Effects of fuel cetane number on the structure of diesel spray combustion: An accelerated Eulerian stochastic fields method

Abstract

An Eulerian stochastic fields (ESF) method accelerated with the chemistry coordinate mapping (CCM) approach for modelling spray combustion is formulated, and applied to model diesel combustion in a constant volume vessel. In ESF-CCM, the thermodynamic states of the discretised stochastic fields are mapped into a low-dimensional phase space. Integration of the chemical stiff ODEs is performed in the phase space and the results are mapped back to the physical domain. After validating the ESF-CCM, the method is used to investigate the effects of fuel cetane number on the structure of diesel spray combustion. It is shown that, depending of the fuel cetane number, liftoff length is varied, which can lead to a change in combustion mode from classical diesel spray combustion to fuel-lean premixed burned combustion. Spray combustion with a shorter liftoff length exhibits the characteristics of the classical conceptual diesel combustion model proposed by Dec in 1997 (http://dx.doi.org/10.4271/970873), whereas in a case with a lower cetane number the liftoff length is much larger and the spray combustion probably occurs in a fuel-lean-premixed mode of combustion. Nevertheless, the transport budget at the liftoff location shows that stabilisation at all cetane numbers is governed primarily by the auto-ignition process.

Keywords:

• transported PDF
• acceleration technique
• diesel spray flames

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was sponsored by the Swedish Research Council (VR) and the Competence Center for Combustion Processes (KC-FP) at Lund University as well as the Swedish Energy Agency and Scania through an FFI project. The computation was performed using the Lindgren cluster at the PDC Center for High Performance Computing and the Swedish National Infrastructures for Computing (SNIC).