Turbocharger with bleed air braking function

Abstract

A turbocharger with a bleed air brake function relates to the technical field of internal combustion engine supercharging devices and comprises a turbine, the turbine comprises a volute, and a turbine is rotatably arranged in the volute; a first flow channel and a second flow channel which are used for introducing waste gas are arranged on the volute, the first flow channel is communicated with a turbine flow channel, the second flow channel is communicated with a turbine back disc through a perforated heat insulation cover, and a flow channel switching mechanism which is used for connecting and disconnecting the first flow channel or the second flow channel is arranged on the volute. The problems that in the prior art, after an exhaust brake valve is closed, axial force borne by a thrust bearing is instantly and greatly improved compared with axial force in a normal working state, so that the bearing capacity of the thrust bearing is insufficient, and abrasion of the thrust bearing is accelerated are solved; and the exhaust pressure of the engine cannot be released, so that air leaks from a gap between a sealing ring at the turbine end and a sealing ring groove.

Description

Technical Field

[0001] The present invention relates to the technical field of internal combustion engine supercharging devices, and particularly to a turbocharger with an air bleeding braking function. Background Art

[0002] For commercial vehicles used for freight or long-distance passenger transport, when driving on long downhill slopes or slippery roads such as ice, snow, and mud, frequent use of brakes will cause the brake system to overheat, thereby reducing its braking efficiency and accelerating the wear of brake pads and tires, posing a great hidden danger to driving safety. To overcome the above problems, installing an exhaust braking device at the outlet of the engine turbine for auxiliary braking is being increasingly applied.

[0003] An exhaust braking device generally includes an exhaust brake valve and its actuator. When the vehicle is driving on a road that requires long-time braking and deceleration, the driver activates the exhaust braking device to close the valve installed on the exhaust pipe, increasing the exhaust resistance of the engine, thereby increasing the back pressure in the exhaust stroke. This back pressure acts reversely on the piston along the entire exhaust pipe path, generating a reverse torque, consuming the kinetic energy of the engine operation, reducing the engine speed, and then reducing the vehicle speed. This process not only reduces the dependence on the traditional friction braking system but also reduces the risk of wheel locking and improves the vehicle stability.

[0004] As Figure 1 shown, to solve the problem that when the vehicle is driving on long downhill slopes, ice, snow, and muddy roads, it is necessary to continuously use brakes to maintain the vehicle speed, which easily causes the brake pads to wear out faster, shortens the service life of the brake pads, and even causes them to fail. Generally, the measure taken is to install an exhaust brake valve 4 at the exhaust end of the engine turbine. When in an extreme road condition, the exhaust brake valve 4 is closed, and the exhaust back pressure of the engine increases rapidly, increasing the exhaust resistance of the engine, thereby consuming the engine power, reducing its speed, and playing an auxiliary braking function, greatly reducing the use frequency of the brake system. However, when the exhaust brake valve 4 is closed instantaneously, the pressures at the inlet and outlet of the turbine 1 reach the same instantaneously, so that the axial force pointing in the direction of its outlet generated during the normal operation of the turbine 1 disappears. However, due to the inertia of the rotor, the axial force of the compressor 19 can still exist for a period of time, resulting in a significant increase in the axial force in a short time after the exhaust braking, causing the load-bearing capacity of the thrust bearing 15 to be insufficient. If the thrust bearing 15 is designed with a load-bearing capacity according to the axial force required for exhaust braking, then during normal operation, the friction work loss of the thrust bearing 15 will increase, thereby deteriorating the fuel economy and responsiveness of the engine. In addition, after the exhaust brake valve 4 is closed, the exhaust pressure of the engine cannot be released, causing the entire turbine flow passage 203 to be instantly filled with high-pressure gas, which is extremely likely to cause air leakage from the gap between the seal ring 18 at the turbine end and the seal ring groove 1301, and the high-temperature gas enters the chamber of the bearing body 12, posing risks of overheating of the bearing system and coking of the engine oil.

