JPS6138198A - Diffuser for centrifugal hydraulic machine - Google Patents

Abstract

PURPOSE:To recover the pressure sufficiently by controlling the secondary flow in lateral direction of flow path in diffuser then smoothing the flow distorted in lateral direction at the inlet of diffuser and decelerating thereby reducing the pressure loss. CONSTITUTION:Upon supply of flow distorted in lateral direction of the flow path of diffuser 7 from an impeller 4, the fluid at the sideboard 2 side having low flow angle is forcefully increased of the flow angle through a guide vane 12 to increase the speed component in radial direction thus to have sufficient kinetic energy for overcoming the pressure gradient in radial direction of the diffuser 7. Consequently, the fluid at the coreboard 3 side will flow to the sideboard 2 side and decelerated smoothly to the position separated by 1.2-1.3 times of the outerdiameter of the impeller 4 while being smoothed gradually. Since the guidevane 13 will guide such that the flow angle at the sideboard 2 side between said position of the outer diameter of the impeller 4 and the outlet of the diffuser 7 is brought to the design flow angle, the secondary flow from the coreboard 3 side to the sideboard 2 side is suppressed and decelerated smoothly thus to reduce the overall pressure loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a diffuser for a centrifugal fluid machine, and particularly to a diffuser suitable for a large flow rate centrifugal compressor.

[Background of the invention]

A bladeless diffuser used in a conventional centrifugal compactor will be explained with reference to FIGS. 3 and 4. As shown in FIG. 3, a centrifugal impeller 4 consisting of blades 1, side plates 2, and core plate 3 is rotated by a drive machine (not shown) attached to a rotating shaft 5, so that fluid is While passing through the suction pipe 6 and inside the impeller 4, it is given energy and becomes a high-speed flow, flowing into the diffuser 7. The diffuser 7 is composed of a pair of opposing core diffuser plates 8 and side diffuser plates 9, with a flow path formed therebetween. In the diffuser 7, the fluid flowing out from the impeller 4 flows into the scroll casing 10 while its velocity energy is converted into pressure energy. Therefore, the fluid whose velocity energy has been further converted into pressure energy forms a flow that is collected by the scroll casing 10 and flows out from a discharge port (not shown). As shown in the experimental results in No. 4 @, the flow angle α2 taken from the circumferential direction of the exit flow of a centrifugal impeller of a large flow type, that is, a high specific speed, and the radial velocity component C of the absolute velocity are The distribution is greatly distorted from the side to the core plate 3 side. This tendency becomes more pronounced toward the diffuser outlet (rl-
+r2 → r3) becomes stronger and stronger. This is side plate 2
The fluid on the side gradually loses momentum because the flow angle α is smaller than the design flow angle α, and the radial velocity component CII+ becomes very small. This is because the flow on the side plate 2 side becomes reverse flow, and a secondary flow from the side plate 2 side toward each plate 3 side occurs.

As mentioned above, in conventional centrifugal fluid mechanical diffusers, the flow immediately after the impeller exit has a distorted distribution in the width direction of the flow path of the diffuser, which makes it difficult to convert kinetic energy into pressure energy in the diffuser. In combination with not being done enough, exposure (due to reflux)
There was a drawback that fluid performance deteriorated due to increased pressure loss due to the IC.

As a method to solve this drawback, the distorted flow in the width direction of the dip user flow path immediately after the impeller exit is made uniform by the effect of the low-height guide vanes 11 attached to the side of the guard plate 2. However, as shown in the experimental results in Fig. 6(a), after the impeller's outer diameter exceeds 1.2 to 1.3 times, the deceleration on each plate 3 side becomes too large, and the -resistance becomes too large. The disadvantage is that the distorted flow will have a strain with a tendency opposite to that at the impeller outlet. Figure 6(b) shows the radial velocity C when the flow immediately after the impeller exit smoothly decelerates.
This shows the change in l1l.

[Purpose of the invention]

The purpose of the present invention is to uniformize the distorted flow in the width direction of the flow path at the entrance of the diffuser by controlling the secondary flow in the width direction of the flow path in the diffuser, and to smoothly decelerate the flow while maintaining this state. An object of the present invention is to provide a high-performance diffuser for a centrifugal fluid machine in which the pressure loss within the diffuser is reduced and the velocity at the diffuser outlet is reduced by tJs to obtain a large pressure recovery.

