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Valve Method Cuts Engine Emissions Boosts Combustion

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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. In recent years a technique called variable valve actuation (VVA) was introduced that uses an electronically controlled solenoid to open and close valves. Unlike the mechanical cam system VVA allows valves to be opened at chosen times and to varying degrees during the combustion cycle. This technique could be leveraged to help both SI (spark ignition or gasoline) engines and CI (compressed ignition or diesel) engines meet stringent emissions standards. UW–Madison researchers have developed a way to exploit the flexibility of VVA and 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. Briefly opening the valves at these times promotes turbulence and more fuel-air mixing in the combustion chamber 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 the loss of combustion chamber pressure (and thus engine power) while the valves are open the length of time they are open can be minimized easily with VVA. Technology Applications: Reduction of emissions from internal combustions engines

Benefits:

1) Promises to reduce soot emissions by accelerating soot oxidation prior to the exhaust stroke 2) Allows control over ignition timing by tailoring chamber pressure 3) Provides a much simpler and less expensive method to promote combustion chamber mixing than previous technologies 4) Could help diesel engines meet tough emission standards without the need for after-treatment devices 5) Can be readily implemented with other emission control technologies such as those that reduce nitrogen oxides 6) May potentially increase fuel economy 7) Applicable to any internal combustion engine (SI or CI)

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