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METHOD TO MINIMIZE HYDROCARBON EMISSIONS IN A PHEV VEHICLE

IP.com Disclosure Number: IPCOM000229408D
Publication Date: 2013-Jul-26
Document File: 1 page(s) / 187K

Publishing Venue

The IP.com Prior Art Database

Abstract

PHEV vehicles typically contain sealed fuel tanks due to limited engine run time. With limited engine run time, the canister cannot be purged. An FTIV valve shown below is used to seal the fuel tank. Running loss and diurnal vapors are thus trapped inside the tank. Only refueling vapors are adsorbed inside the canister. The PHEV fuel tank is made of steel and designed to withstand large pressure and vacuum magnitudes. The EPA is proposing that future PHEV gas tanks vent themselves in case a small leak in the tank is found. This prevents hydrocarbons (HC) from being emitted into the atmosphere when tank builds up pressure from the diurnal temperature cycle or from heat rejection from a running engine. A pressurized fuel tank with a small leak can emit considerable amounts of HCs.

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METHOD TO MINIMIZE HYDROCARBON EMISSIONS IN A PHEV VEHICLE

PHEV vehicles typically contain sealed fuel tanks due to limited engine run time. With limited engine run time, the canister cannot be purged. An FTIV valve shown below is used to seal the fuel tank. Running loss and diurnal vapors are thus trapped inside the tank. Only refueling vapors are adsorbed inside the canister. The PHEV fuel tank is made of steel and designed to withstand large pressure and vacuum magnitudes. The EPA is proposing that future PHEV gas tanks vent themselves in case a small leak in the tank is found. This prevents hydrocarbons (HC) from being emitted into the atmosphere when tank builds up pressure from the diurnal temperature cycle or from heat rejection from a running engine. A pressurized fuel tank with a small leak can emit considerable amounts of HCs.

Method

The method to mitigate the release of HCs when a small leak is present inside the PHEV fuel tank is to maintain a vacuum inside the tank at all times if possible. The strategy is shown below:

1. During engine running operation, utilize the engine vacuum to keep the tank under constant and moderate vacuum levels. With fuel tank under vacuum, HC will remain inside the fuel tank.

2. During battery running operation, utilize the existing vacuum pump (ELCM) to keep the tank under constant and moderate vacuum.

3. At key off, initially vent the fuel tank by keeping FTIV open. However, FTIV has a considerable current draw (1 amp)...