# Effects of Ethanol-Diesel on the Combustion and Emissions from a Diesel Engine at a Low Idle Speed
## 4 Conclusions  
Different ethanol-diesel fuel blends were applied to a diesel engine operating at a low idle speed to investigate their combustion characteristics, exhaust pollutants and soot morphology. Based on the experimental results, it is possible to draw the following conclusions:  
* The maximum combination pressure and maximum heat release rate of ethanol-blended fuels were higher than those of pure diesel fuel. By increasing the ethanol blend ratio, the maximum combustion pressure decreased and the maximum heat release increased.
* The BSFC increased when ethanol was blended, and increased with the blend ratio; however, the BTEs of ethanol-blended fuels were lower than when pure diesel fuel was used.
* As ethanol was blended and the blending ratio increased, the ignition delay increased, and the combustion duration decreased.
* The COVIMEP values of the ethanol-blended fuels were lower than those of the pure diesel fuel, and tended to increase as the ethanol blending ratio increased above 3%.
* When ethanol was blended and the blending ratio increased, the NOx and soot opacity decreased, but CO emissions increased. The emission ratio of NO2 in NOx also increased with more ethanol. The levels of HC showed a tendency to increase as the ethanol blending ratio increased, although the HC emissions of ethanol-diesel blended fuels are lower than those of pure diesel fuel.
* As the ethanol blending ratio increased, the mean size of the soot particles decreased, and the distribution of small particles increased.  
In low idling conditions with poor combustion conditions, the mixture of bioethanol, a high-oxidant fuel, improves combustion and improves idle stability. Increasing NOx generation due to a longer ignition delay due to the low cetane number of the bioethanol was suppressed by the cooling effect of the high latent heat of evaporation, and as the blend ratio of bioethanol increased, NOx was reduced still further.  
This experiment confirmed its effect by blending pure diesel with bioethanol at a low rate. The low viscosity of bioethanol can adversely affect the lubrication of diesel engines. In the future, it is thought that we will need to study not only the limits of the blending ratio of bioethanol, but also the methods for higher blending ratios (e.g., the addition of biodiesel).  
Figure 10: (**a**) Mean soot particle sizes, and (**b**) distributions of particles.  
**Author Contributions:** [PERSON] suggested this research, performed the experiments, analyzed all experimental data, and wrote this paper. [PERSON] performed the experiments and contributed to combustion analysis. [PERSON] performed the data analysis and contributed to the discussion, and supervised the work and the manuscript. All authors participated in the evaluation of the data. All authors have read and agreed to the published version of the manuscript.  
**Acknowledgments:** This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (No. 2019R11A1A01057727) and the government of Korea (MSIT) (No. 2019R1F1A1063154). The authors also thank the teachers in the Center for University-Wide Research Facilities (CURF) at Jeonbuk National University for their help in collecting some experimental data.  
**Conflicts of Interest:** The authors declare no conflicts of interest.