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Combustion pp 137-152 | Cite as

Ignition Processes

  • Jürgen Warnatz
  • Ulrich Maas
  • Robert W. Dibble

Abstract

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,
$$ \rho {c_{p}}\frac{{\partial T}}{{\partial t}} = \frac{{\partial p}}{{\partial t}} + \frac{\partial }{{\partial z}}(\lambda \frac{{\partial T}}{{\partial z}}) - (\rho \upsilon {c_{p}} + \sum\limits_{j} {{j_{i}}} {c_{p}},j)\frac{{\partial T}}{{\partial z}} - \sum\limits_{j} {{h_{j}}} {r_{j}}. $$
(101)
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).

Keywords

Heat Production Flame Propagation Thermal Explosion Premix Flame Ignition Process 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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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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