Centrifugal compressor for generating two different pressure ratios

Abstract

The invention relates to a centrifugal compressor for generating two different pressure ratios, belongs to the technical field of internal combustion engine pressurization, and solves the problems that an impeller blade needs to be transformed into a step shape and a gas flow channel needs to be directly separated in an existing centrifugal compressor for generating two different pressure ratios. The centrifugal compressor comprises a first machine shell, a second machine shell, an impeller, a main shaft, a first pressurizing unit and a second pressurizing unit. The first pressurizing unit and the second pressurizing unit can output high-pressure-ratio gas and low-pressure-ratio gas correspondingly. On the basis of the original structure of the gas compressor, the impeller blade type does not need to be damaged, high-pressure and low-pressure gas output can be achieved, the structure is simple, space is saved, and efficiency and stability are achieved; and surge caused by blockage of an impeller channel due to boundary layer separation of low-energy gas at the blade top can be avoided, so that the stable working range of the gas compressor is enlarged.

Description

Technical Field

[0001] The invention relates to the technical field of internal combustion engine supercharging, and in particular to a centrifugal compressor for generating two different pressure ratios. Background Art

[0002] Since some vehicles used in special occasions need to be equipped with a two-stage supercharging system for the internal combustion engine, the micro gas turbine as an auxiliary power device has the advantage of being applied to the two-stage supercharging system. When in use, the micro gas turbine auxiliary supercharging system needs to supply air to both the main supercharger and the micro combustion chamber. Since the current centrifugal compressor, whether single-stage or multi-stage, can only output gas with one pressure ratio, the auxiliary turbine needs to drive two compressors to supply air to both, which increases the length of the rotor system in the auxiliary supercharging system, thereby increasing the imbalance of the rotor, and also puts forward extremely high requirements on the bending resistance and stiffness of the rotor system. At the same time, since the pressure required by the auxiliary combustion compressor is relatively high, and the pressure required by the auxiliary supercharging compressor in the two-stage supercharger is relatively low, it is necessary to design a centrifugal compressor that can output two different pressure ratios while taking into account the functions of the auxiliary combustion compressor and the auxiliary supercharging compressor. Summary of the invention

[0003] In view of the above analysis, an embodiment of the present invention aims to provide a centrifugal compressor for generating two different pressure ratios, so as to solve the problem that the existing centrifugal compressor generating two different pressure ratios needs to transform the impeller blades into a stepped shape and directly separate the gas flow path.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] A centrifugal compressor for generating two different pressure ratios comprises a first casing, an impeller, a main shaft, a first boosting unit and a second boosting unit; the first casing comprises a compressor gas inlet and a first volute; the impeller comprises a wheel disc and blades; and a main air flow channel is formed between the inner wall of the first casing and the surface of the impeller.

[0006] Furthermore, the first boosting unit outputs high-pressure ratio gas; and the second boosting unit outputs low-pressure ratio gas.

[0007] Furthermore, the first supercharging unit includes a first air flow inlet, a first diffuser and a first collecting flow passage.

[0008] Furthermore, the first air flow inlet is an annular inlet connected to the outlet of the impeller.

[0009] Furthermore, the first collecting flow passage is a vortex-shaped gas passage arranged in the first volute.

[0010] Furthermore, the first diffuser is an annular gas channel formed between two parallel annular planes.

[0011] Furthermore, two ends of the first diffuser are respectively connected to the first air flow inlet and the first collecting flow channel.

[0012] Furthermore, the second supercharging unit includes a second air flow inlet, a second diffuser, a second collecting flow passage and a second volute.

[0013] Furthermore, the second air flow inlet is communicated with the downstream flow section of the main air flow channel.

[0014] Furthermore, the second boost unit is located in the first casing.

[0015] Furthermore, the second air flow inlet is opened on the rim wall of the first casing, and the second diffuser and the second collecting flow passage are located in the first casing.

[0016] Furthermore, the second air flow inlet is a circular inlet concentric with the impeller and connected to the flow channel edge of the main air flow channel; the second collecting flow channel is arranged in the second volute; the second diffuser is an annular channel whose two ends are respectively connected to the second air flow inlet and the second collecting flow channel.

[0017] Furthermore, the blade tip curve of the blade is a smooth curve.

[0018] Furthermore, the second diffuser is a gas channel formed between two parallel annular arc surfaces, and the arc surface of the second diffuser and the arc surface of the main air flow channel are arc surfaces in the same direction.

[0019] Furthermore, it also includes a second casing; the second air flow inlet is located at the outer periphery of the wheel disc, and the second diffuser and the second collecting flow channel are located in the second casing.

[0020] Furthermore, the blade bottom is separated from the wheel disc at the outer periphery of the second air flow inlet.

[0021] Furthermore, the inner wall of the second housing is provided with a circular ring opening, and the circular ring opening divides the inner wall of the second housing into an inner ring plane and an outer ring plane.

[0022] Furthermore, the inner ring plane of the second housing fits the bottom plane of the wheel disc, the outer ring plane of the second housing is provided with an annular step, the bottom plane of the annular step is adjacent to the bottom of the blade and has a gap, and the side wall of the annular step is adjacent to the outlet of the blade and has a gap.

[0023] Furthermore, the second air flow inlet is opened on the wheel disc, and the second diffuser and the second collecting flow passage are located in the second casing.

[0024] Furthermore, the second air flow inlet is a plurality of openings opened at intervals along the circumference of the wheel disc.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] (1) The present invention provides a second boosting unit, so that one centrifugal compressor can output two high-pressure gases with different pressure ratios, thereby achieving the boosting effect of both the auxiliary combustion compressor and the auxiliary boosting compressor.

[0027] (2) Based on the original structure of the compressor, the present invention does not need to transform the impeller blades into a stepped shape to achieve the output of gases with different pressure ratios. It only needs to modify the compressor casing structure, or modify the impeller at the same time, to achieve the simultaneous output of high-pressure and low-pressure gases. The structure is simple and easy to process, and does not affect the original internal layout of the compressor.

[0028] (3) The present invention does not separate the main air flow channel and does not affect the pressurization effect of the high-pressure ratio gas outlet.

[0029] (4) The low-pressure ratio gas boosting unit of the present invention adopts a curved surface design, which can effectively reduce the energy loss of the gas.

[0030] (5) When the second boost unit of the present invention draws gas from the main air flow channel, it can draw low-energy gas from the blade tip gap, thereby preventing the low-energy gas from separating in the boundary layer at the blade tip and blocking the impeller channel to cause surge, thereby increasing the stable operating range of the compressor.

[0031] (6) The present invention does not change the original supercharging unit. By arranging the second air flow inlet on the casing or the wheel and arranging the second diffuser air and the second collecting air duct in the casing, the structure is compact and reasonable, and the space occupied by the equipment is saved.

[0032] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the following content, and some advantages can be obvious from the description or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the text and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0034] Figure 1 is a schematic diagram of an axial cross-sectional structure of a centrifugal compressor of specific embodiment 1;

[0035] Figure 2 is a schematic diagram of an axial cross-sectional structure of a centrifugal compressor of specific embodiment 2;

[0036] Figure 3 is a partially enlarged schematic diagram of the second air inlet of specific embodiment 2;

[0037] Figure 4 is a schematic diagram of an axial cross-sectional structure of a centrifugal compressor of specific embodiment 3;

[0038] Figure 5 It is a schematic diagram of the radial cross-sectional structure of the wheel disc of specific embodiment 3;

[0039] Reference numerals:

[0040] 1-first casing; 101-compressor gas inlet; 102-first volute; 103-wheel rim wall; 2-second casing; 3-impeller; 301-wheel disc; 302-blade; 3021-blade tip; 4-main shaft; 5-first boost unit; 501-first air flow inlet; 502-first diffuser; 503-first collecting flow channel; 6-second boost unit; 601-second air flow inlet; 602-second diffuser; 603-second collecting flow channel; 604-second volute; 7-main air flow channel; 8-blade tip clearance. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0042] Example 1

[0043] like Figure 1As shown, a centrifugal compressor for generating two different pressure ratios is disclosed, comprising a first casing 1, a second casing 2, an impeller 3, a main shaft 4, a first supercharging unit 5 and a second supercharging unit 6. The main shaft 4 installs the impeller 3 on the inner wall of the second casing 2 through the central axis hole on the second casing 2 and the impeller 3. The first casing 1 is sleeved on the outside of the impeller 3 and is fixed to the second casing 2 by bolts. A compressor gas inlet 101 is provided at the center of the front end of the first casing 1, and a first volute 102 of a spiral gas collecting structure is provided on the periphery of the gas inlet 101; the impeller 3 comprises a wheel disc 301 and blades 302, and a blade tip gap 8 is left between the blade tip 3021 and the wheel rim wall 103 of the first casing 1, and a main air flow channel 7 is formed between the inner wall of the first casing 1 and the surface of the impeller 3. The first boosting unit 5 is located at the periphery of the end of the main air flow channel 7. The first boosting unit 5 includes a first air flow inlet 501, a first diffuser 502 and a first collecting channel 503. The first air flow inlet 501 is located between the inner walls of the first casing 1 and the second casing 2, and is an annular inlet connected to the outlet of the impeller 3. The first diffuser 502 is located in an annular channel on the periphery of the first air flow inlet 501. The first collecting channel 503 is located on the periphery of the first diffuser 502, and is an air collecting channel formed on the inner wall of the first volute 102. The first boosting unit 5 can output high pressure ratio gas at its outlet. The second boost unit 6 is a gas channel connected to the main gas channel 7, including a second gas inlet 601, a second diffuser 602, a second collecting channel 603 and a second volute 604; the second gas inlet 601 is a circular inlet concentric with the impeller 3, and is connected to the edge of the downstream flow section of the main gas channel 7. The preferred solution is to connect at 3 / 4 of the flow of the main gas channel 7; the second diffuser 602 is an annular channel connected to the second gas inlet 601, located at the periphery of the second gas inlet 601; the second collecting channel 603 is connected to the other end of the second diffuser 602, and is a gas collecting channel formed by the inner wall of the second volute 604. The second volute 604 is a vortex-shaped gas collecting structure, which can be arranged in the first housing 1 or the second housing 2. The end of the second collecting channel 603 is connected to the outlet of the second boost unit 5, and outputs low-pressure ratio gas.

[0044] During implementation, the gas enters the main airflow channel 7 from the compressor gas inlet 101, and the speed and pressure increase after the impeller 3 does work. Since the main airflow channel 7 is connected with the second airflow inlet 601, the gas flowing through the second airflow inlet 601 in the main airflow channel 7 can be sucked into the channel of the second booster unit 6. The sucked gas is diffused by the second diffuser 602, collected by the second collecting flow channel 603, and then flows out of the compressor, outputting low-pressure ratio gas. The unsucked gas continues to be compressed by the impeller blades 302 in the impeller 3. After the pressure increases, it enters the first diffuser 502 from the first airflow inlet 501 for diffusion due to the action of centrifugal force, and then is collected by the first collecting flow channel 503 in the first volute 102 and flows out of the compressor, outputting high-pressure ratio gas.

[0045] Compared with the prior art, since the second boosting unit 6 of the present application is a branch channel connected to the edge of the main airflow channel 7, the low-pressure ratio gas is output by sucking the low-energy gas near the second airflow inlet 601 in the main airflow channel 7 into the second boosting unit 6. This solution is different from the solution in the prior art that directly divides the main airflow channel 7 into two channels to form a second channel, so the gas energy loss in the main airflow channel 7 is small, and the boosting effect of the first boosting unit 5 is less affected, which can meet the more flexible high and low pressure ratio output requirements.

[0046] Furthermore, the second diffuser 602 is a gas channel formed between two parallel annular arc surfaces, and the arc surface of the second diffuser 602 and the arc surface of the main air flow channel 7 are arc surfaces in the same direction.

[0047] Compared with the diffuser formed between two annular planes in the prior art, since the main air flow channel 7 is an arc-shaped surface near the second air flow inlet 601, the second diffuser 602 is set as a gas channel formed between two parallel circular arc surfaces, and the arc surface is in the same direction as the main air flow channel 7. Therefore, when the low-energy gas near the second air flow inlet 601 is sucked into the second diffuser 602, the arc-shaped ring channel of the second diffuser 602 can not only play a role in diffusing the gas, but also play a role in smoothly guiding the gas, so that the gas is subject to less resistance when gradually changing the flow direction, thereby reducing energy loss.

[0048] It should be noted that, when the intake flow rate of the centrifugal compressor of the prior art is small, the low-energy gas will gather at the blade tip 3021 and then separate at the boundary layer, resulting in blockage of the impeller 3 channel, causing the compressor to surge. The second boost unit 6 of the output dual-pressure ratio centrifugal compressor of the present invention is connected to the main airflow channel 7 at its downstream flow section, so that the low-energy gas near the second airflow inlet 601 is sucked out of the blade tip gap 8, and flows out of the compressor after passing through the second diffuser 602 and the second collecting flow channel 603, effectively avoiding the boundary layer separation of the low-energy gas after gathering at the blade tip 8, avoiding the blockage of the main airflow channel 7 causing the compressor to surge, and effectively improving the range of the stable working flow of the compressor.

