International Journal of Automotive Technology

The Korean Society of Automotive Engineers (한국자동차공학회)
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EFFECT OF VALVE TIMING AND LIFT ON FLOW AND MIXING CHARACTERISTICS OF A CAI ENGINE

  • Kim, J.N. (Department of Mechanical Engineering, Korea University) ;
  • Kim, H.Y. (Department of Mechanical Engineering, Korea University) ;
  • Yoon, S.S. (Department of Mechanical Engineering, Korea University) ;
  • Sa, S.D. (Department of Mechanical Engineering, Korea University) ;
  • Kim, W.T. (Hyundai Motor Company)
  • Published : 2007.12.01
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Abstract

To increase the reliability of auto-ignition in CAI engines, the thermodynamic properties of intake flow is often controlled using recycled exhaust gases, called internal EGR. Because of the internal EGR influence on the overall thermodynamic properties and mixing quality of the gases that affect the subsequent combustion behavior, optimizing the intake and exhaust valve timing for the EGR is important to achieve the reliable auto-ignition and high thermal efficiency. In the present study, fully 3D numerical simulations were carried out to predict the mixing characteristics and flow field inside the cylinder as a function of valve timing. The 3D unsteady Eulerian-Lagrangian two-phase model was used to account for the interaction between the intake air and remaining internal EGR during the under-lap operation while varying three major parameters: the intake valve(IV) and exhaust valve(EV) timings and intake valve lift(IVL). Computational results showed that the largest EVC retardation, as in A6, yielded the optimal mixing of both EGR and fuel. The IV timing had little effect on the mixing quality. However, the IV timing variation caused backflow from the cylinder to the intake port. With respect to reduction of heat loss due to backflow, the case in B6 was considered to present the optimal operating condition. With the variation of the intake valve lift, the A1 case yielded the minimum amount of backflow. The best mixing was delivered when the lift height was at a minimum of 2 mm.

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References

  1. Asproulis, P. N. (1994). High Resolution Numerical Predictions of Hypersonic Flows on Unstructured Meshes. Ph. D. Dissertation. Imperial College. England
  2. Aoyama, T., Hattori, Y. and Mizuta, J. (1996). An experimental study on premixed-charged compression ignition gasoline engine. SAE Paper No. 960081
  3. Christensen, M., Hohansson, B. and Einewall, P. (1997). Homogeneous charge compression ignition (HCCI) using isooctane, ethanol and natural gas-A comparison with spark ignition operation. SAE Paper No. 972874
  4. Christensen, M. and Hohansson, B. (1998). Influence of mixture quality on homogeneous charge compression ignition. SAE Paper No. 982454
  5. Christensen, M., Hultqvist, A. and Hohansson, B. (1999). Demonstrating the multi fuel capability of a homogeneous charge compression ignition engine with variable compression ratio. SAE Paper No. 1999-01-3679
  6. Issa, R. I. (1986). Solution of the implicitly discretised fluid flow equations by operator-splitting. J. Comp. Phys., 62, 40−65
  7. Lavy, W., Dabadie, J., Willand, J., Juretzka, A., Ma, T., Lendresse, Y., Schulz, C., Kramer, H., Zhao, H. and Damiano, L. (2000). Innovative ultra-low NOx controlled auto-ignition combustion process for gasoline engines: The 4-SPACE project. SAE Paper No. 2000-01-1873
  8. Li, J., Zhao, H. and Ladommatos, N. (2001). Research and development of controlled auto-ignition (CAI) combustion in a 4-stroke multi-cylinder gasoline engine. SAE Paper No. 2001-01-3608
  9. Li, Y., Zhao, H., Brouzos, N. and Ma, T. (2006). Effect of injection timing on mixture and CAI combustion in a GDI engine with an air-assisted injector. SAE Paper No. 2006-01-0206
  10. Nicholls, J. A. (1972). Stream and Droplet Breakup by Shock Waves. NASA SP-194 (Eds. D.T. Harrje and F.H. Reardon). 126−128
  11. Ranz, W. E. and Marshall, W. R. (1952). Evaporation from drops-Part I and II, Chem. Eng. Prog. 48, 3, 141
  12. Reitz, R. D. and Diwakar, R. (1986). Effect of drop breakup on fuel sprays. SAE Paper No. 860469
  13. Sato, S., Kweon, S. P., Yamashita, D. and Iida, N. (2006). Influence of the mixing ration of double componential fuel on HCCI combustion. Int. J. Automotive Technology 7, 3, 251−259
  14. Weltens, H. (1993) Optimization of catalytic gas flow distribution by CFD prediction. SAE Paper No. 930784
  15. Yuen, M. C. and Chen, L. W. (1976). On drag of evaporating liquid droplets. Combust. Sci. and Tech. 14, 147−154