[0005] With the use of the prior art including the above-mentioned device, the deficiencies of this technology have gradually emerged, mainly manifested in the following aspects: First, in the short time after the exhaust brake valve is closed and the axial force balance effect of the turbine head is lost, the axial force borne by the thrust bearing will instantaneously increase significantly compared to the axial force in the normal working state, thus causing insufficient bearing capacity of the thrust bearing, accelerating its wear, and increasing the failure rate of the turbocharger.

[0006] Second, after the exhaust brake valve is closed, the exhaust pressure of the engine cannot be released, causing the entire turbine flow path to be instantly filled with high-pressure gas, which is extremely likely to lead to air leakage through the gap between the seal ring and the seal ring groove at the turbine end. High-temperature gas enters the bearing body chamber, posing risks of overheating of the bearing system and coking of the engine oil.

[0007] In summary, it is obvious that the prior art has inconveniences and defects in actual use, so it is necessary to make improvements. Summary of the Invention

[0008] Aiming at the defects in the prior art, the present invention solves the problems that after the exhaust brake valve in the traditional technology is closed, the axial force borne by the thrust bearing will instantaneously increase significantly compared to the axial force in the normal working state, thus causing insufficient bearing capacity of the thrust bearing and accelerating its wear; and the exhaust pressure of the engine cannot be released, resulting in air leakage through the gap between the seal ring and the seal ring groove at the turbine end.

[0009] To solve the above problems, the present invention provides the following technical solutions: A turbocharger with an air-introducing braking function, including a turbine, and the turbine includes a volute, and a turbine is rotatably provided in the volute; A first flow path and a second flow path for introducing exhaust gas are provided on the volute, the first flow path is communicated with the turbine flow path, The second flow path is communicated with the back plate of the turbine through an opening heat insulation cover, A flow path switching mechanism for switching on and off the first flow path or the second flow path is provided on the volute.

[0010] As an optimized solution, the inlet of the opening heat insulation cover is communicated with the second flow path in the entire circumferential direction.

[0011] As an optimized solution, a plurality of jet through holes are evenly distributed in the circumferential direction on the mating wall surface of the opening heat insulation cover and the back plate of the turbine.

[0012] As an optimized solution, the jet through holes are equal-diameter through holes or variable-diameter through holes, and the cross section of the jet through holes is circular, rectangular or elliptical.

[0013] As an optimized solution, the total cross-sectional area of several of the jet through-holes accounts for 5-40% of the cross-sectional area of the first flow channel.

[0014] As an optimized solution, the turbine includes an open back disk, the radial position of the jet through-holes is between the turbine back disk and the inlet rim of the turbine blade, the jet through-holes have a tangential angle in the circumferential direction, and the angle between the axis of the jet through-holes and the tangential direction is 20-60°.

[0015] As an optimized solution, the turbine includes a closed back disk, the distance between the jet through-holes and the turbine center is less than the distance between the rim of the turbine back disk and the turbine center, and the axis of the jet through-holes is perpendicular to the turbine back disk.

[0016] As an optimized solution, the flow channel switching mechanism includes a cubic valve body housing connected to the volute. The cubic valve body housing is provided with a first inlet communicating with the first flow channel and a second inlet communicating with the second flow channel. The cross-sectional area of the second inlet is not greater than that of the first inlet. A valve body for opening and closing the first inlet or the second inlet is swingably provided in the cubic valve body housing.

[0017] As an optimized solution, the spatial volume of the second flow channel accounts for 20-50% of the spatial volume of the first flow channel.