[0049] The design principle of the second booster unit 6 is:

[0050] 1. Determine the diameter D1 of the impeller and the first air flow inlet 501 according to the required high-pressure gas pressure ratio and the total output flow of the compressor (the sum of the high-pressure gas and low-pressure gas flow values);

[0051] 2. Further determine the width b1 of the blade outlet and the first air flow inlet 501 according to the high-pressure gas flow rate;

[0052] 3. Referring to the above calculation, the low-pressure impeller diameter D2 and width b2 required to achieve the low pressure ratio are determined according to the required low-pressure gas pressure ratio and the total compressor output flow rate. Taking into account the energy loss of the second diffuser 602 and the second collecting flow channel 603, in order to meet the low-pressure gas pressure ratio of the dual-pressure ratio output compressor, the diameter of the second air flow inlet 601 needs to be larger than the theoretically calculated low-pressure impeller diameter D2, so that the pressure at the second air flow inlet 601 is higher than the low-pressure output pressure, thereby compensating for the flow loss in the second diffuser 602 and the second collecting flow channel 603.

[0053] 4. The width b3 of the second air inlet 601 can be calculated according to the flow similarity principle: the ratio of the width of the second air inlet 601 to the low-pressure bleed air flow is equal to the ratio of the calculated low-pressure compressor impeller outlet width D2 to the compressor output total flow, so the width b3 of the second air inlet 601 is determined according to the low-pressure bleed air flow. m1 is the high pressure gas flow rate, and m2 is the low pressure gas flow rate.

[0054] 5. The second diffuser 602 has the same width as the second air flow inlet 601, and converts the kinetic energy of the gas in the second booster unit 6 into the static pressure of the bleed air, thereby playing a pressure diffusion role.

[0055] like Figure 1 As shown, the second supercharging unit 6 is disposed in the first housing 1 , the second air inlet 601 is opened on the rim wall 103 of the first housing 1 , and the second diffuser 602 and the second air collecting channel 603 are located in the first housing 1 .

[0056] During implementation, the gas flowing through the second air flow inlet 601 in the main air flow channel 7 is sucked into the channel of the second booster unit 6, and after being guided and diffused by the second diffuser 602, it is collected by the second collecting channel 603 and outputs gas with a lower pressure ratio.

[0057] Compared with the prior art, the second boosting unit 6 is arranged in the first housing 1 in this embodiment, which can output gas with different pressure ratios to meet the more flexible output requirements of high and low pressure ratios, and does not need to transform the blade 302 into a stepped blade through complex and fine processing to produce two pressure ratios. Therefore, the blade top and outlet of the blade 302 can remain in their original state, and there is no need to add a partition to directly separate the main air flow channel. It is easy to implement, simple in structure, and flexible in function. In addition, since the second boosting unit 6 can be arranged in the idle space between the first volute 504 and the compressor gas inlet 101, it does not need to occupy a large useful space, the structure is compact, and does not affect the original internal layout of the compressor.

[0058] Since the second air flow inlet 601 is opened on the rim wall 103 of the first casing 1, when the compressor airflow is small, the low-energy gas in the blade tip gap 8 can be more directly sucked into the second boost unit 6, avoiding the boundary layer separation of the low-energy gas at the blade tip that blocks the impeller channel and causes surge, thereby better widening the compressor flow range.

[0059] Example 2

[0060] like Figure 2 , Figure 3 As shown, the difference from Example 1 is that the second supercharging unit 6 is arranged in the second housing 2, the second airflow inlet 601 is opened on the second housing 2, and the second diffuser 602 and the second collecting flow channel are located in the second housing 2. The bottom of the blade is separated from the wheel disc at the outer part of the second airflow inlet; the inner wall of the second housing is provided with a circular opening, and the circular opening divides the inner wall of the second housing into an inner ring plane and an outer ring plane; the inner ring plane is in contact with the bottom plane of the wheel disc, and the outer ring plane is provided with an annular step, the bottom plane of the step is adjacent to the bottom of the blade and has a gap, and the side wall of the step is adjacent to the outlet of the blade and has a gap.

[0061] During implementation, the gas flowing through the second air flow inlet 601 in the main air flow channel 7 is sucked into the channel of the second booster unit 6, and after being guided and diffused by the second diffuser 602, it is collected by the second collecting channel 603 and outputs gas with a lower pressure ratio.

[0062] Compared with the prior art, this embodiment has the same beneficial effects as Embodiment 1, and at the same time, the second boost unit 6 and the first boost unit 5 are arranged on both sides of the blade disk 301, so that the volume of the second volute 604 is not limited by space, thereby meeting the needs of more application scenarios.

