**Acknowledgements**

larger than 100 nm. B40 trends show that the increase in engine speed is responsible for an increase in the concentration of particles of diameters under 100 nm and larger than 200 nm. The traces highlight the abrupt decrease in particle number concentration in the range of diameters around 1 µm. The increase in load (at constant engine speed) is responsible for the increase in

**Figure 15.** a): Accumulation mean diameter at 80% load, b): accumulation mean diameter at 3300 rpm [35].

The comparison between the particles' distributions points out that B20 and B40 are characterized by lower number of particles than ULSD in almost all diameters. This behavior agrees with literature data. Studies report that the employment of biodiesel blends produces an increased number of nanoparticles and a reduced number of ultrafine and fine particles in comparison with ULSD [6, 37, 38]. It can be explained by the oxygen content of WCO that favors the combustion completeness in the region of fuel-rich diffusion flame and then pro-

In **Figure 15**, the variation with engine operative conditions of the mean size of accumulation mode is shown. For all tested fuels, the court mean diameter decreases with increasing engine speed at constant load value. The increase in load condition causes an increase in the court

WCO biodiesel blends have lower mean diameter in their exhaust than diesel fuel. B40 has

Biodiesel from waste cooking oil was tested to investigate the impact of WCO percentage in blends with ultralow-sulfur diesel oil in the performance and emission characteristics of an up-to-date light and compact common rail diesel engine, whose main application is in micro-

The engine performance (in terms of available torque, brake specific fuel consumption, brake thermal efficiency) with biodiesel blends was found quite similar for B20 and diesel fuel. B40

motes the oxidation of the already-formed soot and inhibits the soot growth [19].

smaller particle mean diameter as regards B20 for almost all tested conditions.

suffered for the lower caloric value of the blend in comparison with ULSD.

particles' sizes for both B20 and B40.

32 Improvement Trends for Internal Combustion Engines

mean diameter.

**4. Conclusion**

cars and in urban vehicles.

We acknowledge the fundamental contribution of AVL which provided the instrumentation for the particle matter measurements (AVL Particle Counter and AVL Micro Soot Sensor) used during the research activity.
