Air intake structure, centrifugal compressor and turboprop engine

Abstract

The present invention relates to the field of aero-engine technology, and more specifically, to an air intake structure, a centrifugal compressor, and a turboprop engine, wherein the air intake structure includes an air intake casing, an outer cover, an impeller cover, an impeller, and an isolation flange. The air intake casing is connected to the outer cover, the outer cover is disposed outside the impeller and the impeller cover, and the impeller cover is disposed outside the impeller, forming an air flow channel between the impeller and the impeller cover. The isolation flange is mounted outside the impeller cover and connected to the outer cover. A mounting hole for mounting a compressor shaft is provided in the middle of the air intake casing. A plurality of air intake channels are provided within the air intake casing, and the ends of the air intake channels along the air flow direction are connected to the air flow channels. The air intake structure also includes a bleed reflux structure for adjusting the amount of gas reflux, and the bleed reflux structure is respectively connected to the air intake channel and the air flow channel. The present invention can adjust the amount of gas reflux to enable the compressor to always operate in a high-efficiency range while maintaining a certain air flow and pressure, thereby increasing engine power and reducing fuel consumption and pollutant emissions.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation engines, and more particularly to an air intake structure, a centrifugal compressor, and a turboprop engine. Background Art

[0002] In order to prevent aircraft engine compressor surge, many compressors are equipped with bleed valves. Generally, the bleed valves are opened below the 92% to 95% Ng speed range to discharge a portion of the compressed air directly into the atmosphere, thereby increasing the air flow through the compressor and keeping the compressor operating point away from the surge line. Bleeding the compressor will not only cause energy loss, but also make the combustion chamber temperature higher during the aircraft engine startup process, consuming more starting electricity and fuel. However, not bleeding will cause the blade surface airflow to separate, the compressor to surge, and the efficiency to drop sharply, causing fatigue cracks in the parts to expand, and in severe cases, failure to occur. Existing anti-surge bleed valves (see attached Figure 5 ), the air inlet is directly connected to the atmosphere, so that part of the compressed air is discharged directly into the atmosphere to meet the function of keeping the compressor working point away from the surge line, which inevitably causes energy loss and cannot achieve the optimization and maximization of energy utilization.

[0003] A Chinese patent discloses a multi-channel compressor bleed air circulation device for a turboshaft engine. Multiple gas return channels are provided on the compressor casing. By using a multi-channel extraction and recirculation structure, the surge margin and operating range of the turboshaft engine's centrifugal compressor under low and high pressure ratio conditions can be effectively widened, while reducing compressor bleed volume, improving engine power, and reducing fuel consumption and pollutant emissions. However, this structure roughly controls the air pressure entering the diffuser by recirculating gas at different locations, thereby keeping the compressor away from the surge point. Since the pressure cannot be precisely controlled, it cannot ensure that the compressor always operates in the high-efficiency zone. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide an air intake structure that can adjust the gas return flow rate so that the compressor always operates in a high-efficiency zone while maintaining a certain air flow and pressure, thereby increasing engine power and reducing fuel consumption and pollutant emissions.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] An air intake structure is provided, including an air intake casing, an outer cover, an impeller cover, an impeller, and an isolation flange. The air intake casing is connected to the outer cover, the outer cover is arranged outside the impeller and the impeller cover, and the impeller cover is arranged outside the impeller, an air flow channel is formed between the impeller and the impeller cover, and the cross-sectional area of the air flow channel changes from large to small along the air flow direction. The isolation flange is installed outside the impeller cover and connected to the outer cover; a mounting hole for installing a compressor shaft is provided in the middle of the air intake casing, and the mounting hole is coaxially arranged with the impeller, and a plurality of air intake channels are provided in the air intake casing, and the ends of the air intake channels along the air flow direction are connected to the air flow channels; and an air discharge reflux structure for adjusting the gas reflux amount is also included, and the air discharge reflux structure is respectively connected to the air intake channel and the air flow channel.

