JPH08284897A - Cavitation detecting method of turbo pump - Google Patents

Abstract

PURPOSE: To judge the occurrence of a cavitation properly by detecting even a low level one in an accurate manner. CONSTITUTION: A moment measuring instrument 6 consisting of a strain gauge is attached to a wing axis 3 of one blade 4 selected out of plural blades 4 in an impeller 5 of a turbo pump, and in the case where any cavitation has occurred in these blades 4 in time of pumping operation, a variation in moment of the wing axis 3 is measured by a moment measuring instrument 6 by utilizing a fact that moment of each wing axis 3 of respective blades 4 is varied and grows larger, and the measured value is displayed on a display 10, through which the occurrence of cavitation is made so as to be judgeable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting cavitation in a turbo pump.

[0002]

2. Description of the Related Art Conventionally, a plurality of blades 4, 4, ... Through a blade shaft 3 on a blade boss 2 fixed to a main shaft 1 shown in FIG.
In a turbo pump having an impeller 5 to which is attached, when cavitation occurs in the blades 4, 4, ... During pumping operation, a method of detecting cavitation by vibration or noise of the turbo pump is known. However, with this type of detection method, when the flow rate is small, even if vibration occurs, it is difficult to accurately determine whether the cause of this vibration is the flow of water or cavitation. . Further, if the installed state of the turbo pump is deteriorated over time, vibration and noise may occur in the turbo pump regardless of the occurrence of cavitation. That is, the method of detecting cavitation by vibration or noise has a drawback that it is difficult to properly determine the occurrence of cavitation.

On the other hand, there is also known a method of detecting cavitation by knowing the decrease in the head. However, due to the occurrence of cavitation, the rate at which the head is lowered is only about 3%. Moreover, in a turbo pump in which the shape of the blades is taken into consideration, the head may not decrease even if cavitation occurs.
That is, even in the method of detecting cavitation based on the fluctuation of the head, it is difficult to properly determine the occurrence of cavitation, as in the method of detecting cavitation based on the above-described vibration or noise.

Therefore, when the cavitation occurs in the blades 4, 4, ... During the pumping operation, the inventor of the present invention twists about the axis of the blade shaft 3, that is, the blade shaft, as compared with the case where the cavitation does not occur. Focusing on the point that the moment changes and becomes large, the present invention has been completed as a result of earnest research.

[0005]

The problem to be solved is that it is difficult to properly judge the occurrence of cavitation by the method of detecting cavitation by vibration or noise and the method of detecting cavitation by fluctuation of the head. It is a point.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a turbo pump having an impeller in which a plurality of blades are attached to a blade boss fixed to a main shaft via a blade shaft. A feature is that a moment measuring device that measures the moment of the blade axis is installed, and the cavitation of the turbo pump is detected based on the measured value of this moment measuring device. Has achieved the purpose of properly determining the occurrence of.

[0007]

According to the present invention, when cavitation occurs in the blade during the pumping operation of the turbo pump, the moment of the blade axis changes and increases. By measuring the change in the moment of the blade axis with the moment measuring device, it is possible to properly determine the occurrence of cavitation.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the same or corresponding parts as those of the conventional example described in FIG. In FIG.
The turbo pump has an impeller 5 in which a plurality of blades 4, 4, ... Are attached to a blade boss 2 fixed to a main shaft 1 via a blade shaft 3.
It has. A moment measuring device 6 made of, for example, a strain gauge is attached to the blade shaft 3 of one blade 4 selected from the plurality of blades 4, 4, ... Also, it is electrically connected to a transmitter 8 which is a rotary telemeter attached to the main shaft 1 through a signal line 7 which penetrates through the main shaft 1.

On the other hand, a receiver 9 which is close to the transmitter 8 and receives a radio signal transmitted from the transmitter 8 is arranged. 9
The moment measurement value received by is converted into a numerical value and displayed.

In the above structure, when cavitation occurs in the plurality of blades 4, 4, ... During the pumping operation of the turbo pump, the moment of the blade shaft 3 of each blade 4, 4 ,. A blade 3 of one blade 4 selected from the plurality of blades 4, 4, ... Has a moment measuring device 6 formed of, for example, a strain gauge, so that the blade of one blade 4 selected. The moment change of one blade 4 selected from the shafts 3 is measured by the moment measuring device 6. The measured moment measurement value is input to the transmitter 8 via the signal line 7. The transmitter 8 transmits a wireless signal based on the input measurement value of the moment measuring device 6. The transmitted radio signal is received by the receiver 9, and the reception signal is output from the receiver 9 to the display 10,
After being amplified by the display unit 10, the moment measurement value is converted into a numerical value and displayed with a value larger than that in the case where no cavitation occurs. Therefore, by confirming that the measured moment value displayed on the display 10 is larger than the predetermined value, it is possible to properly determine the occurrence of cavitation.

As described above, when the cavitation occurs, the moment measuring device 6 causes the twist around the axis of the blade shaft 3, that is, the moment of the blade shaft to change and become larger than that when the cavitation does not occur. Since cavitation is detected by measuring, cavitation can be reliably detected even at low level cavitation as compared with the conventional detection method that detects cavitation due to vibration, noise, or fluctuations in head. Can be properly determined.

[0012]

As described above, according to the present invention, when cavitation occurs, the twist about the axis of the blade axis, that is, the moment of the blade axis changes and becomes larger than that when cavitation does not occur. By using
Since the cavitation is detected by the moment measuring device, compared with the conventional detection method that detects cavitation due to vibration, noise, or fluctuations in the head, it is possible to reliably detect even low-level cavitation and generate cavitation. You can make a proper judgment.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional example.

[Explanation of symbols]

 1 main shaft 2 blade boss 3 blade shaft 4 blade 5 impeller 6 moment measuring device

Claims (1)

[Claims] 1. A turbo pump including an impeller in which a plurality of blades are attached to a blade boss fixed to a main shaft via a blade shaft, and a moment for measuring a moment of the blade shaft on the blade shaft of the blade. A method for detecting cavitation of a turbo pump, characterized in that a cavitation of the turbo pump is detected based on a measurement value of the moment measuring device.