MAE 3183, Measurements II Laboratory
Turbines are machines which develop torque and shaft power as a result of a momentum change in the
fluid which flows through them. The fluid may be a gas, vapor, or liquid. For the fluid to achieve the high
velocity required to provide worthwhile momentum changes, there must be significant pressure differences
between the inlet and exhaust of the turbine. Sources of pressurized gas include previously compressed
(and possibly heated) gas - as in a gas turbine, or in the turbine of a turbo-charger for an I.C. engine. In
power generating plants, fossil or nuclear fuel is used to boil large amounts of water into steam vapor at
high pressures. A turbine converts the energy of the steam into work that drives electric generators. This
process provides the electricity that we use in homes and businesses.
There are numerous types of turbines. These vary from the elementary example used in a dentist drill to
the large, multi-stage turbines used in the generating stations, developing as much as 1000 MW. The
turbine used for the experiment, the Hilton Experimental Turbine F800, is classified as a “
stage, axial flow, impulse turbine
” indicates an elementary turbine without complications such as
velocity compounding. "
” means the expansion of the fluid from the turbine inlet pressure to
the exhaust pressure takes place within one stator and its corresponding rotor. “
” indicates that
the fluid enters and leaves the rotor at the same radius and without significant radial components in the
velocity. Finally, “
” means that the fluid pressure drop (and consequent increase of velocity) takes
place in the stator - i.e. in the nozzles. The fluid therefore passes through the rotor at an almost constant
pressure, having only the velocity changed. It is useful to consider the turbine as a work producing
machine undergoing a steady flow process, and to analyze its efficiency relative to a machine without
irreversibilities or heat transfers.
Application of the first law of thermodynamics
, First Law applied to a turbine
Figure 1 shows a turbine through which unit mass of fluid flows under steady flow conditions. The
pressures, specific enthalpies and velocities at inlet and exhaust are p
While unit mass of fluid flows, a specific work transfer, w, and a specific heat transfer, q, take place.
Applying the first law in the form of the steady flow equation: