Determining compressor and infinitesimal stage efficiencies

Question

1)(a) Explain the flow pattern from leading to trailing edge of a cambered aerofoil blade in a turbo Machine.

(b) Describe the Reheat and Preheat phenomena in Turbines and Compressors.            

2)(a) Low Pressure air Compressor develops the pressure of 1500 kgf/m². If initial and final states of air P₁ = 1.02 bar, T₁ =  300K and T₂ =  315 K. Find out the compressor and infinitesimal stage efficiencies.

(b) Write down the losses in turbo Machines.

3) A centrifugal fan has the data given below:

Inner Diameter of the impeller = 18 cm
Outer diameter of the impeller = 20 cm
Speed = 1450 rpm

Relative and absolute velocities respectively are:

At Entry = 20 m/s, 21 m/s
At exit = 17 m/s, 25 m/s
Flow rate = 0.5 kg/s
Motor efficiency = 78%

Find out:

(a) the stage pressure rise
(b) Degree of reaction
(c) The power required to drive the fan

Take density of air 1.25 kg/m³.

4) The axial fan stage consisting of only the rotor has the following data:

Rotor blade air angle at exit = 10^o
Tip Diameter = 60cm
Hub Diameter = 30 cm
Rotational Speed = 960 rpm 
Power required = 1 KW
Flow co-efficient = 0.245
Inlet flow conditions (P₁) = 1.02 bar
Inlet flow conditions (T₁) = 316 K

Find out:

(a) the rotor blade angle at entry

(b) Stage pressure rise

(c) Overall efficiency

5) Stage of a turbine with Parsons blading delivers dry saturated steam at 2.7 bar from fixed blades at 90 m/s. Mean blade height is 40 mm, and moving blade exit angle is 20^o. Axial velocity of steam is ¾ of the blade velocity at mean radius. Steam is supplied to the stage at the rate of 9000 kg/hr. The effect of blade tip thickness on the annulus area can be neglected, compute

(a) the wheel speed in rpm

(b) the diagram power

(c) the diagram efficiency