[0063] Since the gas near the second booster unit 6 is sucked out of the main airflow channel 7, the gas pressure in the main airflow channel 7 near the second airflow inlet 601 is reduced, which destroys the pressure balance of the original low gas pressure in the blade tip gap 8 and the high gas pressure on the side of the impeller 301, and makes the gas near the blade tip 3021 flow intermittently toward the side of the impeller 301. Therefore, when the compressor has a small flow rate, since the gas in the blade tip gap 8 flows toward the side of the impeller 301, the gathering of low-energy gas in the blade tip gap 8 is avoided, and the boundary layer separation of low-energy gas after gathering at the blade tip 3021 is suppressed, and the clogging of the impeller channel causing the compressor to surge is avoided, which has the technical effect of effectively widening the stable working flow range of the compressor.

[0064] Example 3

[0065] like Figure 4 , Figure 5 As shown, the difference from Example 2 is that, in this embodiment, the second air flow inlet 601 of the second boost unit 6 is opened on the wheel disc 301, and the second diffuser 602 and the second collecting air duct 603 are located in the second casing 2; the second air flow inlet 601 is a plurality of openings opened on the wheel disc 301 at intervals along the circumference, and the shape of the openings is arc-shaped, circular or rectangular; the shape of the openings is preferably arc-shaped, and the number of the openings is preferably 6.

[0066] Specifically, this embodiment adopts a method of local air intake by opening arc-shaped openings at intervals on the wheel disc 301, which not only has the same beneficial effects as Example 2, but also enables the wheel disc 301 to remain as a whole after the second air flow inlet 601 is opened, so that the blades 302 do not need to be separated from the wheel disc 301 at the impeller outlet, thereby ensuring the stability of the shape of the blades 302. Figure 5 Only the uniform area interval intake method of the wheel 301 is shown, and other methods such as non-uniform area interval intake are also within the design scope of this case.

[0067] Compared with the prior art, the centrifugal compressor for generating two different pressure ratios provided by the present invention does not need to destroy the impeller blade shape on the basis of the original structure of the compressor, and can achieve flexible high and low pressure gas output, and can also avoid low energy gas blocking the impeller channel at the blade top and causing surge, thereby increasing the range of stable operation of the compressor.

Claims

1. A centrifugal compressor for producing two different pressure ratios, characterized in that: It comprises a first casing (1), an impeller (3), a main shaft (4), a first supercharging unit (5) and a second supercharging unit (6); The first casing (1) comprises a compressor gas inlet (101) and a first volute (102); the impeller (3) comprises a wheel disc (301) and blades (302); a main air flow channel (7) is provided between the inner wall of the first casing (1) and the surface of the impeller (3), and a blade tip clearance (8) is provided between the inner wall of the first casing (1) and the blade tip of the blade (302).

2. The centrifugal compressor for generating two different pressure ratios according to claim 1, characterized in that: The first pressurizing unit (5) outputs high-pressure ratio gas; and the second pressurizing unit (6) outputs low-pressure ratio gas.

3. The centrifugal compressor for generating two different pressure ratios according to claim 2, characterized in that: The first supercharging unit (5) comprises a first air flow inlet (501), a first diffuser (502) and a first air collecting channel (503).

4. The centrifugal compressor for generating two different pressure ratios according to claim 3, characterized in that: The first air flow inlet (501) is an annular inlet connected to the outlet of the impeller (3).

5. The centrifugal compressor for generating two different pressure ratios according to claim 3, characterized in that: The first collecting flow channel (503) is a vortex-shaped gas channel arranged in the first volute (102).

6. The centrifugal compressor for generating two different pressure ratios according to claim 3, characterized in that: The first diffuser (502) is an annular gas channel formed between two parallel annular planes.

7. The centrifugal compressor for generating two different pressure ratios according to claim 6, characterized in that: Two ends of the first diffuser (502) are respectively connected to the first air flow inlet (501) and the first collecting flow channel (503).

8. The centrifugal compressor for generating two different pressure ratios according to claim 2, characterized in that: The second supercharging unit (6) comprises a second air flow inlet (601), a second diffuser (602), a second air collecting passage (603) and a second volute (604).

9. The centrifugal compressor for generating two different pressure ratios according to claim 8, characterized in that: The second boosting unit (6) is located inside the first casing (1).

10. The centrifugal compressor for generating two different pressure ratios according to claim 8, characterized in that: The second air flow inlet (601) is communicated with the downstream flow section of the main air flow channel (7).

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