Comparative Study on the Macroscopic Characteristics of Gasoline and Ethanol Spray from a GDI Injector under Injection Pressures of 10 and 60 MPa

To reduce particulate matter (PM) emissions from vehicles powered by gasoline direct injection (GDI) engines, increasing the fuel injection pressure has been one promising approach. However, a comparison of macroscopic characteristics between gasoline and ethanol from a GDI injector under an ultrahigh injection pressure of more than 50 MPa has not been reported. The experimental study presented in this paper can provide some new and valuable information about comparing and analyzing the macroscopic characteristics of gasoline and ethanol spray from a GDI injector in both front and side views under injection pressures of 10 and 60 MPa. The experimental results show that compared to ethanol, gasoline spray has a slight advantage in L-S (penetration of whole spray), L-C (penetration of core region of spray), theta(S) (spray cone angle), and R-I (irregularity of spray boundary) under both P-I (injection pressure) = 10 MPa and P-I = 60 MPa, which would promote a more homogeneous mixture of air and fuel. Furthermore, the advantage of gasoline in theta(S) is more pronounced under P-I = 60 MPa. At the end of injection, S-S (area of whole spray) of gasoline is around 2% larger than ethanol, while its advantage in S-C (area of core region of spray) can be around 5%. With the increase of P-I from 10 to 60 MPa, a marked increase of R-S (the ratio of S-C to S-S) and R-I indicates that atomization and air-fuel mixture homogeneity can be significantly improved for both gasoline and ethanol spray. Besides, a minor revision to the Dent model helps achieve a significant improvement in the prediction accuracy of L-S for both gasoline and ethanol spray under injection pressures of 10 and 60 MPa.