DESC:A CENTRIFUGAL COMPRESSOR FOR TURBOCHARGER
FIELD OF THE INVENTION
The present invention is related to a centrifugal compressor for turbocharger. In particular, the present invention is related to a centrifugal compressor for turbochargers having varied trim to improve surge side performance without trading-off with the choke side performance and vice versa.
BACKGROUND OF THE INVENTION
Turbochargers are generally used to increase the performance of an internal combustion engine. A turbocharger extracts energy from engine exhaust via a turbine to drive a compressor that compresses the intake air and direct it to the engine. Turbochargers typically rely on compressor wheels consisting of fins or blades that rotate inside a casing. A rotating compressor wheel within compressor housing sucks air through an intake port, compresses it in an impeller passage, and diffuses it into a volute. The compressed air is then supplied to an intake manifold of an internal combustion engine. It is known that the clearance existing between the compressor wheel end and the casing forming the internal wall of the airflow duct degrades the efficiency of the engine. Thus the overall efficiency of the turbocharger is a function of compressor and turbine, whereas the compressor efficiency is dependent on the wheel geometry, housing and the intake port.
A compressor flow map as shown in Fig.1 (plot of pressure ratio versus mass fluid flow) helps to characterize the performance of a compressor. It is important for any compressor to have a wide operating envelope (13), as measured between the "choke line (14)" at which the mass flow rate is maximum that it can pass without very high overheating of the air and the "surge line (15)" which is a minimum mass air flow where the air can flow without surging, at a given rotational speed of a compressor wheel. A typical operating line (13) is shown in fig.1 which ensures that the compressor does not surge or overheat and the operating line is adequately spaced away from the surge as well as choke limits.
It is a challenging task to develop a compressor having an adequately wide flow range from surge on the low end to the choke on the high end. Many researches in this field have developed a host of designs and methods for extending the usable flow range.
Probably the most widely used and effective design for compressor flow range enhancement is to provide ported shroud (23) as shown in Fig.2a in the compressor housing at suitable locations radially adjacent to the impeller blade. These ported shroud design is provided with by-pass ports (24) enables recirculation of air flow back to the impeller intake as shown in Fig 2a, this apparently increases higher flow to the impeller thus enhancing the compressor surge limit at the lower flow side of the compressor map. However at a higher flow rate as shown in Fig 2b, a part of the incoming air flow connects the impeller at a distance marginally away from the impeller inlet, this apparently lowers the flow to the impeller thus enhancing the compressor choke limit. Thus optimized positioning of the by-pass ports is essential for maintaining the operating line envelop and maximizing the benefits on surge as well as choke sides.
Alternately, the performance on surge side can be improved by reducing the trim. Wherein, trim is the ratio of inducing diameter (D1) to the outer diameter (D2) (Trim = D1/D2) as shown in Fig.3. Generally trim reduction is done by chipping off material from the impeller wheel tip. Reducing the trim moves the flow towards the lower flow side. However this worsens the choke side performance, since the compressor geometry is fixed. Further removal of material is a tedious process and possesses higher chances of rejection rate, if material removed from the impeller wheel is beyond permissible limit of geometric dimension and tolerance.
However, compressor with reduced trim improves surge side performance by trading off the choke side performance, because of the fixed geometry of the compressor.
US patent document 9528527 discloses a compressor of an exhaust-gas turbocharger (ATL), having a compressor wheel and a compressor housing which has a housing longitudinal axis. An inlet duct runs from a compressor inlet to the compressor wheel. A recirculation duct has a compressor-wheel-side inflow opening and a compressor-inlet-side return flow opening. The inflow opening and the return flow opening can be opened and closed.
US Patent No. 9719518 discloses an adjustable trim centrifugal compressor with ported shroud, and turbocharger having same. Wherein the turbocharger having an inlet-adjustment mechanism in an air inlet for the compressor, operable to move between an open position and a closed position in the air inlet. The inlet-adjustment mechanism includes an axially elongated ring. In the open position, the radially outer surface of the ring is spaced from a tapering inner surface of the air inlet so that air can flow in an annular passage between the tapering surface and the ring, and the ring opens the ported shroud. In the closed position, the ring abuts the tapering surface to close off the annular passage and to close off the ported shroud. Movement of the inlet-adjustment mechanism from the open position to the closed position is effective to shift the compressor's surge line to lower flow rates.
In the above prior-art documents the axially elongated ring in the inlet increases the weight of the compressor and does not provide any acoustic effect. Furthermore, in the cited documents the ports have a flow reversal mechanism which produces a large recirculation area as shown in Fig.4 that extends far into the impeller intake. Such large recirculation of fluid in compressor is detrimental to the compressor efficiency and also to the acoustics which can easily travel upstream the turbocharger. The shorter recirculation of fluid in the compressor nearly eliminates the noise due to turbulence, swirl and squish of the fluid.
Therefore, for the above reasons there is need in art to provide a compressor having reduced trim without trading-off the choke side performance. Furthermore, a compressor without having any additional parts and having improved acoustic effect.
OBJECT OF THE INVENTION
The primary objective of the present invention is to provide a centrifugal compressor for turbochargers having varied trim.
Another objective of the present invention is to provide a centrifugal compressor for turbochargers having varied trim with improved surge side performance without trading-off with the choke side performance and vice versa.
Another objective of the present invention is to provide a centrifugal compressor for turbochargers having varied trim, wherein trim reduction is achieved by fluid flow known as fluid trim.
Still another objective of the present invention is to provide a centrifugal compressor for turbochargers having varied trim without machining off any material from the impeller wheel.
Yet another objective of the present invention is to provide a centrifugal compressor for turbochargers having varied trim without addition of new parts to the compressor.
Further objective of the present invention is to provide a centrifugal compressor for turbochargers having varied area of the recirculation zone.
Final objective of the present invention is to provide a centrifugal compressor for turbochargers having smaller recirculation zone which enables improved acoustic performance.
SUMMARY OF THE INVENTION
The present invention provides a centrifugal compressor for turbochargers having varied trim to improve compressor performance, comprising of: a housing (101), said housing (101) having an annular inlet (102) and an outlet (103); a shaft (104), said shaft (104) is positioned axially in the centre of the housing (101); a compressor wheel (105), said compressor wheel (105) is coupled with the shaft (104), wherein a plurality of blades (106) circumferentially spaced apart having its first edge attached to the surface of the compressor wheel and its second edge extending radially outwards, said second edge of the plurality of blades (106) comprising a leading edge (107) and a trailing edge (108); and a shroud wall (109) is positioned radially adjacent to the second end of the plurality of blades (106).
In an embodiment, the shroud wall (109) is provided with an opening (111) formed between the first end (121) of the housing and the said first end (123) of the shroud wall (109), wherein said second end (124) of the shroud wall is affixed to the second end (122) of the housing, forming a closed port (110) between the annular inlet (102) of the housing (101) and the said port side face (113) of the shroud wall (109).
In an embodiment of the present invention, wherein said annular inlet (102) receives the fluid at the varying flow rate proceeding towards the compressor wheel (105), wherein a part of fluid entering said annular inlet (102) is bypassed into the port (110), a recirculation zone (RZ) is formed near the shroud wall (109) and inducing diameter (D1) is varied, thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
In an embodiment of the present invention, wherein area of the recirculation zone varies according to the fluid flow rate into the annular inlet (102).

