Turbocharger Compressor With Dual Collector Chambers

Abstract

Disclosed is a single stage, centrifugal compressor component of a turbocharger for an internal combustion engine in which the vanes of the compressor wheel are formed to provide frontal vane portions extending radially beyond the adjoining vane portions. An internal wall of the compressor wheel cover forms two discrete chambers or passages, one accommodating air flow induced by the radially extending vane portions, the other accommodating flow induced by the adjoining vane portions. Heat exchange may occur across the wall between the two air flow paths.

Description

BACKGROUND OF THE INVENTION

The desirability of reducing the temperature of supercharging air before its introduction into the intake of an internal combustion engine is well known. U.S. Pat. No. 3,143,103 discloses a multi-stage turbocharger compressor having a separate, axial-flow stage for providing cooling air to an external heat exchanger through which passes the high pressure, high temperature air for charging the engine. The maintenance of maximum oxygen content per unit volume of charging air, as pointed out in the above mentioned patent, is an important advantage of charge air cooling, however, the more recent concern with reduction of undesirable engine exhaust emissions makes such treatment of the engine charging air a matter of increasing interest for transport and industrial diesel engine users and manufacturers. Lower combustion temperatures, in general, produce lower toxic nitrogen oxide exhaust emissions, and since cooling the engine charging air provides lower combustion temperatures, providing a compact, efficient charge air cooling turbocharger compressor assembly is a matter of growing urgency and importance.

The concept of the present invention is embodied in a compact, single stage, centrifugal compressor in which the compressor wheel vanes are formed to provide a flow of relatively cool air at relatively low pressure, this flow being maintained separate from the flow of high temperature, high pressure air induced by the main portion of the vanes. The separate air flows induced by the two portions of the wheel vanes are, normally, placed in heat exchange relation to each other in an external heat exchanger, however, since heat exchange can begin immediately, within the compressor wheel cover, the external heat exchanger may be of reduced size. The frontal portions of the vanes, providing the cooling air flow, may be separate from the adjoining vane portions and carried on a hub separate from that carrying the adjoining vane portions. With the two hubs mounted concentrically on the drive shaft, because of a conical undercut on the rear face of the frontal vane portions and their hub, a vibration damping force is applied to each of the adjoining vane portions by its corresponding frontal vane portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a turbocharger embodying the present invention with the compressor component shown in sections.

FIG. 2 is an end view of the turbocharger shown in FIG. 1.

FIG. 3 is a fragmentary, top view of the blades of the compressor wheel shown in FIG. 1.

FIG. 4 is a schematic illustration of the turbocharger shown in FIG. 1 incorporated into a system utilizing an exchanger and providing for the turbocharging of an internal combustion engine.

FIG. 5 is a fragmentary view of a portion of the compressor wheel and cover such as shown in FIG. 2 but illustrating a modified form of the construction.

FIG. 6 is a top plan view of a fragment of a modified form of the compressor wheel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIGS. 1 and 2, there is illustrated an exhaust gas driven turbocharger which is composed of a turbine housing 10 enclosing a conventional bladed turbine wheel (not shown) which drives the shaft 14. The turbine housing is provided with a flanged inlet passage 18 which transmits engine exhaust gases to the turbine wheel. The turbine component itself is of conventional construction. High pressure gases, entering the turbine, are expanded through the turbine wheel, causing the shaft 14 to rotate at high speed. The spent gases are discharged through the turbine outlet passage 19.

Attached to the turbine housing casting 10 is an intermediate casting 21, the casting 21 and the turbine housing 10 being held in sealed relation by means of clamp ring 22. The casting 21 is nonsymmetrical in configuration and includes a central portion 24 and an outwardly flanged portion 27. The central portion 24 of the casting 21 is provided with a central aperture 34 through which the shaft 14 extends. Within this aperture the portion 24 carries rotary and thrust bearings indicated generally at 36 which permit free rotation of the shaft.

