Radial hydraulic machinery four-quadrant performance curves dependent on specific speed and applied in transient calculations

The paper presents research analysis of possible analytical relationships that could exist in pointwise data for four-quadrant performance curves of one radial pump and seven pump-turbines for which the authors collected the basic data and performed the calculation. All the performance curves are for different specific speeds. Additionally, the examples of transformation calculation from the four-quadrant curves into Suter form curves shown in [1] - Thorley (1996) and [2] - Stepanoff (1959) have been presented. A numerical model has been developed for the calculation of transient processes in hydropower plants with installed pumps and pump-turbines. As an input data, the analytical relationships found in the previous research analysis have been used, as well as the pointwise curves for various specific speeds. The multi comparison of the results has been made and comprehensive conclusions given

Radial hydraulic machinery four-quadrant performance curves dependent on specific speed and applied in transient calculations

The paper presents research analysis of possible analytical relationships that could exist in pointwise data for four-quadrant performance curves of one radial pump and seven pump-turbines for which the authors collected the basic data and performed the calculation. All the performance curves are for different specific speeds. Additionally, the examples of transformation calculation from the four-quadrant curves into Suter form curves shown in [1] - Thorley (1996) and [2] - Stepanoff (1959) have been presented. A numerical model has been developed for the calculation of transient processes in hydropower plants with installed pumps and pump-turbines. As an input data, the analytical relationships found in the previous research analysis have been used, as well as the pointwise curves for various specific speeds. The multi comparison of the results has been made and comprehensive conclusions given

Solving the problem of general capacitor placement in radial distribution systems with laterals using simulated annealing

'Simulacija kaljenja' je prvi put primenjena za rešavanje problema kompenzacije reaktivne snage od strane grupe inženjera sa Kornel Univerziteta, Itaka, Nju Jork 1990-ih godina. To je metoda koja traga za globalnim optimumom funkcije cilja a ne zaglavljuje kod lokalnih optimuma čiji broj raste sa povećavanjem dimenzije problema. Originalne metode rešavanja problema kroz razvijene programe su prikazane. Bolja konvergencija se postiže inicializacijom algoritma sa rigoroznijim vrednostima parametara i to još uvek za prihvatljivo računarsko (CPU) vreme.Simulated annealing was introduced as the algorithm for solving general capacitor placement problem by a group of engineers from Cornell University Ithaca, New York in 1990s. It is the method which searches for a global optimum of the objective function rather than being stuck to the local optima whose number grows as problem dimension increases. In the developed programs, original methods for solving the problem are introduced. Optimum is reached by initializing an algorithm with more rigorous parameters and for reasonable amount of CPU time

Solving the problem of general capacitor placement in radial distribution systems with laterals using simulated annealing

'Simulacija kaljenja' je prvi put primenjena za rešavanje problema kompenzacije reaktivne snage od strane grupe inženjera sa Kornel Univerziteta, Itaka, Nju Jork 1990-ih godina. To je metoda koja traga za globalnim optimumom funkcije cilja a ne zaglavljuje kod lokalnih optimuma čiji broj raste sa povećavanjem dimenzije problema. Originalne metode rešavanja problema kroz razvijene programe su prikazane. Bolja konvergencija se postiže inicializacijom algoritma sa rigoroznijim vrednostima parametara i to još uvek za prihvatljivo računarsko (CPU) vreme.Simulated annealing was introduced as the algorithm for solving general capacitor placement problem by a group of engineers from Cornell University Ithaca, New York in 1990s. It is the method which searches for a global optimum of the objective function rather than being stuck to the local optima whose number grows as problem dimension increases. In the developed programs, original methods for solving the problem are introduced. Optimum is reached by initializing an algorithm with more rigorous parameters and for reasonable amount of CPU time

Investigation of a submerged cavitating jet behavior, Part two: Influences of operating conditions, geometrical parameters and arrangements of detection system

Na osnovu rezultata vizuelizacije kavitacionog vodenog mlaza dobijenih digitalnom kamerom, istraživani su uticaji parametara kao što su: pritisak ubrizgavanja, prečnik i geometrija mlaznice, način postavljanja mlaznice (konvergentan ili divergentan), kavitacijskog broja i izlazne brzine mlaza. Dodatno je proučavan efekat postavljanja sistema za vizuelizaciju. Pokazan je jak uticaj svih parametara na izgled mlaza i njegove karakteritike.In visualization results of highly-submerged cavitating water jet obtained by a digital camera, the influences of parameters such as: injection pressure nozzle diameter and geometry, nozzle mounting (convergent or divergent) cavitation number and exit jet velocity, were investigated. In addition, the position of visualization system was studied. All the parameters have been found to be of strong influence on the jet appearance and performance

