JPS6166899A - Return channel of centrifugal compressor - Google Patents

Abstract

PURPOSE:To improve efficiency by increasing the flow-passage width at the outlet than that at the inlet of the U-turn part of a return channel and installing a plurality of guide vanes lower than the flow-passage width along the inner wall of the U-turn part. CONSTITUTION:As for the U-turn part 8 of a return channel 10, the width of a flow passage is increased from the inlet to the outlet, and the width B5 of the flow passage at the outlet of the U-turn part 8 is increased larger than that at the inlet or the width B4 of the flow passage at the outlet at the outlet of a diffuser 7. Further, guide vanes 15 are installed onto the U-turn inner-wall side. Therefore, the U-turn part of the return channel can e operated as effective diffuser, and friction loss can be reduced, and the whole efficiency can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a configuration in which velocity energy given by an impeller is recovered by a diffuser, decelerated and pressurized, and unrecovered velocity energy is recovered by a return channel. Centrifugal pressure with! This relates to the return channel in one aircraft.

[Prior art]

Conventionally, in a multi-stage compressor having a return channel, as shown in FIG.

The impellers 1.
1” is compressor body 2, suction cover 5, middle body 6.6
They are housed in impeller chambers each partitioned by "6". Further, the outlet of the impeller 1 passes through the diffuser 7, and is further connected to the U formed by the middle body 6.6''.
The outlet of the impeller 1 is connected to the next stage impeller 1' through a return channel 10 consisting of a flow path in which a turn part 8 and a return vane 9 are arranged, and the outlet of the impeller 1 is connected to the swirl chamber 11 through a diffuser 7'. It is connected to

In the figure, 12 is a suction pipe 13 connected to the suction cover 5.
．． 13° indicates the sealing device of impeller 1 and 1°, respectively.

Such multi-stage pressure iii! The action of i is that the impeller 1 sucks fluid from the suction pipe 12, increases its pressure and gives it velocity energy, and then guides it to the diffuser 7 to decelerate and increase its pressure to recover the velocity energy.

However, in the diffuser 7, the velocity energy of the fluid is not sufficiently recovered and still has considerable velocity energy, and this residual velocity energy is further transferred to the U-turn section 8.
The air then reaches a return channel 10 consisting of a flow path provided with return vanes 9, is collected, is guided to the next stage of vanes, and further reaches a swirl chamber 11 via a diffuser 7''.

Generally, the width of the flow path of the diffuser 7 is narrow, and the fluid flows from the outlet of the diffuser 7 through the U-turn section 8 through the vane 9.
Until the population is reached, the flow path width of the U-turn section 8 is also changed to the differential user 7 in order to avoid sudden changes in speed or flow angle.
The flow path width Bs at the outlet of the U-turn portion 8 may be made equal to the flow path width B at the outlet, or the flow path width Bs at the outlet of the U-turn portion 8 may be made slightly wider, taking into consideration the filtration speed.

[Problem that the invention seeks to solve]

In such a configuration, the U-turn simply diverts the flow from 18
Since the flow path width of the return channel 10 is almost the same as the narrow flow path width of the diffuser 7, the flow path of the U-turn portion and the return channel is The friction loss was large, and the total pressure ti was considerably lost by the time it reached the inlet of the impeller 1' of the next stage, reducing the stage efficiency of the pressure mi.

Such a drawback is particularly noticeable in the case of an impeller having a small specific speed (the width of the flow path in the diffuser is narrow).

On the other hand, if the flow path width of the return channel is made wider than the diffuser width in order to reduce friction loss in the return channel, the flow path width will inevitably expand within the U-turn section, so as shown in Figure 2 ( As shown in a), BS>B
When set to a, the meridional velocity distribution will be biased towards the outer wall at the exit of the U-turn section, and the flow angle (angle with respect to the circumferential direction) will be as shown in Figure 2 (
As shown in b), it has been experimentally found that the distribution is small on the inner wall side and large on the outer wall side.

Now, when examining the pressure recovery rate Cp from the U-turn entrance to the exit, the subscript 4.5 is the U-turn population and exit, C is the absolute velocity, Cm is the meridional velocity, P is the static pressure, When P is the total pressure, ρ is the fluid 8 degrees, and the width of the U-turn streamline is B, the total pressure loss coefficient ξU and the pressure recovery coefficient Cp are respectively Cp/2)Ca''.By the way, Pv a −P, + (ρ/2)C4”Pr s −
Ps 10 (ρ/2) Cs ”tz ・Cm4-bs
・CmC m5C-C4S i na4 Cm, = Cs S i na.

Therefore, (here α4.α is the angle with respect to the circumferential direction at the inlet and outlet), therefore, ba 5 incr.

b, The smaller the value of Sinα5, the more the value of Cp increases by 319, and the U-turn portion operates as an effective diffuser.

As mentioned above, the flow at the exit of the U-turn section is biased toward the outside of the outer wall, and the flow angle is smaller on the inner wall side and larger on the outer wall side, so on the U-turn inner wall side, b 5 > b 4 and S in a duck < 3 in
α4, and on the other hand, on the U-turn outer wall side, <b, , S i na, > S i ncra
It becomes. Therefore, ba Sinα.

bs　　　　　　Sinα.

There is not much difference in the value between the U-turn inner wall and the outer wall.
In this state, the diffuser has the disadvantage that the flow angle at the U-turn exit, that is, the return vane population, is non-uniform, and simply setting the shape of the U-turn portion to Bs>84 does not result in an effective diffuser.