[0007] Specifically, air enters the intake channel, and under the action of the high-speed rotating impeller, the air is thrown from the center of the centrifugal impeller to the outer edge of the centrifugal impeller by centrifugal force, that is, it enters the air flow channel, and the pressure gradually increases; the intake structure of the present invention is the intake part located in front of the diffuser, and the air flowing out of the air flow channel will enter the diffuser. The present invention abandons the existing solution of directly discharging the exhaust gas to the atmosphere, and instead guides the exhaust gas back to the intake channel, so that part of the air circulates in the intake structure, so that the compressor can not only discharge the exhaust gas but also recycle the available energy of the exhaust gas, so that the temperature of the core combustion chamber of the compressor does not increase too much. The high-pressure exhaust gas flows back to the compressor intake channel to form a jet, which blows at high speed towards the inner flow channel wall of the intake channel and the back of the impeller blade. The airflow entrainment effect accelerates the airflow in the intake channel axially, thereby reducing the angle of attack of the airflow at the leading edge of the impeller blade, delaying the airflow separation at the back of the blade, improving the efficiency of the compressor, and slightly improving the pressure ratio. By adjusting the amount of recirculated air through the bleed air recirculation structure, the amount of air entering the diffuser can be adjusted, allowing the compressor to be adjusted to the optimal high-efficiency operating point. This improves compressor efficiency, reduces wasted energy, and lowers fuel consumption. It is undeniable that compressed air released by existing bleed air valves enters the atmosphere surrounding the engine, potentially flowing to the engine air intake and also "recirculating" to the centrifugal compressor. However, in this case, the air is recirculated, but the available energy is not recovered. The technical problem to be solved by the present invention is to achieve bleed air recirculation in the centrifugal compressor and efficiently recover the available energy in the bleed air, allowing the centrifugal compressor to withstand more airflow distortion from the intake duct and avoid surge. The bleed air recirculation structure also regulates the flow rate of the recirculated air so that the air flow received by the combustion chamber is less than that of the compressor, allowing the engine to operate normally, efficiently, and stably at partial load within a wider range below 95% Ng speed.

[0008] Preferably, the exhaust reflux structure includes a pressure regulating assembly, a high-pressure air chamber and a pressure regulating air chamber, and several reflux channels. The high-pressure air chamber is surrounded by an outer cover, an isolation flange, and an impeller cover. The pressure regulating air chamber is surrounded by an air intake casing, an impeller cover, and an isolation flange. The high-pressure air chamber and the pressure regulating air chamber are separated on both sides of the isolation flange. A through hole is provided on the isolation flange to connect the high-pressure air chamber and the pressure regulating air chamber. The pressure regulating assembly is installed at the through hole of the isolation flange. The high-pressure air chamber is connected to the air flow channel. One end of the reflux channel is connected to the pressure regulating air chamber, and the other end is connected to the air intake channel.

[0009] Preferably, the pressure regulating assembly includes a rotary valve, a drive motor, a controller, an air pressure sensor and a temperature sensor. The air pressure sensor and the temperature sensor are both installed in the pressure regulating chamber. The rotary valve is located at the through hole. The rotary valve is connected to the drive motor, and the drive motor is connected to the controller signal.

[0010] Preferably, the driving motor is a digital servo.

[0011] Preferably, the reflux channel is communicated with the mounting hole, and is arranged close to the mounting hole toward the impeller. The axis of the reflux channel and the axis of the mounting hole form an inclination angle α, and the inclination angle α is 30° to 40°.

[0012] Preferably, the corners in the reflux channel adopt circular transition turns.

[0013] Preferably, a nozzle is provided at the end of the air inlet channel and the mounting hole close to the impeller, and the nozzle is located beside the connection point between the return channel and the mounting hole.

[0014] Preferably, a notch is provided in the air flow channel near the end portion with a smaller cross-sectional area, and the notch is communicated with the high-pressure air chamber.

[0015] Preferably, the high-pressure air chamber, the pressure-regulating air chamber, the nozzle, and the gap are all annular structures.

[0016] Preferably, the number of the intake channels and the return channels are equal, both being 3 to 5, and are in one-to-one correspondence, and the intake channels are evenly distributed in the intake casing.

