MENG 411-Fluidmachinery

Fall 2012

Problem Session and Assignment # 1

2. Consider the parameters with the following functional relation:

),,,,,,,,( QgHNbdDfP µρε=

for evaluation the performance of turbomachine where;

P: power, ρ : fluid density, d/D: inner/outer diameter, µ : fluid viscosity,

N: rotational speed, gH: specific energy variable, Q: volume flow rate.

Investigate the dimensionless performance of the above turbomachine’s relation.

Homework assignment

4. A large wind turbine, designed to operate at 50 km/h, is to be tested in a laboratory by

constructing a 1:15 scale model. What air speed should be used in the wind tunnel, what

angular velocity should be used to simulate a prototype speed of 5 rpm, and what power

output is expected from the model if the prototype output is designed to be 50 kW?.

5. A quarter scale hydraulic turbine model is tested to work under a head of 11 m. The full

scale turbine is required to work under a head of 30 m and to run at 430 rpm. At what

speed must the model run?. If the model develops 100 kW and uses 1.05 m3/s of water,

what power and rate of flow will be obtained from the full scale turbine assuming that its

efficiency is 3% better than that of the model.

6. A centrifugal compressor when running at 3000 rpm develops a pressure of 1.05 bar and

a mass flow rate of 0.3 kg/s. If the inlet area of the compressor is 0.01 m2, find the mass

flow rate when the compressor runs at 18000 rpm. Estimate also the inlet Mach number,

and the developed pressure.

(hint: Atmospheric conditions are 1.01325 bar and 300 K).

Homework assignment

7. A test is to be performed on a proposed design for a large pump that is deliver 1.5 m3/s of

water from a 40-cm diameter impeller with a pressure rise of 400 kPa. A model with an

8-cm diameter impeller is to be used. What flow rate should be used and what pressure

rise is to be expected?. The model fluid is water at the same temperature as the water in

the prototype.

Solution: