Impact of the Injection and Gas Exchange on the Particle Emission of a Spark Ignited engine with Port Fuel Injection

Paper #:
  • 2017-01-0652

  • 2017-03-28
Upcoming stringent limits for particulate numbers (PN) of spark ignited (SI) engines imply further challenges for the combustion process development. Wall film formation within the combustion chamber is a major source of particle generation through non-premixed turbulent combustion. This study presents a methodology to predict particle generation from wall wetting employing numerical CFD simulation and fuel film analysis. The engine parameters spray pattern, injection timing, intake valve timing, as well as engine load/speed were varied and their impact on wall film and PN was evaluated. A naturally aspirated 4-cylinder gasoline engine with port-fuel injection was investigated at wide open throttle. It was equipped with soot particle sampling technology and optical access to the combustion chamber of cylinder 1. In-cylinder high-speed visualisation revealed a notable presence of non-premixed turbulent flames, which were typically initiated between the valve seats and cylinder head. Flames were observed on both intake valve regions and their size was found to match qualitatively with the PN measurements. The highest amounts of particles were obtained at early intake valve timing, high engine load/speed and open valve injection with small spray cone angles. Spray propagation, wall film transport and droplet impingement were simulated using a validated CFD multi-component fuel model [1]. Wall film distribution and properties were carefully analysed on the nearby surfaces where non-premixed flames were spotted. An excellent correlation was found between the extent of wall wetting, the intensity of diffusion flame and the number of measured particles over a broad range of operating conditions. The presented technique can be used to evaluate the potential sources of particle emissions in PFI engines in early development stages, based on the numerical analysis of the wall film. [1] Lauer, T., Heiss, M., Bobicic, N., Holly, W. et al., "A Comprehensive Simulation Approach to Irregular Combustion," SAE Technical Paper 2014-01-1214, 2014
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