Variable Camshaft Valve Timing and its Effects to Hydrous Ethanol (E100) Combustion during Engine Warm up Phase

摘要

In-cylinder airflow has significant impact in mixture formation and burn in internal combustion engines. Exhaust valve closing retard and early intake valve opening have large contribution for the in-cylinder airflow. It may reduce pumping work (energy lost to pump exhaust gases out of the cylinder and to draw the fresh air-fuel mixture), hurt combustion stability due to the excess of residual gas in the combustion chamber or still contribute to cylinder scavenging, increasing the amount of fresh air resulting in higher burn efficiency and more work extracted from the cycle. Brazilian market has large Hydrous Ethanol fuel (E100) usage. Due to E100 fuel properties, the intake and exhaust valves opening and closing time must be carefully defined during the engine warm up phase to avoid negative effects on the combustion. The objective of this work is to analyze the effects in performance, combustion stability and emissions, of exhaust valve timing at different engine temperatures when using E100 fuel in a Ford 1.5L naturally aspirated 3-cylinder engine with Port Fuel Injection (PFI) and dual variable valve timing control. The study shows that it is possible to obtain significant emissions improvements during warm up phase by optimizing exhaust valve timing, without exceeding combustion stability limits.