Browsing by Author "Szymański, Artur"

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    Evaluation of leakage through labyrinth seals with analytical models
    (Centre of Informatics, Tri-City Academic Supercomputer and networK, 2019-01-03) Szymański, Artur; Dykas, Sławomir
    Secondary flows in turbo machinery highly affect the overall efficiency and rotor stability. A prime example of such a phenomenon are leakage flows. Despite their complexity,they can often be estimated with simple semi-empirical formulae, solved with hand calculations.Such an approach is much more cost and time effective during the design process. The formulae consists of a carry-over coefficient and a discharge coefficient elements. To evaluate the leakage properly, an adequate model of the carry-over coefficient has to be developed. This paper presents show the flow conditions and the cavity geometry changes in a straight through labyrinth seal affect the amount of leakage. The effect of the number of teeth, the gap size, the Reynolds number and the pressure ratio are considered. The data to validate the results was obtained from an in-house experiment, where a vast number of cases was tested. Additionally, the study was supported by a two-dimensional steady-state CFD study. Eleven analytical models,Including both very simple as well as more sophisticated methods, were solved according to the experimental case and compared. Six different seal configurations were examined. They included straight through seals with two and three straight knives for various gap sizes.The comparison highlighted differences in the results for models – a certain group presented underestimated results. However, another group of models – presented an excellent agreement with the experimental data. Based on this study, a group of models representing the results within the 10% uncertainty band was selected.
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    Experimental and numerical study on the performance of the smooth-land labyrinth seal
    (Institute of Physics, 2016-12) Szymański, Artur; Dykas, S.; Wróblewski, W.; Majkut, M.; Strozik, M.
    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.
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    Experimental investigation of gas turbine compressor water injection for NOx emission reductions
    (Elsevier, 2019-04-03) Block novelo, David alejandro; Igie, Uyioghosa; Szymański, Artur
    The global rising demand for civil air travel shows good prospects for the industry, however, this growth is inevitably matched with higher levels of emissions and fuel consumption. In this study, demineralised water injection is presented as an alternative to reduce NOx emissions and enhance engine performance. The experimental study firstly presents the droplet size characterisation of a spray nozzle. This is done for varied injection pressure, water temperature and at varied axial and radial locations using an impaction pin nozzle. The single-shaft Artouste engine is used in conducting the compressor water injection test with water-to-air ratios of 0.5, 1 and 2%. The water droplet diameter, engine gas path and exhaust emissions are all monitored in real time. For the engine tests, droplets are measured at the spraying point and correlations are used to account for the droplet size at the inlet of the compressor due to measurement difficulties in this region. The test showed a reduction in compressor discharge temperature by up to 34 K and a NOx decrease by 25%. Nevertheless, the higher reductions in NOx at higher water-to-air ratios are attributed to a predominant cooling in the combustor because of unevaporated water in the compressor. At 0.5% water-to-air ratio, the drop in NOx is mainly due to compressor cooling and signified by the only case in which the fuel-to-air ratio reduces. The study presents evidence of the combined effects of compressor and combustor water ingestion. The CO is seen to increase significantly and associated with reduced combustor efficiency.
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    Impact of compressed air energy storage demands on gas turbine performance
    (Sage, 2020-02-16) Igie, Uyioghosa; Abbondanza, Marco; Szymański, Artur
    Industrial gas turbines are now required to operate more flexibly as a result of incentives and priorities given to renewable forms of energy. This study considers the extraction of compressed air from the gas turbine; it is implemented to store heat energy at periods of a surplus power supply and the reinjection at peak demand. Using an in-house engine performance simulation code, extractions and injections are investigated for a range of flows and for varied rear stage bleeding locations. Inter-stage bleeding is seen to unload the stage of extraction towards choke, while loading the subsequent stages, pushing them towards stall. Extracting after the last stage is shown to be appropriate for a wider range of flows: up to 15% of the compressor inlet flow. Injecting in this location at high flows pushes the closest stage towards stall. The same effect is observed in all the stages but to a lesser magnitude. Up to 17.5% injection seems allowable before compressor stalls; however, a more conservative estimate is expected with higher fidelity models. The study also shows an increase in performance with a rise in flow injection. Varying the design stage pressure ratio distribution, brought about an improvement in the stall margin utilized, only for high extraction.
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    Investigation of the tip-leakage losses in turbine axial stages
    (Institute of Physics, 2014-12) Szymański, Artur; Dykas, S.; Wróblewski, W.; Rulik, S.
    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.