me433 project: variable compression ratio engine systems anthony crawford ph.d., p.e
TRANSCRIPT
ME433 Project:Variable Compression Ratio Engine Systems
Anthony CrawfordPh.D., P.E.
Compression ratio
cv
cvd
V
VVr
1
11 kr
Knock Limits Compression Ratio
• Ways to mitigate knock– Higher octane fuel– Sophisticated control system– Reduced compression ratio
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
N
mQ
r
KT fLV
3011
2 1 fLV mQr
KP
30
11
1
Various VCR Systems
System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + + + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- oCosts o - -- -- - - o - - --
++ very low negative impact + low negative impact o moderate impact
- high negative impact -- very high negative impact
• Secondary piston– Changes clearance V
VCR that adjust the clearance volume without modifying the TDC
System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + + + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- o
Costs o - -- -- - - o - - --
++ very low negative impact+ low negative impact
o moderate impact-high negative impact
--- very high negative impact
• Rotation– Moves cylinder up
VCR that adjust the clearance volume without modifying the TDC
System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + + + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- o
Costs o - -- -- - - o - - --
++ very low negative impact+ low negative impact
o moderate impact-high negative impact
--- very high negative impact
• Translation– Moves cylinder up
VCR that adjust the clearance volume without modifying the TDC
System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + + + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- o
Costs o - -- -- - - o - - --
++ very low negative impact+ low negative impact
o moderate impact-high negative impact
--- very high negative impact
VCR that adjust the clearance volume by modifying the TDC
• Linkage– Adjust base pivot or link length to affect TDC
System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + + + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- o
Costs o - -- -- - - o - - --
++ very low negative impact+ low negative impact
o moderate impact-high negative impact
--- very high negative impact
VCR that adjust the clearance volume by modifying the TDC
• Rocking– Movement on one side generates opp. movement in piston
System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + - + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- oCosts o - -- -- - - o - - --
++ very low negative impact+ low negative impact
o moderate impact-high negative impact
--- very high negative impact
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
VCR that adjust the clearance volume by modifying the TDC
• Eccentric pivots– Effectively adjusts
link lengths System Criterion
1 2 3 4 5 6 7 8 9 10
Suitability for Cont. CR
Continuous VCR 2-stage VCR
Determination of Actual CR
+ + - + + + - - - -
Chamber Shape
-- ++ ++ ++ ++ ++ ++ ++ ++ ++
Impact on Package
- -- -- -- - - ++ + + +
Modification of Production
o -- -- -- - - + + + +
Oscillating Mass
++ -- -- ++ ++ -- -- + + --
Friction ++ - - ++ - - o + -- oCosts o - -- -- - - o - - --
++ very low negative impact+ low negative impact
o moderate impact-high negative impact
--- very high negative impact
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
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.