transfer experiment. First, ensure that the flow field in the disk cavity is stable and the airflow and the rotor domain reach a thermal equilibrium state before the airflow step temperature rise is achieved. Then turn on the heater to heat the airflow and set this moment as the zero moment of transient heat transfer.

[0056] Step 5: According to the relevant knowledge of heat transfer, the corresponding heat transfer temperature needs to be obtained before calculating the surface heat transfer coefficient. In the present invention, the heat transfer temperature calculation formula is:

[0057]

[0058] Where, T aw is the adiabatic wall temperature, which refers to the heat transfer temperature; T rel is the relative total temperature of the airflow; R is the recovery coefficient, usually R = Pr 1 / 3 ; ω is the angular velocity of the turntable; r is the local radius position of the turntable; is the circumferential velocity of the airflow at the local position in the disk cavity, obtained from the total pressure and static pressure measurement points; c p is the specific heat at constant pressure.

[0059] Step 6: Evaluate the accuracy of the transient measurement technique for the surface heat transfer coefficient.

[0060] In verifying the accuracy of the measurement method, the benchmark selected by the present invention is the empirical relationship of the free disk, as shown in Formula 3. The empirical relationship of the free disk is:

[0061]

[0062] Where λ is the thermal conductivity, ρ is the density, ω is the angular speed of the turntable, r is the local radial position, and μ is the dynamic viscosity.

[0063] The signals collected by the measuring instrument in the transient experiment are converted into corresponding temperature parameters, pressure parameters and velocity parameters by a computer program. The surface heat transfer coefficient is obtained by using the surface heat transfer coefficient measurement method, and compared with the theoretical correlation formula of the free disk surface heat transfer coefficient to evaluate the accuracy of the transient measurement technology of the surface heat transfer coefficient.

[0064] In this embodiment, when the deviation between the surface heat transfer coefficient measurement result and the free disk theoretical relationship is less than 10%, it means that the surface heat transfer coefficient measurement method used is feasible and accurate. Table 1 shows the comparison between the numerical calculation result of the surface heat transfer coefficient under the working condition determined in step 3 and the free disk theoretical relationship. The calculation results show that the maximum deviation between the surface heat transfer coefficient under the working condition determined in step 3 and the theoretical empirical relationship is less than 10%. It can be considered that the experimental platform structure and operation process of the present invention can accurately simulate the flow heat transfer characteristics of the free disk, that is, the relevant content of the present invention can be used to verify the accuracy of the surface heat transfer coefficient measurement technology during the experiment.

[0065] Table 1 Comparison between the surface heat transfer coefficient calculation results and the free disk theoretical relationship

[0066]

[0067] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for transient measurement of surface heat transfer coefficient in a rotating disk cavity, characterized in that The specific steps are as follows: Design the disc cavity gap ratio of the rotor-stator disc cavity structure, and obtain a rotor-stator disc cavity structure with a larger disc cavity gap. The flow characteristics in the disc cavity of this structure conform to the flow characteristics of the free disc. Arranging pressure measuring points and temperature measuring points on the rotor-stationary disc cavity structure that increases the disc cavity gap; Calculate the working conditions that meet the free disk flow heat transfer characteristics; Conduct transient heat transfer experiments based on the calculated operating conditions; Based on the data collected at the measuring points in the experiment, the heat transfer temperature in the rotating disk cavity is calculated, and the surface heat transfer coefficient in the rotating disk cavity is obtained according to the transient measurement method of the surface heat transfer coefficient.

2. The method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 1, characterized in that: The disc cavity gap ratio G is designed to be 1.

34.

3. The method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 2, characterized in that: The rotating and stationary disc cavity structure for increasing the disc cavity gap comprises an air intake casing, a cylindrical casing for increasing the disc cavity gap, and an air outlet casing which are coaxially installed in sequence, and the rotating disc is coaxially rotatably connected in the disc cavity via a rotating shaft.

4. The method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 3, characterized in that: The temperature measuring points include wall temperature measuring points and relative total temperature measuring points. The wall temperature measuring points are arranged at different radial positions on the inner wall of the disk cavity, and multiple measuring points are evenly distributed in the circumferential direction of each radial position. The relative total temperature measuring point is arranged at a distance of 5 mm from the turntable wall, and the radius position corresponds one-to-one with the radius position of the wall temperature measuring point.

5. The method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 4, characterized in that: The pressure measuring points include a total pressure measuring point and a static pressure measuring point arranged on the stator casing, and the radius positions correspond one-to-one to the radius positions of the wall temperature measuring points.

6. A method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 5, characterized in that: The calculation formula for the working condition that meets the free disk flow heat transfer characteristics is as follows: In the formula, is the mass flow rate; x = r / b, r is the local radius position of the turntable, and b is the maximum radius of the turntable; is the rotational Reynolds number, ρ is the air flow density, ω is the turntable angular velocity, and μ is the dynamic viscosity.

7. A method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 6, characterized in that: The transient heat exchange experiment sets the moment when the heater is turned on to start heating the airflow as the zero moment of transient heat exchange. Prior to this, it is necessary to ensure that the flow field in the disk cavity is stable and adjust the airflow and the rotor domain to reach a thermal equilibrium state.

8. The method for transient measurement of surface heat transfer coefficient in a rotating disk cavity according to claim 7, characterized in that: The calculation formula of the heat exchange temperature is as follows: Where, T aw is the adiabatic wall temperature, i.e. the heat transfer temperature; T rel is the relative total temperature of the airflow; R is the recovery coefficient, and R = Pr 1 / 3 ; ω is the angular velocity of the turntable; r is the local radius position of the turntable; is the circumferential velocity of the airflow at the local position in the disk cavity, obtained from the total pressure and static pressure measurement points; c p is the specific heat at constant pressure.

9. A system for transient measurement of heat transfer coefficient of a surface in a rotating disk cavity, used for implementing the method for transient measurement of heat transfer coefficient of a surface in a rotating disk cavity according to any one of claims 1 to 8; characterized in that: The invention comprises a rotating and static disc cavity structure for increasing the disc cavity gap and pressure measuring points and temperature measuring points arranged thereon. A heater is arranged at the disc cavity inlet of the rotating and static disc cavity structure.

10. A verification method for the transient measurement method of the surface heat transfer coefficient in a rotating disk cavity according to any one of claims 1 to 8, characterized in that The specific steps are as follows: Substitute the data obtained from the transient heat transfer experiment into the free disk heat transfer coefficient calculation formula to obtain the theoretical value of the free disk surface heat transfer coefficient; the formula is as follows: Where λ is the thermal conductivity, ρ is the density, ω is the angular speed of the turntable, r is the local radial position, and μ is the dynamic viscosity; The heat transfer coefficient of the rotating disk cavity surface obtained by the transient measurement method of the heat transfer coefficient of the rotating disk cavity surface is compared with the heat transfer coefficient of the free disk surface to verify the accuracy of the measurement method.

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