The present invention aims to solve such problems of the conventional ones, reduce the total pressure loss in the return channel, increase the efficiency of the return channel, and improve the membrane characteristics of the pressure mi.

[Means for solving problems]

As a means to solve the above problems, the present invention has a configuration in which the velocity energy given by the impeller is recovered by a diffuser to decelerate and pressurize the fluid, and the unrecovered velocity energy is recovered by a return channel. Centrifugal pressure 1iI8
1, the outlet flow path width of the U-turn portion in the return channel is made larger than the inlet flow path width to expand the flow path area of the U-turn portion, and the resulting uneven flow angle at the U-turn portion outlet is In order to correct this, we installed a guide vane with a collar that is lower than the channel width along the inner wall of the U-turn.
bz Sin
α.

bs 5 inct.

This increases the pressure increase within the U-turn.

With the above configuration, the U-turn section can be changed from the conventional simple flow to 18
It is now possible to operate not only as a channel that turns 0 degrees but also as an effective diffuser, and the width of the channel with return vanes in the return channel that will be installed later is also increased. The efficiency of the entire return channel can be improved.

〔Example〕

The embodiment of the present invention shown in FIGS. 3 and 4 will be described below.

What is shown in FIG. 3 is a single-stage pressure ms different from the multi-stage pressure 1liI machine shown as the prior art in FIG. 1, and the same reference numerals indicate the same parts. That is, the impeller 1 is attached to a drive shaft supported by a bearing and a sealing device 3 in the pressure 11 machine body 2, and is housed in an impeller chamber defined by the pressure 11 machine body 2 and the middle body 6. . Also, impeller 1
The outlet passes through the diffuser 7 and then the middle body 6.6”
The pressure! It is connected to an outlet provided in the cover 14 at the front end of 1a.

As shown in FIGS. 3 and 4(a), the U-turn portion 8 of the return channel 10 expands the flow path width from the inlet to the outlet, that is, the flow path width Bs at the outlet of the U-turn portion 8 is Alternatively, the flow path width B4 at the outlet of the diffuser 7 may be made larger than that, so that the flow path width of the U-turn section 8 increases continuously from the inlet to the outlet, thereby increasing the pressure of the fluid within the U-turn section. However, just by expanding the flow path width of the U-turn section 8, it is not possible to expect an increase in pressure on the inner wall side of the U-turn section as described above. By providing this, the flow angle of only the fluid in the U-turn IJ (IIJ) is forcibly turned and the pressure is increased.
It may be provided within a 90 degree range from the exit to the apex of the U-turn section 8, or within a 180 degree range from the exit to the inlet of the U-turn section 8, or between 90 degrees and 180 degrees from the exit. Either is fine.

Furthermore, since the purpose of providing the guide vane 15 is to turn the flow angle on the inner wall side of the U-turn section 8, its height does not need to be very high, and its angle (with respect to the meridian direction) is shown in Fig. 4. A-A in FIG. 4(a) shown in (b)
It is better to decrease from the inlet to the outlet, as shown in the figure, and it is meaningless to increase β at least.

〔Effect of the invention〕

As described above, the present invention expands the flow path area of the U-turn part in the return channel from the inlet side to the outlet side, and provides a guide vane that forces the flow along the inner wall of the U-turn part. By increasing the pressure on the inner wall of the turn section, it is possible to make the U-turn section of the return channel act as an effective dephasor, and the flow angle at the exit of the U-turn is made uniform. The flow path with return vanes also has a wider flow path, which reduces the velocity of the fluid and reduces friction losses, reducing the total pressure loss in the return channel as a whole, thus significantly improving compressor stage efficiency. can be achieved.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional side view of the conventional multi-stage pressure 'am, and Figure 2 (
a) is an explanatory diagram showing the flow state of the pressure 11a in the U-turn section of FIG. 1, FIG. 2(b) is a diagram showing the flow angle distribution at the inlet and outlet of the U-turn section, and FIG. FIG. 4(a) is a longitudinal cross-sectional side view of the single stage pressure w1m of the embodiment.
FIG. 4(b) is a longitudinal sectional side view of the U-turn portion of the compressor shown in FIG. 1, 1'...-impeller, 2- compressor main body, 3-
Bearing and sealing device, 4 Drive shaft, 5 Suction cover, 6.6°, 6"-middle barrel, 7.7"... Day phaser, 8... U-turn section, 9- Return vane , ]0...Return channel, 11-... Volute chamber, 12... Suction pipe, 13. +3” - sealing device,
14 -- Cover, 15- Guide vane, 8, : Dephasor outlet flow path width (U-turn part inlet flow path width) Bs : U-turn part outlet flow path width b Convergence α of two streamlines : Flow angle (circumferential direction ) β Guide vane angle (angle with respect to meridian direction)

Claims (1)

[Claims] 1. A centrifugal compressor having a configuration in which velocity energy given by an impeller is recovered by a diffuser to decelerate and pressurize the fluid, and further unrecovered velocity energy is recovered by a return channel. The outlet flow path width of the U-turn portion in the channel is made larger than the inlet flow path width to expand the flow path area of the U-turn portion, and a plurality of guides lower than the flow path width are provided along the inner wall of the U-turn portion. A return channel of a centrifugal compressor characterized by the provision of vanes. 2. The guide vane is provided over a range of 90 degrees to 180 degrees between the U-turn outlet and the inlet, and the outlet angle of the guide vane is smaller than the inlet angle. Return channel of the centrifugal compressor described in item 1.