Studies on Purge Noise Reduction in Vapor Line using 1D Simulation

摘要

Noise reduction is a major concern in the recent times and global automotive industries evolve new technology to meet the norms. The major contribution to vehicle’s interior noise is from engine, intake, exhaust, structure, aerodynamic and road. In recent days, more attention is given to other sources of noises which are dominant. Purge noise is one such noise which has more impact to the interior noise because the cabin has become much quieter due to the latest advancements and new technologies used in vehicle design and development. Using the air dampening device in the vapor line is one of the techniques to minimize the purge noise. In this paper a study is carried out in order to optimize the design of air dampening device which meets the requirements. Fuel vapors that got collected in canister will purge through vapor line and are controlled by purge valve before they enter the engine. The solenoid controlled purge valve is moved by the ON/OFF pulses from the Engine Control Module (ECM) to control the flow of fuel vapor. The opening and closing of valve creates pressure pulsations which travels through vapor line and radiate as purge noise. In current practice, the purge noise is not measured separately, but the effect is heard at the Driver Right Ear (DRE) in the frequency range of 100 to 1000Hz. A component level 1D simulation model is developed in order to study the impact of the design parameters to reduce the purge noise in a 4 Cylinder Internal combustion engine. Using the 1D simulation tool GT- Power, a model is built and various designs are simulated to study the acoustic effect of the air dampening device downstream of the vapor line. A non-linear Transmission Loss (TL) setup is used in this simulation. Studies are carried out to understand the impact on the TL in the Frequency range (100 - 1000 HZ) with different architectures such as diameter, length, volume, inlet pipe and outlet pipe. Results are plotted between Frequency vs TL in order to understand the geometry which provides higher TL. Higher the TL lesser will be the purge noise. Multiple iterations are carried out in order to arrive at the optimum design to meet the TL requirements. Testing is carried out with the base line and optimized design. The optimized design in simulation has shown a good improvement in the purge noise reduction. This technique can be used to design an optimum vapor line in the early development stage for future vehicle programs.