BRIEF DESCRIPTION OF THE DIAGRAM
Figure 1 depicts the typical compressor flow map plotted between pressure ratio versus mass fluid flow showing the wide operating envelope (13), measured between the "choke line (14)" and the "surge line (15)".
Figure 2a illustrates the state of art of a centrifugal compressor for turbocharger with ported shroud having recirculation zone at higher fluid flow rate.
Figure 2b illustrates the state of art of a centrifugal compressor for turbocharger with ported shroud having recirculation zone at lower fluid flow rate.
Figure 3 depicts the compressor with state of the art standard “trim”, ratio of inducing diameter (D1) to outer diameter (D2) of a centrifugal compressor for turbocharger with ported shroud.
Figure 4 represents a centrifugal compressor for turbocharger having varied trim to improve compressor performance according to the present invention.
Figure 5 describes the recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) ) in the inducing compressor area according to the present invention.
Figure 6a shows the vertical (45) positioning of second end (122) of the housing to the bypassed fluid flow at the closed port (110) between the annular inlet (102) and the said port side face (113) of the shroud wall (109).
Figure 6b shows the inclined (46) positioning of second end (122) of the housing to the bypassed fluid flow at the closed port (110) between the annular inlet (102) and the said port side face (113) of the shroud wall (109).
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention as embodied by “a centrifugal compressor for turbocharger”, succinctly fulfils the above-mentioned need(s) in the art. The present invention has objective(s) arising as a result of the above-mentioned need(s), said objective(s) being enumerated below. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety, and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/or any functional equivalent(s) even though, such structural alternative(s) and/or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation(s)/modification(s) applied to the structural alternative(s)/functional alternative(s) within its scope and purview. The present invention may be embodied in other specific form(s) without departing from the spirit or essential attributes thereof.
Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
The present invention provides a centrifugal compressor for turbochargers having varied trim to improve compressor performance, comprising of: a housing (101) having a first end (121) and a second end (122), wherein said housing (101) is provided with an annular inlet (102) and an outlet (103) for the main fluid flow; a shaft (104), said shaft (104) is positioned axially in the centre of the housing (101); a compressor wheel (105), said compressor wheel (105) is coupled with the shaft (104), wherein a plurality of blades (106) circumferentially spaced apart having its first edge attached to the surface of the compressor wheel and its second edge extending radially outwards, said second edge of the plurality of blades (106) comprising a leading edge (107) and a trailing edge (108); and a shroud wall (109) having a impeller side face (112) and a port side face (113), said shroud wall (109) is positioned radially adjacent to the second end of the plurality of blades (106), wherein a closed port (110) is formed between the annular inlet (102) of the housing (101) and the said port side face (113) of the shroud wall (109).
In the preferred embodiment of the present invention, wherein said shroud wall is provided with a first end (123) and a second end (124). Wherein said first end (123) of the shroud wall is provided with an opening (111) formed between the first end (121) of the housing and the said first end (123) of the shroud wall (109). Wherein said second end (124) of the shroud wall is affixed to the second end (122) of the housing, forming a closed port (110) between the annular inlet (102) of the housing and the said port side face (113) of the shroud wall (109).
In the preferred embodiment of the present invention, wherein said first end (123) of the shroud wall is positioned vertically or at an inclined position to the said main fluid flow at the annular inlet (102). Wherein said inclination of the first end of the shroud wall leads to a diverging port or a converging port.
In the preferred embodiment of the present invention, wherein said second end (122) of the housing is positioned vertical or inclined to the bypassed fluid flow at the closed port (110) between the annular inlet (102) and the said port side face (113) of the shroud wall (109).
In the preferred embodiment of the present invention, wherein said annular inlet (102) receives the main fluid flow at varying flow rate proceeding towards the said compressor wheel (105), a part of fluid is bypassed into the closed port (110) through a opening (111) formed between the housing and the said shroud wall (109), this creates a recirculation zone (RZ) near the shroud wall (109). Wherein the said recirculation zone varies the inducing diameter (D1) thereby varying the trim of the compressor. Wherein area of the said recirculation zone (RZ) varies according to the fluid flow rate into the said annular inlet (102).
In the preferred embodiment of the present invention, wherein said recirculation zone (RZ) is formed along the length of the port side face (113) of the shroud wall (109) in the inducing compressor area. Wherein said recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) varies the inducing diameter (D1) thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
