HYDRAULIC PERFORMANCE OF CONICAL DIFFUSERS

Abstract

This thesis presents a study of the l ydrziuLio portoxnanoo of ccrnio . diffusors, hawing an area ratio of I t 4 with total divor once an lea equal to 320 o 1800. Four types of boundary geometryy for the diffuoin section$ nrnolyt a curve obtained by potent iloc theory for axieyxwnotrie oaue o, Gibson' c ourvo, a st rai a►t cone and € n abrupt ozaneion were adopted and their re Lat ivo perfor-mance is stud d for three different Reynolds Number of the moan flow at entrance. The Reynolds number is chimed from 268,000 to 92O QQ0 , to know its • effect on each of the four bounthry eeometrioo. .Turbulent boundary der was obtained at the ontr snco for aU models by puttint proper roughness st. imulat ore. Growth of turbulent boundary iffier and location of oepc at ion, point on the cur red wnU are carefully studied by taking moan velooity and mean pressure data. Eziatiz literature on the Clor7 phenomena in diffuser soot ions is briefly reviewed and cou mentad, Some of the ezloting criteria useful for prodoting the po#it of separation of the turbulent boundary layer have been compared with the present observations. The diffuser section c isohar ee into the oquare dust of a non-oircuiat ing wind tunnel. Tine-average values of total presoure and ambient scat to pro3oure ware measured separately by means of iypodoaic tubes at suitable stat ions along the length within the dLCfusor soot ion and in the dust downstream of the diffuser, L1eaeureaonta within in the boundary Layer were taken upt o separationpoint located apriori wish was approximated by visualising the Slow direct ion by wei t«i loco threads* iiowever, velocity d .ut ribut Anna- along the out ire orross-seat ion of flow were t .on at tae inst seat ion, four other soot for within tae diffuser and thaw more suet ions at suit able iat o .s in the duet, Dimensionless velocity profile ► within the boundary layers as well au across the d,iemater and wail pressures ace plotted. rowth of momentum tIUoineea and snaps para-meter along the arc length of diffuser bound ry were plotted for two diffusers only i.e. e.. potent jal4low model. and Gibso .'e model. The var at ion of Iot to every correct ion factor with distance is also calculated, The *oe ficiont of energy loos is plotted as a funotton of the Bc maids amber for all The growth of momentum tbic tneoeo shape parameter and head loss as measured here are compared with oarlio results by 1). Roos, Sts at ford# 4.. Gibson and U.0. Cbturvedi. The oeement of the development of tuxb ,lent boundary layer is poor# while for shape parameter and head loss, it is quite satisfactory. The results Indicate that thorn is no apps- stable change in the value of coefficient of energy lose for the potent ial- flow and t ibsor2. geometries whereas it is slightly higher in the case of of ai; nt diffuser and maxi* mum for the abrupt a rpansion, The doeffieierit of head loss is found to decrease as the Reynolde number uses and this trawl is consist ont for all the four models* The .ass-anetry in the flew is obaerved for all the rune and visual. observations indicated flow alternation fro one waLl. to the o posite wall. It appears that this peculiar phenomenon is inherent with all sops ted £lows, no matter thether they are enolesed by boundaries or enlopig the boundaries.