**Author details**

Simeon Iliev

When the relative air-fuel ratio increases, the concentration of HC emissions decreases. The reason for the decrease in HC emissions is similar to that of CO described above. The comparison between the decrease in HC emissions and the blended fuels indicates that methanol is more effective than ethanol. The lowest HC emissions are obtained with methanol-blended

**Figure 15** shows the influence of the blended fuels on NOx emissions. It is noticeable that when methanol and ethanol percentage increases up to 30% E30 (M30), the NOx emission increases, after which it decreases with increasing the percentage of the methanol (ethanol). The reason is that the improved combustion results in increased temperature in combustion chamber. The higher methanol (ethanol) content in the blends lowers the temperature in com-

**1.** Latent heat of evaporation of alcohols, which decreases the temperature in combustion

**2.** The more triatomic molecules are produced: the higher the gas heat capacity and the lower the combustion gas temperature will be. However, the low temperature in combustion

The purpose of the present chapter is to demonstrate the influence of ethanol and methanol addition to gasoline on spark-ignition engine performance and emission characteristics. The

With the increase of the percentage of ethanol in the blended fuel, the engine brake power

With the increase of the percentage of methanol in the blends M5 and M10, the brake power slightly increased, and with the increase of the percentage of methanol in the blends M30 and

As the ethanol (methanol) percentage increased, the BSFC increased. The blended fuels show higher BSFC and lower engine brake power than pure gasoline. Furthermore, there is a slight difference between the BSFC in comparison of gasoline and gasoline blended fuels (E5, E10,

When there is an increase in ethanol and methanol percentage, the CO and HC concentration decreases. The lowest CO and HC emissions are obtained with blended fuel containing

Increasing the percentage of ethanol and methanol leads to a significant increase in NOx

When there is an increase in the ethanol and methanol percentage up to 30% E30 (M30), there is an increase in the NOx concentration, followed by a decrease, after which it decreases with increasing ethanol (methanol) percentage. The lowest NOx emissions are obtained with gasoline.

chamber can also lead to an increment in the unburned combustion product.

fuel (M50). When more combustion is complete, it will result in lower HC emissions.

bustion chamber. The lower temperature is due to:

summarized results from this study are the following:

chamber during the vaporization.

156 Biofuels - Challenges and opportunities

decreased for various engine speeds.

M50, the brake power decreased.

and E20 and M5, M10, and M20).

methanol (M50).

emissions.

**4. Conclusions**

Address all correspondence to: spi@uni-ruse.bg

Department of Engines and Vehicles, University of Ruse, Ruse, Bulgaria
