improved engine design concepts using the second law of ......2008 doe merit review bethesda, md...

2008 DOE Merit Review Bethesda, MD

Improved Engine Design Concepts Usingthe Second Law of Thermodynamics Contract No. DE-FC26-05NT42633 (NT42633)

J. A. Caton Texas A&M University

26 February 2008

This presentation does not contain anyproprietary or confidential information.

Texas A&M University E3 Laboratory

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2008 DOE Merit Review

Improved Engine Design Concepts Usingthe Second Law of Thermodynamics

Presentation Outline

♦ Purpose of Work

♦ Previous Comments

♦ Barriers

♦ Approach

♦ Accomplishments

♦ Technology Transfer/Publications/Patents

♦ Plans for Next Fiscal Year

♦ Summary


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Purpose of Work

♦ Develop engine cycle simulations

♦ Examine engine concepts which will –

• reduce combustion irreversibilities

• increase thermal efficiency

• maintain or lower emissions

♦ Develop and use simplified systems

• isolate combustion processes


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--------------

2008 DOE Merit Review Previous Comments:

Summary Comments:

“An excellent approach to help guide improvements in engine efficiency.”

“A stronger connection with industry should be developed so that the power of this technique is brought to bear on improving the design of new engines.”

New Actions:

Will develop stronger ties to industry –

different ideas for these collaborations

invitation …


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Technical Barriers:

♦No generic technical barriers for project


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Approach: Thermodynamic System and Analyses Techniques

♦ An engine cycle simulation based on the first law of thermodynamics is used.

♦ The analysis is extended to include the second law – availability (exergy)

♦ Key features include detailed properties, multiple zones for combustion, and availability computations


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Accomplishments ♦Simplified Systems to Isolate Combustion Irreversibilities

♦Parametric studies for constant volume and constant pressure systems

♦Hypothetical “reversible” combustion processes for reciprocating devices

♦ Spark-Ignition Engines (most recent studies) ♦More realistic EGR sub-models

♦Effects of compression ratio

♦Effects of expansion ratio (over expanded engines)

♦ Diesel Engine Studies (initial results)


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List of Previous Studies

♦Effects of engine speed and load

♦Effects of equivalence ratio

♦Effects of combustion duration, timing and schedule

♦Effects of the use of EGR

♦Effects of oxygen enrichment of inlet air

♦Effects of the use of hydrogen

♦Effects of compression ratio

♦Effects of expansion ratio (over-expanded engines)


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Three Examples of Results from this Work

1. SI Engine with EGR

2. Use of Over-Expanded Engines

3. Preliminary Diesel Engine Results


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Engine Cycle Simulation:EGR Sub-Model Improvements

Parametric Study


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Engine Cycle SimulationImproved EGR Model

EGR (%)

Effi

cien

cy/M

ax E

ff

0 10 20 30 400.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

♦ Combustion “termination” for higher levels of EGR helped match experimental results

Wedge C

hamber G

MR

Modified Chamber GMR

Cooled

andAdiabatic

EGR

Our C

ase

Improved EGR sub-model –

♦ Longer burn duration (while maintaining optimum timing) for higher levels of EGR not too significant


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Engine Cycle Simulation: Improved EGR ModelAdiabatic EGR Configuration

AVA

ILA

BIL

ITY

(%)

100%

80%

60%

40%

20%

0%

30.08 30.93 Work

23.12 23.14 Heat Transfer

24.28 21.39 Net Transfer out

20.52 19.31 Destroyed by Combustion

Due to Flow

Total Indicated

Destruction due Unused Fuel Unused Fuel Destruction due

(0.78) to Inlet Mixing

(1.35) to Inlet Mixing (0.66) (4.44)

0% EGR 20% EGR


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Engine Cycle Simulation: Improved EGR ModelCooled EGR Configuration

Destruction due to Inlet Mixing

100%

80%

60%

40%

20%

0%

Unused Fuel Unused Fuel Destruction due to Inlet Mixing(0.66) (4.45)

(1.13) A

VAIL

AB

ILTY

(%)

30.08 31.14

23.12 19.47

24.28 22.8

20.52 21.01

Destroyed by Combustion

Net Transfer out Due to Flow

Heat Transfer

Total Indicated Work

(1.35)