[0017] The present invention also provides a centrifugal compressor, comprising the above-described air intake structure, diffuser, air guide wheel, compressor shaft, and motor, wherein the air guide wheel is installed at the front end of the air intake structure, the diffuser is installed at the rear end of the impeller, the compressor shaft is installed in the mounting hole, and the motor is connected to the compressor shaft.

[0018] Specifically, air enters the air intake channel, and under the action of the high-speed rotating impeller, the air is thrown from the center of the centrifugal impeller to the outer edge of the centrifugal impeller by centrifugal force, that is, it enters the air flow channel, and the pressure gradually increases. The air flowing out of the air flow channel enters the diffuser, the speed decreases, the pressure increases again, and finally flows out of the compressor.

[0019] The present invention also provides a turboprop engine, comprising an engine body and the centrifugal compressor as described above, wherein the centrifugal compressor is installed in the engine body.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The centrifugal compressor of the present invention features a positive feedback loop for air pressure signals. Higher bleed pressure increases the gas velocity at the inlet duct before the diffuser, resulting in a stronger ejection boost effect and higher compressor outlet pressure. This centrifugal compressor has a slightly higher compression ratio and a wider high-efficiency operating range. By adjusting the angle of the rotary vane valve to vary the bleed return air flow rate, the compressor operating point is positioned within the high-efficiency range.

[0022] (2) The centrifugal compressor of the present invention has a high surge margin, which broadens the stable operating speed range of the turboprop engine and reduces fuel consumption. Since the turbine speed in some low-power operating conditions is reduced by (30-40)%, the noise level is significantly reduced.

[0023] (3) The position where the return channel of the centrifugal compressor of the present invention enters the air inlet channel is selected to be close to the inlet end of the centrifugal impeller, which is beneficial to increasing the energy of the boundary layer in the air inlet casing and on the back of the impeller blades, and delaying the separation of the air flow.

[0024] (4) The return channel uses smooth rounded corners to reduce flow losses. The annular nozzle can increase the jet velocity and enhance the injection and supercharging effect. The high-speed air jet can blow the impeller and has a high-pressure air starting function.

[0025] (5) The centrifugal compressor of the present invention has a bleed air return flow control function, thus having higher safety. In the event of damage to the digital servo, the rotary vane valve remains stationary and maintains a fixed opening, and the minimum bleed air return flow can still prevent compressor surge. In the prior art, if the conventional anti-surge bleed air valve fails, the aircraft engine cannot start smoothly, and surge, overheating, low power, flameout, scraping, and breakage may occur.

[0026] (6) Both the digital servo and the rotary plate valve have a health self-check function. The self-check function of the ordinary pneumatic anti-surge vent valve is very poor, and the indicator light often reports a false fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural schematic diagram of an air intake structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the installation of the impeller cover, pressure regulating assembly and isolation flange of the present invention;

[0029] Figure 3 for Figure 1 sectional view of

[0030] Figure 4 for Figure 3 A local enlarged view of point A;

[0031] Figure 5 It is a structural diagram of an anti-surge vent valve in the prior art;

[0032] Figure 6 This is the compressor characteristic curve of the centrifugal compressor.

[0033] The icon marks are explained as follows:

[0034] 1. Intake casing; 11. Nozzle; 2. Outer cover; 3. Impeller cover; 4. Impeller; 5. Isolation flange; 61. Intake channel; 62. Air flow channel; 71. Pressure regulating assembly; 711. Rotary vane valve; 712. Drive motor; 72. High-pressure air chamber; 73. Pressure regulating air chamber; 74. Return channel; 75. Notch; 8. Compressor shaft; 9. Anti-surge valve; α is the inclination angle formed by the axis of the return channel and the axis of the mounting hole.

