THE EFFECT OF FUEL VARIATION ON FLAME PROPAGATION IN IC ENGINES WITH STRONG MACRO FLOWS
- 1 Institute of Nuclear Sciences “VINČA”, University of Belgrade, Serbia
In this paper some results concerning the evolution of flame propagation through unburnt mixture of two different hydrocarbon fuels,such as CH4 and C8H18, in engines with strong macro flows were presented. Flame propagation was represented by the evolution of spatial distribution of temperature in various cutplanes within combustion chamber. Flame front location was determined in zones with maximum temperature gradient. All results were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry of IC engine combustion chamber with moving boundaries. In 4.-valve engines the fluid flow pattern during intake is characterized with organized tumble motion pursued by small but clearly legible deterioration in the vicinity of BDC. During compression the fluid flow pattern is entirely three-dimensional and fully controlled by vortex motion located in the central part of the chamber. For that reason these engines are designated as IC engines with strong macro flows (swirl, squish, tumble) yielding non-spherical flame shapes usually encountered in quiescent flows. Flame propagation results for both fuels were obtained with eddy-viscosity model i.e. with standard k-ε model of turbulence.
The interplay between fluid flow pattern and flame propagation is entirely invariant as regards fuel variationindicating that flame propagation through unburnet mixture of CH4 and C8H18 hydrocarbon fuels is not chemically controlled but controlled by dint of turbulent diffusion.