The purpose of the ''International Wet Steam Modeling Project'' is to review the ability of computational methods to predict condensing steam flows. The results of numerous wet-steam methods are compared with each other and with experimental data for several nozzle test cases. The spread of computed results is quite noticeable and the present paper endeavours to explain some of the reasons for this. Generally, however, the results confirm that reasonable agreement with experiment is obtained by using classical homogeneous nucleation theory corrected for non-isothermal effects, combined with Young's droplet growth model. Some calibration of the latter is however required. The equation of state is also shown to have a significant impact on the location of the Wilson point, thus adding to the uncertainty surrounding the condensation theory. With respect to the validation of wet-steam models it is shown that some of the commonly used nozzle test cases have design deficiencies which are particularly apparent in the context of two-and three-dimensional computations. In particular, it is difficult to separate out condensation phenomena from boundary layer effects unless the nozzle geometry is carefully designed to provide near-one-dimensional flow.
Realization of numerous tests on the droplet size measurement with extinction probe, in a 200 MW low-pressure steam turbine, provides necessary experimental data for testing the theoretical models of the droplet nucleation process in steam turbines. The earlier computational model accounting for the unsteady and viscous effects given by Bakhtar and Heaton and by Guha and Young, where the steam particles follow randomly chosen different streamlines within the blade rows with prescribed polytropic efficiency distribution in the pitchwise direction, thus undergoing various nucleation conditions, has been extended in this paper to consider to some extent two-dimensional effects. Because several uncertainties still exist in the inversion methods, predicting the size distribution of droplets, this contribution is aimed at direct comparison of the computed and measured transmittance data I/I 0 .
This paper presents the experimental investigations of steam flow with condensation in the blading system of the low-pressure (LP) part of a 360 MW turbine. To this end, special probes were used, which provided flow visualization opportunities including localization of the front of condensation, determining distributions of pressure, temperature, velocity, and flow angle in the inter-row gaps, measurements of water droplet concentration and sizes. The measurements have proved that the condensation process in the LP turbine might be of heterogeneous nature, depending on the concentration of chemical impurities in steam. The measurement results constituted the basis for computational fluid dynamics (CFD) flow calculations, which were performed using the time-dependent 3D Reynolds averaged Navier–Stokes equations coupled with two-equation turbulence model (k-ω SST) and additional conservation equations for the liquid phase. The set of governing equations has been closed by a “local” real gas equation of state. The condensation phenomena were modeled on the basis of the classical nucleation theory. The heterogeneous condensation model on the insoluble and soluble impurities was implemented into presented CFD code. The system of governing equations was solved by means of a finite volume method on a multiblock structured grid. The obtained numerical results and experimental data were compared and discussed.
Summary There are many low‐temperature heat sources; however, current technologies for their utilization have a relatively low efficiency and high cost. The leading technology in the low‐temperature domain for heat‐to‐work conversion is the organic Rankine cycle (ORC). Absorption power cycles (APCs) are a second option. Nearly all currently known APCs, most importantly the Kalina cycle, use a water‐ammonia mixture as their working fluids. This paper offers a theoretical exploration of the possibility of utilizing aqueous solutions of three salts (lithium bromide, lithium chloride and calcium chloride), known mainly from absorption cooling, as working fluids for APCs. The cycles are compared with a typical steam Rankine cycle, a water‐ammonia APC, and (subcritical) ORCs with a range of working fluids explored. The analysis includes a parasitic load for heat rejection by a cooling tower or air‐cooled condenser. The absorption cycles exhibit better performance than all Rankine‐based cycles analysed in temperatures below 120°C. For the LiBr‐based APC, a detailed thermal design of the cycle is provided for 100°C water as a heat source and a sensitivity analysis is performed of the parameters controlling the main cycle. Mechanical design considerations should not pose a problem for small power units, especially in the case of expansion machines, which are often problematic in ORCs. The salt‐based APCs also carry environmental benefits, as the salts utilized in the working fluids are non‐toxic. Copyright © 2016 John Wiley & Sons, Ltd.
The aim of this paper is to introduce a novel method for the detection of coarse water droplets in a low pressure part of steam turbines. The photogrammetry method has been applied for the measurement of coarse droplets in the low-pressure part of a steam turbine. A new probe based on this measurement technique was developed and tested in the laboratory and in a steam turbine in the Poþerady power-plant. The probe was equipped with state-of-the-art instrumentation. The paper contains results from laboratory tests and the first preliminary measurements in a steam turbine. Possible applications of this method have been examined.
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