Combustion and soot formation characteristics of homogeneous supercritical sprays of dieseline blend in constant volume chamber

Abstract

In present work, combustion and soot formation characteristics of supercritical (SC) sprays are studied in a cylindrical constant volume combustion chamber under diesel engine-like experimental conditions. Hot surface temperature range (673 K to 723 K), initial cylinder pressure range (2 MPa to 4 MPa) and injection pressure range of 10 MPa to 30 MPa are the experimental conditions. Photo sensor and piezoelectric sensors are employed for indicating combustion and injection events respectively. Commercial diesel fuel and dieseline blend are employed for analyzing combustion of normal diesel and SC sprays respectively. It is investigated that duration of combustion of SC sprays are substantially lower than normal diesel sprays at all experimental conditions. Percentage reduction in DOC of SC sprays as compared to diesel sprays is above 35% for all cases. Percentage reduction in DOC of SC sprays is observed highest at higher IP of 30 MPa. Percentage reduction in soot formation (SF) in SC spray combustion is more than 90% at all operating conditions. At normal diesel engine operating conditions, nearly 82% reduction in DOC and about 96% reduction in SF are found. Combustion of SC sprays seems hot air and single-phase homogeneous combustion unlike that of normal diesel sprays having hot surface ignition/combustion. SC spray injection system proves out to be a faster as well as cleaner combustion technology for future high speed direct-injection engines.