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Browse complete papersA Pelton wheel is designed to develop 6000 kW under a net head of 300 m while running at 550 rpm. The overall efficiency is 85%, and the ratio of jet diameter to wheel diameter is \( \frac{1}{10} \). If the velocity coefficient Kv=0.98 and speed ratio Ku = 0.46, the number of jets required is:
1
2
3
4
Correct answer
1
The draft tube of a Kaplan turbine has an inlet diameter of 2.6 m, and its inlet is 2.9 m above the tail race. The turbine develops 2100 metric horsepower under a net head of 6.5 m. A vacuum gauge fitted at the inlet of the draft tube shows a negative head of 4 m. The turbine efficiency is 86%. Atmospheric pressure = 10.3 m of water.
Determine the draft tube efficiency.
56%
66%
76%
86%
Correct answer
56%
A Francis turbine is supplied through a 6 m diameter penstock and has the following data: Output = 63, 500 kW, Discharge = \( 117 m^3/s \), Speed = 150 rpm, Hydraulic efficiency = 92%, Static pressure head at penstock just before runner = 57.4 m, velocity in tail race = 2.4 m/s, The pressure tap is 3 m above tail race. The net head acting on the turbine and the overall efficiency are approximately:
H = 55 m, \( \eta_0 = 0.85 \)
H = 60.98 m, \( \eta_0 = 0.907 \)
H = 65 m, \( \eta_0 = 0.92 \)
H = 58 m, \( \eta_0 = 0.88 \)
Correct answer
H = 55 m, \( \eta_0 = 0.85 \)
Steam enters a nozzle at a pressure of 10 bar with a specific volume of \( 0.25 m^3/kg \). The index of expansion is n = 1.3, and the throat area is \( 0.01 m^2 \). Under isentropic conditions, determine the maximum possible steam mass flow rate.
13.5 kg/s
24.4 kg/s
4.6 kg/s
55.9 kg/s
Correct answer
13.5 kg/s
A 13, 240 kW Francis turbine runs at 150 rpm under a net head of 27 m. The effective atmospheric pressure head is 10.6 m of water. The draft tube must extend at least 0.77 m below the tail race. The maximum permissible height of a straight conical draft tube is approximately:
1, 45 m
2.01 m
2.22 m
2.82 m
Correct answer
1, 45 m
Steam expands isentropically through a nozzle with an adiabatic heat drop of 100 kJ/kg. Calculate the exit velocity of steam (assuming negligible inlet velocity).
320 m/s
447 m/s
520 m/s
400 m/s
Correct answer
320 m/s
A cylinder of diameter 1.2 m rotates in the air, moving at 128 km/h. A lift of 5886 N per metre length is developed on the cylinder. Assuming ideal fluid theory, \( \rho = 1.236 kg/m^3 \). Find the rotational speed of the cylinder in rpm and the location of the stagnation points.
N = 566 rpm; \( \theta = -30^\circ \) and \( 210^\circ \)
N = 500 rpm; \( \theta = -45^\circ \) and \( 225^\circ \)
N = 600 rpm; θ = -25∘ and 205∘
N = 550 rpm; θ = -35∘ and 215∘
Correct answer
N = 566 rpm; \( \theta = -30^\circ \) and \( 210^\circ \)
A kite weighing 12.26 N has an effective area of \( 0.9 m^2 \). The tension in the string is 32.37 N, and the string makes an angle of \( 45^\circ \) with the horizontal. The wind speed is 32 km/h. If the density of air is \( 1.203 kg/m^3 \), find the coefficients of drag CD and lift CL.
CD = 0.32, CL=0.58
CD = 0.45, CL = 0.71
CD = 0.535, CL = 0.822
CD = 0.72, CL = 0.41
Correct answer
CD = 0.32, CL=0.58
In an impulse steam turbine, Adiabatic power, Rim power, and Shaft power are defined as \( \dot{m}_s(h_1 - h_2) \), \( \dot{m}_s(h_1 - h_4) \), and \( \dot{m}_s(h_1 - h_5) \),respectively. The enthalpy \( h_2 \) accounts for losses in the nozzle, \( h_4 \) includes the effects of blade friction and windage losses, and \( h_5 \) further incorporates mechanical losses in power transmission. Based on these definitions and the nature of losses occurring at different stages of energy conversion in the turbine, which of the following statements correctly represents the relationship among Adiabatic power, Rim power, and Shaft power?
Rim power is greater than adiabatic power due to reheating in the blades
Shaft power is always equal to rim power
Net efficiency is independent of mechanical losses
Internal efficiency is based on the ratio of rim power to adiabatic power
Correct answer
Rim power is greater than adiabatic power due to reheating in the blades
A centrifugal pump has an impeller of diameter 0.29 m running at 960 r.p.m. with an outlet vane angle of 28°. The velocity of flow is 2 m/s. The static suction lift is 2.8 m. Head losses are: suction pipe = 0.61 m, impeller = 0.49 m, volute casing = 0.88 m.
Find the pressure head readings at:
(i) Inlet to the pump
(ii) Impeller outlet
Inlet = -2.8 m, Impeller outlet = 7 m
Inlet = -3.6 m, Impeller outlet = 12 m
Inlet = -4.2 m, Impeller outlet = 18 m
Inlet = -3.1 m, Impeller outlet = 24 m
Correct answer
Inlet = -2.8 m, Impeller outlet = 7 m