A centrifugal compressor for producing two different pressure ratios

Abstract

This invention relates to a centrifugal compressor for generating two different pressure ratios, belonging to the field of internal combustion engine turbocharging technology. It solves the problems of existing centrifugal compressors requiring impeller blade modification into a stepped shape and direct separation of gas flow channels to generate two different pressure ratios. The centrifugal compressor provided by this invention includes a first casing, a second casing, an impeller, a main shaft, a first turbocharging unit, and a second turbocharging unit. The first and second turbocharging units can respectively output high-pressure ratio gas and low-pressure ratio gas. Based on the original compressor structure, this invention achieves both high and low-pressure gas output without altering the impeller blade profile. It features a simple structure, saves space, and is highly efficient and stable. Furthermore, it avoids boundary layer separation of low-energy gas at the blade tip, which can cause impeller channel blockage and surge, thereby increasing the compressor's stable operating range.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine turbocharging technology, and more particularly to a centrifugal compressor for generating two different pressure ratios. Background Technology

[0002] Because some vehicles used in special applications require a two-stage turbocharging system for their internal combustion engines, micro gas turbines, as auxiliary power units, have the advantage of being applied to two-stage turbocharging systems. In operation, the micro gas turbine auxiliary turbocharging system must supply gas to both the main turbocharger and the micro combustion chamber. Since current centrifugal compressors, whether single-stage or multi-stage, can only output gas at one pressure ratio, the auxiliary turbine needs to drive two compressors to supply gas to both, increasing the length of the rotor system in the auxiliary turbocharging system and consequently increasing rotor imbalance. This also places extremely high demands on the rotor system's bending resistance and rigidity. Furthermore, because the auxiliary combustion compressor requires a higher pressure ratio, while the auxiliary turbocharger compressor in the two-stage turbocharger requires a lower pressure ratio, it is necessary to design a centrifugal compressor that combines the functions of both an auxiliary combustion compressor and an auxiliary turbocharger compressor, capable of outputting two different pressure ratios. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a centrifugal compressor for generating two different pressure ratios, in order to solve the problem that existing centrifugal compressors for generating two different pressure ratios require modifying the impeller blades into a stepped shape and directly separating the gas flow channels.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] A centrifugal compressor for generating two different pressure ratios includes a first casing, an impeller, a main shaft, a first booster unit, and a second booster unit; the first casing includes a compressor gas inlet and a first volute; the impeller includes a disk and blades; the main airflow channel is located between the inner wall of the first casing and the surface of the impeller.

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

[0007] Furthermore, the first pressurization unit includes a first airflow inlet, a first diffuser, and a first airflow collecting channel.

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

[0009] Furthermore, the first gas collecting channel is a vortex-shaped gas channel located inside the first volute.

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

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

[0012] Furthermore, the second pressurization unit includes a second airflow inlet, a second diffuser, a second airflow collector, and a second volute.

[0013] Furthermore, the second airflow inlet is connected to the downstream section of the main airflow channel.

[0014] Furthermore, the second booster unit is located inside the first housing.

[0015] Furthermore, the second airflow inlet is located on the rim wall of the first housing, and the second diffuser and the second airflow collector are located inside the first housing.

[0016] Furthermore, the second airflow inlet is an annular inlet concentric with the impeller and connected to the edge of the main airflow channel; the second collecting airflow channel is located inside the second volute; and the second diffuser is an annular channel with both ends connected to the second airflow inlet and the second collecting airflow channel, respectively.

[0017] Furthermore, the leaf tip curve 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 airflow channel are in the same direction.

[0019] Furthermore, it also includes a second housing; the second airflow inlet is located on the outer periphery of the disc, and the second diffuser and the second airflow collector are located inside the second housing.

[0020] Furthermore, the blade base separates from the rotor at the outer periphery of the second airflow inlet.

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

[0022] Furthermore, the inner ring plane of the second housing is in contact with the bottom plane of the wheel, and 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 airflow inlet is located on the disc, and the second diffuser and the second airflow collector are located inside the second housing.

[0024] Furthermore, the second airflow inlet consists of multiple openings spaced circumferentially on the disc.

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

[0026] (1) By setting a second pressurization unit, the present invention can achieve the effect of simultaneously assisting the combustion compressor and the booster compressor by using a centrifugal compressor to output two high-pressure gases with different pressure ratios.

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

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

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

[0030] (5) When the second booster unit of the present invention draws gas from the main airflow channel, it can draw away the low-energy gas in the blade tip gap, thereby avoiding the low-energy gas from causing boundary layer separation at the blade tip and blocking the impeller channel, thus increasing the stable operating range of the compressor.

[0031] (6) Without changing the original pressurization unit, the present invention sets a second airflow inlet on the housing or wheel and sets the second diffuser and the second collector airflow channel inside the housing. The structure is compact and reasonable, saving the space occupied by the equipment.

[0032] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the specification or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained from the content specifically pointed out in the text and accompanying drawings. Attached Figure Description

[0033] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

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

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

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

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

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

[0039] Figure label:

[0040] 1-First casing; 101-Compressor gas inlet; 102-First volute; 103-Wheel rim wall; 2-Second casing; 3-Impeller; 301-Disc; 302-Blade; 3021-Blade tip; 4-Main shaft; 5-First booster unit; 501-First airflow inlet; 502-First diffuser; 503-First gas collecting channel; 6-Second booster unit; 601-Second airflow inlet; 602-Second diffuser; 603-Second gas collecting channel; 604-Second volute; 7-Main airflow channel; 8-Blade tip clearance. Detailed Implementation

[0041] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which 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 intended 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, including a first housing 1, a second housing 2, an impeller 3, a main shaft 4, a first booster unit 5, and a second booster unit 6. The main shaft 4 mounts the impeller 3 onto the inner wall of the second housing 2 through a central shaft hole on the second housing 2 and the impeller 3. The first housing 1 is fitted over the impeller 3 and is bolted to the second housing 2. The front end center of the first housing 1 is provided with a compressor gas inlet 101, and the outer periphery of the gas inlet 101 is provided with a first volute 102 with a spiral gas collecting structure. The impeller 3 includes a disk 301 and blades 302. A blade tip gap 8 is left between the blade tip 3021 and the rim wall 103 of the first housing 1. A main airflow channel 7 is formed between the inner wall of the first housing 1 and the surface of the impeller 3. The first booster unit 5 is located on the outer periphery of the end of the main airflow channel 7. The first booster unit 5 includes a first airflow inlet 501, a first diffuser 502, and a first collecting airflow channel 503. The first airflow inlet 501 is located between the inner walls of the first housing 1 and the second housing 2, and is an annular inlet connected to the outlet of the impeller 3. The first diffuser 502 is an annular channel located on the outer periphery of the first airflow inlet 501. The first collecting airflow channel 503 is located on the outer periphery of the first diffuser 502 and is a collecting airflow channel formed by the inner wall of the first volute 102. The outlet of the first booster unit 5 can output high pressure ratio gas. The second pressurization unit 6 is a gas passage connected to the main airflow passage 7, including a second airflow inlet 601, a second diffuser 602, a second gas collecting channel 603, and a second volute 604. The second airflow inlet 601 is an annular inlet concentric with the impeller 3 and connected to the edge of the downstream section of the main airflow passage 7. Preferably, it is connected at 3 / 4 of the flow path of the main airflow passage 7. The second diffuser 602 is an annular channel connected to the second airflow inlet 601 and is located on the outer periphery of the second airflow inlet 601. The second gas collecting channel 603 is connected to the other end of the second diffuser 602 and is a gas collecting channel formed on the inner wall of the second volute 604. The second volute 604 is a vortex-shaped gas collecting structure and can be located inside the first housing 1 or the second housing 2. The end of the second gas collecting channel 603 is connected to the outlet of the second pressurization unit 6, outputting low-pressure gas.

[0044] In operation, gas enters the main airflow channel 7 from the compressor gas inlet 101. After being powered by the impeller 3, its velocity and pressure increase. Since the main airflow channel 7 is connected to the second airflow inlet 601, the gas flowing through the second airflow inlet 601 in the main airflow channel 7 can be drawn into the channel of the second booster unit 6. The drawn-in gas is diffused by the second diffuser 602, collected by the second collector channel 603, and then flows out of the compressor, outputting low-pressure gas. The gas that is not drawn in continues to be compressed by the impeller blades 302 in the impeller 3. After the pressure increases, due to the centrifugal force, it enters the first diffuser 502 from the first airflow inlet 501 for further diffusion, and is then collected by the first collector channel 503 in the first volute 102 before flowing out of the compressor, outputting high-pressure gas.

[0045] Compared with the prior art, since the second pressurization unit 6 of this application is a branch channel connected to the edge of the main airflow channel 7, low-pressure ratio gas is output by drawing low-energy gas near the second airflow inlet 601 in the main airflow channel 7 into the second pressurization unit 6. This solution differs from the prior art in that the main airflow channel 7 is directly divided into two channels to form the second channel. Therefore, the gas energy loss in the main airflow channel 7 is smaller, and the impact on the pressurization effect of the first pressurization unit 5 is smaller, which can meet the output requirements of more flexible high and low pressure ratios.