In the preferred embodiment of the present invention, Wherein the said recirculation zone (RZ) additionally acts an acoustic curtain, which reduces or eliminates the noises produced due to the turbulence, swirl and squish of the fluid in the compressor.
In the preferred embodiment of the present invention, the said area of the recirculation zone (RZ) is inversely proportional to the main fluid flow rate at the annular inlet (102). Wherein at higher flow rate, smaller is the area of the recirculation zone resulting in higher inducing diameter (D1), which improves the choke side flow performance. At lower flow rate, larger is the area of the recirculation zone resulting in smaller inducing diameter (D1), which increases surge side flow performance.
Thus the present invention provides a centrifugal compressor for turbochargers having reduced trim with improved surge side performance without trading-off with the choke side performance. The present invention provides effective reduction in trim without machining off any material from the compressor wheel (105) or without addition of any new parts to the compressor, by providing a varied recirculation zone (RZ) which acts a "fluid trim". Further the said fluid trim with smaller recirculation zone acts as an acoustic curtain eliminating the noise due to turbulence, swirl and squish of the fluid in the compressor
EXAMPLE 1
The turbocharger receives the main fluid flow by the annular inlet (102) towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through a opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). Wherein said first end of the shroud wall (109) is vertical to said main fluid flow, providing a parallel uniform fluid flow width. This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). Wherein area of the said recirculation zone (RZ) varies according to the fluid flow rate into the said annular inlet (102). Wherein said recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) varies the inducing diameter (D1) thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
EXAMPLE 2
The turbocharger receives the main fluid flow by the annular inlet (102) towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through an opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). Wherein said first end of the shroud wall (109) is inclined to the said main fluid flow, providing a diverging port for the bypassed fluid. This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). Wherein, area of the said recirculation zone (RZ) varies according to the fluid flow rate into the said annular inlet (102). Wherein said recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) varies the inducing diameter (D1) thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
EXAMPLE 3
The turbocharger receives the main fluid flow by the annular inlet (102) towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through an opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). Wherein said first end of the shroud wall (109) is inclined to the said main fluid flow, providing a converging port for the bypassed fluid. This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). Wherein, area of the said recirculation zone (RZ) varies according to the fluid flow rate into the said annular inlet (102). Wherein said recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) varies the inducing diameter (D1) thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
EXAMPLE 4
The turbocharger receives the main fluid flow by the annular inlet (102) towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through an opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). Wherein said second end of the compressor housing is positioned vertical (45) to the said bypassed fluid flow as shown in Fig.6a. This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). Wherein, area of the said recirculation zone (RZ) varies according to the fluid flow rate into the said annular inlet (102). Wherein said recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) varies the inducing diameter (D1) thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
EXAMPLE 5
The turbocharger receives the main fluid flow by the annular inlet (102) towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through an opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). Wherein said second end of the compressor housing is positioned at an inclined angle (46) to the said bypassed fluid flow as shown in fig. 6b. This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). Wherein, area of the said recirculation zone (RZ) varies according to the fluid flow rate into the said annular inlet (102). Wherein said recirculation zone (RZ) formed along the length of the port side face (113) of the shroud wall (109) varies the inducing diameter (D1) thereby varying the trim of the compressor and acts as a “fluid trim” for the compressor.
EXAMPLE 6
The turbocharger receives the main fluid flow by the annular inlet (102) at a higher fluid flow rate towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through an opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). At higher main fluid flow rate, area of the recirculation zone is reduced. Due to lower area of the recirculation zone, the resulting inducing diameter (D1) of the compressor is increased, thus trim (D1/D2) of the compressor is increased. Therefore, performance of the turbocharger compressor, at the choke side is improved.

