Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2000-05-23
2001-09-11
Solis, Erick (Department: 3747)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S624000, C123S568120, C123S559200, C123S568200, C123S568210
Reexamination Certificate
active
06286312
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus for an internal combustion engine. More particularly, the present invention relates to reducing harmful emissions from a diesel engine provided with a system for recirculation of exhaust gases to the intake of the engine, a so called EGR system (“Exhaust Gas Recirculation”). The present invention also relates to a method for use in an internal combustion engine.
BACKGROUND OF THE INVENTION
In connection with load-carrying vehicles powered by a diesel engine, there exists a general need for reducing, as much as possible, the emission of harmful pollutants from the engine exhaust gases. These emissions are primarily nitrogen oxide compounds (NO
x
), carbon monoxide (CO) and hydrocarbons (HC). In order to reduce these emissions, various measures can be taken. For example, it is known that the design of the combustion chamber in the engine cylinder and the process of injecting the engine fuel can be adjusted so as to minimize these emissions. In those cases where the engine is equipped with a turbocharger, the emission of NO
x
compounds may be reduced by cooling the air fed into the engine (known as “intercooling”).
In connection with gasoline driven engines, the exhaust gases are normally purified by means of a catalytic converter located in the exhaust system. Because a diesel engine is operated with an air surplus, however, the three-way catalyst cannot be used for the reduction of NO
x
compounds from a diesel engine.
Due to increasing environmental requirements and the expected demands of future legislation, the need for reducing the emissions, primarily of NO
x
compounds, from diesel engines has grown ever stronger. In this context, it is known that the amount of NO
x
compounds from a diesel engine can be reduced by equipping it with something known as an EGR system (Exhaust Gas Recirculation), by means of which a certain amount of exhaust gases can be returned from the engine exhaust to its intake. The amount of NO
x
compounds generated in a diesel engine is principally exponentially proportional to the temperature inside the combustion chamber, and, by using an EGR system, the local temperature during combustion can be lowered by dilution with exhaust gases (CO
2
and H
2
O). This in turn leads to less creation of NO
x
.
A diesel engine may be provided with an EGR system by connecting a separate line between the ordinary exhaust outlet of the engine and a point close to the fresh air intake of the engine. In this line, a controllable valve can be arranged, which is also connected to a control unit. In dependence of the existing engine operating conditions, particularly its rotational speed and load, the control unit will determine the degree of opening of the valve, i.e. the amount of EGR gases to be recirculated to the engine air intake. A certain amount of EGR gases will then be fed from the engine exhaust side to its intake side, by means of the fact that the exhaust side pressure is normally higher than the intake side pressure, thus creating a natural “propulsion pressure” for the EGR gases.
In those cases where a diesel engine having an EGR system is utilized together with a turbocharger unit, a problem will thus be created by the fact that for most of the operating points, a higher pressure exists after the turbocharger compressor (i.e. at the point of the engine intake manifold where the incoming fresh air is fed to the engine) than at the engine exhaust outlet. This, in turn, means that a recirculation of EGR gases will not be possible, as there will not be any natural propulsion pressure from the engine exhaust to its intake side. In this manner, no EGR gas flow can be injected into the engine.
In accordance with the prior art, this problem can be solved by providing the turbocharger with variable turbine geometry. One arrangement using this solution is shown in Japanese Patent Application No. 08270454 A, disclosing a diesel engine having a turbocharger comprising adjustable guide vanes, which, depending on the engine operating conditions, can be adjusted to a certain position by means of a control unit. In this way, a sufficiently high pressure can be created on the engine exhaust side whereby a required amount of EGR gases can be recirculated to the intake side.
A substantial disadvantage of this known apparatus relates to the fact that it will entail an impaired gas exchange in the engine. Consequently, there is a need for engine arrangements providing a flow of EGR gases without impaired gas exchange in a diesel engine equipped with a turbocharger.
An object of the present invention is to provide an improved arrangement for an internal combustion engine, particularly a diesel engine equipped with an EGR system and a turbocharger, and providing an adequate propulsion pressure for the EGR gases, so as to achieve a reduction of the NO
x
emissions of the engine.
SUMMARY OF THE INVENTION
In accordance with the present invention, this and other objects have now been realized by the invention of an internal combustion engine comprising a crankshaft and at least one cylinder, an intake line for supplying air to the at least one cylinder, an exhaust line for discharging exhaust gases from the at least one cylinder, a recirculation line for recirculating at least a portion of the exhaust gases from the exhaust line to the intake line for reducing emissions from the internal combustion engine, a valve disposed in the recirculation line for controlling the flow of the at least a portion of the exhaust gases therethrough, a turbocharger associated with the exhaust line including a first turbocharger unit for absorbing energy from the exhaust gases and including compressing means for compressing air supplied to the intake line, and a second turbocharger unit disposed downstream of the first turbocharger unit for absorbing energy from the exhaust gases, whereby a pressure is created in the exhaust line which is greater than the pressure in the intake line, and power transmission means for transmitting power from the second turbocharger unit to the crankshaft. Preferably, the internal combustion engine comprises a diesel engine.
In accordance with one embodiment of the internal combustion engine of the present invention, the engine includes a cooler associated with the recirculation line for cooling the exhaust gases recirculated to the intake line.
In accordance with another embodiment of the internal combustion engine of the present invention, the first turbocharger unit and the second turbocharger unit comprise turbines powered by the exhaust gases.
In accordance with another embodiment of the internal combustion engine of the present invention, the valve comprises an electronically controlled valve, whereby the valve can be continuously controlled between an open condition and a closed condition.
In accordance with another embodiment of the internal combustion engine of the present invention, the valve comprises a first valve, and the engine includes a second valve disposed in the recirculation line, whereby each of the first and second valves can control the flow of the at least a portion of the exhaust gases therethrough, the first and second valves being independently controllable, whereby a plurality of valve positions can be obtained in a stepwise manner.
In accordance with another embodiment of the internal combustion engine of the present invention, the recirculation line is connected to the exhaust line at a point upstream of the first turbocharger unit.
In accordance with another embodiment of the internal combustion engine of the present invention, the at least one cylinder includes a pair of intake valves for supplying air thereto.
In accordance with the present invention, a method has also been discovered for reducing emissions from an internal combustion engine including a crankshaft, at least one cylinder, an exhaust line, and an air intake line, the method comprising absorbing energy from the exhaust gases created by the internal combustion engine at a first location in the exhaust lin
Lerner David Littenberg Krumholz & Mentlik LLP
Solis Erick
Volvo Lastvagnar AB
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