WO1982000686A1

WO1982000686A1 - Turbine with variable restriction in turbine inlet

Info

Publication number: WO1982000686A1
Application number: PCT/SE1981/000197
Authority: WO
Inventors: Scania Ab Saab
Original assignee: Johansson A
Priority date: 1980-08-14
Filing date: 1981-06-30
Publication date: 1982-03-04
Also published as: GB2094409A; GB2094409B; SE8005747L

Abstract

A turbine, preferably an exhaust-driven turbine forming part of the supercharger of an internal combustion engine, provided with a mechanism (10) for variable restriction in a peripheral inflow duct (3) leading to a turbine rotor (4) rotatably located in turbine casing (2). The invention is intended to prevent, when throttling the turbine inflow, disturbances of the incoming flow leading to energy loss and to prevent or at least reduce the development of mechanical and thermal stresses in the device controlling the throttling action. In this respect the turbine in accordance with the invention is characterised in that the restriction can be adjusted by radial displacement of an outer wall section in turbine casing (2) forming a boundary of inflow duct (3), in that the said wall section comprises a number of wall elements (16, 17, 18) connected with one another in an articulated manner, with at least two of them supported in an articulated and/or displaceable manner in respect of turbine casing (2), and in that the wall section is at its respective ends arranged to connect, subject to a substantially unchanged inflow duct with fixed wall sections in turbine casing (2), so as to form with the latter a helical inlet leading to turbine rotor (4).

Description

Turbine with variable restriction in turbine inlet

The present invention relates to a turbine, preferably an exhaust- driven turbine forming part of the supercharger of an internal combustion engine provided with a mechanism for variable restriction in a peripheral inflow duct leading to a turbine rotor rotatably located within the turbine casing.

With a view to safeguarding the energy content in the exhaust flow of an internal combustion engine it is already known to connect to the engine a supercharger comprising a turbine designed for variable adjustment of the turbine inlet. So far a rotatable flap is described in the German specification DOS 2.151.658, the location of which in the turbine casing is close to an inlet throat pertaining to the turbine. The flap has a free end, and in every restricting position the flow area of the inlet duct is enlarged directly after the restriction. As a result, such a free end causes the incoming flow to be disturbed in a manner entailing a loss of energy.

Furthermore, exhaust gas pulsations may lead to mechanical stresses, whereby the said stresses may give rise to vibration problems in respect of the flap which is rotatably supported at one end. In addition the flap and in particular its end part is subject to high thermal stresses owing to difficulties in dissipating heat from the flap. The heat problem is especially noticeable with turbines forming part of petrol engine superchargers since in the application the turbine is driven by exhaust gases which are hotter than the exhaust gases from a diesel engine.

The object of the present invention consists in designing a turbine, preferably an exhaust-driven turbine, which is free from the said disadvantages. The turbine in accordance with the invention is provided with a mechanism to bring about a variable restriction within a peripheral inflow duct leading to a turbine rotor rotatably located in the turbine casing, whereby the invention is in the main characterised in that the restriction can be adjusted by radial displacement of an outer wall section in the turbine casing forming a boundary of the inflow duct, in that the said wall section comprises a number of wall elements connected with one another in an articulated manner, with at least two wall elements being supported, in respect of the turbine casing, in an articulated and/or displaceable manner, and in that the wall section is arranged, at its respective ends, for connection to fixed wall sections in the turbine casing, the area of the flow duct being substantially unchanged and so as to form, in conjunction with the said fixed wall sections, a helical inlet.

Since the design in accordance with the invention comprises a number of co-operating wall elements throttling the flow in lengthwise direction is enabled, as a result of which losses of energy due to abrupt changes in throughput are largely eliminated. This in turn causes also the thermal and mechanical stresses to which the design in accordance with the invention is subject to be reduced by comparison with restricting devices according to known technology. In addition, the fact that the wall elements are connected to fixed inlet surfaces of the turbine casing enables relatively efficient heat transfer to the surrounding turbine casing as well as evenly distributed absorption of external forces.

With an advantageous embodiment of the invention one wall element is rotatably supported in respect of the turbine casing whereas a wall element connected in an articulated manner with the former is displaceably and rotatably arranged in respect of the turbine casing. The said features constitute prerequisites for designing, with only two wall elements, a simple mechanism in accordance with the invention. Preferably however at least one wall element is fixed in an articulated manner within the turbine casing, with at least one wall element being linked in an articulated manner with an arm or similar device rotatably supported within the turbine casing, whereby the said am or similar device is so arranged as to be acted upon by rotary movements for adjusting the wall elements and, accordingly, the restriction of the turbine inlet.

Other features characterising the invention will be found in the subsequent patent claims and in the following description of an embodiment illustrating the invention. The description refers to the attached figures, with Figure 1 showing a cross-section of a turbine in accordance with the invention and

Figure 2 corresponding substantially to a section A-A in figure 1. A specimen turbine in accordance with the figures is intended to form part of a supercharger not shown of an internal combustion engine of petrol engine type. The said turbine consists in the main of a turbine casing 2 and a turbine rotor 4 rotatably supported therein. The turbine has a tangential inlet 1 , with the said inlet 1 passing into a helical inflow duct 3 which is provided in turbine casing 2 and leads to turbine rotor 4. During operation exhaust gases are fed in known manner from the internal combustion engine via inflow duct 3 towards a number of blades (not shown) of turbine rotor 4, whereupon the exhaust gases are conducted radially inward giving off energy at this stage. After energy transmission to turbine rotor 4 the exhaust gases are discharged through an axial outlet 6 (see figure 2). The turbine is provided with a turbine shaft 5. which is so arranged as to drive, during operation of the turbine, a compressor not shown, the latter being in its turn designed to affect the engine charging pressure. At the transition from turbine inlet 1 the radially outer surface of inflow duct 3 consists of a mechanism 10 in accordance with the invention for adjusting the inflow restriction. Mechanism 10 consists substantially of three parts, i.e. a sector-shaped lever 16 and two flaps 17 and 18 respectively located one after the other in the direction of flow and connected with one another in an articulated manner, the said flaps constituting wall elements and jointly forming an outer wall section adjustable in respect of inflow duct 3. The sector-shaped lever 16 is connected in a torsionally rigid manner with a shaft 15 rotatably supported within the turbine casing, and to the sector-shaped shaft \G is secured a journal 19 with flap 17 being rotatably located about the latter. The other end of flap 17 is, as previously stated, connected with flap 18 by a common bearing 20 which constitutes a displaceable pivot for the flaps 17,18. The other end of flap 18 is, via a shaft 21, rotatably supported in respect of turbine casing 2. Mechanism 10 is controlled by an external actuator 11 so as to take up various positions capable of being adjusted in the radial direction. Actuator 11 conveniently consists in an ordinary pressure cell in which a diaphragm and a spring (not shown) act, subject to the influence of a pressure medium such as the prevailing gas pressure in the engine intake system and/or exhaust system, on a control rod 12 imparting to it an axial displacement. Control rod 12 is connected in an articulated manner with a lever 13 secured to shaft 15, the displacement of rod 12 imparting a rotary movement to lever 13, which is transmitted, via shaft 15 supported in turbine casing 2, to the adjusting mechanism 10.

So as to permit alternative settings of mechanism 10 turbine casing 2 is provided with a projection 25. As can be seen in figure 2 projection 25 comprises two substantially plane side walls 26, 27 in which flaps 17,18 are arranged, the said flaps having straight lateral edges. In order to bring about a smooth connection between the flap ends of mechanism 10 and the fixed sections of inlet 1 provided in turbine casing 2, flaps 17,18 are designed with a curvature matching the curvatures of the fixed sections in turbine casing 2. Figure 2 shows the design of end part 28 of flap 18 projecting in the direction of flow.

In addition, the sector-shaped lever 16 is provided with an outer surface 29 covering the transition between the throat-shaped turbine inlet 1 and mechanism 10. The gaps between surfaces capable of dis- placement in respect of one another are minimised by overlapping at the bearings 19, 20. Gaps shown in the figures are enlarged in order to facilitate their illustration.

Projection 25 is provided with a special space beneath mechanism 10, in which exhaust gases collect during operation of the engine thus forming a damping cushion of gas which counteracts flap vibrations and flutter. As a result mechanical stresses to which mechanism 10 is subject are reduced and there is less danger of irritating noise. In order to make them resistant to high exhaust temperatures components forming part of mechanism 10 are advantageously constructed with the aid of a ceramic material. The tolerance requirements in respect of bearings and gaps can be kept low, which facilitates the co-operation of materials having different coefficients of linear expansion.

For easier assembly of mechanism 10 in the turbine, casing 2 is made separable in two halves, preferably in cross-section at right angles to turbine shaft 5. Alternatively it is possible to provide projection 25 with sections capable of being opened thus enabling the said assembly.

In figure 1 the fully drawn lines show mechanism 10 in the position of maximum restriction, in which position the inflow area of the turbine, following the throat-shaped turbine inlet 1, has its lowest value. Thereafter the radial distance between flaps 17,18 and turbine shaft 5 gradually diminishes in the direction of flow, as a result of which the exhaust gas flow towards turbine rotor 4 is controlled in a manner advantageous from the point of view of energy loss. However, it is not excluded that, with a view to enabling rapid acceleration of the turbine, so large a restriction of the inflow area is selected that the said distance of mechanism 10 is subsequently increased.

The dashed lines in figure 1 show mechanism 10 in a position corresponding to maximum flow area. In this case too the radial distance between flaps 17, 18 and turbine shaft 5 is substantially subject to gradual reduction in the direction of flow.

The invention is not limited to the turbine embodiment described but may, within the scope of the following patent claims, be modified so as to bring about different embodiments. It is for instance possibl to make the inner flap 18 displaceable in respect of turbine casing 2, for instance by supporting it in casing 2 direct or via a lever. If one of flaps 17,18 is displaceably and rotatably supported in casing 2 direct, mechanism 10 in accordance with the invention may comprise only two flaps 17,18, with the second flap 17 rotatably supported in respect of casing 2 and connected with the outer actuator 11 in a torsionally rigid manner. The power-transmitting action of the latter on mechanism 10 in accordance with the invention can be brought about by a shaft connected to any wall element and rotatably supported in casing 2 or by applying a force direct to the mechanism in a position between the bearing points and in substance radially in respect of the turbine shaft. Both the maximum and minimum restriction inflow areas can be made adjustable from outside, depending on the end position of mechanism 10. The said end position can be regulated with the aid of staybolts etc., which the wall elements of the mechanism are made to abut.

Claims

C L A I M S

1. A turbine, preferably an exhaust-driven turbine forming part of the supercharger of an internal combustion engine, provided with a mechanism (10) for variable restriction in a peripheral inflow duct (3) leading to a turbine rotor (4) rotatably supported in turbine casing (2), c h a r a c t e r i s e d in that the restriction is adjustable by radial displacement of an outer wall section (16,17,18) in turbine casing (2) forming a boundary of inflow duct (3), in that the said wall section comprises a number of wall elements (16,17,18) connected with one another in an articulated manner, with at least two wall elements supported in an articulated and/or displaceable manner in respect of turbine casing (2), and in that the wall section is so arranged at its respective ends as to connect, subject to a substantially unchanged area of the flow duct, with the fixed wall sections in turbine casing (2) and to form with the latter a helical inlet leading to turbine rotor (4).

2. A turbine in accordance with claim 1, c h a r a c t e r i s e d in that one wall element (18) is rotatably supported in respect of turbine casing (2) whereas another wall element (17) is displaceably and rotatably arranged in respect of turbine casing (2).

3. A turbine in accordance with claim 1, c h a r a c t e r i s e d in that the adjustable wall section in turbine casing (2) consists of three wall elements (16,17,18), i.e. a sector-shaped lever (16) or similar device and two flaps (17,18) arranged one behind the other in the direction of flow.

4. A turbine in accordance with claim 3, c h ar a c t e r i s e d in that one flap (18) is at one end rotatably secured in turbine casing (2) whereas the other flap (17) is rotatably secured to lever (16), the latter being rotatably supported in turbine casing (2) and so designed as to be acted upon by rotary movements for adjusting the turbine inlet restriction.

5. A turbine in accordance with claim 4, c h a r a c t e r i s e d in that the adjusting mechanism (lθ) is so designed that a rotary movement of lever (16) causes radial displac ment of the joint bearing (20) of flaps (17, 18) in respect of turbine casing (4).

6. A turbine in accordance with claim 5, c h a r a c t e r i s e d in that lever (16) is so arranged as to connect with its outer surface (29) with a throat-shaped section in turbine inlet (1) whereas the inner flap (18) is arranged to connect with an inner convex surface of an inlet helix in turbine casing (2) .

7. A turbine in accordance with claim 6, c h a r a c t e r i s e d in that lever (16) is arranged to be acted upon by rotary movements produced by a device (11) located outside turbine casing (2), the said device preferably consisting of an actuator controlled by pressure medium.