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F. BOZZA, A. GIMELLI Dept. of Mech. Eng. (DIME) Univ. of Naples “Federico II”, ITALY E. TORELLA

Diagnostics in Automotive Engines and Vehicles MECA ’02 Dept. of Mech. Eng. - University of Salerno October 4th 2002. F. BOZZA, A. GIMELLI Dept. of Mech. Eng. (DIME) Univ. of Naples “Federico II”, ITALY E. TORELLA ELASIS S.C.p.A, ITALY.

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F. BOZZA, A. GIMELLI Dept. of Mech. Eng. (DIME) Univ. of Naples “Federico II”, ITALY E. TORELLA

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  1. Diagnostics in Automotive Engines and VehiclesMECA ’02 Dept. of Mech. Eng. - University of Salerno October 4th 2002 F. BOZZA, A. GIMELLIDept. of Mech. Eng. (DIME) Univ. of Naples “Federico II”, ITALY E. TORELLA ELASIS S.C.p.A, ITALY The Potential of 1D Simulation Models in Control Applications of VVT Engines

  2. Introduction MECA’02 Workshop, Oct 2002 VVT VVA Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.2 • Intake (and exhaust) Variable Valve Timing (VVT) is nowadays commonly used in the standard SI Engine production (cam phasers): • Variable Valve Actuation (VVA) systems will be moreover adopted in the next SI engine generation (Electro-magnetic actuators): • Improvements on output performance at WOT and on BSFC and NOx emission at part-load have been assessed

  3. Motivation MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.3 • With themost advanced VVA devices, an increased number of parameters must be controlled by the EMS: Spark Adv.,Throttle,A/F, IVO,IVC,EVO,EVC,IVL,EVL traditional ctrl’d parameters,valve-train arrangementparams • It is really difficult to characterize the engine behavior through a classical experimental analysis • The number of experimental tests to be conducted, is exponentially growing accordingly to the rising number of setting variables

  4. Motivation MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.4 • Some difficulties also arise when a simple cam phaser system is employed (only one additional control parameter) • In this case, a different experimentally derived volumetric efficiency map must be employed within traditional speed-density procedure for predicting the port air mass flow • This depends on both the different development of the wave propagation phenomena in the external ducts, as well as on valve backflows, causing “internal EGR”

  5. Experimental data MECA’02 Workshop, Oct 2002   Exh Int Miminum Load Line  = 50 deg Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.5 Phased Intake & Exhaust VVT Engine Volumetric Efficiency Contours  = 0 deg Engine: CBR 1400 16v

  6. Objective MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.6 • Problem: • Variable Valve devices require additional experimental efforts to develop the Engine Management System, with a considerable penalty on costs and time-to-market of new engines • The employment of an accurate 1D simulation model to help the development of the EMS and reduce the demandof experimental data • Development of two examples aiming to show the “ Potential of the 1D Simulation Models in Control Applications ” • Proposed solution: • Test - cases:

  7. Summary MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.7 • Brief description and validation of the 1D code • First example: Control-Laws of various VVA devices are derived through the matching of the 1D code with a numerical optimization procedure • Second Example: A Correlation of volumetric efficiency with some easily measurable parameters is derived, basing on “pseudo-experimental” data generated with the 1D code

  8. MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.8 Simulation Model 1Dime • 1D Flow model: • Finite Volume numerical scheme coupled to a flux correction TVD (Total Variation Diminishing) technique. • Eqs. for the scalar transport of chemical species (unburned fuel, xf, and burned products, xr, fractions) for a correct computation of in-cylinder composition (the presence of “internal EGR” is then accounted for)

  9. Simulation Code MECA’02 Workshop, Oct 2002 Burned Gas SL u’ L SL Unburned Gas SL Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.9 1Dime • Combustion, Turbulence and Emission Model • Fractal Approach: the turbulent flow field wrinkles the flame front, which assumes fractal characteristics: • Fractal dimension and wrinkling scales depend on turbulence intensity, computed with k-K model • Multi-zone approachfor NOx Emission computation, frozen equilibrium assumption for CO estimation, crevices and partial-burn mechanisms for HC production

  10. Experimental Analyses MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.10 Two Engines were tested at ELASIS: • A traditional fixed-valve engine (Fire 1242 16v) • A phased intake & Exhaust VVT Engine (CBR 1400 16v) CBR 1400 16v Sketch of the Port-Deactivation System employed to promote the burning speed at high EGR rate

