INLET GUIDE VANES FOR TURBOCHARGER COMPRESSORS

Abstract

A device and method for imparting a negative pre-whirl to an airstream entering a compressor wheel of a turbocharger. Using a plurality of radially positioned vanes through which the airstream to the compressor wheel communicates, a negative pre-whirl is imparted to the airstream entering the compressor wheel from an intake passage. This pre-whirl is imparted by positioning the vanes radially within an engageable ring and curving the vanes in a direction opposite the direction of rotation of the compressor wheel. Performance is further enhanced by a hub centrally positioned with the vanes where the hub includes a cavity sized to encapsulate a compressor nut and eliminate air turbulence therefrom.

Claims

1. In a turbocharger, used on an internal combustion engine, a method for improving the performance thereof comprising: positioning vanes having a curved shape imparting a negative pre-whirl to an airstream being communicated to a compressor wheel receiving said airstream from an intake passage of a compressor casing of said turbocharger; and said negative pre-whirl being in a direction opposite a direction of rotation of the compressor wheel.

2. The method of claim 1 additionally comprising the step of: forming said vanes with a curve running opposite to a rotation of said compressor wheel; and axially positioning a bullet-nosed hub mounted in the air intake passage of the compressor casing, in a position in front of a nut engaged to a hub turning a compressor of said turbocharger.

3. A turbocharger intake air apparatus, comprising: a plurality of radially oriented vanes; said vanes positioned within a passage of a compressor casing which communicates an incoming airstream to a compressor wheel of a turbocharger and said vanes shaped to impart a negative pre-whirl to said airstream communicated to said compressor wheel of said turbocharger; and said negative pre-whirl being in a direction of rotation opposite a rotational direction of said compressor wheel.

4. The turbocharger intake air apparatus of claim 3, additionally comprising: said plurality of radially oriented vanes being curved in a direction opposite to said rotational direction of said compressor wheel.

5. The turbocharger intake air apparatus of claim 4, additionally comprising: said plurality of radially oriented vanes extending from a center point to distal ends; and a ring engaged with said distal ends, said said ring adapted for a circumferential engagement within said passage of said turbocharger which communicates said airstream to said compressor wheel.

6. The turbocharger intake air apparatus of claim 5, additionally comprising: a hub located at said center point, said hub curving to a point on a first end and having a cavity at a second end opposite said first end; and said cavity sized to encapsulate a lock nut engaged at a front of said compressor wheel, whereby turbulence from said lock nut formed in said air communicated to said compressor wheel is eliminated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 depicts the turbocharger air inlet velocity triangle, taken at the inducer geometric mean diameter.

[0016] FIG. 2 is a turbocharger compressor air inlet velocity triangle, showing the effect of negative pre-whirl.

[0017] FIG. 3 is a cross section of a typical turbocharger compressor component showing the addition of the pre-whirl vane ring herein disclosed positioned within the passage providing an airstream to the compressor wheel, and shown in FIG. 3a.

[0018] FIG. 3a depicts a cross section of a pre-whirl vane ring which may be adapted for engagement within existing and newly manufactured turbochargers.

[0019] FIG. 3b depicts a perspective view of the device such as in FIGS. 3 and 3a, configured for operative positioning upon a turbocharger.

[0020] FIG. 4 is a front view showing one preferred mode of the pre-whirl vane ring having a plurality of radially positioned vanes, as in FIGS. 3 and 3a.

[0021] FIG. 5 is a section through of one pre-whirl vane showing a preferred curvature of the vane to impart negative pre-whirl to the airstream communicated thereover and to the compressor wheel.

[0022] FIG. 6 is a graphic depiction of experimental compressor performance results of the prior art negative pre-whirl produced by movable flat plate vanes.

[0023] FIG. 7 is a graphic depiction of compressor performance comparing such flat plate vanes and the curved pre-whirl vanes herein disclosed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0024] Current design practice consists of selecting a reasonable value for the velocity of the compressor inlet airflow (such as 250/sec) and designing for constant axial inlet velocity over the radius of the compressor wheel inducer vanes.

[0025] Shown in FIG. 1 is a typical air inlet velocity triangle, showing the inlet velocity at the geometric mean diameter of the compressor wheel inducer. The non-movable pre-whirl vanes of the device and method herein are configured to impart a direction to the absolute air inlet velocity of an airstream being communicated to the compressor wheel, which is opposite to the rotation of the compressor wheel.

[0026] As depicted in FIG. 2, the negative pre-whirl angle, , a current range for optimal performance improvement would be in the range of 15 to 25. However, other pre-whirl angles for example in a range between 5 to 50 can be chosen for specific compressor performance enhancements. Additionally, while curved vanes are preferred herein as experimentation has shown such to provide significant improvement in compressor performance, planar or straight vanes might also be employed in the device herein and still yield a slight performance increase of the turbocharger, and while not optimum, such a configuration is anticipated within the scope of this application.

[0027] In the graphic depictions of FIGS. 1 and 2, U represents the wheel velocity, C the absolute air inlet velocity, and W the relative air inlet velocity, usually plotted in feet per second. The compressor wheel inducer vanes in FIG. 1 are designed to match the angle of the relative air inlet velocity W.