[0018] As an optimized solution, an external actuator for driving the valve body to swing is fixed on the outer wall of the cubic valve body housing.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: By providing a flow channel switching mechanism at the inlet of the traditional supercharger volute, when the engine needs auxiliary braking, the engine exhaust can be introduced into the second flow channel, and the gas flowing out quickly from the jet through-holes on the open-hole heat insulation cover can be used, or it can be sprayed onto the suction surface of the turbine blade inlet, thereby generating a turbine rotation braking force, causing the speed of the compressor to drop rapidly, and greatly shortening the time when the thrust bearing is subjected to a high axial force load; or it can be sprayed onto the wall surface of the turbine back disk, and the stagnation pressure is used to make the turbine still have a certain axial force to balance the axial force of the compressor, so that the maximum axial force received by the thrust bearing is reduced; The present invention has the characteristics of simple structure, convenient implementation and low cost. It can effectively solve the problems that the impeller braking time is long during exhaust braking of the traditional turbocharger rear exhaust brake valve and the axial force of the impeller has no axial force of the turbine to balance it. Therefore, it can effectively reduce the phenomenon of thrust bearing wear caused by exhaust braking, and can reduce the flow rate of high-temperature exhaust gas leaking into the bearing body, improving the reliability and service life of the turbocharger. Brief Description of the Drawings

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0021] Figure 1 is a schematic structural diagram of the prior art; Figure 2 is a schematic structural diagram of Embodiment 1; Figure 3 is Figure 2 an enlarged structural diagram of part A in Figure 4 is Figure 2 a sectional structural diagram taken along the F-F direction in Figure 5 is a schematic structural diagram of the flow path switching mechanism of the present invention; Figure 6 is a schematic structural diagram of the external execution mechanism of the present invention; Figure 7 is a schematic structural diagram of the cross-section of the opening heat insulation cover of Embodiment 1; Figure 8 is Figure 2 a sectional structural diagram taken along the E-E direction in Figure 9 is a schematic structural diagram of Embodiment 2; Figure 10 is Figure 9 an enlarged structural diagram of part B in Figure 11 is a schematic structural diagram of the cross-section of the opening heat insulation cover of Embodiment 2.

[0022] In the figure: 1 - turbine, 2 - turbine wheel, 201 - inlet suction surface of turbine blade, 202 - turbine back plate, 203 - turbine flow passage, 204 - open back plate, 205 - closed back plate, 206 - inlet rim of turbine blade, 3 - volute, 301 - double inlet passage, 302 - first inlet, 303 - first flow passage, 304 - second inlet, 305 - second flow passage, 306 - inlet partition plate, 307 - cross-section of first flow passage, 4 - exhaust brake valve, 5 - flow passage switching mechanism, 6 - cube valve body housing, 601 - flange of opening one, 602 - flange of opening two, 7 - valve body housing cover plate, 701 - boss of shaft sleeve, 8 - valve body, 801 - valve body rotating shaft, 9 - external actuator, 901 - actuator rotating shaft, 10 - coupling, 11 - perforated heat shield, 1101 - inner cavity of perforated heat shield, 1102 - jet through hole, 12 - bearing body, 1201 - bearing housing, 1202 - volute end stop, 1203 - bearing seat, 1204 - pressure end stop, 13 - turbine shaft, 1301 - seal ring groove, 14 - floating bearing, 15 - thrust bearing, 16 - thrust sleeve, 17 - shaft seal, 18 - seal ring, 19 - compressor, 20 - compressor impeller, 21 - lock nut, 22 - compressor housing. Detailed implementation manners

[0023] Hereinafter, embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and therefore are only examples and cannot be used to limit the protection scope of the present invention.

[0024] Embodiment 1 As Figures 2 to 8 shown, a turbocharger with an air bleeding braking function includes a turbine 1, the turbine 1 includes a volute 3, and a turbine wheel 2 is rotatably arranged in the volute 3; The volute 3 is provided with a first flow passage 303 and a second flow passage 305 for introducing exhaust gas, the first flow passage 303 is communicated with the turbine flow passage 203, the second flow passage 305 is communicated with the turbine back plate 202 through a perforated heat shield 11, and the volute 3 is provided with a flow passage switching mechanism 5 for opening and closing the first flow passage 303 or the second flow passage 305.

