Hydro Turbine in a Venturi Tube

U radu su prikazani rezultati istraživanja hidroturbine u Venturijevoj cijevi za zadani broj okretaja i zadanom brzinom vode na ulazu u cijev. Rezultati su dobiveni komercijalnim softverom za numeričku dinamiku fluida. Ispitivanje je obuhvatilo usporedbu snage koju daju jedna i dvije suprotno smjerno rotirajuće hidroturbine u Venturijevoj cijevi. Numeričke simulacije za dvije turbine koje se okreću u suprotnim smjerovima s jednakim kutnim brzinama pokazale su da se javlja znatan pad snage na prednjoj turbini, dok je ukupna snaga nešto veća nego za jednu turbinu.This paper presents results of a research hydro turbine in a Venturi tube for given revolutions per minute and velocity of water at the entry of the tube. The results were obtained with commercial software for numerical fluid dynamics. The research was included comparison of power obtained with one and two contra-rotating hydro turbine in a Venturi tube. The numerical simulations, for two turbines rotating in opposite directions with equal angular velocities, showed that a considerable power drop occurred, whereas the total power is somewhat larger than for the one turbine

Numerical simulation of multiphase flow around suction plates of ventilation mill in the function of extending its remaining working life

Ovaj rad prestavlja mogućnost korišćenja rezltata numeričkih simulacija, za smanjenje habanja radnih delova ventilacionog mlina za mlevenje uglja u termoelektrani Kostolac B. Mogućnost revitalizacije usisnih ploča ventilacionog mlina je zasnovan na 3D numeričkoj simulaciji multifaznog strujanja u ventilacionom mlinu. Čvrste čestice smeše ugalj, mineralne materije, pesak tokom procesa mlevenja izazivaju veliko habanje usisnih ploča. Primenom softverskog paketa ANSYS FLUENT 12, dobiće se detaljniji prikaz multifaznog strujanja i brzine mešavine koja omogućuje da se na osnovu intenziteta i smera brzine, preciznije odrede kritične zone u kojima će se pojaviti oštećenja kod usisnih ploča ventilacionog mlina. Korišćen je Euler-Euler model mešavine. Rezultati dobijeni pomoću numeričke simulacije koristiće se za izbor optimalne tehnologije revitalizacije usisnih ploča ventilacionog mlina. Primenom ovog pristupa rešavanja problema smanjio bi se broj mogućih interventnih popravki i produžio bi se period između neophodnih kompletnih remonta postrojenja, čime bi se ostvarili značajni ekonomski efekti i ujedno povećala energetska efikasnost termoenergetskih agregata.This paper presents results of the analyses obtained by numerical simulation for the possibilities of increasing the wear resistance of the ventilation mill working parts for coal grinding in the Kostolac B power plant. The possibilities for modification are based on 3D numerical simulation of multiphase flow of ventilation mill. Mineral materials during the process of milling in the ventilation mill cause strong wear of the suction plates. The multiphase flow simulations are performed in order to obtain the mineral materials paths and velocity vectors. The mixture model of the Euler-Euler approach is used. The results obtained in the numerical simulation serve for the selection of an optimal redesign of the suction plates. The application of this approach can reduce the number of possible repairs and extends the period between them, resulting in significant economic effects

CFD Analysis of the Influence of Centrifugal Separator Geometry Modification on the Pulverized Coal Distribution at the Burners

This paper presents the results of 3D numerical flow simulation in the ventilation mill (VM) and air mixture channel (AMC) of Kostolac B power plant, where a centrifugal separator with adjustable blade angle is used. Numerical simulations of multiphase flow were performed using the Euler-Euler and the Euler-Lagrange approach of the ANSYS FLUENT software package. The geometry of the numerical model was almost identical to the VM and AMC of Kostolac B, except for the smallest details. An unstructured tetrahedral grid, consisted of almost three million cells, was generated. The main contribution of this paper is the original analysis of the influence of centrifugal separator (CFS) geometry modification on the coal powder distribution at the horizontal burners. The modification of the blade angle, blade shape, and vertical position of the separator and its effect on the coal powder distribution at the burners were analyzed and are published for the first time. Results of the numerical simulations were compared with the measurements and can be used in modifying the separator geometry and position to obtain optimal distribution of the pulverized coal at the burners. Application of these results, obtained by numerical methods, ensures significant savings in time and money, in the process of finding the optimal geometry of CFS

