Inversion phenomena with energy separation in a gas ejector

The article considers inverse phenomena, with energy separation in a classical gas ejector, consisting in the fact that the cold and hot air zones change places, depending on the throttling conditions at the inlet and outlet of the ejector.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 187–188, September–October, 1976.     

A gas ejector system and a differential ejector

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 6, pp. 10–15, November–December, 1991.     

Neutralizer with a gas ejector

A neutralizer model with a gas ejector is studied, whose main element (a sonic nozzle) is a gap between two conical surfaces. Static pressure distributions were measured along the axis of the neutralizer at different gas pressures in the receiver. Stagnation pressure, total flow, gas target thickness, flow separation factor, Knudsen number, and gas-dynamic performance of the neutralizer were calculated from the gas pressure values on the axis of the neutralizer at the point with the coordinate z/d = 3, and static pressure distributions in the characteristic cross sections of the neutralizer were obtained.     

Theory of the energy separation of a compressible gas flow

Optimum gas parameters which ensure the maximum heat transfer across a flat plate separating two streams with different Mach numbers are found on the basis of an exact self-similar solution for a laminar boundary layer.     

Effect of energy supply to a gas on laminar boundary layer separation

A decelerated flow in a supersonic boundary layer containing a heat source modeling an electric discharge is studied numerically. Calculations are performed for a wide range of the source power. The possibility of controlling the boundary layer separation is demonstrated. The boundary layer separation on cooled walls is found to occur substantially later than on thermally insulated walls.     

Self-similar solutions for energy liberation in a gas stream

By using dimensional analysis some possible kinds of nonstationary and stationary gas flows with energy liberation which result in self-similar problems are investigated. The cases of energy liberation in a gas at rest and in uniform supersonic and hypersonic streams are examined. The gas is assumed inviscid and perfect. Results of a computation of some hypersonic self-similar gas motions are presented. Three classes of self-similar gas motions have been well studied at this time: the strong explosion, the power-law flow caused by the expansion of a plane, cylindrical, or spherical piston [1], and conical flow (including combustion and detonation waves [2–4]). Some new self-similar motions caused by energy liberation on certain lines, surfaces, or in volumes will be examined below.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 106–113, November–December, 1974.     

Momentum transfer in a vertical down flow liquid jet ejector: case of self gas aspiration and emulsion flow

Momentum transfer in a vertical liquid jet contactor consisting of an ejector supported in a vertical column has been studied, using three different liquids as motive fluids, and air as the entrained gas.On the basis of macroscopic momentum and energy balance, an overall loss factor is derived. Moreover, an empirical correlation is proposed to predict the mass flow rate of entrainment by the liquid jet system. Finally, an expression to predict the volumetric flow rate of the carried fluid available at a pressure higher than atmospheric, is given.     

The effects of the secondary fluid temperature on the energy transfer in an unsteady ejector with a radial-flow diffuser

Unsteady ejectors are devices whereby energy is exchanged between directly interacting fluids. Unlike steady ejectors, the mechanism responsible for the energy transfer is reversible in nature and thus higher efficiencies are perceivable. A potential application for PEE is for enhancement in output power per weight as in turbochargers. The unsteady ejector when used as a turbocharger the device is expected to perform under wide range of ambient temperatures. Therefore, it is important to investigate the effects of the temperature of the induced ambient air on the energy transfer. The radial-flow ejector, which usually leads to higher-pressure ratios with fewer stages, was selected for the investigation. The flow field is investigated at two Mach numbers 2.5 and 3.0 utilizing rectangular short-length supersonic nozzles for accelerating the primary fluid. Fundamental to the enhancement of these devices performance relies on the management of the flow field in such a way to minimize entropy production. The numerical analyses were conducted utilizing a package of computational fluid dynamics.     

Mechanism of turbulent boundary layer separation from a smooth wall

The mechanism of turbulent boundary layer separation under the influence of a positive pressure gradient is analyzed. The process of turbulent separation from a smooth wall in a plane diffuser channel has been experimentally investigated. It is shown that separation is determined by the nature of the flow in a certain inner part of the boundary layer, where the friction effect is unimportant. This region of the boundary layer is most exposed to the action of the positive pressure gradient and it is there that the stagnant zone primarily appears.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 69–77, November–December, 1990.     

Theoretical investigation of the combined flow of a two-dimensional,high-pressure stream and a one-dimensional,low-pressure stream of ideal gas in ejector nozzles

On the basis of [1] an improved method was developed which, within the framework of the model of an ideal gas, allows one to calculate the flow in ejector nozzles without a limit on the coefficient of ejection. During the development of the method it was established, on the basis of a preliminary analysis, that the difference equations which approximate the differential equations of the flow of coaxial streams in an ejector nozzle (high-pressure and low-pressure streams, treated in two-dimensional and one-dimensional approximations, respectively) have a singular point. Owing to the finiteness of the integration step the position of this singular point differs in the general case from the position of the singular point for the differential equations describing the flow under investigation. This difference is larger the smaller the coefficient of ejection. Now allowing for this fact in the existing methods of calculation in an analogous formulation [1–4] limits the possibilities of all these methods, as a rule, to cases of relatively large coefficients of ejection.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 110–116, November–December, 1978.The authors thank A. N. Kraiko for useful discussions and attention to the work.     

Contribution to the theory of the high compression ratio gas ejector with cylindrical mixing chamber

Ways of improving the operation of a gas ejector with a high compression ratio are investigated. The conditions for obtaining the maximal compression ratio at the critical operating regime of the gas ejector are studied theoretically and experimentally with account for mixing of the supersonic injecting and subsonic ejected streams ahead of the choking section. The principles for the rational utilization of the effect of stream mixing in the ejector ahead of the choking section are indicated; the use of these principles permits a several-fold increase of the compression ratio of the supersonic ejector. A theory is given for the critical regime of the gas ejector with uniformly perforated nozzle, and the hydraulic parameters of the required wall perforationss are determined. It is shown that perforation as a hydraulic factor can improve significantly the parameters of the sonic ejector in the critical regime.The foundations of modem gas ejector theory were developed by Khristianovich [1, 2]. In these studies he established the relationship between the parameters of the flow at the end of the mixing chamber (section 3, p ₀ is the total pressure, is the reduced velocity) and the parameters of the ejecting (section 1, p ₀ ,) and the ejected (p₀₁,₁) flows with account for compressibility for the ejector with a cylindrical mixing chamber (Fig. 1a). The ejector theory [1, 2] (see also [3, 4]) is given in the hydraulic approximation: the flow at the end of the mixing chamber is assumed uniform, flow friction on the mixing chamber walls is neglected. The use of the gasdynamic functions [5–9] made it possible to obtain computational equations for the ejector in a convenient form and to extend them to the case of mixing of gases with different thermophysical properties. We note that for subsonic velocities of the ejecting and ejected flows the system of ejector equations [1, 2] is supplemented by the condition of equality of the static pressures p=P₁ at the stream contact section 1.The results of extensive experimental studies of subsonic ejectors are in good agreement with the results of this theory.For sonic or supersonic velocity of the ejecting gas (=1) the condition p=p₁ is not satisfied in the general case. Fundamental for the development of ejector theory was the establishment by Millionshchikov and Ryabinkov in 1948 of the existence of a critical operating regime of the supersonic ejector [7, 10]. They showed that the limiting operating regimes of the gas ejector for high pressure differentials ==p ₀ /p₀₁ are determined by the conditions for the choking of the ejected jet by the expanding supersonic ejecting flow. With the occurrence of the critical regime the velocity of the ejected jet at the choking section (section 2, Fig. 1a) reaches the speed of sound (=1); this limits the further increase of the pressure ratio and the ejector compression ratio =p ₀ /p ₀ for a given ejection coefficient k (k is the ratio of the ejected and ejecting gas flow rates). The relationships between these flow parameters at sections 2 and 1 supplement the system of ejector equations and permit determining its critical characteristics.Millionshchikov and Ryabinkov showed that for moderate values of the pressure ratio good agreement of the theoretical and experimental ejector characteristics are given by the assumption of constant static pressure p₂=const at section 2 (Fig. 1a).The limit of the applicability of the theory based on the condition p₂= = const, was studied experimentally by Lyzhin [10].The theory of the critical regime of the gas ejector was developed in 1953 in studies of Nikol'skii, Shustov, Vasil'ev, Taganov, and Mezhirov [10, 11]. Nikol'skii showed that the condition of constant static pressure at the choking section is not in agreement with the momentum equation.For a more rigorous theoretical determination of the critical ejector regime he proposed joining between sections 1 and 2 (Fig. 1a) the calculation of the ejecting jet using the method of characteristics and the hydraulic calculation of the ejected jet; example calculations were made by Nikol'skii and Shustov. Taganov and Mezhirov suggested a method for calculating the ejector critical regime using a linear distribution of the pressure in the supersonic ejecting jet (at the choking section 2).A simple and successful method for calculating the ejector critical regime was given by Vasil'ev, who used the hydraulic representation of the ejecting and ejected flows in the choking section; both flows are assumed uniform at section 2, the static pressures in these flows in the general case are different and are determined by the momentum equation. A similar theory for the ejector critical regime was developed independently in [12, 13], and the theory with account for the supersonic ejecting flow (ahead of the choking section) was developed using the method of characteristics in [14].It should be noted that the results of the calculations of the critical characteristics of the ejectors using all three of these methods were practically indentical and in good agreement with experiment for large and moderate values of the ejection coefficients. We emphasize that in the theories of the ejector critical regime the flow mixing between sections 1 and 2 is neglected.The critical regime theory imposes significant limitations on the possible characteristics of the gas ejector, first of all, on the achievable compression ratio =p ₀ /p ₀ . Thus, from the data of [10], even for a pressure ratio =1000 the maximal theoretical value of the compression ratio for the supersonic ejector does not exceed 40 (see in Fig. 2 the limiting ejector characteristics based on the critical regime theory); for the sonic air ejector (=1) the theoretical value of 3.5 (see Fig. 9b on p. 26). Therefore it is important to analyze the methods for influencing the critical regime parameters in order to determine ways to improve the operation of the gas ejector with a high compression ratio.     

