Electro-pneumatic variable valve actuation system for camless engine: Part I-development and characterization

Abstract

The intake and exhaust valves lift, timing, and duration influence the performance, combustion, and emissions of an internal combustion engine. In this study, an electro-pneumatic variable valve actuation (VVA) system was developed for independent control of the valve motion. The Shadowgraph technique was used to characterize the valve motion, and a high-speed camera was used to capture the valve images. It was observed that by controlling the airflow rate into the pneumatic actuator, different valve lifts were achieved successfully. However, the valve velocity at the end of backward stroke was so high that valve hits the valve seat. Therefore, pneumatic damping was introduced towards the end of backward stroke and valve velocity was reduced when valve comes in contact with the valve seat. Multi-cycle analysis for valve lift and velocity profiles were performed to evaluate cycle-to-cycle variations of the developed actuation system. The results show that the system performs well for both part and full lift conditions with coefficient of variation below 1% and has an acceptable valve seating velocity control. The developed VVA system will be used in Part-II and the effect of un-throttled operation on fuel consumption improvement in a camless engine will be investigated.