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					N Ox Emissions Reduction of a Natural Gas SI Engine
   under Lean Conditions:
    Comparison of the EGR and RGR concepts



Olivier LE CORRE
                E.M.N. - FRANCE


Frédéric PIROTAIS
                   I.N.P.G. - FRANCE


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     Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                       INTRODUCTION
CHP fuelled by NG
     - good thermal efficiency
     - smaller impact on global warning
            high H/C ratio limits CO2 emission
  Nevertheless
      - high emission level of UHC
                                            Sogaard et al.

Main advantages of a hydrocarbon and hydrogen blend
     - increases thermal efficiency
     - reduces UHC, CO, CO2 emissions
                                             Tsolakis et Megaritis
   Nevertheless
     - NOx emissions raising
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      Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                       INTRODUCTION

Hydrogen: fuel for the future?

  Unfortunately

  Hydrogen production and storage are difficult
                                                   Hoekstra

Idea : in-situ fuels reforming
                                                   Zheng et al.




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      Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                     RGR Concept
                                           H2O, CO2, N2




                         500-550°C




                           H2, CO, N2

                                                                 4
Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                      Table of contents



1/ SI engine
      Thermodynamic model
      Test bench

       2/ Reformer
            Model
            Bibliography

               3/ Feedback loop

                        4/ Conclusion and perspectives


                                                                  5
 Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                      Table of contents



1/ SI engine
      Thermodynamic model
      Test bench

       2/ Reformer
            Model
            Bibliography

               3/ Feedback loop

                        4/ Conclusion and perspectives


                                                                  6
 Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
       Two-zone thermodynamic model



                     - fresh and burnt gases
                     - an uniform in-cylinder pressure
                     - both leakage and blow-by are neglected

                     - burnt mass fraction, see Chelma

                     - laminar speed of blend, see
                     Shahad Al-Janabi and Sadi Al-Baghadi

                     - wall heat transfer, see Hohenberg




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Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                      Test Bench


                      Designation           Testing Bench
                                            Turbo-charged
                      Displacement Volume   17 964 cm3
                      Number of cylinders   6
                      Bore B                152 mm
                      Con. Rod length L     300 mm
                      Stroke S              165 mm
                      Intake opens          25°BTC
                      Intake closes         45°ABC
                      Exhaust opens         60°BBC
                      Exhaust closes        15°ATC
                      Engine Speed          1500 RPM




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Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
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Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                       S.I. engine




        Good agreements between
numeric simulations and experimental tests
                                                                  10
 Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                      Table of contents



1/ SI engine
      Thermodynamic model
      Test bench

       2/ Reformer
            Model
            Bibliography

               3/ Feedback loop

                        4/ Conclusion and perspectives


                                                                  11
 Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                            Reformer : model at equilibrium
Reforming kinetic
                                     k1                              
Co-production from CH4                                      3
                                                          p H 2 pCO
CH 4  H 2 O  CO  3H 2                  p                          
                                             CH 4 p CO2 
                                    p H.5 
                                      2
                                        2 
                                                              K1      
                                                                      
                               r1 
                                                  DEN 2

                                    k2                                   
Water-gas shift                                            p H p CO2
CO  H 2 O  CO 2  H 2                                                  
                                          p CO p H 2O        2
                                                                          
                                   pH                          K2        
                                       2                                 
                              r2 
                                                 DEN 2
Production of CO2 from              k3                                   
                                                              2
                                         p                 p H 2 p CO    
                                            CH 4 p H 2 O 
                                                   2
CH4
                                   p H.5 
                                     3
                                       2 
                                                                 K3       
                                                                          
CH 4  2 H 2 O  CO 2  4 H 2 r3 
                                                 DEN 2



See Xu and Froment




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                Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                                    Reformer : plug flow
Reformer data
Length of reformer tube              0.3 m
Inside diameter of reformer tube     0.10 m
Outside diameter of reformer tube    0.13 m

Catalyst data
Catalyst Pellet dimension            17 x 8 x 10 mm
Pellet porosity                      0.5
Pellet equivalent diameter           7.5 mm
Pellet tortuosity                    3.54
Solid catalyst density               2355 kg/m3
Catalyst bed density                 1170 kg/m3




                                                                              13
             Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
             Reformer results
        comparison with bibliography



                   Allenby




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Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                      Table of contents



1/ SI engine
      Thermodynamic model
      Test bench

       2/ Reformer
            Model
            Bibliography

               3/ Feedback loop

                        4/ Conclusion and perspectives


                                                                  15
 Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                    Feedback loop




                                                                 16
Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                      Table of contents



1/ SI engine
      Thermodynamic model
      Test bench

       2/ Reformer
            Model
            Bibliography

               3/ Feedback loop

                        4/ Conclusion and perspectives


                                                                  17
 Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany
                Conclusion and Perspectives



Blend of Reformed Gas Recirculation and Natural Gas :
an opportunity to optimise the CHP engines

Nevertheless,

under very lean conditions, misfire occures and leads
cycle to cycle dispersions.

On one hand, hydrogen improves flame propagation
BUT, on the other hand very lean conditions reduce it.



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       Spring Technical Conference, May 8 – 10, 2006, Aachen, Germany

				
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