CN113340411A - Propeller power meter load device for measuring background noise of circulating water tank - Google Patents
Propeller power meter load device for measuring background noise of circulating water tank Download PDFInfo
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- CN113340411A CN113340411A CN202110761469.7A CN202110761469A CN113340411A CN 113340411 A CN113340411 A CN 113340411A CN 202110761469 A CN202110761469 A CN 202110761469A CN 113340411 A CN113340411 A CN 113340411A
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- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
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Abstract
The invention relates to a propeller power instrument load device for measuring background noise of a circulating water tank, which comprises a magnetic powder brake, a shell, a screw shell and a sucker, wherein the magnetic powder brake is arranged on a propeller power instrument shaft and provides a constant torque; the shell is used for wrapping the shell of the magnetic powder brake and sealing the magnetic powder brake inside, the four wing-shaped supports extending out of the shell are respectively connected with the suckers through screws, and the length of each screw is adjusted through threads so as to adapt to circulating water tanks with different sections; the screw rod is wrapped by a screw rod shell.
Description
Technical Field
The invention relates to a propeller dynamometer load device, and belongs to the field of ship and ocean engineering.
Background
The design of propellers or pump-jet impellers of ships and underwater vehicles often needs to meet certain noise indexes, which requires that the underwater noise of the propellers or pump-jet impellers is forecasted in the design process. At present, the commonly used underwater noise prediction methods for propellers or impellers include a numerical prediction method and a model test prediction method, wherein the model test method is a more acceptable underwater noise prediction method.
The propeller noise model test is generally performed in a circulating water tank. The circulating water tank is often made into a vertical return-shaped pipeline structure, the height is generally about 10 meters, a water pump impeller pushes water flow to flow in the return-shaped pipeline at the bottom horizontal pipeline, and a propeller power instrument device, an observation window and related measuring instruments are arranged on the upper horizontal pipeline. A schematic view of the horizontal pipe at the upper part of the circulating water tank is shown in fig. 1.
In a propeller or pump noise model test, the method generally comprises two steps, namely measuring the background noise inside a circulating water tank; then the measurement of the underwater radiation noise of the propeller model is carried out. Typically, the noise measurement of the latter needs to be 6 db higher than the former in order to consider the measured signal to have a sufficient signal-to-noise ratio for prediction.
The background noise inside the circulating water tank is measured, the water flow speed and the pressure level inside the circulating water tank are required to be consistent with the situation when the propeller model is used for formal measurement, and the rotating speed of the propeller dynamometer is also consistent with the rotating speed when the propeller model is used. The basic principle is to keep the same with various parameters during formal test as much as possible. However, in the measurement of the background noise of the circulating water tank, the propeller dynamometer is in a no-load idle state without a propeller model, and the motor load condition is different from that with the propeller model. For the propeller dynamometer motor load with the propeller model, it can be estimated approximately by the following parameters: in a general test, the rotating speed of the propeller model is 20 revolutions per second, the fluid torque of the propeller model is about 6 Nm, and the power required by the propeller dynamometer to supply the propeller model is 754 watts. It can be seen from this evaluation case that the propeller dynamometer has a very large difference in the output power of the motor with and without the propeller model, which leads to an increase in the motor noise and vibration, resulting in a change in the actual background noise of the water tank when the noise model test with the propeller model is performed. This change is caused by the different loads on the motor of the propeller dynamometer and may introduce errors into the test results.
Through the analysis, the existing propeller noise model test based on the circulating water tank has the defect that the load of a propeller power meter is different from the load of a propeller model in the background noise measurement step. The background noise of the circulating water tank adopted at present can be underestimated, and the original test result which is not higher than the background noise by 6 decibels is considered to have enough signal-to-noise ratio for use. On the other hand, it may also lead to an excessive prediction of propeller noise by attributing to the propeller noise the additional noise generated by the load-up of the motor of the propeller dynamometer.
Disclosure of Invention
Aiming at the defects in the background noise measurement link of the circulating water tank, the invention provides a propeller power meter load device which is used for applying a constant torque to a propeller power meter in the background noise measurement link, wherein the constant torque is equal to the fluid torque of a propeller model used in a test under the same rotating speed. And the incidental noise due to the installation of the device is lower than the true background noise of the circulating water tank itself. By adopting the device in the measurement of the background noise of the circulating water tank, the motor of the propeller power meter can be in the same load working condition as that of the motor with the propeller model during the test, so that the real background noise of the circulating water tank is ensured to be obtained through measurement, and the test accuracy of the propeller noise model is improved.