[0025] The inlet of the perforated heat shield 11 is communicated with the second flow passage 305 in the entire circumferential direction.

[0026] A plurality of jet through holes 1102 are evenly distributed along the circumferential direction on the mating wall surface of the perforated heat shield 11 and the turbine back plate 202.

[0027] The jet through holes 1102 are equal-diameter through holes or variable-diameter through holes, and the cross-section of the jet through holes 1102 is circular, rectangular or elliptical.

[0028] The total cross-sectional area of a plurality of jet through-holes 1102 accounts for 5-40% of the cross-sectional area of the first flow channel 303.

[0029] The turbine 2 includes an open back disk 204. The radial position of the jet through-holes 1102 is between the turbine back disk 202 and the inlet rim 206 of the turbine blade. The jet through-holes 1102 have a tangential angle in the circumferential direction, and the angle between the axis of the jet through-holes 1102 and the tangential direction is 20-60°.

[0030] The turbine 2 includes a closed back disk 205. The distance between the jet through-holes 1102 and the center of the turbine 2 is less than the distance between the rim of the turbine back disk 202 and the center of the turbine 2, and the axis of the jet through-holes 1102 is perpendicular to the turbine back disk 202.

[0031] The flow channel switching mechanism 5 includes a cubic valve body housing 6 connected to the volute 3. Inside the cubic valve body housing 6, there is a first inlet 302 communicating with the first flow channel 303 and a second inlet 304 communicating with the second flow channel 305. The cross-sectional area of the second inlet 304 is not greater than the cross-sectional area of the first inlet 302. A valve body 8 that opens and closes the first inlet 302 or the second inlet 304 is swingably provided inside the cubic valve body housing.

[0032] The space volume of the second flow channel 305 accounts for 20-50% of the space volume of the first flow channel 303.

[0033] An external actuator 9 for driving the valve body 8 to swing is fixed on the outer wall of the cubic valve body housing 6.

[0034] The open-cell heat shield 11 is fixed in the area between the volute 3, the turbine back disk 202, and the bearing housing 1201.

[0035] It further includes a turbine 1, a compressor 19, and a bearing body 12. The turbine 2 is a radial-flow turbine or a mixed-flow turbine. A volute 3 is arranged outside the turbine 2, and a tip clearance is left between the volute 3 and the tip of the turbine 2 blades.

[0036] A dual-inlet channel 301 is arranged at the inlet position of the volute 3 flow channel, where the first inlet 302 communicates with the first flow channel 303 and the second inlet 304 communicates with the second flow channel 305.

[0037] Among them, the first flow channel 303 is in a vortex shape, and its outlet communicates with the turbine flow channel 203. The second flow channel 305 has a circumferentially uniform structure.

[0038] The cross-sectional area of the second inlet 304 is less than or equal to the cross-sectional area of the first inlet 302. The space volume of the second flow channel 305 is 20-50% of the volume of the first flow channel 303; a flow channel switching mechanism 5 is arranged outside the dual-inlet channel 301.

[0039] The flow path switching mechanism 5 is composed of a cubic valve body shell 6, a valve body shell cover plate 7, a valve body 8, and an external actuator 9.

[0040] The cubic valve body shell 6 and the volute 3 are integrally castings. There are two openings on the outer side of the cubic valve body shell 6. An opening one flange 601 and an opening two flange 602 are correspondingly arranged for the two openings. The opening one flange 601 is used to connect the engine exhaust pipe flange; the opening two flange 602 is used to connect with the valve body shell cover plate 7 and is fastened by bolts.

[0041] Fitting stop mouths are arranged on both the cubic valve body shell 6 and the valve body shell cover plate 7 to realize the radial and circumferential positioning of the two.

[0042] The valve body 8 has a flat structure. The shape of the valve body 8 is similar to that of the first inlet 302 and the second inlet 304, but the area is larger than the areas of these two channel inlets; a valve body rotating shaft 801 is arranged on one side of the valve body 8. The valve body rotating shaft 801 is installed at the position of the inlet partition plate 306 in the middle of the first inlet 302 and the second inlet 304; the thickness of the valve body 8 is 1 - 3 mm. Driven by the external actuator 9, it can rotate no less than 180°, that is, the valve body 8 can be in a state of completely blocking the first inlet 302 or in a state of completely blocking the second inlet 304; the valve body rotating shaft 801 is inserted into the inner hole of the shaft sleeve boss 701 and has a clearance fit with the inner hole of the shaft sleeve boss 701.

[0043] The valve body rotating shaft 801 is connected to a coupling 10 on the outer side of the valve body shell cover plate 7, and the other end of the coupling 10 is connected to the actuator rotating shaft 901 of the external actuator 9.

[0044] The external actuator 9 is a motor servo mechanism or a pneumatic actuator.

[0045] The perforated heat insulation cover 11 has a cast thin shell structure. This part realizes axial pressing and limiting through the bolts fastening of the bearing shell 1201 and the volute 3 at the volute end stop 1202, and its radial position is realized by the interference fit with the inner diameter of the volute end stop 1202.

[0046] The inlet of the inner cavity 1101 of the perforated heat insulation cover communicates with the outlet of the second flow path 305 in the entire circumferential direction; a plurality of jet through holes 1102 are circumferentially distributed on the wall surface of the perforated heat insulation cover 11 that cooperates with the turbine back disk 202; the wall thickness of the perforated heat insulation cover 11 is 1 - 3 mm, and the hole cross-sectional area is 0.8 - 7 mm 2 and the number of through holes evenly distributed in the circumference is 6 - 20.

[0047] The turbine 2 has an open back disk 204. The radial position of the jet through-hole 1102 is between the turbine back disk 202 and the inlet rim 206 of the turbine blade. The jet through-hole 1102 has a tangential angle in the circumferential direction. The angle between the axis of the jet through-hole 1102 and the tangential direction is 20 - 60°. The axis of the jet through-hole 1102 points in the opposite direction of the turbine rotation, so that the area of the cross-section of the jet through-hole 1102 projected along its axis can all fall on the suction surface 207 of the turbine blade.

[0048] The bearing body 12 includes a bearing housing 1201, a turbine shaft 13, a floating bearing 14, a thrust bearing 15, a thrust collar 16, a shaft seal 17, and a sealing ring 18.

[0049] The compressor 19 includes a compressor impeller 20, a locking nut 21, and a compressor housing 22.

[0050] The sealing ring 18, the floating bearing 14, the thrust collar 16, the thrust bearing 15, the shaft seal 17, and the compressor impeller 20 are sequentially sleeved on the turbine shaft 13 and locked at the end of the turbine shaft 13 with the locking nut 21, so that the above parts are fastened.

[0051] There is a clearance fit between the floating bearing 14 and the turbine shaft 13 as well as between the floating bearing 14 and the bearing seat 1203; the turbine shaft 13 is a multi-step shaft, with a sealing ring groove 1301 provided on the thickest shaft and an external thread designed at the end of the thinnest shaft; a sealing ring 18 is provided between the sealing ring groove 1301 and the bearing housing 1201 as well as between the shaft seal 17 and the bearing housing 1201; a compressor housing 22 is provided outside the compressor impeller 20, with a clearance fit between the compressor housing 22 and the compressor impeller 20, and the compressor housing 22 is fastened to the press end stop 1204 of the bearing housing 1201 through bolts and a pressing plate.

[0052] Embodiment 2 Such as Figures 9 to 11 , when the turbine 2 has a closed back disk 205, the radial position where the jet through-hole 1102 is located is less than the rim of the turbine back disk 202, and its axis is perpendicular to the turbine back disk 202, and the rest of the structure is the same as that of Embodiment 1.

