A SKELETAL KINETIC MECHANISM FOR PRF COMBUSTION IN HCCI ENGINES

Abstract

A single zone thermodynamic model, coupled to a kinetic mechanism, is developed and is capable of predicting the ignition timing of Primary Reference Fuels (PRFs) in a Homogeneous Charge Compression Ignition (HCCI) engine. A new combination of kinetic mechanisms is used, which includes 120 reactions and 58 species for both ignition and high temperature reactions. The model is validated using a step by step methodology. The validation compares ignition delays predicted by the model with published measurements from a rapid compression machine, shock tube as well as the cylinder pressure histories taken from two different experimental HCCI engines for various operating conditions. The model is able to qualitatively predict the effect of different parameters such as gas temperature, gas pressure, equivalence ratio and octane number on the HCCI ignition delay.

Keywords:

• HCCI
• Ignition
• Internal combustion engines
• Kinetic modeling
• Primary reference fuel

Financial support received from the Natural Sciences and Engineering Research Council of Canada (NSERC) research grant number 249553-02 and Canadian Federal Networks of Centers of Excellence (NCE) program under AUTO21 research grant D01–DAF/DO5 is acknowledged. The authors would also like to acknowledge the Westgrid High Performance Computing Network, which was used to obtain many of the results presented in this paper.

Notes

^a Third body efficiencies: H₂O, 0; H₂, 0; N₂, 0.

^b Third body efficiences: H₂O, 0; H₂, 0.

^c Third body efficiences: H₂O, 6.3.

^d Third body efficiences: H₂, 2; O₂, 6; H₂O, 6; CO, 1.5; CO₂, 3.5.

IVC: Intake Valve Closing, EVO: Exhaust Valve Opening, aBDC: after Bottom Dead Center.

^a Two experimental set-ups are used for the Ricardo engine. These two set-ups only differ in valve timings. Both intake and exhaust valves in the second configuration open and close 5 degrees before the values given in Table 3 (the first configuration).

All points at N = 700 rpm, Indicated Mean Effective Pressure ≈ 5 bar. T _in : intake temperature, p _ivc : cylinder pressure at IVC.

CAD aTDC: Crank Angle Degrees after Top Dead Center.