Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1995-10-13
1997-11-11
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Methods
60284, 60289, 60297, F01N 320
Patent
active
056851448
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the operation of an internal combustion engine fitted with a catalytic converter and having an exhaust gas ignition system for reducing the light-off time of the catalytic converter.
BACKGROUND OF THE INVENTION
PCT Patent Application WO 92/22734, of which the present invention is an improvement, discloses a method of reducing the total emissions during cold starts from an engine burning a hydrocarbon fuel and having an afterburner arranged upstream of a catalytic converter. The method comprises the steps of adding an excess of fuel to the engine combustible charge and adding air to reach the engine exhaust gases to assure the presence in the exhaust/air mixture immediately after the engine has first fired of sufficient concentrations of hydrogen and oxygen to permit the resulting exhaust/air mixture to be ignitable and to burn with a steady flame in the afterburner while the latter is at a temperature close to the ambient temperature, and igniting the exhaust/air mixture in the afterburner immediately after the engine has first fired.
A difficulty encountered in the above method of operating an engine is that the mixture required during cold starts is so rich that it can result in undesirable side effects such as plug fouling and running instability. For these reasons the exhaust gas ignition regime can only be maintained for a relatively short time after the engine has first fired and this result in only a relatively thin slice of the catalysis matrix being heated to its light-off temperature. Thereafter it is necessary to run in a modified regime to ensure that this slice remains hot and that the remainder of the catalysis matrix is brought to its light-off temperature.
OBJECT OF THE INVENTION
The present invention therefore seeks to provide a method of operating an engine that permits exhaust gas ignition to occur during cold starts with more moderate levels of fuel enrichment to the engine.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a method of operating an engine having an afterburner and a catalytic converter downstream of the afterburner comprising the steps of introducing sufficient excess fuel to the engine to produce in the exhaust gases fuel constituents including unburnt hydrocarbons, carbon monoxide and hydrogen, intercepting the unburnt hydrocarbons upstream of the afterburner so as to allow substantially only carbon monoxide and hydrogen to reach the afterburner, introducing sufficient additional air into the exhaust system to bring the composition of only the carbon monoxide, hydrogen and air to stoichiometry or leaner than stoichiometry, the resulting concentration of hydrogen and oxygen in the mixture reaching the afterburner being sufficient for ignition immediately after a cold start, igniting the mixture in the afterburner with an ignition source, releasing the intercepted unburnt hydrocarbons to the afterburner after the ignition and introducing sufficient additional air into the exhaust system to bring the composition of the released unburnt hydrocarbons, carbon monoxide, hydrogen and air to stoichiometry or leaner than stoichiometry to ensure complete combustion within the exhaust system.
In the prior art proposal referred to above, oxygen was added to the system to bring the entire mixture reaching the afterburner to stoichiometry and for this purpose additional oxygen had to be introduced to react not only with the hydrogen and carbon monoxide that are vital to achieve cold ignition but also with the unburnt hydrocarbon content of the exhaust gases. The additional amount of air introduced for the purpose of reacting with the hydrocarbons reduced the hydrogen and carbon monoxide concentrations. For these to reach the critical limit required for cold ignition, the quantity of fuel injected to the engine had to be increased. It should be noted in this context that the concentrations of hydrogen and oxygen are critical in that cold ignition cannot occur if the hydrogen concentration i
REFERENCES:
patent: 3503716 (1970-03-01), Berger
patent: 5379586 (1995-01-01), Honji
patent: 5501073 (1996-03-01), Miyashita
Drouillard Jerome R.
Ford Global Technologies Inc.
Hart Douglas
LandOfFree
Operation of an internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Operation of an internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Operation of an internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1220353