VARIABLE GEOMETRY RADIAL TURBINE

Abstract: The inlet area and the inlet flow angle of a radial turbine for a turbocharger can be controlled and adapted to a continuously changing gas flow rate by a plurality of movable vanes in the volute inlet.

Description: BACKGROUND OF THE INVENTION: Field of the Invention This invention relates to various types of variable geometry type radial turbine for a turbocharger and so forth in which an inletting cross sectional area thereof can be changed. Description of the Prior Art: The conventional type of the variable geometry turbine for a turbocharger will now be described with reference to Figs. 12 and 13. A turbine wheel 320 is disposed in a housing 321 which forms an exhaust gas passage 327 which accelerates the exhaust gas which has been introduced. A movable vane 323 which is disposed in a portion 326 through which the exhaust gas is introduced into the turbine wheel 320 is opened and closed, whereby the turbine geometry is varied. In this case, as shown in Fig. 13, the passage throat area becomes A₁ when the movable vane 323 is closed, while the passage throat area becomes A₂ when the movable vane 323 is opened. As mentioned above, the throat area of the passage is changed, and this change causes the accelerating ratio to be changed, whereby the turbine geometry is changed. Another type of the conventional variable geometry turbine is shown in Figs. 14 and 15. In the inlet port movable type radial turbine, shown in Figs. 14 and 15, the gas introduced through an inlet port of a scroll passage 400 flows a movable passage 430 which is formed by a flap vane 420 and an inner wall 401 of the scroll passage, and the gas is then introduced into a moving blade 440 through the inner side of a rear scroll passage 402. A rotary shaft 422 which is disposed in the front edge portion 421 of the flap vane 420 projects outside through a penetrating hole 403 in the wall adjacent to the scroll passage 400. The flap vane 420 is therefore capable of being rotated relative to the rotary shaft 422 as illustrated by the short dash line by turning a lever 423 provided with a handle of the rotary shaft 422. By rotating the flap vane 420 relative to the rotary shaft 422, the distance between the inner wall 401 and a rear end 424 of the flap vane 420 is changed, whereby the area of the movable passage 430 is changed for the purpose of changing the flowing characteristics of the turbine. In the conventional type variable geometry turbine having a moving vane, shown in Figs. 12 and 13, the amount of the exhaust gas at the time of the vane being opened and which is allowed to be introduced into the turbine wheel, and the range of amount of the gas being between the throat area A₂ and the throat area A₁, is defined in accordance with the length of the movable vane 323. Therefore, the variable range of the geometry of the turbine can be made large by lengthening the movable vane 323, but operation of the long movable vane in the atmosphere of high temperature and an exhaust gas causes the durability to deteriorate. If the movable vane is lengthened, the movable angle at the time of opening and closing the vane is not changed, therefore the distance of shifting the tip of the movable vane become large in accordance with the length of the movable vane. The turbine performance sometimes deteriorates because the vane transverses the exhaust gas flow when the movable vane is opened. The conventional type of the inlet port movable radial turbine shown in Figs. 14 and 15 is a type in which the flap vane 420 is rotated relative to the rotary shaft 422 which is disposed at the front end portion 421 of the flap vane 420 for the purpose of changing the area of the movable passage 430 which is formed by the rear end 424 of the flap vane 420 and the inner wall 410 of the scroll passage. Therefore when the turbine flow rate is intended to reduce, the rear end 424 of the flap vane 420 must be brought to near the inner wall 401 of the scroll passage. As a result of this, a dead water region is generated in the rear stream of the flap vane 420, whereby the efficiency of the turbine rapidly deteriorates. In the case where the flow rate of the turbine is intended to increase in the conventional type of the inlet port movable type radial turbine, the rear end 424 of the flap vane 420 must be brought to the position far from the inner wall 401 of the scroll passage so as to expand the movable passage 430. In this case, a certain distance must be kept between the rear end 424 and the movable blade 440 for the purpose of preventing interference. If the area of the movable passage 430 is intended to increase for the purpose of increase the maximum flow rate of the turbine, the inner wall 401 of the scroll passage must therefore be brought to the outside position. In this case, when the flow rate is intended to reduce, the rotational angle ϑ of the flap vane 420 must further increase, whereby the dead water region which is generated at the rear stream