[0053] The working principle of this device is as follows: In the present invention, the exhaust brake valve installed behind the turbine of the turbocharger is cancelled, a flow path switching mechanism is provided in the front section of the inlet of the volute, and the volute is designed as a double-flow volute; In the flow path switching mechanism 5 of the present invention, the valve body 8 can be in one of two states under the action of the external actuator 9; these two states are respectively: State 1: Open the first flow path 303 and close the second flow path 305; State 2: Close the first flow path 303 and open the second flow path 305.

[0054] When the valve body 8 is in the first state, the high-temperature gas discharged from the engine enters the first flow channel 303 after passing through the opening one flange 601 and entering the flow channel switching mechanism 5; the high-temperature exhaust gas expands therein, flows out of the volute 3 at a certain speed, and then enters the turbine flow channel 203 to expand and do work, converting a part of the internal energy, kinetic energy, and pressure energy into the rotational mechanical energy of the turbine 2, and pushing the compressor impeller 20 to rotate and compress to do work.

[0055] When the vehicle is driving on a road condition that requires auxiliary braking, the valve body 8 is in the second state under the action of the external actuator 9. At this time, the exhaust gas discharged from the engine enters the second flow channel 305 after passing through the opening one flange 601 and entering the flow channel switching mechanism 5, and then, under the action of a large pressure difference, quickly sprays out through the jet through-holes 1102 evenly distributed in the circumferential direction on the opening heat insulation cover 11.

[0056] Since the volume of the second flow channel 305 is designed to be 20 - 50% of that of the first flow channel 301, and the total area of the jet through-holes 1102 is designed to be 5 - 40% of the cross-section 307 of the first flow channel, when the high-temperature exhaust gas passes through the second flow channel 303, the flow of the gas will generate a great resistance, which can also cause the pressure in front of the turbine to increase significantly instantaneously when the valve body switches, playing a role in increasing the exhaust back pressure of the engine, thereby enabling the engine to generate auxiliary braking.

[0057] When the axis of the jet through-hole 1102 on the opening heat insulation cover 11 has a certain tangential angle and faces the suction surface 201 of the turbine blade inlet, a relatively small amount of high-speed gas flowing out of the opening heat insulation cover 11 can impact the suction surface 201 of the turbine blade inlet, that is, a braking force that prevents the turbine 2 from rotating can be generated, which can quickly reduce the rotational speed of the compressor impeller 20 rotating coaxially, thereby significantly accelerating the reduction speed of the axial force of the turbine shaft 13, reducing the high-load bearing time of the thrust bearing 15, and effectively reducing its wear.

[0058] When the distance between the jet through-hole 1102 and the center is less than the diameter of the closed back disk 205, the gas flowing out quickly from the jet through-hole 1102 will impact the wall surface of the closed back disk 205, and the pressure of this wall surface will increase under the action of the stagnation pressure, so that the axial force that disappears at the turbine exhaust end in the normal exhaust braking state can be restored to a certain extent, so that a certain axial force at the turbine end can be provided under the exhaust braking to balance the axial force at the compressor end, reducing the axial force that the thrust bearing 15 needs to bear under the exhaust braking, effectively reducing its wear, and increasing the service life of the thrust bearing 15.

[0059] In addition, when the high-temperature combustion gas flows through the jet through-hole 1102, due to the throttling effect of the jet through-hole 1102, the jet velocity increases significantly while the pressure decreases significantly. Therefore, the air pressure in the gap between the turbine back disk 202 and the perforated heat shield 11 is relatively low, thus avoiding the risk of excessive pressure in the turbine flow passage 203 caused by the traditional exhaust braking method and increasing the leakage of high-temperature combustion gas to the bearing body 12.

