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Increasingly, low-capacity electricity generating installations using renewable energy sources are becoming widespread. They bring imbalance to the energy system. Frequency control is carried out using powerful steam turbines. To ensure reliable and efficient operation of powerful steam turbines, it is important to understand the processes occurring in the last stages of the low-pressure cylinder. At present, there is no approach to determining the idle mode (the moment of transition from the generation of mechanical power to its consumption) for large fanning stages. The purpose of the work is to develop an approach to estimating the relative volumetric steam flow rate of steam for large fanning stages, which characterizes the idle mode. This goal is achieved by developing a dependence to determine the idle mode for large fanning stages at nominal operating mode in a compressible medium using the results of an experimental study of model stages for high power turbines. The most important result is the satisfactory agreement between the values of volume flow rate obtained during the calculation, using the proposed method, with experimentally studies for the T-250/300-240 turbine last stage. The calculation error is about 3%. The significance of the results obtained is that the proposed approach allows determining the idle mode of the low-pressure cylinder stages of steam turbines quickly and ac-curately during operation and design, which makes it possible to increase the efficiency and reli-ability of power units.

A partially spherically symmetric exact solution of dynamics of a heat-conducting medium with the thermodynamic equations of state of a perfect gas for which the viscous stress tensor depends on the strain-rate tensor in an arbitrary way is given. It is assumed that the strain rates and the pressure are homogeneous and there is no acceleration; in this case, the equations of motion are identically satisfied. As a result of separation of variables in the energy equation, the three-dimensional Poisson equation is obtained for the density as a function of the Lagrangian coordinates. Its solution simulates compression of a domain of significantly variable density in the medium considered, for example, in the case of full spherical symmetry of a buble or a drop. Non-spherical constant-density surfaces are also possible. Flow can occur from the state of rest with a finite mass of the medium due to the motion of the compressing spherical piston. The power-law non-Newtonian liquids are investigated. The energy of medium is calculated and its behavior is presented in the neighborhood of the instant of compression to a point. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the evaluation of quasi-static equilibrium solutions for inflatable space membrane structures. A Mooney–Rivlin hyper-elastic material model, with variable constitutive constants, is considered. A compressible weightless medium is used to introduce within the membrane a one-parametric over-pressure loading compared to an ambient pressure. Analytical instability results are shown for a spherical and derived for a cylindrical case. These are compared to numerical simulations based on a flat linearly interpolated triangular space membrane element. Path-following procedures are used to find generalized equilibrium paths, with different parameterizations. Numerical examples show that the methods developed can give information on the stability of the membranes, but that the medium and means for introducing the internal pressure are of importance for the interpretation of stability. [Copyright &y& Elsevier]

model of flow in a Ranque vortex tube is suggested. It is based not on the thermal interaction between hot and cold flows, but rather on a mechanical one. It is shown that to describe the Ranque-Hilsch effect it is necessary, along with the radial flow, to take into account the uptake or addition of mass, as well as to ensure a smoother conjugation between a forced and a peripheral vortices, demanding the continuity not only of the tangential velocity component, but also of its first derivative with respect to the radius. In this case, the motion in the vortex tube is considered as a system of vortex flows and vortex sources interacting between themselves. [ABSTRACT FROM AUTHOR]