# A Review of Early Injection Strategy in Premixed Combustion Engines
## 5 Blending Ratio  
Because of the different physical and chemical properties of alternative fuels, the blending ratio of alternative fuel directly affects the overall spray behavior, atomization characteristics, and emission characteristics. [PERSON] et al. [PERSON] et al. (2019) investigated different blending ratios (20-100%) of biodiesel combustion in an optical HSDI diesel engine under low-load premixed combustion conditions using the early injection strategy. Results showed that fuel impingement on the wall was observed for all ratios. The liquid penetration became longer and fuel impingement was stronger with increased biodiesel ratio; also, \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Author** & **Injection Angle (\({}^{\circ}\))** & **Fuel** & **BSFC** & **NOx** & **HC** & **CO** & **Soot** \\ \hline [PERSON] and [PERSON] [PERSON] and [PERSON] (2019) & 60/156 & Diesel & \(\downarrow\) & \(\rightarrow\) & na & na & na \\ [PERSON] et al. [PERSON] et al. (2019) & 70/150 & Diesel & na & \(\downarrow\) & na & na & \(\uparrow\) \\ [PERSON] et al. [PERSON] et al. (2019) & 70-150 & Diesel & \(\downarrow\) & na & na & \(\uparrow\) \\ Mobasheri and Peng Mobasheri and Peng (2019) & 90-145 & Diesel & \(\downarrow\)\(\uparrow\) & \(\downarrow\) & na & na & \(\downarrow\uparrow\) \\ [PERSON] et al. [PERSON] et al. (2019) & 100–148 & Diesel & na & \(\uparrow\) & na & na & \(\uparrow\) \\ [PERSON] and [PERSON] and [PERSON] and [PERSON] (2019) & 100/150 & Diesel & na & \(\uparrow\) & \(\downarrow\) & \(\downarrow\) \\ [PERSON] (2019) & 100-158 & Diesel & na & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) \\ [PERSON] et al. [PERSON] et al. (2019) & 70/156 & Bioethanol blended & \(\downarrow\) & na & \(\downarrow\) & \(\downarrow\) & na \\ [PERSON] et al. [PERSON] et al. (2019) & 60/70/156 & DME & \(\downarrow\) & \(\rightarrow\) & \(\downarrow\) & \(\downarrow\) & \(\rightarrow\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Variation of performance and emissions after decreasing the injection angle (two-stage). the ignition delay became longer and heat release curves became lower and broader. This could be explained by the higher boiling point and lower cetane number of the biodiesel. Except for B0, soot luminosity increased with increasing biodiesel ratio. This might be because the low volatility of biodiesel results in locally rich regions with higher soot luminosity, as shown in Figure 13. NOx emissions first decreased with increasing biodiesel ratio; then, after the ratio passed a certain value, NOx emissions increased. This is because of the trade-off between ignition delay and oxygen content. [PERSON] et al. [38] investigated the effects of bioethanol-blended diesel fuel on combustion and emission characteristics in an early injection diesel engine. The blending ratio of the bioethanol varied from 10% to 30%. Results showed that an increased bioethanol blending ratio extended the ignition delay due to lower cetane number and the decreased gas temperature caused by the evaporation of bioethanol with large latency. The difference in ignition delay between pure diesel and diesel-bioethanol blended fuels became larger under early injection conditions. The bioethanol-diesel blending caused a small decrease in soot emission because of the high oxygen content, and reduced NOx emission because of the low combustion temperature caused by the high heat of evaporation of bioethanol fuel and lower heating value. However, HC and CO emissions increased with an increased bioethanol blending ratio. [PERSON] et al. [100] investigated the influence of the blended gasoline ratio on gasoline/diesel dual-fuel combustion. The blending ratio of the gasoline was increased from 68% to 84%. Results showed that a more homogeneous charge and lower global fuel reactivity resulted from increasing the gasoline ratio, which led to later combustion phasing. The retarded combustion phasing dropped the cylinder temperature, which reduced the cylinder pressure and NOx emissions.