Experimental Study of Ignition and Combustion Characteristics of Dieseline Spray in Supercritical State

Abstract

AbstractIn present study, supercritical spray combustion and conventional (non-supercritical) spray combustion processes are analyzed at same operating conditions inside direct-injection constant-volume combustion chamber under very lean burning conditions using various sensors. Ignition delay and duration of combustion during each combustion process are compared at same operating conditions. Dieseline blend (50% diesel and 50% gasoline by v/v) is used for supercritical spray combustion study. It is found that ID of SC sprays are significantly smaller than ID of liquid diesel sprays at all operating conditions. At all operating conditions, percentage reduction of ID is above 80% in SC sprays than liquid diesel sprays. It is found that nominal decrease in ID of SC sprays occurs with increase in CP and IP. DOC of SC sprays is remarkably smaller than DOC of liquid diesel spray at all operating conditions. At all operating conditions, percentage reduction in DOC is above 60% in SC sprays as compared to liquid diesel sprays. DOC of SC sprays is greatly affected by IP and effect of CP on DOC is nominal. It is found that SC spray combustion mainly occurs as hot air combustion rather than hot surface ignition. Reduction of ID and DOC in SC spray combustion causes reduction in NOX and smoke formation, respectively. Hence, SC spray combustion is a homogeneous, faster, and clean combustion than normal droplet spray combustion. SC spray injection and combustion technology is a clean combustion technology for automotive engines, which significantly reduce emissions and consequently improve human health. KeywordsIgnition and combustion characteristicsSupercritical and conventional spray combustionConstant volume combustion chamberSensors