Flow analysis of the turbine rotor tip seal on a highly rotary test rig

Workshop byl částečně podpořen projektem CZ.1.07/2.3.00/20.0139. Tento projekt je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky

Investigation of the tip-leakage losses in turbine axial stages

In turbomachinery, an influence of a tip-leakage flow on overall blade loss is crucial and its reduction is still worth striving for. In this paper a numerical analysis of the flow in tip seal of high-rotating gas turbine engine has been made. This analysis is a part of experimental research for testing the commercially used different tip seals solutions. Described test rig is predicted to be an universal tool for developing and examining different configurations of turbine blade tips. Presented numerical analysis is used to predict physical phenomena that may affect the rotor blade performance. In the numerical investigation the commercial Ansys CFX software was employed. The most important parameters were: mass flow rate at the inlet and outlet of the test bench, pressure and velocity distribution and the air temperature growth above the rotor. Also, an influence of test rig inlet and outlet geometry on flow uniformity was investigated. During the analysis the attention was focused also on minimizing the turbulence intensity in outlet area, that could cause significant difficulties in flow and stable work of the machine – generated eddies contributes to lower the mass flow rate

Experimental and numerical study on the performance of the smooth-land labyrinth seal

In turbomachinery the secondary flow system includes flow phenomena occurring outside the main channel, where the gaseous medium performs work on blades. Secondary air distribution constitutes a very complex and closely interrelated system that affects most of the gas turbine components. One of the most important examples of the secondary flow is leakage occurring in seals, e.g. at the rotor and stator tips, on the shaft or on the sides of the blade rim. Owing to its simplicity, low price, easy maintenance and high temperature capability, the labyrinth seal is a prime sealing solution that may be selected from numerous types of sealing structures applied in turbomachinery. For this reason, an experimental study of this particular structure has been carried out. The paper presents leakage performance of the smooth-land labyrinth seal

Labyrinth seals flow field evaluation with optical methods

This work aims to perform the detailed experimental investigation of the flow field in labyrinth seal specimen using optical methods: LDA (Laser Doppler Anemometry) and schlieren visualization. Preliminary tests were performed on a stationary (rotor model with labyrinth does not move), linear – where the curvature of the specimen is omitted – measuring stand supplied by a vacuum pump. The installation makes it possible to achieve critical pressure ratios, up to two. This investigation was also supported by CFD (Computational Fluid Dynamics) calculations performed using the Ansys CFX v.17 commercial code with a flow model based on the RANS equations. Prediction scheme simulated the experimental campaign parameters. In CFD study, different types of mesh resolution were tested, with variable volume discretization in the area of labyrinth fin tip. Presented study shows challenges as well as the possibilities of flow field visualization including three-dimensional vortexes and strong jets occurring downstream the fin tips. Some limitations of LDA method application were pointed out, especially in areas of rapid fluid expansion. Moreover paper presented that schlieren method is a very efficient way of giving the turbulence structures in linear labyrinth seal fins. In the end, experimental results were compared with CFD study, which reviled the best method for labyrinth seal structures flow field simulation. Comparison of experimental and computed results showed some agreement between those two approaches. Flow visualization also allowed to understand better the flow behavior in cavities, which is crucial for design tools development.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

The integration of renewable energy sources into electric power transmission systems

Renewable energy technologies such as photovoltaics, solar thermal power plants, and wind turbines are nonconventional, environmentally attractive sources of energy that can be considered for electric power generation. Many of the areas with abundant renewable energy resources (very sunny or windy areas) are far removed from major load centers. Although electrical power can be transmitted over long distances of many hundreds of miles through high-voltage transmission lines, power transmission systems often operate near their limits with little excess capacity for new generation sources. This study assesses the available capacity of transmission systems in designated abundant renewable energy resource regions and identifies the requirements for high-capacity plant integration in selected cases. In general, about 50 MW of power from renewable sources can be integrated into existing transmission systems to supply local loads without transmission upgrades beyond the construction of a substation to connect to the grid. Except in the Southwest, significant investment to strengthen transmission systems will be required to support the development of high-capacity renewable sources of 1000 MW or greater in areas remote from major load centers. Cost estimates for new transmission facilities to integrate and dispatch some of these high-capacity renewable sources ranged from several million dollars to approximately one billion dollars, with the latter figure an increase in total investment of 35%, assuming that the renewable source is the only user of the transmission facility

Lack of trust in maternal support is associated with negative interpretations of ambiguous maternal behavior

Attachment theory assumes that children who lack trust in maternal availability for support are more inclined to interpret maternal behavior in congruence with their expectation that mother will remain unavailable for support. To provide the first test of this assumption, early adolescents (9-13 years old) were asked to assess whether ambiguous interactions with mother should be interpreted in a positive or a negative way. In our sample (n = 322), results showed that early adolescents' lack of trust in their mother's availability for support was related to more negative interpretations of maternal behavior. The associations remained significant after controlling for depressive mood. The importance of these findings for our understanding of attachment theory, attachment stability, and clinical practice are discussed

State trust in middle childhood: an experimental manipulation of maternal support

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Revising working models across time: Relationship situations that enhance attachment security

We propose the Attachment Security Enhancement Model (ASEM) to suggest how romantic relationships can promote chronic attachment security. One part of the ASEM examines partner responses that protect relationships from the erosive effects of immediate insecurity, but such responses may not necessarily address underlying insecurities in a person’s mental models. Therefore, a second part of the ASEM examines relationship situations that foster more secure mental models. Both parts may work in tandem. We posit that attachment anxiety should decline most in situations that foster greater personal confidence and more secure mental models of the self. In contrast, attachment avoidance should decline most in situations that involve positive dependence and foster more secure models of close others. The ASEM integrates research and theory, suggests novel directions for future research, and has practical implications, all of which center on the idea that adult attachment orientations are an emergent property of close relationships