GB2105789A

GB2105789A - Variable geometry turbine

Info

Publication number: GB2105789A
Application number: GB08124771A
Authority: GB
Inventors: Neil Watson
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-08-13
Filing date: 1981-08-13
Publication date: 1983-03-30
Also published as: GB2105789B

Abstract

In a radial inward flow turbine having one or more volute passages 14, an arcuate segment 17 may be bodily shiftable out of and into an opening 20 formed in a side wall of the flow channel 16, with the result that the arcuate segment 17 respectively forms a comparatively greater or lesser part of the inner wall of the or each of the passages 14, the arcuate segment 17 being movable under the control of an actuating member 18 which may be reciprocable on an axis extending substantially parallel to the axis of the rotor 11. Withdrawal of the arcuate segment 17 into the opening 20 may open a gas flow passage through casing 10 bypassing the rotor 11, and in another arrangement the actuating member 18 is pivotable on an axis parallel to the rotor axis. <IMAGE>

Description

SPECIFICATION Variable geometry turbines The present invention relates to variable geometry turbines of the kind, hereinafter referred to as the kind specified, comprising a radial inward flow bladed rotor mounted within a casing, the casing including one or more volute passages which decrease in cross-sectional area with increasing distance from respective inlets thereto, and the casing also including a peripheral supply channel which surrounds the rotor and communicates, along its length, with the rotor as well as the or each of thepassages.

A common application of such a turbine is as a turbo supercharger for an internal combustion engine - exhaust gas from the engine drives the turbine which in turn drives a compressor for supplying air under pressure to the engine.

One of the problems associated with this kind of turbine, however, especially when used as a turbo supercharger for an engine, is ensuring that the turbine matches the engine.

At high engine speeds the quantity of exhaust gas is relatively large so that if the turbine is designed to operate with a high flow of exhaust gas then at lower engine speeds resulting in a much lower flow of exhaust gas, the amount of air delivered by the compressor will be insufficient. Conversely if the turbine is designed to drive the compressor at the correct speed with a low flow of exhaust gases then at high engine speeds when the amount of exhaust gas is relatively high, the amount of air delivered by the compresorwill be too great.

Exactiy this problem has been tackled by British Patent No. 1 440 313, which discloses the provision of an elongated baffle strip which is supported by groove means in the casing and follows the outer wall of the passage, the strip overlapping itself over a portion of its length so that it forms both the inner and outer walls of the passage over a portion of the length of the passage, the strip being movable along its length so that the extent of overlap can be altered, whereby the effective area of a throat defined between the overlapping portions of the baffle strip can be adjusted.

Although that arrangement is capable, in the application mentioned hereinabove, of driving the compressor at a higher speed when the exhaust gas flow is low, it nonetheless suffers from the important practical disadvantage that the elongated baffle strip tends to buckle as it is bodily pushed, in the direction of its length, along the groove means in order to reduce the effective area of the throat.

In accordance with the present invention, however, a variable geometry turbine of the kind specified comprises an arcuate segment movable between operative an inoperative positions, in which the arcuate segment respectively does and does not form at least a part of the inner wall of the or each of the passages, the arcuate segment being movable under the control of an actuating member reciprocable or pivotable on an axis extending substantially parallel to the axis of the rotor.

In particularly preferred embodiments of the present invention, the entire arcuate segment is bodily shiftable into and out of an opening of generally complementary shape formed in the casing, and such withdrawal can open a gas flow passage through the casing by-passing the rotor.

Three variable geometry turbines, in accordance with the present invention, will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure lisa simplified sectional end view of a first turbine; Figure 2 is a less simplified sectional side view taken along the line X-X of Figure 1; and Figures 3 and 4 are views similar to Figures 1 and 2, respectiely, of second and third turbines.

Avariable geometry turbine is shown, in Figures 1 and 2, having a generally annular casing 10 within which is located a rotor 11 having blades 12. The rotor is of the radial inflow type and the casing defines an axially extending outlet 13. Formed within the casing are a pair of volute passages 14which extend from an inlet flange 15 around the rotor, the passages having a reducing cross-sectional area as their distance from the inlet flange increases. The passages are side-by-side and connect to a common aperture 16 extending about the periphery of the rotor 11. The axial width of the aperture 16 is substantially equal throughout its length. A pair of exhaust pipes (not shown) lead from individual banks or groups of engine cylinders to the passages 14 at the inlet flange 15.

Mounted within the casing 10 is an arcuate segment 17that can be moved to block part of the aperture 16, from the point at which the passages 14 and the aperture 16 connect nearest to the inlet flange 15, the radius of the arcuate segment 17 reducing as the distance from this point increases.

