A technique for the Monte Carlo simulation of the radiation in the carbon dioxide and nitrogen dissociation products in a shock wave is described: the rates of chemical reactions, as well as the excitation of electronic, vibration, and rotation levels of atoms and molecules of CO, CN, O2, and C2. A comparison of the results of numerical simulation and the experimental data obtained on shock tubes of the Institute of Mechanics of Moscow State University is presented.

An analytical model for calculating the radiation intensity in shock-heated air is constructed, taking into account the absorption of radiation as it passes across the shock wave along the observation beam of the measuring systems of experimental installations. Using the model, an assessment is made of the effect of absorption on the broadening of spectral lines, as well as on the radiation intensity of high-temperature air in the vacuum-ultraviolet and visible spectral regions.

A series of experiments are conducted with the use of a shock tube at the Institute of Mechanics, Moscow State University to determine radiation absorption spectra in shock-heated oxygen in the wavelength range of 213–260 nm at a gas pressure of 1 Torr and shock wave velocities ranging from 3.4 to 4.5 km/s. Based on a comparison of the experimental data with the results of calculations using a spectral-kinetic model, the effect of bound–bound and bound–unbound transitions in the Schumann–Runge system on the absorption properties of oxygen is analyzed.

The self-ignition of a propylene–oxygen–argon stoichiometric mixture with a volumetric argon content of 95 C_2^ (λ = 553 nm) are analyzed. The ignition delay times τign are measured in the temperature range T = 1200–2460 K and pressures p = 4.5–25 atm. The data obtained are compared with the results of other authors.

Results of spectroscopic measurements of the equilibrium electron concentration behind a strong shock wave in argon at a shock-wave velocity of 4.2 km/s and a pressure ahead of the wave front of 5 Torr and in O2, N2, and air in the velocity range from 8.3 to 11.3 km/s at an initial pressure of 0.25 Torr are presented. The measurement method was based on an analysis of broadening of the hydrogen-atom Hβ line of the Balmer series in the spectrum of the integral radiation density of the studied gas to which a small amount of H2 was added ( 1

Предложена модель для численного исследования излучения за фронтом сильной ударной волны в газовой смеси CO 2 –N 2 . Модель основана на методе прямого статистического моделирования Монте-Карло и учитывает физико-химические свойства атомов и молекул, поступательно-вращательный и поступательно-колебательный обмен энергией, кинетику химических реакций, возбуждение электронных уровней атомов и молекул, а также процессы переноса радиационной энергии. Проведена серия расчетов спектральных характеристик ударно нагретой смеси. Полученные результаты сравниваются с имеющимися экспериментальными данными.

The radiation characteristics of shock-heated argon are measured in the shock-wave velocity range of 4.5 to 7.8 km/s at gas pressures ahead of the shock wave front of 0.25, 1.0, and 5.0 Torr. Time-integrated sweeps of radiation and the time dependences of the radiation intensity of shock-heated argon at the wavelength of 420 nm are obtained in absolute units. The results of direct statistical simulation by the Monte Carlo method of radiation-chemical processes in the argon behind the front of a strong shock wave are presented. The model takes into account the processes of excitation and ionization of an atom by electron impact, emission and absorption for a discrete spectrum, bremsstrahlung, photoionization, and photorecombination, as well as the broadening of atomic lines. The experimental and calculated data are compared.

The results of measuring the integral and temporal spectral characteristics of shock-heated air are presented. The experiments are carried out on a modified two-sections SST-M shock tube of the Institute of Mechanics, Moscow State University in shock wave velocities ranging from 7.8 to 10.7 km/s and initial pressures in the low-pressure chamber of 0.125 and 0.25 Torr. The radiation wavelength range 115–195 nm, corresponding to the vacuum ultraviolet (VUV) spectral region, in which the main contribution to the radiation is made by the atomic lines of nitrogen and oxygen, is studied. The obtained radiation spectrograms are analyzed. The measurement data are compared with the available experimental data of other authors.

С помощью двухдиафрагменной ударной трубы DDST-M Института механики МГУ проведена серия зондовых измерений параметров низкотемпературной плазмы перед фронтом падающей ударной волны. В качестве рабочих газов использовали азот, кислород, воздух и аргон. Полученные результаты позволяют описать процессы фотоэффекта и фотоионизации частиц исследуемого газа за счет жесткого излучения от ударно-нагретой среды и оценить влияние этих процессов на изменение потенциала зонда. Зондовые измерения синхронизированы с регистрацией светового потока, которая осуществлялась с использованием лавинного фотодиода и 9-кадровой видеокамеры К011, расположенных в торце ударной трубы. Данные с камеры и пьезоэлектрические датчики регистрируют динамику открытия диафрагмы, а также процесс формирования ударной волны в исследуемом газе.

The results of the radiation characteristics of shock-heated air measurements in the vacuum-ultraviolet region are presented. The experiments are carried out in the STS shock tube of the Institute of Mechanics, Moscow State University at shock-wave velocities of 7.3 to 10.7 km/s and initial pressures in the low-pressure chamber of 0.125, 0.2, and 0.25 Torr. An analytical model of the radiation process is constructed, which takes into account the absorption of radiation during its passage through the air . Processing the experimental dependences of the radiation intensity on time for the main radiation lines using this model made it possible to propose a radiation method for determining the electron temperature of a shock-heated gas. The presented data are compared with the experimental data of other authors.

Представлены результаты измерения радиационных характеристик атомных компонент ударно-нагретого воздуха в вакуумно-ультрафиолетовой области. Эксперименты проведены в ударной трубе STS Института механики МГУ при скоростях ударной волны 7.3–10.7 км/с и начальных давлениях в камере низкого давления 0.125, 0.2 и 0.25 Торр. Построена аналитическая модель радиационного процесса, учитывающая поглощение излучения при его прохождении поперек ударной волны вдоль луча наблюдения. Обработка с помощью этой модели экспериментальных зависимостей интенсивности излучения от времени для основных полос излучения позволила предложить радиационный метод определения электронной температуры ударно-нагретого газа. Представленные данные сравниваются с экспериментальными результатами, полученными другими методами.

The integral and temporal spectral characteristics of shock-heated air are measured in the shock wave velocity range from 7.35 to 10.4 km/s at the pressure ahead of the shock front p 0 = 0.25 Torr. The experiments are carried out on the DDST-M shock-wave setup of the Institute of Mechanics of Moscow State University. The radiation wave range λ = 600–1100 nm is studied; it corresponds to the visible and near infrared spectral ranges, where the main contribution to the radiation is made by the atomic lines of nitrogen and oxygen. The integral-in-time radiation spectrograms obtained in the experiments are analyzed. The distinctive features of the time oscillograms are defined for the most typical atomic lines of the spectrum. The measurement data are compared with the experimental data of other authors.

Измерены радиационные характеристики ударно-нагретого аргона в диапазоне скоростей ударной волны 4.5–7.8 км/с при давлении газа перед ее фронтом 0.25, 1.0 и 5.0 Торр. Получены интегральные по времени развертки излучения, а также временны́е зависимости интенсивности излучения ударно-нагретого аргона на длине волны 420 нм в абсолютных единицах. Представлены результаты прямого статистического моделирования методом Монте-Карло радиационно-химических процессов в аргоне за фронтом сильной ударной волны. В модели учитываются процессы возбуждения и ионизации атома электронным ударом, излучения и поглощения для дискретного спектра, тормозное излучение, процессы фотоионизации и фоторекомбинации, а также уширение атомарных линий. Проведено сравнение экспериментальных и расчетных данных.

This paper is the continuation of [ https://chemphys.edu.ru/issues/2017-18-1/articles/686/ ]. It presents the analysis of the experimental data [ https://chemphys.edu.ru/issues/2017-18-1/articles/686/ ] on the emission of pure argon behind the front of a strong shock wave in a range of velocities of 4.5–7.8 km/s and a range of pressures ahead of the wave front of 1 Torr. The estimates of the concentration of electrons, at which an avalanche-like increase in the emission intensity starts, are given based on the simplified model of an argon atom. The estimates of the population temperature of the electronic states are made using the data on the change in the concentration of the excited states on an assumption of their Boltzmann distribution. The presented estimates show that the population temperature substantially differs from the temperature of the gas behind the front of a shock wave. The discussion of the initial portion of emission is presented.

The paper presents the results of studies with the use of shock tubes at the Institute of Mechanics of the M. V. Lomonosov Moscow State University, in which measurements were made of the radiation of shock-heated gases simulating the conditions of the entry of spacecraft into the atmosphere of the Earth and other planets of the Solar system with orbital and superorbital velocities. A description of the measuring equipment is given, as well as techniques of diagnostics and processing of the obtained spectroscopic information. Numerous experimental data on the radiation of shock-heated gases in a wide range of the radiation spectrum from vacuum ultraviolet to infrared have been analyzed, which serve as the basis for the development of various gas-dynamical models.

Представлены результаты измерения интегральных и временны́х спектральных характеристик ударно-нагретого воздуха. Эксперименты проведены на модифицированной двухсекционной ударной трубе STS-M Института механики МГУ в интервале скоростей ударной волны от 7.8 до 10.7 км/с при начальных давлениях в камере низкого давления 0.125 и 0.25 Торр. Исследован диапазон волн излучения 115–195 нм, соответствующий вакуумно-ультрафиолетовой области спектра, в которой основной вклад в излучение дают атомарные линии азота и кислорода. Проведен анализ полученных спектрограмм излучения. Данные измерений сравниваются с имеющимися экспериментальными данными других авторов.

The study of radiation shock-heated gases provides information on the radiation heat fluxes, which are of great interest for problems in hypersonic aerodynamics. The results of the experimental study of the initial stage of nonequilibrium emission of pure argon obtained at the experimental "Shock tube" complex of the Research Institute of Mechanics, Moscow State University are presented. A simplified model is proposed for the calculation of the radiation intensity of atomic lines behind the shock wave front. The effect of electrons on the features of argon radiation at the initial stage after the passage of the shock wave behind the gas-dynamic front before the beginning of the avalanche ionization is discussed.