Modeling n-dodecane Spray Combustion with a Representative Interactive Linear Eddy Model

Abstract

Many new combustion concepts are currently being investigated to further improve engines in terms of both efficiency and emissions. Examples include homogeneous charge compression ignition (HCCI), lean stratified premixed combustion, stratified charge compression ignition (SCCI), and high levels of exhaust gas recirculation (EGR) in diesel engines, known as low temperature combustion (LTC). All of these combustion concepts have in common that the temperatures are lower than in traditional spark ignition or diesel engines. To further improve and develop combustion concepts for clean and highly efficient engines, it is necessary to develop new computational tools that can be used to describe and optimize processes in nonstandard conditions, such as low temperature combustion. Thus, in the presented study a recently developed model (RILEM: Representative Interactive Linear Eddy Model [1]) for regime-independent modeling of turbulent non-premixed combustion is used to simulate the so called Spray B' of the Engine Combustion Network (ECN), which is a heavy-duty optical engine experiment. RILEM directly resolves the interaction of turbulent mixing with the chemistry along a one-dimensional representative line of sight through the combustion chamber via stochastic sequences of statistically independent eddy events. RILEM in its present form consists of a single (one-dimensional) linear eddy model (LEM) instantiation that is coupled to an unsteady Reynolds-averaged Navier-Stokes solver within the OpenFOAM framework. The coupling is similar to unsteady flamelet concepts but features distinct and important differences, e.g. an intrinsic representation of the scalar dissipation rate distribution and its fluctuations. Cylinder pressure, heat release rates and ignition delay time from the computation are compared to experiments under parametric variation of temperature.