Patent Application
20200340497
The present disclosure relates to centrifugal compressors, such as used in turbochargers, and more particularly relates to centrifugal compressors in which the effective inlet area or diameter can be adjusted for different operating conditions by means of an inlet-adjustment mechanism disposed in the air inlet for the compressor.
An exhaust gas-driven turbocharger is a device used in conjunction with an internal combustion engine for increasing the power output of the engine by compressing the air that is delivered to the air intake of the engine to be mixed with fuel and burned in the engine. A turbocharger comprises a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically the turbine housing is formed separately from the compressor housing, and there is yet another center housing connected between the turbine and compressor housings for containing bearings for the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and that receives exhaust gas from an engine. The turbine assembly includes a nozzle that leads from the chamber into the turbine wheel. The exhaust gas flows from the chamber through the nozzle to the turbine wheel and the turbine wheel is driven by the exhaust gas. The turbine thus extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through an inlet of the compressor housing and the air is compressed by the compressor wheel and is then discharged from the housing to the engine air intake.
Turbochargers typically employ a compressor wheel of the centrifugal (also known as “radial”) type because centrifugal compressors can achieve relatively high pressure ratios in a compact arrangement. Intake air for the compressor is received in a generally axial direction at an inducer portion of the centrifugal compressor wheel and is discharged in a generally radial direction at an exducer portion of the wheel. The compressed air from the wheel passes through a diffuser before being delivered to a volute, and from the volute the air is supplied to the intake of an internal combustion engine.
The operating range of the compressor is an important aspect of the overall performance of the turbocharger. The operating range is generally delimited by a surge line and a choke line on an operating map for the compressor. The compressor map is typically presented as pressure ratio (discharge pressure Pout divided by inlet pressure Pin) on the vertical axis, versus corrected mass flow rate on the horizontal axis. The choke line on the compressor map is located at high flow rates and represents the locus of maximum mass-flow-rate points over a range of pressure ratios; that is, for a given point on the choke line, it is not possible to increase the flow rate while maintaining the same pressure ratio because a choked-flow condition occurs in the compressor.
The surge line is located at low flow rates and represents the locus of minimum mass-flow-rate points without surge, over a range of pressure ratios; that is, for a given point on the surge line, reducing the flow rate without changing the pressure ratio, or increasing the pressure ratio without changing the flow rate, would lead to surge occurring. Surge is a flow instability that typically occurs when the compressor blade incidence angles become so large that substantial flow separation arises on the compressor blades. Pressure fluctuation and flow reversal can happen during surge.
In a turbocharger for an internal combustion engine, compressor surge may occur when the engine is operating at high load or torque and low engine speed, or when the engine is operating at a low speed and there is a high level of exhaust gas recirculation (EGR). Surge can also arise when an engine is suddenly decelerated from a high-speed condition. Expanding the surge-free operation range of a compressor to lower flow rates is a goal often sought in compressor design.
Applicant is the owner of several patent applications (hereinafter, “the commonly owned Applications”) describing various inlet-adjustment mechanisms for delaying the onset of surge to lower flow rates at a given compressor pressure ratio (i.e., shifting the surge line to the left on the compressor map), including but not limited to: Application Ser. No. 14/642,825 filed on Mar. 10, 2015; Ser. No. 14/551,218 filed on Nov. 24, 2014; Ser. No. 14/615,428 filed on Feb. 6, 2016; Ser. No. 15/446,054 filed on Mar. 1, 2017; Ser. No. 15/446,090 filed on Mar. 1, 2017; Ser. No. 15/456,403 filed on Mar. 10, 2017; Ser. No. 15/836,781 filed on Dec. 8, 2017; Ser. No. 15/806,267 filed on Nov. 7, 2017; Ser. No. 15/822,093 filed on Nov. 24, 2017; Ser. No. 15/907,420 filed on Feb. 28, 2018; Ser. No. 15/904,493 filed on Feb. 26, 2018; and Ser. No. 15/909,899 filed on Mar. 1, 2018; the entire disclosures of all of said applications being hereby incorporated herein by reference. Inlet-adjustment mechanisms in accordance with said applications generally include a plurality of blades or vanes that collectively circumscribe an orifice whose effective diameter is adjustable by movement of the blades or vanes radially inwardly or outwardly. By adjusting the effective compressor inlet diameter to a reduced value at operating conditions where surge may be imminent, the surge line on the compressor map is shifted toward lower flow rates, thereby preventing surge from occurring at said operating conditions.
