Impact of Fuel Properties on GDI Injector Deposit Formation and Particulate Matter Emissions 2020-01-0388

Gasoline Direct Injection (GDI) engines show advantages in reducing fuel consumption and gaseous pollution emissions when compared to Port Fuel Injection (PFI) engines. However, particulate matter emissions are an essential issue for GDI engine development due to increasingly stringent worldwide emission regulations. Previous studies have shown that gasoline fuel compositions, as well as deposits formed in GDI fuel injectors, can affect emissions in the GDI engine.

In this work, the impact of gasoline fuel properties on forming injector deposits and the resulting effect on particulate emissions were investigated using a modern Chinese GDI engine. Six test fuels with different properties involving changes in olefins, aromatics, heavy (C9/C9+) aromatics, T90 and deposit control additive (DCA) were prepared based on the gasoline survey results from the Chinese gasoline fuel market and the China 6 gasoline fuel standard limits. A 1.0L 3-cylinder turbocharged GDI engine in the Chinese market was prepared and operated under a steady-state condition (2000 rpm, 3 bar BMEP load) lasting for 55 hours to accumulate injector deposits. The injector flow rate and injection pulse width changes caused by injector deposits were measured when different gasoline fuels were used. Meanwhile, the engine out particle number (PN) emissions were measured before, during and after the fouling tests.

Test results indicated that fuel properties showed an obvious impact on GDI injector deposit formation and the PN emissions significantly increased after injector fouling. Gasoline fuels with higher olefin, aromatic and heavy aromatic contents generated more deposits in GDI injectors and resulted in higher PN emissions, while fuel containing DCA was effective in reducing the injector deposit formation and PN emissions. It was also observed that when T90 of the fuel reached 180 °C with increasing amount of heavy aromatics, the injector fouling tendency was reduced, indicating the complicated formation mechanism of deposits in GDI injectors.