Two-degree-of-freedom stator diffuser structure for semi- centrifugal compressor outlet

Abstract

This invention belongs to the field of fluid machinery technology. It discloses a two-stage, two-degree-of-freedom stator diffuser-rectifier structure at the outlet of a semi-centrifugal compressor, positioned between the compressor outlet and the combustion chamber inlet. The structure includes a first-stage stator and a second-stage stator arranged sequentially along the airflow direction. By sequentially arranging the first-stage and second-stage stators between the compressor outlet and the combustion chamber inlet along the airflow direction, the rectification and diffusion process, originally concentrated in a single-stage flow channel, is distributed to be completed continuously by two stages of stators. This helps reduce the single-stage diffusion load, mitigates the separation risk caused by unfavorable pressure gradients, and improves the stability of the conversion from dynamic pressure to static pressure. By using a split-type first-stage stator with a higher number of blades, it can preferentially recover circumferential divergent kinetic energy and swirling kinetic energy, rapidly weakening large-scale non-uniform swirling flow near the compressor outlet, quickly normalizing the airflow direction, and establishing more favorable inflow conditions for the second-stage stator.

Description

Technical Field

[0001] This invention belongs to the field of fluid machinery technology, and particularly relates to a two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of a semi-centrifugal compressor. Background Technology

[0002] Currently, small compressors mainly employ centrifugal or axial flow structures, but they still suffer from shortcomings in total pressure recovery and energy utilization in the section from compressor outlet to combustion chamber inlet. Centrifugal compressors typically exhibit strong swirling flow at the outlet, making it difficult to effectively convert swirling kinetic energy into static pressure. This easily leads to flow separation, vortex dissipation, and additional total pressure loss in the subsequent transition channel, resulting in a low total pressure recovery coefficient. While axial flow compressors possess high flow capacity, their single-stage pressure ratio is relatively limited under small-scale conditions. Especially for semi-centrifugal compressors, their axial outlet may still retain significant swirling components and multi-directional velocity components, lacking efficient rectification and diffusion mechanisms, resulting in insufficient energy recovery in the section from compressor outlet to combustion chamber inlet.

[0003] In existing technologies, downstream flow shaping typically relies on a single-stage stator or conventional diffuser channel to simultaneously achieve flow direction correction and velocity attenuation within a finite axial length. Due to the large single-stage diffuser load, a strong unfavorable pressure gradient is easily formed within the blade passage, leading to boundary layer thickening, local separation, and an increase in additional total pressure loss. Summary of the Invention

[0004] The purpose of this invention is to provide a two-stage, two-degree-of-freedom stator diffuser rectification structure at the outlet of a semi-centrifugal compressor, which solves the technical problems in the prior art such as insufficient swirl elimination, inadequate diffusion, low total pressure recovery, and low energy recovery efficiency.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A two-stage, two-degree-of-freedom stator diffuser-rectifier structure is located between the compressor outlet and the combustion chamber inlet at the outlet of a semi-centrifugal compressor. It includes a primary stator and a secondary stator arranged sequentially along the airflow direction. The primary stator is a split structure and is fixed to the inner side of the compressor's outer wall. The secondary stator is an integral structure and is fixed to a central structural support. The secondary stator maintains a clearance fit with the main shaft. The primary and secondary stators each include multiple first stator blades and multiple second stator blades, with the number of first stator blades exceeding the number of second stator blades. The primary stator, secondary stator, compressor outer wall, combustion chamber outer wall, combustion chamber inner wall, and central structural support together define an axially connected annular flow channel from the compressor outlet to the combustion chamber inlet, allowing the airflow from the compressor outlet to undergo rectification and diffusion in stages along the primary and secondary stators.

[0006] Preferably, the first-stage stator is located between the compressor and the second-stage stator, and the second-stage stator is located between the first-stage stator and the combustion chamber inlet.

