Controlled Area Progression Vaned Diffuser

This application is a non-provisional patent application claiming priority under 35 U.S.C. § 119 (e) to U.S. Provisional Patent No. 63/649,796 filed on May 20, 2024.

The present disclosure relates generally to turbocharger systems for internal combustion engines and, more particularly, to compressors having controlled area progression vaned diffusers configured for efficient operation.

Turbochargers are used in numerous applications such as automotive, marine, and aerospace applications. Turbochargers operate by forcing more intake air into a combustion chamber of an internal combustion engine to improve the efficiency and power output of the engine. A turbocharger may generally include a compressor connected to a turbine by an interconnecting shaft. The turbine may extract energy from the flow of exhaust gases to drive the compressor via the interconnecting shaft, while the compressor may increase the pressure of intake air for delivery to the combustion chamber. The compressor may include a radial impeller that accelerates the intake air and expels the air in a radial direction, and a diffuser that slows down the expelled air to cause a pressure rise.

The design of turbocharger compressors is a highly refined art. The shape, curvature, and surface finish of the compressor rotor, compressor housing, and diffuser are designed to produce maximum pressure boost across the desired range of operating conditions. When very high pressure ratios are required, as in the case of large commercial diesel engines, vaned diffusers may be preferred over vaneless diffusers because they provide a higher maximum pressure ratio and increased efficiency, albeit frequently at the cost of a reduced map width, as depicted on a compressor map well known in the art as showing the relationship between pressure ratio and volume or mass flow rate. The vanes of a vaned diffuser define channels into which high velocity gas from the compressor is received, and through which the gas is decelerated in order to convert its kinetic energy into a static pressure. Circumferentially spaced guide vanes provide passages that expand radially in area to diffuse the flow.

While effective, the operating range of turbocharger compressors may be limited to certain mass flow rates and pressure ratios outside of which the compressor may exhibit undesirable choke or surge behavior. In particular, the operating range of a compressor may be characterized by the compressor map of operable mass flow rates and pressure ratios, with right and left boundaries respectively defining the choke and surge lines of the compressor. The choke line defines the maximum mass flow rate of the compressor, and the surge line defines the minimum mass flow rate of the compressor. Compressor surge occurs when the direction of flow through the compressor reverses to relieve pressure at the compressor outlet under low mass flow rate and high pressure ratio conditions. That is, at certain low mass flow rates and high pressure ratios, the flow can no longer adhere to the suction side of the blades, interrupting the discharge process and resulting in a pressure build up at the compressor outlet. The direction of air flow through the compressor may be reversed until a stable pressure ratio is reached, at which point the air flow proceeds in the forward direction again. This flow instability continues within the surge range of the compressor map and produces a noise known as “surging”. Operating the turbocharger in surge for extended periods is undesirable, and may negatively impact the performance of the turbocharger.

In one aspect of the present disclosure, a controlled area progression vaned diffuser for a compressor is disclosed. The compressor may include a bearing housing in which a shaft is supported by a bearing to rotate about a rotational axis, a compressor wheel disposed on the shaft and having a compressor radius, and a compressor housing connected to the bearing housing, defining a chamber within which the compressor wheel rotates and a volute for receiving airflow generated by the compressor wheel. The controlled area progression vaned diffuser may include a bearing diffuser wall of the bearing housing having an annular shape and extending from the chamber to the volute, a compressor diffuser wall of the compressor housing having an annular shape and extending from the chamber to the volute, wherein the bearing diffuser wall and the compressor diffuser wall are spaced apart in an axial direction. The controlled area progression vaned diffuser may further include a plurality of vanes extending from the bearing diffuser wall and the compressor diffuser wall and circumferentially spaced about the rotational axis, each vane have a vane leading edge and a vane trailing edge, a diffuser inlet proximate the chamber, and a diffuser outlet proximate the volute, wherein the airflow from the compressor wheel enters the controlled area progression vaned diffuser through the diffuser inlet, between the bearing diffuser wall and the compressor diffuser wall and past the plurality of vanes, and flows out of the diffuser outlet to the volute. The bearing diffuser wall and the compressor diffuser wall may be spaced apart by a vane leading edge width at the vane leading edge, the bearing diffuser wall and the compressor diffuser wall may define a pinch point between the diffuser inlet and the vane leading edge, wherein pinch point has a pinch point width that is less than the vane leading edge width, and diffuser outlet may have a diffuser outlet width that is less than the vane leading edge width.

Additional aspects are defined by the claims of this patent.

