Variable Valve Actuation Method to Enhance Combustion and Reduce Engine Emissions

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In four-stroke engines intake and exhaust valves open during the engine cycle to introduce air into the combustion chamber prior to combustion and to release exhaust gases once combustion is complete. Valves are typically opened and closed by a mechanical cam-drive mechanism with timing dictated by rotation of the engine’s crankshaft. Recently a new technology has been introduced that uses an electronically controlled solenoid to open and close valves. Unlike the mechanical cam system this variable valve actuation (VVA) technique allows valves to be opened at chosen times and to varying degrees during the combustion cycle. UW-Madison researchers have now devised a way to exploit the flexibility of VVA to reduce pollutant emissions from internal combustion engines. Their method employs VVA to open valves not only during the intake and exhaust strokes as in conventional engines but also at optimal times during the compression and/or power stokes. Opening the valves at these times promotes in-chamber turbulence and mixing during combustion resulting in much greater soot oxidation. Any unburned fuel or particulates that escape through open valves via the intake manifold will be ingested during the next engine cycle and thus won’t contribute to emissions. Also to reduce loss of combustion chamber pressure (and thus engine power) during valve opening the length of time the valves are open can be minimized easily with VVA. Technology Applications: Reduction of emissions from internal combustions engines


1) Promises to reduce soot emissions by accelerating soot oxidation prior to the exhaust stroke 2) Provides a much simpler and less expensive method to promote combustion chamber mixing than previous technologies 3) Could allow diesel engines to meet tough new emission standards without the need for after-treatment devices 4) Can be readily implemented with other emission control technologies such as those that reduce nitrogen oxides 5) May potentially increase fuel economy 6) Applicable to any internal combustion engine

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