[0007] Preferably, the first-stage stator is composed of multiple first stator blades, which are evenly distributed circumferentially on the inner side of the compressor outer wall.

[0008] Preferably, the first-stage stator includes thirty-six first stator blades, which are fixed to the compressor structure housing by laser welding.

[0009] Preferably, the primary stator is made of 6061 aluminum alloy.

[0010] Preferably, multiple second stator blades form an integral blade cascade, which is fixed to the central structural support.

[0011] Preferably, the secondary stator comprises eighteen secondary stator blades, and the secondary stator is bolted to the central structural support.

[0012] Preferably, the secondary stator is made of 310S stainless steel.

[0013] Preferably, the gas flow path is as follows: compressor outlet, first stage stator inlet, first stage stator outlet, second stage stator inlet, second stage stator outlet, and combustion chamber inlet.

[0014] Preferably, the first stator blade extends from the inner side of the compressor outer wall toward the main shaft, and the second stator blade extends from the central structural support toward the direction away from the main shaft.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In this invention, by sequentially setting a first-stage stator and a second-stage stator along the airflow direction between the compressor outlet and the combustion chamber inlet, the rectification and diffusion process, which was originally concentrated in a single-stage flow channel, is distributed to be completed continuously by two-stage stators. This helps to reduce the single-stage diffusion load, mitigate the separation risk caused by unfavorable pressure gradients, and improve the stability of the conversion from dynamic pressure to static pressure.

[0016] 2. The two-stage dual-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor in this invention, by setting a split-type first-stage stator with a higher number of blades, can preferentially recover circumferential divergent kinetic energy and swirling kinetic energy, can rapidly weaken large-scale non-uniform swirling flow near the compressor outlet, make the airflow direction more regular as soon as possible, and establish more favorable inflow conditions for the second-stage stator.

[0017] 3. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor in this invention, by setting a two-stage stator, can further rectify and diffuse the residual swirling flow and axial velocity at the outlet of the first-stage stator, which is beneficial to improve the outlet static pressure, improve the uniformity of the outlet flow field, and improve the boundary conditions at the combustion chamber inlet. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a cross-sectional view of the two-stage stator diffuser rectifier structure in this invention; Figure 2 This is the gas flow path of the two-stage stator diffuser rectifier structure in this invention; Figure 3 This is a three-dimensional view of the first-order stator in this invention; Figure 4 This is a left view of the first-order stator in this invention; Figure 5 This is a three-dimensional view of the secondary stator in this invention; Figure 6 This is a left view of the secondary stator in this invention; Reference numerals: 1. Compressor outer wall; 2. Compressor impeller; 3. First-stage stator; 4. Second-stage stator; 5. Central structural support. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] This invention is described in detail with reference to the accompanying drawings. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not to scale. Furthermore, the accompanying drawings are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0024] Furthermore, it should be noted in the description of this invention that the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] A semi-centrifugal compressor is a compressor type in which the compressor impeller performs the main work in the upstream stage, and the outlet flow transitions from a high-speed rotating state to a near-axial transport state. This type of compressor is characterized by a high pressure ratio per unit stage and a compact structure. However, its outlet is often accompanied by strong swirling flow, uneven velocity direction, and difficulty in fully converting local kinetic energy into static pressure. Therefore, it is prone to separation and additional losses in the subsequent short-distance transition channel.

[0027] The two-stage two-degree-of-freedom stator diffuser rectification structure provided by this invention aims to solve the flow shaping and diffusion problems in the downstream section of a semi-centrifugal compressor.

[0028] The term "two degrees of freedom" as used in this paper refers to two stages of stators controlling two main flow states respectively. The first-stage stator handles the circumferential divergent and swirling degrees of freedom, while the second-stage stator handles the axial swirling degree of freedom and the axial velocity component. The term "usable dynamic pressure" as used in this paper refers to the dynamic pressure portion that can be converted into static pressure through rectification and diffusion under given flow channel conditions.