Study and analysis of the cavitating and non-cavitating jets part two parameters controlling the jet action and a new formula for cavitation number calculation

This part of the paper presents the relation between the working conditions, nozzle geometry, nozzle diameter, and jet behavior. Experimental work has been made by impinging the submerged jets on the copper specimen as a target for a period of time. The mass loss and erosion rate at various conditions were measured, calculated and analyzed. For the visualization, a high-speed camera was used and the obtained data were processed to measure parameters which are used to characterize the clouds. Correlations among the jet dynamic power, the cavity length, erosion rate, and the pertinent experimental parameters are apparent. In addition, formulas are proposed to conveniently compare the efficiency of jetting systems based on working conditions. Based on the mathematical analyses of the obtained results a new form for cavitation number calculation is proposed

Investigation of a submerged cavitating jet behavior, Part one: The phenomenon, detection technique and sono-luminesеnce

U cilju istraživanja i razumevanja strukture mlaza i ponašanja kavitacionog oblaka u vremenu i prostoru, izvršena je vizuelizacija duboko potopljenog kavitacionog vodenog mlaza korišćenjem kamere 4-Quik-05. Ovo je zahtevalo obaveznu tehniku sinhronizacije i različite tipove objektiva. Uticaj parametara kao što su: pritisak ubrizgavanja, nizvodni pritisak i kavitacijski broj, i njihov značaj je eksperimentalno dokazan. Zapisi sonarno-luminescentnog fenomena su potvrdili da mehurovi nestaju dužinom čitave putanje mlaza. Takođe, istraživan je i efekat uticaja temperature na zvučnu-luminescenciju.In order to study and understand the jet structure and the behavior of cloud cavitation within time and space, visualization of highly submerged cavitating water jet has been done using 4-Quik-05 camera. This included obligatory synchronization technique and different types of lens-objectives. The influencing parameters, such as: injection pressure, downstream pressure and cavitation number were experimentally proven to be very significant. The recordings of sono-luminescence phenomenon proved the bubble collapse everywhere along the jet. In addition, the effect of temperature on sono-luminescence was a point of investigation

Study and analysis of the cavitating and non-cavitating jets part two parameters controlling the jet action and a new formula for cavitation number calculation

This part of the paper presents the relation between the working conditions, nozzle geometry, nozzle diameter, and jet behavior. Experimental work has been made by impinging the submerged jets on the copper specimen as a target for a period of time. The mass loss and erosion rate at various conditions were measured, calculated and analyzed. For the visualization, a high-speed camera was used and the obtained data were processed to measure parameters which are used to characterize the clouds. Correlations among the jet dynamic power, the cavity length, erosion rate, and the pertinent experimental parameters are apparent. In addition, formulas are proposed to conveniently compare the efficiency of jetting systems based on working conditions. Based on the mathematical analyses of the obtained results a new form for cavitation number calculation is proposed

Study and analysis of the cavitating and non-cavitating jets part one parameters controlling force, power, and the jet behavior

This paper presents the dependency of the jet power and the cavitation intensity on the working conditions of the cavitating and non-cavitating jet flow. This dependency is indicated by the cavitation erosion process and flow structure. The effects of working conditions on the cavitation erosion were experimentally investigated. The flow visualization was done using a high-speed photography recording system. The analysis shows that the erosion rate calculation and the visualization of the jet structure can be used as tools to estimate the jet strength, the jet actions, the jet power, and the performance of the jetting system

Investigation of a submerged cavitating jet behavior, Part two: Influences of operating conditions, geometrical parameters and arrangements of detection system

Na osnovu rezultata vizuelizacije kavitacionog vodenog mlaza dobijenih digitalnom kamerom, istraživani su uticaji parametara kao što su: pritisak ubrizgavanja, prečnik i geometrija mlaznice, način postavljanja mlaznice (konvergentan ili divergentan), kavitacijskog broja i izlazne brzine mlaza. Dodatno je proučavan efekat postavljanja sistema za vizuelizaciju. Pokazan je jak uticaj svih parametara na izgled mlaza i njegove karakteritike.In visualization results of highly-submerged cavitating water jet obtained by a digital camera, the influences of parameters such as: injection pressure nozzle diameter and geometry, nozzle mounting (convergent or divergent) cavitation number and exit jet velocity, were investigated. In addition, the position of visualization system was studied. All the parameters have been found to be of strong influence on the jet appearance and performance