Fluid Engines and Turbines

A pump or compressor does work on a fluid in order to increase the fluid s pressure, elevation, velocity, or internal energy. A fluid engine or turbine extracts work from a fluid by lowering its pressure, elevation, velocity, or internal energy. These definitions are the reverse of each other, so some devices could serve as pumps or as fluid engines, depending on what way they were run. Tidal power plants and pumped storage power plants use the same device as a pump for part of the day and as a turbine for another part of the day. 

The PD pump shown in Fig. 9.1 can be used as a fluid engine with simple changes in valve timing. This is the form of the steam engine which supplied most of the world s mechanical power in the nineteenth and early twentieth centuries its operation is the reverse of that of the compressor, shown diagrammatically in Fig. 9.9. This type of engine has been replaced for very large applications with turbines (cheaper and simpler) and in industry with 

For large installations extracting power from fluids (generally water in hydroelectric plants and steam in thermal power plants), the most common device is a turbine. Water and steam turbines have the same principles of operation but vei different sizes, shapes, and speeds. 

Another kinid of turbine is the reaction turbine, in which the fluid enters 

This is called a reaction turbine for the same reason that a rocket motor is often called a reaction motor the force exerted is described by Newton s third law, action equals reaction. A turbine of this type could be constructed by attaching two rockets to the ends of a shaft in place of the water jets shown in Fig. 9.13. In a reaction turbine, the pressure reduction takes place in a moving nozzle. 

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Fluid engine and turbine efficiency is defined as the inverse of pump or compressor efficiency ... 

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