Method of controlling a direct-injection gaseous-fuelled internal combustion engine system with a selective catalytic reduction converter

摘要

A method controls a direct-injection gaseous-fuelled internal combustion engine system to improve the conversion efficiency of an SCR converter that is operative to reduce levels of NOx. The method comprises detecting when the internal combustion engine is idling and timing the injection of a first quantity of fuel to begin injection when the engine's piston is near top dead center; and controlling the temperature of exhaust gas to be above a predetermined temperature that is defined by an operating temperature range that achieves a desired conversion efficiency for the selective catalytic reduction converter, by: (a) timing injection of the gaseous fuel to begin after timing for injection the first quantity of fuel, and (b) increasing exhaust gas temperature by increasing a delay in timing for injecting the gaseous fuel, while limiting the delay to keep concentration of unburned fuel exiting the combustion chamber below a predetermined concentration.

主权项

1. A method of controlling a gaseous-fuelled internal combustion engine system comprising an internal combustion engine and a selective catalyst reduction (SCR) converter, said internal combustion engine comprising a combustion chamber defined by a cylinder and a piston reciprocable within said cylinder, said piston being connected to a crankshaft that rotates when said piston reciprocates, and an injector for injecting a gaseous fuel directly into said combustion chamber, wherein an exhaust gas exiting from said combustion chamber is received in said selective catalyst reduction (SCR) converter that is operative to reduce levels of NOx in said exhaust gas by converting NOx into nitrogen and water, said method comprising:
(A) detecting at least one engine parameter indicative of when said internal combustion engine is idling; and (B) in an engine cycle, during said internal combustion engine's idling time:
(i) beginning injection of a first quantity of fuel when said piston is near top dead center; and(ii) controlling temperature of exhaust gas exiting said combustion chamber to be above a predetermined temperature that is defined by an operating temperature range that achieves a desired conversion efficiency for said selective catalytic reduction converter, by:
(a) beginning injection of said gaseous fuel after said beginning injection of said first quantity of fuel, and(b) increasing exhaust gas temperature by increasing a delay in timing for injecting said gaseous fuel, while limiting said delay to keep concentration of unburned said gaseous fuel exiting said combustion chamber below a predetermined concentration, wherein said delay in timing, measured in degrees of crank angle rotation, is between 14 and 25 degrees after top dead center.