Himičeskaâ fizika

The analysis of the main methods for recording the radiation characteristics of high-temperature gases behind the front of a strong shock wave, including the 3D-spectroscopy method and the time-integrated spectroscopy method, is carried out. A more realistic approach to processing experimental data is proposed, which presents the obtained information in the form of spectrograms of the thermal flux power of shock-heated gas. Spectrograms of the thermal flux power of shock-heated air measured by the time-integrated spectroscopy method in the shock wave velocity range from 8 to 11 km/s at an initial pressure of 0.25 Torr are analyzed. Their comparison with the corresponding spectrograms obtained by the 3D-spectroscopy method showed that both methods give approximately the same results.

Using a quasi-one-dimensional model of steady detonation with a divergent flow in the reaction zone, an analysis of an array of experimental data on the detonation rate of finely dispersed ammonium perchlorate was carried out, which was obtained at one time by Donna Price with her colleagues from the NOL Laboratory of the USA. In these experiments, the diameter and initial charge density varied over a wide range. As a result of the analysis, the values of two coefficients included in the equation of the rate of exothermic conversion of AP (the pressure exponent n and the rate constant G) were determined, at which the calculations are consistent with the experiment on the dependence of the detonation velocity on the charge diameter for five different values of initial density. In all calculations, the exponent of n turned out to be 1.0, and the constant G decreased by more than 4 times, as the initial density increased from 1.0 to 1.45 g/cm³. The flow characteristics in the detonation wave reaction zone were calculated. The detonation wave front has a shape close to spherically symmetrical, only on and near the charge axis. The radius of curvature of the front, which is close in magnitude to the diameter of the charge on the charge axis, decreases 4–5 times as it approaches the side interface of the charge. Along with the radius of curvature near the side interface, the pressure at the wave front decreases significantly. The width of the reaction zone, from the wave front to the Chapman-Jouget point, is about 3 mm and increases with increasing density. An analysis of the calculated characteristics of the reaction zone for near-critical conditions close to detonation failure showed that a significant decrease in the particle velocity gradient at the wave front due to energy losses in the lateral rarefaction wave is observed at the side interface of the charge and is absent on the charge axis. Thus, it is the side interface of the charge that should be considered as the place whereconditions for detonation failure are formed, as a result of a decrease in the rate of exothermic conversion and an increase in energy losses in the lateral rarefaction wave.

Atmospheric aerosol containing sulfates affects air quality on a regional scale and the climate on a global scale. For example, in the northern part of the North China Plain, an agglomeration with a population of about half a billion people is systematically exposed to catastrophically rapid pollution by dense haze. In this work, for the first time, evidence is interpreted in favor of the existence of critical atmospheric conditions that enable the extremely rapid formation of sulfates and nitrates in aerosol particles and, in combination with suitable meteorological conditions (temperature, relative humidity, atmospheric stagnation, etc.), lead to the occurrence of aerosol haze. It is shown that sustained and rapid sulfate accumulation in the degenerate-branched regime of a catalytic process involving transition metal ions is possible – at a given air humidity and in an atmosphere polluted with sulfur and nitrogen oxides – only if the ammonia concentration exceeds a certain threshold. At the same time, the rate of nitrate formation also increases, driven by the coupling of sulfate and nitrate formation processes. As a result, the absorption of moisture and ammonia from the air intensifies, ensuring a self-sustaining and rapid increase in the mass concentration of aerosol haze particles in the atmosphere.