Is there any trip on dryness fraction in steam turbine? If so, what is the recommended value of dryness fraction that must be maintained at LP exhaust to condenser? Also Why should we maintain the dryness fraction with in the limits?
Except for the last few stages of ST blades (probably the last two rows), in general ST blades are not designed to rotate with the present of water droplets. The droplets will damage the blades pretty soon. For the given design back pressure of LP turbines, the last row or maybe the second last row of blades is designed to deal typical up to 10% wetness. Anything more than that the wetness might reach the unprotected blades.
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