Том 52, № 4 (2016)

The influence of C₃–C₅ alkanes on the ignition of their binary mixtures with methane in air at a temperature of 523–1000 K and a pressure of 1 atm is studied. It is shown that the presence of only 1% C₃–C₅ alkanes considerably reduces the ignition delay of methane. At a concentration of 10–20%, the ignition delay practically corresponds to the autoignition delay of the added alkane. The effect of additives of heavy alkanes becomes less noticeable with increasing initial temperature. These results can be used to estimate the permissible content of C₅₊ heavy species in gas turbine engine fuel at which their influence on the fuel knock resistance is sufficiently low. It is only 0.5%.

The mechanism of formation of nanosized aerosol particles during mechanical grinding of coal from Kuzbass mines is studied. The concentration and size spectrum of aerosol particles in a mine tunnel during cutter operation were measured using an aerosol spectrometer. It is found that 90% of the particles are less than 200 nm in size. In the nanometer range, there are two peaks corresponding to average diameters of 20 and 150 nm, the first of which is due to single particles, and the second to aggregates consisting of single particles. The formation of aerosol during mechanical coal grinding in a continuous flow mill was studied. The spectrum and morphology of the particles produced in the laboratory mill are in qualitative agreement with those for the nanoaerosol formed in the mine. The influence of the coal aerosol on the combustion of gas mixtures was studied. Laboratory experiments showed that the presence of the nanoaerosol in a lean methane–air mixture significantly increased its explosibility. This was manifested in an increase in the maximum pressure and a significant increase in the pressure rise rate during explosion. The study leads to the conclusion that the nanoaerosol is formed from the organic coal components released into the gas phase during local heating of coal on the cutter teeth.

Experimental data demonstrating the correlation of parameters in the power-law dependence of the burning rate of composite solid propellants on pressure are reported. The reasons for changes in the burning rate due to changes in propellant mixing conditions are discussed. The deviation of the pressure in the combustor of a solid-propellant rocket motor is analyzed with due allowance for the correlation of parameters in the burning rate law. It is shown that the relative deviation of the burning rate depends on pressure at which propellant combustion occurs. Moreover, for each propellant, there exists a pressure level at which the burning rate deviation is theoretically equal to zero, regardless of the differences in propellant compositions and properties.

Regimes of continuous spin detonation in a plane–radial combustor with an external diameter of 80 mm with peripheral injection of a hydrogen–oxygen mixture in the range of specific flow rates of the mixture 3.6–37.9 kg/(s ·m²) are obtained for the first time. Depending on the diameter of the exit orifice in the combustor (40, 30, or 20 mm), specific flow rate of the mixture, its composition, and counterpressure, one to seven transverse detonation waves with a frequency from 6 to 60 kHz are observed. It is found that the number of detonation waves increases, while their intensity decreases owing to reduction of the exit orifice diameter or to an increase in the counterpressure. The flow structure in the region of detonation waves is analyzed. The domain of detonation regimes in the coordinates of the fuel-to-air equivalence ratio and specific flow rate of the mixture is constructed. A physicomathematical model of continuous spin detonation in a plane–radial combustor is formulated. For parameters of hydrogen and oxygen injection into the combustor identical to experimental conditions, the present simulations predict similar parameters of detonation waves, in particular, the number of waves over the combustor circumference and the wave velocity.

Based on a previously proposed modified van der Waals model for a mixture, a widerange semi-empirical equation of state for silicon dioxide with due allowance for evaporation, dissociation, and ionization is constructed. In the low-density limit, it transforms to Saha’s equation of state for a mixture of ideal gases consisting of ions and electrons. The model and simplifying assumptions used in constructing the equation of state are described. The values of constitutive parameters are given. Results of model calculations are compared with data obtained in experiments on shock compression of solid and porous quartz samples, isentropic unloading, etc.

This paper presents the results of experimental studies of the cavitation breakdown of liquids in a wide range of shock-wave loading. The free surface velocity of liquids and the velocity spectrum of the cloud of particles and jets were measured using a laser heterodyne interferometer (photon Doppler velocimetry), and their size was determined. The spall strength of distilled water was determined.

The dynamic compression and localized adiabatic shear in samples of an HMX based explosive was studied using the split Hopkinson bar technique. Dynamic compression tests were performed at strain rates of (0.3–2.0) · 10³ s⁻¹. Fracture of the explosive samples was found to occur at stresses of 60–80 MPa. The behavior of HMX based samples was also studied in localized shear tests at different strain rates (200–2500 s⁻¹). The initiation of explosive transformations under the dynamic loads is discussed.