Hydrocarbon retaining and purging system
First Claim
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1. A method comprising:
- flowing exhaust gas from an inlet to an outlet of a hydrocarbon trap, the trap having a plurality of layers of different porosity and/or of different adsorptive affinity to hydrocarbon chains;
flowing fuel tank hydrocarbons from the inlet to the outlet of the hydrocarbon trap; and
flowing a purging exhaust gas from the outlet to the inlet of the hydrocarbon trap.
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Abstract
Methods and systems are provided for reducing hydrocarbon emissions from an engine having a hydrocarbon retaining system. One example method comprises flowing exhaust gas over a hydrocarbon trap, the trap having a plurality of layers with different porosity and/or a different adsorptive affinity to hydrocarbon chains, and flowing hydrocarbons from a fuel tank over the hydrocarbon trap.
70 Citations
16 Claims
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1. A method comprising:
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flowing exhaust gas from an inlet to an outlet of a hydrocarbon trap, the trap having a plurality of layers of different porosity and/or of different adsorptive affinity to hydrocarbon chains; flowing fuel tank hydrocarbons from the inlet to the outlet of the hydrocarbon trap; and flowing a purging exhaust gas from the outlet to the inlet of the hydrocarbon trap. - View Dependent Claims (2, 3, 4)
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5. A method of operating an engine having a hydrocarbon retaining system coupled to an engine exhaust, an engine intake, and a fuel tank, said hydrocarbon retaining system including a first zeolite layer with a first pore size, and a second zeolite layer with a second pore size, said first pore size being smaller than said second pore size, the method comprising:
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during an engine cold start, routing exhaust gas in a first direction from an inlet to an outlet of the hydrocarbon retaining system to store exhaust hydrocarbons over a length of the hydrocarbon retaining system; and routing fuel tank vapors from the inlet to the outlet of the hydrocarbon retaining system to store fuel tank hydrocarbons over the length of the hydrocarbon retaining system; and during a purging condition, routing a purging exhaust gas in a second, opposite direction from the outlet to the inlet of the hydrocarbon retaining system to purge stored hydrocarbons from the length of the hydrocarbon retaining system, and directing the purging exhaust gas to the engine intake. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A system for a vehicle including an engine intake, an engine exhaust, and a fuel tank, the system comprising:
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a hydrocarbon trap coupled to the engine intake, the engine exhaust, and the fuel tank, said hydrocarbon trap including a first zeolite layer with a first pore size and a first adsorptive affinity to selected hydrocarbon chains, and a second zeolite layer with a second pore size and a second adsorptive affinity to the selected hydrocarbon chains, the first pore size being smaller than the second pore size, said second affinity being greater than said first affinity; and a controller with computer readable instructions for, storing hydrocarbons in the trap by flowing exhaust gas and fuel tank vapors in a first direction across a length of the trap, from an inlet to an outlet of the trap; and purging the stored hydrocarbons by flowing a purge gas in a second, opposite direction across the length of the trap, from the outlet to the inlet of the trap. - View Dependent Claims (13, 14, 15, 16)
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Specification