[0029] To facilitate understanding, the key terms will be explained before describing the embodiments. Circumferential divergent degrees of freedom refer to the tendency of gas to diffuse, deviate, and spread unevenly in the circumferential direction around the central axis of the machine. Its essence is the discretization and non-uniformity of the outlet flow in the circumferential direction. Swirling degree of freedom refers to the fact that gas still has a significant circumferential velocity around the central axis, thus forming an overall rotational tendency.

[0030] Axial swirling degree of freedom refers to a state in which, although the gas has a main direction of forward transport, its velocity vector still has a spiral-like forward characteristic, which is a composite state formed by the coupling of residual swirling and axial transport.

[0031] The axial velocity component refers to the velocity component of the gas moving along the main axis. This velocity component is not a negative factor, but when its value is too large and it is not properly diffused, it means that a considerable portion of the available dynamic pressure has not yet been converted into static pressure.

[0032] Dynamic pressure is the pressure term resulting from fluid velocity, which can be expressed as half the fluid density multiplied by the square of the velocity. Static pressure is the thermodynamic pressure exerted by the fluid on the wall. Total pressure is the sum of static and dynamic pressures. The total pressure recovery coefficient characterizes the ratio of the total pressure retained at the combustion chamber inlet after the airflow passes through the stator structure to the total pressure at the compressor outlet; a higher value indicates a smaller total pressure loss during the rectification and diffusion process.

[0033] Staged diffusion refers to the process of not completing all deceleration and pressurization at once in a single flow channel, but rather breaking down the diffusion task into multiple series components to complete it step by step. This reduces the load on a single-stage diffuser and lowers the risk of separation induced by unfavorable pressure gradients.

[0034] Example: Figures 1 to 6 As shown, the two-stage dual-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor is located between the compressor outlet and the combustion chamber inlet, and includes a first-stage stator 3 and a second-stage stator 4 arranged sequentially along the airflow direction.

[0035] The compressor impeller 2 is located upstream of the unit and is used to accelerate and enhance the air entering the compressor. The compressor outer wall 1 forms the outer boundary of the upstream flow channel. At the same time, the compressor outer wall 1 also undertakes the positioning and bearing function of the first-stage stator 3, which is directly welded to the compressor outer wall 1. The outer wall of the combustion chamber and the inner wall of the combustion chamber together define the annular confluence channel after the outlet of the second-stage stator 4. Structurally, they envelop and guide the airflow at the combustion chamber inlet.

[0036] The first-stage stator 3 is located in the near-outlet region behind the compressor impeller outlet and is fixed inside the compressor casing. The first-stage stator 3 is the main diffuser unit, which is used to perform the first-stage rectification and diffusion of the airflow from the compressor outlet in order to recover the available dynamic pressure corresponding to the circumferential divergent degree of freedom and the swirling degree of freedom.

[0037] The secondary stator 4 is located downstream of the primary stator 3 and near the combustion chamber inlet area, and is fixed on the central structural support 5. The secondary stator 4 serves as an additional diffuser unit, used to perform a second stage of rectification and diffusion on the airflow after it has been treated by the primary stator 3, so as to further recover the dynamic pressure corresponding to the residual swirling flow and axial velocity, thereby increasing the static pressure of the airflow and improving the outlet flow field. The dynamic pressure can be evaluated by using the definition of local airflow dynamic pressure, combined with the static pressure recovery coefficient and the total pressure loss coefficient.

[0038] A main shaft is also set at the center of the device. The main shaft is mainly responsible for driving the air compressor 2 to rotate. The secondary stator 4 is fixed to the stationary structure through the central structural support 5 and maintains a clearance fit with the main shaft, thus forming an overall structure of rotation and stationary operation, and internal and external coordination.