In order to achieve the purpose, the invention adopts the technical scheme that: a propeller power instrument load device for measuring background noise of a circulating water tank comprises a magnetic powder brake, a shell, a screw shell and a sucker, wherein the magnetic powder brake is arranged on a propeller power instrument shaft and provides a constant torque; the shell is used for wrapping the shell of the magnetic powder brake and sealing the magnetic powder brake inside, the four wing-shaped supports extending out of the shell are respectively connected with the suckers through screws, and the length of each screw is adjusted through threads so as to adapt to circulating water tanks with different sections; the screw rod is wrapped by a screw rod shell.
Furthermore, the shell is formed by combining two halves, a cavity in the center of the shell is used for placing a magnetic powder brake, and the whole appearance is obtained by rotating the NACA0012 wing profile for one circle around the center line.
Furthermore, a shaft hole is reserved at the front end of the shell and used for extending out of a shaft of the magnetic powder brake 1, and a shaft seal is arranged.
Furthermore, four airfoil supports extending out of the shell are in a NACA0012 shape, one end of each airfoil support is rigidly connected with the shell, a threaded hole is drilled in the other end of each airfoil support and used for being connected with a screw rod, and a wire routing hole is drilled in one airfoil support and used for a wire of the magnetic powder brake to go out.
Further, the screw rod is a screw rod with threads at two ends.
Furthermore, the screw shell is composed of two halves, the two halves are combined to form a NACA0012 wing shape, one half is provided with a positioning groove, the other half is provided with a positioning convex point for quick positioning, and the two halves are respectively provided with a semicircular wire routing hole for the wire of the magnetic powder brake to go out; the two halves are combined and then tightly connected through bolts, and the angle is adjusted to enable the nose-tail line of the airfoil profile to be parallel to the incoming flow direction.
Further, the screw rod shell is made of plastic or organic glass, and the length of the screw rod shell is matched with that of the screw rod.
Furthermore, the sucker is in a structure that an airfoil section is rigidly connected with a circular sucker, the airfoil shape of the sucker is consistent with that of the screw shell, a threaded hole is drilled at the end part of the airfoil section and is used for being connected with the screw, and the length of the screw can be adjusted through the connecting depth so as to adapt to circulating water tanks with different sections; the circular sucker is adsorbed on the inner wall of the circulating water tank, and the effect of fixing the whole structure is achieved; the suction force of the circular sucker is selected according to the thrust force of the shell and the screw shell in the flow field, and the suction process ensures that the nose tail line of the wing-shaped section of the sucker is parallel to the incoming flow direction.
Further, the load device of the propeller power instrument is arranged in the circulating water tank or on the shell of the propeller power instrument.
Further, after the propeller dynamometer load device is completed, silica gel is used for filling threaded holes in the surface of the shell, and smoothness of the outer surface is guaranteed.
The invention has the beneficial effects that:
the technical key point of the invention is a design scheme of a structural device for applying load to a propeller power meter in a circulating water tank propeller noise model test, and the specific key implementation points are as follows:
(1) the magnetic powder brake provides a torque equal to the torque applied to the propeller model with the same rotating speed for the propeller power meter, and the load of the propeller power meter in the background noise measurement link and the load of the propeller power meter in the real test link are guaranteed to be the same.
(2) A low noise housing design based on NACA0012 airfoil profile;
(3) through the fixing device formed by the screw, the screw shell and the sucker, the threaded connection depth of the screw can be adjusted, so that the circulating water tank is suitable for circulating water tanks with different section sizes.
The method can be used for measuring the background noise of the circulating water tank, and the accuracy of the background noise measurement result is ensured by providing the propeller power meter with the torque equal to the propeller model at the same rotating speed in the background noise measurement process.
Drawings
FIG. 1 is a schematic view of an upper horizontal pipe of a circulation water tank;
FIG. 2 is an overall block diagram of the present invention;
FIG. 3 is a schematic view of a magnetic particle brake;
FIG. 4 is a schematic view of the housing;
FIG. 5 is a schematic view of a screw;
FIG. 6 is a schematic view of a screw housing;
FIG. 7 is a schematic view of a suction cup;
fig. 8 is a view showing the effect of the installation of the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples.
