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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Last updated: 2021-11-10