The following description of various embodiments is merely illustrative in nature and is in no way intended to limit the scope of the invention, its application or its uses.

As shown in, an engine airflow systemmay include an internal combustion enginethat may have a number of cylinders for the controlled combustion of fuel to produce power. Exhaust gas generated during combustion may exit the engineat an exhaust manifoldthat may be connected to an exhaust passage. The exhaust passagemay lead to a turbineof a turbocharger. The exhaust gas may be expanded in the turbineand release energy to rotate a turbine wheel. The exhaust gas may continue from the turbinethrough an exhaust passage, an exhaust after treatment deviceand an exhaust throttle valveto an exhaust discharge.

The turbine wheelmay be connected to a compressor wheeldirectly or indirectly by a shaft. The compressor wheelmay be disposed in a compressor. Through the action of routing exhaust gases to rotate the turbine wheel, the compressor wheelmay be correspondingly rotated by the shaft. The rotating compressor wheelmay draw air in through an intake passageand compress the air. Compression of the intake air may charge an intake systemof the enginethrough a passage, a charge air cooler, a passageand intake manifold. An intake throttle valvemay be provided to selectively throttle the passagewhen desired, though the intake throttle valvemay be omitted in embodiments of the engine airflow system.

While controlled area progression vaned diffusers (CAPVDs) according to the present disclosure are illustrated and described herein as being implemented in a turbocharger for an internal combustion engine, those skilled in the art will understand that the CAPVDs may be implemented in any centrifugal compressors used to boost the performance of a power source. For example, the CAPVDs may be implemented in electrically driven boosters that are driven by an electric motor as opposed to a turbine drive by combustion exhaust. Alternatively, CAPVDs may be implemented in fuel cell air supplies for electric vehicles that may or may not include a turbine. Further alternative implementations of CAPVDs according to the present disclosure in centrifugal compressors are contemplated by the inventors. Moreover, while the compressoris described herein as drawing in, compressing and discharging air, compressors in accordance with the present disclosure may be implemented to compress any gas that flows through the process such as, for example, exhaust gas.

An embodiment of a compressorof a turbocharger is illustrated in. The description of the compressormay include references to axial or axially, which is indicated by reference numeraland means a direction along or parallel to a rotational axis A of the shaft. The description may further include references to radial or radially, which is indicated by the reference numeraland means a direction toward or away from the rotational axis A of the shaftin any of the 360 degrees around the shaft. The shaftmay be supported by bearings (not shown) in a bearing housingthat may be disposed between the compressorand the turbine. The compressor wheelmay be disposed in a chamberthat may be defined by the bearing housingand a compressor housing. The compressor wheelmay include a central hubhaving an annular outer edgeand connected to the shaft, and a plurality of circumferentially spaced bladeshaving blade tipsat their radial ends. A compressor inletto the chambermay be defined by the compressor housingthrough which air may be drawn by the compressor wheel. Air may be delivered from the compressor wheelthrough a diffuserand may be collected in a volutefor communication to the passagevia a compressor outlet (not shown). The diffusermay be defined between the bearing housingat a bearing diffuser wall, and the compressor housingat a compressor diffuser wall. A plurality of circumferentially spaced vanesas known in the art may extend between the diffuser walls,to define channels through which high velocity gas flows and is decelerated. The diffusermay form an annular passage extending radially outward from the chamberproximate the blade tipsto the volute. Air drawn in through the compressor inletmay be acted upon in the chamberby the bladesof the compressor wheeland delivered through the diffuserto the volute.

The flow of air leaving the compressor wheel tipenters the adjacent segment of the diffuserwhich may be referred to as a diffuser inlet, and exits the diffuserto the voluteat a diffuser outlet. The diffuser inletis a segment of the diffuserclosest to the compressor wheel, which also has the highest gas flow velocity since the annulus area Aof the diffuseris smaller radially inward, and becomes greater moving radially outward. The annulus area Aof the diffuserat a given radial distance rfrom the axis A of the compressor wheelmay be determined by the following equation:

where wis a width of the diffuserat a given radial distance r. In the compressorof, the diffuserhas a conventional design wherein the diffuser walls,are parallel and the diffuser width wp is constant as the diffuserextends radially from the diffuser inletto the outlet to the volute. Each of the vanesmay start at a vane leading edge (VLE)proximate the diffuser inletand extend through the diffuserto a vane trailing edge (VTE)proximate the diffuser outletand the volute.

presents a graphrepresenting the diffuser annulus area Aversus the diffuser radius rof vaned diffusers. A linerepresents an area progression of the vaned diffuserof the conventional compressoras the diffuser radius rincreases. Initially, the diffuser width wand the corresponding diffuser annulus area Amay decrease from the outer edgeof the compressor wheel hubas the compressor housingconverges toward the compressor blade tipsand the bearing housinguntil reaching the diffuser inlet. After the diffuser inlet, the diffuser width wremains constant and the diffuser walls,remain parallel as the diffuser radius rincreases and the diffuser annulus area Aincreases linearly until the diffuserintersects with the voluteat the diffuser outlet. While the compressoris illustrated and described as having the diffuser inletradially outward from the outer edgeof the huband proximate the blade tips, the diffuser inletmay be defined at any position proximate the compressor wheelthat is relevant to a particular implementation of the diffuser. Regardless of the defined location of the diffuser inlet, the diffuser walls,are parallel with a fixed diffuser width wfrom the diffuser inletto the diffuser outletin conventional compressors.

In the present embodiments, the area progression is controlled by varying the diffuser width was the diffuser extends from the diffuser inletto the volute.illustrates an embodiment of the compressorwherein a CAPVDhas a varying diffuser width created by a compressor diffuser wallthat is contoured relative to the bearing diffuser wall. The outer edgeof the compressor hubdefines a compressor radius rfrom the rotational axis A, and a diffuser inletmay be defined at a diffuser inlet radius rthat is approximately equal to a radial distance to the blade tips. The diffuser inletmay have a diffuser inlet width wbetween the corresponding portions of the diffuser walls,. As the CAPVDextends radially outward from the diffuser inlet, a first compressor diffuser wall portionmay be angled toward the bearing diffuser wallso that the width of the CAPVDdecreases until the compressor diffuser wallreaches a first transition or pinch pointat a pinch point radius rand a pinch point width w. Radially beyond the pinch point, a second compressor diffuser wall portionis angled away from the bearing diffuser wallso that the width of the CAPVDincreases until the compressor diffuser wallreaches a second transition pointat a second transition point radius rwith the diffuser width w. The VLEsof the vanesmay be located at a VLE radius rthat may be equal to the second transition point radius ras shown, or may be greater than the second transition point radius rin alternative implementations.

Radially beyond the second transition point, a third compressor diffuser wall portionmay be parallel to the bearing diffuser wallto maintain the diffuser width wfor at least the radial length of the vanesto a VTE radius r. In some embodiments, the compressor diffuser wallmay continue to extend beyond the VTEsparallel to the bearing diffuser wallto the diffuser outlet. In the illustrated embodiment, however, radially beyond a third transition pointat a third transition point radius r, a fourth compressor diffuser wall portionmay be angled toward the bearing diffuser wallso that the width of the CAPVDdecreases until the compressor diffuser wallreaches a diffuser outletat a diffuser outlet radius rwith a diffuser outlet width w. The third transition point radius rmay be equal to the VTE radius ras shown, or greater than the VTE radius rsuch that the third transition pointis radially outward of the VTEs.

Referring back to, a linerepresents the annulus area progression of the diffuser. As with the linefor the conventional vaned diffuser, the annulus area Amay decrease from the outer edgeof the compressor wheel hubas the compressor housingconverges toward the compressor blade tipsand the bearing housinguntil reaching the diffuser inlet. From the diffuser inletto the pinch point, the annulus area Aincreases at a low rate as the first compressor diffusor portionextends radially as the decreasing diffuser width offsets the increasing radial dimension in Equation (1). After the pinch point, the annulus area Aincreases at a greater rate as both the radius and the diffuser width increase until the second transition pointproximate the VLE. From the second transition pointto the third transition point, the annulus area Aincreases at a lower rate that may be approximately a linear rate as the radius increases and the diffuser width is constant. After the third transition point, the annulus area Amay decrease as shown when the decrease in the diffuser width offsets the increase in the radius as the diffuserextends to the diffuser outlet.

Those skilled in the art will understand that the shape of the linemay change for particular designs of the diffuseras the radial positions of the diffuser inlet, VLE, VTE, points,,and diffuser outletand the various widths are tuned to achieve desired performance characteristics for the design and for the turbochargers or other devices in which compressorswith the diffuserin accordance with the present disclosure are implemented. Table 1 below provides a summary of the parameters discussed above that are relevant to the design of the diffuser:

The first column of Table 1 lists the parameters illustrated inand discussed in the accompanying text, and the second column provides approximate value ranges for each parameter that may provide guidance in designing the diffuserfor a particular application. The value ranges for the parameters may be derived from the compressorin which the diffuseris implemented. For example, the value of the diffuser inlet width wmay be derived from the compressor radius rof the compressor wheeland be within a range of 0.08-0.14 times the compressor radius r. Other values may then be derived from the compressor radius ror the diffuser inlet width w. An exemplary design of the diffusermay have the scaled values shown in the third column that indicate that the parameter values in the exemplary design fall within the values ranges of the respective parameters.

