DESIGN AND PERFORMANCE OF A VARIABLE VALVE TIMING SYSTEM ON A HIGHLY TURBOCHARGED DIESEL-ENGINE - EXPERIMENTAL AND PREDICTED RESULTS

A previous study using a cycle simulation program had identified the p ossibility that highly rated diesel engines might benefit from a varia ble valve timing (VVT) system. In particular, the study had shown that , by delaying the start of inlet valve opening at part load, it should be possible to eliminate the reverse flow that can lead to inlet port fouling. The work reported here encompasses the design and implementa tion of a variable valve timing system on a highly rated high-speed ma rine diesel engine. The principal topics addressed are the selection a nd design of a mechanism, a comparison between the predictions and res ults from mechanism testing on a single-cylinder valve-train rig and t he engine performance predictions and results obtained when the mechan ism was tested on the engine. The results from the single-cylinder tes t rig demonstrated that the mechanism performed satisfactorily, and th is led to a design suitable for retro-fitting to the engine. The engin e was comprehensively instrumented and the experimental results were i n good agreement with the cycle simulation predictions.