Performance tuning of IC engine with variable exhaust system using a one-D simulation tool
1 online resource (85 pages) : PDF
University of North Carolina at Charlotte
The exhaust system has a significant effect on the breathing capability of an IC engine, which when increased, increases the volumetric efficiency. Due to the sudden opening of the exhaust valve, the highly pressurized gases in the combustion chamber rush out creating a pressure wave. When the low pressure wave is made to return at the time of exhaust valve opening, the evacuation of exhaust gases improve. This is due to the higher pressure differential that is created by the low pressure wave. Using this principle, the exhaust system was tuned with a one-D simulation tool to achieve higher scavenging efficiency. However, as the engine speed changes the requirements to achieve the tuned condition changes and also the strength of the wave decreases for every reflection. With a variable runner length system the higher engine speeds use the first reflection and lower engine speeds are shifted to use later low pressure wave reflections. Tuning the exhaust valve timing along with the runner length further improved the performance. With tuned runner length and valve timing 1-2% and 5-8% improvement was seen in brake torque at higher and lower engine speeds respectively. Increase in valve lift, where low pressure wave is taken advantage of, increased torque by another 1-2%. However, when the compression wave returns at EVO, low lift reduced the negative effect of the compression wave. With 20% less lift, almost 50% of the loss incurred due to shifting between reflections was reduced. Overall, 2-3% and 7-10% improvement in torque was achieved with variable runner length and valve train system at higher and lower engine speeds respectively.
1D MODELEXHAUSTPRESSURE WAVERUNNER LENGTHVALVE LIFTVALVE TIMING
Uddin, MesbahBari, SaifulTkacik, Peter
Thesis (M.S.)--University of North Carolina at Charlotte, 2017.
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