Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-12-10
2001-04-17
Koczo, Michael (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S602000
Reexamination Certificate
active
06216459
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention resides in an arrangement for the recirculation of exhaust gases in an internal combustion engine.
In order to achieve the lowest possible emission limits, particularly in connection with internal combustion engines for commercial vehicles, exhaust gas re-circulation concepts are being developed by which the NOx emissions are reduced without essential increases in the fuel consumption. It is known for example, from DE 43 30 487 C1 and DE 43 03 521 C1 to provide a turbocharger, for this purpose with an exhaust gas turbine which includes a variable geometry such as an adjustable flow guide structure, rotatable guide vanes, axially movable flow guide rings or similar devices. By changing the geometry of the exhaust gas turbine, for example, by closing the turbine flow guide structure, a turbine inlet pressures p
3
which is larger than the charge air pressure P
2
can be obtained over a large operating range up to full engine power. As a result, the exhaust gas can be re-circulated from a point of the exhaust pipe upstream of the turbine to the charge air duct downstream of a charge air cooler (inter-cooler) ahead of the engine without reducing the air/fuel ratio which would affect the fuel consumption.
There are however problems since during full load operation the cylinder pressure limit and also a compression pressure limit of the exhaust gas turbocharger must be observed, whereby exhaust gas re-circulation may be prevented or is at least limited. These limits can be overcome in known arrangements only by additional measures, which affect the overall efficiency of the gas exchange. Additional measures are disclosed, for example, in DE 4 429 232 C1, wherein variable ejectors serving as flow control apparatus, which are arranged in the charge air duct, are disclosed. Also, supplemental compressors for the compression of exhaust gas are known for example from DE 43 12 078 C2.
Using adjustable guide vanes, it is possible to form, during engine braking operation, a so-called turbo-brake wherein the turbine guide vanes structure is adjusted to a very small flow cross-section. As a result, the internal combustion engine is highly charged whereby a very high engine braking power can be obtained.
However, actual tests have shown that the long life expected from engines, and in particular from commercial internal combustion engines, cannot be achieved with the measures known so far.
DE OS 28 55 687 discloses an asymmetrical two-flow exhaust gas turbine, wherein the two spiral inlet flow passages, which are separated by a separating wall, are different in size. With the asymmetrical separation, it is said that the pressure ahead of the smaller inlet flow passage is higher than in the charge air duct so that exhaust gas re-circulation is made possible. In order to insure sufficient exhaust gas re-circulation also with high charge air pressures a large difference in flow cross-section between the two flow passages must be provided which detrimentally affects the turbine efficiency, and generally the charge air exchange efficiency of the engine.
It is the object of the present invention to provide an exhaust gas re-circulation arrangement for a supercharged internal combustion engine, which permits exhaust gas recirculation for the various operating states of the engine without expensive supplemental measures.
SUMMARY OF THE INVENTION
In an exhaust gas re-circulation arrangement for a supercharged internal combustion engine including an exhaust gas turbocharger with an exhaust gas turbine and a compressor, first and second exhaust pipes extending from the engine separately to the exhaust gas turbine, a charge air duct extending from the compressor to the engine and an exhaust gas recirculation line extending from one of the exhaust pipes upstream of the exhaust gas turbine to the charge air duct downstream of the compressor, the exhaust gas turbine has two turbine inlet flow passages, which provide for different flow volumes and to each of which one of the exhaust pipes is connected and a control arrangement is provided for controlling the exhaust gas flow through the turbine inlet flow passages so as to control the pressure in the exhaust gas re-circulation line to be higher than in the charge air intake duct.
With the different inlet flow passages in combination with a variable geometry of the exhaust gas turbine, for example, a variable guide vane arrangement, the pressure of the recirculated gas can be controlled by a control unit in such a way that, when necessary, it is higher than the pressure of the charge air. As a result, exhaust gas re-circulation can always be accomplished. At the same time, it can be prevented by a particular control scheme, that problems arise during full load operation.
In addition to being used as a turbo-brake, the variable geometry may be formed for example by a vane ring structure, which is slideable into one or both of the flow channels. It can be used to control the pressure in the exhaust pipe recirculation line upstream of the exhaust gas turbine and, consequently, also in the exhaust gas re-circulation flow.
If, for example, an as high as possible variability with a relatively high asymmetry of the flow channels is selected, the exhaust pipe, in accordance with a particular embodiment of the invention, may include a pressure release or gas redirecting arrangement by way of which exhaust gas can flow from one to the other of the turbine gas inlet passages or it can be blown off.
In this way, the turbo braking power can be limited and/or the exhaust gas re-circulation volume and the exhaust gas pressure can be controlled.
Since the turbine efficiency drops with increasing asymmetry also the asymmetry may be limited and a pressure control device may be provided in the charge air duct, for example in the form of a variable ejector. It is also possible to provide a supplemental compressor or a second exhaust gas turbocharger, which is arranged in parallel with the first turbocharger.
Instead of, or in addition to, differently sized turbine inlet passages, the inlet passages may have the same size, but a restriction may be arranged in the exit area of one of the passages. Such restriction may be provided for example by an adjustable guide vane structure, which causes a desired pressure build-up in one of the passages.
Below, two embodiments of the invention will be described in greater detail on the basis of the accompanying drawings.
REFERENCES:
patent: 4179892 (1979-12-01), Heydrich
patent: 5611202 (1997-03-01), Sumser et al.
patent: 5791146 (1998-08-01), Dungner
patent: 5794445 (1998-08-01), Dungner
patent: 5855117 (1999-01-01), Sumser et al.
patent: 5943864 (1999-08-01), Sumser et al.
patent: 28 55 687 (1979-06-01), None
patent: 43 03 521 (1994-01-01), None
patent: 43 30 487 (1995-01-01), None
patent: 43 12 078 (1995-06-01), None
patent: 44 29 232 (1995-09-01), None
patent: 196 03 591 (1997-03-01), None
Daudel Helmut
Finger Helmut
Schmidt Erwin
Sumser Siegfried
Bach Klaus J.
Daimler-Chrysler AG
Koczo Michael
LandOfFree
Exhaust gas re-circulation arrangement does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Exhaust gas re-circulation arrangement, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Exhaust gas re-circulation arrangement will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2466805