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Acetylene is an effective additive to various rocket fuels. Acetam, an equilibrium highly concentrated solution of acetylene in liquid ammonia, is a promising fuel for use in liquid−propellant jet engines. To gain insights into the processes occurring in such systems and provide means for predicting their characteristics, the self-ignition of model acetylene−oxygen−argon mixtures is experimentally and theoretically studied. The experiments are performed behind reflected shock waves in a temperature range from 1100 to 1870 K at a total gas concentration of [M] ≈ 1.0 × 10−5 mol/cm3, with chemiluminescence signals from electronically excited C 2 * (λ ≅ 516 nm), CH* (429 nm), CO 2 *(363 nm), and OH* (308 nm) recorded. Numerical simulations within the framework of various detailed kinetic mechanisms closely reproduce the measured temperature dependences of the ignition delay time for the tested mixtures, but in some cases fail to satisfactorily describe the time profiles of the emission signals from C 2 *, CH*, CO 2 *, and OH*. The performed numerical simulations make it possible to explain the observed characteristic features of the emission profiles of electronically excited C 2 *, CH*, CO 2 *, and OH* during the self-ignition of C 2 H 2 –O 2 −Ar mixtures. Sensitivity analysis demonstrates that the existence and characteristics of the preignition stage in the CO 2 * and OH* emission signals are largely determined by the kinetic behavior of intermediate species, such as the ketene molecule and CH 2 radical. Based on the results obtained, a new detailed kinetic mechanism has been proposed for describing processes in the combustion products of acetylene-containing propellants, in particular chemiluminescent glow, which are of considerable interest for the development of new technologies for astronautics and aeronautics. • Results of shock-tube acetylene autoignition are presented. • A detailed kinetic mechanisms capable of describing acetylene ignition delay is developed. • The problems of simulation of chemiluminescence are discussed. • The importance of the kinetics of intermediate products are demonstrated. [ABSTRACT FROM AUTHOR]

The self-ignition of a stoichiometric acetone−oxygen mixture diluted with argon was studied both experimentally and numerically. The experiments were performed behind reflected shock waves over a temperature range from 1280 to 1810 K at a total gas concentration of [ M ] 50 ≈ 10−5 mol/cm3. The process was monitored by recording the signals of absorption by methyl radicals (λ = 216.5 nm) and emission from electronically excited OH* radicals (λ = 308 nm) and CO 2 * molecules (λ = 370 nm). Numerical simulations within the framework of various detailed kinetic mechanisms were performed to reproduce our own and published experimental data on the pyrolysis and self-ignition of acetone behind reflected shock waves, including the concentration profiles of acetone and CH 3 in the ground state and electronically excited OH* and CO 2 *, as well as the temperature dependence of the self-ignition delay time. It has been established that various detailed kinetic mechanisms describe the kinetic characteristics of the pyrolysis of acetone in shock waves with varying degrees of accuracy. At the same time, all of them predicted the measured ignition delays within a factor of two. A sensitivity analysis showed that the reactions determining the pyrolysis of acetone produce only a slight effect on the branched-chain ignition process, so that the relevant rate constants only slightly affect the ignition delay time. • Shock tube results of acetone autoignition are presented. • Detailed kinetic mechanisms are capable to describe acetone ignition delay. • The problems of simulation of acetone pyrolysis were revealed. • Kinetics of methyl radicals reactions should be refined. [ABSTRACT FROM AUTHOR]

The time evolution of the chemiluminescence emission signals of CH*, OH*, C 2 *, and CO 2 * during the self-ignition of a number of the simple hydrocarbons is studied. The experiments are performed behind reflected shock waves over a temperature range of 1100–1900 K at a pressure of ∼1 bar. The effects of fuel-to-oxidizer equivalence ratio and the structure of the hydrocarbon molecule on the time profiles of the signals for each of the emitters are examined. A detailed kinetic mechanism for describing the emission signals from CH*, OH*, C 2 *, and CO 2 * recorded during the self-ignition of hydrocarbons is developed. To make the simulations more rigorous and reliable, the NASA thermodynamic polynomials for C 2 *, and CO 2 * were calculated based on the respective rotational and vibrational parameters given in the literature. Numerical simulations satisfactorily reproduce the measured time profiles of the signals from the studied emitters. • Chemiluminescence emission of CH*, OH*, C2*, and CO2* is studied. • Detailed kinetic mechanism for describing the emission signals was developed. • Simulation results well reproduce the measured intensity of emission. • Full width at half maximum of the emission signals are presented. [ABSTRACT FROM AUTHOR]