Combustion pp 137-152 | Cite as

Ignition Processes

  • Jürgen Warnatz
  • Ulrich Maas
  • Robert W. Dibble


The discussion of premixed flames (Chapter 8) and nonpremixed flames (Chapter 9) assumed that the flames were at a steady state. The solutions are time-independent. The time-dependent process of starting with reactants and evolving in time towards a steadily burning flame is called ignition. Ignition processes are always time-dependent. Examples of ignition processes include induced ignition (such as occurs in gasoline engines induced by a spark), autoignition (such as occurs in Diesel engines), and photoignition caused by photolytic generation of radicals. In these cases, the ignition process is described quantitatively by addition to the time-dependent energy conservation equation (3.6) a term ∂p/∂t,
$$ \rho {c_{p}}\frac{{\partial T}}{{\partial t}} = \frac{{\partial p}}{{\partial t}} + \frac{\partial }{{\partial z}}(\lambda \frac{{\partial T}}{{\partial z}}) - (\rho \upsilon {c_{p}} + \sum\limits_{j} {{j_{i}}} {c_{p}},j)\frac{{\partial T}}{{\partial z}} - \sum\limits_{j} {{h_{j}}} {r_{j}}. $$
The additional term accounts for the temperature increase (or decrease) caused by compression (or expansion) of the mixture. Here it is assumed that, although the pressure p varies with time, the pressure is spatially uniform (Maas and Warnatz 1988).


Heat Production Flame Propagation Thermal Explosion Premix Flame Ignition Process 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Jürgen Warnatz
    • 1
  • Ulrich Maas
    • 2
  • Robert W. Dibble
    • 3
  1. 1.Universität Heidelberg Interdisziplinäres Zentrum für Wissenschaftliches RechnenHeidelbergGermany
  2. 2.Institut für Technische VerbrennungUniversität StuttgartStuttgartGermany
  3. 3.Department of Mechanical EngineeringUniversity of CaliforniaBerkeleyUSA

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