CFD Analysis of the Influence of Centrifugal Separator Geometry Modification on the Pulverized Coal Distribution at the Burners

This paper presents the results of 3D numerical flow simulation in the ventilation mill (VM) and air mixture channel (AMC) of Kostolac B power plant, where a centrifugal separator with adjustable blade angle is used. Numerical simulations of multiphase flow were performed using the Euler-Euler and the Euler-Lagrange approach of the ANSYS FLUENT software package. The geometry of the numerical model was almost identical to the VM and AMC of Kostolac B, except for the smallest details. An unstructured tetrahedral grid, consisted of almost three million cells, was generated. The main contribution of this paper is the original analysis of the influence of centrifugal separator (CFS) geometry modification on the coal powder distribution at the horizontal burners. The modification of the blade angle, blade shape, and vertical position of the separator and its effect on the coal powder distribution at the burners were analyzed and are published for the first time. Results of the numerical simulations were compared with the measurements and can be used in modifying the separator geometry and position to obtain optimal distribution of the pulverized coal at the burners. Application of these results, obtained by numerical methods, ensures significant savings in time and money, in the process of finding the optimal geometry of CFS

Possibility of Reducing the Overpressure of Shock Wave of Powder Gases around the Mortar

This paper resulted from the research of the overpressure of the shock wave of the powder gases, which occurs during firing of the mortar. Work encompasses modeling and computation of the overpressure field. Increasing overpressure around the mortar is analyzed in the case of using the largest powder charges. In order to reduce the overpressure a corresponding technical solution has been proposed. The solution in the form of divergent nozzle has been proposed and it is placed at the barrel muzzle. The paper also analyzes the impact of this solution to reduce the overpressure intensity at the crew position.Computation results of the overpressure of the powder gases, which were obtained by the realization of numerical calculation, based on the application of the finite volume method, were confirmed by the experimental results, achieved in the firing experiments

Numerical simulation of multiphase flow around suction plates of ventilation mill in the function of extending its remaining working life

Ovaj rad prestavlja mogućnost korišćenja rezltata numeričkih simulacija, za smanjenje habanja radnih delova ventilacionog mlina za mlevenje uglja u termoelektrani Kostolac B. Mogućnost revitalizacije usisnih ploča ventilacionog mlina je zasnovan na 3D numeričkoj simulaciji multifaznog strujanja u ventilacionom mlinu. Čvrste čestice smeše ugalj, mineralne materije, pesak tokom procesa mlevenja izazivaju veliko habanje usisnih ploča. Primenom softverskog paketa ANSYS FLUENT 12, dobiće se detaljniji prikaz multifaznog strujanja i brzine mešavine koja omogućuje da se na osnovu intenziteta i smera brzine, preciznije odrede kritične zone u kojima će se pojaviti oštećenja kod usisnih ploča ventilacionog mlina. Korišćen je Euler-Euler model mešavine. Rezultati dobijeni pomoću numeričke simulacije koristiće se za izbor optimalne tehnologije revitalizacije usisnih ploča ventilacionog mlina. Primenom ovog pristupa rešavanja problema smanjio bi se broj mogućih interventnih popravki i produžio bi se period između neophodnih kompletnih remonta postrojenja, čime bi se ostvarili značajni ekonomski efekti i ujedno povećala energetska efikasnost termoenergetskih agregata.This paper presents results of the analyses obtained by numerical simulation for the possibilities of increasing the wear resistance of the ventilation mill working parts for coal grinding in the Kostolac B power plant. The possibilities for modification are based on 3D numerical simulation of multiphase flow of ventilation mill. Mineral materials during the process of milling in the ventilation mill cause strong wear of the suction plates. The multiphase flow simulations are performed in order to obtain the mineral materials paths and velocity vectors. The mixture model of the Euler-Euler approach is used. The results obtained in the numerical simulation serve for the selection of an optimal redesign of the suction plates. The application of this approach can reduce the number of possible repairs and extends the period between them, resulting in significant economic effects