[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 airflow 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 airflow channel 7 is an arc-shaped surface near the second airflow inlet 601, and the second diffuser 602 is set as a gas channel formed between two parallel annular arc surfaces, and the arc surface is in the same direction as the arc surface of the main airflow channel 7, when the low-energy gas near the second airflow inlet 601 is drawn into the second diffuser 602, the arc-shaped channel of the second diffuser 602 can not only play a role in diffusion, but also play a role in smoothing the gas, so that the resistance encountered by the gas when gradually changing the flow direction is small, thereby reducing energy loss.

[0048] It should be noted that in existing centrifugal compressors, when the inlet flow rate is low, low-energy gas accumulates at the blade tip 3021 and undergoes boundary layer separation, leading to blockage of the impeller 3 passage and causing compressor surge. The second booster unit 6 of the dual-pressure-ratio centrifugal compressor of this invention is connected to the main airflow passage 7 in its downstream section, allowing low-energy gas near the second airflow inlet 601 to be drawn out of the blade tip gap 8, passing through the second diffuser 602 and the second collector airflow passage 603 before exiting the compressor. This effectively prevents boundary layer separation caused by low-energy gas accumulation in the blade tip gap 8, avoids blockage of the main airflow passage 7 that could cause compressor surge, and effectively improves the range of stable operating flow rates of the compressor.

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

[0050] 1. Determine the diameter D1 of the impeller and the first airflow inlet 501 based on the required high-pressure gas pressure ratio and the total output flow rate of the compressor (the sum of the high-pressure gas and low-pressure gas flow rates).

[0051] 2. Further determine the width b1 of the blade outlet and the first airflow inlet 501 based on the high-pressure gas flow rate.

[0052] 3. Based on the above calculations, determine the low-pressure impeller diameter D2 and width b2 required to achieve the low-pressure ratio according to the required low-pressure gas pressure ratio and the total output flow of the compressor. Considering the energy loss of the second diffuser 602 and the second gas collecting channel 603, in order to meet the low-pressure gas pressure ratio of the dual-pressure ratio output compressor, the diameter of the second gas inlet 601 needs to be larger than the theoretically calculated low-pressure impeller diameter D2, so that the pressure at the second gas inlet 601 is higher than the low-pressure output pressure, thus compensating for the flow loss in the second diffuser 602 and the second gas collecting channel 603.

[0053] 4. The width b3 of the second airflow inlet 601 can be calculated based on the principle of flow similarity: the ratio of the width of the second airflow inlet 601 to the low-pressure bleed airflow is equal to the ratio of the calculated low-pressure compressor impeller outlet width D2 to the total compressor output flow rate. Therefore, the width b3 of the second airflow inlet 601 can be determined based on the low-pressure bleed airflow rate. 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 airflow inlet 601, and converts the kinetic energy of the gas in the second pressurization unit 6 into the static pressure of the induced gas, thereby playing a diffusion role.

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

[0056] During implementation, the gas flowing through the second airflow inlet 601 in the main airflow channel 7 is drawn into the channel of the second pressurization unit 6. After being guided and diffused by the second diffuser 602, the gas is collected by the second collecting channel 603 and output as gas with a lower pressure ratio.

[0057] Compared with the prior art, this embodiment places the second pressurizing unit 6 inside the first housing 1, which can output gases with different pressure ratios to meet more flexible high and low pressure ratio output requirements. Furthermore, it eliminates the need for complex and precise machining to modify the blades 302 into stepped blades to generate two pressure ratios. Therefore, the blade tip and outlet of the blades 302 can remain unchanged, and there is no need to add a baffle to directly separate the main airflow channel. This makes implementation convenient, structurally simple, and functionally flexible. In addition, since the second pressurizing unit 6 can be placed in the unused space between the first volute 504 and the compressor gas inlet 101, it does not require occupying a large amount of additional usable space, resulting in a compact structure that does not affect the original internal layout of the compressor.

[0058] Since the second airflow inlet 601 is located on the rim wall 103 of the first casing 1, when the compressor airflow is small, it can more directly draw the low-energy gas in the blade tip gap 8 into the second booster unit 6, avoiding the low-energy gas from separating at the blade tip and blocking the impeller passage, thus preventing surge. This can better play the role of widening the compressor flow range.

