JP4100030B2 - Centrifugal compressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air supply device for a supercharger that generates supercharging pressure to an engine, an air source facility of a general manufacturing plant, and the like.
[0002]
[Prior art]
A turbocharger for supercharging an engine has, for example, a turbine compressor having an impeller and a centrifugal compressor (compressor) having an impeller integrated with each other via a bearing casing, and the impeller and the impeller are combined. The shaft is rotatably supported in the bearing vehicle compartment, the impeller is rotated by exhaust of the engine, and the impeller is rotated through the shaft by the rotation of the impeller, whereby the intake air is fed by the centrifugal compressor. The engine is compressed and supplied to the engine.
[0003]
In the centrifugal compressor used for the supercharger, a phenomenon called surging occurs, which may seriously affect the performance of the supercharger. Surging is a phenomenon in which a kind of self-excited vibration occurs even when there is no periodic load fluctuation, and the pressure and the discharge amount fluctuate periodically. Surging occurs when there is a small discharge amount in which the total lift (or pressure ratio) -discharge amount characteristic rises to the right as shown in FIG. The cause of surging will be explained qualitatively. When the discharge amount decreases and the flow rate flowing through the impeller decreases, a laminar boundary layer develops on the wall surface (casing) of the shroud wall facing the outer periphery of the impeller. Since there is little inflow of energy into the boundary layer, that portion becomes a low pressure region. As a result, a reverse flow from the high pressure region on the discharge side of the impeller occurs, and the discharge pressure decreases. When the discharge pressure decreases, the reverse flow stops and becomes a normal flow again. Thus, periodic fluctuations in the discharge pressure and the discharge amount occur, and this is surging. If surging occurs, the bearing, the impeller, the shaft coupling and the like are seriously damaged.
[0004]
FIG. 4B is a diagram of a plurality of characteristic curves using the rotation speed of the impeller as a parameter. A line connecting the vertices of the characteristic curve of FIG. 4A is referred to as a surge line S. This is called a surging area A. If the surge line S can be moved to the low flow rate side to the position S ′, the engine operation can be adapted over a wider range.
[0005]
In order to solve such a problem, the applicant of the present application previously filed a patent application (Japanese Patent Laid-Open No. 5-60097). FIG. 5 is a cross-sectional view of the centrifugal compressor disclosed in the above application. As shown in the drawing, a scroll-like compression flow path 3 is provided on the outer peripheral portion of the impeller 1 via the diffuser portion 2 and the suction port 4 is formed extending forward from the diffuser portion 2. A housing 6 having a shroud wall 5 is provided. Further, the impeller 1 is connected to a turbine impeller (not shown) via a shaft, and the turbine impeller is rotated by exhaust of the engine so that the impeller 1 rotates via the shaft. In the centrifugal compressor in which the vehicle 1 is rotated and the intake wheel is compressed by the rotation of the impeller 1 so that the engine is supplied with air, the blades are disposed on the inlet 4 side portion of the shroud wall 5. A throttle portion 7 that is reduced in diameter toward the entrance of the vehicle 1 is provided so that the air that has been contracted by the throttle portion 7 is sucked by the impeller 1, and the shroud wall 5 has an annular shape. of A retreat cavity 8 is provided, and further, a slit-shaped first flow path 9 for communicating the inside of the treatment cavity 8 and the installation position of the impeller 1 with the shroud wall 5, the inside of the treatment cavity 8, and the throttle portion Slit-like second flow passages 10 for communicating in a radial direction with a position slightly downstream from the end of 7 are respectively drilled in the circumferential direction, and the first flow passage 9, the treatment cavity 8, the second flow The passage 10 constitutes a circulation flow path for circulating a part of the air sucked by the impeller 1 at the time of low flow operation to reduce the flow rate of the surge wire.
