JPS6117273Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pump with an induction device, and relates to an improvement of the pump with an induction device, which improves suction performance with an extremely simple structure and facilitates its adjustment.

As pumps become faster and more compact, improvements in suction performance are required, and a structure in which a spiral impeller called an inducer is installed coaxially with the pump main impeller in front of the pump main impeller, that is, on the pump suction port side, has become popular. However, this pump with an inducer has a flow rate of approximately 60% or less of the design flow rate, and a low NPSH.
Under these conditions, low-cycle pressure pulsations occur, causing large vibrations and noise within the pump piping, which may interfere with pump operation.

The cause of this pressure pulsation has not been elucidated in detail, but as a countermeasure, (a) the design flow rate of the inducer is set to approximately the design flow rate of the main impeller, as shown in Japanese Patent Publication No. 16094/1973.
2.5 to 4 times, and a structure in which a diaphragm plate or nozzle is fixed almost immediately in front of the inducer is (b) As shown in JP-A-52-11405, the pump suction pipe is connected to the outlet side of the inducer and the inducer. (c) As shown in JP-A-52-10902, a structure is provided in which a bypass pipe is provided that opens to the inlet side and a part of the fluid on the inducer outlet side is circulated to the inducer inlet side through the bypass pipe. There is a method of creating a warp by bending the rear end of the blade in a direction that increases the exit angle, or bending the front end of the blade in a direction that decreases the entrance angle, as shown in (d) Japanese Patent Application Laid-Open No. 105604/1983. A structure in which a plurality of inducers are arranged in series and the blade angle of the preceding stage inducer is set smaller than the blade angle of the subsequent stage inducer is (e) the most advanced of the inducers as shown in Japanese Patent Application Laid-Open No. 105603/1983. Various structures have been proposed, such as one in which one end of the sleeve is fixed to the outer periphery and the other end is bent inward to form a constriction. In order to suppress pulsation, for example, in the structure (a), the shape, dimensions, installation position, etc. of the aperture plate or nozzle, and in the structure (b), the flow rate to be circulated, the opening position of the bypass pipe, etc. In the method (c), the angle of warp and the range of warp, etc., in the structure (d), the degree of change in the blade angle, etc., and in the structure (e), the axial length of the sleeve and the diaphragm. It is necessary to test and adjust the inner diameter of each part.

In order to make this adjustment, first operate the pump and measure the pressure pulsation and pump performance. If either of these is not satisfied, disassemble the inducer part and check the dimensions, angle, position, etc. of the inducer part as described above. After making changes, reassemble and operate the pump, and repeat this process until the pressure pulsation and pump performance are satisfied.In addition to the measurement work and disassembly and assembly work, the dimensions, angle, position, etc. of the inducer part are Changing this requires processing operations such as cutting, welding, and forming, which is extremely complicated and takes a lot of time.

Furthermore, any of the above proposals may or may not be effective depending on the pump specifications such as the total head and discharge amount, and the pump structure such as the type of inducer and main impeller and the configuration of their combination. As mentioned above, the cause of pressure pulsation is not understood in detail, so it is difficult to predict, and there is no definitive means to prevent pressure pulsation in all pumps with an inducer.

In this way, it is difficult to select which structure among the proposals mentioned above can prevent pressure pulsations for a given pump with an inducer without conducting a test. However, due to the structure and dimensional constraints of the pump, it is extremely difficult to change the structure after manufacture.

In addition, since the pressure pulsations mentioned above do not occur in pumps with inducers of all specifications and structures,
It is extremely uneconomical to adopt a structure such as the one proposed above in advance in order to prevent pressure pulsations.

The present invention has been developed in view of the above, and by providing a baffle plate in front of the inductor of a pump with an inducer, and arranging this baffle plate coaxially with the inducer, pressure pulsations in the pump with an inducer can be suppressed without machining work. This can be prevented by simply attaching the baffle plate without making any changes to the pump structure, and the adjustment work is extremely easy, and furthermore, it can be combined with a conventional pressure pulsation prevention structure. This provides a pump with an inducer that can prevent the pressure pulsation for a wider range of pump specifications and pump structures.

Next, the present invention will be explained based on an embodiment shown in FIG.

Reference numeral 1 designates a pump casing, in which a pump main impeller 3 is disposed within a whirlpool chamber 2, and a spiral impeller 5 serving as an inducer is disposed within a pump suction port 4 of the pump casing 1. The helical impeller 5 and the main impeller 3 are each inserted into the pump rotating shaft 7 via a key 6.