[Summary of the invention]

The diffuser of the centrifugal fluid machine of the present invention has a plurality of guide vanes having a height of 1/3 to 115 times the width of the diffuser flow path and extending in the flow direction in the flow path, and the diffuser plate on the side plate side has a plurality of guide vanes arranged at the impeller outlet. From immediately afterward to the rear position of 162 to 1.3 times the outer diameter of the impeller, each diffuser plate has a diameter of 162 to 1.3 times the outer diameter of the impeller.
．． It is provided from the rear position of 2 to 1.3 times to the diffuser exit diameter position.

According to the above configuration, not only the fluid flow angle and radial velocity component on the side plate side are forcibly increased, but also the fluid flow angle on each plate side is forcibly held at an arbitrary angle. Therefore, the fluid on the side plate side can overcome the pressure gradient of the diffuser and flow, and the fluid on each plate side can also overcome the pressure gradient of the diffuser and flow from the rear position 1.2 to 1.3 times the outer diameter of the impeller. From the board side to the side board side 2
Next flow can be prevented. Therefore, the flow can be decelerated while maintaining uniformity in the width direction of the flow path.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1, a centrifugal impeller 4 consisting of blades 1, side plates 2, and core 3 is rotated by a drive machine (not shown) attached to a rotating shaft 5, so that fluid is sucked in. While passing through the pipe 6 and inside the impeller 4, it is given energy and becomes a high-speed flow that flows into the diffuser 7, as in the conventional case.

A plurality of guide vanes with a height of 1/3 to 115 mm of the flow path width of the diffuser 7 are arranged on the flow path surface of the side diffuser plate 9 from a position immediately behind the impeller to a height of 1.2 to 1 mm of the impeller outer diameter. It is attached to the flow path surface of the diffuser plate 8 on each plate side from a position 1.2 to 1.3 times the outer diameter of the impeller 4 to a position corresponding to the diffuser outlet diameter.

As shown in FIG. 2, the inlet angle β3 of the guide vane 12 on the side plate side is set to a value smaller than the flow angle αi at the design flow rate point.

The outlet angle β4 is made approximately equal to the design flow point flow angle αi. The change from flow angle β3 to β4 is approximated and connected by a curve such as a circular arc or a logarithmic spiral so as to be smooth.

Further, the inlet angle β5 and the outlet angle β6 of the guide vane 13 on the core plate side are approximately equal to the design flow point flow angle αi, that is, β4.

With this structure, when a distorted flow flows from the impeller 4 in the width direction of the diffuser flow path into the diffuser 7, the fluid on the side plate 2 side where the flow angle α2 is small is forcibly blocked by the guide vanes 12. By creating the flow angle α2, the radial velocity component becomes large and has enough momentum to overcome the radial pressure gradient of the diffuser 7, so the fluid on each plate 3 side flows into the side plate 2 side. The distorted flow gradually becomes uniform and decelerates smoothly to a position of 1.2 to 1.3 times the outer diameter of the impeller. Moreover, the guide vane 13 is 1 of the outer diameter of the impeller.
．． Since the fluid flow angle on each plate 2 side from the 2 to 1.3 times the position to the diffuser outlet is forced to be guided to the designed flow angle α, the secondary flow from each plate 3 side to the side plate 2 side is forced. Flow is restricted.

Therefore, smooth deceleration is achieved from a position 1.2 to 1.3 times the blade outer diameter to the diffuser outlet diameter.

〔Effect of the invention〕

As described above, according to the present invention, fluid backflow (backflow) within the diffuser is suppressed, smooth deceleration within the diffuser is achieved, total pressure loss is reduced, and sufficient pressure is maintained. Recovery will be obtained and the performance of the diffuser will be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a front view taken along the line A-A in FIG. 1, and FIGS. 3 and 5 are longitudinal sectional views of a conventional centrifugal fluid machine. 4 is a distribution diagram of the flow toward the diffuser shown in FIG. 3, and FIG. 6 is a distribution diagram of the flow toward the diffuser shown in FIG. 5.

Claims (1)

[Claims] In a diffuser in which a flow path is formed between a pair of diffuser plates provided on the outer periphery of an impeller of a centrifugal fluid machine, the diffuser has a height of 1/3 to 1/5 of the width of the diffuser flow path and extends in the flow direction within the flow path. A plurality of guide vanes are installed along the side diffuser plate from immediately after the impeller exit to 1.2 of the outer diameter of the impeller.
A centrifugal fluid machine characterized in that the core plate side diffuser plate is provided from a diameter position of 1.2 to 1.3 times the impeller outer diameter to a diffuser outlet diameter position. diffuser.