[0028] FIG. 3 shows a cross section of the turbocharger compressor device 10 and method herein having a pre-whirl component shown as a vane ring 15 operatively positioned in operative engagement within a typical turbocharger 11, consisting of a compressor wheel 12, a compressor casing 13, and a back plate 14. In such operative positioning, the device 10 is positioned in front of the compressor wheel 12 and within the passage 21 communicating an incoming airstream to the compressor wheel 12. FIG. 3 also illustrates the positioning of fixed pre-whirl vanes 18, which as shown are formed as a vane ring 15, and which are positioned within the air inlet section of the compressor casing 13 in accordance with the invention. It should be noted that in newly manufactured turbochargers the vanes 18 providing the pre-whirl could be operatively positioned without the ring and any such positioning of vanes 18 to communicate a negative pre-whirl to the stream of incoming air to the compressor wheel 12 of a turbocharger 11 is considered within the scope of this patent.

[0029] A conventional turbocharger rotating assembly is clamped together by a rotor lock nut 16 which usually has a hexagonal shape for engagement of a wrench to tighten the assembly. The hexagonal shape of the lock nut 16, rotating at very high speed in current turbochargers, produces a turbulence in the inlet airflow. This turbulence impairs the airflow into the compressor wheel 12 and the overall performance of the turbocharger.

[0030] Alone, or in combination with the plurality of pre-whirl vanes 18 herein, the positioning of a cone or bullet-shape hub 17 which is configured at a second end with a cavity 19 adapted to surround and encapsulate the lock nut 16, eliminates or significantly reduces any turbulence in the inlet airflow, caused by the high speed of rotation of the lock nut 16. As noted this hub 17 may be employed without the pre-whirl vanes 18 and yield a performance increase to the turbocharger by elimination of turbulence in the incoming airstream and such is anticipated. However, employment of the pointed or bullet shaped hub 17 in combination with the pre-whirl vanes 18 is particularly preferred as a symbiotic relation therebetween provides significant enhancement of airflow provided to the compressor wheel 12 from that of conventional turbochargers.

[0031] The pre-whirl vanes 18 in the pre-whirl vane ring 15 are curved to thereby impart a rotation to the airflow communicated to the compressor wheel 12 through the passage 21 communicating an incoming airstream to the compressor wheel 12, in a direction opposite to the rotation of the compressor wheel 12. This opposite direction rotation of the inlet airflow through the passage 21 is usually designated as negative pre-whirl. Negative pre-whirl directs the inlet airflow into the compressor wheel 12 in such a way that the mass flow of inlet air is increased, and the pressure generated by the compressor 12 is also increased. Depending on the design of the compressor wheel 12, the efficiency can be higher with negative pre-whirl imparted to the incoming airstream.

[0032] FIG. 4 shows a front view of a negative pre-whirl vane ring 15. While shown employing fifteen vanes 18, which is a current preferred mode, the vane ring 15 can have anywhere from three vanes 18 to fifty vanes 18 depending on the cross section of the vane ring 15 and configuration of the compressor wheel 12 receiving the pre-whirl airflow through the passage 21 (FIG. 3) which is generated by the curve of the vanes 18 of the vane ring 15.

[0033] FIG. 5 is a section through one pre-whirl vane 18, showing how the vane curvature turns the inlet airflow from a substantially laminar flow, along an axial direction, through the passage 21 and causes the airstream to enter the compressor wheel 12 at a small angle opposite to the counter clockwise wheel rotation of the compressor wheel 12 (see FIG. 2).

[0034] A limited amount of experimental data is reproduced from prior art literature has in theory shown a potential increase in mass flow and pressure ratio produced by -20 degrees rotatable flat plate pre-whirl vanes (see FIG. 6). However, such is just research and theory, and in some cases teaches the employment of rotating flat vanes rather than fixed vanes, if the taught calculations were employed to reduce the taught configuration to practice.

[0035] FIG. 7 illustrates an improvement in performance based on the disclosed device and method herein, comparing the previously taught pre-whirl flat plate vanes and the device and method herein positioning curved pre-whirl vanes 18 and combining such with an axially positioned hub 17, in a vane ring 15 configuration, to deliver a turbulence-free negative pre-whirl airflow to a turbocharger compressor 12.

[0036] The negative pre-whirl vane ring 15 with the bullet-shaped hub 17 can be made as an inexpensive aluminum casting or fabricated from other materials. In this ring configuration, the vane ring 15 may be inserted in the inlet section of new or existing compressor casings, as shown in FIG. 3, by forming the casing in a manner adapted to circumferentially engage the vane ring 15 or through a simple machining operation in the casing air inlet section. Thus, this invention provides an inexpensive means of significantly improving the performance of small turbocharger compressors that will result in a significant improvement in performance of the engines on which such turbochargers are mounted, and in the performance of vehicles in which the turbocharged engines are used. The unique negative pre-whirl vane ring 15 of the device and method herein employs curved vanes 18 and a bullet-shaped hub 17, which yields a significant increase in flow range and pressure ratio obtained from the turbocharger compressor. The graphic depiction in FIG. 7 indicates that curved vanes 18 can increase the flow range and pressure ratio over that obtained using previously taught movable flat plate vanes. Thus, the combination of curved vanes 18 fixed in position within a vane ring 15 of this invention, combined with a bullet-shaped hub 17, in a combined symbiotic configuration, will improve the flow range and pressure ratio of turbocharger compressors to a significant degree over the prior art.

[0037] While all of the fundamental characteristics and features of the turbocharger pre-whirl, device and method have been shown and described herein, with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosure and it will be apparent that in some instances, some features of the invention may be employed without a corresponding use of other features without departing from the scope of the invention as set forth. It should also be understood that various substitutions, modifications, and variations may be made by those skilled in the art without departing from the spirit or scope of the invention. Consequently, all such modifications, variations and substitutions are included within the scope of the invention as defined by the following claims.