Secured to the flanged portion 27, by means of clamp ring 37, is a compressor cover casting indicated generally at 38. Extending within, and integral with the cover casting 38 is a curved wall 39. The wall has extending portions 39a which define the circular, common boundary 39b between two chambers 41 and 42.

Chamber 41 encircles the compressor wheel, to be subsequently described in detail, and forms a generally annular collector area whose outlet is formed at the tangentially extending outlet passage 43 (FIG. 2). As may be seen in FIG. 1, the chamber 42 forms a volute-type collector and diffuser passage. An extending portion 39c of the wall 39 provides the narrow diffuser passage 43 extending generally radially from the tips of the compressor wheel vanes, to be subsequently described. The volute chamber or passage 42 has its outlet at the tangentially extending outlet passage 44 (FIG. 2).

The extending, reduced diameter portion of the shaft 14 supports a centrifugal type compressor wheel indicated generally at 46 carrying a plurality of radially extending vanes. As may best be seen in FIGS. 1 and 3, the vanes each have a frontal portion 47 leading, or in front of, the adjoining vane portions 48. The frontal portion 47 of each of the vanes has a radially extending portion 47a which extends radially beyond the adjoining vane portion 48 and, it will be noted, the circular common boundary between the chambers 41 and 42 is located adjacent the junction of the radially extending frontal portions 47a and the adjoining vane sections 48. The frontal vane portions 47 are carried by a hub portion 51 supported on the shaft 14, the hub portion 51 being pressed against the adjacent hub member 52 which carries the adjoining vane portions 48. The hub 51 and the hub portion 52 are held in place by the tightening down of the lock nut 53 on the threaded end of the shaft 14. It will be understood that the edges of the vane frontal portions 47 engage the edges of the adjoining vane portions 48 and, as may best be seen in FIG. 3, the bucket-forming curvature of the vanes extends continuously and smoothly across both the radially extending frontal vane portions 47 and the adjoining vane portions 48.

As shown by broken line 56 in FIG. 1, the rear face of the hub 51 and the trailing edges of the frontal vane portions 47 are slightly undercut, preferably in conical configuration as indicated by broken line 56, so that as the hub 51 is pressed against the hub portion 52 by tightening of the locknut 53, the frontal vane portions 47 apply a vibration damping force to the corresponding adjoining vane portions 48, the damping force being concentrated adjacent the outer marginal edges of the adjoining vanes 48. It will be understood that broken line 56 illustrates the rear face of the hub 51 and the frontal vane portions 47 before the hub is tightened against the portion 52. As the nut 53 is tightened down the hub portion and the vanes are deformed slightly so as to bring them into edge engagement with the adjoining vane portions and the hub 51 into engagement with the hub portion 52, the deformation resulting in the damping force applied at the outer edges of the adjoining vane portions 48.

In operation, as the compressor wheel 46 is rotated at high speed, air is moved through the compressor inlet passage 58. The flow of gases induced by the radially extending frontal vane portions 47a moves past the circular boundary 39b and into the collector chamber 41. The remaining portion of the gas flow, induced by the frontal vane portions 47 which register with the adjoining vane portions 48, moves through the narrow diffuser passage 43 into the volute diffuser passage or chamber 42. The air moving to the chamber 41 is at a lower temperature and pressure than is the air moving through the chamber 42 and, as may best be seen in FIG. 4, the flow of air through the chamber 41, exiting through the outlet 43, is conveyed to a conventional air-to-air heat exchanger indicated schematically at 61. The high temperature high pressure air moving through the volute passage 42 exits through the outlet 44 and is conducted to the heat exchanger 61. Because of the heat exchange between the two discrete air flows, the temperature of the air from the chamber 42 is lowered before it is introduced into the intake manifold 62 of the internal combustion engine shown schematically at 63.

