Chemically Reacting Flows Division

Autoignition in Turbulent Flows

Turbulent Inhomogeneous Autoignition of Liquid Fuels

Autoignition is a multi-physics phenomenon that occurs in wide-ranging engineering applications, such as diesel engines, gas turbines and jet-engine afterburners. In these applications, autoignition occurs in the presence of flow inhomogeneities and turbulence. Liquid fuel autoignition presents a case of chemically reacting flow where processes such as jet break-up, atomisation, droplet evaporation (interfacial heat and mass transfer), turbulent mixing and chemical reaction occur simultaneously in the presence of flow, mixture and phase inhomogeneities. The multi-scale nature and direct coupling between these various contributing processes, present a challenging fundamental problem which cannot be understood by extrapolation from homogeneous, inhomogeneous (gaseous) and even single droplet combustion studies.Photo

The Chemically Reacting Flow Division of the Clean Energy Processes Laboratory at Imperial College London is equipped with a state-of-the-art experimental apparatus for a parametric study of the effect of flow inlet conditions on autoignition of polydispersed droplets of pure liquid fuels. A vertically mounted and optically accessible quartz reactor of circular cross-section receives upwards flowing air with temperatures up to 1150 K and velocities up to 40 m/s. Liquid fuel is injected continuously and axisymmetrically from a water-cooled circular nozzle (placed concentrically at the reactor inlet) into this confined turbulent coflow of high temperature air at atmospheric pressures. Dynamic measurements of temperature with fine thermocouples and; optical non-intrusive measurements (with high-speed cameras) are performed to obtain quantitative data on autoignition delay time, location, frequency; fuel jet break-up, drop formation and evaporation.




Research application/scope:

  • Improve design of combustors in engines and gas turbines for efficient fuelutilisation and reduction of harmful emissions by predicting and controlling autoignition
  • Measurements constitute a valuable data-set for validating and developing computational models of multiphase turbulent combustion and chemically reactingflows