JP3841391B2 - Turbo machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a turbomachine, and more particularly to a turbomachine capable of preventing flow instability by suppressing swirling due to recirculation flow at a blade inlet and blade swirling stall regardless of the type and fluid.
[0002]
More specifically, the present invention relates to a turbo machine such as a pump, a compressor, or a blower having a non-displacement type impeller, and in particular, suppresses pre-rotation and blade rotation stall in a positive flow of the recirculation flow at the blade inlet. The present invention relates to a turbo machine that can prevent flow instability and is suitable for a mixed flow pump or the like used as a circulating water pump, a drainage pump or the like in thermal power or nuclear power generation.
[0003]
[Prior art]
Rotating machines collectively referred to as turbomachines can be classified as follows according to the fluid and type to be handled.
[0004]
1. Fluid to handle
Liquid, gas
2. format
Axial flow, diagonal flow, centrifugal
For example, since it is easy to operate, the mixed flow pump that is currently used mainly includes a suction casing, a pump, a diffuser, and the like from upstream to downstream.
[0005]
An impeller that rotates within the casing of the pump is driven to rotate by a rotating shaft, and gives energy to the liquid sucked from the suction casing. The diffuser has a function of converting a part of the velocity energy of the fluid into a static pressure.
[0006]
A typical lift-flow rate characteristic curve (a horizontal axis is a parameter indicating a flow rate and a vertical axis is a parameter indicating a lift) of a turbomachine including the mixed flow pump is as follows. In other words, in the low flow rate region, the lift is lowered as the flow rate is increased, but while the flow rate is in a specific region, the lift characteristic is generally increased so that the lift increases as the flow rate is increased. In the region where the flow rate is higher than the characteristic region, the head decreases again as the flow rate increases.
[0007]
When the turbomachine is operated at a flow rate in the upwardly rising characteristic region, surging occurs in which a mass of fluid self-excites in the pipeline. This upward-rising characteristic is that when the flow rate of the fluid flowing through the turbomachine is low, a recirculation flow is generated at the outer edge of the impeller inlet. At this time, the flow path of the fluid entering the impeller is narrowed, and It is thought to occur because the fluid entering the impeller is swirled by the influence of the flow.
[0008]
Since surging damages not only turbomachines but also piping connected upstream and downstream, operation in low flow areas is usually prohibited. In addition, in order to improve the surging of the turbomachine and the above-mentioned right-up characteristic and to expand the operating range, the blade shape (profile) is improved, and the following method has been proposed.
[0009]
1. Casing treatment
The stall margin is improved by forming a narrow groove of 10 to 20% of the chord length of the blade in the casing region where the impeller exists. That is, the already proposed casing treatment forms a groove having a considerable depth in the axial direction, the circumferential direction, or the oblique direction in the radial direction or obliquely in the region where the blades on the inner wall of the casing are present. .
[0010]
2. Separator
A separator is disposed to separate the backflow portion of the recirculation flow generated at the blade inlet outer edge in the low flow region from the forward flow portion, thereby preventing the recirculation flow from expanding.
[0011]
Examples of the separator applied to the axial flow turbomachine include a suction ring method, a blade separator method, and an air separator method.
[0012]
The suction ring system confines the reverse flow outside the suction ring, and the blade separator system provides a fin between the casing and the ring. In addition, the air separator system opens the blade (blade) tip and guides the reverse flow to the flow path outside the casing and prevents the reverse flow from turning by the fins. However, the apparatus becomes large-scale.
[0013]
3. Active control
A high-pressure fluid is ejected from the outside to the location where the recirculation flow is generated in the vicinity of the blade inlet to suppress the swirling due to the recirculation flow.
[0014]
Further, a mixed flow pump will be described as an example of a conventional turbomachine. The head-flow characteristic curve (hereinafter referred to as the head curve) of the mixed flow pump is required to have a head-down characteristic that can be stably operated when the pump is operated in the entire flow rate range. However, in an ordinary pump, the efficiency representing the pump performance, the stability of the lift curve, the cavitation performance, the deadline shaft power, and the like are generally in a mutually contradictory relationship. That is, if one characteristic is improved, other characteristics are lowered, and at the same time, it is difficult to improve two or more characteristics. For example, pumps that place importance on efficiency tend to be unstable because the upward-sloping characteristics are prominent in part of the lift curve.
[0015]
As described above, it is already known to provide a casing treatment or a separator as a conventional technique for obtaining an upwardly rising head curve capable of stable operation. A known example of this type is described in US Pat. No. 4,212,585.
[0016]
In addition to this, a turbo that is provided with a plurality of grooves connecting the blade inlet side and the blade existing area on the casing inner surface on the inner surface of the casing so as to suppress the swiveling of the inlet and obtain a lift curve without a right-up characteristic. Machines have also been proposed.
