Investigating renewable fuel combustion II: DNS of DME and n‐heptane ignition in a turbulent non‐homogeneous flow with high dissipation

Abstract

Direct Numerical Simulations (DNS) are conducted to gain insight into the early ignition process in a non‐homogeneous turbulent flow. This is the second part of a study to investigate the characteristics of renewable oxygenated fuel versus conventional diesel. In the first study, Unsteady Reynolds‐Averaged Navier‐Stokes (URANS) simulations of a research diesel engine were carried out. Attention was paid to the impact of the liquid phase properties on the in‐cylinder flow patterns. DNS is employed here to investigate local micro‐mixing effects on ignition. DiMethyl‐Ether (DME) is the model for oxygenated fuel while conventional hydrocarbon (HC) is represented by n‐heptane. Subtle effects of micro‐mixing can modify the combustion phasing in the compression‐ignition mode. For the same temperature and mixture fraction distributions, the location of the stoichiometry iso‐surface is different for the oxygenated and conventional fuels, and as a result ignition kernels develop at a higher temperatures for n‐heptane than for DME. This may change the conclusions with respect to the cetane number and homogeneous ignition investigations.

Keywords:

• Turbulence
• Ignition
• DNS
• Complex chemistry
• DME
• Diesel

Acknowledgement

This research has been made possible by the funding received from the Government of Canada Program for Energy Research and Development (PERD/AFTER) and from the National Research Council of Canada. The contribution from Dr W. Wallace to improve the shape of the communication is greatly appreciated.