Solved Examples based on outward flow reaction turbine

SOLVED EXAMPLES BASED ON OUTWARD FLOW REACTION TURBINE

Example - 31

An outward flow reaction turbine has internal and external diameter of the runner as 0.6 m and 1.2m respectively. The guide blade angle is 15o and velocity of flow through the runner is constant and equal to 4m/s. It the speed of the turbine is 200 rpm, head on the turbine is 10m and discharge at outlet is radial determine.

(i) The runner vane angle at inlet and outlet.

(ii) Workdown by the work/sec per unit weight of water striking per second 

(iii) Hydraulic efficiency.

Given data:

Internal diameter D1 = 0.6 m

External diameter D2 = 1.2 m

Guide blade angle α = 15°

Velocity of flow Vf1 = Vƒ2 = 4 m/s

Speed (N) = 200 rpm

Head (H) = 10m

Discharge at outlet = Radial Vw2 = 0 V2 = Vƒ2, B = 90°

To find:

1. Runner vane angle θ and ϕ 

2. Workdone/sec per unit weight of water

3. Hydraulic efficiency (ηh)

Solution:

Result:

1. Runner vane angle θ = 24.83°, ϕ = 17.65°

2. Work one/seper unit weight of water / sec = 9.240 Nm/N

3. Hydraulic efficiency = 95,65%

Example - 32

The internal and external diameter at an outward flow reaction turbine are 2m and 2.75m respectively. The turbine is running at 250 rpm and rate of flow at water through the turbine is 5 m3/s. The width of the runner is constant at inlet and outlet and is equal to 250 mm. The head on the turbine is 150m Neglecting thickness of the vanes and taking discharge radial at outlet determine. 

(i) Vane angles at inlet and outlet 

(ii) Velocity of flow at inlet and outlet 

Given data:

Internal diameter D1 = 2.0m

Speed (N) = 250 rpm

External diameter D2 = 2.75m 

Discharge Q = 5 m3/s

Width B1 - B2 = 250mm = 0.25m

Head (H) = 150m

Discharge = Radial Vw2 = 0, Vƒ2 = V2, β = 90°

To find:

1. Vane angles at inlet and outlet

2. Velocity of flow at inlet and outlet

Solution:

6. From velocity triangles [same as inward flow turbines]

Result:

1. Vane angle θ = 6.072°

ϕ = 3.68°

2. Flow velocity at inlet (Vf1) = 3.183 m/s

outlet (Vƒ2) = 2.315 m/s