Investigation of transonic unsteady-state flow in the presence of phase transformations

Saltanov, G. A.; Tkalenko, R. A.

doi:10.1007/bf00852813

Cited by 12 publications

(5 citation statements)

References 7 publications

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“…The first numerical results for unsteady two-phase nozzle flows with non-equilibrium condensation of water vapour obtained with a one-dimensional code were presented by Saltanov & Tkalenko (1975) and compared with experiments. Here two oscillation modes (which we will denote by 1 and 2) were presented.…”

Section: Introductionmentioning

confidence: 99%

Instabilities and bifurcation of non-equilibrium two-phase flows

Adam

Schnerr

1997

J. Fluid Mech.

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New instabilites of unsteady transonic flows with non-equilibrium phase transition are presented including unsymmetric flow patterns with moving oblique shock systems in supersonic nozzles with perfectly symmetric shapes. The phenomena were first detected when performing experiments in our supersonic wind tunnel with atmospheric supply and could be perfectly reproduced by numerical simulations based on the Euler equations, i.e. neglecting the viscosity of the fluid. The formation of the liquid phase is modelled using the classical nucleation theory for the steady state together with the Hertz–Knudsen droplet growth law and yields qualitatively and quantitatively excellent agreement with experiments in the unsteady flow regime with high-frequency oscillations including the unstable transient change of the structure from symmetric to unsymmetric flow.For engineering applications the sudden increase or decrease of the frequency by a factor 2 or more and of the pressure amplitude at the bifurcation limits is of immediate practical interest, e.g. for flutter excitation of turbomachinery blading.

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Section: Introductionmentioning

confidence: 99%

Instabilities and bifurcation of non-equilibrium two-phase flows

Adam

Schnerr

1997

J. Fluid Mech.

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“…20 Mach -Zehnder interferograms of one periodic cycle of self-excited oscillations of condensing flow in nozzle No. 7 (see Table 1), flow from left, starting at left column from top; frequency f ¼ 749 Hz; indraft wind tunnel experiment, operating with atmospheric humid air, reservoir conditions: f 0 ¼ 83%, x ¼ 9.5 g vapour /kg dry air , original picture from Barschdorff [16] water vapour were presented by Saltanov and Tkalenko [18]. They applied an extended Gudunov method to solve the one-dimensional Euler equations coupled with the classical nucleation theory of Frenkel.…”

Section: Self-excited Oscillations In Laval Nozzlesmentioning

confidence: 99%

Unsteadiness in Condensing Flow: Dynamics of Internal Flows with Phase Transition and Application to Turbomachinery

Schnerr

2005

Proceedings of the Institution of Mechanical Engineers, Part C:

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Steady flows of condensable fluids may become unsteady if one component of the fluid starts to condense. In high-speed expansion flows, typical for large-scale steam turbines, the subcooled vapour state collapses after nucleation, typically in flow regimes close to Mach number 1. After the formation of steady shocks, instantaneous thermal choking initiates selfexcited high-frequency oscillations which is the focus of this article. The driving mechanism is the interaction of compressibility and energy supply in flows close to maximum mass flux density and is therefore not controlled by the viscosity of the fluid. Additional viscosity-driven excitation mechanisms exist and superpose the primary diabatic instability, especially in axial cascades. Typical are shedded shear layers from blade trailing edges and the periodic interference of wakes separating from the stator with the rotor blades. This article presents a review of the authors and various co-workers' research, supplemented by important references to complete the subject under consideration. This article starts with an introduction in the most simple flow model of given heat addition in constant area flow and ends with mixed homogeneous/heterogeneous condensation in a transonic axial cascade stage with a high-resolution sliding interface for preservation of submicron condensate convected from the stator into the rotor. Numerical simulations are compared with experiments of flows with and without carrier gas.

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“…He combined the classical nucleation theory with the Hertz-Knudsen model for droplet growth and the equations of diabatic gas dynamics. Numerical solutions for Laval nozzle flows with condensation-induced oscillations were presented by first Saltanov & Tkalenko (1975) for a quasi-one-dimensional configuration and by White & Young (1993) for the unsteady two-dimensional case. A new numerical approach was introduced by Schnerr & Dohrmann (1990) and Mundinger (1994), who described the nucleation and condensation process by solving the conservation laws for the first four moments of the droplet-size distribution function, as proposed by Hill (1966).…”

Section: Introductionmentioning

confidence: 99%

Effects of homogeneous condensation in compressible flows: Ludwieg-tube experiments and simulations

et al. 2007

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Effects of homogeneous nucleation and subsequent droplet growth in compressible flows in humid nitrogen are investigated numerically and experimentally. A Ludwieg tube is employed to produce expansion flows. Corresponding to different configurations, three types of experiment are carried out in such a tube. First, the phase transition in a strong unsteady expansion wave is investigated to demonstrate the mutual interaction between the unsteady flow and the condensation process and also the formation of condensation-induced shock waves. The role of condensation-induced shocks in the gradual transition from a frozen initial structure to an equilibrium structure is explained. Second, the condensing flow in a slender supersonic nozzle G2 is considered. Particular attention is given to condensation-induced oscillations and to the transition from symmetrical mode-1 oscillations to asymmetrical mode-2 oscillations in a starting nozzle flow, as first observed by Adam & Schnerr. The transition is also found numerically, but the amplitude, frequency and transition time are not yet well predicted. Third, a sharp-edged obstacle is placed in the tube to generate a starting vortex. Condensation in the vortex is found. Owing to the release of latent heat of condensation, an increase in the pressure and temperature in the vortex core is observed. Condensation-induced shock waves are found, for a sufficiently high initial saturation ratio, which interact with the starting vortex, resulting in a very complex flow. As time proceeds, a subsonic or transonic free jet is formed downstream of the sharp-edged obstacle, which becomes oscillatory for a relatively high main-flow velocity and for a sufficiently high humidity.

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Investigation of transonic unsteady-state flow in the presence of phase transformations

Cited by 12 publications

References 7 publications

Instabilities and bifurcation of non-equilibrium two-phase flows

Instabilities and bifurcation of non-equilibrium two-phase flows

Unsteadiness in Condensing Flow: Dynamics of Internal Flows with Phase Transition and Application to Turbomachinery

Effects of homogeneous condensation in compressible flows: Ludwieg-tube experiments and simulations

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