Patent Application
20170191490
This patent disclosure relates generally to turbochargers for use with internal combustion engines and, more particularly, to impellers for centrifugal compressors used as part of turbochargers for use with internal combustion engines.
Internal combustion engines are supplied with a mixture of air and fuel for combustion within the engine that generates mechanical power. To maximize the power generated by this combustion process, the engine is often equipped with a turbocharged air induction system.
A turbocharged air induction system includes a turbocharger that uses exhaust from the engine to compress air flowing into the engine, thereby forcing more air into a combustion chamber of the engine than the engine could otherwise draw into the combustion chamber. This increased supply of air allows for increased fuelling, resulting in an increased engine power output.
The fuel energy conversion efficiency of an engine may depend on many factors, including the efficiency of the engine's turbocharger. Turbocharger efficiency can be affected by the structures at the turbine operating to extract energy from the exhaust gas, as well as the structures at the compressor operating to use the extracted energy to compress air that is provided to the engine cylinders.
Various past attempts have been made to increase the efficiency of turbochargers by improving, in part, the operating efficiency of the compressor by adjusting design features of the compressor's impeller. One example of a compressor impeller can be found in DE102009007843A1 (the '843 reference), which describes a compressor wheel having a set of split blades arranged between two consecutive complete blades. As show in the '843 reference, for example, in
The disclosure describes, in one aspect, a turbocharger for use with an internal combustion engine. The turbocharger includes a turbine housing surrounding a rotatable turbine wheel that is connected to a shaft. A center housing includes a bearing arrangement that rotatably supports the shaft, which shaft extends through the center housing. A compressor housing surrounds an end of the shaft, and a compressor wheel is connected to the end of the shaft and is rotatably disposed within the compressor housing. The compressor wheel includes a central hub having a centerline, a root portion and an end portion. The root portion is adjacent to a connection between the compressor wheel and the end of the shaft.
In one embodiment, a first plurality of blades is formed around the central hub such that each of the first plurality of blades extends from the root portion to a first area adjacent the end portion along the centerline. A second plurality of blades is formed around the central hub. Each of the second plurality of blades is disposed between adjacent blades from the first plurality of blades and extends from the root portion of the hub to a second area along the centerline, which is shorter than the first area with respect to the centerline. A third plurality of blades is formed around the central hub such that each of the third plurality of blades is disposed along the central hub between adjacent blades from the first plurality of blades and from the second plurality of blades. Each of the third plurality of blades extends from the root portion of the hub to a third area along the centerline, where the third area is shorter than the second area with respect to the centerline.
Accordingly, the compressor wheel includes a plurality of sets of blades, each set of blades including a blade from each of the first, second and third pluralities of blades arranged in order such that, at any radial location around the compressor wheel during operation, a blade from the first plurality of blades is followed by a blade from the second plurality of blades, and a blade from the second plurality of blades is followed by a blade from the third plurality of blades.
This disclosure relates to an improved turbocharger configuration for use with an internal combustion engine. More particularly, the disclosure relates to an improved compressor in which a compressor wheel, which can also be referred to as a compressor impeller, that is of a centrifugal compressor type that is arranged with blades of different lengths to increase compressor efficiency and decrease compressor transient response time, thus increasing engine performance.
A simplified, exemplary block diagram of an engine 100 is shown in
Rotation of the shaft 126 causes a compressor wheel (not shown here) of a compressor 136 to rotate. As shown, the compressor 136 is a radial compressor configured to receive a flow of fresh, filtered air from an air filter 138 through a compressor inlet 140. Pressurized air at an outlet 142 of the compressor 136 is routed via a charge air conduit 144 to a charge air cooler 146 before being provided to an intake manifold 148 of the engine 100. In the illustrated embodiment, air from the intake manifold 148 is routed to the combustion cylinders 106 where it is mixed with fuel and combusted to produce engine power.
An EGR system 102, which is optional, includes an EGR cooler 150, which is also optional, that is fluidly connected to an EGR gas supply port 152 of the exhaust conduit 108. A flow of exhaust gas from the exhaust conduit 108 can pass through the EGR cooler 150 where it is cooled before being supplied to an EGR valve 154 via an EGR conduit 156. The EGR valve 154 may be electronically controlled and configured to meter or control the flow rate of the gas passing through the EGR conduit 156. An outlet of the EGR valve 154 is fluidly connected to the intake manifold 148 such that exhaust gas from the EGR conduit 156 may mix with compressed air from the charge air cooler 146 within the intake manifold 148 of the engine 100.
