Experimental system and working method for measuring friction loss of high-pressure fluid in rotor-static gap

Abstract

The present invention discloses an experimental system for measuring the friction loss of high-pressure fluid in the rotor-static gap and its working method, which belong to the field of impeller machinery design and analysis technology. Compared with the conventional friction loss measurement method, the present invention eliminates the influence of the bearing friction loss and the graphite ring sealing device friction loss in the main device of the experimental platform on the measurement of the fluid friction loss in the rotor-static gap, and greatly improves the measurement accuracy of fluid friction. At the same time, when measuring the bearing friction loss and the graphite ring sealing device friction loss, the fluid pressure in the rotor-static gap is fully reduced to reduce the influence of the fluid friction loss and improve the measurement accuracy. By improving the shaft end sealing technology, the measurement of the friction loss of high-pressure, high-density supercritical fluid in the rotor-static gap is realized. The present invention realizes the high-precision measurement of the friction loss of high-pressure fluid in the rotor-static gap, which can be used for the calibration of numerical simulation methods and friction loss prediction models.

Description

Technical Field

[0001] The invention belongs to the technical field of impeller machinery design and analysis, and particularly relates to an experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap and a working method thereof. Background Art

[0002] Impeller machinery is an important heat-to-power conversion device, and its efficiency has a significant impact on the overall performance of the cycle. Therefore, the study of internal losses in impeller machinery has always been a hot topic. For impeller machinery using high-pressure, high-density supercritical fluid as the working fluid, friction losses within the rotor-static clearance have become one of the key issues affecting operating efficiency. Public research results show that friction losses within high-speed impeller machinery have become the main source of losses. In the supercritical carbon dioxide principle prototype at Sandia National Laboratories in the United States, friction losses within the impeller machinery accounted for 37.5% of the total losses.

[0003] At present, the research on fluid friction loss in the rotor-static gap has the following problems: 1) In previous friction loss experimental systems, it is difficult to distinguish between fluid friction loss and bearing friction loss. The bearing friction loss in the main device of the experimental bench is included in the fluid friction loss in the rotor-static gap, which makes the error of the experimental measurement results larger and reduces the prediction accuracy of the friction loss model; 2) In previous friction loss experimental systems, the shaft end sealing technology is less difficult, and only the friction loss of low-pressure fluids in the rotor-static gap can be studied. However, experiments on high-pressure and high-density supercritical fluids are difficult to implement. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide an experimental system and working method for measuring the friction loss of high-pressure fluid in the rotor-static gap, which can accurately measure the friction loss of supercritical fluid in the rotor-static gap.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention discloses an experimental system for measuring the friction loss of high-pressure fluid in a rotor-static gap, comprising a high-speed motor, a torque detection device, an experimental platform main device, a data acquisition system, a gap and sealing air supply system, and a vacuum pumping system;

[0007] The main device of the experimental platform includes a rotor and a housing. The rotor is located inside the housing and supported by bearings at both ends. A graphite ring sealing device is installed between the middle of the rotor and the bearings at both ends. A sealed air supply port is provided in the middle of the graphite ring sealing device. A rotor-static gap is formed between the middle of the rotor and the housing. A temperature and pressure detection device is installed in the rotor-static gap.

[0008] The high-speed motor is connected to a motor cooling system and a speed control device. The high-speed motor is connected to one end of the torque detection device through a first coupling, and the other end of the torque detection device is connected to the rotor through a second coupling; the torque detection device and the temperature and pressure detection device are respectively connected to the data acquisition system; the vacuum system is connected to the rotor-static gap; the gap and sealed air supply system are respectively connected to the rotor-static gap and the sealed air supply port.

[0009] Preferably, the torque detection device is a micro-range dynamic torque sensor, the accuracy of the torque detection device is higher than ±0.5%, and the response time is less than 1ms; the first coupling and the second coupling are laminated flexible couplings.

[0010] Preferably, the speed control device is a frequency converter, the power interface of the high-speed motor is connected to the power interface of the frequency converter, and the control signal interface of the high-speed motor is connected to the control signal interface of the frequency converter.

[0011] Preferably, the graphite ring sealing device includes a graphite sealing ring and a labyrinth seal, the sealed air supply port is arranged in the middle of the graphite sealing ring, and the labyrinth seal is arranged between the graphite sealing ring and the rotor-static gap.

