Curtis turbine

Figure 9-6 shows a diagram of a single-stage impulse turbine. The statie pressure deereases in the nozzle with a eorresponding inerease in the absolute veloeity. The absolute veloeity is then redueed in the rotor, but the statie pressure and the relative veloeity remain eonstant. To get the maximum energy transfer, the blades must rotate at about one-half the veloeity of the gas jet veloeity. Two or more rows of moving blades are sometimes used in eonjunetion with one nozzle to obtain wheels with low blade tip speeds and stresses. In-between the moving rows of blades are guide vanes that redireet the gas from one row of moving blades to another as shown in Figure 9-7. This type of turbine is sometimes ealled a Curtis turbine.

The Curtis and the Parsons turbine designs are based on different fundamental principles of fluid flow. The Curtis turbine has an impulse design, where the steam expands through nozzles so that it reaches a... 

Figure 9-7. Pressure and veioeity distributions in a Curtis-type impuise turbine.

A Volt Curtis steam turbine, by GE from the designs of Charles G. Curtis, was installed for the Tv /in City Rapid Transit Company in Minneapolis and photographed in around 19QQ. (Corbis-Eetlmannj... 

Somerscales, E. F. C. (1992). The Vertical Curtis Steam Turbine. Mewconien Society of Engineering Technology Transactions 63 1-52. 

A combination of methods (1) and (2) may be used, as in the Curtis machine which may have, say, five pressure stages with two moving wheels in each pressure stage. This leads to peripheral speeds as low as those of pressure turbines, along with high efficiency. 

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