초록 ▼

A diesel (compression ignition) engine having combustion management means and an exhaust gas aftertreatment system without an NOx trap, which system includes a platinum group metal (PGM) catalyst liable to be poisoned by fuel sulphur to cause significant degradation of catalyst performance, which en

A diesel (compression ignition) engine having combustion management means and an exhaust gas aftertreatment system without an NOx trap, which system includes a platinum group metal (PGM) catalyst liable to be poisoned by fuel sulphur to cause significant degradation of catalyst performance, which engine is fuelled, at least intermittently, by a diesel fuel containing such levels of sulphur as to cause poisoning of the catalyst, wherein the combustion management means is effective to modulate the air/fuel ratio (λ) to 0.95, preferably 0.90, or richer for a time which is in aggregate sufficient to cause release of significant quantities of sulphur-containing species from the catalyst or catalyst components, whereby the catalyst is regenerated.

대표청구항 ▼

1. A diesel (compression ignition) engine having combustion management means and an exhaust gas aftertreatment system which system comprising a platinum group metal (PGM) catalyst liable to be poisoned by fuel sulfur to cause significant degradation of catalyst performance, which engine is fuelled,

1. A diesel (compression ignition) engine having combustion management means and an exhaust gas aftertreatment system which system comprising a platinum group metal (PGM) catalyst liable to be poisoned by fuel sulfur to cause significant degradation of catalyst performance, which engine is fuelled, at least intermittently, by a fuel containing such levels of sulfur as to cause poisoning of the catalyst, wherein the combustion management means is effective to modulate the air/fuel ratio (λ) in pulses to 0.95 or richer to provide a series of peak enrichments of from 250 milliseconds to 5 seconds in duration for an aggregate time of from 10 seconds to 10 minutes, whereby the catalyst is regenerated, and wherein the exhaust gas aftertreatment system does not include a NOx trap.2. An engine according to claim 1, wherein the combustion management means is effective to modulate the air/fuel ratio pulses to 0.90 or richer.3. An engine according to claim 1, wherein the catalyst is an oxidation catalyst.4. An engine according to claim 1, incorporating “common rail” fuel injection, programmed to provide in at least one cylinder, such a quantity of fuel post combustion in the main power stroke, so as to reach, in the exhaust gases, λ of 0.90 or richer.5. An engine according to claim 1, wherein the catalyst is an oxidation catalyst and the exhaust gas aftertreatment system also includes a particle or soot filter downstream of the catalyst.6. An engine according to claim 1, wherein it is fuelled with diesel fuel containing at least 250 ppm sulfur.7. A method of regenerating a PGM catalyst poisoned by sulfur in the exhaust gas aftertreatment system of an internal combustion engine, which method comprising modulating the air/fuel ratio (λ) of the exhaust gases passing through the system, which system includes the catalyst but does not include a NOx trap, to 0.95 or richer to provide a series of peak enrichments of from 250 milliseconds to 5 seconds in duration for an aggregate time of from 10 seconds to 10 minutes, whereby the catalyst is regenerated.8. Method according to claim 7, wherein the catalyst is in the temperature range 200?500° C., preferably 350?500° C., during regeneration.9. Method according to claim 7, wherein the exhaust gas is derived from diesel fuel containing at least 250 ppm sulfur.10. A method according to claim 7, wherein λ in the exhaust gases is 0.90 or richer.11. Method according to claim 7, wherein the catalyst is in the temperature range 350° C.?500° C. during regeneration.12. A method of regenerating a PGM catalyst poisoned by sulfur in the exhaust gas aftertreatment system of an internal combustion engine, the method comprising modulating the air/fuel ratio (λ) of the exhaust gases passing through the system, which includes the catalyst but not a NOx trap, to 0.95 to 1.1 to provide a series of peak enrichments of from 250 milliseconds to 5 seconds in duration for an aggregate time of from 10 seconds to 10 minutes, whereby the catalyst is regenerated.13. Method according to claim 12, wherein the catalyst is in the temperature range 200?500° C. during regeneration.14. Method according to claim 12, wherein the exhaust gas is derived from diesel fuel containing at least 250 ppm sulfur.15. Method according to claim 12, wherein the catalyst is in the temperature range 350° C.?500° C. during regeneration.16. A diesel (compression ignition) engine having combustion management means and an exhaust gas aftertreatment system which system comprising a platinum group metal (PGM) catalyst liable to be poisoned by fuel sulfur to cause significant degradation of catalyst performance, which engine is fuelled, at least intermittently, by a fuel containing such levels of sulfur as to cause poisoning of the catalyst, wherein the combustion management means is effective to modulate the air/fuel ratio (λ) in pulses to 0.95 to 1.1 to provide a series of peaks of from 250 milliseconds to 5 seconds in duration for an aggregate time of from 10 seconds to 10 minutes, whereby the catalyst is regenerated, and wherein the exhaust gas aftertreatment system does not include a NOx trap.17. An engine according to claim 16, wherein the catalyst is an oxidation catalyst.18. An engine according to claim 16, incorporating “common rail” fuel injection, programmed to provide in at least one cylinder, such a quantity of fuel post combustion in the main power stroke, so as to reach, in the exhaust gases, the air/fuel ratio (λ) pulses.19. An engine according to claim 16, wherein the catalyst is an oxidation catalyst and the exhaust gas aftertreatment system also includes a particle or soot filter downstream of the catalyst.20. An engine according to claim 16, wherein it is fuelled with diesel fuel containing at least 250 ppm sulfur.