0% EGR 20% EGR


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Engine Cycle SimulationImproved EGR Model

Second Law Results – Load and Speed2222

1400 rpmEqui. Ratio = 1.0spark = "MBT"

EGR = 20% Cooled

EGR = 0%

"WOT"

"WOT"

"WOT"

EGR = 20% Adiabatic

1000 2000 3000 4000 5000 6000 7000

EGR = 20% Cooled

bmep = 325 kPaEqui. Ratio = 1.0spark = "MBT"

EGR = 20% Adiabatic

EGR = 0%

Des

truct

ion

of A

vaila

bilit

y by

Com

bust

ion

(%)

21

20

19

Con

bust

ion

Des

truct

ion

of A

vaila

bilit

y(%

)

21

20

19

18

17180 200 400 600 800 1000

bmep (kPa) Engine Speed (rpm)


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Effects of Expansion Ratio

(for a constant compression ratio)

a novel engine mechanism needed


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“Atkinson” CycleAssumptions/Approximations

� Piston motion is assumed to be approximated by superimposed motions of the classic “slider-crank” mechanism

� Clearance volume based on compression ratio

� Mechanical friction based on either compression or expansion ratio (details depend on mechanism)

� Engine performance parameters such as bmep based on stroke of the compression process for the displaced volume


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Cylinder Volume for “Atkinson” Cycle


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Brake Thermal Efficiency vs Expansion Ratio- Part Load -

¾ Note: results for constant part load – must adjust throttle to maintain load

¾ For these conditions, modest gains of brake thermal efficiency

¾ For higher than optimum expansion ratio, the efficiency decreased due to increase heat transfer (more surface area) and ineffective exhaust processes


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Brake Thermal Efficiency vs Expansion Ratio- Wide Open Throttle (WOT) Cases -

¾ Compared to the previous part load cases, WOT results in much more improvement as the expansion ratio increases

¾ The efficiency increases about 10% from no over-expansion (i.e., ER = CR) to the optimum expansion ratio

¾ Next: Cylinder pressures and flows


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Example of WOT Pressures and Flows


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Availability Destruction due to

Combustion for WOT Conditions

¾ Very slight increase in the availability destruction due to combustion – this is largely a result of the modest changes in temperatures

¾ For part load, the changes were even less – the average destruction was about 21.8% (lower temperatures than for the WOT cases)


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Summary of Diesel Results

Parameter Conventional Diesel

LTC Diesel

Engine Speed 1500 rpm 1500 rpm Inlet Pressure 105 kPa 92 kPa Engine Load, bmep 393 kPa 417 kPa Equivalence Ratio 0.387 0.843 Exhaust Gas Recirculation 0.0 % 41.9% Burn Duration (0 – 100%) 24.0°CA 28.0°CA Start of Combustion Timing –7.0°aTDC 4.5°aTDC Peak Pressure 6836 kPa at

9°aTDC 3764 kPa at

22°aTDC Peak Average Temperature 1678 K at

13°aTDC 1710 K at 28°aTDC

Brake Thermal Efficiency 33.4% 32.6% EI-NOx 30 g/kgf 0.2 g/kgf

EI-PM 0.17 g/kgf 0.03 g/kgf

HC 220 ppm (C1) 1880 ppm (C1) CO 240 ppm 4460 ppm


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1 2

Overall Energy Values

ENER

GY

(%)

0

20

40

60

80

100

(33.4%)

(10.6%)

(25.1%)

Other

(18.5%)

(9.5%)

(32.6%)

Brake Work

Heat Transfer

Exh Flows (38.9%) (29.0%)

Friction

Conventional LTC 0% EGR 42% EGR


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1 2

Overall Availability Values

AVAI

LAB

ILIT

Y (%

)100

80

60

40

20

0 (42.4%)

(20.7%)

(9.3%)

Other

(18.8%)

(15.0%)

(40.8%)

Total Indicated

Work

Heat Transfer

Exh Flows

(24.0%) (24.5%) Destruction

Burned

Conventional LTC 0% EGR 42% EGR


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Technology Transfer/Publications/Patents1. H. Sivadas and J. A. Caton, “Effects of Exhaust Gas Recirculation on Exergy Destruction due to

Isobaric Combustion for a Range of Conditions and Fuels” accepted for publication, International Journal of Energy Research, 29 November 2007.

