G. Adomeit

Bio: G. Adomeit is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Combustion & Ignition system. The author has an hindex of 8, co-authored 16 publications receiving 1250 citations.

Shock-tube investigations on the self-ignition of hydrocarbon-air mixtures at high pressures

Abstract: The self-ignition behaviour of various fuel-air mixtures has been investigated without inert gas dilutionusing a high-pressure shock tube. In order to obtain data directly applicable to the modeling of engine combustion, the shock-tube facility was designed to handle fuel-air mixtures up to initial pressures of more than 40 bar and to achieve measuring times up to 10 ms. As typical representatives of engine fuel components, n-heptane, benzene, iso-octane, methanol, and methyl-tert-butylether (MTBE) were investigated. Two pressure levels for the investigation, 13 bar and nearly 40 bar, have been chosen. The ignition of n-heptane begins with a rapid pressure increase, especially at higher temperatures. Benzene, iso-octane, methanol, and MTBE show a slow initiation of the ignition without distinct pressure peak (mild ignition) at low temperatures, which at higher temperatures changes to a rapid pressure increase after a variable time lag (strong ignition). The strong ignition limit depending on temperature, pressure, and fuel was determined. An investigation was made of the dependence of the ignition delay times of iso-octane and benzene on equivalence ratio and temperature at nearly 40 bar. A comparison of the ignition delay times of all the fuels investigated is presented for stoichiometric mixtures and at two pressure levels.

Kinetic modeling of gasoline surrogate components and mixtures under engine conditions

Abstract: Real fuels are complex mixtures of thousands of hydrocarbon compounds including linear and branched paraffins, naphthenes, olefins and aromatics. It is generally agreed that their behavior can be effectively reproduced by simpler fuel surrogates containing a limited number of components. In this work, an improved version of the kinetic model by the authors is used to analyze the combustion behavior of several components relevant to gasoline surrogate formulation. Particular attention is devoted to linear and branched saturated hydrocarbons (PRF mixtures), olefins (1-hexene) and aromatics (toluene). Model predictions for pure components, binary mixtures and multi-component gasoline surrogates are compared with recent experimental information collected in rapid compression machine, shock tube and jet stirred reactors covering a wide range of conditions pertinent to internal combustion engines (3–50 atm, 650–1200 K, stoichiometric fuel/air mixtures). Simulation results are discussed focusing attention on the mixing effects of the fuel components.

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.