Benha UniversitySubject: Turbo- Machine
Faculty of Engineering- ShoubraYear : fourth Mech. Power
Mech. Power Department2007/2008
Sheet No (1)
1-A radial flow turbine required to produce 30 MW under a head of 14 m at a speed of 95 rpm. A geometrically similar model with an output of 40 kW and a head of 5 m is to be tested under dynamically similar conditions. At what speed must the model be run, what is the required impeller diameter ratio between the model and prototype and what is the volume flow rate through the model if its efficiency can be assumed to be 90 percent. Assume that the density change can be neglected.
2-The performance curves of a centrifugal pump are shown in Fig. 1. The impeller diameter is 127 mm and the pump delivers 3.83 lit/sec at a speed of 2000 rpm. If a 102 mm diameter impeller is fitted and the pump runs at speed of 2200 rpm, what is the volume flow rate? Determine also the new pump head.
3-An axial flow compressor is designed to run at 4500 rpm when ambient atmospheric conditions are 101.3 kPa and 15 oC. On the day when the performance characteristic is obtained, the atmospheric temperature is 25 oC. What is the correct speed at which the compressor must run? If an entry pressure of 60 kPa is obtained at the point where the normal ambient condition mass flow would be 65 kg/sec, calculate the mass flow obtained in the test.
4-Specifications for axial flow coolant pump for one loop of a pressurized water nuclear reactor are:
Head 85 m
Flow rate 20 000 m3/sec
Speed 1490 rpm
Diameter 12200 mm
Water density 714 kg/m3
Power 4 MW (electrical)
The manufacturer plans to build a model. Test conditions limit the available electric power to 500 kW and flow to 0.5 m3/sec of cold water. If the model and prototype efficiencies are assumed equal, find the head, speed and scale ratio of the model. Calculate the dimensionless specific speed of the prototype and confirm that it is identical with the model.
5-A pump with an available driven speed of 800 rpm is required to overcome a 1.83 m head while pumping 0.3 m3/sec. What type of pump is required and what power is required?
6-A reservoir has a head of 40 m and a channel leading from the reservoir permits a flow of 34 m3/sec. If the rotational speed of the rotor is 150 rpm, what is the most suitable type of turbine use?
7-A large centrifugal pump contains liquid whose kinematic viscosity may vary between 3 and 6 times that of water. The dimensionless specific speed of the pump is 0.183 rev and it is to discharge 2 m3/sec of liquid against a total head of 15 m. Determine the range of speeds and test heads for a one-quarter scale model investigation of the full size model uses water.
8-In a projected low-head hydroelectric scheme, 10 1000 ft3/sec of water are available under a head of 12 ft. Alternative schemes to use Francis turbines having a specific speed of 105 rpm or Kaplan turbines with specific speed of 180 rpm are investigated. The normal running speed is to be 50 rpm in both schemes. Determine the dimensionless specific speeds and compare the two proposals insofar as the number of machines are concerned, and estimate the power and the efficiency of each type may be assume to be 0.9.
9-A customer approaches with a particular pump required and is quoted for an axial flow pump of rotor diameter 152.4 mm. Running at a speed of 980 rpm, the machine is said to deliver 0.283 m3/sec of water against a head of 9.1 m at an efficiency of 85%. Are claims of the salesman realistic?
10- A Francis turbine runs at 180 rpm under a head of 146 m with an efficiency of 93.5 %. Estimate the power output of the installation.