Turbulent flow of gas in a curvilinear channel in the presence of suction from a separation region

Integral parameters that characterize reversible and irreversible changes in the flux of the total pressure in channels with perforated walls are introduced. An experimental investigation was made of subsonic gas flow in curvilinear channels of rectangular cross section in the presence of suction of gas from a separation region of the flow formed on an internal (convex) strongly curved wall of the channel. The optimal position of the suction slit was determined and it was shown to be possible to reduce appreciably the loss in the channel and improve its gas-dynamic characteristics. Two-dimensional turbulent flow of an incompressible fluid in curvilinear channels in the presence of suction was simulated numerically. The mathematical model is based on the complete system of Navier-Stokes equations, additional differential equations for the energy of the turbulence and the rate of its dissipation, special correction equations to take into account the curvature of the streamlines, and model boundary conditions for the sections of the walls through which the suction of the fluid takes place.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhldkosti i Gaza, No. 4, pp. 72–80, July–August, 1984.     

Small-amplitude nonlinear waves in a dissipative gas with excess vibrational energy

By means of the method of two-scale expansions the results of studies [3–5] are extended to the case of cylindrical and spherical waves, and an equation for the gas velocity which takes dissipative processes into account is derived for one-dimensional plane small-amplitude nonlinear waves. A number of exact particular solutions of this equation is found. Since the accuracy of solutions obtained by means of approximate methods in problems of the type in question has not previously been estimated, the limits of applicability of the analytical method employed are established by comparing the results with numerical calculations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 151–158, March–April, 1990.The authors are grateful to M. S. Ruderman for useful discussions.     

Numerical and experimental evidence of the Fabri-choking in a supersonic ejector

The purpose of a supersonic ejector consists in the mixing of two fluids with different stagnation pressures in order to obtain a fluid at an intermediate stagnation pressure at the discharge. Depending on the geometry of the ejector and on the operating conditions, the entrained secondary stream may reach sonic/supersonic velocities within the ejector, leading to the capping of the entrained mass flow rate for fixed reservoir conditions. Although the associated limitation of the entrainment ratio (due to choking) is a well known phenomenon, there is still a lack of understanding of the complex flow phenomena at play within supersonic ejectors, and further detailed knowledge and modeling of the choking process is necessary. This paper presents a detailed analysis of the choking phenomenon through advanced post-processing of CFD calculations which are validated with experimental results both at the global and the local scales. This in-depth investigation of the choking phenomenon within the ejector is proposed both qualitatively and quantitatively for given reservoir conditions. The complex flow signature highlighted by means of the numerical results is then investigated and corroborated through experimental shadowgraphy. Studies combining experimental results (including visualizations) with numerical simulations are rather scarce in the open literature and to the knowledge of the authors, this study is the first one that proposes such a detailed analysis. For the present ejector geometry and operating conditions, the choking phenomenology of the secondary stream is found to closely correspond to the model of the Fabri-choking early postulated in Fabri and Siestrunck (1958).