The present application is concerned with improvements to turbochargers having an inlet-adjustment mechanism generally of the type described above.
The present disclosure is directed to turbochargers having a compressor and an inlet-adjustment mechanism for the compressor that can enable the surge line for the compressor to selectively be shifted to the left (i.e., surge is delayed to a lower flow rate at a given pressure ratio). It has been found that when the inlet-adjustment mechanism is closed, noise and flow pulsation can occur in the air inlet of the compressor. The present disclosure describes embodiments of turbochargers that can at least partially mitigate such noise and flow pulsation. Described herein are turbochargers having the following features:
In accordance with some embodiments, a series of acoustic cavities are defined within the first housing portion, and there are a plurality of openings respectively leading into the various cavities.
In one embodiment, the openings are defined in the air inlet wall, and can be distributed axially and circumferentially in the air inlet wall.
In another embodiment, a plurality of openings are defined in the radially extending upstream wall of the first housing portion, and a plurality of acoustic cavities are defined within the first housing portion, one opening for each cavity. The openings are circumferentially spaced apart about the annular space that houses the inlet-adjustment mechanism.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
A turbocharger 10 in accordance with one embodiment of the invention is illustrated in axial cross-sectional view in
The turbine wheel 22 is disposed within a turbine housing 24 that defines an annular chamber 26 for receiving exhaust gases from an internal combustion engine (not shown). The turbine housing also defines a nozzle 28 for directing exhaust gases from the chamber 26 generally radially inwardly to the turbine wheel 22. The exhaust gases are expanded as they pass through the turbine wheel, and rotatably drive the turbine wheel, which in turn rotatably drives the compressor wheel 14 as already noted.
With reference to
The second housing portion 16-2 defines a shroud surface 16s that is closely adjacent to the radially outer tips of the compressor blades. The shroud surface defines a curved contour that is generally parallel to the contour of the compressor wheel.
The compressor housing 16 upstream of the compressor wheel 14 defines an annular space S located radially outward of the air inlet 17. An axial extent of the annular space is bounded between a radially extending upstream wall UW which is part of the first housing portion 16-1 and a radially extending downstream wall DW which is part of the second housing portion 16-2. A radially innermost extremity of the annular space is open to the air inlet 17.
The compressor of the turbocharger includes an inlet-adjustment mechanism 100 disposed in the annular space S of the compressor housing. The inlet-adjustment mechanism is operable for adjusting an effective diameter of the air inlet into the compressor wheel. As such, the inlet-adjustment mechanism is movable between an open position and a closed position, and various points intermediate said positions.
With reference now to
As shown in
The invention is not limited to inlet-adjustment mechanisms having arcuate pivotable blades as shown. Various other types of inlet-adjustment mechanisms can be used in the practice of the present invention, including but not limited to the mechanisms described in the commonly owned Applications as previously noted and incorporated herein by reference.
At low flow rates (e.g., low engine speeds), the inlet-adjustment mechanism 100 can be placed in the closed position of
At intermediate and high flow rates, the inlet-adjustment mechanism 100 can be partially opened as in
As previously noted, Applicant has discovered that when the inlet-adjustment mechanism is in the closed position to reduce the effective inlet diameter, noise and flow pulsation or fluctuation in the inlet can occur. The present invention is aimed at mitigating such noise and flow pulsation, through the provision of a series of acoustic cavities within the compressor housing upstream of the inlet-adjustment mechanism. With reference to
Each acoustic cavity with its associated openings acts as a Helmholtz resonator. The various Helmholtz resonators can each be tuned to a particular frequency so that noise of that frequency is attenuated by the resonator. As those skilled in the art will recognize, the frequency to which a Helmholtz resonator is tuned is primarily a function of the volume of the acoustic cavity, the length of the neck that leads from the main fluid duct into the cavity, and the cross-sectional area of the neck. In accordance with the invention, the number of acoustic cavities and their dimensional parameters can be selected to attenuate the noise frequency components that are of most concern. Thus, while the illustrated embodiment has eight acoustic cavities, the invention is not limited to any particular number of cavities. Similarly, while there are two openings into each cavity in the illustrated embodiment, the invention is not limited to any particular number of openings.
A second embodiment of the invention is illustrated in
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, it is within the scope of the invention to combine Helmholtz resonators according to the first embodiment with quarter-wave resonators according to the second embodiment within the same turbocharger compressor. Additionally, as noted, the number, sizes, and arrangement of the acoustic cavities and their associated openings can be different from those shown in the drawings, the invention not being limited in such respects. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