EXAMPLE 7
The turbocharger receives the main fluid flow by the annular inlet (102) at a lower fluid flow rate towards the said compressor wheel (105). A part of fluid is bypassed into the closed port (110) through an opening (111) formed between the first end of the compressor housing and the said first end of the shroud wall (109). This creates a recirculation zone (RZ) in the closed port (110) near the port side face (113) of the shroud wall (109). At lower main fluid flow rate, area of the recirculation zone is increased. Due to increased area of the recirculation zone, the resulting inducing diameter (D1) of the compressor is reduced, thus trim (D1/D2) of the compressor is reduced. Therefore, performance of the turbocharger compressor, at the surge side is improved.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the spirit and the scope of the invention may be made by a person skilled in the art.
,CLAIMS:We claim
1. A centrifugal compressor for turbochargers having varied trim to improve compressor performance, comprising of:
a. a housing (101) having a first end (121) and a second end (122), wherein said housing (101) is provided with an annular inlet (102) and an outlet (103) for the main fluid flow;
b. a shaft (104), said shaft (104) is positioned axially in the centre of the housing (101);
c. a compressor wheel (105), said compressor wheel (105) is coupled with the shaft (104), wherein a plurality of blades (106) circumferentially spaced apart having its first edge attached to the surface of the compressor wheel and its second edge extending radially outwards, said second edge of the plurality of blades (106) comprising a leading edge (107) and a trailing edge (108); and
d. a shroud wall (109) having a impeller side face (112) and a port side face (113), said shroud wall (109) is positioned radially adjacent to the second end of the plurality of blades (106), Characterized in that ,
Wherein said shroud wall is provided with a first end (123) and a second end (124), Wherein said first end (123) of the shroud wall is provided with an opening (111) formed between the first end (121) of the housing and the said first end (123) of the shroud wall (109), wherein said second end (124) of the shroud wall is affixed to the second end (122) of the housing, forming a closed port (110) between the annular inlet (102) of the housing (101) and the said port side face (113) of the shroud wall (109).