The invention discloses a propeller dynamometer load device for measuring background noise of a circulating water tank, and the whole structure of the propeller dynamometer load device is shown in figure 2. Respectively comprises 5 parts of a magnetic powder brake 1, a shell 2, a screw rod 3, a screw rod shell 4 and a sucker 5.
The magnetic powder brake 1 (see fig. 3) is arranged on a propeller dynamometer shaft and provides a constant torque, the magnitude of the torque is determined according to the test working condition of a propeller model, and the determination process is as follows: at present, the noise test of the propeller model is required to be carried out under the condition of equal thrust coefficient, and generally, the rotating speed of the propeller model in the test is firstly determined, and then the inflow speed of a circulating water tank is adjusted to enable the thrust coefficient of the propeller model to reach a target value. At this time, the torque of the propeller model reaching the target thrust coefficient under the conditions of the propeller model rotating speed and the circulating water tank inflow speed set by the test can be obtained through a torque measuring instrument built in the propeller dynamometer. The magnetic powder brake 1 is a mature product and needs to be electrified during operation. The selected standard is that the adjustable torque range covers the torque range required by the test. The noise level of most magnetic powder brakes is researched and researched to be below 50dB when the magnetic powder brakes work, and is far lower than the background noise of the circulating water tank. The housing 2 is a housing for enclosing the magnetic powder brake 1, and mainly functions to seal the magnetic powder brake 1 therein and reduce disturbance to a flow field through an airfoil housing thereof, thereby reducing additional noise. The shell 2 is formed by combining two halves, the two halves are fixedly connected into a whole through bolt holes 2-6 on the shell and bolts, and the structure of the shell is shown in figure 4. The cavity 2-1 in the center is used for placing the magnetic powder brake 1, and the whole appearance is obtained by rotating the NACA0012 airfoil profile for one circle around the center line. The NACA0012 airfoil is used because a great deal of experimental results show that the overall influence of the flow field is small when the boundary layer separation point of the surface of the airfoil is relatively back. The front end of the shell 2 is provided with a shaft hole 2-2 for the shaft of the magnetic powder brake 1 to extend out and is provided with a shaft seal. Four wing-shaped brackets 2-3 extending from the casing 2 are also in the shape of NACA0012, one end of which is rigidly connected to the casing 2 and the other end of which is drilled with threaded holes 2-4 for the connection of screws 3. In addition, a wire-passing hole 2-5 is drilled in one of the wing-shaped supports 2-3 for the wire of the magnetic powder brake 1 to pass through. The screw rod 3 is a screw rod with threads at two ends, see fig. 5, one end of the screw rod is in threaded connection with four wing-shaped supports extending out of the shell 2, and the length of the screw rod can be adjusted through the depth of the threaded connection so as to adapt to circulating water tanks with different sections and improve the application range. The other end of the screw rod 3 is connected with the sucking disc 5 through threads, and the length of the screw rod can be adjusted through the depth of the threaded connection. The screw housing 4 is a disposable structure for wrapping the screw and is composed of two halves with a screw hole 4-1 in the middle, see fig. 6. The two halves are combined to form a NACA0012 wing shape, wherein one half is provided with a positioning groove 4-2, the other half is provided with a positioning salient point 4-3 for quick positioning, and the two halves are respectively provided with a semicircular wire routing hole 4-4 for the wire of the magnetic powder brake 1 to go out. The length of the screw rod can be adjusted on the test site according to the length of the screw rod, and the screw rod is generally longer and shorter on the test site according to the actual length of the screw rod. The two halves are combined and then tightly connected through bolts, and the angle is adjusted to enable the nose-tail line of the airfoil profile to be parallel to the incoming flow direction. The sucker 5 is a structure formed by rigidly connecting an airfoil section 5-1 and a circular sucker 5-2, the airfoil shape of the sucker is consistent with that of a screw shell 4, a threaded hole is drilled at the end part of the airfoil section 5-1 and is used for being connected with the screw 3, and the length of the screw can be adjusted through the connecting depth so as to adapt to circulating water tanks with different sections. The circular sucker 5-2 is adsorbed on the inner wall of the circulating water tank to play a role in fixing the whole structure. The suction force of the circular sucker is selected according to the thrust force of the shell 2 and the screw shell 4 in the flow field, and the suction process ensures that the nose-tail line of the wing-shaped section of the sucker 5 is parallel to the incoming flow direction. After the whole device is installed, the threaded holes in the surface of the shell are filled with silica gel, and smoothness of the outer surface is guaranteed.