[0035] Arrows indicate the direction of airflow. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only and are schematic, not actual, representations. They should not be construed as limiting this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted from the drawings.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0038] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0039] Example 1

[0040] like Figures 1 to 4 The figure shows an embodiment of an air intake structure of the present invention, including an air intake casing 1, an outer cover 2, an impeller cover 3, an impeller 4, and an isolation flange 5. The air intake casing 1 is connected to the outer cover 2, the outer cover 2 is arranged outside the impeller 4 and the impeller cover 3, and the impeller cover 3 is arranged outside the impeller 4. An air flow channel 62 is formed between the impeller 4 and the impeller cover 3. Along the air flow direction, the cross-sectional area of the air flow channel 62 changes from large to small. The isolation flange 5 is installed outside the impeller cover 3 and connected to the outer cover 2; a mounting hole for installing the compressor shaft 8 is provided in the middle of the air intake casing 1, and the mounting hole is coaxially arranged with the impeller 4. A plurality of air intake channels 61 are provided in the air intake casing 1, and the ends of the air intake channels 61 along the air flow direction are connected to the air flow channels 62; it also includes a venting reflux structure for adjusting the gas reflux amount, and the venting reflux structure is respectively connected to the air intake channel 61 and the air flow channel 62.

[0041] By setting the cross-sectional area of the airflow channel 62 from large to small, preferably, the cross-sectional area of the air intake channel 61 is also set from large to small along the airflow direction, and the cross-sectional area at the end of the air intake channel 61 is larger than the cross-sectional area at the front end of the airflow channel 62. During the air inflow process, as the flow channel area decreases, the flow velocity increases and the air pressure increases.

[0042] As an embodiment of the present invention, the exhaust reflux structure includes a pressure regulating assembly 71, a high-pressure air chamber 72, a pressure regulating air chamber 73, and a plurality of reflux channels 74. The high-pressure air chamber 72 is surrounded by an outer cover 2, an isolation flange 5, and an impeller cover 3. The pressure regulating air chamber 73 is surrounded by an intake casing 1, an impeller cover 3, and an isolation flange 5. The high-pressure air chamber 72 and the pressure regulating air chamber 73 are separated on both sides of the isolation flange 5. A through hole is opened on the isolation flange 5 to connect the high-pressure air chamber 72 with the pressure regulating air chamber 73. The pressure regulating assembly 71 is installed at the through hole of the isolation flange 5. The high-pressure air chamber 72 is connected to the air flow channel 62. One end of the reflux channel 74 is connected to the pressure regulating air chamber 73, and the other end is connected to the intake channel 61.

[0043] The pressure regulating assembly 71 is used to regulate the air pressure. Specifically, the air pressure is regulated by controlling the air flow from the high-pressure air chamber 72 into the pressure regulating air chamber 73. The high-pressure air chamber 72 is connected to the end of the air flow channel 62, that is, the position before the high-pressure gas enters the diffuser. The return channel 74 is arranged between the pressure regulating air chamber 73 and the intake channel 61. Specifically, by returning a part of the high-pressure gas that is about to enter the diffuser to the high-pressure air chamber 72, entering the pressure regulating air chamber 73 through the pressure regulating assembly 71, and then returning to the vicinity of the air inlet of the intake channel 61 through the return channel 74, the bleed air is recovered, which can not only reduce the air flow rate of the high-pressure gas entering the diffuser, but also avoid directly discharging the high-pressure gas into the atmosphere. It is reused by reflux, thereby realizing the bleed air reflux of the centrifugal compressor and the efficient recovery of available energy, so that the centrifugal compressor can resist more air inlet air distortion and no surge occurs.

[0044] The centrifugal compressor with bleed air return flow control function needs to solve the problem of high-pressure air bleed flow control. Figure 6 , the horizontal axis is the gas flow rate, the unit is kilograms per second; the vertical axis is the compression ratio, the contour line is the isoefficiency line, the rib line is the isospeed line, and the red line is the surge line. From the centrifugal compressor characteristic curve diagram (Map diagram), it can be seen that moving the working point adjacent to the surge line in the direction of increasing the flow rate and reducing the pressure ratio can make the working point move away from the surge line. At the surge boundary, the bleed valve can increase the flow rate and reduce the pressure ratio by opening, so that the working point enters the narrow and long high-efficiency area of the compressor Map diagram. Excessive bleed and pressure reduction will jump out of the high-efficiency area diagonally downward. Ordinary bleed valves only have two states: open and closed, and it is difficult to achieve fine control of the bleed flow rate. The present invention can accurately control the return air flow rate by adopting the pressure regulating component 71, so that the compressor always operates in the high-efficiency area.

