Active vapor pressure regulation for evaporative emission control in plug-in hybrid electric vehicle fuel systems

When plug-in hybrid electric vehicles (PHEVs) operate under long-term electric-only driving or extended parking conditions, the conventional passive evaporative emission control system is prone to carbon canister saturation, leading to uncontrolled vapor release into the atmosphere. To address this issue, this study proposes a novel active vapor recovery system that suppresses gasoline evaporation by actively regulating the vapor pressure in the fuel tank based on gas–liquid phase equilibrium. A dynamic vapor pressure balance model under electric-only operating conditions is established to quantify vapor generation and control demand as a function of ambient temperature variation. An experimental test platform is developed to validate both the feasibility of the proposed active control strategy and the accuracy of the vapor generation model. Experimental results show that the deviation between the theoretical and measured vapor quantities remains within 5.08%, demonstrating that the proposed method can effectively achieve quasi-zero evaporative emissions in PHEV fuel systems during electric-only operation. This study provides a new technical route beyond conventional passive control approaches for evaporative emission mitigation in PHEVs.