JP3399063B2 - Turbine heat shield - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine heat shield device, and more particularly to a turbine that rotates by using the flow velocity of a high-temperature fluid, and a drive source for rotating the turbine. TECHNICAL FIELD The present invention relates to a turbine heat shield device suitable for shielding heat in a turbine-side space and an impeller-side space in a supercharger provided with a back-to-back impeller that rotates and pumps a low-pressure fluid. 2. Description of the Related Art For example, a supercharger such as a so-called turbocharger mounted on a vehicle rotates an impeller directly connected to a turbine by a rotating shaft by rotating the turbine at high speed by exhaust gas of an internal combustion engine. Then, high-pressure air is generated by air compression by the centrifugal effect, and the generated high-pressure air is introduced into the combustion chamber. [0003] In this case, the exhaust gas guided to rotate the turbine is generally hot, whereas the temperature of the air pumped by the impeller is low from the viewpoint of increasing the density of the air supplied to the combustion chamber. desirable. On the other hand, the positions of the turbine and the impeller are
It is desirable that they are close from the viewpoint of reducing the size of the turbocharger.However, in order to dispose the two close together, it is necessary to adopt such a configuration and still make the space on the turbine side and the space on the impeller side enough. There is a need for a turbine heat shield device that can shield heat. An example of such a turbine heat shield device is disclosed in Japanese Patent Application No. 5-262608. FIG. 5 shows an overall configuration diagram of a turbocharger 20 incorporating such a heat shield device. A turbocharger 20 shown in FIG. 1 has a turbine 1 and an impeller 2 arranged back to back, and bearings 3 and 3.
4 is a cantilevered configuration. In this case, the turbine 1 is a member that is exposed to a high-temperature exhaust gas or a combustion gas introduced by winding around the outer periphery thereof, and has a high temperature during operation of the turbocharger 20. Therefore, radiant heat is radiated from the back surface of the turbine disk 1a, and if no measures are taken, the intake air flowing through the impeller 2, the impeller disk 2a, and the air flow path 2b is heated, and the intake density is reduced. As a result, the efficiency of the compressor (compressor) is reduced. For this reason, the turbo jar 20 shown in FIG.
In (2), a heat shield plate 21 is provided between the turbine 1 and the impeller 2 to shield the radiant heat. The heat shield plate 21 is attached to a first plate 22 located on the impeller 2 side, a second plate 23 located on the turbine 1 side, and a rotating shaft 5 connecting the turbine disk 1a and the impeller disk 2a. Opposing labyrinth 24 and blade 25
It is composed of The plate members 22 and 23 are joined so as to form a gap 26 inside the heat shield plate 21. The plate-shaped body 22 has a space 2 on the impeller disk 2a side.
A first ventilation hole 22a is formed to communicate the air gap 7 with the gap 26 near the outermost diameter of the impeller disk 2a, while the plate-like body 23 has a space 2 on the turbine disk 1a side.
8 and the gap 26 with the rotating shaft 5 of the turbine disk 1a.
A second ventilation hole 23a communicating with the vicinity is formed. The rotary shaft 5 has a rotary shaft center hole 6 at the center thereof, and has an air supply hole 7 communicating the rotary shaft center hole 6 with the space 27 and a rotary shaft center hole 6 and the rotary shaft 5. An air discharge hole 9 that communicates with the fitted labyrinth blade 8 is provided. Furthermore, the labyrinth blade 8
It is provided in communication with the upstream space 2 d of the impeller 2. In this configuration, when the impeller disk 2a rotates with the rotation of the turbine disk 1a and high-pressure compressed air is generated in the space 27, the generated high-pressure compressed air is transmitted to the internal combustion engine that communicates with the air flow path 2b. It is guided into the space 27 while being introduced into the intake passage. Then, it flows through the surface of the plate-like body 22 of the heat shield plate 21 or passes between the back surface of the turbine disk 1a and the plate-like body 23 through the first ventilation hole 22a, the gap 26, and the second ventilation hole 22b. It flows into the formed space 28. Thus, the turbine disk 1a is cooled, and a heat insulating air layer is formed in the gap 26. In this case, despite the fact that the turbine 1 and the impeller 2 are provided back to back, radiation of radiant heat from the turbine 1 to the impeller 2 is suppressed, and high efficiency as a compressor in the turbocharger 20 is secured. can do. However, the above-mentioned conventional turbine heat shield device supplies high-pressure compressed air to a heat shield plate 21 disposed between the turbine 1 and the impeller 2. It is. That is, in the conventional turbine heat shield device, part of the high-pressure compressed air originally compressed to increase the intake pressure of the internal combustion engine is consumed as cooling air, and the compression efficiency of the turbocharger decreases. It is accompanied by. Further, the high-pressure compressed air has a higher temperature than the low-pressure air before compression due to the temperature increase in the compression, so that the cooling efficiency is lower than when the low-pressure air at normal temperature is used for cooling the heat shield plate 21. Also have. The present invention has been made in view of the above points, and has a heat shield plate provided between a turbine and an impeller, and the heat shield plate is cooled by air before being compressed by the impeller. An object of the present invention is to provide a turbine heat shield device that solves the above problems. SUMMARY OF THE INVENTION The object of the present invention is to provide a turbocharger having a back-to-back turbocharger having a turbine rotating by the flow velocity of a high-temperature fluid and an impeller rotating by using the turbine as a driving source to pump low-pressure fluid. Inside the machine, a turbine heat shield device that shields the space on the turbine side and the space on the impeller side, which is disposed between the turbine and the impeller,