[0006]
When the operation is performed, the air sucked from the suction port 4 by the rotation of the impeller 1 is sucked into the suction region in the impeller 1 and supplied to the target place through the diffuser portion 2 and the compression flow path 3. The During low flow operation, the pressure in all regions of the impeller 1 is higher than the pressure in the treatment cavity 8. Accordingly, an air flow is generated such that a part of the air passing through the blade portion of the impeller 1 is directed from the first flow path 9 into the treatment cavity 8. On the other hand, at this time, since the air entering from the suction port 4 is contracted by the throttle portion 7, the velocity distribution when passing through the second flow path 10 is outside (close to the wall) due to the contraction effect. It is bigger (faster). Therefore, the air flow that has received the contraction flow passes through the opening of the second flow path 10, and as a result, the air in the treatment cavity 8 is sucked from the second flow path 10, and as a result, the treatment cavity 8. A part of the air passing through the blade portion of the impeller 1 is exhausted from the first flow passage 9 through the treatment cavity 8 from the second flow passage 10, and it is again impeller 1. As shown by the broken line arrows in FIG. 5, a circulating flow a utilizing static pressure can be generated.
[0007]
Since the circulation flow a is generated in this way, the flow rate flowing in the impeller 1 can be increased even in the operation region where the discharge flow rate is small, and the back flow from the discharge side of the impeller 1 is extracted. The surge line S shown in FIG. 4 (B) can be moved to the position of S ′ on the low flow rate side.
[0008]
However, since the circulation flow a is a flow having a component in the same direction as the rotation of the impeller 1, that is, a forward swirl direction, it is possible to achieve a wider operating range than the case where there is no circulation flow a. Since the turning of the flow angle before and after the impeller 1 is small, the Euler head which is the pressure ratio of the entrance and exit of the impeller 1 is lowered.
[0009]
Therefore, the applicant of the present application has previously filed a patent application in order to widen the operating range without lowering the Euler head (Japanese Patent Laid-Open No. 2001-289197).
[0010]
6A and 6B are drawings disclosed in the above application. In the figure, parts common to those in FIG. 5 are denoted by the same reference numerals, and redundant description is omitted. In FIG. 6A, 11 is a reverse swirl fin provided in the second flow path 10, and in FIG. 6B, 12 is a reverse swirl fin provided in the treatment cavity 8. The reverse swirl fins 11, 12 have an angle α of 0 or positive with the radial direction, and as indicated by the dotted arrows, the reverse swirl fins 11, 12 are discharged as a flow in the range of the reverse turning direction from those having no turning component. The turning of the flow angle before and after 1 increases, and the Euler head, which is the pressure ratio between the entrance and exit of the impeller 1, increases.
[0011]
[Problems to be solved by the invention]
However, in the invention disclosed in JP-A-5-60097, the shape of the circulation channel formed by the first channel 9, the treatment cavity 8, and the second channel 10 is not specified at all. As a result of earnest research and experiments, the inventors of the present application have found that the shape of the circulation channel has a great influence on the surging region of the centrifugal compressor, and by specifying the shape of the circulation channel, centrifugal compression is achieved. We obtained knowledge that the operating range of the machine can be further expanded to the low flow rate side.
[0012]
The present invention has been completed based on the above findings, and an object of the present invention is to provide a centrifugal compressor capable of expanding an operation region by numerically specifying the shape of a circulation channel.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a centrifugal compressor according to the present invention includes a housing having a shroud wall extending forward from an outer peripheral portion of an impeller to form a suction port, and a portion of the shroud wall on the suction port side includes the housing. A throttle portion that is reduced in diameter toward the inlet of the impeller, and has a slit-shaped first flow path that opens at a portion of the shroud wall facing the outer periphery of the impeller, and a final end of the throttle portion. In the centrifugal compressor provided with a circulation flow path comprising a slit-shaped second flow path that opens near the small diameter, and an annular treatment cavity that connects the first flow path and the second flow path, The inner diameter of the annular treatment cavity is 1.5 to 2.0 times the inlet diameter of the impeller, and the height of the treatment cavity is 1.0 to 2.0 times the slit width of the first flow path.
[0014]
In addition, the circulating flow exiting the circulation channel is in a direction opposite to the radial flow or the rotational direction of the impeller on the second channel or the second channel and the second channel side of the cylindrical cavity. It is preferable to provide a plurality of reverse swirl fins that are inclined to provide a swirling flow.
