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

1. World Congress, March 3-6, 2003 Cobo Center, Detroit, Michigan, USA F. BOZZADept. of Mech. Eng. (DIME) Univ. of Naples “Federico II”, ITALY E. TORELLA ELASIS S.C.p.A, ITALY The Employment of a 1D Simulation Model for A/F Ratio Control in a VVT Engine Paper # 2003-01-0027

2. Introduction SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.2 • With themost advanced VVA devices, an increased number of parameters must be controlled by the Engine Management System (EMS): Spark Adv.,Throttle,A/F, IVO,IVC,EVO,EVC,IVL,EVL traditional ctrl’d parameters,valve-train arrangementparams • It is really difficult to completely characterize the engine behavior through experimental analysis. The number of tests to be conducted is exponentially growing accordingly to the rising number of setting variables • Since some years DIME and ELASIS are collaborating to employ a 1D simulation model to help the development of the EMS and reduce the demandof experimental data

3. Previous Work SAE’03 World Congress, March 2003  Exh Int   Exh I E Exh Int Int s Exh Int Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.3 (results from SAE 2002 -01-1107) BSFC percent Variation 2250 rpm

4. Motivation SAE’03 World Congress, March 2003   Exh Int Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... 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. Motivation SAE’03 World Congress, March 2003   Exh Int Miminum Load Line  = 50 deg Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.5 Phased Intake & Exhaust VVT Engine Volumetric Efficiency Contours  = 0 deg Engine: CBR 1400 16v Experimental data

6. Objective SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.6 • Proposed Solution: • Development of Correlation between volumetric efficiency and some easily measurable parameters, based on “pseudo-experimental” data generated with the 1D code • Proposed solution: • Application:

7. Summary SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.7 • Brief description and validation of the 1D code • Experimental Analysis: • Theorethical Analysis and code Validation: • Correlation Development:

8. SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... 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 SAE’03 World Congress, March 2003 Burned Gas SL u’ L SL Unburned Gas SL Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... 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. The CBR Engine SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.10 The Tested Engine is equipped with: • a phased intake & Exhaust VVT Engine (CBR 1400 16v) CBR 1400 16v Inverse Miller Cycle Sketch of the Port-Deactivation System employed to promote the burning speed at high EGR rate

11. Experimental Analyses SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.11

12. Experimental Analyses SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.12

13. 1D Simulation SAE’03 World Congress, March 2003 Dp Exhaust mass flow rate Slider Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.13 CBR 1400 16v • Only Input Data: • Throttle Opening • Rotational Speed • Air/Fuel Ratio • Spark Advance • VVT Position • Ambient Conditions 1D Geometrical representation:

14. Validation at WOT SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.14

15. Validation at Part-Load SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.15

16. Validation at Part-Load SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.16

17. Validation at Part-Load SAE’03 World Congress, March 2003  = 50 deg Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.17 Phased intake & Exhaust VVT Engine (CBR 1400 16v)  = 0 deg  = 28 deg

18. Results Discussion SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.18 • The employed 1D engine models is well suited to the present application. A limited number of experimental data is required for model tuning and validation • Although not expressly required, an extended simulation analysis is also carried out. Theoretically derived engine operating maps can be employed in a number of control applications (static look-up tables) • The objective is to show the potential existing for a significant reduction of the experimental efforts required for the EMS

19. Extended Simulation Analyses SAE’03 World Congress, March 2003 EXP CBR 1400 16v NUM  = 0 deg Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.19

20. Extended Simulation Analyses SAE’03 World Congress, March 2003 EXP CBR 1400 16v NUM  = 50 deg Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.20

21. Results Discussion SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.21 • 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 • A great potential there exist for a significant reduction of the experimental efforts required for the EMS • The methodology is applicable to various VVA concepts and can certainly help a more rapid development of the EMS

22. The A/F Ratio Control SAE’03 World Congress, March 2003 EXP NUM Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.22 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

23. Vol. Eff. Correlation SAE’03 World Congress, March 2003 Vol.Eff0 from Correlation Vol.Eff0 from 1D Model Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.23 • 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

24. Vol. Eff. Correlation SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.24 • 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

25. Vol. Eff. Correlation SAE’03 World Congress, March 2003 Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.25 • The comparison on TRUE experimental data at various phase positions furnished good results: Vol.Eff from corrected correlation Experimental Vol.Eff.

26. Conclusion SAE’03 World Congress, March 2003 Black-Box White-Box Grey-Box F&E Models 1D Models Exp. Data Bozza, and Torella, 2003-01-0027, The Employment of a 1D Simulation Model ... Pag.26 • The results presented have shown the great potential offered by the 1D models in different control applications • The A/F Ratio Correlation……. • 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…