[0017]
[Problems to be solved by the invention]
According to the above-mentioned casing treatment and separator of the prior art, although it is possible to move the above-mentioned rising characteristic of the lift curve to a lower flow rate side and expand the stable operation region, it is possible to eliminate the rising characteristic itself. It was difficult. In addition, the efficiency of the turbomachine decreases by 1% every time the stall margin is increased by 10% in the casing treatment.
[0018]
In the active control, it is necessary to obtain a high-pressure fluid from the turbomachine itself or from the outside, so that the efficiency of the turbomachine system is reduced.
Further, when a groove connecting the blade inlet side and the inside of the blade inner surface of the casing is formed, it is easy to process the groove, there is little reduction in efficiency, and a lift curve without a right-up characteristic can be obtained. However, when the blades pass through multiple grooves formed on the inner surface of the casing while rotating, pressure pulsation may occur due to interference between the flow from the blades and the grooves, which may increase vibration and noise. Is not considered.
[0019]
An object of the present invention is to obtain a turbo machine that has a lift-flow rate characteristic with improved right-up characteristics, can suppress a decrease in efficiency, and can also suppress an increase in vibration and noise.
[0020]
Another object of the present invention is to provide a turbo machine that has improved head-flow characteristics even for a turbo machine having a closed impeller, and that can suppress efficiency reduction and vibration / noise.
[0021]
[Means for Solving the Problems]
A first feature of the present invention for achieving the above object is a casing, an impeller provided in the casing and having a plurality of blades, an inner surface of the casing, and an inlet side of the impeller. A plurality of first grooves that communicate with the inside of the impeller on the inner surface of the casing; and a second groove that is provided on the inner surface of the casing and connects the plurality of first grooves in the circumferential direction. Is on the turbomachine.
[0022]
The width of the first groove is 5 mm or more, and the total of the plurality of first groove widths provided in the circumferential direction is about 30 to 50% with respect to the circumferential length of the casing inner surface where the groove exists, and the first groove It is more preferable that the depth of the groove is 2 mm or more and is about 0.5 to 1.6% of the inner diameter of the casing where the groove exists.
[0023]
It is better to provide the second groove in the impeller existing area on the inner surface of the casing. Preferably, the depth of the second groove is shallower than the depth of the first groove.
[0024]
Further, it is better to form the second groove from the turbo machine downstream end position of the first groove to the inside of the blade on the casing inner surface or the blade inlet side.
[0025]
A second feature of the present invention is provided with a plurality of grooves in a fluid pressure gradient direction that are provided on the inner surface of the casing and communicate with the inlet side of the impeller and the impeller existing area on the inner surface of the casing. The groove is from the vicinity of the blade inlet toward the downstream side of the turbomachine , Formed by bending from the axial direction to the impeller rotation direction Is.
[0026]
A third feature of the present invention is that a plurality of circumferentially arranged first grooves in the fluid pressure gradient direction are provided on the impeller inlet side of the casing inner surface, and a periphery provided in the blade existing area on the casing inner surface. A second groove in the direction and a flow path connecting the first groove and the second groove.
[0027]
The flow path is constituted by a groove, a hole, a pipe, a tube, or the like provided around the casing inner surface.
[0028]
According to a fourth aspect of the present invention, a plurality of circumferentially arranged first grooves in a fluid pressure gradient direction are provided on the impeller inlet side of the inner surface of the casing, and the blade existing area on the inner surface of the casing. A circumferential second groove, a circumferential third groove provided near the blade leading edge of the casing inner surface, and a flow path connecting the second groove and the third groove; The flow path is formed on an extension line of the first groove, bypassing the inner surface of the casing, and communicated with the first groove via the third groove.
[0030]
According to a sixth aspect of the present invention, in a turbomachine including a closed type impeller having a shroud and a casing for accommodating the impeller, the vicinity of a blade inlet of the impeller is configured to be an open type without a shroud, and the blade A plurality of first grooves in the pressure gradient direction are arranged on the inner wall of the casing facing the portion without the shroud near the inlet, and the inlet side starting end of the first groove is from the blade tip inlet side of the impeller. On the upstream side, the outlet end of the first groove is disposed downstream of the impeller tip inlet portion, and a second groove connecting the plurality of first grooves in the circumferential direction is provided on the shroud near the blade inlet. This is because it is provided on the inner wall of the casing facing the non-existing portion.
[0031]
A seventh feature of the present invention is that a first groove that connects a low flow rate recirculation flow generation position on the blade inlet side and a blade tip existing area on the casing inner surface in a gradient direction of fluid pressure is formed in a circumferential direction on the inner surface of the casing. And a turbomachine downstream end position of the first groove is a fluid having a pressure required to suppress the occurrence of pre-swirl in the main inlet of the turbomachine upstream end position of the first groove. And a second groove that connects the first groove in the circumferential direction is provided on the inner surface of the casing near the blade inlet, and the portion of the casing where the first and second grooves are installed is the other part of the casing. It is in being configured separately from the part.
[0032]
According to the present invention, the second groove in which a part of the first groove is continuous in the circumferential direction at a depth shallower than, equal to, or greater than the depth of the first groove in the blade existence area of the groove. By reducing the pressure pulsation caused by interference between the groove and the flow from the impeller when the blade passes through the groove in the pressure gradient direction, the increase in vibration and noise caused by the pressure pulsation is suppressed. Can do.
[0033]
Also, the flow from the impeller and the groove can be obtained by inclining the groove (first groove) from the vicinity of the impeller inlet portion to the downstream side of the turbomachine in the rotation direction of the impeller (curving in the direction opposite to the bending of the impeller). Interference can be mitigated.
[0034]
Furthermore, the first groove in the pressure gradient direction extends to the blade inlet and is configured not to overlap the second groove in the circumferential direction, which is necessary to suppress the occurrence of pre-swirl during the inlet main flow (positive flow). The same effect can be obtained even if the circumferential groove and the groove formed in the pressure gradient direction are communicated with each other so that a fluid having a proper pressure can be taken out. The two grooves are preferably connected by a flow path provided on the outer peripheral side of the casing, avoiding the inner surface of the casing through which the mainstream flows. Thus, it is possible not to provide a groove in the pressure gradient direction in the blade existing area on the inner surface of the casing, and to reduce interference between the fluid from the impeller and the groove. The flow path connecting the first groove and the second groove is preferably formed on the extended line of the first groove so that a fluid reversing the main flow flows into the blade inlet side.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
[0036]
FIG. 1 shows a first embodiment of the present invention. The figure is an enlarged cross-sectional view of an impeller portion of a mixed flow pump, which is a typical example of a turbomachine. Reference numeral 1 denotes an open type impeller provided with open blades 22. A shallow groove (first groove) 24 in the direction of the fluid pressure gradient is formed on the inner surface of the casing 2 near the outer peripheral side inlet portion of the blade 22 in order to suppress the occurrence of recirculation flow due to the backflow from the blade at the blade inlet portion. Many are formed in the circumferential direction. The turbo machine downstream end position a of the groove is in the blade existence area, and a position b where a part of the fluid pressurized by the impeller is recirculated through the groove 24 at a low flow rate upstream of the turbo machine. To guide you to. As a result, since the pressurized fluid on the downstream side is ejected to a place where recirculation flow is likely to occur, the occurrence of recirculation flow can be suppressed, and the main flow at the turbomachine inlet becomes swirling flow due to the recirculation flow. Since it can be suppressed, it is possible to realize a high-performance turbomachine that prevents the occurrence of blade rotation stall.
[0037]
Further, in the present embodiment, the second groove 25 is provided on the inner surface of the casing so as to make the portion corresponding to the blade existing area of the plurality of first grooves 24 provided in the circumferential direction continue in the circumferential direction. When the second groove 25 is not provided, when the blade 22 passes through the groove 24 due to the rotation of the impeller, the flow from the first groove 24 formed in the axial direction (pressure gradient direction) and the impeller 1 interferes. It was found that pressure pulsation occurred. The generated pressure pulsation vibrates the turbomachine and increases vibration and noise. In the present embodiment, the second groove 25 in the circumferential direction is provided in the blade existing area, so that the pressure difference between the first grooves 24 formed in the circumferential direction is reduced in the second groove 25, The pressure pulsation generated by the first groove 24 and the blade 22 can be reduced, and the increase in vibration and noise due to the pressure pulsation can be suppressed.
[0038]
FIG. 2 is a diagram showing a head-flow rate characteristic curve and an efficiency-flow rate characteristic curve of the turbomachine, in which the horizontal axis represents a non-dimensional flow rate and the vertical axis represents a non-dimensional head. In the figure, white circles are a head-flow characteristic curve and an efficiency-flow characteristic curve of a turbomachine that does not form the first groove 24 on the inner surface of the casing. The black circles indicate the lift-flow rate characteristic curve and the efficiency-flow rate characteristic curve in the turbomachine having the first groove. The white triangles show the lift-flow rate characteristic curve and the efficiency-flow rate characteristic curve in the turbo machine in which the first groove 24 and the circumferential second groove 25 are formed near the end position a of the groove 24 on the downstream side of the turbo machine. .
[0039]
As is apparent from FIG. 2, in the case of the white circle, there is a right-up characteristic in which the lift increases with an increase in the flow rate when the non-dimensional flow rate is in the range of 0.5 to 0.6. In the case of a black circle, the right-up characteristic is eliminated. Also in the white triangle which is the present embodiment, the same effect as the black circle is confirmed.
[0040]
FIG. 3 is a diagram showing the relationship between the flow rate and vibration acceleration of the turbomachine. White circles, black circles, and white triangles are the same turbomachinery data as in FIG. In the figure, the horizontal axis represents the non-dimensional flow rate, and the vertical axis represents the non-dimensional vibration acceleration. As is apparent from FIG. 3, in the case of the black circle having the first groove, the vibration acceleration has a peak at a non-dimensional flow rate of about 0.5 to 0.6, compared with the case of the white circle, It can be seen that the vibration increases compared to the case of the white circle over the entire range. On the other hand, in the case of the white triangle having the first and second grooves, the vibration acceleration is greatly improved as compared with the black circle, and the vibration acceleration at a dimensionless flow rate of about 0.5 to 0.6 is obtained. It can be seen that there is no peak and the vibration is greatly improved.
[0041]
FIG. 4 is a diagram showing the relationship between the flow rate of the turbo machine and the noise level. White circles, black circles, and white triangles are the same turbo machine data as in FIG. In the figure, the horizontal axis represents the non-dimensional flow rate, and the vertical axis represents the non-dimensional noise level. As is apparent from FIG. 4, the noise level is increased in the case of the black circle as compared with the case of the white circle. In contrast to the black circle having only the first groove, in the case of the white triangle having the first and second grooves (this embodiment), no groove is formed in the casing in the high flow rate range which is the main operating range. It can be seen that the noise level has been greatly reduced to around the same level as the case (white circle).
[0042]
In the embodiment shown in FIG. 1, the circumferential second grooves 25 are shallower than the depth d of the first grooves 24 in the pressure gradient direction, and a large number of first grooves formed in the circumferential direction are formed. All or some of them are communicated in the circumferential direction.
[0043]
The depth of the second groove 25 in the circumferential direction may be equal to the depth d of the first groove 24 in the pressure gradient direction, or may be greater than the first groove depth d.
[0044]
Further, in the example of FIG. 1, the formation position of the second groove 25 in the circumferential direction is from the vicinity of the front edge C of the blade 22 to the position slightly upstream from the groove end position a toward the downstream side of the turbomachine. However, the second groove 25 may be formed from the vicinity of the front edge C of the blade 22 to the end position a of the groove toward the downstream side of the turbomachine (see the dotted line 25a). Further, as shown in FIG. 5, the second groove 25 may be provided in the blade existence area from the groove end position a to a slightly upstream side thereof, and as shown by a dotted line 25b, the end of the groove may be provided. You may form from the position a to the upstream of a turbomachine rather than the front edge C of the blade | wing 22. FIG.
[0045]
FIG. 6 is a developed view of the inner surface of the casing shown in FIG. 1. As shown in this figure, the second groove 25 in the circumferential direction is a plurality of first grooves 24 formed in the circumferential direction in the pressure gradient direction. All of these are communicated in the circumferential direction. As shown in FIG. 7, the circumferential second grooves 25 are intermittently arranged in the circumferential direction so that some of the first grooves 24 formed in the circumferential direction are in communication with each other. Several may be formed. Further, as shown in FIG. 8, the second groove 25 in the circumferential direction starts from the vicinity of the blade inlet portion so that the first grooves 24 in the pressure gradient direction communicate with each other in the circumferential direction. You may form helically to the terminal position a.
[0046]
Next, a second embodiment of the present invention will be described with reference to FIG.
[0047]
This embodiment is also the same as the first embodiment in that a plurality of grooves 24 in the pressure gradient direction (axial direction) communicating the blade inlet side and the blade existing area on the inner surface of the casing are provided. In this embodiment, the portion (downstream side of the blade) corresponding to the blade existing area of the groove 24 is further inclined (curved) in the impeller rotation direction as shown in the drawing. With this configuration, the interference between the blades 22 and the grooves 24 can be moderated, the occurrence of pressure pulsation can be reduced, and the increase in vibration and noise can be suppressed. The upstream side of the blade of the groove 24 is in the axial direction, and the fluid whose pressure has been increased by the blade flows backward through the groove 24 toward the impeller inlet side to the place where the recirculation flow generated at the low flow rate occurs. By ejecting, it is possible to suppress the swirl flow and blade swirl stall caused by the recirculation flow, thereby eliminating or reducing the upward rising characteristic in the lift-flow rate characteristic curve of the turbomachine.
[0048]
FIG. 10 is a diagram showing a third embodiment of the present invention. (A) of a figure is an expanded view of a casing inner surface, (b) is AA sectional drawing (meridian plane sectional drawing) of (a).