[0015]
Next, the operation of the present invention will be described. As described above, the circulating flow that has flowed into the first flow path is a swirl flow that has a component in the same direction as the impeller, that is, a forward swirl direction. The first flow path is a slit-shaped flow path, and the flow path area increases as the distance from the inlet increases. Like the diffuser portion that connects the impeller outlet and the scroll-shaped compression flow path, the first flow path has a circulating flow. Convert velocity energy into pressure energy. Therefore, when the inner diameter of the treatment cavity is increased to be 1.5 to 2.0 times the impeller inlet diameter, the length of the first flow path is increased, and the function as a diffuser is sufficiently exhibited. The pressure at the treatment cavity inlet increases, and a sufficient amount of circulation flow is obtained in the low flow rate region, so that the surge line can be moved to the low flow rate side. Furthermore, since the height (width) of the treatment cavity is set to 1.0 to 2.0 times the slit width of the first flow path, the rapid expansion of the flow path of the circulating flow flowing into the treatment cavity from the first flow path. Pressure loss can be kept low.
[0016]
Further, by providing a reverse swirl fin on the outlet side of the circulation flow path, the air flow flowing into the impeller is made to flow in a radial direction or a direction swirling in the direction opposite to the rotation direction of the impeller. Since the turning of the flow angle before and after the vehicle is large and the impeller performs sufficient work, the Euler head as the pressure ratio of the entrance and exit of the impeller becomes large.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the invention described in claim 1 of the present application. In this figure, the same reference numerals are given to portions common to those in FIG. 5, and duplicate descriptions are omitted. In the figure, reference numeral 20 denotes a circulation flow path, which includes a first flow path 9, a treatment cavity 8, and a second flow path 10. Reference numeral 21 denotes an annular block, which forms a circulation channel 20 between the inner surface 5 a of the shroud wall 5. The block 21 is supported from the inner surface 5a of the shroud wall 5 by about three radial ribs (not shown). Reference numeral 9 denotes a slit-shaped first flow path, which is shown as a plane perpendicular to the rotation axis in the figure, but may be a frustoconical surface inclined with respect to the rotation axis. Since the diameter of the first flow path is enlarged, the velocity energy is converted into pressure energy inside as in the case of the dephaser 2, and the pressure is increased, but a sufficient length is necessary to exert its function. is there. The treatment cavity 8 is an annular cavity connected to the first flow path 9. As it can be taken long enough to the first flow path 9, to the inlet diameter _{D 1} of the the _{D 2} impeller 1 (the outer diameter of the annular block 21) the inner diameter of the treatment cavity _8, D 2 = 1.5 to be in ~2.0D _1. Further, the height h ₂ of the treatment cavity 8 is set so that h ₂ = 1.0 to 2.0 h ₁ with respect to the width h ₁ of the first flow path in order to prevent pressure loss due to sudden expansion of the flow path. ing. Reference numeral 10 denotes a second flow path connected to the treatment cavity 8. The outlet of the second flow path 10 opens slightly downstream of the throttle portion 7 of the suction port 4. The second flow path 10 is illustrated as a truncated conical surface whose diameter decreases toward the inlet of the impeller 1, but it may be a surface perpendicular to the rotation axis, or may be inclined in the direction opposite to the drawing. A conical surface may be used.
[0018]
2 is a cross-sectional view taken along a plane including a rotation axis, and FIG. 2B is a cross-sectional view taken along the arrow B in FIG. The present invention is obtained by adding a reverse swirl fin to the invention described in claim 1 shown in FIG. 1, and the same reference numerals are given to the parts common to FIG. In the figure, 13 is a reverse swirl fin. The angle α formed between the reverse swirl fin 13 and the radial surface 14 including the rotational axis may be in the range of 0 to a positive value. Although the reverse swirl fin 13 is provided from the portion near the second flow path 10 of the treatment cavity 8 to the second flow path 10 in the drawing, it may be provided only in the second flow path 10.
