GB2357047A

GB2357047A - Exhaust gas purification system

Info

Publication number: GB2357047A
Application number: GB9929247A
Authority: GB
Inventors: Michael Deacon; David Arthur Ketcher; Michael James Watts
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 1999-12-11
Filing date: 1999-12-11
Publication date: 2001-06-13
Anticipated expiration: 2019-12-11
Also published as: GB9929247D0; GB2357047B

Abstract

An exhaust gas purification system is provided for treating exhaust gas from the diesel engine 10 of a motor vehicle. A plurality of fuel injectors 26 for injecting fuel into the combustion chambers of the engine 10 are connected together by a common fuel line 24, which is fed by a fuel pump 22. An additional fuel injector 30 also connected to the common fuel line 24 is provided on the engine exhaust line 14, for injecting fuel therein, upstream of a catalytic converter 19. The fuel injected into the exhaust 14 flows into the catalytic converter 19 where it reacts with harmful components of the exhaust gas in order to neutralise those components. Because the additional injector is connected to the common fuel line 24, it is fed with fuel at a continuously high pressure.

Description

2357047 Exhaust Gas Purification System The present invention relates to

an exhaust gas purification system for treating exhaust gas from the internal combustion engine of a motor vehicle. The invention is particularly but not exclusively suitable for use with a diesel engine.

To reduce the detrimental effect of motor vehicle exhaust gases on the environment, it is now standard practice to include a catalytic converter in the exhaust line of the vehicle in order to cause harmful or toxic components of the exhaust gas to react and form less harmful gases.

is one particularly harmful gas is nitrogen oxide (NOx). To reduce the concentration of NOx in the exhaust gas, it is known from patent document GB 2316339A for example to introduce fuel into the exhaust line, upstream of the catalytic converter. The fuel acts as a reducing agent and in the presence of the catalyst, reduces the NOx to nitrogen, which is a harmless gas. In GB 2316339A, the fuel is introduced into the exhaust line by a fuel injector fed from a low pressure output of a fuel pump (rather than an output for feeding fuel to the engine).

However because the fuel pressure is not high enough to atomise the fuel sufficiently finely, an electric heater is used so that the fuel is in a gaseous state when it mixes with the exhaust gas. The use of such a heater may introduce a considerable drain on the electrical current supply of the vehicle.

It is an object of this inventions to address the above issues.

990862gb.doc 07 December 1999 2 According to a f irst aspect of the invention, there is provided an exhaust gas purification system for an internal combustion engine characterised in that it comprises: a fuel pump; a plurality of main fuel injectors for injecting fuel into the combustion chambers of an engine; a common fuel line in communication with a fuel pump output and each of the main fuel injectors; an exhaust line having a catalytic converter; and an exhaust injector mounted on the exhaust line for injecting fuel therein upstream of the catalytic converter, wherein the exhaust injector is fed by a subsidiary fuel line in communication with the common fuel line.

is The fuel injected into the exhaust line can then flow downstream with the exhaust gas, and into the catalytic converter, so that the fuel can act as a reducing agent and reduce the NOx to nitrogen gas.

This invention can conveniently be used with a Common Rail Fuel System, where fuel is fed to all the injectors via the common fuel rail or line at a substantially constant pressure, as opposed to other fuel supply systems, where fuel is pulsed to each injector individually in a cyclic order. Since in this invention the subsidiary fuel line leading to the exhaust injector is in communication with the common fuel line, the exhaust injector can be fed continuously at a pressure that is sufficiently high to atomise the fuel finely enough without the need for an air supply or a heater to vaporise the fuel.

The present invention has the additional advantage that the fuel pump is used for supplying fuel to both the main injectors and the exhaust injector, so that an additional fuel pump to supply fuel to the exhaust injector is not 9908629b.doc 07 December 1999 3 required.

Preferably, the exhaust injector will be mounted on the exhaust line at a point that is down-stream of a turbocharger turbine, to avoid fuel depositing on the turbine walls and blades.