[0045] As an embodiment of the present invention, the pressure regulating assembly 71 includes a rotary valve 711, a drive motor 712, a controller, an air pressure sensor and a temperature sensor. The air pressure sensor and the temperature sensor are both installed in the pressure regulating air chamber 73. The rotary valve 711 is located at the through hole. The rotary valve 711 is connected to the drive motor 712, and the drive motor 712 is connected to the controller signal.

[0046] The rotary vane valve 711 is positioned between the high-pressure air chamber 72 and the pressure-regulating air chamber 73, blocking the opening connecting the high-pressure air chamber 72 and the pressure-regulating air chamber 73. By controlling the position of the rotary vane valve 711, the size of the opening is controlled, thereby controlling the amount of reflux. A pressure sensor collects pressure information within the pressure-regulating air chamber 73 and feeds it back to the controller. A temperature sensor monitors the temperature within the pressure-regulating air chamber 73 and feeds the result back to the controller. The controller controls the drive motor 712 to rotate the rotary vane valve 711, thereby adjusting the angle of rotation of the rotary vane valve 711 and controlling the opening width of the connection port. Preferably, the drive motor 712 and the controller are integrated into a digital servo, perhaps a 90° digital servo, to gradually open and close the rotary vane valve 711. The rounded corners of the rotary vane valve 711 allow it to rotate 90° in a narrow space without interfering with the intake casing 1. The output shaft of the dedicated 90° digital servo is offset to avoid obstructing the connection port, and the output gear is mounted in a slightly elevated convex cavity. This digital servo is driven by a stepper motor and features stall detection, providing health diagnostics. By controlling air flow and velocity, the air pressure can be adjusted, achieving a pressure-regulating function.

[0047] As one embodiment of the present invention, the return channel 74 is connected to the mounting hole. The return channel 74 is arranged near the mounting hole toward the impeller 4. The axis of the return channel 74 and the axis of the mounting hole form an inclination angle α, which is 30° to 40°.

[0048] The pressure regulating air chamber 73 is located on the side of the air inlet channel 61, and the return channel 74 is used to make the return gas return to the entrance of the air inlet channel 61. Specifically, the connection position of the return channel 74 and the air inlet channel 61 is very critical. A bearing mounting position is provided at the end of the air inlet structure near the mounting hole for mounting a bearing to support the compressor shaft 8. The present invention communicates with the mounting hole of the compressor shaft 8 through the return channel 74, and the mounting hole is connected to the air inlet channel 61, thereby making the return gas return to the air inlet channel 61; the direction of the connection section between the return channel 74 and the mounting hole is also very important, which is related to the problem of the incident angle of the return gas. The return channel 74 is close to the mounting hole toward the impeller 4 The direction setting can be consistent with the direction of air flowing into the air inlet channel 61, and ultimately all of them flow to the diffuser. If the return channel 74 is set in the opposite direction, part of the gas will flow out from the bearing mounting position at the end of the mounting hole, causing the loss of return gas. It will also cause part of the gas to collide with the compressor shaft 8 wall and the mounting hole wall and then return, causing energy loss; the return channel 74 needs to avoid the bearing mounting position and the air inlet channel 61 to avoid interference; the axis of the return channel 74 and the axis of the mounting hole are at an inclination angle α. Preferably, the inclination angle α is 35 degrees, which allows the airflow to smoothly enter the swirl chamber formed by the mounting hole wall and the compressor shaft 8 wall, with sufficient flow area and small kinetic energy loss.

[0049] As an embodiment of the present invention, a nozzle 11 is provided at the end of the air inlet passage 61 and the mounting hole close to the impeller 4 , and the nozzle 11 is located beside the connection between the return passage 74 and the mounting hole.

[0050] A centrifugal compressor with bleed air recirculation control must first address the problem of returning high-pressure air to the vicinity of the inlet duct 61 entrance to recover a large amount of usable energy (reducing exergy losses). Preferably, the airflow in front of the diffuser, i.e., at the end of the airflow duct 62, is deflected toward the head of the impeller 4 through the recirculation duct 74. The nozzle 11 serves as the connection between the inlet duct 61 and the mounting hole. Located behind the connection between the recirculation duct 74 and the mounting hole, the nozzle 11 is closer to the impeller 4. Because the recirculated air is blocked by the impeller 4 along the compressor shaft 8, it flows smoothly into the inlet duct 61. Preferably, the nozzle 11 is an annular structure; air returning from different recirculation ducts 74 flows through the annular nozzle 11 into the adjacent inlet duct 61. The outer surface of the compressor shaft 8 and the central inlet duct hole form the jet nozzle 11. The compressor shaft 8 rotates at approximately 54,000 rpm, with a tangential velocity of 124 m / s on its outer surface. Together with the central hole, it forms a rotating plug-type annular converging-diverging nozzle. The high-pressure airflow exits the jet nozzle 11 at a high axial velocity toward the impeller 4. Due to its high tangential velocity, the air molecules disperse radially and circumferentially within the inlet passage 61, supercharging the main airflow entering the passage 61. Due to relative motion, the tangential velocity of the branch jet relative to the impeller 4 is nearly zero, but its axial momentum is significant, generating torque on the blade profile that propels the impeller 4 in rotation, thereby recovering the usable energy of the high-pressure air.

[0051] As an embodiment of the present invention, a notch 75 is provided near the end of the air flow channel 62 with a smaller cross-sectional area, and the notch 75 is communicated with the high-pressure air chamber 72 .

[0052] Before entering the diffuser, some high-pressure gas enters the high-pressure chamber 72 through the notch 75 and begins to vent and flow back. Preferably, the notch 75 is annular, allowing gas returning from different inlet passages 61 to enter the high-pressure chamber 72 through the notch 75. Both the high-pressure chamber 72 and the pressure-regulating chamber 73 are also annular in structure. The returning gas passes through the rotary vane 711 and enters the pressure-regulating chamber 73, where it is then diverted through different return passages 74 back to the different inlet passages 61 for circulation. Of course, the high-pressure chamber 72 and the pressure-regulating chamber 73 do not need to be annular. In this case, there are multiple high-pressure chambers 72, pressure-regulating chambers 73, and pressure-regulating assembly 71, with a one-to-one correspondence between the three. Accordingly, multiple notches 75 are also required to allow air to flow from the air flow passage 62 into the return passage 74.

[0053] As an embodiment of the present invention, the number of the intake channels 61 and the number of the return channels 74 are equal, namely, five, and they correspond one to one. The intake channels 61 are evenly distributed in the intake casing 1 .

[0054] The number of intake channels 61 and return channels 74 can be designed according to needs. Preferably, in a compressor of conventional size, five intake channels 61 are provided, and each intake channel 61 corresponds to a return channel 74, which can better control the intake and exhaust effects.

[0055] Example 2

[0056] The following is an embodiment of a centrifugal compressor of the present invention, including the above-mentioned air intake structure, diffuser, air guide wheel, compressor shaft 8, and motor, wherein the air guide wheel is installed at the front end of the air intake structure, the diffuser is installed at the rear end of the impeller 4, the compressor shaft 8 is installed in the mounting hole, and the motor is connected to the compressor shaft 8.

[0057] The guide wheel introduces air into the air intake structure. The air enters the air intake channel 61 and is formed into high-pressure gas through the centrifugal action of the impeller 4. Part of the air enters the diffuser from the end of the air flow channel 62, and part of it enters the high-pressure air chamber 72 from the gap 75, passes through the pressure regulating component 71 and enters the pressure regulating air chamber 73, and then returns to the end of the impeller 4 in the air intake channel 61 through the return channel 74, and starts a new round of air intake under the action of the impeller 4 together with the newly entered gas.

[0058] The centrifugal compressor of the present invention has a bleed air reflux control function, and can achieve a higher compression ratio and a wider high-efficiency working area.

[0059] Example 3

[0060] The following is an embodiment of a turboprop engine according to the present invention, comprising an engine body and a centrifugal compressor as described above, wherein the centrifugal compressor is installed in the engine body.

[0061] The engine of the present invention has a high surge margin, can broaden the stable operating speed range, and reduce fuel consumption. Since the turbine speed in some low-power working conditions is reduced by (30-40)%, the noise level is significantly reduced.