[0049]
A plurality of first grooves 24 in the axial direction (fluid pressure gradient direction) connecting the inlet side of the impeller and the inside of the impeller are formed on the inner surface of the casing 2 in the circumferential direction. A second groove 25 that is partially continuous in the circumferential direction is formed on the inner surface of the casing. Further, a flow path 27 is formed around the inner surface of the casing so as to communicate the first groove 24 and the second groove 25. The flow path 27 exists on the extended line of the groove 24, and a part of the fluid pressurized by the blade 22 through the second groove 25 and the flow path 27 flows into the first groove 24, and the recirculation flow on the blade inlet side It is ejected to the place of occurrence. As a result, as in the above-described embodiment, it is possible to eliminate or reduce the right-up characteristic in the lift-flow rate characteristic curve of the turbomachine.
[0050]
Further, since no axial groove is formed on the inner surface of the casing in the impeller existing area, there is no flow interference when the blade passes through the first groove, and the plurality of first grooves 24 are formed by the second groove 25. Since the pressure difference between them is also reduced, an increase in vibration and noise due to pressure pulsation can be suppressed.
[0051]
A specific example for realizing the structure of the third embodiment is shown in FIG. (A) of the figure is a developed view of the inner surface of the casing, (b) is a cross-sectional view taken along the line AA of (a) (cross-sectional view of the meridian surface), and (c) is a cross-sectional view taken along the line BB of (a) Indicates.
[0052]
The casing is divided into three parts in the axial direction as indicated by 28, 29 and 30. (Here, the casings 28 and 29 may be integrated or the casings 29 and 30 may be integrated.) The axial direction connecting the inner surface of the casing 28 from the blade inlet side to the blade leading edge c ( (Gradient direction of fluid pressure) A plurality of grooves 24 are formed in the circumferential direction. Further, an annular member (casing) 31 is fitted to the inner peripheral side of the casing 29, and a circumferential second groove 25 is formed by the turbomachine downstream end surface of the annular member 31 and the end surface of the casing 30. . A flow path 27 is formed on the back side of the annular member 31 so as to communicate the first groove 24 and the second groove 25. As shown in (c), the annular member 31 can be fixed to the inner surface of the casing 29 by joining the inner surface of the casing 29 and the outer peripheral surface of the portion where the groove of the annular member 31 is not formed.
[0053]
Next, a modification of the embodiment shown in FIG. 10 is shown in FIG. A different point from FIG. 10 is that the flow path 32 provided by bypassing the inner surface of the casing is constituted by a pipe or a tube. As a result, the fluid pressurized by the blades flows back to the first groove 24 via the second groove 25 and the flow path 32 and is ejected to the recirculation flow generation location on the blade inlet side.
[0054]
Another modification of the embodiment shown in FIG. 10 is shown in FIG. (A) of a figure is an expanded view of a casing inner surface, (b) is AA sectional drawing of (a).
[0055]
A difference from FIG. 10 is that a third circumferential groove 33 that communicates in the circumferential direction a plurality of first axial grooves 24 formed in the circumferential direction on the inner surface of the casing at the front edge portion c of the blade 22. This is provided separately from the two grooves 25. The second groove 25 and the third groove 33 are communicated with each other through the flow path 27, and the fluid pressurized by the blade 22 is supplied to the first groove 24 through the second groove 25, the flow path 27, and the third groove 33. It is the composition which flows into.
[0056]
Pressure pulsation caused by interference when the blades 22 pass through the first groove 24 alleviates the pressure difference between the first grooves 24 provided in the circumferential direction by the second grooves 25 and the third grooves 33. In addition, the increase in vibration and noise of the turbomachine due to pressure pulsation can be suppressed.
[0057]
A fourth embodiment of the present invention will be described with reference to FIG.
[0058]
In this embodiment, a plurality of deep grooves 24 in the fluid pressure gradient direction are formed on the inner surface of the casing 2 to communicate the inlet side of the impeller 1 and the impeller existing area on the inner surface of the casing. The movable member 34 having a thickness smaller than the groove depth is provided to be movable in the radial direction (vertical direction). The movable member 34 is configured to have the same curved surface as the curved surface of the inner surface of the casing 2.
[0059]
By adopting the structure of this embodiment, the movable member 34 is moved in the outer diameter direction as shown in FIG. 14A in the operation region where the upward rising characteristic of the lift-flow rate characteristic curve of the turbomachine occurs. The shallow groove 24 in the axial direction is formed on the inner surface of the casing. Due to the shallow groove 24, a part of the fluid pressurized by the blade 22 passes through the groove 24, flows backward to the main flow, and is ejected to the region where the recirculation flow is generated at the blade inlet. Generation of swirling flow and blade swirling stall can be suppressed, and the right-up characteristic of the lift-flow rate characteristic curve of the turbomachine can be eliminated or reduced.
[0060]
Further, in the operating region where the upward-rising characteristic of the lift-flow rate characteristic curve does not occur, as shown in FIG. 14B, the movable member 34 is moved in the inner diameter direction so that the inner surface of the movable member coincides with the inner surface of the casing. Thus, the shallow groove 24 is not present. By doing so, in the operation region where the upward ascending characteristic does not occur, since there is no groove on the inner surface of the casing, there is no fluid interference between the blade and the axial groove, and pressure fluctuation can be eliminated.
[0061]
Thus, according to the present embodiment, there is an effect that vibration and noise generated due to the influence of the axial groove can be eliminated in the entire flow rate range.
[0062]
FIG. 15 shows an example in which the first embodiment of the present invention shown in FIG. 1 is applied to a turbomachine using a closed type impeller having a shroud in the impeller (for example, a closed type mixed flow pump). 16 is a cross-sectional view taken along line XIII-XIII in FIG.
[0063]
The closed type impeller 1 is provided with a shroud 1a. The shroud 1a is not provided near the entrance 1c of the blade, and the impeller is a semi-open type impeller having a portion without the shroud. A mouth ring portion 1b is provided on the innermost diameter side portion of the shroud, and a casing ring 5 is provided on the inner surface of the stationary casing 2 opposite to the mouth ring portion 1b. A rotary shaft sealing portion is configured between the mouth ring portion 1 b and the casing ring 5. As shown in FIGS. 15 and 16, a plurality of first axial grooves 24 in the circumferential direction are provided at equal intervals on the inner periphery of the casing inner surface 2a facing the blades in the portion near the blade inlet 1c without the shroud. The book is arranged. The turbomachine downstream end position a of the groove exists up to a position slightly downstream from the blade leading edge (position close to the mouth ring portion 1b near the blade inlet 1c), and the turbomachine upstream end position b of the groove 24 Is located upstream of the blade leading edge of the impeller. The portion 2g of the casing 2 facing the shroud end surface 1d of the impeller is configured in the axial direction substantially at the same position as the downstream end position a of the groove 24, and is configured in a plane perpendicular to the axis. The surface (part) 2g and the shroud end surface 1d face each other with a gap of δ1 in the axial direction. 25 is a second groove in the circumferential direction formed in the vicinity of the blade existing area of the first groove 24 in the axial direction, and this groove 25 communicates with a plurality of first grooves formed in the circumferential direction. It is constructed in a shallower groove.
[0064]
When the turbo machine (pump) is operated in a low flow rate region, a recirculation flow (back flow) 6 is generated as shown in FIG. In the present embodiment, due to the above configuration, a part of the flow boosted by the impeller flows backward in the first groove 24 from the downstream end position a to the upstream end position b. Since the groove 24 is formed in the direction of the pump shaft, the fluid flowing through the groove is ejected to the location where the recirculation flow is generated at a low flow rate without having a component in the impeller rotation direction, thereby weakening the recirculation flow or As a result, the generation of the recirculation flow is suppressed. Therefore, it is possible to prevent or suppress the occurrence of pre-swirl flow and blade swirl stall that occur on the impeller inlet side due to recirculation flow, and the decrease in the theoretical lift is reduced, and the flow rate-head characteristic curve of turbomachinery is increased to the right. Can be improved.
[0065]
Further, the pressure pulsation due to the interference generated when the blades 22 pass through the axial groove 24 is relieved by the presence of the second groove 25, and the pressure difference between the grooves 24 can be relieved. It is possible to suppress the vibration and noise from being increased.
[0066]
Although the above-described embodiment has mainly described an example of a mixed flow pump, the present invention is similarly applied to a turbo machine such as a centrifugal pump having an open impeller or a closed impeller, a mixed flow blower, and a mixed flow compressor. Can be applied to.
[0067]
Further, as shown in FIG. 17, the cross-sectional shape of the groove 24 in the axial direction (fluid pressure gradient direction) provided on the inner surface of the casing is not only a rectangular cross-section but also a cross-sectional shape such as a chevron cross-section, a round cross-section, and a trapezoidal cross-section. You may comprise. The circumferential grooves 25 and 33 can also have the same groove cross-sectional shape.
[0068]
The operating flow rate of the pump is determined as the intersection of the actual lift determined as the difference between the suction-side water level and the discharge-side water level of the pump station, and the resistance curve determined by summing up the pipe resistance of the pump station and the pump lift curve. In pumps that emphasize efficiency, when the maximum efficiency flow rate is set to 100% flow rate, a characteristic that rises to the right appears in a part of the flow rate-lift characteristic curve near 50 to 70% flow rate, or 50 to 70% flow rate. Even if it did not rise to the right in the vicinity, there was a tendency for a flat part to occur in the lift curve. In particular, if there is a region that rises to the right in the lift curve, there may be a plurality of intersections between the lift curve and the resistance curve, and the pump discharge amount fluctuates and becomes unstable. This tendency is remarkable when the actual head is high and the pipe resistance is small.