The subsidiary fuel line leading to the exhaust injector may be directly connected to the common fuel line, so that the fuel fed to the exhaust injector is at substantially the same pressure as the fuel fed to the main injectors for injecting fuel into the combustion chambers of the engine. The same type of injector component as is used for injecting fuel into the engine may then be used for injecting fuel into the exhaust line.

Alternatively, since the fuel pressure at the exhaust injector need not be as high as that at the main injectors, a pressure reducing device may be placed between the subsidiary fuel line and the common fuel line.

This will allow a less expensive, lower pressure injector to be used for injecting fuel into the exhaust line.

Preferably, the pressure at which fuel is provided to the exhaust injector will be at least 100 bar, so that the spray of injected fuel is more likely to be sufficiently fine for the fuel to react with NOx in the catalyst appropriately.

Preferably, a control device will be provided to control the fuel injection rate into the exhaust line, in order for engine parameters such as engine speed and load to be taken into account.

9908629b.doc 07 December 1999 4 According to a second aspect of the invention, there is provided an exhaust gas purification system for an internal combustion engine characterised in that it comprises: a fuel pump; a plurality of main fuel injectors for injecting fuel into the combustion chambers of an engine; a common fuel line in communication with a fuel pump output and each of the main fuel injectors; an exhaust line having a catalytic converter; and an exhaust injector mounted on the exhaust line for injecting fuel therein upstream of the catalytic converter, wherein the exhaust injector is fed by the fuel pump at a pressure of at least 100 bar.

Because the pressure is at least 100 bar, fuel injected is into the exhaust line is more likely to be injected as a fine enough spray to react efficiently with NOx in the catalytic converter.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which:

Figure 1 shows a schematic diagram of a diesel engine with an exhaust injector connected to a common fuel line according to the invention; Figure 2 shows a schematic diagram of a diesel engine as in Figure 1 except that a fuel reducing device is placed between the common fuel line and the exhaust injector.

Figure 3 shows a schematic diagram of a diesel engine with an exhaust injector connected to a fuel pump.

In Figure 1, a diesel engine 10 is shown having an air 990862gb.doc 07 December 1999 intake 12 and an exhaust line 14, along which there is placed a turbocharger turbine 16 followed by a catalytic converter 19 in the direction of flow. An exhaust output is located in the direction of the arrow 18.

The engine 10 is supplied with fuel by a Common Rail Fuel System (CRF system) generally indicated as 20. The CRF system 20 has a fuel pump 22 connected to four (main) fuel injectors 26 by a common fuel line 24. The fuel pump 22 produces a fuel pressure which is transmitted by the common fuel line 24 to each of the injectors 26 in unison, so that the pressure at the inputs of the injectors 26 is substantially continuous rather than pulsed. The flow of fuel though each injector 26 is individually controlled by is a solenoid valve (not shown). Each valve is timed to open and close in a periodic manner at predetermined moments in the engine cycle.

An exhaust injector 30 is mounted on a passage 32 of the exhaust line 14, upstream of the catalytic converter 19 and downstream of the turbocharger turbine 16. The exhaust injector is directly connected to the common fuel line 24 by a subsidiary fuel line 34 so that the input 36 of the exhaust injector 30 is at a pressure that is substantially equal to the pressure in the common fuel line 24, which is typically 1500 bar to 1800 bar.

The exhaust injector 30 injects atomised fuel into the flow of exhaust gas. When the exhaust gas reaches the catalytic converter 19, the NOx component of the gas reacts with the injected fuel and forms harmless nitrogen gas.

The supply of injected fuel into the exhaust line 14 is regulated by a metering device, such as a solenoid valve 9908629b.doc 07 December 1999 6 46 in the exhaust injector 30. The solenoid valve or other metering device will be controlled by an engine control unit 48 as a function of engine parameters such as engine speed and load, in order for fuel to be injected into the exhaust line 14 at an appropriate rate.

