Modelling of pressure losses in the Evaporative Emission System

This thesis investigates the possibility to use a simulation tool to study pressure drop in the Evaporative Emission (EVAP) system, exemplified with the system for the car model S60 sold on the US market, called USS60. The EVAP system is a part of the fuel system in the vehicle and prevents evaporated hydrocarbons from the fuel to escape to the environment. As the performance of the system is strongly dependent on the flow and pressure it is of great importance to have knowledge about the pressure losses in the system. A reliable simulation tool would save both time and money in the design of the system since less prototype tests would be needed if it is possible to replace tests with simulations. In this work, the simulation software, GT Suite, has been used to model pressure losses in the EVAP system, and to investigate how changes in the system influence the pressure drop during the two main processes; purge and refuelling. First, experiments on the real EVAP system were carried out to obtain data for validation of the model and to obtain data needed for modelling of the more complex components. A model was then set up for simulation of the system and finally a sensitivity analysis was performed to investigate the impact on the pressure losses when changes in the EVAP system were made. The results show that the pressure losses in the Pipe 5 has the largest impact on total pressure drop in the system during the purge process and corresponds to 75% of the total pressure loss. During the refuelling process the canister affects the pressure losses the most. The simulation model is a simplification of the real system, but it gives an indication of how chosen design parameters influence the pressure drop. The model can be used for predictive analyses as long as the simulation results match the characteristics of the complex components