[0039] like Figures 1 to 4 As shown, the first-stage stator 3 adopts a split structure, with thirty-six first-stage stator blades evenly distributed circumferentially on the inner side of the compressor outer wall 1, and fixed to the compressor structural shell by laser welding. The first-stage stator 3 is located near the compressor outlet, which is beneficial for rectifying and diffuserizing the high-speed incoming flow as early as possible, and improves the installation rigidity of the first-stage stator 3.

[0040] Furthermore, under operating conditions where the local temperature at the compressor outlet meets the material requirements, the first-stage stator 3 can be made of 6061 aluminum alloy to balance quality control and processing performance. Under higher temperature conditions, the first-stage stator 3 can also be made of heat-resistant aluminum alloy, stainless steel, or nickel-based alloy.

[0041] Specifically, the thirty-six first stator blades of the first stage stator 3 are evenly arranged circumferentially, which effectively disperses the local flow and local turning load borne by each blade passage. For the compressor outlet, there is a significant circumferential velocity and circumferentially uneven incoming flow. If only a single-stage stator with fewer blades is used, the inflow deviation borne by a single blade passage will increase, and local boundary layer thickening and separation will be more likely to occur in the blade passage.

[0042] The first-stage stator 3, with its thirty-six first-stage stator blades, finely segments the outlet flow stream using a high number of blades, enabling preferential shaping of the circumferential divergent and swirling degrees of freedom over a shorter axial distance. Preferential shaping refers to, without aiming to completely eliminate all velocity components at once, first directionally suppressing the circumferential diffusion and overall rotational tendencies that are most prone to losses, thus transforming the incoming flow from a highly skewed state to a relatively controllable one.

[0043] Moreover, setting the first-stage stator 3 as a split type has the following advantages: First, the split type facilitates the processing, positioning, and correction of each blade, which helps to ensure the circumferential pitch accuracy and inflow angle matching accuracy of each blade during the installation process; Second, the split structure enables the first-stage stator 3 to better adapt to the strong circumferential non-uniform flow field at the compressor outlet. The split structure facilitates the positioning and installation angle calibration of each blade before assembly, thereby improving the inflow adaptability.

[0044] like Figure 1 , Figure 2 , Figure 5 and Figure 6 As shown, the second-stage stator 4 is a supplementary diffuser component. The second-stage stator 4 adopts an integral structure, consisting of eighteen second-stage stator blades forming a single blade cascade, which is fixed to the central structural support 5 by bolts. Since the second-stage stator 4 is close to the combustion chamber inlet, its operating temperature is higher than that of the first-stage stator 3 region. Therefore, the second-stage stator 4 can be made of 310S stainless steel to improve structural stability and oxidation resistance under high-temperature conditions.

[0045] The secondary stator 4 is used to perform a second stage of rectification and diffusion on the residual swirling flow and high axial velocity at the outlet of the primary stator 3, thereby further reducing the flow velocity, increasing the static pressure and improving the uniformity of the outlet flow field.

[0046] Specifically, the secondary stator 4 does not simply repeat the function of the primary stator 3, but rather supplements the residual helical flow and axial high-speed flow based on the pre-rectification of the primary stator 3. Since the inlet flow of the secondary stator 4 has already been pre-treated by the primary stator 3, its diffusion process is beneficial to further increase the static pressure with a lower separation risk.

[0047] The second-stage stator 4 adopts an integrated structure, which helps to ensure the relative positional accuracy of each blade and the overall coaxiality. The second-stage stator 4 has fewer blades than the first-stage stator 3, which helps to reduce flow blockage and surface friction losses while meeting the supplementary diffusion requirements.

[0048] It should be noted that during the design process, the installation angles of the first-stage stator 3 and the second-stage stator 4 are determined based on the velocity triangle at the impeller outlet under the compressor's design operating conditions. The inlet angle of the first-stage stator 3 is matched with the average absolute flow direction angle at the impeller outlet to reduce the leading edge angle of attack of the first-stage stator 3; similarly, the inlet angle of the second-stage stator 4 is matched with the average absolute flow direction angle at the outlet of the first-stage stator 3 to reduce the leading edge angle of attack of the second-stage stator 4. The axial position, blade height, chord length, pitch, and throat area of ​​the first-stage stator 3 and the second-stage stator 4 are determined based on the design flow rate, design speed, and target combustion chamber inlet pressure recovery requirements.