[0060] When the engine needs exhaust braking, on the one hand, the present invention can guide the high-pressure exhaust gas into the inner cavity 1101 of the opening heat shield and then spray it onto the suction surface 207 of the turbine blade or the turbine back disk 202 through the jet through-hole 1102, which can quickly reduce the rotational speed of the compressor impeller 20 or increase the axial force for balance of the turbine back disk 202, solving the problem that the axial force is instantaneously too large and the thrust bearing 15 is prone to overload failure when the exhaust brake valve 4 is installed behind the turbine for exhaust braking; on the other hand, due to the throttling effect of the jet through-hole 1102, the air flow pressure entering the turbine flow passage 203 decreases, significantly reducing the air leakage amount of the high-temperature combustion gas from the gap between the sealing ring 18 and the sealing ring groove 1301 to the bearing body 12, and improving the problem that the traditional exhaust braking device is prone to cause high-temperature overheating of the components of the bearing body 12 and coking of the engine oil.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A turbocharger with an air bleeding braking function, characterized in that: It includes a turbine (1), and the turbine (1) includes a volute (3), and a turbine (2) is rotatably provided in the volute (3); The volute (3) is provided with a first flow channel (303) and a second flow channel (305) for introducing exhaust gas. The first flow channel (303) is communicated with the turbine flow channel (203), The second flow channel (305) is communicated with the turbine back plate (202) through an open-hole heat insulation cover (11), The volute (3) is provided with a flow channel switching mechanism (5) for switching on and off the first flow channel (303) or the second flow channel (305).

2. The turbocharger with an air bleeding braking function according to claim 1, characterized in that: The inlet of the open-hole heat insulation cover (11) is communicated with the second flow channel (305) in the entire circumferential direction.

3. The turbocharger with an air bleeding braking function according to claim 1, characterized in that: A plurality of jet through-holes (1102) are evenly distributed along the circumferential direction on the mating wall surface of the open-hole heat insulation cover (11) and the turbine back plate (202).

4. The turbocharger with an air bleeding braking function according to claim 3, characterized in that: The jet through-holes (1102) are equal-diameter through-holes or variable-diameter through-holes, and the cross-section of the jet through-holes (1102) is circular, rectangular or elliptical.

5. The turbocharger with an air bleeding braking function according to claim 3, characterized in that: The total cross-sectional area of the plurality of jet through-holes (1102) accounts for 5-40% of the area of the first flow channel cross-section (307).

6. The turbocharger with air bleeding braking function according to claim 3, wherein: The turbine (2) includes an open back plate (204). The radial position of the jet through-holes (1102) is between the turbine back plate (202) and the turbine blade inlet rim (206). The jet through-holes (1102) have a tangential angle in the circumferential direction, and the angle between the axis of the jet through-holes (1102) and the tangential direction is 20-60°.

7. The turbocharger with an air bleeding braking function according to claim 3, characterized in that: The turbine (2) includes a closed back plate (205). The distance between the jet through-holes (1102) and the center of the turbine (2) is less than the distance between the rim of the turbine back plate (202) and the center of the turbine (2), and the axis of the jet through-holes (1102) is perpendicular to the turbine back plate (202).

8. The turbocharger with an air bleeding braking function according to claim 1, characterized in that: The flow channel switching mechanism (5) includes a cubic valve body housing (6) connected to the volute (3). The cubic valve body housing (6) is provided with a first inlet (302) communicated with the first flow channel (303) and a second inlet (304) communicated with the second flow channel (305). The cross-sectional area of the second inlet (304) is not larger than the cross-sectional area of the first inlet (302). A valve body (8) for switching on and off the first inlet (302) or the second inlet (304) is swingably provided in the cubic valve body housing (6).

9. The turbocharger with an air bleeding braking function according to claim 1, wherein: The space volume of the second flow channel (305) accounts for 20-50% of the space volume of the first flow channel (303).

10. The turbocharger with an air bleeding braking function according to claim 8, characterized in that: An external actuator (9) for driving the valve body (8) to swing is fixed on the outer wall of the cubic valve body housing (6).

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