The pressure of exhaust gas at the exhaust conduit 108, which is commonly referred to as back pressure, is higher than ambient pressure, in part, because of the flow restriction presented by the turbine 120. The pressure of the air or the air/EGR gas mixture in the intake manifold 148, which is commonly referred to as boost pressure, is also higher than ambient because of the compression provided by the compressor 136. In large part, the pressure difference between back pressure and boost pressure, coupled with the flow restriction and flow area of the components of the EGR system 102, determine the maximum flow rate of EGR gas that may be achieved at various engine operating conditions.
An outline view of the turbocharger 119 is shown in
The compressor 136 includes a compressor vane ring 274 that has vanes 276 disposed radially around the compressor wheel 213. The vanes 276 fluidly connect a compressor inlet bore 278, which contains the compressor wheel 213, with a compressor scroll passage 280 that is formed in the compressor housing 217 and that terminates to a compressor outlet opening 282. Bolts 284 and circular plate segments 286 connect the compressor housing 217 to a compressor mounting plate 268.
An outline view of the compressor rotor or compressor wheel 213 is shown from a front perspective in
Various blades 308 are formed around and along the central hub 302. The blades 308 operate to redirect air entering the compressor towards the compressor outlet while also compressing the air. In the illustrated embodiment, three different types of blades 308 are shown formed on the compressor wheel 213. Specifically, the compressor wheel 213 includes a first plurality of blades 310, a second plurality of blades 312 and a third plurality of blades 314. Each blade in the first, second and third pluralities of blades 310, 312 and 314 operate to redirect air towards the compressor outlet, and/or split air streams passing over and around the compressor wheel to increase compressor efficiency.
More specifically, each of the first plurality of blades 310 is a full-size blade, compared to the remaining blades 308, meaning, that the full-size blade extends from a root area 316 of the central hub 302 up to an area adjacent the free end 304, as shown in
Each of the second plurality of blades 312, which can be referred to as a half-blade, is shorter than a full-size blade, which means that each of the second plurality of blades 312 extends from the root area 316 of the central hub 302 up to an area that is closer to the root diameter 322 than the leading edges 318 of the first plurality of blades 310. Each of the second plurality of blades 312 includes a leading edge 324 that forms a tip 326, which is disposed at a second distance, X2, from the root diameter 322 of the central hub 302, as shown in
Similar to the second plurality of blades 312, each of the third plurality of blades 314, which can be referred to as a partial-blade, is shorter than a full-size blade, which means that each of the third plurality of blades 314 extends from the root area 316 of the central hub 302 up to an area that is closer to the root diameter 322 than the leading edges 318 of the first plurality of blades 310 and also the leading edges 324 of the second plurality of blades 312. Each of the third plurality of blades 314 includes a leading edge 328 that forms a tip 330, which is disposed at a third distance, X3, from the root diameter 322 of the central hub 302, as shown in
As can be seen in
Moreover, different ratios of the lengths X1, X2 and X3 can be used. In the illustrated embodiment, X1 is selected such that X1 is equal to about 1.6 times X2 and about 2.2 times X3. Stated differently, for the illustrated embodiment, X2≈0.62*X1, or 62% of X1, but it can be anywhere in the range between 55% and 70% of X1. Similarly, X3≈0.46*X1, or 46% of X1, but it can be anywhere in the range between 40% and 55%. Based on this relations, it can be appreciated that X2≈1.36*X3, or X3≈0.73*X2, or about 73% of X2, but it can be anywhere in the range between 65% and 80%.
At the root of the wheel, the blades are arranged such that, in a rotation direction, R, as denoted in the figure, a blade from the first plurality of blades 310 is follows a blade from the second plurality of blades 312, and then the two are follow a blade from the third plurality of blades 314 for any radial location of the compressor wheel 213 as the compressor wheel 213 rotates. However, close to the free end 304, the blades are arranged differently such that the leading edge 328 of a blade from the third plurality of blades 314 follows the leading edge 318 of a blade from the first plurality of blades 310, and then the leading edge 324 of a blade from the second plurality of blades 312 follows.
These arrangements are shown in
The present disclosure is applicable to radial turbocharger compressors for internal combustion engines, but can also be applied to other types of compressors having rotating blades. In the embodiments shown herein, a compressor having a compressor wheel or impeller having three separate sets of blades at different lengths and shapes was unexpectedly found to improve compressor and turbocharger efficiency, for example, in terms of pressure ratio across the compressor and in terms of temperature entropy efficiency.
A qualitative chart showing two pressure ratio maps for a baseline compressor and a compressor having a compressor wheel in accordance with the present disclosure is shown in
A qualitative chart showing compressor efficiency for a baseline compressor and the compressor having a compressor wheel in accordance with the present disclosure is shown in
The second family of curves 416, shown in dashed lines, represents the performance curves with respect to corrected mass flow of the compressor in accordance with the disclosure. As can be seen from the graph in
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
