Hybrids limit the combustion engine operation, thereby imposing new and challenging technical requirements on evaporative emissions control systems and driving implementation of new technical solutions and technologies. The solutions presented by Delphi include advanced integrated evaporative emissions systems for hybrids and partial zero-emissions (PZEV) vehicle hybrids:

• carbon canisters;
• canister modules; and
• electrically heated hydrocarbon scrubbers for integrated and non-integrated fuel systems.

Standards require control of volatile hydrocarbons (fuel vapor) being released from gasoline fuel systems at any vehicle condition: driving, refuelling or parking. In order to protect the environment and air quality, vapors are temporarily stored in evaporative emissions canisters and introduced as fuel in the engine during vehicle operation.

As gasoline vapors and condensed liquid from the fuel tank enter the canister through the tank tube, hydrocarbon molecules in the vapors and liquid are attracted to and stored on the surfaces of the carbon bed inside the canister (adsorption). A manifold vacuum draws fresh air through the carbon bed, pulling the gaseous molecules into the intake manifold for combustion (purging).

Delphi hybrid evaporative emissions canister modules have been specially designed to help vehicle manufacturers meet the world’s most stringent evaporative emissions requirements (LEV II and LEV III; PZEV and various hybrid vehicle systems) while optimizing a vehicle’s fuel economy.

The modules include a highly efficient carbon canister, a robust electrically heated hydrocarbon scrubber and an advanced electronic controller. While conventional evaporative emissions canisters are designed to operate with regular purge cycles, Delphi says that its hybrid canister modules provide increased canister regeneration efficiency that enables optimal evaporative emissions control in low purge engine operation.

Delphi’s technology eliminates the need for pressurized steel systems in PZEV full hybrid vehicle systems, thus enabling the use of a plastic fuel tank which contributes to an overall vehicle program cost reduction. The heated scrubber also allows the use of low cost carbon for further cost savings.

Additionally, the “plug and play” module capability enables ease of assembly for integrated and non-integrated applications and easy upgrade of existing system architecture. Other benefits include increased durability, safety and reliability, according to Delphi.