[0069]
Conventionally, the maximum efficiency and the stability of the head are balanced so that the head curve does not rise to the right, so the maximum efficiency tends to decrease. In addition, when the pump has an unstable region, the operating range of the pump must be a range in which instability does not occur, and the operating range is narrow. For this reason, when one pump enters an unstable region, it is necessary to take measures such as reducing the pump capacity and increasing the number of pumps. By adopting the present invention described above, these conventional problems can be solved. Furthermore, in the present invention, by providing the circumferential groove, it is possible to reduce the occurrence of pressure pulsation caused by interference between the axial groove and the flow from the impeller, and the pressure pulsation vibrates the pump, and the pump body and piping. Vibration and noise can be reduced. Therefore, according to the present invention, there is an effect that a high-performance turbo machine having no right-up characteristic can be employed in a pump station near a residential area.
[0070]
The present invention has a great effect when applied to a mixed flow pump. Especially when the rotational speed is N (rpm), the total head is H (m), and the discharge amount is Q (m3 / min), The specific speed Ns, which is an index indicating the characteristics,
Ns = N × Q0.5 / H0.75 = 1000 to 1500
It has a particularly remarkable effect when applied to those.
[0071]
Further, the present invention is particularly effective when applied to a pump in which the actual head determined by the suction water level and the discharge water level of the pump station to which the pump is applied is 50% or more with respect to the pump specification point head.
[0072]
【The invention's effect】
According to the present invention, a plurality of first grooves that communicate between the inlet side of the impeller and the impeller existing area on the inner surface of the casing, and the second grooves that connect the plurality of first grooves in the circumferential direction. Therefore, it is possible to obtain a turbo machine that has a lift-flow rate characteristic with improved right-up characteristics, can suppress a decrease in efficiency, and can also suppress an increase in vibration and noise.
[0073]
It is to be noted that the same effect as described above can be obtained by providing a plurality of grooves in the fluid pressure gradient direction and a movable member provided so as to be movable in the radial direction inside the grooves and capable of changing the depth of the grooves. be able to.
[0074]
Further, according to the present invention, a turbo machine having the same effect as described above can be obtained by providing a semi-open type structure without a shroud only in the vicinity of the blade inlet even for a turbo machine having a closed type impeller having a shroud. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a meridional cross-sectional view of a main part of a turbomachine showing a first embodiment of the present invention.
FIG. 2 is a diagram showing a head-flow characteristic curve and an efficiency-flow characteristic curve of a turbomachine.
FIG. 3 is a diagram showing the relationship between the flow rate of a turbo machine and vibration acceleration.
FIG. 4 is a diagram showing a relationship between a flow rate of a turbo machine and a noise level.
FIG. 5 is a meridional cross-sectional view of a main part of a turbomachine showing a modification of the embodiment shown in FIG. 1 of the present invention.
6 is a developed view of the inner surface of the casing shown in FIG. 1. FIG.
7 is an inner surface development view of a casing showing a modification of the example shown in FIG.
8 is an inner surface development view of a casing showing another modification of the example shown in FIG. 6. FIG.
FIG. 9 is an inner surface development view of a casing showing a second embodiment of the present invention.
FIGS. 10A and 10B are views showing a third embodiment of the present invention, in which FIG. 10A is an exploded view of the inner surface of the casing, and FIG. 10B is a cross-sectional view taken along the line AA in FIG.
FIGS. 11A and 11B are diagrams showing a specific example that realizes the structure of the third embodiment of FIG. 10, in which FIG. 11A is an exploded view of the inner surface of the casing, and FIG. 11B is a sectional view taken on line AA in FIG. ), (C) are BB cross-sectional views (meridional cross-section) of (a).
12 is a meridional cross-sectional view of a main part of a turbo machine showing a modification of the embodiment shown in FIG.
13A and 13B are views showing another modification of the embodiment shown in FIG. 10, in which FIG. 13A is a developed view of the casing inner surface, and FIG. 13B is a sectional view taken along line AA of FIG.
14A and 14B are meridional cross-sectional views showing a fourth embodiment of the present invention, in which FIG. 14A shows a state in which the movable member 34 is moved in the outer diameter direction, and FIG. 14B shows the movement of the movable member in the inner diameter direction. It is a figure which shows the state made to do.
FIG. 15 is a meridional cross-sectional view of the main part showing an example in which the first embodiment of the present invention shown in FIG. 1 is applied to a turbomachine using a closed impeller having a shroud in the impeller.
16 is a cross-sectional view taken along line XIII-XIII in FIG.
FIG. 17 is a cross-sectional view showing various examples of cross-sectional shapes of grooves formed on the inner surface of the casing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Impeller, 1a ... Shroud, 2 ... Casing, 22 ... Blade, 24 ... 1st groove | channel (pressure gradient direction or axial groove), 25 ... 2nd groove | channel (circumferential groove | channel), 27 ... Current Road 31, annular member (casing) 32, flow path (pipe or pipe), 33 third groove (circumferential groove)

Claims (15)

  A casing, an impeller having a plurality of blades provided in the casing, and a plurality of first blades provided on the inner surface of the casing and communicating between the inlet side of the impeller and the impeller existing area on the inner surface of the casing. A turbomachine comprising a groove and a second groove provided on an inner surface of the casing and connecting the plurality of first grooves in a circumferential direction.   2. The width of the first groove according to claim 1, wherein the total width of the plurality of first grooves provided in the circumferential direction is about 30 to 50% with respect to a circumferential length of the casing inner surface in which the groove exists. And the depth of the first groove is 2 mm or more, and the turbomachine in which the first groove is formed to be about 0.5 to 1.6% of the inner diameter of the casing in which the groove exists .   3. The turbomachine according to claim 1, wherein the second groove is provided in an impeller existing area on the inner surface of the casing.   4. The turbomachine according to claim 1, wherein a depth of the second groove is shallower than or equal to the depth of the first groove. 5.   The turbomachine according to claim 1, wherein a depth of the second groove is deeper than a depth of the first groove.   6. The turbomachine according to claim 1, wherein a plurality of the second grooves are formed intermittently in the circumferential direction.   7. The turbomachine according to claim 1, wherein the second groove is formed from a blade leading edge position on the inner surface of the casing or the vicinity thereof to a blade existing area or a terminal position of the first groove.   The second groove according to any one of claims 1 to 6, wherein the second groove is formed from a turbo machine downstream end position of the first groove to a blade existing area or a blade inlet side of the casing inner surface. Turbo machine.   The turbomachine according to any one of claims 1 to 6, wherein the second groove is spirally wound on an inner surface of the casing from a blade inlet side to a turbo machine downstream end position of the first groove. . A casing, an impeller having a plurality of blades provided in the casing, and a plurality of fluid pressure gradient directions provided on the inner surface of the casing and communicating between the inlet side of the impeller and the impeller existing area of the casing inner surface The groove in the fluid pressure gradient direction is formed by bending from the direction parallel to the axis to the impeller rotation direction from the vicinity of the blade inlet portion toward the downstream side of the turbomachine. Turbo machine.   A casing, an impeller provided in the casing and having a plurality of blades; a plurality of first grooves in a fluid pressure gradient direction provided in a circumferential direction on the impeller inlet side of the casing inner surface; and the casing A turbomachine comprising: a second groove in a circumferential direction provided in the blade existing area on an inner surface; and a flow path connecting the first groove and the second groove.   12. The turbomachine according to claim 11, wherein the flow path is any one of a groove, a hole, a pipe, or a tube that is provided around the inner surface of the casing.   A casing, an impeller provided in the casing and having a plurality of blades; a plurality of first grooves in a fluid pressure gradient direction provided in a circumferential direction on the impeller inlet side of the casing inner surface; and the casing A circumferential second groove provided in the blade existing area on the inner surface, a circumferential third groove provided near the blade leading edge on the casing inner surface, the second groove, and the third groove A flow path connecting the grooves, the flow path is formed on an extension line of the first groove, bypassing the inner surface of the casing, and communicated with the first groove via the third groove. Turbo machine characterized by.   In a turbomachine including a closed type impeller having a shroud and a casing for accommodating the impeller, a portion near the blade inlet of the impeller is configured as an open type without a shroud, and is opposed to a portion without the shroud near the blade inlet. A plurality of first grooves in the pressure gradient direction are arranged on the circumference of the inner wall of the casing, and the inlet end of the first groove is located upstream from the blade tip inlet side of the impeller. The exit end is located downstream from the impeller tip inlet, and the second groove connecting the plurality of first grooves in the circumferential direction is provided on the inner wall of the casing facing the shroud-free portion near the blade inlet. A turbomachine characterized by that.   In a turbomachine including an impeller and a casing that accommodates the impeller, a low-flow recirculation flow generation place and an inner surface of the casing on the inner surface of the casing facing the outer peripheral portion of the impeller blade on the inlet side A plurality of first grooves are formed in the circumferential direction to connect the inside of the blade tip existing area in the direction of the fluid pressure gradient, and the turbomachine downstream end position of the first groove is the turbomachine upstream end position of the first groove The second groove for connecting the first groove in the circumferential direction is formed on the inner surface of the casing near the blade inlet. A turbomachine characterized in that a portion of the casing in which the first and second grooves are provided is configured separately from other portions of the casing.

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