The parameter value ranges of the example design in Table 1 are also exemplary for the CAPVDin accordance with the present disclosure. For example, the value ranges and scaled values of Table 1 show the VLE width wand the VTE width wbeing equal to the diffuser width wD and, consequently, equal to each other such that the diffuser walls,are parallel from the VLEto the VTE. In alternative embodiments, the VLE width wmay be greater than or less than the VTE width wsuch that the portion of the CAPVDfrom the VLEto the VTEis tapered. Further alternative geometries for CAPVDsin accordance with the present disclosure are contemplated.

The CAPVDmay provide improved efficiencies over conventional vaned diffusers such as the diffuser.presents a compressor mapof a compressor pressure ratio (outlet pressure over inlet pressure) versus compressor mass flow. The compressor maprepresents a comparison of simulation data for the operation of the compressorwith the baseline vaned diffuserofand the controlled area progression vaned diffuserofhaving the exemplary parameter values set forth in Table 1. In the compressor map, a choke linedefines a maximum compressor mass flow rate of the compressorwith the diffuserabove which the high flow rate and low compressor pressure ratio may cause the compressorto choke. A surge linefor the diffusermay define the minimum compressor mass flow rate below which the discharge process may be interrupted. Linesmay represent combinations of compressor pressure ratios and corresponding compressor mass flows for various rotational speeds of the compressor wheel.

The data for the diffuserincludes a choke lineto the left of the choke linein this comparison, a surge lineand constant compressor rotational speed lines. As shown by the data, the surge linefor the diffuseris shifted to the left from the surge lineof the diffuserindicating that diffuserwill allow the compressorto operate at lower compressor mass flow rates without encountering surging. The area between the surge lines,represents operating conditions where the geometry of the diffuseris having a meaningful effect to suppress the surge mechanism.

The data further shows that improvements in efficiencies can be achieved by controlled area progression vaned diffusers in accordance with the present disclosure. As shown in the compressor map, improvements in efficiency may be achieved with the diffuserin both choke and surge. The greatest efficiency gains may be realized proximate the choke lines,and the surge lines,of the compressor map.

Controlled area progression vaned diffusers in accordance with the present disclosure may allow compressors of turbochargers to operate more efficiently at low compressor mass flows, and reduce the occurrences of surging during low mass flow conditions. By shaping the compressor diffuser wallto vary the diffuser width wp and control the annulus area progression of the diffuser, separation of air from the diffuser walls,at low mass flows can be suppressed and the amount of separation may be reduced to reduce drag within the diffuserand maintain efficiency of the compressorunder such conditions. Controlled area progression allows controlled pressure in the diffuserthat leads to suppression of separation and instability in the diffuser, which can improve efficiency.

Previously known diffusersprovided two variables for controlling their performance within the compressor: the diffuser width wand the radial length of the diffuser. Controlled area progression vaned diffusersin accordance with the present disclosure provide greater flexibility in tuning the diffuser to improved the efficiency of compressorsby contouring the shape of the compressor diffuser wall. Contouring of the compressor diffuser wallfacilitates reducing annulus area Ain zones where the diffuser flow is unstable and tends to separate. Conversely, the annulus area Amay be increased where the diffuser flow is stabilized by the vanes to reduce flow speeds and friction losses. More stable flow through the diffusercan result in greater efficiency, and the increased efficiency may be achieved while maintaining or expanding the width of the compressor map.

In previously known vaned diffusers, such as the vaned diffuser, the VLEis typically located at approximately 1.1-1.2*rdue to the belief that positioning the vanesproximate the compressor wheelachieves optimum efficiency. In contrast, the VLEin the present design of the vaned diffusercan be positioned in the range from 1.3-1.4 rdue to the pinch pointstabilizing the fluid flow proximate the diffuser inlet. With the vanespositioned further from the compressor wheel, efficiency may be maintained while potentially reducing vibration and high cycle fatigue (HCF) on the compressor blades.

While the preceding text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of protection is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the scope of protection.

It should also be understood that, unless a term was expressly defined herein, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning.