—Extensive experimental results were obtained on the oxidation of many aliphatic hydrocarbons in a high temperature, turbulent flow reactor developed for kinetic studies. These results indicated the viability of presenting this complex kinetic situation in the format of a simplified, overall kinetic scheme which could accurately predict the major species formed and the temperature-time history (rate of heat release) of the system. The proposed overall mechanism follows the general form:

A Multiple-step Overall Kinetic Mechanism for the Oxidation of Hydrocarbons

Ignition time measurements of propane, n-butane, n-heptane, and n-decane have been studied behind reflected shock waves over the temperature range of 1300-1700 K and pressure range of 1-6 atm. The test mixture compositionvaried from approximately 2-20% O 2 , and the equivalence ratio ranged from 0.5 to 2.0. To determine more precisely the fuel mole fraction of the test mixture, a new technique has been employed in which a 3.39-μm HeNe laser and multiple-pass setup is utilized to measure the fuel in situ by absorption. Ignition delay times were measured at the shock tube endwall by a CH emission diagnostic (431 nm) that viewed the shock-heated mixture through a window in the endwall. This enabled the ignition time at the unperturbed endwall conditions to be determined accurately, thereby avoiding problems inherent in measuring ignition times from the shock tube sidewall. A parametric study of the experimental data reveals marked similarity of the ignition delay time characteristics among these four n-alkanes, and a unique correlation is presented in which the stoichiometric ignition time data for all four n-alkanes has been correlated into a single expression with an R 2 value of 0.992: Τ=9.4×10 - 1 2 P - 0 . 5 5 X O 2 - 0 . 6 3 C - 0 . 5 0 exp(46,550/RT) where the ignition time is in seconds, pressure in atmospheres, the activation energy in calories per mole, X O 2 is the mole fraction of oxygen in the test mixture, and C is the number of carbons atoms in the n-alkane. Comparisons to past ignition time studies and detailed kinetic mechanisms further validate the correlations presented here.

Study of the High-Temperature Autoignition of n-Alkane/O/Ar Mixtures

Abstract—A detailed chemical kinetic reaction mechanism is developed to describe the oxidation and pyrolysis of propane and propene. The mechanism consists of 163 elementary reactions among 4l chemical species. New rate expressions are developed for a number of reactions of propane, propene, and intermediate hydrocarbon species with radicals including H, 0, and OH. The mechanism is tested by comparisons between computed and experimental results in shock tubes and the turbulent flow reactor. The resulting comprehensive mechanism accurately reproduces experimental data for pressures from 1 to 15 atmospheres, temperatures from 1000 to 1700 K, and fuel-oxidizer equivalence ratios from 0.066 to pyrolysis conditions. The mechanism also predicts correctly laminar flame properties for propane and propene, and detonation properties for propane.

A Comprehensive Chemical Kinetic Reaction Mechanism for Oxidation and Pyrolysis of Propane and Propene

An analytical study of the ignition of mixtures of methane and ethane has been carried out, using a numerical model consisting of 25 chemical species and 75 elementary chemical reactions. Computed ignition delay times and effective activation energies are compared with published experimental shock tube results. Initial conditions studied include temperatures from 1300-1900 K. and mixtures ranging from pure methane to pure ethane, with stoichiometric amounts of oxygen, diluted in argon. The analytical model reproduces experimental results for the effective activation energy and ignition delay time for both pure methane and pure ethane. Ignition delay times computed for mixtures of methane and ethane are found to lie between the pure methane and the pure ethane results. Addition of relatively small quantities of ethane to methane rapidly reduces the ignition delay time of the methane-ethane mixtures to values close to those of pure ethane. The chemical kinetic factors involved in the ignition of fu...

K. Sheller

Papers

Shock tube investigation of ignition in propane--oxygen--argon mixtures. [At temperatures of 1250 to 1600/sup 0/K and pressures from 2 to 10 atm]