For effecting movement of the arcuate segment 17 there is provided an actuating member 18 extending parallel to the axis of rotation of the rotor. In an operative position of the actuating member 18, the arcuate segment 17 lies against a side wall 19 of the aperture 16, as shown at A in Figure 2. In an inoperative position of the actuating member 18, the arcuate segment 17 is withdrawn into a housing 20 formed in the opposite side wall of the aperture 16, as shown at B in Figure 2. Referring now to Figure 1, when the arcuate segment 17 is in postion Athe throat through which all gases must flow is formed at position C. When the arcuate segment 17 is in position B the throat will occur at position D where the cross-sectional area of the passages is greater than at position C.

At low engine speed the segment is moved to position Aforming the throat of reduced crosssectional area at position C. Conversely at high engine speed the segment is moved to position B forming the throat of larger cross-sectional area at position D.

The arcuate segment 17 can be moved to intermediate positions at an intermediate engine speed or be used only as a two-position device. In other similar arrangements, the arcuate segment 17 can be slanted, so that, as the arcuate segment 17 is progressively pushed out of its housing 20 by the actuating member 18, a progressively greater length of the peripheral supply aperture 16 is blocked off, with the leading (free) edge of the arcuate segment 17 entering a complementary housing formed in the side wall 19. There may be a single arcuate segment 17, preferably extending through an arc of from 60 to 360" when in its full blocking position, or there may be a series of arcuate segments 17 underthe control of respective actuating members 18.

Further alternatives are shown in Figures 3 and 4.

In Figure 3, arcuate segment 17a is shown pivotably mounted about an axis P located parallel to but eccentrically of axis Q of the rotor, but this limits the extent of the blocking to a little over 90". In Figure 4, arcuate segment 17b is capable of being withdrawn to such an extent that a gas by-pass 30 is opened. By allowing some of the gas to by-pass the rotor at high engine speed, turbine torque is reduced even further. This could be useful in passenger car applications where the change in mass flow rate is high compared even to a truck diesel.

CLAIMS (Filed on 11 Aug 1982) 1. A variable geometry turbine comprising a radial inward flow bladed rotor mounted within a casing, the casing including one or more volute passages which decrease in cross-sectional area with increasing distance from respective inlets thereto, and the casing also including a peripheral supply channel which surrounds the rotor and communicates, along its length, with the rotor as well as the or each of the passages, with an arcuate segment being movable between operative and inoperative positions, in which the arcuate segment respectively forms a comparatively greater or lesser part of the inner wall of the or each of the passages, the arcuate segment being movable under the control of an actuating member reciprocable or pivotable on an axis extending substantially parallel to the axis of the rotor.

2. A variable geometry turbine according to claim 1, in which the arcuate segment is bodily shiftable into and out of an opening of generally complementary shape formed in the casing.

3. A variable geometry turbine according to claim 2, in which the actuating member is reciprocable and the opening is formed in a side wall of the peripheral supply channel.

4. A variable geometry turbine according to claim 3, in which withdrawal of the arcuate segment into the opening opens a gas flow passage through the casing by-passing the rotor.

5. A variable geometry turbine substantially as hereinbefore described with reference to Figures 1 and 2, or Figure 3, or Figure 4, of the accompanying drawings.

6. A variable geometry turbine according to any preceding claim when forming a turbo supercharger for an internal combustion engine.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. progressively pushed out of its housing 20 by the actuating member 18, a progressively greater length of the peripheral supply aperture 16 is blocked off, with the leading (free) edge of the arcuate segment 17 entering a complementary housing formed in the side wall 19. There may be a single arcuate segment 17, preferably extending through an arc of from 60 to 360" when in its full blocking position, or there may be a series of arcuate segments 17 underthe control of respective actuating members 18. Further alternatives are shown in Figures 3 and 4. In Figure 3, arcuate segment 17a is shown pivotably mounted about an axis P located parallel to but eccentrically of axis Q of the rotor, but this limits the extent of the blocking to a little over 90". In Figure 4, arcuate segment 17b is capable of being withdrawn to such an extent that a gas by-pass 30 is opened. By allowing some of the gas to by-pass the rotor at high engine speed, turbine torque is reduced even further. This could be useful in passenger car applications where the change in mass flow rate is high compared even to a truck diesel. CLAIMS (Filed on 11 Aug 1982)

1. A variable geometry turbine comprising a radial inward flow bladed rotor mounted within a casing, the casing including one or more volute passages which decrease in cross-sectional area with increasing distance from respective inlets thereto, and the casing also including a peripheral supply channel which surrounds the rotor and communicates, along its length, with the rotor as well as the or each of the passages, with an arcuate segment being movable between operative and inoperative positions, in which the arcuate segment respectively forms a comparatively greater or lesser part of the inner wall of the or each of the passages, the arcuate segment being movable under the control of an actuating member reciprocable or pivotable on an axis extending substantially parallel to the axis of the rotor.