Combustion modeling in RCCI engines with a hybrid characteristic time combustion and closed reactor model. (1st October 2018)

• Record Type: Journal Article
• Authors: Zhou, Dezhi; Yang, Wenming; Li, Jing; Tay, Kun Lin; Kraft, Markus
• Is Part Of: Applied energy. Volume 227(2018)
• Page Start: 665
• Page End: 671
• Publication Date: 2018-10-01
• Subjects: RCCI combustion modeling -- CTC model -- CHEMKIN -- Hybrid model; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2017.08.137
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: A hybrid model based on the classical CTC model and CHEMKIN model was proposed. The proposed hybrid model is able to model RCCI combustion with detailed chemistry. The hybrid model is robust and efficient for RCCI combustion simulations. Abstract: This study proposed a hybrid model consisting of a characteristic time combustion (CTC) model and a closed reactor model for the combustion modelling with detailed chemistry in RCCI engines. In the light of the basic idea of the CTC model of achieving chemical equilibrium in high temperature, this hybrid model uses the CTC model to solve the species conversion and heat release in the diffusion flame. Except for the diffusion flame, the auto-ignition in RCCI combustion is computed by a closed reactor model with the CHEMKIN library by assuming that the computational cells are closed reactors. The border of the transition between the CTC model and closed reactor model is determined by two criteria, a critical temperature and a critical Damköhler number. On the formulation of this hybrid model, emphasis is placed on coupling detailed chemistry into this hybrid model. A CEQ solver for species equilibrium calculations at certain temperature, pressure was embedded with CTC for detailed chemistry calculation. Then this combustion model was integrated with the CFD framework KIVA4 and the chemical library CHEMKIN-II and validated in a RCCI engine. The predicted in-cylinder pressure and heat release rate (HRR) show a good consistency with the data from the experiment and better accuracy than that computed from the sole closed reactor model. More importantly, it is observed that this model could save computational time compared with closed reactor model due to less stiff ordinary differential equations (ODEs) computation. A sensitivity analysis of the critical temperature and critical Damköhler number was conducted to demonstrate the effect of these two parameters in the current model.