[0012] Preferably, the motor cooling system includes a cooling water tank, a cooling water regulating valve, a cooling water pump and an air heat exchanger connected in sequence through a cooling water circulation pipeline, and the internal cooling channel of the high-speed motor is connected to the cooling water pump and the air heat exchanger respectively.

[0013] Preferably, the gap and sealing air supply system includes several groups of high-pressure gas cylinders, and the outlets of the several groups of high-pressure gas cylinders are respectively connected to the gap air supply pipeline and the sealing air supply pipeline; the gap air supply pipeline is connected to the rotary-static gap, and a gap air supply electric valve is provided on the gap air supply pipeline; the sealing air supply pipeline is connected to the graphite ring sealing device, and a sealing air supply electric valve is provided on the sealing air supply pipeline.

[0014] Preferably, the vacuum system includes a vacuum pipeline, an electric regulating valve and a vacuum pump arranged on the vacuum pipeline. The vacuum pipeline is connected to the rotor-static gap, and the electric regulating valve is arranged upstream of the vacuum pump.

[0015] Preferably, the rotor is a hollow shaft structure; and the bearing is a P2 grade angular contact ball bearing.

[0016] The working method of the experimental system for measuring the friction loss of high-pressure fluid in the rotor-static gap disclosed in the present invention includes:

[0017] S1: Start the motor cooling system;

[0018] S2: The speed control device starts and controls the high-speed motor to rotate at a preset speed, driving the rotor in the main device of the experimental platform to rotate;

[0019] S3: Close the gap and seal the air supply system, open the vacuum system to vacuum the rotating static gap;

[0020] S4: After the bearing temperature stabilizes, the rotor torque is measured by a micro-range dynamic torque sensor, and the temperature and pressure in the rotor-static gap are measured by a temperature and pressure detection device in the rotor-static gap, and input into the data acquisition system;

[0021] S5: Open the gap and seal the gas supply system, close the vacuum system, and maintain the gas pressure in the rotary-static gap at the preset pressure and temperature;

[0022] S6: Repeat S4 and measure the friction torque of the bearing, the friction torque of the graphite ring seal, and the friction torque of the fluid in the rotor-static gap at the same bearing temperature;

[0023] S7: The difference between the torque measured by S6 and the torque measured by S4 is the friction torque of the fluid in the rotor-static gap, and the friction loss at the preset pressure and temperature in the rotor-static gap is calculated by the preset speed set by S2;

[0024] S8: Repeat S2 to S7 to obtain friction loss data of the rotor under the conditions of constant fluid pressure and temperature in the rotor-static gap and different rotational speeds and under the conditions of different fluid pressure and temperature in the rotor-static gap and constant rotational speed.

[0025] Preferably, in S5, the absolute pressure in the rotor-static gap is lower than 2 kPa.

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] In previous experimental studies of friction loss, it was difficult to distinguish between fluid friction loss and bearing friction loss. Consequently, bearing friction loss within the main experimental platform assembly was included in the fluid friction loss within the rotor-static clearance, resulting in low precision in the experimental measurement results. The experimental system of the present invention measures the bearing friction loss within the main experimental platform assembly and the friction loss of the graphite ring seal assembly, using these as base numbers to eliminate these losses in the experimental results, thereby accurately determining the fluid friction loss within the rotor-static clearance. In previous experimental studies of friction loss, the medium used had low pressure and density, making shaft-end sealing technology difficult to implement, making experiments with high-pressure, high-density supercritical fluids difficult. The experimental system of the present invention incorporates graphite ring seals on either side of the rotor-static clearance within the main experimental platform assembly, with a sealed air supply port located in the middle of the graphite ring seals to prevent fluid leakage within the rotor-static clearance. Although the graphite ring seals maintain close contact with the rotor during operation, their friction loss is eliminated along with the bearing friction loss as a base number in the experimental results. Therefore, while achieving a sealing effect, the measurement accuracy of the fluid friction loss within the rotor-static clearance is not affected. To ensure high-precision measurement of bearing friction loss and graphite ring seal friction loss within the main body of the test bench, the experimental system of the present invention utilizes a vacuum system to fully reduce the fluid pressure within the rotor-static gap during measurement of bearing friction loss and graphite ring seal friction loss. This reduces the impact of fluid friction loss within the rotor-static gap and improves the measurement accuracy of bearing friction loss and graphite ring seal friction loss. A gap and seal air supply system steadily supplies high-pressure supercritical fluid to the rotor-static gap and high-pressure gas to the intermediate body of the graphite ring seal, preventing leakage of the high-pressure supercritical fluid and further improving measurement accuracy.