2. J. A. Caton, “Results from an Engine Cycle Simulation of Compression Ratio and Expansion Ratio Effects on Engine Performance,” accepted for publication, ASME Transactions — Journal of Engineering for Gas Turbines and Power, 07 November 2007.

3. J. A. Caton, “The Effects of Compression Ratio and Expansion Ratio on Engine Performance Including the Second Law of Thermodynamics: Results from a Cycle Simulation,” in Proceedings of the 2007 Fall Conference of the ASME Internal Combustion Engine Division, Charleston, SC, 14–17 October 2007.

4. P. S. Chavannavar, and J. A. Caton, “The Destruction of Availability (Exergy) due to Combustion Processes: A Parametric Study,” Journal of Power and Energy, Proceedings of the Institution of Mechanical Engineers, Part A, vol. 220, number 7, pp. 655–669, 2006.

5. J. A. Caton, “Utilizing a Cycle Simulation to Examine the Use of EGR for a Spark-Ignition Engine Including the Second Law of Thermodynamics,” in Proceedings of the 2006 Fall Conference of the ASME Internal Combustion Engine Division, Sacramento, CA, 5–8 November 2006.

6. J. A. Caton, “First and Second Law Analyses of a Spark-Ignition Engine Using Either Isooctane or Hydrogen,” in Proceedings of the 2006 Fall Conference of the ASME Internal Combustion Engine Division, Sacramento, CA, 5–8 November 2006.

7. J. A. Caton, “The Effects of Exhaust Gas Recirculation (EGR) for a Spark-Ignition Engine: A Second Law Analysis,” in Proceedings of the 2006 Spring Meeting of the Central States Section of the Combustion Institute, Cleveland, OH, 21–23 May 2006.

8. P. S. Chavannavar and J. A. Caton, “Irreversibilities Associated with Basic Combustion Processes,” in Proceedings of the 2006 Spring Meeting of the Central States Section of the Combustion Institute, Cleveland, OH, 21–23 May 2006.


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Technology Transfer/Publications/Patents

Theses and Dissertations 1. Rajeshkumar Shyani, “An Investigation of the Use of EGR for Spark-Ignition Engines: Using an

Engine Cycle Simulation,” MSME, expected May 2008.

2. Sushil Oak, “Use of an Engine Cycle Simulation to Study Diesel Engine Combustion,” MSME, expected May 2008.

3. Hari Sivadas, “The Effects of EGR, Water/N2/CO2 Injection, and Oxygen Enrichment on the Availability Destroyed Due to Combustion for a Range of Conditions and Fuels,” MSME, August 2007.

4. Kaushik T. Patrawala, “An Examination of Possible Reversible Combustion at High Temperatures and Pressures for a Reciprocating Engine,” MSME, May 2007.

5. Dushyant Pathak, “Use of a Thermodynamic Cycle Simulation to Determine the Difference Between a Propane-Fuelled Engine and an Iso-Octane-Fuelled Engine,” MSME, December 2005.

6. Praveen Chavannavar, “Parametric Examination of the Destruction of Availability Due to Combustion for a Range of Conditions and Fuels,” MSME, August 2005.


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Plans for Next Fiscal Year

♦ Complete diesel engine studies using the extended engine cycle simulations

♦ Use the extended engine cycle simulations to investigate engine performance for a wide range of operating conditions

♦ Use the extended engine cycle simulations to design engine concepts for reductions of engine irreversibilities


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Summary

♦ Work has been completed for simple systems, SI engines and CI engines.

♦ A new sub-model for EGR for SI engines has been developed and used in a series of parametric studies.

♦ The effects of compression ratio and expansion ratio have been documented. Over expanded engines have modest potential for full load operation, but minimal advantages at part load.

♦ New studies of diesel engines have been initiated. Preliminary results for second law parameters have been obtained.


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improved engine design concepts using the second law of ......2008 doe merit review bethesda, md...

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