Variable Valve Actuation Strategies for Improving Aftertreatment System Efficiency in Modern Diesel Engines Over the Heavy-Duty Federal Test Procedure Certification Cycle
Diesel engine aftertreatment thermal management is accomplished through two different strategies: get-hot when the aftertreatment is cold and stay-hot when the aftertreatment is at operating temperatures for efficient emission conversions. Get-hot utilizes high flow rates and temperatures to increase the aftertreatment systems temperatures at the expense of fuel consumption and stay-hot requires high temperatures in a fuel-efficient manner for increased aftertreatment performance. This study investigates the benefits of half-engine non-fired 2-stroke operation to increase the exhaust flow rates for aftertreatment get-hot. For aftertreatment stay-hot, reverse breathing strategies are compared to conventional aftertreatment strategies as well as cylinder deactivation. This study includes an investigation of a specific operating condition when compressor surge can be instigated through cylinder deactivation during engine motoring events following high-load operations. It is found that half-engine non-fired 2-stroking can decrease the time for the SCR to reach 150 deg C by 33%. 2-cylinder non-fired reverse breathing can match half-engine cylinder deactivation's fuel consumption and cumulative NOx over the HD-FTP when applied at a loaded idle condition. Cylinder deactivation has also been found to instigate deep “decel'” compressor surge when deactivating cylinders during motoring events following high load operation. An algorithm to predict and prevent compressor surge has been developed and validated in this study. Some of the methodology and results for the compressor surge mitigation section has been omitted due to pending IP work.
Shaver, Purdue University.
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