[0028] Furthermore, the torque detection device adopts a micro-range dynamic torque sensor, the accuracy of the torque detection device is higher than ±0.5%, and the response time is less than 1ms, which can ensure the accuracy and real-time performance of the torque measurement signal.

[0029] Furthermore, the speed control device adopts a frequency converter, which can accurately control the speed of the high-speed motor.

[0030] Furthermore, the graphite ring sealing device includes a graphite sealing ring and a labyrinth seal, the sealed air supply port is arranged in the middle of the graphite sealing ring, and the labyrinth seal is arranged between the graphite sealing ring and the rotor-static gap, further improving the sealing performance.

[0031] Furthermore, the cooling water in the motor cooling system passes through the internal cooling channel of the high-speed motor, the air heat exchanger, the cooling water tank, the cooling water regulating valve and the cooling water pump in sequence, and enters the high-speed motor again, forming a cycle, reducing the internal temperature of the high-speed motor and avoiding overheating.

[0032] Furthermore, the gap and sealing gas supply system realizes sealing and supplies gas to the rotating static gap through several groups of high-pressure gas cylinders, and controls the gas flow through the gap gas supply electric valve and the sealing gas supply electric valve.

[0033] Furthermore, the rotor adopts a hollow shaft structure to reduce the rotor mass and starting torque, thereby improving measurement accuracy; the bearing adopts P2 grade angular contact ball bearings to ensure the rotation accuracy of the rotor, avoid the unevenness of the rotor-static clearance formed by the rotor and the housing along the circumferential direction, and ensure the accuracy of the measurement results.

[0034] The working method of the experimental system for measuring the friction loss of high-pressure fluid in the rotor-static gap disclosed in the present invention is simple to operate, eliminates the errors caused by bearing friction loss and graphite ring sealing device friction loss in previous experiments, and improves measurement accuracy.

[0035] Furthermore, after evaluation, it was found that when the absolute pressure in the rotary-static gap of the main device of the experimental bench was lower than 2kPa, the fluid friction loss in the rotary-static gap had almost no effect on the measurement of the bearing friction loss and the friction loss of the graphite ring sealing device, thus ensuring the accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0037] Figure 2 This is a structural diagram of the main device of the experimental platform.

[0038] In the figure: 1-high-speed motor, 2-first coupling, 3-torque detection device, 4-second coupling, 5-laboratory main body, 6-data acquisition system, 7-frequency converter, 8-gap air supply electric valve, 9-seal air supply electric valve, 10-high-pressure gas cylinder, 11-electric regulating valve, 12-vacuum pump, 13-cooling water tank, 14-cooling water regulating valve, 15-cooling water pump, 16-air heat exchanger, 17-rotor, 18-housing, 19-rotor-static clearance, 20-graphite ring sealing device, 21-bearing. DETAILED DESCRIPTION

[0039] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments, which are intended to explain rather than limit the present invention:

[0040] like Figure 1 , which is an experimental system for measuring the friction loss of high-pressure fluid in a rotor-static gap of the present invention, comprising a high-speed motor 1, a torque detection device 3, a main experimental platform device 5, a data acquisition system 6, a gap and sealing air supply system, and a vacuum system;

[0041] The main device 5 of the experimental platform includes a rotor 17 and a housing 18. The rotor 17 is arranged inside the housing 18. Both ends of the rotor 17 are supported by bearings 21. Graphite ring sealing devices 20 are provided between the middle of the rotor 17 and the bearings 21 at both ends. A sealed air supply port is provided in the middle of the graphite ring sealing device 20. A rotor-static gap 19 is formed between the middle of the rotor 17 and the housing 18. A temperature and pressure detection device is provided in the rotor-static gap 19.

[0042] The high-speed motor 1 is connected to a motor cooling system and a speed control device 7. The high-speed motor 1 is connected to one end of the torque detection device 3 through the first coupling 2, and the other end of the torque detection device 3 is connected to the rotor 17 through the second coupling 4; the torque detection device 3 and the temperature and pressure detection device are respectively connected to the data acquisition system 6; the vacuum system is connected to the rotor-static gap 19; the gap and sealed air supply system are respectively connected to the rotor-static gap 19 and the sealed air supply port.

