The effect of HDPE and LDPE pyrolytic oils on cavitation formation in a common-rail diesel injector

Abstract

Plastic production and usage increase every year due to its practicality, adaptability, and low-cost production. The problem with plastic arises when it becomes waste and needs to be treated. Most of the plastic we use is produced from petrochemical material that can be used in resource recovery processes like pyrolysis to produce various materials. One of the pyrolysis process products is pyrolytic oil, whose properties are similar to conventional fuels. Minor differences in fuel properties can influence the injection process, in-nozzle flow condition, spray formation and break-up, the combustion process, etc. The presented paper aims to study the influence of pyrolytic oil‘s properties on cavitation formation in the injection nozzle of a common-rail injector. First, the pyrolytic oils were obtained from waste high- and low-density polyethylene using a pyrolysis reactor. Afterwards, the oils were characterized and implemented in the AVL FIRE computation program for studying their influence on cavitation formation in the injection nozzle hole. The obtained results indicate slight differences in fuel properties that influence cavitation formation and spread in the injection hole, which further influence conditions at the exit of the injection hole. The lower lower viscosity of pyrolytic oils influences lower friction in the fuel nozzle flow. The lower density and viscosity of pyrolytic oils promotes cavitation formation, advance time of it appearance at injection hole exit and influence the shorter presence of cavitation in the needle closing phase.