METHOD OF IMPROVING EXHAUST EMISSION OF A COMBUSTION ENGINE, AND COMBUSTION ENGINE

Abstract

In a method of reducing pollutants of a combustion engine, exhaust gas, generated by a cylinder of the combustion engine, is fed to an exhaust gas aftertreatment system as a function of a predefined condition solely via a first exhaust channel which communicates with a first one of first and second exhaust valves of the cylinder. The first exhaust channel is hereby coated, at least in part, by a thermally insulating layer selected such that a heat input is transmitted to the exhaust gas aftertreatment system which heat input is greater than a heat input in a second exhaust channel communicating with a second one of the first and second exhaust valves. The predefined condition is defined as a function of a coolant temperature of the combustion engine.

Claims

1. A method of reducing pollutants of a combustion engine, said method comprising: feeding exhaust gas, generated by a cylinder of the combustion engine, to an exhaust gas aftertreatment system as a function of a predefined condition solely via a first exhaust channel which communicates with a first one of first and second exhaust valves of the cylinder and is coated, at least in part, by a thermally insulating layer selected such that a heat input is transmitted to the exhaust gas aftertreatment system which heat input is greater than a heat input in a second exhaust channel communicating with a second one of the first and second exhaust valves; and defining the predefined condition as a function of a coolant temperature of the combustion engine.

2. The method of claim 1, wherein the second exhaust channel is configured in the absence of an insulating layer.

3. The method of claim 1, further comprising discharging exhaust gas from the cylinder at least in part via the second one of the first and second exhaust valves and the second exhaust channel as a function of a further predefined condition.

4. The method of claim 1, wherein the first exhaust channel is configured such that the heat input from the cylinder into the exhaust gas aftertreatment system is at a maximum.

5. A combustion engine, comprising: a cylinder having first and second exhaust valves; an exhaust gas aftertreatment system receiving exhaust gas from the cylinder as a function of a predefined condition solely via a first exhaust channel which communicates with a first one of first and second exhaust valves of the cylinder; and a thermally insulating layer applied on the first exhaust channel and selected such that a heat input is transmitted to the exhaust gas aftertreatment system which heat input is greater than a heat input in a second exhaust channel communicating with a second one of the first and second exhaust valves, said predefined condition being defined as a function of a coolant temperature of the combustion engine.

6. The combustion engine of claim 5, further comprising a control device configured to control the first and second exhaust valves such that as a function of the predefined condition the first exhaust valve opens to allow exhaust gas, generated by the cylinder, to flow to the exhaust gas aftertreatment system via the first exhaust channel.

7. The combustion engine of claim 6, further comprising first and second turbochargers, said control device being configured to operate the first exhaust valve such that during a cold start phase of the combustion engine exhaust gas flows in the first exhaust channel to the exhaust gas aftertreatment system via the first turbocharger only.

8. The combustion engine of claim 5, wherein the thermally insulating layer is applied upon an inner surface of the first exhaust channel.

9. The combustion engine of claim 5, wherein the thermally insulating layer is applied upon an outer surface of the first exhaust channel.

10. The combustion engine of claim 5, constructed in the form of a diesel engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0025] Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which the sole FIG. 1 shows a schematic illustration of an exemplified embodiment of a combustion engine according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] The depicted embodiment is to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figure may not necessarily be to scale. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

[0027] Turning now to FIG. 1, there is shown a schematic illustration of an exemplified embodiment of a combustion engine according to the present invention. The combustion engine, e.g. a diesel engine, is shown here only to the extent that is necessary for the understanding of the present invention. It will be appreciated by persons skilled in the art that the combustion engine must contain much mechanical apparatus which does not appear in the foregoing Figure. However, this apparatus, like much other necessary apparatus, is not part of the invention, and has been omitted from FIG. 1 for the sake of simplicity.

[0028] FIG. 1 shows a cylinder 1 of the combustion engine. Arranged in the cylinder 1 are a piston 3 as well as a first exhaust valve 5 and a second exhaust valve 7. In order to subject exhausts, produced in the cylinder 1 during operation of the combustion engine, to an aftertreatment as rapidly and efficiently as possible, an exhaust gas aftertreatment system 9 has to be brought to operating temperature as rapidly as possible after stating the combustion engine. For this purpose, provision is made to maximize a heat input by exhausts into the exhaust gas aftertreatment system 9 by only opening the exhaust valve 5 to allow a flow of exhaust gas to exit the cylinder 1 exclusively via an exhaust channel 11 which is associated to the exhaust valve 5. On its way to the exhaust gas aftertreatment system 9, exhausts flow initially to a turbocharger 13 and then to the exhaust gas aftertreatment system 9 for a time period long enough for the temperature in the exhaust gas aftertreatment system 9 to reach a desired predefined temperature.

[0029] The exhaust channel 11 has in its interior, i.e. on an inner side 15, a thermal insulating layer 17 which minimizes or even prevents a transfer of heat energy from exhaust gas within the exhaust channel 11, i.e. from the exhaust gas to a material delimiting the exhaust channel 11. Thus, heat energy in the exhaust retained in the exhaust gas and can be used for heating the exhaust gas aftertreatment system 9. The insulating layer 17 may be a layer of enamel which exhibits extremely poor heat conduction. An example of an enamel layer is known under the designation NemaCoat, distributed by Nemak Europe GmbH. It is, of course, also conceivable that the insulating layer 17 includes ceramic insets, so-called portliners.

[0030] As soon as the exhaust gas aftertreatment system 9 has reached operating temperature, the second exhaust valve 7 can be activated to open in order to allow exhaust to also exit the cylinder 1 and to flow in a second exhaust channel 19 for operation of a turbocharger 21 which is in communication with the exhaust channel 19. In this way, the combustion engine can be operated efficiently and at high performance. The heating phase, during which an input of heat energy into the exhaust gas aftertreatment system 9 takes place, is coupled to an operating mode of a control of the first exhaust valve 5 and the second exhaust valve 7, which control in turn can be controlled as a function of a current coolant temperature for example.

[0031] While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

[0032] What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: