Possible emergency situations typical for hotshot wind tunnels with electric arc or combined heating of the test gas with systems of stabilization and controlled diaphragm breakdown are considered in the case of malfunction when the arc discharge in the discharge chamber does not occur and the capacitor battery remains charged. To prevent emergency situations, the following changes (feedback elements) are made in the wind tunnel structure, which allow further operation of the wind tunnel systems only if there is an increase in pressure in the settling chamber due to heat supply: 1) the piston of the fast-response valve is hollow to increase the volume of the locking cavity to eliminate the necessity of decreasing the pressure in this cavity; 2) the high-pressure channel connecting the piston and its rod with the settling chamber volume is filled by a fluid and closed by the piston on the side of the settling chamber, 3) the device for forced breakdown of the diaphragm is equipped by an external electric circuit for diaphragm opening control.

The paper presents a set of tests with a setup using steam supply into ejector instead of compressed air. Experi-ments measured the gas analysis data — volumetric concentrations O 2 , CO, CO 2 , C n H m , NO x , H 2 at different propor-tions of air and steam. The data are compared with calculations for thermodynamic equilibrium compositions for the reacting mixture С+Н 2 О+air performed by “Terra” computer code including the case of air excess ( α ≤ 1). The cal-culations were also compared with available data on gasification output at a high content of ballasting gas. It was demonstrated that in these operation modes, the steam was an inert dilution agent, which did not exclude the outcome of coal gas production with high Н 2 /СО and СО/СО 2 ratios corresponding to different modes of gasification.

In the present paper, we analyze emergency situations typical of short-duration wind tunnels with electric-arc or combined test-gas heating in the presence of stabilization and diaphragm-rupturing systems, which occur in the case of no discharge initiation in the settling chamber, with the capacitor battery having remained charged during the start of wind-tunnel systems. For avoiding such emergency situations, some additional changes based on using feedback elements are introduced into the wind-tunnel design: the piston of the fast-response valve is made hollow for increasing the volume of the shutoff cavity and for making the release of pressure from this cavity unnecessary; the high-pressure channel, which connects the piston and the piston rod with the settling-chamber cavity, is filled with a liquid and is closed from the side of the settling chamber with a piston; the device for controlled diaphragm breakdown is provided with an external electric circuit intended to control the diaphragm-rupturing process. Those modifications allow subsequent functioning of the wind-tunnel systems only in the presence of heat-supply-induced pressure growth in the settling chamber of the wind tunnel.

This paper presents a review of studies of the photoelectric properties of PbSnTe:In films obtained by molecular beam epitaxy and photosensitive structures in the far infrared and submillimeter ranges based on these films. The parameters of photodetector arrays of this type and detectors based on doped semiconductors and superconductors are compared. One-dimensional (2×128 elements) and two-dimensional (128 × 128 elements) PbSnTe:In based arrays with a sensitivity threshold of ~22 μm and an operating temperature of T ≤ 16 K are implemented. Under background-free conditions, the noise equivalent power (NEP) was NEP ≤ 10−18 W/Hz0.5 at T = 7 K for a black body radiation source at TBB = 77 K. In the submillimeter range of the spectrum, sensitivity to laser radiation with a wavelength λ ≤ 205 μm and a value NEP ≤ 10−12 W/Hz0.5 was observed without optimization of the design of the photosensitive element and minimization of the measurement circuit noise. The directions of the development of PbSnTe:In based radiation detectors are considered..

Applicability of a KTA crystal-based laser system with optical parametric oscillators (OPO) generation to lidar sounding of the atmosphere in the spectral range 3-4 mu m is studied in this work. A technique developed for lidar sounding of trace atmospheric gases (TAG) is based on differential absorption lidar ( DIAL) method and differential optical absorption spectroscopy (DOAS). The new technique uses broadband radiation and a CCD detector, which ensures measurement of backscattering signals with simultaneous altitude and wavelength resolution. The DIAL-DOAS technique is tested to estimate its efficiency for lidar sounding of atmospheric trace gases. The numerical simulation performed shows that a KTA-based OPO laser is a promising source of radiation for remote DIAL-DOAS sounding of the TAGs under study along surface tropospheric paths. The laser system design provides a possibility of narrowing the laser line within the 0.01-5 cm(-1) limits. This possible improvement along with a small step of laser line tuning and the presence of absorption lines of other atmospheric gases, including atmospheric pollutants, in the spectral range under study make this laser a unique instrument for atmospheric sounding.

A method of formation and heating of CO 2 as a test gas in the settling chamber of a hotshot wind tunnel is considered. To form and heat CO 2 , the chamber is filled with a source gas mixture of CO, O 2 , and CO 2 , and after initiation, these substances participate in an exothermic chemical reaction in accordance with the formula CO + 0.5 O 2 + x CO 2 = (1 + x )CO 2 . A stoichiometric ratio of the concentrations of carbon monoxide CO and oxygen is used. Variation of the number of moles x of ballast CO 2 in the left part of the chemical formula allows changing the temperature of the resultant test gas in a wide range. Experiments in the IT-302M hotshot wind tunnel carried out at ITAM SB RAS have shown that a pressure increase during an isochoric process in the settling chamber due to the joint effect of heat released in the reaction CO + 0.5 O 2 and an electric charge provides the completeness of CO combustion almost equal to unity. The time of reaction completion at its initiation by an electric arc is no more than several milliseconds.

With results of testing various models for several last years, the article will describe the capabilities of the IT-302M hotshot wind tunnel in terms of modeling of high-velocity flows in the Mach number range from 4 to 20 for external flow regimes and from 2 to 6 for the attached pipeline regime with the following flow parameters: total pressure from 5 to 1000 bar and total temperature from 700 to 3500 K. Some of these pioneering activities are unique: for instance, a positive thrust force was obtained in a scramjet model for the first time; a series of tests was performed for comparisons of the results of inlet flows obtained in hotshot and blow down wind tunnels, including shock starting of the inlet and a possibility of its modeling by using a special device in the long-duration wind tunnel. A new concept of a short-duration wind tunnel with opposing pistons of pressure multipliers has been considered.

Рассмотрена модель Pb1-xSnxTe:In, основанная на представлениях теории неупорядоченных систем, проведены расчеты температурных зависимостей положения уровня Ферми и концентрации носителей заряда в зависимости от уровня легирования индием и их сравнение с экспериментальными данными. Проведен расчет нестационарных вольт-амперных характеристик в режиме инжекции из контакта и ограничения тока пространственным зарядом при различных скоростях изменения напряжения, выполнено сравнение полученных данных с экспериментом и показано, что вид характеристик определяется параметрами захвата электронов на локализованные состояния. Исследованы релаксации фототока в магнитном поле и обсужден механизм таких релаксаций в предположении о магнитном вымораживании носителей заряда.

Possibility of application of a laser system with parametric light generation based on a nonlinear KTA crystal for lidar sensing of the atmosphere in the 3–4 μm spectral range is investigated. A technique for lidar measurements of gas components in the atmosphere with the use of differential absorption lidar (DIAL) and differential optical absorption spectroscopy (DOAS) method is developed. The DIAL-DOAS technique is tested for estimating the possibility of laser sensing of minor gas components in the atmosphere.

A method for raising the maximum settling-chamber pressure in a short-duration wind tunnel equipped with pressure multipliers arranged in opposition to each other for stabilization of test gas parameters is proposed. For this purpose, a wind-tunnel design with an additional third pressure multiplier attached to the body of the second pressure multiplier was developed. The rod of the additional multiplier contacts the large-area piston stage of the second multiplier, and the pre-piston space being connected to the receiver. The inclusion of an additional pressure multiplier in the wind-tunnel design at the maximum attainable driver-gas pressure of 150−170 bar, defined by the standard industrial pressure of air used for filling wind-tunnel receivers with the driver gas, allows a two-fold increase in the maximum settling-chamber pressure, from 1100 to 2000−2200 bar. For raising the maximum settling-chamber pressure above 2000–2200 bar, the use of one additional pressure multiplier proved to be insufficient because, in the latter case, its becomes necessary to simultaneously raise the driver-gas pressure over 150−170 bar.

Applicability of a KTA crystal-based laser system with optical parametric generation to lidar sounding of the atmosphere in the spectral range 3-4 mu m is studied in this work. A technique developed for lidar sounding of trace atmospheric gases is based on differential absorption (DIAL) technique and differential optical absorption spectroscopy (DOAS). The DIAL-DOAS technique is tested to estimate its efficiency for lidar sounding of atmospheric trace gases.

A laser system is designed that provides for tunable generation of nanosecond radiation pulses in the 3-4 mu m range. Optical block-diagram and specifications of the system are presented. The laser system as a part of a differential absorption lidar designed can be used for remote control of pollutant concentrations along surface atmospheric paths.

A method and system for sampling a chemically active gas from a hypersonic flow with high stagnation parameters are developed. Results of an experimental study of the test gas composition at the nozzle exit of the IT-302M hotshot wind tunnel based at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences are presented. As the air in the settling chamber is heated up to 3000 K by an electric arc only, the volume fraction of oxygen in the test section decreases from 21 to 18%, which may require supplying an additional amount of oxygen into the settling chamber as a compensation for its reduction in some tests of gas-dynamic models with combustion. In the case with hydrogen used together with the electric arc for increasing the energy of the facility, the degree of completeness of the reaction of hydrogen combustion in air in the settling chamber is determined. For the minimum possible supply of electric energy for the IT-302M wind tunnel (based on conditions of arc combustion stability), the hydrogen combustion efficiency is ≈0.9 for extremely lean hydrogen-air mixtures with the hydrogen concentration much lower than the flammability limits under standard conditions. The combustion efficiency rapidly approaches unity as the hydrogen concentration in the settling chamber and the electric energy supply are increased.

Calculated parameters of the gas flow in the test section of a high-enthalpy short-duration wind tunnel (IT-302M hotshot wind tunnel) are compared with experimentally determined values. It is demonstrated that the differences in flow characteristics in the test section measured by two methods [flow rate determined by the method of flask filling and physical velocity determined by particle image velocimetry (PIV)] and the calculated values is within several percent. The experimental results show that the assumptions taken for calculating the flow parameters in the test section ensure a fairly accurate description of the processes in the gas-dynamic duct of the hotshot wind tunnel. The most significant differences between the calculated and experimental values are found to be induced by two factors: neglect of heat losses from the test gas (gas flow) to the walls of the first settling chamber and uncertainty in reconstructing the pressure level in the first chamber at the time t = 0.

A high-enthalpy short-duration wind tunnel (hotshot wind tunnel) is designed for different operation modes ensured by combining various methods of test gas heating [by an electric arc, chemical energy, adiabatic compression, and heating in an external source of heat (with respect to the settling chamber)]. The wind tunnel is designed for the following ranges of parameters: stagnation pressure p 0 = 1–200 MPa, stagnation temperature T 0 = 600–4000 K, Mach number M = 4–20, and test time t < 1 s. The wind tunnel can operate both in the regime of the classical hotshot facility with decreasing parameters of the test gas and in the regime with stabilization of parameters owing to synchronized motion of the opposite pistons of the pressure multiplier toward each other.