Internal Combustion Engine, Numerical Analysis, Unsteady Flow, Scavenging Efficiency

Abstract

A theoretical analysis was made of the transient fuel supply characteristics in a carburetor with secondary slow air bleed under decelerating drive conditions. Time-dependent one-dimensional equations of continuity and motion were derived for describing transient flow of fuel and air in the slow system of a carburetor, being solved by the finite difference method. Experimental work was also performed to verify the validity of the theoretical results. A carburetor under full-throttle operation was suddenly decelerated and the first appearance of fuel discharged from the outlet of idle port was detected by a set of phototransistor and LED. The results showed that the present analysis was successful in giving results consistent with experimental data. The secondary slow air bleed was found to be useful for improving the transient response of a carburetor. Delay time was mostly due to the period of time elapsed for fuel to arrive at emulsion holes of secondary slow air bleed.