A heat shield plate having a cavity inside, and above the impeller
A shroudka which is a space on the flow side and covers the impeller.
A cooling fluid inflow passage communicating the first space near the root of the bar with the gap of the heat shield plate; and a space upstream of the impeller, wherein the pressure is lower than the first space during rotation of the impeller. This is achieved by a turbine heat shield device including a cooling fluid discharge passage that communicates a second space to be formed with a gap of the heat shield plate. In the turbine heat shield according to the present invention, the heat shield plate is interposed between the turbine and the impeller, and radiant heat radiated from the turbine is directly transmitted to the impeller. To prevent At this time, the gap provided in the heat shield plate functions as a heat insulating air layer, and functions to delay the transfer of the radiant heat supplied from the turbine side to the heat shield plate to the impeller side. The cooling fluid inflow passage is provided in the first space upstream of the impeller, and the cooling fluid discharge passage is provided in the second space having a lower pressure than the first space when the impeller is operated. , And communicate with each other via a gap in the heat shield plate. Therefore, during the operation of the impeller, the cooling fluid is discharged from the cooling fluid inflow passage through the gap of the heat shield plate due to the pressure difference between the first space and the second space. A flow of air is formed that escapes to the passage. This air does not consume the high-pressure compressed air pressurized by the rotation of the impeller, and since it is relatively low-temperature normal-pressure air, high heat shielding without lowering the compression efficiency as a supercharger. The effect will be obtained. FIG. 1 is an overall structural view of a turbocharger 30 incorporating a turbine heat shield device according to an embodiment of the present invention. The turbine heat shield according to the present embodiment differs from the turbine heat shield described with reference to FIG. 5 only in the structure around the heat shield plate, and other structures are almost the same. For this reason,
In the apparatus of this embodiment, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be simplified. The turbocharger 30 incorporating the turbine heat shield according to the present embodiment also has the turbine 1 and the impeller back-to-back, as well as the conventional turbocharger shown in FIG. It is designed to be cantilevered. That is, the turbine disk 1
a and the impeller disk 2a are coaxially fitted by the rotating shaft 5, and are supported by the bearings 3 and 4, and rotate integrally. Here, the turbocharger 30 is a device incorporated in, for example, an internal combustion engine, a gas turbine engine, or the like, which generates high-pressure compressed air in an intake system using exhaust energy to improve the output of the internal combustion engine or the like. The exhaust gas introduction passage 31 provided on the outer periphery of the turbine 1 has
An exhaust port (hereinafter, simply referred to as an exhaust port) of an internal combustion engine or the like is connected. The exhaust gas introduction passage 31 is formed such that its diameter increases as it approaches the exhaust port (downward in FIG. 1), that is, the diameter decreases as it goes along the outer periphery of the turbine 1. It is configured to increase the flow velocity of the inflowing exhaust gas. Then, the exhaust gas flowing into the turbine 1 flows out to the exhaust passage 32 after rotating the turbine disk 1a. The shroud cover 33 provided to cover the impeller 2 is open to an intake passage 34 located on the upstream side. On the other hand, the outlet of the air flow passage 2b in which high-pressure compressed air is generated by the rotation of the impeller disk 2a is formed in a diffuser 36 having a channel portion 35 and a shroud cover 33, and is provided in an intake port (hereinafter simply referred to as an intake (Referred to as a port). The channel 35 has a triangular shape whose width increases toward the outer periphery of the diffuser 36, as shown in FIG. 2, which is a cross section taken along line II-II of FIG. This serves to prevent the air from being reduced in pressure as it travels to the outer periphery of the diffuser 36. As shown in FIG. 1, the turbocharger 30
Between the turbine disk 1a and the impeller disk 2a, a heat shield plate 37 for shielding heat between the two is disposed. The heat shield plate 37 corresponds to the above-described heat shield plate, and constitutes a main part of the present embodiment. The heat shield plate 37 is composed of a plate-shaped member 38 disposed on the impeller 2 side and a plate-shaped member 39 disposed on the turbine side.
And a labyrinth 24 and a blade 25 provided at a portion of the turbine disk 1a facing the rotating shaft 5. The blade 25 is provided with a plurality of protrusions so as to form a wavy outer shape, and is a member that realizes a seal between the space on the turbine 1 side and the space on the impeller 2 side in a non-contact manner by the action of the protrusions. . That is, a slight gap is provided between the blade 25 and the rotating shaft 5. Therefore, even when the rotating shaft 5 rotates at a high speed, there is no sliding between the blade 25 and the rotating shaft 5, and it is possible to prevent the two from changing over time. On the other hand, when a pressure difference is generated between the space on the turbine 1 side and the space on the impeller 2 side, the pressure difference is decomposed into a stepwise small pressure difference by a plurality of projections provided on the blade 25, and the pressure loss is reduced. Consumed. For this reason, the space on the turbine 1 side and the space on the impeller 2 side are in a substantially sealed state despite non-contact. A gap 40 corresponding to the above-mentioned gap is formed between the plate-like bodies 38 and 39. Here, the plate-like body 38 is provided integrally with the diffuser 36 having the channel or the vane (hereinafter, simply referred to as a channel) 35 as described above, and the channel 35
As shown in FIGS. 1 and 2, a cooling fluid inflow passage 41 and a cooling fluid discharge passage 42 communicating with the gap 40 are provided in the air passage 40. FIG. 3 is an enlarged view of a section taken along line III-III in FIG. 2, and FIG. 4 is an enlarged view of a section taken along line IV-IV in FIG.
The peripheral configuration of the cooling fluid inflow passage 41 and the peripheral configuration of the cooling fluid discharge passage 42 will be described in detail with reference to FIG. As shown in FIG. 3, the cooling fluid inflow passage 41
Has one end open to the cavity 40 and the other end open to the base of the shroud cover 33 in the intake passage 34 via a filter 44 provided in the housing 43. The space at the base of the shroud cover 33 is a space upstream of the impeller 2 and a space in which the internal pressure relatively close to the atmospheric pressure is maintained during the operation of the impeller 2, and corresponds to the above-described first space. The filter 44 is provided with the cooling fluid suction passage 4.
1 is provided to prevent clogging due to inhalation of foreign matter into the inside 1 or chipping of the impeller blades. On the other hand, as shown in FIG. 4, the cooling fluid discharge passage 42 has one end opened to the cavity 40 and the other end formed with a ventilation passage 45 provided between the housing 43 and the shroud cover 33. The shroud cover 33 has an opening in the shroud cover 33 immediately upstream of the impeller disk 2a. The space in which the ventilation passage 45 is opened is a space upstream of the impeller 2 and a space in which a negative intake air pressure is generated when the impeller 2 operates. In other words, the space has a lower pressure than the space at the base of the shroud cover 33 in which the atmospheric pressure is substantially maintained even when the impeller is operated. In this sense, the space in the shroud cover 33 corresponds to the above-described second space. According to this configuration, when the impeller 2 operates and a negative pressure is generated in the shroud cover 33 and immediately upstream of the impeller disk, the negative pressure is guided to the cooling fluid discharge passage 42 through the ventilation passage 45, The air is guided to the cooling fluid inflow passage 41 through the gap 40. Then, the air in the intake passage 34 is sucked from the cooling fluid inflow passage 41, flows through the gap 40, and is discharged into the shroud cover 33. Here, the cooling fluid inflow passage 41 and the cooling fluid discharge passage 42 are substantially 180 ° as shown in FIG.
° is provided for the channel 35 out of phase. Therefore, when air flows into the cooling fluid inflow passage 41 and flows toward the cooling fluid discharge passage 42, the gap 40 provided in a donut shape in the heat shield plate 37 has
A flow velocity will be generated in the entire area. Therefore, during the operation of the impeller 2, that is, the operation of the turbocharger 30, the heat shield plate 3
The relatively low-temperature air in the intake passage 34 is introduced into the entire area of the inside 7, and the gap 40 effectively functions as a heat insulating layer, and appropriately shields radiant heat radiated from the turbine 1 toward the impeller 2. It is possible to heat. Meanwhile, in an internal combustion engine or the like in which supercharging is performed by a turbocharger, at a low load where supercharging by the turbocharger is not so required, a portion where the air flow in the intake passage relatively easily stagnates (for example, in this embodiment, (The vicinity of the base of the shroud cover 33 where the cooling fluid inflow passage 41 opens) in some cases. If the amount of air to be introduced into the shroud cover 33 is small and the flow velocity does not occur near the base of the shroud cover 33, the air stagnant at that location will be
This is because they are exposed to the radiant heat. If the amount of intake air suddenly increases in such a situation, the staying high-temperature air will be sucked into the impeller 2 at a stretch. This causes a reduction in compression efficiency as a charger, generation of a surge, and the like, and also causes contact with a cover or the like due to deformation of the impeller disk 2a and damage. On the other hand, the turbine cooling device of the present embodiment has the shroud cover 3 in the intake passage 34 as described above.
In this configuration, the air for cooling the heat shield plate is sucked from the root of 3. Therefore, depending on the operating state of the turbocharger, a flow velocity is always generated in a portion where the air has stagnated in the past, and the effect that the above-described problem caused by the stagnant high-temperature air can be solved can also be obtained. As described above, in the turbine cooling device of this embodiment, in the turbocharger in which the turbine 1 and the impeller 2 are provided back-to-back and the size is reduced, sufficient heat shielding is achieved without lowering the compression efficiency. It has an excellent effect that the effect can be ensured and the trouble due to the stagnation of high-temperature air can be effectively prevented. In the present embodiment, the first space and the second space are each defined by the shroud cover 33.
, And the inside of the shroud cover 33, but is not limited to this, and may be any two spaces where a differential pressure is generated when the impeller is operated. As described above, according to the present invention, the heat shield plate disposed between the turbine and the impeller is cooled by the low-temperature air taken in from the upstream of the impeller. The heat shielding plate can be effectively cooled without lowering the compression efficiency as described above, and a high heat shielding effect can be obtained. For this reason, the turbine heat shield device according to the present invention has a feature that a supercharger having a high compression efficiency and a small size can be realized as compared with the conventional supercharger. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a turbocharger incorporating a turbine heat shield device according to one embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a configuration of a turbine heat shield device of the present embodiment. FIG. 3 is an enlarged view (part 1) illustrating a configuration of a main part of the turbine heat shield device of the present embodiment. FIG. 4 is an enlarged view (part 2) illustrating a main configuration of the turbine heat shield device of the present embodiment. FIG. 5 is an overall configuration diagram of a turbocharger incorporating a conventional turbine heat shield device. DESCRIPTION OF SYMBOLS 1 Turbine 1a Turbine disk 2 Impeller 2a Impeller disk 3, 4 Bearing 30 Turbocharger 33 Shroud cover 34 Intake passage 37 Heat shield plate 38, 39 Plate 40 Air gap 41 Cooling fluid inflow passage 42 Cooling fluid discharge Passage 45 Ventilation passage

Claims (1)

(57) [Claim 1] In a supercharger provided with a back-to-back turbine that rotates at a flow rate of a high-temperature fluid and an impeller that rotates by using the turbine as a drive source and pumps a low-pressure fluid, A turbine heat shield device that shields heat between a space on the turbine side and a space on the impeller side, the heat shield plate being disposed between the turbine and the impeller, having a gap inside, and the impeller Space on the upstream side of
A cooling fluid inflow passage communicating between a first space near the base of the shroud cover to be covered and a gap of the heat shield plate; and a space upstream of the impeller, wherein the first space is provided during rotation of the impeller. A turbine heat shield device, comprising: a cooling fluid discharge passage that communicates a second space having a lower pressure with a gap of the heat shield plate.