Minimum ignition energy

About: Minimum ignition energy is a research topic. Over the lifetime, 2275 publications have been published within this topic receiving 44606 citations.

Chemical kinetics of hydrocarbon ignition in practical combustion systems

Abstract: Chemical kinetic factors of hydrocarbon oxidation are examined in a variety of ignition problems. Ignition is related to the presence of a dominant chain-branching reaction mechanism that can drive a chemical system to completion in a very short period of time. Ignition in laboratory environments is studied for problems including shock tubes and rapid compression machines. Modeling of the laboratory systems is used to develop kinetic models that can be used to analyze ignition in practical systems. Two major chain-branching regimes are identified, one consisting of high temperature ignition with a chain branching reaction mechanism based on the reaction between atomic hydrogen with molecular oxygen, and the second based on an intermediate temperature thermal decomposition of hydrogen peroxide. Kinetic models are then used to describe ignition in practical combustion environments, including detonations and pulse combustors for high temperature ignition and engine knock and diesel ignition for intermediate temperature ignition. The final example of ignition in a practical environment is homogeneous charge, compression ignition (HCCI), which is shown to be a problem dominated by the kinetics of intermediate temperature hydrocarbon ignition. Model results show why high hydrocarbon and CO emissions are inevitable in HCCI combustion. The conclusion of this study is that the kinetics of hydrocarbon ignition are actually quite simple, since only one or two elementary reactions are dominant. However, many combustion factors can influence these two major reactions, and these are the features that vary from one practical system to another.

Numerical modeling of catalytic ignition

Abstract: Catalytic ignition of CH4, CO, and H2 oxidation on platinum and palladium at atmospheric pressure is studied numerically. Two simple configurations are simulated: the stagnation flow field over a catalytically active foil and a chemical reactor with a catalytically active wire inside. The simulation includes detailed reaction mechanisms for the gas phase and for the surface. The gas-phase transport and its coupling to the surface is described using a simplified multicomponent model. The catalyst is characterized by its temperature and its coverage by adsorbed species. The dependence of the ignition temperature on the fuel/oxygen ratio is calculated and compared with experimental results. The ignition temperature of CH4 oxidation decreases with increasing CH4/O2 ratio, whereas the ignition temperature for the oxidation of H2 and CO increases with increasing fuel/oxygen ratio. The kinetic data for adsorption and desorption are found to be critical for the ignition process. They determine the dependence of the ignition temperature on the fuel/oxygen ratio. A sensitivity analysis leads to the rate-determining steps of the surface reaction mechanism. The bistable ignition behavior observed experimentally for lean H2/O2 mixtures on palladium is reproduced numerically. The abrupt transition from a kinetically controlled system before ignition to one controlled by mass transport after ignition is described by the time-dependent codes applied.