2.4.4   Leaving loss


Steam leaves the final stage of an LP turbine with kinetic energy at the total pressure and enthalpy shown in Fig 1.19. If the steam could be slowed down isentropically to zero kinetic energy, it would be at static pressure and enthalpy.

In practice the steam does slow down after leaving the last blade, but through the conversion of its kinetic energy to flou friction losses. This is a constant enthalpy process since the steam cannot do work on blades that it has already left. Consequently the steam comes tc rest at the point X on Fig 1.19.

LP cylinder efficiency

The heat loss between the total conditions at blade exit (H2) and the static pressure line (H4) is known at the leaving loss. The significance leaving loss has or efficiency can be seen in the following example:


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