GB2100359A

GB2100359A - Variable volume radial turbine

Info

Publication number: GB2100359A
Application number: GB8215303A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1981-06-16
Filing date: 1982-05-26
Publication date: 1982-12-22
Also published as: GB2100359B; DE3219250A1; JPS57206704A; DE3219250C2

Abstract

A shaft (10) having a shaped tip (20) or groove formed thereon is projectable or rotatable to deflect the gases flowing in the scroll (12) and variably direct the gases into the turbine impeller (22) in a manner which induces an effective change in the capacity of the turbine. <IMAGE>

Description

SPECIFICATION Variable volume radial turbine The present invention relates generally to radial turbines and more particularly to a radial turbine equipped with a simple capacity varying device.

For the purpose of promoting both fuel economy and power output, automotive internal combustion engine turbochargers are required to operate over a wide range of engine operating conditions and to produce usable amounts of torque even at low and medium engine speeds. In order to achieve this it is desirable to design the scroll to have a configuration which will direct the exhaust gases from the engine to the turbine impeller of the turbocharger so that at low engine speeds the rotation of the impeller can be increased rapidly while not inducing high exhaust back pressures during high speed engine operation.However, such a compromise cannot in actual practice be produced whereby it has been necessary to utilize a small capacity turbine and by-pass exhaust gases around the turbine upon excessive back pressure prevailing in the exhaust manifold of the engine and/or when the turbine impeller speed increases to the point of producing an excessive supercharging pressure in the induction manifold. However, the use of so called "waste gates" for by-passing the exhaust gases is not desirable from the view point of exhaust gas energy recovery. Thus, it has been proposed to effectively vary the capacity of the turbine by utilizing an arrangement such as illustrated in Figs.

1 and 2 of the drawings and which is disclosed in Japanese Patent Publication Sho 54-84123.

However, while this arrangement has been able to vary the capacity of the turbine it has suffered from a number of drawbacks. Viz., the scroll 1 must be sectioned so as to aliow for the installation of the flow coritrol vane 2 and the surfaces 3 of the scroll on either side of the vane 2 must be precision machined to provide the necessary clearances between the vane and the scroll housing. This of course renders the construction and production of the turbine both more complex and expensive while still not being entirely satisfactory in that, due to the high temperature and pressures which prevail in the scroll 1 during operation of the engine, the vane 2 is apt to distort and either jam, or in the worst case, warp to the degree of contacting the turbine impeller 4 itself.Further, the shaft 5 which is rotatably disposed through the housing to control the movement of the vane 2 is apt to seize due to the very high temperatures, thus preventing the solenoid control arrangement 6 from moving the vane when it is desired to do so.

The present invention features a shaft having a shaped tip or groove which is projectable into or rotatable with respect to the scroll housing of a radial turbine so as to variably direct the gases flowing in said scroll into the turbine impeller in a manner which induces an effective change in the capacity of the turbine.

More specifically the present invention takes the form of a device for varying the capacity of a radial turbine which includes a scroll housing and a turbine impeller located at the downstream end of said scroll, comprising: a shaft movable with respect to said scroll housing and disposed in said scroll housing so as to have a portion located immediately adjacent the downstream end thereof, with a shaped portion on said shaft portion and means for moving said shaft so that said shaped portion selectively deflects the fluid which flows in said scroll housing with respect to said impeller in accordance with a sensed operating parameter.

The features and advantages of the arrangement of the present invention will become more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which: Fig. lisa sectional plan of the prior art arrangement referred to in the opening paragraphs of the present disclosure; Fig. 2 is a sectional elevation taken along the section line Il-Il of Fig. 1; Fig. 3 is a sectional plan showing a first embodiment of the present invention; Fig. 4 is a sectional elevation taken along the section line IV--IV of Fig. 3; Fig. 5 shows possible tip designs of the shaft which forms a vital part of the present invention;; Fig. 6 is a graph showing in terms of Standardized flow amount and Pressure ratio, the variation in turbine capacity of a turbine equipped with the present invention; Fig. 7 is a sectional elevation of a second embodiment of the present invention; Fig. 8 is a sectional elevation of a third embodiment of the present invention; and Fig. 9 is a sectional elevation showing a fourth embodiment of the present invention.

