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Current energy policies are encouraging the near-term use of fuels derived from civil and industrial waste residues, giving new perspectives for their disposal. The possibility of using, in Diesel engines, a liquid fuel derived from waste synthetic polymeric matrices, such as scrap tyres, is evaluated in this paper. The fuel is obtained by means of an innovative technology based on a thermo-mechanical cracking process at moderate temperatures and pressures. A preliminary investigation was carried out on a 440 cm3 single-cylinder Diesel engine for stationary applications using a commercial automotive Diesel fuel (UNI-EN 590:2010) and two mixtures of automotive Diesel fuel and tyre pyrolysis oil (TPO): the first one containing 20% TPO by volume, the other containing 40% TPO.

Homogeneous charge compression ignition (HCCI) combustion is considered to be an attractive alternative to traditional internal combustion engine operation because of its extremely low levels of pollutant emissions. However, there are several difficulties that must be overcome for HCCI practical use, such as difficult ignition timing controllability. Indeed, too early or too late ignition can occur with obvious drawbacks. In addition, the increase in cyclic variation caused by the ignition timing uncertainty can lead to uneven engine operation. As a way to solve the combustion phasing control problem, dual-fuel combustion has been proposed. It consists of a diesel pilot injection used to ignite a pre-mixture of gasoline (or other high octane fuel) and air. Although dual-fuel combustion is an attractive way to achieve controllable HCCI operation, few studies are available to help the understanding of its in-cylinder combustion behavior.