Ignition and combustion characteristics of n-butanol and FPBO/n-butanol blends with addition of ignition improver

In this study, the ignition and combustion characteristics of fast pyrolysis bio-oil (FPBO) are investigated in a commercially available combustion research unit (CRU) system, which is mainly composed of a constant-volume combustion chamber. To make the unmodified CRU system realizable for FPBO combustion, n-butanol and EHN are used to improve the atomization and ignition properties of the fuel blends, respectively. The study first determines an appropriate proportion of EHN additive into n-butanol to arrive at a good balance between the ignition improvement and the amount of EHN addition. Then, the effects of FPBO content in FPBO/n-butanol blends with the same EHN addition are investigated. The effects of chamber wall temperature are also studied.
Experimental results show that the low-temperature and high-temperature heat release phases can be observed in all tested cases. For n-butanol with addition of EHN, the increase of EHN proportion could effectively advance the low-temperature heat release phase and shorten the ignition delay, while the chamber wall temperature is the dominant factor for combustion phasing and combustion duration. For FPBO/n-butanol blends with addition of EHN, FPBO proportion has negligible effects on the ignition delay. The increase of FPBO proportion results in a delayed combustion phasing and prolonged combustion duration, while these effects become less obvious at the elevated chamber wall temperature.