2. A centrifugal compressor for turbochargers having varied trim to improve compressor performance, as claimed in claim 1, wherein said first end (123) of the shroud wall is positioned vertically or at an inclined position to the said main fluid flow at the annular inlet (102).

3. A centrifugal compressor for turbochargers having varied trim to improve compressor performance, as claimed in claim 1, wherein said second end (122) of the housing is positioned vertically or inclined to the bypassed fluid flow at the closed port (110) between the annular inlet (102) and the said port side face (113) of the shroud wall (109).

4. A centrifugal compressor for turbochargers having varied trim to improve compressor performance, as claimed in claim 1, wherein said annular inlet (102) receives the main fluid flow at varying flow rate proceeding towards the said compressor wheel (105), a part of fluid is bypassed into the closed port (110) through a opening (111) formed between the first end (121) of the housing and the said first end (123) of the shroud wall (109).

5. A centrifugal compressor for turbochargers having varied trim to improve compressor performance, as claimed in claim 1, wherein said closed port (110) creates a recirculation zone (RZ) near the said port side face (113) of the shroud wall (109) varying the inducing diameter (D1), thereby varying the compressor trim ratio.

6. A centrifugal compressor for turbochargers having varied trim to improve compressor performance as claimed in claim 1, wherein said area of the recirculation zone is inversely proportional to the main fluid flow rate at the annular inlet (102).

7. A centrifugal compressor for turbochargers having varied trim to improve compressor performance as claimed in claim 1 and claim 6, wherein at higher main fluid flow rate, smaller is the area of the recirculation zone resulting in higher inducing diameter (D1), improving the choke side flow performance of the compressor.

8. A centrifugal compressor for turbochargers having varied trim to improve compressor performance as claimed in claim 1 and claim 6, wherein at lower main fluid flow rate, higher is the area of the recirculation zone resulting in reduced inducing diameter (D1), improving the surge side flow performance of the compressor.

9. A centrifugal compressor for turbochargers having varied trim to improve compressor performance as claimed in claim 1, wherein said recirculation zone (RZ) creates an acoustic curtain, which reduces or eliminates the noise due to the turbulence, swirl and squish of the fluid in the compressor.