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ME433 Project: Variable Compression Ratio Engine Systems

ME433 Project: Variable Compression Ratio Engine Systems. Anthony Crawford Ph.D., P.E. Compression ratio. Knock Limits Compression Ratio. Ways to mitigate knock Higher octane fuel Sophisticated control system Reduced compression ratio. Theoretical VCR Benefit.

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ME433 Project: Variable Compression Ratio Engine Systems

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  1. ME433 Project:Variable Compression Ratio Engine Systems Anthony Crawford Ph.D., P.E.

  2. Compression ratio

  3. Knock Limits Compression Ratio • Ways to mitigate knock • Higher octane fuel • Sophisticated control system • Reduced compression ratio

  4. Theoretical VCR Benefit • Engine Efficiency (Envera 2.2L VCR I4, a 3.6L turbo-DI V6, and a 5.7L V8 ) • Torque/Power Improved at below WOT levels

  5. Various VCR Systems ++ very low negative impact + low negative impact o moderate impact - high negative impact -- very high negative impact

  6. VCR that adjust the clearance volume without modifying the TDC • Secondary piston • Changes clearance V ++ very low negative impact + low negative impact o moderate impact • high negative impact • -- very high negative impact

  7. VCR that adjust the clearance volume without modifying the TDC • Rotation • Moves cylinder up ++ very low negative impact + low negative impact o moderate impact • high negative impact • -- very high negative impact

  8. VCR that adjust the clearance volume without modifying the TDC • Translation • Moves cylinder up ++ very low negative impact + low negative impact o moderate impact • high negative impact • -- very high negative impact

  9. VCR that adjust the clearance volume by modifying the TDC • Linkage • Adjust base pivot or link length to affect TDC ++ very low negative impact + low negative impact o moderate impact • high negative impact • -- very high negative impact

  10. VCR that adjust the clearance volume by modifying the TDC • Rocking • Movement on one side generates opp. movement in piston ++ very low negative impact + low negative impact o moderate impact • high negative impact • -- very high negative impact

  11. VCR that adjust the clearance volume by modifying the TDC • Elastic component • Elastic components compress at higher pressures thus reducing clearance volume and reducing compression ratio at higher loads

  12. VCR that adjust the clearance volume by modifying the TDC • Eccentric pivots • Effectively adjusts link lengths ++ very low negative impact + low negative impact o moderate impact • high negative impact • -- very high negative impact

  13. Conclusions • VCR systems have the promise to increase: • engine efficiency/power/torque • operate with multiple cycles • adjust to accommodate knock limitations of various fuels. • Multiple VCR systems each have their own advantages and disadvantages with regard to: • effectiveness • complexity • ability to be integrated into current engines

  14. Key References • Pischinger, S., et. al. “Two-stage Variable Compression Ratio with Eccentric Piston Pin,” MTZ Worldwide Edition, 2009-02. • Mendler, C., “Envera Variable Compression Ration Engine,” US DOE report DE-FC26-05NT42484, March 15, 2011. • Aina, T., et. al. “Influence of compression ratio on the performance characteristics of a spark ignition engine,” Advances in Applied Science Research, 3 (4): 1915-1922, 2012.

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