[0043] In a preferred embodiment of the present invention, the torque detection device 3 is a micro-range dynamic torque sensor, the accuracy of the torque detection device 3 is higher than ±0.5%, and the response time is less than 1ms; the first coupling 2 and the second coupling 4 are laminated flexible couplings.

[0044] In a preferred embodiment of the present invention, the speed control device 7 is a frequency converter, the power interface of the high-speed motor 1 is connected to the power interface of the frequency converter, and the control signal interface of the high-speed motor 1 is connected to the control signal interface of the frequency converter.

[0045] In a preferred embodiment of the present invention, the graphite ring sealing device 20 includes a graphite sealing ring and a labyrinth seal. The sealed air supply port is located in the middle of the graphite sealing ring, and the labyrinth seal is located between the graphite sealing ring and the rotor-static gap 19, that is, on the inner side of the graphite sealing ring.

[0046] In a preferred embodiment of the present invention, the motor cooling system includes a cooling water tank 13, a cooling water regulating valve 14, a cooling water pump 15 and an air heat exchanger 16 which are connected in sequence through a cooling water circulation pipeline, and the internal cooling channel of the high-speed motor 1 is connected to the cooling water pump 15 and the air heat exchanger 16 respectively.

[0047] In a preferred embodiment of the present invention, the gap and sealing air supply system includes several groups of high-pressure gas cylinders 10, and the outlets of the several groups of high-pressure gas cylinders 10 are respectively connected to the gap air supply pipeline and the sealing air supply pipeline; the gap air supply pipeline is connected to the rotary-static gap 19, and a gap air supply electric valve 8 is provided on the gap air supply pipeline; the sealing air supply pipeline is connected to the graphite ring sealing device 20, and a sealing air supply electric valve 9 is provided on the sealing air supply pipeline.

[0048] In a preferred embodiment of the present invention, the vacuum system includes a vacuum pipeline and an electric regulating valve 11 and a vacuum pump 12 arranged on the vacuum pipeline. The vacuum pipeline is connected to the rotor-static gap 19, and the electric regulating valve 11 is arranged upstream of the vacuum pump 12.

[0049] In a preferred embodiment of the present invention, the rotor 17 is a hollow shaft structure; the bearing 21 is a P2 grade angular contact ball bearing.

[0050] The working method of the experimental system for measuring the friction loss of high-pressure fluid in the rotor-stationary gap comprises the following steps:

[0051] S1: Start the cooling water regulating valve 14 and the cooling water pump 15 in sequence, and the motor cooling system works normally to avoid overheating inside the motor;

[0052] S2: Start the high-speed motor 1 through the frequency converter, set a certain experimental speed, and keep running for 2 minutes;

[0053] S3: Close the gap air supply electric valve 8 and the sealing air supply electric valve 9, open the electric regulating valve 11, start the vacuum pump 12, and evacuate the rotor-static gap 19 to an absolute pressure of less than 2 kPa for 1 minute;

[0054] S4: After the temperature of the bearing 21 in the main device 5 of the test bench is stabilized, the rotor speed, torque, and pressure and temperature in the gap are measured by the micro-range dynamic torque sensor and the sensor on the main device 5 of the test bench. The data are entered into the data acquisition system 6 and recorded, and the bearing friction torque and the graphite ring sealing device friction torque are measured;

[0055] S5: Open the gap air supply electric valve 8 and the sealing air supply electric valve 9, close the electric regulating valve 11 and the vacuum pump 12, and maintain the gas pressure in the rotary-static gap 19 at a certain experimental pressure and temperature.

[0056] S6: Repeat S4, and at the same bearing temperature, measure the bearing friction torque, the graphite ring sealing device friction torque, and the fluid friction torque in the rotor-static gap 19;

[0057] S7: The difference between the torque measured by S6 and the torque measured by S4 is the fluid friction torque, and the friction loss of the fluid in the rotor-static gap 19 under a certain temperature and pressure is calculated by the speed set by S2;

[0058] S8: Repeat S2 to S7 to obtain friction loss data of the rotor 17 under the conditions of constant fluid pressure and temperature in the rotor-static gap 19 and different rotational speeds, and under the conditions of different fluid pressures and temperatures in the rotor-static gap 19 and constant rotational speed;

[0059] S9: Close the gap air supply electric valve 8 and the seal air supply electric valve 9, and turn off the high-speed motor 1 through the frequency converter;

[0060] S10: When the temperature inside the high-speed motor 1 drops below 30° C., the cooling water pump 15 and the cooling water regulating valve 14 are closed in sequence.