[0049] Working principle: In actual use, air enters through the compressor inlet, and after the compressor impeller 2 does work, it flows out through the compressor outlet. At this time, the airflow has a high speed and a certain swirling component. The airflow first enters the first stage stator 3. The first stage stator 3 performs the first stage rectification and diffusion of the incoming flow to weaken the circumferential diffusion trend and the overall swirling flow, and converts part of the dynamic pressure into static pressure.

[0050] After being processed by the first-stage stator 3, the airflow enters the second-stage stator 4, where the second-stage stator 4 continues to rectify and diffuse the residual swirling flow and the higher axial velocity, further decelerating the airflow and increasing the static pressure level.

[0051] Finally, the airflow treated by the second-stage stator 4 enters the combustion chamber inlet channel, thereby improving the pressure and velocity distribution conditions at the combustion chamber inlet.

[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0053] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A two-stage, two-degree-of-freedom stator diffuser-rectifier structure at the outlet of a semi-centrifugal compressor, disposed between the compressor outlet and the combustion chamber inlet, characterized in that, It includes a first-stage stator (3) and a second-stage stator (4) arranged sequentially along the airflow direction; The first-stage stator (3) is a split structure and is fixed to the inner side of the compressor outer wall (1); The secondary stator (4) is an integral structure and is fixed on the central structure support (5). The secondary stator (4) maintains a clearance fit with the main shaft. The primary stator (3) and the secondary stator (4) each include a plurality of first stator blades and a plurality of second stator blades, and the number of first stator blades is greater than the number of second stator blades; The primary stator (3), secondary stator (4), compressor outer wall (1), combustion chamber outer wall, combustion chamber inner wall, and central structural support (5) together define an axially connected annular flow channel from the compressor outlet to the combustion chamber inlet, so that the airflow from the compressor outlet can be rectified and diffused in stages along the primary stator (3) and secondary stator (4).

2. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor according to claim 1, characterized in that, The first-stage stator (3) is located between the compressor (2) and the second-stage stator (4), and the second-stage stator (4) is located between the first-stage stator (3) and the combustion chamber inlet.

3. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor according to claim 2, characterized in that, The first-stage stator (3) is composed of multiple first stator blades, which are evenly distributed circumferentially on the inner side of the compressor outer wall (1).

4. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor according to claim 3, characterized in that, The first-stage stator (3) includes thirty-six first stator blades, which are fixed to the compressor structure shell by laser welding.

5. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor according to claim 4, characterized in that, The primary stator (3) is made of 6061 aluminum alloy.

6. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor according to claim 1, characterized in that, Multiple second stator blades form an integral blade cascade, which is fixed on the central structure support (5).

7. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of a semi-centrifugal compressor according to claim 6, characterized in that, The secondary stator (4) includes eighteen secondary stator blades, and the secondary stator (4) is mounted on the central structural support (5) by bolts.

8. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of the semi-centrifugal compressor according to claim 7, characterized in that, The secondary stator (4) is made of 310S stainless steel.

9. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of a semi-centrifugal compressor according to claim 1, characterized in that, The gas flow path is as follows: compressor outlet, first stage stator (3) inlet, first stage stator (3) outlet, second stage stator (4) inlet, second stage stator (4) outlet and combustion chamber inlet.

10. The two-stage two-degree-of-freedom stator diffuser rectification structure at the outlet of a semi-centrifugal compressor according to claim 1, characterized in that, The first stator blade extends from the inner side of the compressor outer wall (1) toward the direction close to the main shaft, and the second stator blade extends from the central structure support (5) toward the direction away from the main shaft.

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