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A Pelton wheel operates from an effective head of He = 450 m and at a flow rate of 5.0 m³/s. The wheel radius is r2= 0.85 m and its rotational speed is 430 rpm. The water which leaves the penstock is divided into a few streams. The nozzle coefficient is cn = 0.98 for each of the nozzles. Impulse blades turn the flow into the direction ß3 =-62° and as a result of friction the relative velocity reduces by an amount which gives a velocity coefficient cy = 0.96. Find, (a) the efficiency of the turbine, (b) the power specific speed, (c) the jet number, d) the nozzle diameter e) the number of buckets in the wheel. Find, (a) the efficiency of the turbine (b) the power specific speed (c) the jet number

A Pelton wheel operates from an effective head of He = 450 m and at a flow rate of 5.0 m³/s. The wheel radius is r2= 0.85 m and its rotational speed is 430 rpm. The water which leaves the penstock is divided into a few streams. The nozzle coefficient is cn = 0.98 for each of the nozzles. Impulse blades turn the flow into the direction ß3 =-62° and as a result of friction the relative velocity reduces by an amount which gives a velocity coefficient cy = 0.96. Find, (a) the efficiency of the turbine, (b) the power specific speed, (c) the jet number, d) the nozzle diameter e) the number of buckets in the wheel. Find, (a) the efficiency of the turbine (b) the power specific speed (c) the jet number

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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A Pelton wheel operates from an effective head of He = 450 m and at a flow rate of 5.0 m³/s. The wheel radius is r2= 0.85 m and its rotational speed is 430 rpm. The water which leaves the penstock is divided into a few streams. The nozzle coefficient is cN = 0.98 for each of the nozzles. Impulse blades turn the flow into the direction ß3 =-62° and as a result of friction the relative velocity reduces by an amount which gives a velocity coefficient cv = 0.96. Find, (a) the efficiency of the turbine, (b) the power specific speed, (c) the jet number, d) the nozzle diameter e) the number of buckets in the wheel. Find, (a) the efficiency of the turbine (b) the power specific speed (c) the jet number (d) the nozzle diameter (e) the number of buckets in the Wheel First find the exit velocity from the nozzle and the blade speed; V2 = CN /2gHe U Туре Ssp | n% The relative velocity entering the Wheel; W2 = V2 – U Relative velocity at the exit; Pelton wheel Single jet Twin jet Three jet Four jet 0.02 - 0.18 88 – 90 0.09 – 0.26 89 – 92 W3 CW2 0.10 – 0.30 89 – 92 || 0.12 – 0.36 86 The tangential component of the relative velocity at the exit; Wu3 = W3sinß3 The tangential component of the absolute velocity at the exit; Vu3 = U + Wu3 Francis 0.39 – 0.65 90 – 92 Low-speed Medium-speed High-speed Extreme-speed 0.65 – 1.2 93 1.2 – 1.9 93 - 96 Specific work; 1.9 – 2.3 89 – 91 w = U (Vu2 – Vu3) Kaplan turbine Bulb turbine 1.55 – 5.17 87 – 94 (Remember V2=Vu2 for Pelton Wheel) The power; 3 - 8 W = pQw || The efficiency; W Specific speed and power specific speed; || (gH.)3/4 Determine the jet number from the table. The flow rate in each jet; Qj N The jet area,; The ratio of the wheel diameter to the jet diameter; Qj Aj : V2 D d Jet diameter; Finally the number of buckets; 4Aj D Z = 2d d + 15
Transcribed Image Text:A Pelton wheel operates from an effective head of He = 450 m and at a flow rate of 5.0 m³/s. The wheel radius is r2= 0.85 m and its rotational speed is 430 rpm. The water which leaves the penstock is divided into a few streams. The nozzle coefficient is cN = 0.98 for each of the nozzles. Impulse blades turn the flow into the direction ß3 =-62° and as a result of friction the relative velocity reduces by an amount which gives a velocity coefficient cv = 0.96. Find, (a) the efficiency of the turbine, (b) the power specific speed, (c) the jet number, d) the nozzle diameter e) the number of buckets in the wheel. Find, (a) the efficiency of the turbine (b) the power specific speed (c) the jet number (d) the nozzle diameter (e) the number of buckets in the Wheel First find the exit velocity from the nozzle and the blade speed; V2 = CN /2gHe U Туре Ssp | n% The relative velocity entering the Wheel; W2 = V2 – U Relative velocity at the exit; Pelton wheel Single jet Twin jet Three jet Four jet 0.02 - 0.18 88 – 90 0.09 – 0.26 89 – 92 W3 CW2 0.10 – 0.30 89 – 92 || 0.12 – 0.36 86 The tangential component of the relative velocity at the exit; Wu3 = W3sinß3 The tangential component of the absolute velocity at the exit; Vu3 = U + Wu3 Francis 0.39 – 0.65 90 – 92 Low-speed Medium-speed High-speed Extreme-speed 0.65 – 1.2 93 1.2 – 1.9 93 - 96 Specific work; 1.9 – 2.3 89 – 91 w = U (Vu2 – Vu3) Kaplan turbine Bulb turbine 1.55 – 5.17 87 – 94 (Remember V2=Vu2 for Pelton Wheel) The power; 3 - 8 W = pQw || The efficiency; W Specific speed and power specific speed; || (gH.)3/4 Determine the jet number from the table. The flow rate in each jet; Qj N The jet area,; The ratio of the wheel diameter to the jet diameter; Qj Aj : V2 D d Jet diameter; Finally the number of buckets; 4Aj D Z = 2d d + 15
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