“…Regarding semiempirical equations about L S prediction, a simplified method named the Dent model was proposed in 1971, which considers injection time and ambient temperature, as shown in eq . − Furthermore, based on the experimental results of L S in this research, a revised version of Dent model is developed in eq to provide a better match. The coefficient of determination R 2 is introduced in eq to evaluate the match quality of the models with experimental data of L S .…”
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), θ 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 θ 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.
“…Regarding semiempirical equations about L S prediction, a simplified method named the Dent model was proposed in 1971, which considers injection time and ambient temperature, as shown in eq . − Furthermore, based on the experimental results of L S in this research, a revised version of Dent model is developed in eq to provide a better match. The coefficient of determination R 2 is introduced in eq to evaluate the match quality of the models with experimental data of L S .…”
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), θ 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 θ 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.
“…Meanwhile, increasing the injection pressure can accelerate vapor-phase diffusion due to high momentum. 55 Figure 13.Vapor-phase area under different ambient conditions and injection pressures.…”
Section: Resultsmentioning
confidence: 99%
“…Meanwhile, increasing the injection pressure can accelerate vapor-phase diffusion due to high momentum. 55…”
The depletion of fossil fuels and stringent emission regulations have encouraged the development of renewable fuels, especially biodiesel and alcohols fuels. The aim of the investigation is to explore the spray diffusion characteristics at different biodiesel-butanol blended ratios (0, 10%, 30%, 50%), ambient temperatures (600 K, 700K, 800 K) and pressures (1 MPa, 3MPa, 5 MPa). The experiment was carried out in a constant-volume combustion chamber. The liquid- and vapor-phase spray images were captured by backlight illumination and schlieren imaging technique, respectively. The axial, radial and spatial diffusion characteristics were analyzed, including spray penetration, cone angle, area, R-parameter and perimeter ratio. Results show that in the case of biodiesel mixed with 10% n-butanol, for liquid-phase spray, the liquid-core spray with high concentration has the largest impact on axial diffusion, and for vapor-phase spray, axial dispersion is slower and radial diffusion is faster. The fuel density and ambient temperature have a more significant impact on the liquid-phase axial dispersion at the steady-state compared with ambient pressure and injection pressure. At lower ambient pressures, increasing the injection pressure can accelerate the radial diffusion and increase the spray cone angle, which is opposite of the variation law at higher ambient pressures. The radial spray has a faster diffusion with adding a small or middle proportion of n-butanol, and the maximum values of liquid- and vapor-phase cone angles appear at biodiesel blended with 30% and 10% n-butanol, respectively. Moreover, the axial diffusion plays a dominant role in the spray spatial dispersion.
“…Spray breakup length and time can be affected by several factors. Higher injection pressure and smaller nozzle diameter lead to shorter breakup length [15]. Liquid surface tension plays an important role in slowing droplets' breakup [16].…”
The liquid fuel breakup mechanism in spray injection with ambient air for diesel and biodiesel at different fuel temperatures is studied numerically. We find that biodiesel fuel type injection with low fuel temperature induces more air entrainment volume to the boundary of the spray than diesel fuel injection and higher fuel temperature. Meanwhile, the normalized parcel density for biodiesel is 12% larger than that of diesel and peaks at a shorter distance along the spray line from the injection point (42 vs. 46 mm). Biodiesel fuel demonstrates a maximum 0.395 mg/s of air mass flow while diesel max mass flow is 0.279 mg/s. As a result, the air entrainment volume of biodiesel to the moving spray area at 1.4 ms reaches 3723.98 mm 3 while for diesel the amount is 3151.27 mm 3 . However, the absorbed y-direction air velocity into the spray core for diesel fuel is dominant. The results give new insights into air exchange to spray boundary in the near nozzle and spray tip area: towards the tip of spray the air pushout is remarkable. Higher fuel temperature leads to slightly lower air exchange flow and entrainment (5.2%), cone angle reduction from 300 to 325 K fuel temperature, and increased surface area:volume ratio for diesel.
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