EVAP System Fluid-Dynamics and Chemistry Modelling for EMS Purge Control Development and Optimization English Free

  • Category Technical paper
  • Related event International Congress : SIA Powertrain - Versailles 2015 - 27-28 May 2015
  • Edition SIA
  • Date 05/28/2015
  • Author L. Smith, A. Hussain - Jaguar Land Rover | E. Pautasso, E. Servetto, E. Graziano - Powertech Engineering | J. Brown - Gamma Technologies
  • Language English
  • Type PDF file (1.03 Mo)
    (Downloadable immediately on receipt of online payment)
  • Number of pages 10
  • Code R-2015-04-45
  • Fee Free

Evaporative emission control (EVAP) systems employing activated carbon canisters have long been an effective means for reducing HC pollutants produced by vehicles equipped with gasoline engines. From an engineer’s perspective, the canister loading during engine shut-off is a quite straightforward process mainly governed by the in-tank conditions and by the chemical kinetics of the HC adsorption. On the other hand, purging the canister while the engine is running is somehow more complex. In fact, the purged fuel vapours recirculated to the intake manifold contribute to the combustion and therefore require the adoption of dedicated fuel injection strategies in order to avoid operating the engine outside the stoichiometric window.
Conventional purge circuits on NA SI engines exploit the intake manifold depression during throttled operation at partial load to drive the fuel vapours into the engine air path. On the other hand, turbo-charged GDI engines employ dual-path EVAP system, in which the purge gases can be directed either to the manifold or to the compressor inlet when the engine is boosted. The pressure losses and flow velocities in each of the two routes are critical parameters in the dimensioning and choice of the valves and ducts along the EVAP system, in order to assure the necessary purge flow. Unfortunately, experimental measures are quite difficult and often unreliable.
CAE techniques represent a powerful tool to develop and optimize the EVAP circuit and control system. In this perspective, this paper describes how an integrated model, including a model of the GTDi 2.0 litre engine and the EVAP system sub-model, was built and correlated to experimental measurements using the 1-D fluid-dynamics software GT-SUITE. A standalone canister model was built, in which the chemical kinetics of the HC adsorption and desorption were modelled in detail. A comprehensive experimental campaign was carried out on a dedicated test rig, to collect the data required to calibrate and validate the standalone model. Different loading and purging conditions were investigated, by changing the inlet flow composition and velocity. The simulation model was setup to run on all the various experimental conditions and an in-depth correlation study was conducted. A good agreement was obtained between simulation results and measures. The charcoal canister and the complete EVAP system models were eventually implemented in a detailed engine model, and validated over a FTP-75 driving cycle demonstrating its suitability to be used as a virtual test rig for the design and development of the EVAP circuit and control system, reducing the costly and time-demanding prototyping and testing activities.