  11. Boundary Conditions MECA’02 Workshop, Oct 2002 Dp Exhaust mass flow rate Slider Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.11 CBR 1400 16v • Only Input Data: • Throttle Opening • Rotational Speed • Air/Fuel Ratio • Spark Advance • VVT Position • Ambient Conditions 1D Geometrical representation:

  12. Validation MECA’02 Workshop, Oct 2002 CO Emission NO Emission Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.12 Traditional fixed-valve engine (Fire 1242 16v) IMEP Air-Flow

  13. Validation MECA’02 Workshop, Oct 2002  = 50 deg Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.13 Phased intake & Exhaust VVT Engine (CBR 1400 16v)  = 0 deg  = 28 deg

  14. Validation MECA’02 Workshop, Oct 2002 EXP NUM Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.14 CBR 1400 16v  = 0 deg

  15. Validation MECA’02 Workshop, Oct 2002 EXP NUM Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.15 CBR 1400 16v  = 50 deg

  16. Validation MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.16 • A limited validation of the 1D whole engine models is frequently found in current literature (only at WOT for example) • The 1Dime model is indeed able to well describe whole engine operation, including low load, idle or high EGR conditions • Model derived engine operating maps can be employed in a number of control applications (static look-up tables) • A great potential there exist for a significant reduction of the experimental efforts required for the EMS

  17. First Example MECA’02 Workshop, Oct 2002 • Intake only VVT ( = spark advance) ( = phase position) • Phased Intake & Exhaust VVT • Unphased Intake & Exhaust VVT • Early Intake Valve Closure (EIVC) ( = scale factor)  Exh Int   Exh Int I E Exh Int s Exh Int Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.17 • An optimization procedure, coupled to the 1D model, can identify the values of the independent variables (vector X) which minimize the BSFC, for 4 different VVT / VVA devices:

  18. First Example MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.18 • At each fixed engine operating condition (in terms of throttle opening *, speed n*, A/F ratio, external conditions)the following mathematical problem can be formulated: • “Optimal Control Laws” of the VVT devices were derived through repeated solutions of the above problem at different load levels (at a constant speed of 2250 rpm) • The objective function can also include inequality constraints (ALF formulation) on emission, or it can be evaluated on few representative points of the test cycles (NEDC, FTP, etc.)

  19. Optimization Results MECA’02 Workshop, Oct 2002  Exh Int   Exh I E Exh Int Int s Exh Int Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.19 2250 rpm BSFC percent Variation

  20. Control Laws MECA’02 Workshop, Oct 2002 I E Exh Int s Exh Int Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.20 Unphased Int.&Exh. EIVC

  21. Second Example MECA’02 Workshop, Oct 2002 EXP NUM Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.21 Phased Intake & Exhaust VVT Engine Vol. Eff. Iso-Contours • A different volumetric efficiency map arises at each VVT position • Can these maps be synthesized in a single correlation? • Model based Vol.Eff. mapswere built at =[0,15,30,35,40,45,50] • Each map consisting of 64 points, 448 “pseudo-experimental” data were generated at standard ambient conditions

  22. Vol. Eff. Correlation MECA’02 Workshop, Oct 2002 Vol.Eff0 from Correlation Vol.Eff0 from 1D Model Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.22 • Numerical data were correlated as a function of Engine speed (rpm), manifold pressure (MAP) and phase delay (VVT) • A non linear regression technique provided the values of the 10 constants of the 2nd order polynomial model function

  23. Vol. Eff. Correlation MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.23 • To take into account the effects of ambient conditions, additional simulations were carried out in a single operating condition (2000 rpm, 2 bar BMEP) • A slightly correction was required with respect to the expected linear dependence on (T/p) term, to take into account sound speed variations and heat losses

  24. Vol. Eff. Correlation MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.24 • The comparison on TRUE experimental data at various phase positions furnished good results: Vol.Eff from corrected correlation Experimental Vol.Eff.

  25. Conclusion MECA’02 Workshop, Oct 2002 Black-Box White-Box Grey-Box F&E Models 1D Models Exp. Data Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.25 • The two examples presented have shown the great potential offered by the 1D models in different control applications • The methodology is applicable to various VVA concepts and can certainly help a more rapid development of the EMS • Computing power of modern PC can allow to directly follow the unsteady behavior of the engine during a complete drive cycle • A “brighter” future seems near to come in control applications…

  26. MECA’02 Workshop, Oct 2002 Bozza, et al., DIME, Napoli, The Potential of 1D Simulation Models ... Pag.26 Optimization Results

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