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Abstract



Leakage detection in evaporative fuel systems for petrol-based passenger cars


The emissions released from the exhaust pipe are not the only pollutants emitted by passenger cars. Evaporation of hydrocarbons from fuels, such as gasoline, harm the environment as well. One way to prevent this from happening is by mounting a carbon canister to the fuel tank, through which vapours and gases must pass to escape into the environment. This canister is filled with activated carbon and collects the hydrocarbons. Fuel systems like these will in this thesis be referred to as purge systems. If a leak occurs however, hydrocarbons may still be emitted into the environment. The amount that may escape from a purge system undetected, is regulated by governments through legislation. One example is the Californian Air Resources Board’s legislation [1], where it is stated, that leakages down to 0.5mm in diameter must be detected by a vehicle’s diagnostic system. This thesis has been conducted at Linköpings university in cooperation with Volvo Car Corporation. The main goal has been to analyse and evaluate leakage detection algorithms for fuel evaporative systems, using the laws of thermodynamic physics and measurements provided by Volvo Car Corporation. Three algorithms for leakage detection are evaluated in this thesis. These have been analysed and evaluated using data provided by Volvo Car Corporation. Evaluation has shown that the algorithm devised by Volvo Car Corporation does not detect leakages down to 0.5mm in diameter using only the pressure sensor. The other two algorithms detected leaks down to 0.5mm in diameter and under certain circumstances may detect 0.3mm in diameter leaks.

Benjamin Lundahl

2014

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