[0019]
Next, the operation of this embodiment will be described. As described above, the circulating flow a flowing into the first flow path 9 is a swirling flow having a component in the same direction as the impeller 1, that is, a forward swirling direction. The first flow path 9 is a slit-shaped flow path, and the flow path area increases as the distance from the inlet increases. Like the diffuser portion 2 that connects the impeller 1 outlet and the scroll-shaped compression flow path 3, The velocity energy of the circulating flow is converted into pressure energy. Accordingly, the inner diameter _{D 2} of the treatment cavity 8, increasing to be 1.5 to 2.0 times the impeller 1 inlet diameter _{D 1,} the length of the first passage 9 is increased, diffuser - as The The pressure at the inlet of the treatment cavity 8 increases sufficiently, a sufficient amount of circulation flow a is obtained in the low flow rate region, and the surge line S can be moved to the low flow rate side. Further, since the height (width) h ₂ of the treatment cavity 8 is set to 1.0 to 2.0 times the slit width h ₁ of the first flow path 9, the circulation flowing from the first flow path 9 into the treatment cavity 8. The pressure loss due to the sudden expansion of the flow path a can be kept low.
[0020]
Furthermore, by providing the reverse swirl fin 13 on the outlet side of the circulation flow path 20, the air flow a flowing into the impeller 1 becomes a flow flowing in the radial direction or in the direction opposite to the rotation direction of the impeller 1. Therefore, the turning of the flow angle before and after the impeller 1 is large, and the impeller 1 performs sufficient work, so the Euler head as the pressure ratio of the entrance and exit of the impeller 1 becomes large.
[0021]
FIG. 3 is a graph of the characteristic curve of the centrifugal compressor of the present invention. In the figure, Qd represents a design flow rate, Q / Qd represents a flow rate ratio, and S represents a surge line. In the figure, “when conventional treatment is mounted” is a centrifugal compressor having the structure shown in FIG. 5, and “when wearing the shape of the present invention” is a centrifugal compressor having the structure shown in FIG. “When the shape + reverse swirl fin is mounted” is a centrifugal compressor having a structure shown in FIG. The “pressure ratio” is the ratio of the outlet pressure / inlet pressure of the centrifugal compressor. FIG. 3 shows that the effect of the present invention is great.
[0022]
The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention.
[0023]
【The invention's effect】
As described above, since the centrifugal compressor of the present invention has a sufficiently large length of the first flow path, it flows into the treatment cavity in a state where the circulating flow is sufficiently decelerated in the first flow path. The pressure in the treatment cavity increases and the circulation flow rate increases. Furthermore, the Euler head rises by combining with the reverse swirl fin. As a result, the centrifugal compressor of the present invention has excellent effects such as the ability to expand the operating range to the low flow rate side.
[Brief description of the drawings]
FIG. 1 is a sectional view of a centrifugal compressor according to claim 1 of the present application.
FIG. 2 is a sectional view of a centrifugal compressor according to claim 2 of the present application.
FIG. 3 is a graph comparing the performance of the present invention and a conventional centrifugal compressor.
FIG. 4 is a graph of a characteristic curve of a centrifugal compressor.
FIG. 5 is a cross-sectional view of a conventional centrifugal compressor.
FIG. 6 is a cross-sectional view of a conventional centrifugal compressor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Impeller 4 Suction port 5 Shroud wall 6 Housing 7 Restriction part 8 Treatment cavity 9 1st flow path 10 2nd flow path 13 Reverse swirl fin 20 Circulation flow path

Claims (2)

A housing having a shroud wall that extends forward from the outer peripheral portion of the impeller to form a suction port, and a throttle portion that reduces the diameter toward the inlet direction of the impeller is provided in a portion on the suction port side of the shroud wall And a slit-shaped first flow path that opens in a portion of the shroud wall facing the outer periphery of the impeller, a slit-shaped second flow path that opens near the minimum diameter that is the end of the throttle portion, and In the centrifugal compressor provided with a circulation flow path composed of an annular treatment cavity connecting the first flow path and the second flow path, the inner diameter of the annular treatment cavity is 1. A centrifugal compressor characterized in that it is 5 to 2.0 times and the height of the treatment cavity is 1.0 to 2.0 times the slit width of the first flow path. The circulating flow exiting the circulating flow channel swirls in a direction opposite to the radial flow or the rotational direction of the impeller on the second flow channel or the second flow channel and the second flow channel side of the cylindrical cavity. The centrifugal compressor according to claim 1, further comprising a plurality of reverse swirl fins inclined so as to become a flow.

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