[0061] The above description is only part of the embodiments of the present invention. Although some terms are used in the present invention, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of the present invention. Interpreting them as any additional limitations is contrary to the spirit of the present invention. The above description is only to further illustrate the content of the present invention with examples to facilitate easier understanding, but it does not mean that the embodiments of the present invention are limited to these. Any technical extension or re-creation made according to the present invention is protected by the present invention.

Claims

1. An experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap, characterized in that: It includes a high-speed motor (1), a torque detection device (3), a test bench main device (5), a data acquisition system (6), a gap and sealing air supply system and a vacuum pumping system; The main device (5) of the experimental table includes a rotor (17) and a housing (18). The rotor (17) is arranged inside the housing (18). Both ends of the rotor (17) are supported by bearings (21). A graphite ring sealing device (20) is provided between the middle of the rotor (17) and the bearings (21) at both ends. A sealed air supply port is provided in the middle of the graphite ring sealing device (20); a rotor-static gap (19) is formed between the middle of the rotor (17) and the housing (18); and a temperature and pressure detection device is provided in the rotor-static gap (19); The high-speed motor (1) is connected to a motor cooling system and a speed control device (7). The high-speed motor (1) is connected to one end of the torque detection device (3) via a first coupling (2), and the other end of the torque detection device (3) is connected to the rotor (17) via a second coupling (4). The torque detection device (3) and the temperature and pressure detection device are respectively connected to the data acquisition system (6); the vacuum system is connected to the rotor-static gap (19); and the gap and seal air supply system are respectively connected to the rotor-static gap (19) and the seal air supply port.

2. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1 is characterized in that: The torque detection device (3) is a micro-range dynamic torque sensor, the accuracy of the torque detection device (3) is higher than ±0.5%, and the response time is less than 1 ms; the first coupling (2) and the second coupling (4) are laminated flexible couplings.

3. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1, characterized in that: The speed control device (7) is a frequency converter, the power interface of the high-speed motor (1) is connected to the power interface of the frequency converter, and the control signal interface of the high-speed motor (1) is connected to the control signal interface of the frequency converter.

4. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1, characterized in that: The graphite ring sealing device (20) comprises a graphite sealing ring and a labyrinth seal, wherein the sealing air supply port is arranged in the middle of the graphite sealing ring, and the labyrinth seal is arranged between the graphite sealing ring and the rotor-static gap (19).

5. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1, characterized in that: The motor cooling system includes a cooling water tank (13), a cooling water regulating valve (14), a cooling water pump (15) and an air heat exchanger (16) which are sequentially connected through a cooling water circulation pipeline, and the internal cooling channel of the high-speed motor (1) is connected to the cooling water pump (15) and the air heat exchanger (16) respectively.

6. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1, characterized in that: The gap and sealing air supply system comprises a plurality of groups of high-pressure gas cylinders (10), the outlets of the plurality of groups of high-pressure gas cylinders (10) are respectively connected to a gap air supply pipeline and a sealing air supply pipeline; the gap air supply pipeline is communicated with the rotary-static gap (19), and a gap air supply electric valve (8) is provided on the gap air supply pipeline; the sealing air supply pipeline is communicated with the graphite ring sealing device (20), and a sealing air supply electric valve (9) is provided on the sealing air supply pipeline.

7. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1, characterized in that: The vacuum pumping system includes a vacuum pumping pipeline, an electric regulating valve (11) and a vacuum pump (12) arranged on the vacuum pumping pipeline. The vacuum pumping pipeline is connected to the rotor-static gap (19). The electric regulating valve (11) is arranged upstream of the vacuum pump (12).

8. The experimental system for measuring friction loss of high-pressure fluid in a rotor-static gap according to claim 1, characterized in that: The rotor (17) is a hollow shaft structure; the bearing (21) is a P2 grade angular contact ball bearing.

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