Enthalpy (fuel mass fraction and/or temperature) fluctuations in the oncoming mixture are known to have important impacts on premixed combustion and in particular on combustion instability. Theoretical modeling has primarily been following an empirical approach. In Part I of the present study, an asymptotically reduced first-principle theory was derived from the reactive Navier-Stokes equations...

The spectral characteristics of combustion noise is dictated by the temporal correlation of the heat release rate fluctuation. This paper investigates the two-point space-time correlation of heat release rate fluctuations by analysing recent direct numerical simulation (DNS) data of turbulent premixed flames. The results show that this correlation decays rapidly in both space and time due to th...

Today, much of the current effort in combustion noise is the development of efficient numerical tools to calculate the noise radiated by flames. Although unsteady CFD methods such as LES or DNS can directly provide the acoustic field radiated by noise sources, this evaluation is limited to small domains due to high computational costs. Hybrid methods have been developed to overcome this limitat...

The Stochastic Fields approach is an effective way to implement transported Probability Density Function modelling into Large Eddy Simulation of turbulent combustion. In premixed turbulent combustion however, thin flame-like structures arise in the solution of the Stochastic Fields equations that require grid spacing much finer than the filter scale used for the Large Eddys Simulation. The conv...

This year’s cover illustration, reproduced here as figure 1, depicts an image formed by a short-time (1/1000 s) exposure of a non-premixed hydrocarbon flame. The flow is driven by the buoyancy forces generated by the density difference from the combustion heat release and resulting temperature rise. The Reynolds number for this buoyancy-induced, turbulent flow is relatively low, estimated at a ...

Temperature Response of an Acoustically Forced Turbulent Lean Premixed Flame: A Quantitative Experimental Determination Robin S. M. Chrystie a , Iain S. Burns b & Clemens F. Kaminski c a Clean Combustion Research Centre, King Abdullah University of Science and Technology, Jeddah, Saudi Arabia b Department of Chemical and Process Engineering, University of Strathclyde, Glasgow, UK c Department o...

TheG-function approach to premixed combustion problems is based on the flamelet concept. Thereby, the flame front is modeled as an embedded interface within the bulk. A level set function is used to describe the position of the flame front. To account for discontinuities in the velocity and the pressure fields across the interface, an eXtended Finite Element Method (XFEM) is applied. That is, t...

NOx emissions in n-heptane/air partially premixed flames (PPFs) in a counter-flow configuration have been investigated. The flame is computed using a detailed mechanism that combines the Held’s mechanism for n-heptane and the Li and Williams’ mechanism for NOx. The combined mechanism contains 54 species and 327 reactions. Based on a detailed analysis, dominant mechanisms responsible for NOx for...

We present simulations of a laboratory-scale low swirl burner fueled with hydrogen at atmospheric pressure. The study uses detailed chemistry and transport including a submechanism for computing nitrogen emissions. The simulation shows how the cellular burning structures characteristic of lean premixed hydrogen combustion lead to enhancements in the NOx emissions from these flames. Analysis of ...