Referring to FIG. 5, a modified form of the turbocharger compressor component is illustrated. The structure of FIG. 5 differs from that described above in that means are provided to extend the surface of wall 68, the counterpart of wall 39 of FIG. 1, within the chamber 41. This means may take the form of integral fins 69 which aid in heat transfer across wall 68.

FIG. 6 discloses a modified form of vane design for the compressor wheel. In this design all of the bucket-forming curvature extends across the radially extending frontal portion 71 of the vanes, the adjoining vane portions 72 being uncurved. Since the uncurved adjoining vane portions 72 and the hub portion from which they extend are formed separately from the curved frontal vane portions 71, simpler casting and manufacturing methods may be used in producing this uncurved portion of the wheel.

The compressor wheel and cover or housing construction of the present invention permits heat exchange between the high temperature air and the lower temperature and pressure air to begin within the compressor housing itself. While in FIG. 4 an external heat exchanger is illustrated for completing the temperature reduction of the air charge for the engine, by use of means for extending the heat exchange surfaces within the compressor housing (by means of fins 69 of FIG. 5, for example) the size and capacity of the external heat exchanger may be reduced. Where air charge cooling requirements are relatively low, use of the structure of the present invention can eliminate the necessity of utilizing a separate, external heat exchanger. Each of the adjoining vane portions 48, which provide the normal, single stage, centrifugal compressor wheel output, have exerted on them a vibration damping force applied to each vane primarily adjacent the circular wall edge 39b. Both the high temperature, high pressure charge air and the cooler air to be used in heat exchange are supplied by a compact, single stage turbocharger compressor. This permits packaging or mounting the turbocharger and heat exchanger in the engine structure itself and eliminates the necessity for locating the heat exchanger core at the engine radiator as is necessary where engine radiator fan air is used as the coolant for the charge air provided by the turbocharger. The use of the turbocharger of the present invention in conjunction with a minimum size heat exchanger, as compared to location of a heat exchanger adjacent the engine radiator using the radiator fan air for cooling, is particularly advantageous for powered vehicles or machinery having extensive off-highway use. In such applications radiator fan air flow passages tend to become blocked by dust, leaves or other debris and the required cooling of the charge air cannot take place. Since in the arrangement shown in FIG. 5, clean air is supplied to both flow passages through the heat exchanger, there is no tendency for it to become obstructed.

Claims

I claim:

1. A turbocharger compressor of the single stage centrifugal type having a compressor wheel rotated by a drive shaft and a cover enclosing said wheel and having an intake passage aligned with the shaft axis, said compressor wheel having radially extending vanes thereon for moving air axially through said intake passage and impelling it radially outwardly transverse to said shaft axis, said vanes each having a frontal portion extending radially beyond the adjoining vane portion, a wall within said cover defining two concentric discrete collector chambers surrounding said wheel, said wall extending to provide a circular common boundary between said two chambers closely adjacent the junction of said radially extending frontal portion and the said adjoining portion of said vanes, whereby said radially extending frontal portion of the vanes moves air into one of said chambers and the said adjoining portions of the vanes move air into the other of said chambers, said wall defining said collector chambers being provided with rib elements axially extending into said one of the chambers and over which the air in the chamber travels in a circular path to increase the cooling effect of said wall and increase the heat transfer between said chambers, said frontal portion of each of said vanes being separate from but in edge-engagement with the corresponding adjoining vane portion, said frontal vane portions extending radially from a hub separate from but mounted on said drive shaft in abutting relation to the compressor wheel portion carrying said adjoining vane portions, the rear face of said hub and the trailing edges of said frontal vane portions being slightly undercut, whereby as said hub is pressed against the adjacent compressor wheel portion on said shaft, said frontal vane portions apply a vibration damping force against each of the adjoining vane portions with said undercut being formed by providing the surface defined by the rear face of said hub and the adjacent trailing edges of said frontal vane portions with a slightly conical contour and a locking nut threaded on said shaft and engaging the hub to press it against said adjacent compressor wheel portion.