A disc-shaped baffle plate 8 is screwed to the tip of the rotating shaft 7 in front of the helical impeller 5 with a bolt 9 via a rotation preventing lock 10, and the bolt 9 is fastened. Accordingly, the baffle plate 8 is connected to the main impeller 3 and the spiral impeller 5.
The pump main impeller 3, the spiral impeller 5, and the baffle plate 8 are thus arranged coaxially.

In addition, 11 in the figure is a pump discharge port formed in the pump casing 1.

Next, the measurement results of the low cycle pressure pulsation in the embodiment of the present invention configured as described above will be explained.

Figure 2 shows a total head of 20m and a discharge flow rate of 1000/
In this implementation, a disk-shaped baffle plate 8 with an outer diameter of 75 mm was attached to a pump with an inducer driven by a 3-phase 4-pole 60 Hz squirrel-cage induction motor with design specifications of min, suction port diameter of 125 mm, and discharge port diameter of 100 mm. Fig. 3 shows the pressure pulsations at the pump discharge port 11 when the pump of this example is operated with the effective suction head set at 0.5 m, with the baffle plate 8 removed from the pump of this example with the above specifications. In the figure, a,
b, c, d, and e are 100% and 80% of the design flow rate, respectively.
%, 60%, 40% and 20% flow rate.

As is clear from a comparison of FIG. 2 and FIG. 3, the pressure pulsation of the pump according to the embodiment of the present invention has a width of 2 at a flow rate of 80% to 40% of the design flow rate.
It is reduced by 1/3 to 1/3,
In particular, at a flow rate of 20% of the designed flow rate, where pressure pulsations were large, good results were obtained in which the width of the pulsations was reduced to about one-fourth.

As described above, according to the present embodiment, simply attaching the baffle plate 8 to the pump rotating shaft 7 facing the tip of the helical impeller 5 of the pump with an inducer requires a structural change of the pump that requires machining work. As mentioned above, pressure pulsations can be prevented by a very simple improvement that does not prevent pressure pulsations, so even if all pumps with an inducer do not have a structure like the conventional example, which prevents pressure pulsations in advance, it is possible to prevent pressure pulsations only when pressure pulsations occur. It is sufficient to adopt the embodiment, and it is extremely economical.

Further, the adjustment for preventing pressure pulsations in this embodiment is carried out by operating the pump with the baffle plate 8 of an appropriate diameter attached, as in the conventional example, and measuring the pressure pulsations and pump performance. If either of these conditions is not satisfied, replace the baffle plate 8 with one of a different diameter, that is, if the pressure pulsation is not reduced significantly, use a baffle plate 8 with a larger diameter. Then, replace each baffle plate 8 with a smaller diameter baffle plate and repeat this process until the pressure pulsation and pump performance are satisfied. However, if you prepare several types of baffle plates 8 with different diameters in advance, Unlike the conventional example, processing operations such as cutting, welding, and molding are not required, and adjustment operations are extremely easy.

In the embodiment described above, the baffle plate 8 is shaped like a sectioned plate, but it may have another shape such as a conical shape, and may be appropriately selected depending on the pump specifications, structure, and effect of the baffle plate 8.

In addition, by combining the present invention with a structure for preventing pressure pulsation such as the conventional example, pressure pulsation can be prevented for a wider range of pump specifications and structures since the range of each effect is different. In a pump with an inducer that has a structure that prevents pressure pulsations, such as the one shown in the example above, if a sufficient effect cannot be obtained in a certain flow rate range even after adjustment, it is necessary to change to another structure such as the conventional example. However, its utility value is great, as the effect can be obtained by an extremely simple improvement that only requires the use of the baffle plate 8 of the present invention.

According to the present invention, it is possible to prevent pressure pulsation in a pump with an inducer, and what is more, the extremely simple work of simply attaching a baffle plate is sufficient, without the need to change the pump structure that involves machining work. Moreover, the adjustment work is extremely easy, and pressure pulsation can be prevented for a wider range of pump specifications and pump structures by simply preparing baffle plates of different types and diameters, and processing such as cutting and welding forming is possible. No work is required and workability is improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a pump with an inducer according to an embodiment of the present invention, Fig. 2 is a diagram showing pressure pulsations at various flow rates of the pump according to the above embodiment, and Fig. 3 is a diagram of a pump without baffle plates. It is a figure showing pressure pulsation at each flow rate. 3... Pump main impeller, 5... Spiral impeller as an inducer, 7... Pump rotation shaft, 8
...Baffle board.

Claims (1)

[Scope of utility model registration request] A pump with an inducer, characterized in that an inducer is provided in front of a pump main impeller, a baffle plate is provided in front of the inducer, and the pump main impeller, the inducer, and the baffle plate are arranged coaxially with a pump rotation shaft.