[0059] Example 2

[0060] like Figure 2 , Figure 3 As shown, the difference from Embodiment 1 is that the second pressurization unit 6 is disposed inside the second housing 2, the second airflow inlet 601 is opened on the second housing 2, and the second diffuser 602 and the second airflow collector are located inside the second housing 2. The blade bottom is separated from the wheel at the outer periphery of the second airflow inlet; the inner wall of the second housing is provided with an annular opening, which 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, 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 airflow inlet 601 in the main airflow channel 7 is drawn into the channel of the second pressurization unit 6. After being guided and diffused by the second diffuser 602, the gas is collected by the second collecting channel 603 and output as gas with a lower pressure ratio.

[0062] Compared with the prior art, this embodiment achieves the same beneficial effects as embodiment 1. At the same time, by distributing the second booster unit 6 and the first booster unit 5 on both sides of the impeller 301, the volume of the second volute 604 is not limited by space, thereby meeting the needs of more application scenarios.

[0063] Because the gas near the second booster unit 6 is drawn out of the main airflow channel 7, the gas pressure in the main airflow channel 7 near the second airflow inlet 601 decreases. This disrupts the original pressure balance where the gas pressure in the blade tip clearance 8 is lower and the gas pressure on the impeller side 301 is higher, causing the gas near the blade tip 3021 to flow intermittently towards the impeller side 301. Therefore, at low compressor flow rates, the flow of gas from the blade tip clearance 8 towards the impeller side 301 prevents the accumulation of low-energy gas in the blade tip clearance 8, inhibits boundary layer separation after low-energy gas accumulates at the blade tip 3021, and avoids impeller channel blockage that could cause compressor surge. This effectively widens the stable operating flow range of the compressor.

[0064] Example 3

[0065] like Figure 4 , Figure 5 As shown, the difference from Embodiment 2 is that in this embodiment, the second airflow inlet 601 of the second booster unit 6 is opened on the wheel 301, and the second diffuser 602 and the second airflow channel 603 are located inside the second housing 2; the second airflow inlet 601 is a plurality of openings spaced along the circumference on the wheel 301, 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 openings is preferably 6.

[0066] Specifically, this embodiment adopts a method of partially induced airflow by opening arc-shaped openings at intervals on the impeller 301. This not only achieves the same beneficial effect as in embodiment 2, but also ensures that the impeller 301 remains a whole after the second airflow inlet 601 is opened, so that the blade 302 does not have to be separated from the impeller 301 at the impeller outlet, thus ensuring the stability of the shape of the blade 302. Figure 5 The example only shows the uniform area interval air intake method of the 301 wheel; other methods, such as non-uniform area interval air intake, are also within the scope of this design.

[0067] Compared with the prior art, the centrifugal compressor provided by the present invention for generating two different pressure ratios does not require damage to the impeller blade profile on the basis of the original compressor structure. It can not only achieve flexible high and low pressure gas output, but also avoid low-energy gas blocking the impeller passage at the blade tip 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 includes a first housing (1), a second housing (2), an impeller (3), a main shaft (4), a first booster unit (5), and a second booster unit (6); The first housing (1) includes a compressor gas inlet (101) and a first volute (102); the impeller (3) includes a disk (301) and blades (302); the inner wall of the first housing (1) and the surface of the impeller (3) are connected to a main airflow channel (7), and there is a blade tip gap (8) between the inner wall of the first housing (1) and the blade tip of the blade (302). The second pressurization unit (6) includes a second airflow inlet (601), a second diffuser (602), a second airflow collecting channel (603), and a second volute (604). The tip curve of the blade (302) is a smooth curve. The second airflow inlet (601) is connected to the edge of the downstream section of the main airflow channel (7), so that the gas flowing through the second airflow inlet (601) in the main airflow channel (7) is drawn into the second pressurization unit (6). After being diffused by the second diffuser (602), the drawn gas is collected by the second gas collecting channel (603) and output as low-pressure gas. The second diffuser (602) is configured as a gas channel formed between two parallel annular arc surfaces; The second airflow inlet (601) is located on the rim wall (103) of the first housing (1), and the second diffuser (602) and the second airflow collection channel (603) are located inside the first housing (1).

2. The centrifugal compressor according to claim 1, wherein The first booster unit (5) outputs high pressure ratio gas.

3. The centrifugal compressor according to claim 2, wherein The first booster unit (5) includes a first airflow inlet (501), a first diffuser (502), and a first airflow collection channel (503).

4. The centrifugal compressor according to claim 3, wherein The first airflow inlet (501) is an annular inlet connected to the outlet of the impeller (3).

5. The centrifugal compressor according to claim 3, wherein The first gas collecting channel (503) is a vortex-shaped gas channel located inside 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, The two ends of the first diffuser (502) are connected to the first airflow inlet (501) and the first airflow collecting channel (503), respectively.

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