Experimental and numerical study of super-critical flow around the rough sphere

Rad predstavlja eksperimentalno i numeričko istraživanje modela sfere sa ciljem predviđanja ponašanja strujanja u prisustvu hrapavosti površina. Rezultati ukazuju na probleme i predlažu rešenje za inžinjersku primenu. Sličnost između strujnih slika dobijenih numeričkim putem i u aerotunelu je postignuta kombinovanim uvođenjem turbulencije u numeričkoj slobodnoj struji hrapavosti površine, zbog ograničavajućih zahteva turbulentnih modela.This paper presents the experimental and numerical research on the sphere model with the goal of prediction of a flow behaviour in a presence of the surface roughness. Results indicate the problems and suggest the solution for engineering practice. The similarity of the numerical and wind tunnel flows was reached by an application of a combination of the intentionally introduced turbulence intensity in a numerical flow as well the artificial roughness of the model, for a reason of restricted requirements of the turbulence modelling

Experimental and numerical study of super-critical flow around the rough sphere

Rad predstavlja eksperimentalno i numeričko istraživanje modela sfere sa ciljem predviđanja ponašanja strujanja u prisustvu hrapavosti površina. Rezultati ukazuju na probleme i predlažu rešenje za inžinjersku primenu. Sličnost između strujnih slika dobijenih numeričkim putem i u aerotunelu je postignuta kombinovanim uvođenjem turbulencije u numeričkoj slobodnoj struji hrapavosti površine, zbog ograničavajućih zahteva turbulentnih modela.This paper presents the experimental and numerical research on the sphere model with the goal of prediction of a flow behaviour in a presence of the surface roughness. Results indicate the problems and suggest the solution for engineering practice. The similarity of the numerical and wind tunnel flows was reached by an application of a combination of the intentionally introduced turbulence intensity in a numerical flow as well the artificial roughness of the model, for a reason of restricted requirements of the turbulence modelling

Numeričke simulacije širenja štetnih gasova i čestica emitovanih iz Železare u Smederevu

This paper presents the results obtained by numerical simulation, of air pollution dispersion from the stacks of steel plant in the direction of Smederevo fortress. Trajectories and concentrations of pollutants (particulate matters, CO and NO2) were determined by commercial software ANSYS FLUENT. The relief of the terrain was included in the geometry of the numerical domain (11400x3600x100 m). An unstructured mesh composed of more than three million cells was generated. Southeast wind speed was 2.9 m/s blowing in the direction parallel to the longest side of the domain. Atmospheric conditions correspond to conversion, i.e. increase in temperature with height. The sources of pollution included in the simulation are central agglomeration stack, blast fumaces stack and central stack of steel-making. Obtained results represent the first step in a complex, multidisciplinary research of the industrial zones impact on cultural heritage objects.U radu su prikazani rezultati širenja štetnih materija u vazduhu, emitovanih iz dimnjaka Železare u pravcu Smederevske tvrđave, dobijeni numeričkom simulacijom. Putanje i koncentracija polutanata (čestica, CO i NO2) su simulirane komercijalnim softverskim paketom ANSYS FLUENT. Reljef terena je uključen u geometriju numeričkog domena, čije su dimenzije 11400x3600x100 m. Generisana je nestruktuisana mreža sa više od tri miliona ćelija. Numerička simulacija je vršena za jugoistočni vetar (paralelan dužoj stranici domena) brzine 2.9 m/s. Atmosferski uslovi odgovaraju slučaju konverzije, temperatura raste sa visinom. Izvori zagađenja su centralni dimnjak aglomeracije, dimnjak visoke peći i centralni dimnjak čeličane. Dobijeni rezultati su samo prvi korak kompleksnog, multidisciplinarnog istraživanja uticaja industrijskih zona na objekte kulturne baštine

Wear resistance improvement of thermal plant fan mill impact plates based on numerical flow simulation

Numerical simulation of 3D multiphase flow is performed to determine the velocity field in the fan mill. The mixture model of the Euler-Euler approach is used. Recirculating gas is a primary phase that carries granular phases including the coal powder and sand. The latter causes heavy wear of mill impact plates. The optimal form of hardfacing geometry and technology has an impact both on velocity magnitude and direction of flow in such a way as to reduce plate wear. This paper presents results of surface modification (based on numerical simulation), implemented on impact plates of the fan mill in the Kostolac B power plant in Serbia. Fishbone hardfacing is made in order to increase the lifetime of impact plates and extend the period between overhauls of fan mills. The experimental tests of fishbone surfacing plates, in exploitation conditions, show that the applied modification, hardfacing technologies and coating materials, give expected results. The application of this hardfacing in the form of a fishbone is simpler, faster and more economical compared to complete overlaying and honeycomb impact plate surfacing. The relative weight loss of base plate after an 1440-hour period of exploitation is 8%, while the weight losses for the hard-faced plate is below 7%