[0062] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An air intake structure, characterized in that: The invention comprises an air intake casing (1), an outer cover (2), an impeller cover (3), an impeller (4), and an isolation flange (5). The air intake casing (1) is connected to the outer cover (2). The outer cover (2) is arranged outside the impeller (4) and the impeller cover (3). The impeller cover (3) is arranged outside the impeller (4). An air flow channel (62) is formed between the impeller (4) and the impeller cover (3). Along the air flow direction, the cross-sectional area of the air flow channel (62) is changed from large to small. The air intake casing (1) is provided with a mounting hole for mounting a compressor shaft (8), and the mounting hole is coaxially arranged with the impeller (4). A plurality of air intake channels (61) are provided in the air intake casing (1), and the ends of the air intake channels (61) along the air flow direction are connected with the air flow channels (62). The air intake casing (1) also includes an air release reflux structure for adjusting the amount of gas reflux, and the air release reflux structure is connected with the air intake channel (61) and the air flow channel (62) respectively. The air release reflux structure includes a pressure regulating assembly (71), a high-pressure air chamber (72), a pressure regulating air chamber (73), and a plurality of reflux channels (74). The high-pressure air chamber (72) is surrounded by the outer cover (2), the isolation flange (5), and the impeller cover (3). The pressure regulating air chamber (73) is surrounded by the air intake casing (1), the impeller cover (3), and the isolation flange (5). The high-pressure air chamber (72) and the pressure-regulating air chamber (73) are separated on both sides of the isolation flange (5). A through hole is provided on the isolation flange (5) to connect the high-pressure air chamber (72) and the pressure-regulating air chamber (73). The pressure-regulating assembly (71) is installed at the through hole of the isolation flange (5). The high-pressure air chamber (72) is connected to the air flow channel (62). One end of the return channel (74) is connected to the pressure-regulating air chamber (73), and the other end is connected to the air inlet channel (61).

2. The air intake structure according to claim 1, characterized in that: The pressure regulating assembly (71) comprises a rotary valve (711), a driving motor (712), a controller, an air pressure sensor and a temperature sensor. The air pressure sensor and the temperature sensor are both installed in the pressure regulating air chamber (73). The rotary valve (711) is located at the through hole. The rotary valve (711) is connected to the driving motor (712), and the driving motor (712) is connected to the controller signal.

3. The air intake structure according to claim 1, characterized in that: The return channel (74) is connected to the mounting hole. The return channel (74) is arranged close to the mounting hole and toward the impeller (4). The axis of the return channel (74) and the axis of the mounting hole form an inclination angle α, and the inclination angle α is 30° to 40°.

4. The air intake structure according to claim 1, characterized in that: A nozzle (11) is provided at the end of the air inlet channel (61) and the mounting hole close to the impeller (4), and the nozzle (11) is located beside the connection point between the return channel (74) and the mounting hole.

5. The air intake structure according to claim 4, characterized in that: The air flow channel (62) is provided with a notch (75) near the end portion with a smaller cross-sectional area, and the notch (75) is communicated with the high-pressure air chamber (72).

6. The air intake structure according to claim 5, characterized in that: The high-pressure air chamber (72), the pressure-regulating air chamber (73), the nozzle (11), and the notch (75) are all annular structures.

7. The air intake structure according to any one of claims 1 to 6, characterized in that: The number of the air intake channels (61) and the return channels (74) are equal, both being 3 to 5, and corresponding one to one. The air intake channels (61) are evenly distributed in the air intake casing (1).

8. A centrifugal compressor, characterized in that: The invention comprises an air intake structure as described in any one of claims 1 to 7, a diffuser, an air guide wheel, a compressor shaft (8), and a motor, wherein the air guide wheel is installed at the front end of the air intake structure, the diffuser is installed at the rear end of the impeller (4), the compressor shaft (8) is installed in the mounting hole, and the motor is connected to the compressor shaft (8).

9. A turboprop engine, characterized in that: It comprises an engine body and the centrifugal compressor as claimed in claim 8, wherein the centrifugal compressor is installed in the engine body.

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