Combustion characteristics of waste styrene–butadiene rubber oil derived from thermal pyrolysis process: experiment and numerical simulation

Abstract

Owing to the similar carbon range in components, the pyrolytic oil derived from waste styrene–butadiene rubber (SBR) is preferred in aviation, for achieving waste-to-energy and fly net zero missions. The present study investigated the combustion and emission characteristics of SBR using a constant volume combustion chamber (CVCC) spray at 673–873 K initial temperature (Tini), 10 and 15 bar initial pressure (Pini), and 0.5 equivalence ratio (φ). SBR combustion properties were benchmarked with conventional jet propellant 5 (JP-5), and JP-5 and SBR were blended at a 50% volume ratio (JP-5-SBR-50). SBR has a shorter ignition delay (ID) and combustion delay (CD) at 15 bar Pini, compared to 10 bar. SBR exhibits negative temperature coefficient (NTC) behavior starting from Tini = 773–823 K, which was more significant at 10 bar. In the NTC region, at Tini = 723 and 823 K, the ID nearly has a 3-fold variation between 10 and 15 bar, and CD has 4- and 1.7-fold variations at Tini = 723 and 823 K, respectively. Finally, τ has a 3- and 1.5-fold variation at Tini = 723 and 823 K. JP-5 has a shorter ID and CD, followed by JP-5-SBR-50 and SBR. At Tini = 673 K, the addition of JP-5 to SBR significantly shortened ID and CD by nearly 24% and 17.5%. JP-5 has higher CO2, thermal NOx, and unburned HC emissions, whereas those were reduced with SBR addition to JP-5. Moreover, CO emissions at the SBR NTC region (773–823 K) gradually increased more than at any other tested Tini. Meanwhile, the measured ID periods and NTC characteristics for SBR were replicated using a reduced mechanism of 106 species and 2,162 reactions. The reduced mechanism also predicted the measured SBR inhibition effect on the ID periods for JP-5.