Multiatomic Gases Research Articles

Inhibition of the reaction between hydrogen and oxygen by multiatomic gas admixtures behind the incident shock wave front

The inhibiting effect of multiatomic gases has been investigated by numerical simulation of hydrogen oxidation with account taken of the nonequilibrium state of the initial components, intermediates, and reaction products behind the shock wave in the framework of a vibrationally nonequilibrated model. The central feature of the model is successively taking into account the vibrational disequilibrium of the HO2 radical as the most important intermediate in the chain branching process. The inhibiting effect can be explained by the influence of the multiatomic gases on the rate of the vibrational relaxation of the vibrationally excited HO2 radical resulting from the reaction. Methane, tetrafluoromethane, fluoromethane, difluoromethane, chlorofluoromethane, formaldehyde, ethane, hexafluoroethane, ethylene, tetrafluoroethylene, and propane have been considered as inhibitory admixtures.

Existence of renormalized weak solutions to the steady equations describing compressible fluids in barotropic regime

We investigate the steady compressible Navier–Stokes system describing compressible fluids in barotropic regime in a bounded three-dimensional domain with slip boundary conditions. Considering a general pressure law of the form p=p(ϱ), where p(ϱ) is increasing at infinity with the rate ϱγ, we show existence of renormalized weak solutions for γ>1. This improves considerably the recent result of Frehse et al. (2012) [9] which requires γ>4/3, and thus allows to treat various multi-atomic gases as well as the relativistic gas where γ=4/3. This result is obtained by using an original bootstrapping argument suggested in Jiang and Zhou (2011) [13] to estimate the density combined with a new potential type estimates up to the boundary obtained via a testing of the momentum equation by a specially constructed test function.

Investigation of the Properties of Substances on the Boundary Curves of Liquid-Vapor Phase Transition

A new approach to construction of generalized dependences for different properties of substances is proposed. A study is made of the changes in the difference in the properties of various substances on the boundary curves of liquid-vapor phase transition. Generalization results obtained in processing of experimental data on the thermodynamic and transport properties of substances on the boundary curves of liquid-vapor transition of monatomic and multiatomic gases, normal and polar organic and inorganic liquids, alkali metals, and mercury are discussed. An analogous approach may be used in studying solid body-liquid and solid body-gas phase transitions.

Kinetic Coefficients in the Boundary-Value Problem on the Slip of a Multiatomic Gas with Rotational Degrees of Freedom

The boundary-value problem on the slip of an inhomogeneous multiatomic gas along the spherical surface of small curvature is solved. For this purpose, a model kinetic equation that includes the rotational degrees of freedom of molecules is proposed. The solution is performed using the method of half-space moments. Gas-kinetic slip coefficients and jumps of macroscopic parameters of gas of the first and second order in the Knudsen number are obtained. These gas-kinetic coefficients are represented in the form of functions depending on the accommodation coefficient of tangential momentum, on the accommodation coefficients of the translational and rotational components of energy, and on the Prandtl number. For a number of multiatomic gases, calculations of the above-mentioned coefficients are performed.

Role of highly efficient collisions in collisional transfer of vibrational energy in benzophenone-foreign gas mixtures

Collisional losses of vibrational energy in mixtures of benzophenone excited by nitrogen laser radiation (λ=337 nm) and foreign gases (Ar, Kr, SF6, C5H12) were studied by time-resolved delayed luminescence. It is established that the intensities and rates of decay of the fast and slow components of delayed luminescence can be used to evaluate the characteristics of V–V– and V–T–transfer of vibrational energy. For the V-V-process, the efficiencies and mean energies transferred in a collision are determined. It is shown that in the mixture with multiatomic gases, vibrational equilibrium is reached after a few collisions, the number of which decreases as the molecule of the foreign gas becomes more complicated. The V–V–process is characterized by high efficiencies of collisions typical for “supercollisions”. The experimental characteristics of V-V-transfer correlate well with ergodic transfer of vibrational energy predicted by statistical theories. 0120 0126 V 3

On the effect of the thermomagnetic pressure difference and the scott effect

The effect of the thermomagnetic pressure difference and the Scott effect are considered, accounting for nonlinear temperature stresses. For a gas of linear diamagnetic molecules, shear nonlinear temperature stress coefficients are determined as functions of the magnetic field frequency. For multi-atomic gas, shear and bulk temperature stress coefficients are obtained in the absence of a magnetic field.

Ring‐opening metathesis polymerization of norbornenes with organosilicon substituents. Gas permeability of polymers obtained

AbstractPolymers of norbornenes with SiMe3 and Si(Me2)CH2SiMe3 groups were synthesized and mass transfer properties of the polymers were studied. Ring‐opening polymerizations of these monomers were realized in the presence of homogeneous WCl6‐based and heterogeneous Re2O7‐based metathesis catalysts. Introduction of silicon‐containing groups in the polynorbornene main chain results in a drastic increase of the permeability (P) and diffusion (D) coefficients for different biatomic and multiatomic gases. Comparison of polymers having SiMe3 and Si(Me2)CH2SiMe3 substituents shows lower permeability and diffusion coefficients in the latter case. The combination of transport properties (Pi values) and separation factors aij = Pi/Pj of the two new silicon‐containing polynorbornenes permits one to consider them as representatives of the most permeable and sufficiently permselective group of polymers. Transport properties of the polymers studied were analysed on the basis of the free volume approach.

Correlation aspects of the selective gas permeabilities of polymeric materials and membranes

Although the solubility and diffusivity of each gas in each polymer are temperature- and may be pressure-dependent properties of every system nevertheless regular trends are noted when either many gases are studied in a single polymer or a single gas is studied in many polymers. Several empirical though scientifically based correlations of such data have been proposed which are at best semi-quantitative. In this paper improved correlations are described to correlate data on diffusivities D and the related energies of activation, and solubilities S and related heats of solution of gases in polymers. The procedures rely on determining an effective Lennard-Jones force constant and molecular diameter for each gas, which parameters hold in all polymers above T g and, with slightly smaller diameters for the multiatomic gases, in all polymers below T g. Each polymer is characterized by four temperature-dependent parameters, two for diffusivity and two for solubility, which hold with all gases. Rules are given for determining these parameters. It is demonstrated that D is correlated to within ±20% and S to ±30%. The procedure described may be used to predict D and S, and hence permeabilities, in cases where data do not already exist. The values and ratios of the predicted permeabilities are a valuable guide when seeking polymers for separating gas mixtures by membrane processing.

Application of the theory of similarity for purposes of generalizing the thermal-diffusion factor for mixtures of multiatomic nonpolar gases

The thermal-diffusion factor of 14 nonpolar-gas mixtures has been generalized on the basis of similarity theory. The theoretical values of αth obtained on the basis of this generalized relationship are compared with the experimental data.

Relaxation processes in multiatomic gases. II

The kinetic equation for an optically inactive component of a mixture of gases is solved in the dissipative approximation. The transport coefficients, the relaxation pressure, and the sources in the equations of the kinetics and relaxation gas dynamics are determined. A diatomic gas with weak excitation of the vibrational states of the molecules is considered, and the relaxation pressure and the relaxation times are determined in the two-moment approximation. The kinetic equations and the equation of radiative transfer are determined in the nondissipative approximation for vibrational-rotational relaxation.

Relaxation processes in multiatomic gases. I

The kinetic equation for an optically inactive component of a mixture of gases is solved in the dissipative approximation. The transport coefficients, the relaxation pressure, and the sources in the equations of the kinetics and relaxation gas dynamics are determined. A diatomic gas with weak excitation of the vibrational states of the molecules is considered, and the relaxation pressure and the relaxation times are determined in the two-moment approximation. The kinetic equations and the equation of radiative transfer are determined in the nondissipative approximation for vibrational-rotational relaxation.

Experimental study of heat exchange in a moderately rarefied gas

An experimental study is performed of heat exchange in multiatomic gases at moderate Knudsen numbers in coaxial geometry. The data obtained are described well by the Liu-Lees theory of multiatomic gases.

Mean-photon-path approximation in the theory of IR-radiation transfer in mixtures of vibrationally nonequilibrium multiatomic gases

Mean-photon-path approximation in the theory of IR-radiation transfer in mixtures of vibrationally nonequilibrium multiatomic gases

Transfer of nonequilibrium IR radiation in mixtures of multiatomic gases

The kinetic equations which form the basis and lead to vibrational temperatures of an arbitrary of a mixture of multicomponent gases is presented. This, in turn, forms a complete system in in combination with the equations of radiant gas dynamics and these are presented and analyzed.

Nonisothermal flow of a rarefied multiatomic gas in a channel

The authors consider the slow flow of a polyatomic gas in a plane channel, bounded at x = + or - d/2 by two infinite parallel planes. Interest in nonisothermal flow in channels and the thermomolecular pressure difference produced by conductivity, which give experimental data on the total thermal conductivity of polyatomic gas provides an independent source of data on internal energy relation times, which are usually determined by experiments on ultrasound absorption or other methods.

Heat and mass transfer of a multiatomic gas in a cylindrical capillary with arbitrary Knudsen numbers

Processes of heat and mass transfer of a multiatomic gas in a cylindrical channel of circular cross section with arbitrary Knudsen numbers are considered on the basis of a model kinetic equation, taking account of the excitation of rotational and vibrational degrees of freedom of the molecules.

Region of applicability and the main features of the generalized Chapman-Enskog method

The present paper is made necessary by the publication of the foregoing paper in this issue by Kolesnichenko [1]. It considers the basic propositions of the generalized Chapman-Enskog method and analyzes the arguments put forward by Kolesnichenko [1] and the validity of the method. The position of the results obtained by Kolesnichenko [14–17] is indicated. Nonequilibrium flows of multiatomic gases in which there occur processes of exchange of internal energy of the molecules in collisions between them and chemical reactions (such processes are called inelastic) are encountered frequently in nature and technology. It is therefore naturally of interest to derive gas-dynamic equations for such flows. The methods of the kinetic theory of gases were first used to obtain equations describing the limiting cases of very fast inelastic processes that take place in times of the order of the molecule-molecule collision times (equilibrium case) and very slow inelastic processes that take place over times of the order of the characteristic flow time (relaxation case). In [2–5], an algorithm was proposed for deriving gas-dynamic equations valid for arbitrary ratios of the rates of the elastic and inelastic processes and reducing to the well-known equations for the limiting cases already mentioned. The algorithm is called the generalized Chapman-Enskog method (abbreviated to the generalized method). The development, modification, and analysis of its properties can be found in [4, 6–13]. In [1], Kolesnichenko has questioned the validity of this algorithm.

Nonequilibrium processes in moderately dense multiatomic gases. II

Nonequilibrium processes in moderately dense multiatomic gases. II

Nonequilibrium processes in moderately dense multiatomic gases. I

Nonequilibrium processes in moderately dense multiatomic gases. I

Effects of vibrational relaxation of multi-atomic molecules on stagnation heat transfer

The flow and temperature fields of multi-atomic gas near the stagnation of a cylinder are theoretically studied, taking molecular vibrational relaxation into account, and putting importance on heat transfer performances. Based on the continuum equations, the velocity and temperature jumps of translational, rotational and vibrational degrees are considered as the boundary conditions and effects of the vibrational relaxation for subsonic flow are discussed. The total heat transferred to the surface is the sum of heats due to the translational-rotational temperature and the vibrational temperature. The ratio of the heats depends much on the ratio of the flow characteristic time to the relaxation time of molecule, and consequently the total heat is much influenced by this ratio of the characteristic times. The effect of the flow-relaxation time on heat transfer is more remarkable in the vibrational nonequilibrium than in the thermal equilibrium main flow. Even in a continuum flow of Knudsen number of about 10 −4, the effect of vibrational relaxation on stagnation heat transfer is still appreciable.