Patent Application
20190330995
The present disclosure relates to turbochargers in which a turbine of the turbocharger is driven by exhaust gas from a reciprocating engine. The invention relates more particularly to turbine housings that are divided into a plurality of substantially separate sections each fed by a separate exhaust system.
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.
In multiple-piston reciprocating engines, it is known to design the exhaust system in such a manner as to take advantage of the pressure pulsation that occurs in the exhaust stream. In particular, it is known to employ what is known as “pulse separation” wherein the cylinders of the engine are divided into a plurality of subgroups, and the pulses from each subgroup of cylinders are substantially isolated from those of the other subgroups by having independent exhaust passages for each subgroup. To take best advantage of pulse separation, it is desired to minimize the communication or “cross talk” between the separate groups of cylinders. Accordingly, in the case of a turbocharged engine, it is advantageous to maintain separate exhaust passages all the way into the turbine of the turbocharger. Thus, the turbine housing into which the exhaust gases are fed is typically divided into a plurality of substantially separate parts.
There are two basic ways in which turbine housings have been divided: (1) meridional division, and (2) sector division. In a meridionally divided turbine housing, the scroll or chamber that surrounds the turbine wheel and into which the exhaust gases are fed is divided into a plurality of passages in the meridional plane such that each passage occupies substantially a full circumference and the passages succeed each other in the axial direction, such as shown in FIG. 4 of U.S. Pat. No. 4,027,994.
In a sector-divided turbine housing, the generally annular chamber is divided into angular sectors each of which occupies only a part of the circumference such that the passages succeed each other in the circumferential direction, such as shown in FIG. 2 of U.S. Pat. No. 6,260,358.
The present disclosure relates to turbochargers having turbine housings of either the sector-divided or the meridionally divided type.
The present disclosure describes embodiments of a turbocharger that is selectively configurable in either a single-scroll or twin-scroll configuration, by either preventing or allowing cross-scroll communication between the two scrolls. The mechanism for switching between these configurations comprises a control valve.
In one embodiment described herein, a turbocharger comprises a compressor wheel mounted within a compressor housing, a turbine housing defining a bore extending along a longitudinal axis and defining a divided volute comprising first and second scrolls for receiving exhaust gas, and a turbine wheel disposed in the turbine housing, the turbine housing further defining a first exhaust gas conduit and a second gas conduit that are separated from each other. The first and second exhaust gas conduits respectively feed exhaust gas into the first and second scrolls. The first exhaust gas conduit has a first entrance section that leads into a first feed section that feeds exhaust gas into the first scroll, and the second exhaust gas conduit has a second entrance section that leads into a second feed section that feeds exhaust gas into the second scroll. The first and second entrance sections converge upon each other with an acute angle therebetween, and the first and second feed sections extend parallel to each other and to a flow axis along which exhaust gas flows through the feed sections.
The turbine housing defines a cross-communication opening connecting the first and second entrance sections to each other. The turbocharger includes a cross-scroll communication control valve comprising a valve member disposed in the cross-communication opening. The valve member tapers along the flow direction, such that it has a shape that may be described as arrowhead-shaped. The valve member is rotatable about a valve axis between a first position and a second position, and the valve axis is parallel to the flow axis. The valve member defines walls that close the cross-communication opening in the first position of the valve member such that the first and second exhaust gas conduits are isolated from each other. The valve member defines a through-passage that establishes fluid communication across the cross-communication opening in the second position of the valve member such that fluid communication occurs between the first and second exhaust gas conduits.
Having thus described the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present disclosure 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 present invention is shown in
The turbocharger also includes a turbine housing 24 that houses the turbine wheel 22. As previously noted, in reciprocating internal combustion engines having a plurality of cylinders, it is advantageous to design the exhaust system in such a manner as to take advantage of the pressure pulsation that occurs in the exhaust streams discharged from the cylinders. In particular, it is advantageous to employ what is known as “pulse separation” wherein the cylinders of the engine are divided into a plurality of subgroups, and the pulses from each subgroup of cylinders are substantially isolated from those of the other subgroups by having independent exhaust passages for each subgroup. To take best advantage of pulse separation, it is desired to minimize the communication or “cross talk” between the separate groups of cylinders. In the case of a turbocharged engine, it is advantageous to maintain separate exhaust passages all the way into the turbine of the turbocharger. To this end, the turbine housing typically has a divided scroll, comprising two separate scrolls that respectively receive separate streams of exhaust gas. As previously noted, the scroll can be divided either meridionally or by angular sectors. For the present invention, it is not important which scroll division approach is employed, as the invention is applicable to either one.
In the illustrated embodiment, the scroll or volute 26 of the turbine housing is sector-divided. Although not visible in the drawings, the scroll 26 is divided into two sectors that extend about 180 degrees in the circumferential direction about the turbine wheel. The two sectors are fed with two separate streams of exhaust gas that come into the turbine housing through a first exhaust gas conduit 25a and a second exhaust gas conduit 25b defined by the turbine housing. With reference to
With reference to
With reference to
The valve member 60 is rotatable between a first position shown in
Based on the above description of the valve member, it will be understood that when the valve member 60 is in the first position shown in
When the lever arm of the actuator (not shown) attached to the valve member 60 is rotated to move the valve member to the second position shown in
The cross-scroll communication control valve 50 can be placed in either the first position or the second position based on a determination of the current operating condition of the engine and turbocharger. Generally, it is advantageous to preserve isolation between the two separate streams of exhaust gas within the turbine housing at operating conditions in which the energy in the exhaust gas stream is relatively low, i.e., at low engine speeds where exhaust gas flow rates are low. At these low-end operating conditions, the valve member can be placed in the first position to isolate the two exhaust gas conduits 25a and 25b from each other. Preserving the pulse-separation effect is beneficial for turbine efficiency at those low-end operating conditions.
At operating conditions having high exhaust gas energy (i.e., high engine speeds where exhaust gas flow rates are high), pulse isolation penalizes engine performance (specifically, maximum power output or specific consumption). Accordingly, at these high-end operating conditions, the valve can be placed in the second position to allow both streams of exhaust gas to use the full volume of the turbine housing scroll, thereby mitigating the engine performance penalty.
The valve 50 can also be placed in any of various partially open positions, intermediate between the closed (first) position and the open (second) position. For example, a plurality of partially open positions at 10% open, 20% open, 30% open, 40% open, 50% open, etc., can be established, in which the valve can be placed. By partially opening the valve to various degrees, the flow rate of exhaust gas to the turbine wheel can be regulated, so that the turbine can be made to perform like a variable-flow turbine.
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. The invention is illustrated and described in connection with a radial-inflow turbine, but the invention is not limited to any particular turbine type, and can be used with axial-inflow turbines, mixed radial-axial-inflow turbines, clipped turbine wheels, etc. 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.
