Impact of preferential vaporization on combustion chamber deposit generation from a gasoline surrogate: A parametric study

Abstract

The effect of injection pressure and impingement-surface temperature on combustion chamber deposit (CCD) inside a constant volume combustion chamber (CVCC) was studied. The CVCC was modified to capture the main characteristics of the spray-wall and film–flame interaction observed in gasoline direct injection (GDI) engines. The measurements were performed at three different injection pressures (30, 100, and 200 bar) and four wall temperatures (353, 393, 433, and 473 K) using a gasoline surrogate (S01) with four components (hexane, isooctane, toluene, 1-methylnaphthalene), under a global equivalence ratio of one. High speed Schlieren measurements and Mie scattering were used to characterize the spray–wall interaction. Moreover, the influence of the vapor distribution of the heavy and light fractions of a second non-fluorescent surrogate (S02, with similar vaporization behavior and composition to S01) doped with p-difluorobenzene (pDFB) and 1-Methylnaphtalene (1-MN) was analyzed around the impingement region. The fluorescent signal of the traces made it possible to study indirectly the effect of preferential vaporization on the CCD generation. Finally, the CCD build-up rate was determined by a gravimetric method. It was found that regardless of the injection pressure, the maximum production of CCD took place at a wall temperature of 393 K, and that an additional increase in the temperature reduced the build-up rate of CCD. The higher retention of heavy fraction on the impingement region at 353 and 393 K, identified by fluorescence, could not explain by itself the higher production of CCD outside the impingement region.