Investigations of Port Dual Injection (PDI) Strategies in Single Cylinder SI Engine Fueled with Ethanol/Gasoline Blends

Novel port dual-injection (PDI) strategy helps to utilize bio-fuels, improve the performance and lower the emissions with higher mass fractions of bio-fuels. PDI strategy in SI engine allows intake manifold blending of two different fuels at any blend ratio. This paper presents the numerical study of PDI strategy using a single cylinder SI Ricardo E6 research engine. The objective of this study is to extend predictive fractal combustion model for ethanol/gasoline blends and assess the influence of ethanol (E10 to E50 mass fractions) addition to gasoline in a PDI engine. Quasi dimensional simulation is carried out using AVL Boost under wide open throttle condition at 1500 rpm. AVL Boost engine model is validated for gasoline and ethanol/gasoline pre-blends port fuel injection (PFI) with the experimental data of published literature obtained for the same engine. PDI strategies- Distance-Injection and Close-to-valve Injection have been applied to assess the extent of the improvements obtained through spark timing optimization. The performance, combustion and emissions characteristic of different ethanol/gasoline blends have been compared between the pre-blend PFI strategy and the PDI equivalent. Maximum improvement in Brake Power is 7 percentage points with PDI. Maximum increase in Indicated efficiency is 4.5 percentage points. Effective Octane Number is enhanced in the range of 7 to 10 units for above blend ratios with PDI. With PDI 6 and 12.5 percentage points decrease in NO_x and HC emissions respectively are observed in comparison to pre-blend PFI whereas no appreciable change in CO emissions. PDI strategies shows overall superior results in terms of performance and emission in comparison to gasoline and pre-blendPFI using single injector.