Shock Waves in Canister Purge Valves

A valve used in automotive applications for purging fuel vapors accumulated in canister to deliver into the engine intake is investigated. Computational Fluid Dynamics (CFD) methods are employed for predicting the maximum mass flow rate through the valve due to pressure drop across the upstream and downstream of the valve. The CFD analyses show good correlation with the experimentally determined pressure drop and the mass flow rate values across the purge valve. More specifically, the chocking behavior of the purge valve predicted through CFD accurately matches the experimental result. Finally, the CFD predicts the appearance of shock wave patterns when back pressure values at the purge valve system exit are varied. The predicted shock wave patterns can be detrimental under normal operating conditions of a fuel system.