Development of an Accelerated Test Method for Compressed Natural Gas Fuel System Robustness against Contamination

Sammanfattning: A key factor for driving the shift towards sustainable transportation systems is alternative fuels, where compressed natural gas (CNG) is a beneficial alternative to the conventional fossil fuels with respect to greenhouse gas emissions. A fuel system is needed for heavy-duty natural gas vehicles, in order to transport the highly pressurized gas from the fuel tanks to the internal combustion engine. The fuel system can be contaminated from several different sources – carry-over compressor oil from refuelling stations, water already present in the gas, manufacturing residuals and road dust entering the fuel system via the receptacle valve. The contaminants can induce fuel system failure modes, leading to poor engine performance, increased emissions or gas pressures above component pressure ratings. The objective of this thesis was to develop an accelerated test method to evaluate CNG fuel system robustness against contamination, to be able to prevent CNG fuel system failures and to ensure a high-quality product. The experimental setup was developed to be installed on a truck in order to utilize already present surrounding systems. The setup enables performance testing of six out of nine components belonging to the fuel system, which can be tested individually or combined in an arbitrary way. The setup induces premature failure modes primarily through excessive contamination in a controlled manner. An experimental procedure has been developed as a complement. Validation of metrics through testing is needed before the test method can be considered finalized.