of the flap vane 420 becomes large, as a result of which, the efficiency deteriorates. SUMMARY OF THE INVENTION: An object of the present invention is to provide a variable geometry type radial turbine which can overcome the aforesaid problems and which is characterized in that the turbine geometry can be continuously varied in a wide range without any deterioration in the turbine performance and furthermore characterized in that the dead water region which is generated at the rear stream of the movable blade is kept least, whereby the turbine efficiency is improved. In order to overcome the aforesaid problems, a plurality of movable vane is provided in the portion through which exhaust gas is introduced into the turbine wheel which is disposed in the turbine housing for the purpose of moving and opening and closing a part of the exhaust gas introducing portion whereby the flow rate of the exhaust gas can be continuously changed. In the variable geometry turbine according to the present invention, a blade-formed rotatable vane is divided into two piece, that is, a front blade and a rear blade. The front blade with a supporting shaft disposed at the rear end portion of the blade is disposed in the upper stream, while the rear blade with a supporting shaft disposed at the front end portion of the blade is disposed in the rear stream. Furthermore, in the radial turbine having a scroll passage, a first movable blade having a rotational shaft thereof disposed adjacent to the rear end with respect to the center of the blade is provided in the portion adjacent to the inner circumference near the entrance of the aforesaid scroll passage, and a second movable blade having a rotational shaft thereof disposed adjacent to the front end with respect to the center of the blade is provided in the rear stream side of the first movable blade in the portion adjacent to the outer circumference of the aforesaid scroll passage. According to the present invention, the variable range of the area of the throat can be made large and the variable range of displacement of the turbine can be made large thanks to the provision of a plurality of the movable vanes. According to another aspect of the present invention, thanks to the provision of the vane having a supporting axis which is disposed adjacent to the rear end portion in the upper stream, the increase in flow rate can be easily realized because the passage having an opening facing inside which has been closed by the vane is opened by turning the vane. In the case where the flow rate is intended to be reduced, the vane with the supporting axis disposed at the front end portion and which is provided in the lower stream is caused to be turned. Since the length of the vane is short, the dead water region which is generated in the rear stream of the vane can be kept small, whereby the deterioration in efficiency can be also kept small. Furthe rmore, according to still another aspect of the present invention, since the first movable blade is disposed in the upper stream of the scroll passage and in the portion adjacent to the inner circumference of the passage, if the flow rate is intended to increase, the inner facing passage which is closed by the blade is opened by way of turning this first movable blade. On the other hand, if the flow rate is intended to decrease, the passage is made narrow by turning the second movable blade which is disposed in the rear stream with respect to the first movable blade and adjacent to the outer circumference of the scroll passage. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a lateral cross sectional view of a first embodiment of the present invention; Fig. 2 is a vertical cross sectional view of the same; Fig. 3a is a vertical cross sectional view of the angle ϑ of the exhaust gas passage according to the same; Fig. 3b is a graph showing the distribution of the area of the exhaust gas passage; Fig. 4 is a cross sectional view of a second embodiment of the present invention; Fig. 5 is a cross sectional view taken along the line V-V in Fig. 4; Fig. 6 is a cross sectional view taken along the line VI-VI in Fig. 4; Fig. 7 is a graph showing the relationship between the turbine flow rate and the turbine efficiency of the aforesaid second embodiment and that of the conventional prior art; Fig. 8 is a cross sectional view of a third embodiment of the present invention; Fig. 9 is a cross sectional view taken along the line IX-IX in Fig. 8; Fig. 10 is a cross sectional view taken along the line X-X in Fig. 8; Fig. 11 is a graph showing relationship between the turbine flow rate and the turbine efficiency of the aforesaid third embodiment and that of the conventional prior art; Fig. 12 is a lateral cross sectional view of the conventional example; Fig. 13 is a vertical cross sectional view of the same; Fig. 14 is a lateral cross sectional view of another conventional example; and Fig. 15 is a vertical cross sectional view of the same. PREFERRED EMBODIMENTS OF THE INVENTION: Referring to accompanying drawings Figs. 1 and 2, a first embodiment of the present invention will now be described. Movable vanes 22 and 23 are provided in a portion 26 through which exhaust gas is introduced into a turbine wheel 20 in a turbine housing 21 and these vanes are supported by means of a bush 24. The movable vanes 22 and 23 are adapted to be capable of moving relative to a movable axis 25 which is disposed in the lower stream of gas. If the turbine capacity is small in this case, the surfaces of both the movable vanes 22 and 23 are brought into contact with a part of the portion 26 through which exhaust gas is introduced into the turbine housing 21, whereby the introduction of the exhaust gas into the turbine wheel 20 through the wall surface is prevented. As a result of this, the throat area in the exhaust gas passage 27 in the turbine housing 21, as shown in Fig. 2, become A₁. In the case where the turbine capacity is large, both the movable vanes 22 and 23 move, whereby openings are formed by the movements of the vanes 22 and 23 from the contact part of the portion 26 and through said openings the exhaust gas is introduced into the turbine wheel 20. The throat area in this case is shown by A₃ in Fig. 2. In the case where the turbine capacity is between the aforesaid small case and the large case, only the movable vane 22 moves and shifts from the surface in which it is in contact with the portion 26 whereby an opening through which the exhaust gas is introduced is formed. The throat area in this case is shown by A₂ in Fig. 2. Fig. 3b is a graph showing the relationship betwee n the passage area and exhaust gas passage angle ϑ around the central axis of the turbine wheel which is shown in Fig. 3a in accordance with the turbine capacity, large, intermediate and small. Namely, when the turbine capacity is small, the exhaust gas passage area decreases from A₁ to B₁ as the angle ϑ increases as designated by the arrow in Fig. 3a. In the similar manner, in the case where the turbine capacity is in the intermediate range, the exhaust gas passage area decreases from A₂ to B₂, and in the case where the turbine capacity is large, it decreases from A₃ to B₃ in accordance with the respective increase in the angle ϑ. The exhaust gas passage areas B₁, B₂ and B₃ are shown in Fig. 2. Aforesaid embodiments are those in the case where the movable vanes 22 and 23 are controlled in a step manner in accordance with the turbine capacity, small, intermediate and large. The degree of opening of the movable vanes 22 and 23 may be defined optionally. The degree of opening of the movable vane 22 and 23 may therefore be defined optionally and combined at the time of controlling for the purpose of obtaining the maximum efficiency at a predetermined flow characteristics. Although the aforementioned embodiments and drawings show the case wherein two rotational vanes are provided, provision of it more than three can display same effect. A second embodiment of the present invention will now be described with reference to the accompanying drawings Fig. 4 (cross sectional view of a casing), Fig. 5 (cross sectional view taken along the line V-V in Fig. 4), Fig. 6 (cross sectional view taken along the line VI-VI in Fig. 5) which show the structure. The comparison of the effect between the present invention and the prior art is shown in Fig. 7. The gas flow introduced into the scroll 101 is then divided into an outer circumferential passage 105 which is formed by a front end 111 of the front blade 110 having a supporting axis 113 in the rear end portion 112 of the front blade and a scroll inner wall 102 and an inner circumferential passage 108 which is formed by the front end 111 of the front blade and a tonque formed area 107 of the scroll. The gas which has passed the outer circumferential passage 105 is then introduced into the scroll passage 103 through the rear variable passage 104 which is formed by a rear end 122 of a rear blade 120 having a supporting axis 123 in the front end portion 121 of the rear blade and the scroll inner wall 102. The flow is then introduced into the moving blade 130 through the inner portion of the scroll 101. The gas which has passed the inner circumferential passage 108 is then introduced into a moving blade 130 through the passage which is formed by the inner side wall of the front blade 110 and the scroll inner wall 102. By turning the front blade 110 relative to the supporting axis 113, the inner passage 108 is expanded, whereby the flow rate of the turbine increases. This time, although the area of the outer circumferential passage 105 becomes small, the distance between the front blade 110 and the scroll inner wall 102 is long enough to prevent the interference of the gas flowing into the outer circumferential passage 105. If the flow rate is intended to become small, the front blade 110 is brought into the position near the scroll toungue formed portion 107, and the rear end 122 of the rear blade 120 is brought into the position near the scroll inner wall 102. Fig. 7 illustrates the relationship between the turbine flow rate and the turbine efficiency of the device according to the present invention and the conventional device shown in Figs. 14 and 15. As can be clearly seen from this drawing, the turbine efficiency is remarkably improved. A third embodiment of an inlet port variable type radial turbine according to the present invention will now be de scribed. Fig. 8 is a cross sectional view illustrating it from which the moving blade is omitted. Fig. 9 is a partial cross sectional view taken along the line IX-IX in Fig. 8. Fig. 10 is a partial cross sectional view taken along the line X-X in Fig. 8. Fig. 11 is a graph showing the turbine efficiency in comparison with that of the conventional type turbine. This radial turbine forms a turbocharger with a compressor. It comprises, as shown in Figs. 8 to 10, a moving blade 240 on inside thereof and a scroll passage 200 which supplies a gas to this moving blade 240. In the area adjacent to the inner circumference near the entrance of the scroll passage 200, a first movable blade 250 is provided. In the area adjacent to the outer circumference of the scroll passage in the rear stream of this first movable blade 250, a second movable blade 290 is provided. The first movable blade 250 has a rotational shaft 252 in the portion 251 adjacent to the rear end (rear end portion) with respect to the blade center. The second movable blade 290 has a rotational shaft 292 in the portion 291 adjacent to the front end (front end portion) with respect to the center of the blade. The rotational shaft 252 penetrates into the hole 254 which is formed in the turbine casing. A lever 255 is secured to the end portion of the rotational shaft 252. The first movable blade 250 can be therefore rotated relative to the rotational shaft 252 by rotating the lever 255. Such rotation of the first movable blade 250 causes the outer circumferential passage 260 to be formed by the first movable blade 250 and the scroll passage inner wall 210 and the inner circumferential passage 280 to be formed by this first movable blade 250 and the scroll tongue-formed portion 270. The rotational shaft 292 penetrates into a hole 294 which is formed in a turbine casing. A lever 295 is secured to the end portion of the rotational shaft 292. Therefore, by turning this lever 295, the second movable blade 290 can therefore be rotated relative to the rotational shaft 292. The rotation of the second movable blade 290 causes the state of the rear variable passage 220 which is formed by the second movable blade 290 and the scroll passage inner wall 210 to be changed. In Fig. 8, reference numeral 253 represents a front end portion of the first movable blade 250, reference numeral 293 represents a rear end portion of the second movable blade 290, and reference numeral 230 represents a rear scroll passage. As mentioned above, in the case where the flow rate is intended to increase, first the rotational shaft 252 is rotated counterclockwise in Fig. 8. The gas (fluid) which has been introduced into the scroll passage 200 is divided into the outer circumferential passage 260 which is formed by the front end portion 253 of the first movable blade 250 and the scroll passage inner wall 210 and the inner circumferential passage 280 which is formed by the first movable blade 250 and the scroll passage tongue-formed portion 270. The fluid which has passed the outer circumferential passage 260 passes a rear variable passage 220 which is formed by the second movable blade 290 which is disposed in the rear stream and the scroll passage inner wall 210 and then introduced into a rear scroll passage 230 and introduced into the moving blade 240 through the opening in the inside of the scroll passage 200. The fluid which has passed the inner circumferential passage 280 passes the passage which is formed by the first movable blade blade 250 and the scroll passage inner wall 210 and then introduced into the moving blade 240. By further counterclockwise rotation of the first movable blade 250 relative to the rotational shaft 252, the inner circumferential passage 280 is expanded, whereby the turbine flow rate increases without any generation of the dead water region in the rear stream side of the blade. In the case where t he flow rate is intended to reduce, the passage continued to the moving blade 240 must be made narrow by rotation of the second movable blade 290 by means of the lever 295. Since the length of the movable blade is shorter with respect to the conventional type shown in Figs. 14 and 15, the dead water region in the rear stream is small, furthermore it can gather the fluid into the inside portion of the passage, whereby the deterioration in efficiency can be kept small. Since the flow from the movable blade to the scroll passage 200 in the rear stream does not exceed the rate when the movable passage area in the rear stream is the maximum, the scroll passage can be designed in accordance with the case in which the variable passage area in the rear stream is maximum. Furthermore, since the rotational shaft 292 of the second movable blade 290 is disposed in the outer circumferential portion, the deterioration in turbine efficiency at the time of the flow rate is intended to make small can be kept small with respect to the conventional prior art. On the other hand, in case where the flow rate is intended to increase, the deterioration in the turbine efficiency can be kept small because the inner circumferential passage 280 is opened, whereby high turbine efficiency can be obtained in the wide flow rate range. Fig. 11 is a graph showing the relationship between the turbine flow rate and the turbine efficiency with comparison with the conventional type turbine. In Fig. 11, symbol A represents the characteristics of an inlet port variable type radial turbine according to this embodiment. Symbol a represents the characteristics of the conventional inlet port variable type radial turbine shown in Figs. 14 and 15. The provision of two or more first movable blades 250 and the second movable blades 290 may be employed in this embodiment. As described above, the present invention can display the following effects. (1) Thanks to provision of a plurality of movable vanes, the turbine capacity can be changed in a wide range. (2) Thanks to the provision of a plurality of movable vanes and resulted alignment of the direction in which the flow direction of the exhaust gas and that of the movable vane at the time of movable vane being opened, whereby high turbine efficiency can be achieved. Further, according to the present invention, since the flow rate, exceeding the rate when the outside variable passage area is maximum, does not pass from the movable vane to the scroll in the rear stream, the scroll outside variable passage can be designed in accordance with the maximum area of the variable passage, whereby the deterioration in efficiency can be kept small in comparison to the conventional prior art when the flow rate is intended to make small (the case where the outside variable passage area is made narrow), whereby the high efficiency can be obtained in a wide range. Also according to the present invention, in spite of the simple structure, the turbine efficiency can be improved by keeping the dead water region which is generated in the rear stream of the movable blade as small as possible.

Claims: 1. A variable geometry radial turbine having a plurality of movable vanes which are disposed in the portion through which an operating gas is introduced into a turbine wheel in a turbine housing, whereby the operating gas introducing portion is opened and closed by moving said vane for the purpose of continuously changing the flow rate of the operation gas. 2. A variable geometry radial turbine according to claim 1 wherein the center of movement of said vane is disposed at the position in the lower stream of the gas. 3. A variable geometry radial turbine having a scroll passage characterized in that the front end portion of a wall adjacent to a turbine moving blade which is disposed in said scroll passage is formed by a vane in the form of a blade which is capable of rotating relative to a shaft which is disposed in the manner transversing said wall, and said blade type vane is divided into two parts, a front blade and rear blade, and said front blade having a shaft which is positioned at the rear end portion of the blade is disposed in the upper stream, and said rear blade of which shaft is positioned at the front end portion of said blade is disposed in the lower stream. 4. A variable geometry radial turbine having a scroll passage characterized in that a first movable blade with a rotational shaft disposed in a portion adjacent to the rear end portion with respect to a center of a blade is provided in the inside portion near an entrance of said scroll passage, and a second movable blade with a rotational shaft disposed in the portion adjacent to the front end with respect to a center of said blade is provided in the outside portion in said scroll passage in the lower stream side of the said first movable blade. 5. A variable geometry radial turbine according to claim 1 wherein each vane is a cantilever type vane which is rotatably secured to a shaft. 6. A variable geometry radial turbine according to claim 3 wherein an area of the scroll passage adjacent to inside is adjusted by means of a vane in the upper stream and an area of the scroll passage adjacent to outside is adjusted by means of a vane in the lower stream.

Inventors: KYOYA, MICHIO SAGAMIHARA MACHINERY WORKS, MATSUDAIRA, NOBUYASU SAGAMIHARA MACHINERY WORKS, MATSUO, EITO NAGASAKI TECHN. INSTITUTE, MIKOGAMI, TAKASHI SAGAMIHARA MACHINERY WORKS, OKAZAKI, YOICHIRO SAGAMIHARA MACHINERY WORKS, TAKAHIRA, NOBUHIRO NAGASAKI TECHN. INSTITUTE
Applicants: MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1987
Main classification: F01D17
IPC codes: F01D17, F02B37