In Figure 2, a pressure reducing device 40 is placed in the fuel path to the exhaust injector 30, between the common fuel line 24 and the subsidiary fuel line 34. The pressure reducing device 40 reduces the pressure at the input 36 to the exhaust injector 30 to a pressure that is less than the common fuel line pressure, but greater than bar. The will allow a less expensive, lower pressure injector component to be used, rather than the higher is pressure injectors 26 necessary to inject fuel into the engine 10.

In Figure 3, the fuel pump 22 has two outputs; a main output 42 for supplying fuel to the (main) injectors 26 and a subsidiary output 44 for supplying fuel to the exhaust injector 30, through the subsidiary fuel line 34.

Here, the subsidiary fuel line 34 is connected directly to the subsidiary output 44 of the fuel pump 22, which produces a pressure that is greater than 100 bar, for the fuel to be injected from the exhaust injector 30 in a fine enough spray.

The subsidiary fuel line 34 may be in communication within the pump with the common fuel line 24, and the pressure reducing device 40 may be incorporated within the pump.

Alternatively, the pump 22 may be capable of generating an intermediate pressure that is below the injection pressure of 1500 to 1800 bar used for the main injectors 24, but above the minimum pressure of about 100 bar for injecting fuel into the exhaust line 14 for reacting with NOx.

990862gb.doc 07 December 1999 7 As it will be appreciated from the above description, this invention provides a simple way of feeding the exhaust injector with continuously pressurised fuel which can be injected into the exhaust gas, in order to neutralise some of its harmful components.

990862gb.doc 07 December 1999 8

Claims

1. An exhaust gas purification system for an internal combustion engine (10) characterised in that it comprises:

a fuel pump (22); a plurality of main fuel injectors (26) for injecting fuel into the combustion chambers of an engine (10); a common fuel line (24) in communication with a fuel pump output and each of the main fuel injectors (26); an exhaust line (14) having a catalytic converter (19); and an exhaust injector (30) mounted on the exhaust line (14) for injecting fuel therein upstream of the catalytic converter (19), wherein the exhaust injector (30) is fed by a subsidiary fuel line (44) in communication with the common fuel line (24).

is

2. An exhaust gas purification system as claimed Claim 1, wherein the pressure at which fuel is provided to the exhaust injector is at least 100 bar.

3. An exhaust gas purification system for an internal combustion engine (10) characterised in that it comprises:

a fuel pump (22); a plurality of main fuel injectors (26) for injecting fuel into the combustion chambers of an engine (10); a common fuel line (24) in communication with a fuel pump (22) and each of the main fuel injectors; an exhaust line (14) having a catalytic converter (19); and an exhaust injector (30) mounted on the exhaust line (14) for injecting fuel therein upstream of the catalytic converter (19), wherein the exhaust injector (30) is fed by the fuel pump (22) at a pressure of at least 100 bar.

4. An exhaust gas purification system for an internal combustion as claimed in Claim 3, wherein the exhaust injector (30) is fed by a subsidiary fuel line (34) in communication with the common fuel line.

990862gb.doc 07 December 1999

5. An exhaust gas purification system as claimed in Claim 1 or Claim 4, wherein the subsidiary fuel line (34) is directly connected to the common fuel line (24).

6. An exhaust gas purification system as claimed in Claim 1 or Claim 4, wherein a pressure reducing device (40) is placed between the subsidiary fuel line (34) and the common fuel line (24).

7. An exhaust gas purification system as claimed in any preceeding claim, wherein the exhaust injector (30) is mounted on the exhaust line (14) at a point that is down stream of a turbocharger turbine (16).

is

8. An exhaust gas purification system as claimed in any preceeding claim, wherein a control device (46) is provided to control the fuel injection rate into the exhaust line.

9. An exhaust gas purification system as claimed in Claim 8, wherein the control device (46) is a solenoid valve in the exhaust injector.

10. An exhaust gas purification system substantially as herein described with reference to the accompanying drawings.

990862gb.doc 07 December 1999