Sensitivity analysis for power plant pumping systems in breakdown

The small number of available complete modern pump characteristics makes the safety analysis of nuclear and conventional power plants based on the characteristics made over half a century ago of specific speeds nq = 24.6,147.1 and 261.4. The aim of the paper is to check sensitivity of the power plant system response for different complete pump characteristics–modern and available from older tests for nq = 24.6, 147.1 and 261.4. It has been shown that Suter’s characteristics for modern pumps give a different response to the pumping system of a power plant in break down than those used so far

The modeling of centrifugal pump transients

Centrifugal pumps are part of larger hydraulic systems. These hydraulic machines can work not only in the pumping mode but in a number of other modes whose job description is possible using complete characteristics. Some of these modes, such as the turbine mode and the reversed turbine mode, may have practical significance. Knowledge of the transition from one steady state to another state allows to estimate instantaneous values such as, e.g., flow current and torque, which may be even a few times higher than nominal. The principal issues in these transients are amplitudes of parameters of these pumps and the time constants associated with the characteristics of the system

Influence of radial flow impeller balance holes on the net positive suction head for rotodynamic pumps

The influence of balance holes of rotodynamic pumps on the net positive suction head is not fully clear. The lack of available information on the subject leads to the situations when deterioration in suction properties of the pump due to the presence of balance holes is recognized during pump test phase. Usually some holes are arbitrarily plugged. The paper analyses the influence of balance holes on net positive suction head characteristics. The measurement data are presented

Investigations of turbulent flow through axial thrust balance holes in rotodynamic pumps

The results of numerical investigations of flow through axial thrust balance holes in impeller of low specific speed pump were presented. The results were compared with available empirical investigations. It is a lack of numerical analyses in foregoing literature on flow through rotating holes. The issue is important for designing rotodynamic pumps. There are difficulties in solving the problem of precisely computing the flow in balance holes analytically

Badania doświadczalne i obliczenia numeryczne sił promieniowych działających na wirnik pompy odśrodkowej

The paper presents the results of measurements and predictions of radial thrust in centrifugal pump with specific speed ns = 26. In the pump tested, a volute with rectangular cross-section was used. The tests were carried out for several rotational speeds, including speeds above and below the nominal one. Commercial code ANSYS Fluent was used for the calculations. Apart from the predictions of the radial force, the calculations of axial thrust were also conducted, and correlation between thrust and the radial force was found. In the range of the measured rotational speeds, similarity of radial forces was checked.W artykule przedstawiono wyniki pomiarów i obliczeń naporu osiowego w pompie odśrodkowej o wyróżniku szybkobieżności ns = 26. W badanej pompie została zastosowana spirala zbiorcza o przekroju prostokątnym. Badania wykonano dla kilku prędkości obrotowych, w tym powyżej i poniżej nominalnej. W obliczeniach wykorzystano kod ANSYS Fluent. Oprócz obliczeń siły promieniowej, zostały przeprowadzone obliczenia naporu osiowego oraz stwierdzono obecność korelacji między obiema siłami. W zakresie mierzonych prędkości obrotowych zbadane zostało również podobieństwo sił promieniowych

Importance of nest boxes for breeding birds in forest areas - the Wielkopolski National Park case study

The study embraced 159 nest boxes placed in three different study plots in the Wielkopolski National Park in western Poland. In the first season, 64% of nest boxes were occupied by four species: great tit Parus major, blue tit Cyanistes caeruleus, Eurasian nuthatch Sitta europaea and European pied flycatcher Ficedula hypoleuca. The dominant species were great and blue tits. Over 80% of broods of great tits and blue tits were reared successfully. Birds preferred nest boxes located in plots with domination of oaks and Scots pine and with rich underbrush. Woodpeckers damaged entrances of 70% of the nest boxes, but did not cause any brood losses. In 13% of the boxes nests of hornets, bumblebees and wasps were found. Bumblebees chose boxes with a bird nest material, whereas wasps and hornets avoided sites occupied by the birds. In general, the insects had a small impact on breeding success of birds and caused failure of only 3% of all broods. Obtained results show that nest boxes in forests may increase density of the most common cavity nesters and secure their high breeding success