Turning now to Figs. 3 and 4, a first embodiment of the present invention is shown. In this arrangement, a shaft 10 extends through the scroll housing 12 and is reciprocatively mounted in bushes 14, 1 6. The bush 1 6 is located immediately adjacent the final (viz., the downstream) portion or tongue 18 of the scroll so that the shaped tip 20 of the shaft 10 may be extended into the flow of exhaust gases just prior to entry of same into the turbine impeller 22.As best seen in Fig. 3, when the shaft is driven by an actuator 24 to cause the tip 20 to extend out of the bush 1 6 to the fullest extent, the exhaust gases are deflected as shown by the arrow, whereby all the exhaust gases circulating in the envelope defined between the broken line and the inner wall of the scroll housing are directed into the impeller 22. Hence, during low engine speed operation wherein the amount of exhaust gas discharged therefrom is relatively small, the turbine impeller 22 may be rotated by the high velocity gases directed thereagainst to produce an adequate amount of torque and hence supply the engine with an adequate supercharging pressure.

However, as the amount of exhaust gas discharged from the engine (not shown) rises and approaches the point where the impeller 22 is rotated at an excessive speed, the shaft 10 may be retracted to reduce the degree of projection of the tip 20. With the accordingly reduced degree of exhaust gas deflection some of the normally deflected exhaust gases are allowed to circulate within the scroll housing without being actually directed into the impeller 22, whereby the conversion of exhaust gas energy into kinetic energy is partially reduced.

To control the degree of projection of the tip 20, the actuator 24 may be of the type used with Fig. 1 prior art arrangement or one similar to those used to actuate the "waste-gates" of arrangements now in common use may be employed. The actuator may be responsive to any one of a number of operating parameters such as turbine RPM, the pressure prevailing in the scroll, engine RPM etc.

Fig. 5 shows three possible tip configurations.

These configurations are such as to promote smooth turbulence-free deflection for reasons which will apparent to those skilled in the art to which this invention pertains.

Fig. 6 is a graph showing the turbine capacity variation produced by retracting the shaft and tip 20 from the most projected position to one where the tip 20 is not extended into the fluid flow in the scroll. In this graph the trace A represents, in terms of standardized fluid flow and pressure ratio, the turbine capacity with the tip fully extended.

Trace B shows the turbine capacity with no projection. Thus, as will be appreciated, as the tip is extended, for any given pressure ratio value, the amount of fluid which may pass through the turbine increases.

Fig. 7, shows a second embodiment of the present invention. In this arrangement the shaft 10 is arranged parallel with the axis of rotation, of the impeller 22. This arrangement features the advantages of requiring only a single bush 26 and that the shaft is not exposed over a substantiai portion thereof to the hot incoming exhaust gases.

The effect of this arrangement is identical with that of the first.

Fig. 8 shows a third embodiment of the present invention. In this arrangement the shaft 20 is arranged at an angle with respect to the axis of rotation of the impeller 22. Again this arrangement requires only a single bush 26 and is not exposed, other than the tip, to exhaust gases to any degree.

Fig. 9 shows a fourth embodiment of the present invention. In this arrangement the shaft 26 is arranged to be rotatable as distinct from reciprocable, and the tip is replaced with a shaped groove 30. The shaft 28 is adapted to be rotated by an actuator and the shape of the groove 30 selected to vary the degree of deflection of exhaust gases in a manner similar to the previously disclosed arrangements.

Thus, it will be appreciated that the present invention represents a considerable improvement over the prior art in both terms of reliability and simplicity.

Claims

1. A device for varying the capacity of a radial turbine which includes a scroll housing and a turbine impeller located at the downstream end of said scroll, comprising: a shaft movable with respect to said scroll housing and disposed in said scroll housing so as to have a portion located immediately adjacent the downstream end thereof and a shaped portion on said shaft portion; and means for moving said shaft so that said shaped portion selectively deflects the fluid which flows in said scroll housing with respect to said impeller in accordance with a sensed operating parameter.

2. A device as claimed in claim 1, wherein said shaft is adapted to be reciprocative and said shaped portion takes the form of a shaped tip formed at one end of said shaft.

3. A device as claimed in claim 1, wherein said shaft is adapted to be rotatable and said shaped portion takes the form of a shaped groove in said shaft.

4. A device as claimed in claim 1, wherein said shaft is disposed to extend through said scroll housing normally with respect to the axis of rotation of said turbine impeller.

5. A device as claimed in claim 2 or 3, wherein said shaft is disposed parallel with respect to the axis of rotation of said turbine impeller.

6. A device as claimed in claim 2, wherein said shaft is disposed at an angle with respect to the axis of rotation of said turbine impeller.

7. A device as claimed in claim 4, wherein said shaft is supported in said scroll housing by two separate bushes.

8. A device as claimed in claim 2, wherein said shaft is supported by a single bush.

9. A device as claimed in claim 1, wherein said moving means takes the form of an actuator which is responsive to a selected operating parameter

10. A device substantially as hereinbefore described with reference to Figs. 3 to 5, or Fig 7, or Fig 8, or Fig 9 of the accompanying drawings