Based on the present invention, the applicable scenarios are as follows:
in the background noise measurement of the circulating water tank, firstly, the magnetic powder brake 1 is installed inside the shell 2, the two shells are screwed through bolts to ensure sealing, and the shaft of the magnetic powder brake 1 is butted with the shaft of the propeller dynamometer 6 through a coupler. Then, screws 3 are installed on the four airfoil-shaped supports of the shell 2 through threaded connections, and the depth of the threaded connections is determined according to the section size of the circulating water tank. Then, a suction cup 5 is installed at the tail end of the screw rod 3 through threaded connection, and the airfoil section of the suction cup 5 is adjusted to be parallel to the incoming flow direction. Finally, the threaded connection depth of the two ends of the screw rod 3 is adjusted, so that the sucker 5 is tightly attached to the inner wall surface of the circulating water tank 7. And finally, adjusting the length of the screw shell 4 according to the exposed length of the screw 3, and wrapping the exposed section of the screw 3. The joints of the screw shell 4 and the wing-shaped sections of the shell 2 and the sucker 5 can have fine seams which are filled by silica gel. And the bolt holes of the whole propeller dynamometer load device 8 exposed outside are also filled and leveled by silica gel, so that the smoothness of the surface is ensured. After the whole device is installed, the magnetic powder brake is electrified, and the background noise can be measured by setting a constant torque equal to the torque of the propeller model in the formal test. The overall effect after assembly in the circulation water tank is shown in fig. 8.
The scheme is that the water tank wall is fixed. A further alternative may be the fixing by means of a propeller power housing. Namely, the fixed point is designed on the shell of the propeller dynamometer by changing the configurations of the screw rod 3, the screw rod shell 4 and the suction cup 5.
Claims (10)
1. The utility model provides a screw power appearance load device for circulating water tank background noise is measured which characterized in that: the magnetic powder brake is arranged on a propeller power instrument shaft and provides a constant torque; the shell is used for wrapping the shell of the magnetic powder brake and sealing the magnetic powder brake inside, the four wing-shaped supports extending out of the shell are respectively connected with the suckers through screws, and the length of each screw is adjusted through threads so as to adapt to circulating water tanks with different sections; the screw rod is wrapped by a screw rod shell.
2. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the shell is formed by combining two halves, a cavity in the center of the shell is used for placing a magnetic powder brake, and the whole appearance is obtained by rotating the NACA0012 wing profile for a circle around the center line.
3. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the front end of the shell is provided with a shaft hole for the shaft of the magnetic powder brake 1 to extend out, and a shaft seal is arranged.
4. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: four airfoil supports that the shell stretches out are NACA0012 appearance, and one end and shell rigid connection, the screw hole is bored to the other end for connecting screw rod, and one of them airfoil support bores and has the line hole, supplies magnetic powder brake's electric wire to walk out.
5. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the screw rod is provided with threads at two ends.
6. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the screw shell is composed of two halves, the two halves are combined to form a NACA0012 wing type, one half is provided with a positioning groove, the other half is provided with a positioning bump for quick positioning, and the two halves are respectively provided with a semicircular wiring hole for leading out a wire of the magnetic powder brake; the two halves are combined and then tightly connected through bolts, and the angle is adjusted to enable the nose-tail line of the airfoil profile to be parallel to the incoming flow direction.
7. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the screw rod shell is made of plastic or organic glass, and the length of the screw rod shell is matched with that of the screw rod.
8. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the sucker is a structure in which an airfoil section is rigidly connected with a circular sucker, the airfoil shape of the sucker is consistent with that of a screw shell, a threaded hole is drilled at the end part of the airfoil section and is used for being connected with a screw, and the length of the screw can be adjusted through the connection depth so as to adapt to circulating water tanks with different sections; the circular sucker is adsorbed on the inner wall of the circulating water tank, and the effect of fixing the whole structure is achieved; the suction force of the circular sucker is selected according to the thrust force of the shell and the screw shell in the flow field, and the suction process ensures that the nose tail line of the wing-shaped section of the sucker is parallel to the incoming flow direction.
9. The propeller dynamometer load device for circulating water tank background noise measurement of claim 1, further comprising: the propeller power instrument load device is arranged in the circulating water tank or on the shell of the propeller power instrument.
10. The propeller dynamometer load device for circulating water tank background noise measurement of claim 9, further comprising: after the propeller dynamometer load device is installed, the threaded holes in the surface of the shell are filled with silica gel, and smoothness of the outer surface is guaranteed.
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