# Effects of Ethanol-Diesel on the Combustion and Emissions from a Diesel Engine at a Low Idle Speed
## 3 Results and Discussion  
### Combustion Characteristics  
#### 3.1.1 Combustion Pressure and Heat Release Rate  
The blending of ethanol has a great effect on combustion in the cylinder. By weight, the ethanol molecule is approximately 33% oxygen, which promotes combustion. On the other hand, the low LHV of ethanol is low, at 64% of that of diesel fuel, but it has a high latent heat of vaporization, which \begin{table}
\begin{tabular}{c c c} \hline \hline
**Table** & **Unit** & **Condition** \\ \hline Engine Speed & rpm & 750 \(\pm\) 10 (Low idle speed) \\ Engine Load & Nm & 40 \\ Cooling Water Temperature & \({}^{\circ}\)C & 85 \(\pm\) 5 \\ Intake Air Temperature & \({}^{\circ}\)C & 25 \(\pm\) 5 \\ Fuel Injection Pressure & bar & 280 \\ Injection Timing & \({}^{\circ}\)CA & Main BTDC 2/Pilot BTDC 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Test conditions. Figure 2: Schematic diagram of the experimental setups. provides an ethanol evaporation cooling effect during combustion. Also, the low density and viscosity of ethanol promote the atomization of the injected fuel. Figure 3a,b and Table 4 shows the combustion pressure and heat release rates for each fuel condition. The maximum combustion pressure of DE_0 is 5828 kPa, and the ethanol-blended DE_3, DE_5 and DE_10 are 4.1%, 3.1% and 2.9% higher, respectively, at 6070 kPa, 6013 kPa and 5998 kPa, respectively. The position of maximum cylinder pressure was at 11 \({}^{\circ}\)CA after top dead center (ATDC) under all fuel conditions. The maximum heat release rate (HRR) is also higher when ethanol is blended. The maximum HRR for DE_3 is increased by 9.3%, from 28.64 J/\({}^{\circ}\)CA to 31.30 J/\({}^{\circ}\)CA at DE_0, DE_3 is increased by 11.2% to 31.86 J/\({}^{\circ}\)CA, and DE_10 is increased by 13.5% to 32.53 J/\({}^{\circ}\)CA. The maximum heat release rate occurred at ATDC 7-8 \({}^{\circ}\)CA under all fuel conditions. The maximum HRR for DE_3 is increased by 9.3%, from 28.64 J/\({}^{\circ}\)CA at DE_0 to 31.30 J/\({}^{\circ}\)CA, DE_5 is increased by 11.2% to 31.86 J/\({}^{\circ}\)CA, and DE_10 is increased by 13.5% to 32.53 J/\({}^{\circ}\)CA. The maximum heat release rate occurred at ATDC 7-8 \({}^{\circ}\)CA under all fuel conditions. [PERSON] [21] reported that the mixture of alcohol increased the HRR due to the increase in the ignition delay because of the low cetane number and high latent heat of evaporation, thereby increasing the maximum combustion pressure. The study by [PERSON] et al. [31] also reported that, with an increased ethanol blending rate, the heat release rate increased dramatically due to the increase in the adiabatic flame template. On the other hand, combustion after the main injection tends to be different from the combustion of pilot injection fuel. When the main injection is sprayed, combustion is generated partially in the combustion chamber, so the diffuse combustion stage is initiated. The greater the increase in the blend ratio of ethanol, the stronger the improvement of combustion by the increase in oxygen content. Also, the addition of ethanol improves the atomization of the injected fuel. [PERSON] [14] said that the advantage of using alcohol as fuel is improving mixing with the air by improving the saturation of the injected fuel through its low viscosity. [PERSON] et al. [17] reported that the increase in ethanol blending resulted in the lower density and reduced surface tension of the blended fuel, which improved the air mixing due to the evaporation of the ethanol spray, which improved the macroscopic spray behavior and atomization performance. [PERSON] et al. [32] also confirmed the injection characteristics of pure diesel fuel, pure ethanol, and ethanol 10% and 20% blended fuel, and reported that the addition of ethanol facilitates the improvement of the spray and atomization.